WorldWideScience

Sample records for gravity wave flow

  1. Sediment gravity flows triggered by remotely generated earthquake waves

    Science.gov (United States)

    Johnson, H. Paul; Gomberg, Joan S.; Hautala, Susan L.; Salmi, Marie S.

    2017-06-01

    Recent great earthquakes and tsunamis around the world have heightened awareness of the inevitability of similar events occurring within the Cascadia Subduction Zone of the Pacific Northwest. We analyzed seafloor temperature, pressure, and seismic signals, and video stills of sediment-enveloped instruments recorded during the 2011-2015 Cascadia Initiative experiment, and seafloor morphology. Our results led us to suggest that thick accretionary prism sediments amplified and extended seismic wave durations from the 11 April 2012 Mw8.6 Indian Ocean earthquake, located more than 13,500 km away. These waves triggered a sequence of small slope failures on the Cascadia margin that led to sediment gravity flows culminating in turbidity currents. Previous studies have related the triggering of sediment-laden gravity flows and turbidite deposition to local earthquakes, but this is the first study in which the originating seismic event is extremely distant (> 10,000 km). The possibility of remotely triggered slope failures that generate sediment-laden gravity flows should be considered in inferences of recurrence intervals of past great Cascadia earthquakes from turbidite sequences. Future similar studies may provide new understanding of submarine slope failures and turbidity currents and the hazards they pose to seafloor infrastructure and tsunami generation in regions both with and without local earthquakes.

  2. Gravity wave astronomy

    International Nuclear Information System (INIS)

    Pinheiro, R.

    1979-01-01

    The properties and production of gravitational radiation are described. The prospects for their detection are considered including the Weber apparatus and gravity-wave telescopes. Possibilities of gravity-wave astronomy are noted

  3. GEODYNAMIC WAVES AND GRAVITY

    Directory of Open Access Journals (Sweden)

    A. V. Vikulin

    2014-01-01

    Full Text Available  Gravity phenomena related to the Earth movements in the Solar System and through the Galaxy are reviewed. Such movements are manifested by geological processes on the Earth and correlate with geophysical fields of the Earth. It is concluded that geodynamic processes and the gravity phenomena (including those of cosmic nature are related.  The state of the geomedium composed of blocks is determined by stresses with force moment and by slow rotational waves that are considered as a new type of movements [Vikulin, 2008, 2010]. It is shown that the geomedium has typical rheid properties [Carey, 1954], specifically an ability to flow while being in the solid state [Leonov, 2008]. Within the framework of the rotational model with a symmetric stress tensor, which is developed by the authors [Vikulin, Ivanchin, 1998; Vikulin et al., 2012a, 2013], such movement of the geomedium may explain the energy-saturated state of the geomedium and a possibility of its movements in the form of vortex geological structures [Lee, 1928]. The article discusses the gravity wave detection method based on the concept of interactions between gravity waves and crustal blocks [Braginsky et al., 1985]. It is concluded that gravity waves can be recorded by the proposed technique that detects slow rotational waves. It is shown that geo-gravitational movements can be described by both the concept of potential with account of gravitational energy of bodies [Kondratyev, 2003] and the nonlinear physical acoustics [Gurbatov et al., 2008]. Based on the combined description of geophysical and gravitational wave movements, the authors suggest a hypothesis about the nature of spin, i.e. own moment as a demonstration of the space-time ‘vortex’ properties.  

  4. Spontaneous generation and reversals of mean flows in a convectively-generated internal gravity wave field

    Science.gov (United States)

    Couston, Louis-Alexandre; Lecoanet, Daniel; Favier, Benjamin; Le Bars, Michael

    2017-11-01

    We investigate via direct numerical simulations the spontaneous generation and reversals of mean zonal flows in a stably-stratified fluid layer lying above a turbulent convective fluid. Contrary to the leading idealized theories of mean flow generation by self-interacting internal waves, the emergence of a mean flow in a convectively-generated internal gravity wave field is not always possible because nonlinear interactions of waves of different frequencies can disrupt the mean flow generation mechanism. Strong mean flows thus emerge when the divergence of the Reynolds stress resulting from the nonlinear interactions of internal waves produces a strong enough anti-diffusive acceleration for the mean flow, which, as we will demonstrate, is the case when the Prandtl number is sufficiently low, or when the energy input into the internal wavefield by the convection and density stratification are sufficiently large. Implications for mean zonal flow production as observed in the equatorial stratospheres of the Earth, Saturn and Jupiter, and possibly occurring in other geophysical systems such as planetary and stellar interiors will be briefly discussed. Funding provided by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program through Grant Agreement No. 681835-FLUDYCO-ERC-2015-CoG.

  5. Surfing surface gravity waves

    Science.gov (United States)

    Pizzo, Nick

    2017-11-01

    A simple criterion for water particles to surf an underlying surface gravity wave is presented. It is found that particles travelling near the phase speed of the wave, in a geometrically confined region on the forward face of the crest, increase in speed. The criterion is derived using the equation of John (Commun. Pure Appl. Maths, vol. 6, 1953, pp. 497-503) for the motion of a zero-stress free surface under the action of gravity. As an example, a breaking water wave is theoretically and numerically examined. Implications for upper-ocean processes, for both shallow- and deep-water waves, are discussed.

  6. Computation of 3D steady Navier-Stokes flow with free-surface gravity waves

    NARCIS (Netherlands)

    Lewis, M.R.; Koren, B.; Raven, H.C.; Armfield, S.; Morgan, P.; Srinivas, K,

    2003-01-01

    In this paper an iterative method for the computation of stationary gravity-wave solutions is investigated, using a novel formulation of the free-surface (FS) boundary-value problem. This method requires the solution of a sequence of stationary Reynolds-Averaged Navier-Stokes subproblems employing

  7. Computation of 3D steady Navier-Stokes flow with free-surface gravity waves

    NARCIS (Netherlands)

    M.R. Lewis; B. Koren (Barry); H.C. Raven

    2003-01-01

    textabstractIn this paper an iterative method for the computation of stationary gravity-wave solutions is investigated, using a novel formulation of the free-surface (FS) boundary-value problem. This method requires the solution of a sequence of stationary Reynolds-Averaged Navier-Stokes subproblems

  8. A fast wind-farm boundary-layer model to investigate gravity wave effects and upstream flow deceleration

    Science.gov (United States)

    Allaerts, Dries; Meyers, Johan

    2017-11-01

    Wind farm design and control often relies on fast analytical wake models to predict turbine wake interactions and associated power losses. Essential input to these models are the inflow velocity and turbulent intensity at hub height, which come from prior measurement campaigns or wind-atlas data. Recent LES studies showed that in some situations large wind farms excite atmospheric gravity waves, which in turn affect the upstream wind conditions. In the current study, we develop a fast boundary-layer model that computes the excitation of gravity waves and the perturbation of the boundary-layer flow in response to an applied force. The core of the model is constituted by height-averaged, linearised Navier-Stokes equations for the inner and outer layer, and the effect of atmospheric gravity waves (excited by the boundary-layer displacement) is included via the pressure gradient. Coupling with analytical wake models allows us to study wind-farm wakes and upstream flow deceleration in various atmospheric conditions. Comparison with wind-farm LES results shows excellent agreement in terms of pressure and boundary-layer displacement levels. The authors acknowledge support from the European Research Council (FP7-Ideas, Grant No. 306471).

  9. Scattering of internal gravity waves

    OpenAIRE

    Leaman Nye, Abigail

    2011-01-01

    Internal gravity waves play a fundamental role in the dynamics of stably stratified regions of the atmosphere and ocean. In addition to the radiation of momentum and energy remote from generation sites, internal waves drive vertical transport of heat and mass through the ocean by wave breaking and the mixing subsequently produced. Identifying regions where internal gravity waves contribute to ocean mixing and quantifying this mixing are therefore important for accurate climate ...

  10. Role of Wind Filtering and Unbalanced Flow Generation in Middle Atmosphere Gravity Wave Activity at Chatanika Alaska

    Directory of Open Access Journals (Sweden)

    Colin C. Triplett

    2017-01-01

    Full Text Available The meteorological control of gravity wave activity through filtering by winds and generation by spontaneous adjustment of unbalanced flows is investigated. This investigation is based on a new analysis of Rayleigh LiDAR measurements of gravity wave activity in the upper stratosphere-lower mesosphere (USLM,40–50kmon 152 nights at Poker Flat Research Range (PFRR, Chatanika, Alaska (65◦ N, 147◦ W, over 13 years between 1998 and 2014. The LiDAR measurements resolve inertia-gravity waves with observed periods between 1 h and 4 h and vertical wavelengths between 2 km and 10 km. The meteorological conditions are defined by reanalysis data from the Modern-Era Retrospective Analysis for Research and Applications (MERRA. The gravity wave activity shows large night-to-night variability, but a clear annual cycle with a maximum in winter,and systematic interannual variability associated with stratospheric sudden warming events. The USLM gravity wave activity is correlated with the MERRA winds and is controlled by the winds in the lower stratosphere through filtering by critical layer filtering. The USLM gravity wave activity is also correlated with MERRA unbalanced flow as characterized by the residual of the nonlinear balance equation. This correlation with unbalanced flow only appears when the wind conditions are taken into account, indicating that wind filtering is the primary control of the gravity wave activity.

  11. The physics of orographic gravity wave drag

    Directory of Open Access Journals (Sweden)

    Miguel A C Teixeira

    2014-07-01

    Full Text Available The drag and momentum fluxes produced by gravity waves generated in flow over orography are reviewed, focusing on adiabatic conditions without phase transitions or radiation effects, and steady mean incoming flow. The orographic gravity wave drag is first introduced in its simplest possible form, for inviscid, linearized, non-rotating flow with the Boussinesq and hydrostatic approximations, and constant wind and static stability. Subsequently, the contributions made by previous authors (primarily using theory and numerical simulations to elucidate how the drag is affected by additional physical processes are surveyed. These include the effect of orography anisotropy, vertical wind shear, total and partial critical levels, vertical wave reflection and resonance, non-hydrostatic effects and trapped lee waves, rotation and nonlinearity. Frictional and boundary layer effects are also briefly mentioned. A better understanding of all of these aspects is important for guiding the improvement of drag parametrization schemes.

  12. Measurements of gravity and gravity-capillary waves in horizontal gas-liquid pipe flow using PIV in both phases

    NARCIS (Netherlands)

    Birvalski, M.; Tummers, M.J.; Henkes, R.A.W.M.

    2016-01-01

    An experimental study was performed in stratified wavy flow of air and water through a horizontal pipe. The velocity fields in both phases were measured simultaneously using PIV and the interfacial shape was resolved using a profile capturing technique. The objective of the study was to

  13. Observations and modeling of wave-supported sediment gravity flows on the Po prodelta and comparison to prior observations from the Eel shelf

    Science.gov (United States)

    Traykovski, P.; Wiberg, P. L.; Geyer, W. R.

    2007-02-01

    A mooring and tripod array was deployed from the fall of 2002 through the spring of 2003 on the Po prodelta to measure sediment transport processes associated with sediment delivered from the Po River. Observations on the prodelta revealed wave-supported gravity flows of high concentration mud suspensions that are dynamically and kinematically similar to those observed on the Eel shelf [Traykovski, P., Geyer, W.R., Irish, J.D., Lynch, J.F., 2000. The role of wave-induced density-driven fluid mud flows for cross-shelf transport on the Eel River continental shelf. Continental Shelf Research 20, 2113-2140]. Due to the dynamic similarity between the two sites, a simple one-dimensional (1D) across-shelf model with the appropriate bottom boundary condition was used to examine fluxes associated with this transport mechanism at both locations. To calculate the sediment concentrations associated with the wave-dominated and wave-current resuspension, a bottom boundary condition using a reference concentration was combined with an "active layer" formulation to limit the amount of sediment in suspension. Whereas the wave-supported gravity flow mechanism dominated the transport on the Eel shelf, on the Po prodelta flux due to this mechanism is equal in magnitude to transport due to wave resuspension and wind-forced mean currents in the cross-shore direction. Southward transport due to wave resuspension and wind forced mean currents move an order of magnitude more sediment along-shore than the down-slope flux associated wave-supported gravity flows.

  14. Formation and mechanics of granular waves in gravity and shallow overland flow

    Science.gov (United States)

    Sediment transport in overland flow is a highly complex process involving many properties relative to the flow regime characteristics, soil surface conditions, and type of sediment. From a practical standpoint, most sediment transport studies are concerned with developing relationships of rates of s...

  15. The wave of the future - Searching for gravity waves

    International Nuclear Information System (INIS)

    Goldsmith, D.

    1991-01-01

    Research on gravity waves conducted by such scientists as Gamov, Wheeler, Weber and Zel'dovich is discussed. Particular attention is given to current trends in the theoretical analysis of gravity waves carried out by theorists Kip Thorne and Leonid Grishchuk. The problems discussed include the search for gravity waves; calculation of the types of gravity waves; the possibility of detecting gravity waves from localized sources, e.g., from the collision of two black holes in a distant galaxy or the collapse of a star, through the Laser Interferometer Gravitational Wave Observatory; and detection primordial gravity waves from the big bang

  16. Laser Source for Atomic Gravity Wave Detector

    Data.gov (United States)

    National Aeronautics and Space Administration — The Atom Interferometry (AI) Technology for Gravity Wave Measurements demonstrates new matter wave Interferometric sensor technology for precise detection and...

  17. New Gravity Wave Treatments for GISS Climate Models

    Science.gov (United States)

    Geller, Marvin A.; Zhou, Tiehan; Ruedy, Reto; Aleinov, Igor; Nazarenko, Larissa; Tausnev, Nikolai L.; Sun, Shan; Kelley, Maxwell; Cheng, Ye

    2011-01-01

    Previous versions of GISS climate models have either used formulations of Rayleigh drag to represent unresolved gravity wave interactions with the model-resolved flow or have included a rather complicated treatment of unresolved gravity waves that, while being climate interactive, involved the specification of a relatively large number of parameters that were not well constrained by observations and also was computationally very expensive. Here, the authors introduce a relatively simple and computationally efficient specification of unresolved orographic and nonorographic gravity waves and their interaction with the resolved flow. Comparisons of the GISS model winds and temperatures with no gravity wave parameterization; with only orographic gravity wave parameterization; and with both orographic and nonorographic gravity wave parameterizations are shown to illustrate how the zonal mean winds and temperatures converge toward observations. The authors also show that the specifications of orographic and nonorographic gravity waves must be different in the Northern and Southern Hemispheres. Then results are presented where the nonorographic gravity wave sources are specified to represent sources from convection in the intertropical convergence zone and spontaneous emission from jet imbalances. Finally, a strategy to include these effects in a climate-dependent manner is suggested.

  18. Gravity induced wave function collapse

    Science.gov (United States)

    Gasbarri, G.; Toroš, M.; Donadi, S.; Bassi, A.

    2017-11-01

    Starting from an idea of S. L. Adler [in Quantum Nonlocality and Reality: 50 Years of Bell's Theorem, edited by M. Bell and S. Gao (Cambridge University Press, Cambridge, England 2016)], we develop a novel model of gravity induced spontaneous wave function collapse. The collapse is driven by complex stochastic fluctuations of the spacetime metric. After deriving the fundamental equations, we prove the collapse and amplification mechanism, the two most important features of a consistent collapse model. Under reasonable simplifying assumptions, we constrain the strength ξ of the complex metric fluctuations with available experimental data. We show that ξ ≥10-26 in order for the model to guarantee classicality of macro-objects, and at the same time ξ ≤10-20 in order not to contradict experimental evidence. As a comparison, in the recent discovery of gravitational waves in the frequency range 35 to 250 Hz, the (real) metric fluctuations reach a peak of ξ ˜10-21.

  19. The sources of atmospheric gravity waves

    International Nuclear Information System (INIS)

    Nagpal, O.P.

    1979-01-01

    The gravity wave theory has been very successful in the interpretation of various upper atmospheric phenomena. This article offers a review of the present state of knowledge about the various sources of atmospheric gravity waves, particularly those which give rise to different types of travelling ionospheric disturbance. Some specific case studies are discussed. (author)

  20. An introduction to atmospheric gravity waves

    CERN Document Server

    Nappo, Carmen J

    2012-01-01

    Gravity waves exist in all types of geophysical fluids, such as lakes, oceans, and atmospheres. They play an important role in redistributing energy at disturbances, such as mountains or seamounts and they are routinely studied in meteorology and oceanography, particularly simulation models, atmospheric weather models, turbulence, air pollution, and climate research. An Introduction to Atmospheric Gravity Waves provides readers with a working background of the fundamental physics and mathematics of gravity waves, and introduces a wide variety of applications and numerous recent advances. Nappo provides a concise volume on gravity waves with a lucid discussion of current observational techniques and instrumentation.An accompanying website contains real data, computer codes for data analysis, and linear gravity wave models to further enhance the reader's understanding of the book's material. Companion web site features animations and streaming video Foreword by George Chimonas, a renowned expert on the interac...

  1. Non Newtonian gravity creeping flow

    International Nuclear Information System (INIS)

    Gratton, J.; Mahajan, S.M.; Minotti, F.

    1988-11-01

    We derive the governing equations for creeping gravity currents of non Newtonian liquids having a power law rheology, using a lubrication approximation. We consider unidirectional and axisymmetric currents. The equations differ from those for Newtonian liquids, being nonlinear in the spatial derivative of the thickness of the current. However, many solutions are closely analogous to those for Newtonian rheology; in particular the spreading relations can also be expressed as power laws of time, with exponents that depend on the rheological index. Similarity solutions for currents whose volume varies as a power of time are obtained. For the spread of a constant volume of liquid, analytic solutions are found. We also derive solutions of the waiting-time type, as well as the ones describing steady flows from a constant source to a sink. General travelling wave solutions are given, and analytic formulae for a simple case are derived. A phase plane formalism, that allows the systematic derivation of self similar solutions, is introduced. The application of the Boltzmann transform is briefly discussed. Present results are closely analogous to those for Newtonian liquids; all the solutions obtained here have their counterparts in Newtonian flows. This happens because the power law rheology, like the Newtonian constitutive relation, involves a single dimensional parameter. Thus one finds similarity solutions whenever the analogous Newtonian problem is self similar. Although the spreading relations are rheology-dependent, in most cases the dependence is rather weak. The present results may be of interest for geophysics since the lithosphere deforms according to an average power law rheology. (author). 17 refs

  2. Upper atmospheric planetary-wave and gravity-wave observations

    Science.gov (United States)

    Justus, C. G.; Woodrum, A.

    1973-01-01

    Previously collected data on atmospheric pressure, density, temperature and winds between 25 and 200 km from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others were analyzed by a daily-difference method, and results on the magnitude of atmospheric perturbations interpreted as gravity waves and planetary waves are presented. Traveling planetary-wave contributions in the 25-85 km range were found to have significant height and latitudinal variation. It was found that observed gravity-wave density perturbations and wind are related to one another in the manner predicted by gravity-wave theory. It was determined that, on the average, gravity-wave energy deposition or reflection occurs at all altitudes except the 55-75 km region of the mesosphere.

  3. Tidal and gravity waves study from the airglow measurements at ...

    Indian Academy of Sciences (India)

    The other waves may be the upward propagating gravity waves or waves resulting from the interaction of inter-mode tidal oscillations, interaction of tidal waves with planetary waves and gravity waves. Some times, the second harmonic wave has higher vertical velocity than the corresponding fundamental wave. Application ...

  4. The nonlinear effects on the characteristics of gravity wave packets: dispersion and polarization relations

    Directory of Open Access Journals (Sweden)

    S.-D. Zhang

    2000-10-01

    Full Text Available By analyzing the results of the numerical simulations of nonlinear propagation of three Gaussian gravity-wave packets in isothermal atmosphere individually, the nonlinear effects on the characteristics of gravity waves are studied quantitatively. The analyses show that during the nonlinear propagation of gravity wave packets the mean flows are accelerated and the vertical wavelengths show clear reduction due to nonlinearity. On the other hand, though nonlinear effects exist, the time variations of the frequencies of gravity wave packets are close to those derived from the dispersion relation and the amplitude and phase relations of wave-associated disturbance components are consistent with the predictions of the polarization relation of gravity waves. This indicates that the dispersion and polarization relations based on the linear gravity wave theory can be applied extensively in the nonlinear region.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides

  5. A Multiscale Nested Modeling Framework to Simulate the Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves

    Science.gov (United States)

    2015-09-30

    Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves Lian Shen St. Anthony Falls Laboratory and Department of Mechanical...on studying surface gravity wave evolution and spectrum in the presence of surface currents caused by strongly nonlinear internal solitary waves...interaction of surface and internal gravity waves in the South China Sea. We will seek answers to the following questions: 1) How does the wind-wave

  6. Relic gravity waves from braneworld inflation

    International Nuclear Information System (INIS)

    Sahni, Varun; Sami, M.; Souradeep, Tarun

    2002-01-01

    We discuss a scenario in which extra dimensional effects allow a scalar field with a steep potential to play the dual role of the inflaton as well as dark energy (quintessence). The post-inflationary evolution of the universe in this scenario is generically characterized by a 'kinetic regime' during which the kinetic energy of the scalar field greatly exceeds its potential energy resulting in a 'stiff' equation of state for scalar field matter P φ ≅ρ φ . The kinetic regime precedes the radiation dominated epoch and introduces an important new feature into the spectrum of relic gravity waves created quantum mechanically during inflation. The amplitude of the gravity wave spectrum increases with the wave number for wavelengths shorter than the comoving horizon scale at the commencement of the radiative regime. This 'blue tilt' is a generic feature of models with steep potentials and imposes strong constraints on a class of inflationary braneworld models. Prospects for detection of the gravity wave background by terrestrial and space-borne gravity wave observatories such as LIGO II and LISA are discussed

  7. Numerical simulations of convectively excited gravity waves

    International Nuclear Information System (INIS)

    Glatzmaier, G.A.

    1983-01-01

    Magneto-convection and gravity waves are numerically simulated with a nonlinear, three-dimensional, time-dependent model of a stratified, rotating, spherical fluid shell heated from below. A Solar-like reference state is specified while global velocity, magnetic field, and thermodynamic perturbations are computed from the anelastic magnetohydrodynamic equations. Convective overshooting from the upper (superadiabatic) part of the shell excites gravity waves in the lower (subadiabatic) part. Due to differential rotation and Coriolis forces, convective cell patterns propagate eastward with a latitudinally dependent phase velocity. The structure of the excited wave motions in the stable region is more time-dependent than that of the convective motions above. The magnetic field tends to be concentrated over giant-cell downdrafts in the convective zone but is affected very little by the wave motion in the stable region

  8. Laser Source for Atomic Gravity Wave Detector Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Atom Interferometry (AI) Technology for Gravity Wave Measurements demonstrates new matter wave Interferometric sensor technology for precise detection and...

  9. A Plant's Response to Gravity as a Wave Guide Phenomenon

    Science.gov (United States)

    Wagner, Orvin

    1997-11-01

    Plant experimental data provides a unifying wave theory (W-wave theory) for the growth and development of plants. A plant's response to gravity is an important aspect of this theory. It appears that a plant part is tuned to the angle with which it initially grew with respect to the gravitational field and changes produce correction responses. This is true because the velocity of W-waves (whose standing waves determine plant structure) within plant tissue is found to be different in different directions (angle a) with respect to the gravitational field. I found that there are preferred values of a, namely integral multiples of near 5 degrees for some plants. Conifers apparently are more sensitive to the gravitational field than deciduous trees, in the cases studied, so their structure is determined in more detail by the gravitational field. A plant's response to gravity appears to be a fundamental phenomenon and may provide a new model for gravity that can be experimentally verified in the laboratory. Along these same lines accelerometers placed in plant tissue indicate that plants produce gravity related forces that facilitate sap flow. See the

  10. Gravity's kiss the detection of gravitational waves

    CERN Document Server

    Collins, Harry

    2017-01-01

    Scientists have been trying to confirm the existence of gravitational waves for fifty years. Then, in September 2015, came a "very interesting event" (as the cautious subject line in a physicist's email read) that proved to be the first detection of gravitational waves. In Gravity's Kiss, Harry Collins -- who has been watching the science of gravitational wave detection for forty-three of those fifty years and has written three previous books about it -- offers a final, fascinating account, written in real time, of the unfolding of one of the most remarkable scientific discoveries ever made. Predicted by Einstein in his theory of general relativity, gravitational waves carry energy from the collision or explosion of stars. Dying binary stars, for example, rotate faster and faster around each other until they merge, emitting a burst of gravitational waves. It is only with the development of extraordinarily sensitive, highly sophisticated detectors that physicists can now confirm Einstein's prediction. This is...

  11. Measuring Gravity in International Trade Flows

    Directory of Open Access Journals (Sweden)

    E. Young Song

    2004-12-01

    Full Text Available The purpose of this paper is two-fold. One is to clarify the concept of gravity in international trade flows. The other is to measure the strength of gravity in international trade flows in a way that is consistent with a well-defined concept of gravity. This paper shows that the widely accepted belief that specialization is the source of gravity is not well grounded on theory. We propose to define gravity in international trade as the force that makes the market shares of an exporting country constant in all importing countries, regardless of their sizes. In a stochastic context, we should interpret it as implying that the strength of gravity increases i as the correlation between market shares and market sizes gets weaker and ii as the variance of market shares gets smaller. We estimate an empirical gravity equation thoroughly based on this definition of gravity. We find that a strong degree of gravity exists in most bilateral trade, regardless of income levels of countries, and in trade of most manThe purpose of this paper is two-fold. One is to clarify the concept of gravity in international trade flows. The other is to measure the strength of gravity in international trade flows in a way that is consistent with a well-defined concept of gravity. This paper shows that the widely accepted belief that specialization is the source of gravity is not well grounded on theory. We propose to define gravity in international trade as the force that makes the market shares of an exporting country constant in all importing countries, regardless of their sizes. In a stochastic context, we should interpret it as implying that the strength of gravity increases i as the correlation between market shares and market sizes gets weaker and ii as the variance of market shares gets smaller. We estimate an empirical gravity equation thoroughly based on this definition of gravity. We find that a strong degree of gravity exists in most bilateral trade, regardless of

  12. Propagation of inertial-gravity waves on an island shelf

    Science.gov (United States)

    Bondur, V. G.; Sabinin, K. D.; Grebenyuk, Yu. V.

    2015-09-01

    The propagation of inertial-gravity waves (IGV) at the boundary of the Pacific shelf near the island of Oahu (Hawaii), whose generation was studied in the first part of this work [1], is analyzed. It is shown that a significant role there is played by the plane oblique waves; whose characteristics were identified by the method of estimating 3D wave parameters for the cases when the measurements are available only for two verticals. It is established that along with the descending propagation of energy that is typical of IGVs, wave packets ascend from the bottom to the upper layers, which is caused by the emission of waves from intense jets of discharged waters flowing out of a diffusor located at the bottom.

  13. Gravity the quest for gravitational wave

    CERN Document Server

    Binétruy, Pierre

    2018-01-01

    What force do the Big Bang, the expansion of the Universe, dark matter and dark energy, black holes, and gravitational waves all have in common? This book uncovers gravity as a key to understanding these fascinating phenomena that have so captivated public interest in recent years. Readers will discover the latest findings on how this familiar force in our everyday lives powers the most colossal changes in the Universe. Written by the widely recognized French public scientist and leading astrophysicist Pierre Binetruy, the book also explains the recent experimental confirmation of the existence of gravitational waves.

  14. Seeding and layering of equatorial spread F by gravity waves

    International Nuclear Information System (INIS)

    Hysell, D.L.; Kelley, M.C.; Swartz, W.E.; Woodman, R.F.

    1990-01-01

    Studies dating back more than 15 years have presented evidence that atmospheric gravity waves play a role in initiating nighttime equatorial F region instabilities. This paper analyzes a spectabular spread F event that for the first time demonstrates a layering which, the authors argue, is controlled by a gravity wave effect. The 50-km vertical wavelength of a gravity wave which they have found is related theoretically to a plasma layering irregularity that originated at low altitudes and then was convected, intact, to higher altitudes. Gravity waves also seem to have determined bottomside intermediate scale undulations, although this fact is not as clear in the data. The neutral wind dynamo effect yields wave number conditions on the gravity wave's ability to modulate the Rayleigh-Taylor instaiblity process. Finally, after evaluating the gravity wave dispersion relation and spatial resonance conditions, we estimate the properties of the seeding wave

  15. Waves and compressible flow

    CERN Document Server

    Ockendon, Hilary

    2016-01-01

    Now in its second edition, this book continues to give readers a broad mathematical basis for modelling and understanding the wide range of wave phenomena encountered in modern applications.  New and expanded material includes topics such as elastoplastic waves and waves in plasmas, as well as new exercises.  Comprehensive collections of models are used to illustrate the underpinning mathematical methodologies, which include the basic ideas of the relevant partial differential equations, characteristics, ray theory, asymptotic analysis, dispersion, shock waves, and weak solutions. Although the main focus is on compressible fluid flow, the authors show how intimately gasdynamic waves are related to wave phenomena in many other areas of physical science.   Special emphasis is placed on the development of physical intuition to supplement and reinforce analytical thinking. Each chapter includes a complete set of carefully prepared exercises, making this a suitable textbook for students in applied mathematics, ...

  16. Flow and instability in quantum gravity

    International Nuclear Information System (INIS)

    Douglas, M.R.; Seiberg, N.; Shenker, S.H.

    1990-01-01

    We study the flow from the m=3 multicritical matrix theory, unambiguously defined by Brezin, Marinari and Parisi, to the m=2 pure gravity theory. We find behavior in the flow indicative of a non-perturbative instability in this definition of non-perturbative pure quantum gravity. We expect a similar situation for all m even theories. Other definitions of these theories are briefly discussed. (orig.)

  17. Acoustic-gravity waves in atmospheric and oceanic waveguides.

    Science.gov (United States)

    Godin, Oleg A

    2012-08-01

    A theory of guided propagation of sound in layered, moving fluids is extended to include acoustic-gravity waves (AGWs) in waveguides with piecewise continuous parameters. The orthogonality of AGW normal modes is established in moving and motionless media. A perturbation theory is developed to quantify the relative significance of the gravity and fluid compressibility as well as sensitivity of the normal modes to variations in sound speed, flow velocity, and density profiles and in boundary conditions. Phase and group speeds of the normal modes are found to have certain universal properties which are valid for waveguides with arbitrary stratification. The Lamb wave is shown to be the only AGW normal mode that can propagate without dispersion in a layered medium.

  18. Stability of Fluvial and Gravity-flow Antidunes

    Science.gov (United States)

    Fedele, J. J.; Hoyal, D. C. J. D.; Demko, T. M.

    2017-12-01

    Antidunes develop as a consequence of interface (free surface) deformation and sediment transport feedback in supercritical flows. Fluvial (open-channel flow) antidunes have been studied extensively in the laboratory and the field, and recognized in ancient sedimentary deposits. Experiments on gravity flow (turbidity and density currents) antidunes indicate that they are more stable and long-lived than their fluvial counterpart but the mechanism controlling this stability is poorly understood. Sea floor bathymetric and subsurface data suggest that large-scale, antidune-like sediment waves are extremely common in deep-water, found in a wide range of settings and sediment characteristics. While most of these large features have been interpreted as cyclic steps, the term has been most likely overused due to the lack of recognition criteria and basic understanding on the differences between antidunes and cyclic steps formed under gravity flows. In principle, cyclic steps should be more common in confined or channel-lobe transition settings where flows tend to be more energetic or focused, while antidunes should prevail in regions of less confinement, under sheet-like or expanding flows. Using published, fluvial stable-antidune data, we show that the simplified 1D, mechanical-energy based analysis of flow over a localized fixed obstacle (Long, 1954; Baines, 1995; Kubo and Yokokawa, 2001) is inaccurate for representing flow over antidunes and their stability. Instead, a more detailed analysis of a flow along a long-wavelength (in relation to flow thickness) wavy bed that also considers the interactions between flow and sediment transport is used to infer conditions of antidune stability and the breaking of surface waves. In particular, the position of the surface wave crest in relation to the bedform crest, along with the role of average flow velocity, surface velocity, and surface wave celerity appear relevant in determining antidune instability. The analysis is

  19. A case study of gravity waves in noctilucent clouds

    Directory of Open Access Journals (Sweden)

    P. Dalin

    2004-06-01

    Full Text Available We present a case study of a noctilucent cloud (NLC display appearing on 10-11 August 2000 over Northern Sweden. Clear wave structures were visible in the clouds and time-lapse photography was used to derive the parameters characterising the gravity waves which could account for the observed NLC modulation. Using two nearby atmospheric radars, the Esrange MST Radar data and Andoya MF radar, we have identified gravity waves propagating upward from the upper stratosphere to NLC altitudes. The wave parameters derived from the radar measurements support the suggestion that gravity waves are responsible for the observed complex wave dynamics in the NLC.

  20. How to turn gravity waves into Alfven waves and other such tricks

    International Nuclear Information System (INIS)

    Newington, Marie E; Cally, Paul S

    2011-01-01

    Recent observations of travelling gravity waves at the base of the chromosphere suggest an interplay between gravity wave propagation and magnetic field. Our aims are: to explain the observation that gravity wave flux is suppressed in magnetic regions; to understand why we see travelling waves instead of standing waves; and to see if gravity waves can undergo mode conversion and couple to Alfven waves in regions where the plasma beta is of order unity. We model gravity waves in a VAL C atmosphere, subject to a uniform magnetic field of various orientations, considering both adiabatic and radiatively damped propagation. Results indicate that in the presence of a magnetic field, the gravity wave can propagate as a travelling wave, with the magnetic field orientation playing a crucial role in determining the wave character. For the majority of magnetic field orientations, the gravity wave is reflected at low heights as a slow magneto-acoustic wave, explaining the observation of reduced flux in magnetic regions. In a highly inclined magnetic field, the gravity wave undergoes mode conversion to either field guided acoustic waves or Alfven waves. The primary effect of incorporating radiative damping is a reduction in acoustic and magnetic fluxes measured at the top of the integration region. By demonstrating the mode conversion of gravity waves to Alfven waves, this work identifies a possible pathway for energy transport from the solar surface to the upper atmosphere.

  1. Shear waves in inhomogeneous, compressible fluids in a gravity field.

    Science.gov (United States)

    Godin, Oleg A

    2014-03-01

    While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere.

  2. Waves in separated two-phase flow

    International Nuclear Information System (INIS)

    Pols, R.M.

    1998-06-01

    This dissertation presents an integral approach to the modelling of co-current flow of liquid and gas for a class of non-linear wave problems. Typically the liquid phase and the gas phase are decoupled and the liquid is depth averaged. The resulting non-linear shallow water equations are solved to predict the behaviour of the finite amplitude waves. The integral approach is applied to the modelling of two-dimensional waves in a horizontal and slightly inclined rectangular channel, two-dimensional waves in a vertical pipe and three-dimensional waves in a horizontal tube. For flow in a horizontal or slightly inclined channel the liquid is driven by the interfacial shear from the gas phase and the surface is subject to extensive wave action. For thin liquid films the pressure in the liquid may be taken as hydrostatic and gravity acts as a restoring force on the liquid. Roll wave solutions to the non-linear shallow water equations are sought corresponding to an interfacial shear stress dependent on the liquid film height. Wave solutions are shown to exist but only for parameters within a defined range dependent on the channel inclination, interfacial roughness and linear dependence on the liquid film height of the shear stresses. Such solutions are discontinuous and are pieced together by a jump where mass and momentum are conserved. The model calculations on wave height and wave velocity are compared with experimental data. The essentially two-dimensional analysis developed for stratified horizontal flow can be extended to quasi three-dimensional flow in the case of shallow liquid depth for a circular pipe. In this case the liquid depth changes with circumferential position and consequently modifies the interfacial shear exerted on the liquid surface creating a wave spreading mechanism alongside changing the wave profile across the pipe. The wave spreading mechanism supposes a wave moving in axial direction at a velocity faster than the liquid thereby sweeping liquid

  3. Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

    Science.gov (United States)

    Meyer, Catrin I.; Ern, Manfred; Hoffmann, Lars; Trinh, Quang Thai; Alexander, M. Joan

    2018-01-01

    We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS) aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS) aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their vertical and horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is 9 times better than that of the operational retrieval. HIRDLS provides 2-D spectral information of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short-horizontal-wavelength gravity waves, and HIRDLS as a limb sounder is more sensitive to short-vertical-wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations. A calculated momentum flux factor indicates that the waves seen by AIRS contribute significantly to momentum flux, even if the AIRS temperature variance may be small compared to HIRDLS. The stratospheric wave structures observed by AIRS and HIRDLS often agree very well. Case studies of a mountain wave event and a non-orographic wave event demonstrate that the observed phase structures of AIRS and HIRDLS are also similar. AIRS has a coarser vertical resolution, which results in an attenuation of the amplitude and coarser vertical wavelengths than for HIRDLS. However, AIRS has a much higher horizontal resolution, and the propagation direction of the waves can be clearly identified in geographical maps. The horizontal orientation of the phase fronts can be deduced from AIRS 3-D temperature fields. This is a restricting factor for gravity wave analyses of limb measurements. Additionally, temperature variances with respect to stratospheric gravity wave activity are compared on a

  4. Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

    Directory of Open Access Journals (Sweden)

    C. I. Meyer

    2018-01-01

    Full Text Available We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their vertical and horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is 9 times better than that of the operational retrieval. HIRDLS provides 2-D spectral information of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short-horizontal-wavelength gravity waves, and HIRDLS as a limb sounder is more sensitive to short-vertical-wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations. A calculated momentum flux factor indicates that the waves seen by AIRS contribute significantly to momentum flux, even if the AIRS temperature variance may be small compared to HIRDLS. The stratospheric wave structures observed by AIRS and HIRDLS often agree very well. Case studies of a mountain wave event and a non-orographic wave event demonstrate that the observed phase structures of AIRS and HIRDLS are also similar. AIRS has a coarser vertical resolution, which results in an attenuation of the amplitude and coarser vertical wavelengths than for HIRDLS. However, AIRS has a much higher horizontal resolution, and the propagation direction of the waves can be clearly identified in geographical maps. The horizontal orientation of the phase fronts can be deduced from AIRS 3-D temperature fields. This is a restricting factor for gravity wave analyses of limb measurements. Additionally, temperature variances with respect to stratospheric gravity wave activity are

  5. Internal Gravity Waves in the Magnetized Solar Atmosphere. I. Magnetic Field Effects

    Energy Technology Data Exchange (ETDEWEB)

    Vigeesh, G.; Steiner, O. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstrasse 6, D-79104 Freiburg (Germany); Jackiewicz, J., E-mail: vigeesh@leibniz-kis.de [New Mexico State University, Department of Astronomy, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003 (United States)

    2017-02-01

    Observations of the solar atmosphere show that internal gravity waves are generated by overshooting convection, but are suppressed at locations of magnetic flux, which is thought to be the result of mode conversion into magnetoacoustic waves. Here, we present a study of the acoustic-gravity wave spectrum emerging from a realistic, self-consistent simulation of solar (magneto)convection. A magnetic field free, hydrodynamic simulation and a magnetohydrodynamic (MHD) simulation with an initial, vertical, homogeneous field of 50 G flux density were carried out and compared with each other to highlight the effect of magnetic fields on the internal gravity wave propagation in the Sun’s atmosphere. We find that the internal gravity waves are absent or partially reflected back into the lower layers in the presence of magnetic fields and argue that the suppression is due to the coupling of internal gravity waves to slow magnetoacoustic waves still within the high- β region of the upper photosphere. The conversion to Alfvén waves is highly unlikely in our model because there is no strongly inclined magnetic field present. We argue that the suppression of internal waves observed within magnetic flux concentrations may also be due to nonlinear breaking of internal waves due to vortex flows that are ubiquitously present in the upper photosphere and the chromosphere.

  6. Gravity waves from tachyonic preheating after hybrid inflation

    Energy Technology Data Exchange (ETDEWEB)

    Dufaux, Jean-Francois [Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Felder, Gary [Department of Physics, Clark Science Center, Smith College, Northampton, MA 01063 (United States); Kofman, Lev [CITA, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Navros, Olga, E-mail: jeff.dufaux@uam.es, E-mail: gfelder@email.smith.edu, E-mail: kofman@cita.utoronto.ca, E-mail: navros@email.unc.edu [Department of Mathematics, University of North Carolina Chapel Hill, CB3250 Philips Hall, Chapel Hill, NC 27599 (United States)

    2009-03-15

    We study the stochastic background of gravitational waves produced from preheating in hybrid inflation models. We investigate different dynamical regimes of preheating in these models and we compute the resulting gravity wave spectra using analytical estimates and numerical simulations. We discuss the dependence of the gravity wave frequencies and amplitudes on the various potential parameters. We find that large regions of the parameter space leads to gravity waves that may be observable in upcoming interferometric experiments, including Advanced LIGO, but this generally requires very small coupling constants.

  7. Experimental Observation of Negative Effective Gravity in Water Waves

    Science.gov (United States)

    Hu, Xinhua; Yang, Jiong; Zi, Jian; Chan, C. T.; Ho, Kai-Ming

    2013-01-01

    The gravity of Earth is responsible for the formation of water waves and usually difficult to change. Although negative effective gravity was recently predicted theoretically in water waves, it has not yet been observed in experiments and remains a mathematical curiosity which is difficult to understand. Here we experimentally demonstrate that close to the resonant frequency of purposely-designed resonating units, negative effective gravity can occur for water waves passing through an array of resonators composing of bottom-mounted split tubes, resulting in the prohibition of water wave propagation. It is found that when negative gravity occurs, the averaged displacement of water surface in a unit cell of the array has a phase difference of π to that along the boundary of the unit cell, consistent with theoretical predictions. Our results provide a mechanism to block water waves and may find applications in wave energy conversion and coastal protection. PMID:23715132

  8. Investigating gravity waves evidences in the Venus upper atmosphere

    Science.gov (United States)

    Migliorini, Alessandra; Altieri, Francesca; Shakun, Alexey; Zasova, Ludmila; Piccioni, Giuseppe; Bellucci, Giancarlo; Grassi, Davide

    2014-05-01

    We present a method to investigate gravity waves properties in the upper mesosphere of Venus, through the O2 nightglow observations acquired with the imaging spectrometer VIRTIS on board Venus Express. Gravity waves are important dynamical features that transport energy and momentum. They are related to the buoyancy force, which lifts air particles. Then, the vertical displacement of air particles produces density changes that cause gravity to act as restoring force. Gravity waves can manifest through fluctuations on temperature and density fields, and hence on airglow intensities. We use the O2 nightglow profiles showing double peaked structures to study the influence of gravity waves in shaping the O2 vertical profiles and infer the waves properties. In analogy to the Earth's and Mars cases, we use a well-known theory to model the O2 nightglow emissions affected by gravity waves propagation. Here we propose a statistical discussion of the gravity waves characteristics, namely vertical wavelength and wave amplitude, with respect to local time and latitude. The method is applied to about 30 profiles showing double peaked structures, and acquired with the VIRTIS/Venus Express spectrometer, during the mission period from 2006-07-05 to 2008-08-15.

  9. Internal wave structures in abyssal cataract flows

    Science.gov (United States)

    Makarenko, Nikolay; Liapidevskii, Valery; Morozov, Eugene; Tarakanov, Roman

    2014-05-01

    We discuss some theoretical approaches, experimental results and field data concerning wave phenomena in ocean near-bottom stratified flows. Such strong flows of cold water form everywhere in the Atlantic abyssal channels, and these currents play significant role in the global water exchange. Most interesting wave structures arise in a powerful cataract flows near orographic obstacles which disturb gravity currents by forced lee waves, attached hydraulic jumps, mixing layers etc. All these effects were observed by the authors in the Romanche and Chain fracture zones of Atlantic Ocean during recent cruises of the R/V Akademik Ioffe and R/V Akademik Sergei Vavilov (Morozov et al., Dokl. Earth Sci., 2012, 446(2)). In a general way, deep-water cataract flows down the slope are similar to the stratified flows examined in laboratory experiments. Strong mixing in the sill region leads to the splitting of the gravity current into the layers having the fluids with different densities. Another peculiarity is the presence of critical layers in shear flows sustained over the sill. In the case under consideration, this critical level separates the flow of near-bottom cold water from opposite overflow. In accordance with known theoretical models and laboratory measurements, the critical layer can absorb and reflect internal waves generated by the topography, so the upward propagation of these perturbations is blocked from above. High velocity gradients were registered downstream in the vicinity of cataract and it indicates the existence of developed wave structures beyond the sill formed by intense internal waves. This work was supported by RFBR (grants No 12-01-00671-a, 12-08-10001-k and 13-08-10001-k).

  10. Intercomparison of stratospheric gravity wave observations with AIRS and IASI

    Directory of Open Access Journals (Sweden)

    L. Hoffmann

    2014-12-01

    Full Text Available Gravity waves are an important driver for the atmospheric circulation and have substantial impact on weather and climate. Satellite instruments offer excellent opportunities to study gravity waves on a global scale. This study focuses on observations from the Atmospheric Infrared Sounder (AIRS onboard the National Aeronautics and Space Administration Aqua satellite and the Infrared Atmospheric Sounding Interferometer (IASI onboard the European MetOp satellites. The main aim of this study is an intercomparison of stratospheric gravity wave observations of both instruments. In particular, we analyzed AIRS and IASI 4.3 μm brightness temperature measurements, which directly relate to stratospheric temperature. Three case studies showed that AIRS and IASI provide a clear and consistent picture of the temporal development of individual gravity wave events. Statistical comparisons based on a 5-year period of measurements (2008–2012 showed similar spatial and temporal patterns of gravity wave activity. However, the statistical comparisons also revealed systematic differences of variances between AIRS and IASI that we attribute to the different spatial measurement characteristics of both instruments. We also found differences between day- and nighttime data that are partly due to the local time variations of the gravity wave sources. While AIRS has been used successfully in many previous gravity wave studies, IASI data are applied here for the first time for that purpose. Our study shows that gravity wave observations from different hyperspectral infrared sounders such as AIRS and IASI can be directly related to each other, if instrument-specific characteristics such as different noise levels and spatial resolution and sampling are carefully considered. The ability to combine observations from different satellites provides an opportunity to create a long-term record, which is an exciting prospect for future climatological studies of stratospheric

  11. Gravity Effects in Microgap Flow Boiling

    Science.gov (United States)

    Robinson, Franklin; Bar-Cohen, Avram

    2017-01-01

    Increasing integration density of electronic components has exacerbated the thermal management challenges facing electronic system developers. The high power, heat flux, and volumetric heat generation of emerging devices are driving the transition from remote cooling, which relies on conduction and spreading, to embedded cooling, which facilitates direct contact between the heat-generating device and coolant flow. Microgap coolers employ the forced flow of dielectric fluids undergoing phase change in a heated channel between devices. While two phase microcoolers are used routinely in ground-based systems, the lack of acceptable models and correlations for microgravity operation has limited their use for spacecraft thermal management. Previous research has revealed that gravitational acceleration plays a diminishing role as the channel diameter shrinks, but there is considerable variation among the proposed gravity-insensitive channel dimensions and minimal research on rectangular ducts. Reliable criteria for achieving gravity-insensitive flow boiling performance would enable spaceflight systems to exploit this powerful thermal management technique and reduce development time and costs through reliance on ground-based testing. In the present effort, the authors have studied the effect of evaporator orientation on flow boiling performance of HFE7100 in a 218 m tall by 13.0 mm wide microgap cooler. Similar heat transfer coefficients and critical heat flux were achieved across five evaporator orientations, indicating that the effect of gravity was negligible.

  12. Gravity waves observed from the Equatorial Wave Studies (EWS campaign during 1999 and 2000 and their role in the generation of stratospheric semiannual oscillations

    Directory of Open Access Journals (Sweden)

    V. Deepa

    2006-10-01

    Full Text Available The altitude profiles of temperature fluctuations in the stratosphere and mesosphere observed with the Rayleigh Lidar at Gadanki (13.5° N, 79.2° E on 30 nights during January to March 1999 and 21 nights during February to April 2000 were analysed to bring out the temporal and vertical propagation characteristics of gravity wave perturbations. The gravity wave perturbations showed periodicities in the 0.5–3-h range and attained large amplitudes (4–5 K in the mesosphere. The phase propagation characteristics of gravity waves with different periods showed upward wave propagation with a vertical wavelength of 5–7 km. The mean flow acceleration computed from the divergence of momentum flux of gravity waves is compared with that calculated from monthly values of zonal wind obtained from RH-200 rockets flights. Thus, the contribution of gravity waves towards the generation of Stratospheric Semi Annual Oscillation (SSAO is estimated.

  13. Geometric flows in Horava-Lifshitz gravity

    CERN Document Server

    Bakas, Ioannis; Lust, Dieter; Petropoulos, Marios

    2010-01-01

    We consider instanton solutions of Euclidean Horava-Lifshitz gravity in four dimensions satisfying the detailed balance condition. They are described by geometric flows in three dimensions driven by certain combinations of the Cotton and Ricci tensors as well as the cosmological-constant term. The deformation curvature terms can have competing behavior leading to a variety of fixed points. The instantons interpolate between any two fixed points, which are vacua of topologically massive gravity with Lambda > 0, and their action is finite. Special emphasis is placed on configurations with SU(2) isometry associated with homogeneous but generally non-isotropic Bianchi IX model geometries. In this case, the combined Ricci-Cotton flow reduces to an autonomous system of ordinary differential equations whose properties are studied in detail for different couplings. The occurrence and stability of isotropic and anisotropic fixed points are investigated analytically and some exact solutions are obtained. The correspond...

  14. Gravity waves from quantum stress tensor fluctuations in inflation

    International Nuclear Information System (INIS)

    Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

    2011-01-01

    We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

  15. Gravity waves from quantum stress tensor fluctuations in inflation

    Science.gov (United States)

    Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

    2011-11-01

    We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

  16. Waves on radial film flows

    Science.gov (United States)

    Cholemari, Murali R.; Arakeri, Jaywant H.

    2005-08-01

    We study the stability of surface waves on the radial film flow created by a vertical cylindrical water jet striking a horizontal plate. In such flows, surface waves have been found to be unstable and can cause transition to turbulence. This surface-wave-induced transition is different from the well-known Tollmien-Schlichting wave-induced transition. The present study aims at understanding the instability and the transition process. We do a temporal stability analysis by assuming the flow to be locally two-dimensional but including spatial variations to first order in the basic flow. The waves are found to be dispersive, mostly unstable, and faster than the mean flow. Spatial variation is the major destabilizing factor. Experiments are done to test the results of the linear stability analysis and to document the wave breakup and transition. Comparison between theory and experiments is fairly good and indicates the adequacy of the model.

  17. pp waves of conformal gravity with self-interacting source

    International Nuclear Information System (INIS)

    Ayon-Beato, Eloy; Hassaine, Mokhtar

    2005-01-01

    Recently, Deser, Jackiw and Pi have shown that three-dimensional conformal gravity with a source given by a conformally coupled scalar field admits pp wave solutions. In this paper, we consider this model with a self-interacting potential preserving the conformal structure. A pp wave geometry is also supported by this system and, we show that this model is equivalent to topologically massive gravity with a cosmological constant whose value is given in terms of the potential strength

  18. Gravity Waves and Wind-Farm Efficiency in Neutral and Stable Conditions

    Science.gov (United States)

    Allaerts, Dries; Meyers, Johan

    2018-02-01

    We use large-eddy simulations (LES) to investigate the impact of stable stratification on gravity-wave excitation and energy extraction in a large wind farm. To this end, the development of an equilibrium conventionally neutral boundary layer into a stable boundary layer over a period of 8 h is considered, using two different cooling rates. We find that turbulence decay has considerable influence on the energy extraction at the beginning of the boundary-layer transition, but afterwards, energy extraction is dominated by geometrical and jet effects induced by an inertial oscillation. It is further shown that the inertial oscillation enhances gravity-wave excitation. By comparing LES results with a simple one-dimensional model, we show that this is related to an interplay between wind-farm drag, variations in the Froude number and the dispersive effects of vertically-propagating gravity waves. We further find that the pressure gradients induced by gravity waves lead to significant upstream flow deceleration, reducing the average turbine output compared to a turbine in isolated operation. This leads us to the definition of a non-local wind-farm efficiency, next to a more standard wind-farm wake efficiency, and we show that both can be of the same order of magnitude. Finally, an energy flux analysis is performed to further elucidate the effect of gravity waves on the flow in the wind farm.

  19. OPG nuclear - deaerator gravity flow test

    International Nuclear Information System (INIS)

    Davidge, E.; Sanchez, R.; Misra, A.; Vecchiarelli, J.

    2013-01-01

    Following a total loss of all AC power, preexisting SG and SGECS are consumed to maintain fuel cooling. These inventories last ~3.5 hours. Additional time is needed to establish offsite Emergency Mitigating Equipment (EME). EME are portable generators/pumps which pump screened lake water directly to boilers, moderator, HTS, vault, etc., as required. Deaerator storage tank inventory can provide water to SGs by gravity draining (additional ~5.5 hours). Deaerator and deaerator storage tank are the highest points in the feedwater system and are normally used to remove air and impurities from the secondary side and store demineralized water. Calculations were done to determine minimum flow requirements to steam generators in a Beyond Design Basis Accident (BDBA). Additional calculations were performed to determine how long deaerator water can achieve this minimum flow rate. A validation test was required to demonstrate that the required flow rates could be achieved, and interim heat sink could be established. Tests were performed on shut-down units during planned outages. Tests successfully demonstrated capability of the interim deaerator gravity drain heat sink. Tests results were very close to analytical predictions. As expected, actual flow rate was slightly higher than predicted since conservative assumptions were used.

  20. Free surface flows under compensated gravity conditions

    CERN Document Server

    Dreyer, Miachel E

    2007-01-01

    This book considers the behavior of fluids in a low-gravity environment with special emphasis on application in PMD (propellant management device) systems . In the compensated gravity environment of a spacecraft, the hydrostatic pressure decreases to very low values depending on the residual acceleration, and surface tension forces become dominant. Consequently, surface tension can be used to transport and position liquids if the residual acceleration and the resulting hydrostatic pressure are small compared to the capillary pressure. One prominent application is the use of PMDs in surface-tension satellite tanks. PMDs must ensure that the tank outlet is covered with liquid whenever outflow is demanded. Furthermore, PMDs are used to ensure expulsion and refilling of tanks for liquids and gases for life support, reactants, and experiment supplies. Since most of the PMD designs are not testable on ground and thus rely on analytical or numerical concepts, this book treats three different flow problems with analy...

  1. No further gravitational wave modes in F(T) gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bamba, Kazuharu, E-mail: bamba@kmi.nagoya-u.ac.jp [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Capozziello, Salvatore, E-mail: capozziello@na.infn.it [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Dipartimento di Fisica, Università di Napoli “Federico II” (Italy); INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli (Italy); De Laurentis, Mariafelicia, E-mail: felicia@na.infn.it [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Dipartimento di Fisica, Università di Napoli “Federico II” (Italy); INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli (Italy); Nojiri, Shin' ichi, E-mail: nojiri@phys.nagoya-u.ac.jp [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Sáez-Gómez, Diego, E-mail: diego.saezgomez@uct.ac.za [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Astrophysics, Cosmology and Gravity Centre (ACGC) and Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town (South Africa); Fisika Teorikoaren eta Zientziaren Historia Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea, 644 Posta Kutxatila, 48080 Bilbao (Spain)

    2013-11-25

    We explore the possibility of further gravitational wave modes in F(T) gravity, where T is the torsion scalar in teleparallelism. It is explicitly demonstrated that gravitational wave modes in F(T) gravity are equivalent to those in General Relativity. This result is achieved by calculating the Minkowskian limit for a class of analytic function of F(T). This consequence is also confirmed by the preservative analysis around the flat background in the weak field limit with the scalar–tensor representation of F(T) gravity.

  2. No further gravitational wave modes in F(T) gravity

    International Nuclear Information System (INIS)

    Bamba, Kazuharu; Capozziello, Salvatore; De Laurentis, Mariafelicia; Nojiri, Shin'ichi; Sáez-Gómez, Diego

    2013-01-01

    We explore the possibility of further gravitational wave modes in F(T) gravity, where T is the torsion scalar in teleparallelism. It is explicitly demonstrated that gravitational wave modes in F(T) gravity are equivalent to those in General Relativity. This result is achieved by calculating the Minkowskian limit for a class of analytic function of F(T). This consequence is also confirmed by the preservative analysis around the flat background in the weak field limit with the scalar–tensor representation of F(T) gravity

  3. Electromagnetic internal gravity waves in the Earth's ionospheric E-layer

    International Nuclear Information System (INIS)

    Kaladze, T.D.; Tsamalashvili, L.V.; Kaladze, D.T.

    2011-01-01

    In the Earth's ionospheric E-layer existence of the new waves connecting with the electromagnetic nature of internal gravity waves is shown. They represent the mixture of the ordinary internal gravity waves and the new type of dispersive Alfven waves. -- Highlights: ► Existence of electromagnetic internal gravity waves in the ionospheric E-layer is shown. ► Electromagnetic nature of internal gravity waves is described. ► Appearance of the new dispersive Alfven waves is shown.

  4. Middle Atmosphere Dynamics with Gravity Wave Interactions in the Numerical Spectral Model: Tides and Planetary Waves

    Science.gov (United States)

    Mayr, Hans G.; Mengel, J. G.; Chan, K. L.; Huang, F. T.

    2010-01-01

    As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) global-scale inertio gravity waves. Numerical experiments are discussed that illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations. Keywords: Theoretical modeling, Middle atmosphere dynamics, Gravity wave interactions, Migrating and non-migrating tides, Planetary waves, Global-scale inertio gravity waves.

  5. Wave Interactions and Fluid Flows

    Science.gov (United States)

    Craik, Alex D. D.

    1988-07-01

    This up-to-date and comprehensive account of theory and experiment on wave-interaction phenomena covers fluids both at rest and in their shear flows. It includes, on the one hand, water waves, internal waves, and their evolution, interaction, and associated wave-driven means flow and, on the other hand, phenomena on nonlinear hydrodynamic stability, especially those leading to the onset of turbulence. This study provide a particularly valuable bridge between these two similar, yet different, classes of phenomena. It will be of value to oceanographers, meteorologists, and those working in fluid mechanics, atmospheric and planetary physics, plasma physics, aeronautics, and geophysical and astrophysical fluid dynamics.

  6. VHF radar observations of gravity waves at a low latitude

    Directory of Open Access Journals (Sweden)

    G. Dutta

    1999-08-01

    Full Text Available Wind observations made at Gadanki (13.5°N by using Indian MST Radar for few days in September, October, December 1995 and January, 1996 have been analyzed to study gravity wave activity in the troposphere and lower stratosphere. Horizontal wind variances have been computed for gravity waves of period (2-6 h from the power spectral density (PSD spectrum. Exponential curves of the form eZ/H have been fitted by least squares technique to these variance values to obtain height variations of the irregular winds upto the height of about 15 km, where Z is the height in kilometers. The value of H, the scale height, as determined from curve fitting is found to be less than the theoretical value of scale height of neutral atmosphere in this region, implying that the waves are gaining energy during their passage in the troposphere. In other words, it indicates that the sources of gravity waves are present in the troposphere. The energy densities of gravity wave fluctuations have been computed. Polynomial fits to the observed values show that wave energy density increases in the troposphere, its source region, and then decreases in the lower stratosphere.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides

  7. Properties of surface waves in granular media under gravity

    International Nuclear Information System (INIS)

    Zheng He-Peng

    2014-01-01

    Acoustical waves propagating along the free surface of granular media under gravity are investigated in the framework of elasticity theory. The influence of stress on a surface wave is analyzed. The results have shown that two types of surface waves, namely sagittal and transverse modes exist depending on initial stress states, which may have some influence on the dispersion relations of surface waves, but the influence is not great. Considering that the present experimental accuracy is far from distinguishing this detail, the validity of elasticity theory on the surface waves propagating in granular media can still be maintained. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  8. Gravity influence on heat transfer rate in flow boiling

    NARCIS (Netherlands)

    Baltis, C.H.M.; Celata, G.P.; Cumo, M.; Saraceno, L.; Zummo, G.

    2012-01-01

    The aim of the present paper is to describe the results of flow boiling heat transfer at low gravity and compare them with those obtained at earth gravity, evaluating possible differences. The experimental campaigns at low gravity have been performed with parabolic flights. The paper will show the

  9. Flow Boiling Critical Heat Flux in Reduced Gravity

    Science.gov (United States)

    Mudawar, Issam; Zhang, Hui; Hasan, Mohammad M.

    2004-01-01

    This study provides systematic method for reducing power consumption in reduced gravity systems by adopting minimum velocity required to provide adequate CHF and preclude detrimental effects of reduced gravity . This study proves it is possible to use existing 1 ge flow boiling and CHF correlations and models to design reduced gravity systems provided minimum velocity criteria are met

  10. Planetary wave-gravity wave interactions during mesospheric inversion layer events

    Science.gov (United States)

    Ramesh, K.; Sridharan, S.; Raghunath, K.; Vijaya Bhaskara Rao, S.; Bhavani Kumar, Y.

    2013-07-01

    lidar temperature observations over Gadanki (13.5°N, 79.2°E) show a few mesospheric inversion layer (MIL) events during 20-25 January 2007. The zonal mean removed SABER temperature shows warm anomalies around 50°E and 275°E indicating the presence of planetary wave of zonal wave number 2. The MIL amplitudes in SABER temperature averaged for 10°N-15°N and 70°E-90°E show a clear 2 day wave modulation during 20-28 January 2007. Prior to 20 January 2007, a strong 2day wave (zonal wave number 2) is observed in the height region of 80-90 km and it gets largely suppressed during 20-26 January 2007 as the condition for vertical propagation is not favorable, though it prevails at lower heights. The 10 day mean zonal wind over Tirunelveli (8.7°N, 77.8°E) shows deceleration of eastward winds indicating the westward drag due to wave dissipation. The nightly mean MF radar observed zonal winds show the presence of alternating eastward and westward winds during the period of 20-26 January 2007. The two dimensional spectrum of Rayleigh lidar temperature observations available for the nights of 20, 22, and 24 January 2007 shows the presence of gravity wave activity with periods 18 min, 38 min, 38 min, and vertical wavelengths 6.4 km, 4.0 km, 6.4 km respectively. From the dispersion relation of gravity waves, it is inferred that these waves are internal gravity waves rather than inertia gravity waves with the horizontal phase speeds of ~40 m/s, ~37 m/s, and ~50 m/s respectively. Assuming the gravity waves are eastward propagating waves, they get absorbed only in the eastward local wind fields of the planetary wave thereby causing turbulence and eddy diffusion which can be inferred from the estimation of large drag force due to the breaking of gravity wave leading to the formation of large amplitude inversion events in alternate nights. The present study shows that, the mesospheric temperature inversion is caused mainly due to the gravity wave breaking and the inversion

  11. Causal properties of nonlinear gravitational waves in modified gravity

    Science.gov (United States)

    Suvorov, Arthur George; Melatos, Andrew

    2017-09-01

    Some exact, nonlinear, vacuum gravitational wave solutions are derived for certain polynomial f (R ) gravities. We show that the boundaries of the gravitational domain of dependence, associated with events in polynomial f (R ) gravity, are not null as they are in general relativity. The implication is that electromagnetic and gravitational causality separate into distinct notions in modified gravity, which may have observable astrophysical consequences. The linear theory predicts that tachyonic instabilities occur, when the quadratic coefficient a2 of the Taylor expansion of f (R ) is negative, while the exact, nonlinear, cylindrical wave solutions presented here can be superluminal for all values of a2. Anisotropic solutions are found, whose wave fronts trace out time- or spacelike hypersurfaces with complicated geometric properties. We show that the solutions exist in f (R ) theories that are consistent with Solar System and pulsar timing experiments.

  12. The instability of internal gravity waves to localised disturbances

    Directory of Open Access Journals (Sweden)

    J. Vanneste

    1995-02-01

    Full Text Available The instability of an internal gravity wave due to nonlinear wave-wave interaction is studied theoretically and numerically. Three different aspects of this phenomenon are examined. 1. The influence of dissipation on both the resonant and the nonresonant interactions is analysed using a normal mode expansion of the basic equations. In particular, the modifications induced in the interaction domain are calculated and as a result some modes are shown to be destabilised by dissipation. 2. The evolution of an initial unstable disturbance of finite vertical extent is described as the growth of two secondary wave packets travelling at the same group velocity. A quasi-linear correction to the basic primary wave is calculated, corresponding to a localised amplitude decrease due to the disturbance growth. 3. Numerical experiments are carried out to study the effect of a basic shear on wave instability. It appears that the growing secondary waves can have a frequency larger than that of the primary wave, provided that the shear is sufficient. The instability of waves with large amplitude and long period, such as tides or planetary waves, could therefore be invoked as a possible mechanism for the generation of gravity waves with shorter period in the middle atmosphere.

  13. Particle dispersion and mixing induced by breaking internal gravity waves

    Science.gov (United States)

    Bouruet-Aubertot, Pascale; Koudella, C.; Staquet, C.; Winters, K. B.

    2001-01-01

    The purpose of this paper is to analyze diapycnal mixing induced by the breaking of an internal gravity wave — the primary wave — either standing or propagating. To achieve this aim we apply two different methods. The first method consists of a direct estimate of vertical eddy diffusion from particle dispersion while the second method relies upon potential energy budgets [Winters, K.B., Lombard, P.N., Riley, J.J., D'Asaro, E.A., 1995. J. Fluid Mech. 289, 115-128; Winters, K.B., D'Asaro, E.A., 1996. J. Fluid Mech. 317, 179-193]. The primary wave we consider is of small amplitude and is statically stable, a case for which the breaking process involves two-dimensional instabilities. The dynamics of the waves have been previously analyzed by means of two-dimensional direct numerical simulations [Bouruet-Aubertot, P., Sommeria, J., Staquet, C., 1995. J. Fluid Mech. 285, 265-301; Bouruet-Aubertot, P., Sommeria, J., Staquet, C., 1996. Dyn. Atmos. Oceans 29, 41-63; Koudella, C., Staquet, C., 1998. In: Davis, P. (Ed.), Proceedings of the IMA Conference on Mixing and Dispersion on Stably-stratified Flows, Dundee, September 1996. IMA Publication]. High resolution three-dimensional calculations of the same wave are also reported here [Koudella, C., 1999]. A local estimate of mixing is first inferred from the time evolution of sets of particles released in the flow during the breaking regime. We show that, after an early evolution dominated by shear effects, a diffusion law is reached and the dispersion coefficient is fairly independent of the initial seeding location of the particles in the flow. The eddy diffusion coefficient, K, is then estimated from the diapycnal diffusive flux. A good agreement with the value inferred from particle dispersion is obtained. This finding is of particular interest regarding the interpretation of in situ estimates of K inferred either from tracer dispersion or from microstructure measurements. Computation of the Cox number, equal to the

  14. Solitary wave and periodic wave solutions for the thermally forced gravity waves in atmosphere

    International Nuclear Information System (INIS)

    Li Ziliang

    2008-01-01

    By introducing a new transformation, a new direct and unified algebraic method for constructing multiple travelling wave solutions of general nonlinear evolution equations is presented and implemented in a computer algebraic system, which extends Fan's direct algebraic method to the case when r > 4. The solutions of a first-order nonlinear ordinary differential equation with a higher degree nonlinear term and Fan's direct algebraic method of obtaining exact solutions to nonlinear partial differential equations are applied to the combined KdV-mKdV-GKdV equation, which is derived from a simple incompressible non-hydrostatic Boussinesq equation with the influence of thermal forcing and is applied to investigate internal gravity waves in the atmosphere. As a result, by taking advantage of the new first-order nonlinear ordinary differential equation with a fifth-degree nonlinear term and an eighth-degree nonlinear term, periodic wave solutions associated with the Jacobin elliptic function and the bell and kink profile solitary wave solutions are obtained under the effect of thermal forcing. Most importantly, the mechanism of propagation and generation of the periodic waves and the solitary waves is analysed in detail according to the values of the heating parameter, which show that the effect of heating in atmosphere helps to excite westerly or easterly propagating periodic internal gravity waves and internal solitary waves in atmosphere, which are affected by the local excitation structures in atmosphere. In addition, as an illustrative sample, the properties of the solitary wave solution and Jacobin periodic solution are shown by some figures under the consideration of heating interaction

  15. Generating gravity waves with matter and electromagnetic waves

    International Nuclear Information System (INIS)

    Barrabes, C.; Hogan, P A.

    2008-01-01

    If a homogeneous plane lightlike shell collides head on with a homogeneous plane electromagnetic shock wave having a step-function profile then no backscattered gravitational waves are produced. We demonstrate, by explicit calculation, that if the matter is accompanied by a homogeneous plane electromagnetic shock wave with a step-function profile then backscattered gravitational waves appear after the collision

  16. Unified flow regime predictions at earth gravity and microgravity

    International Nuclear Information System (INIS)

    Crowley, C.J.

    1990-01-01

    This paper illustrates the mechanistic models developed to predict flow regime transitions at earth gravity for various pipe inclinations can be successfully applied to existing microgravity flow regime data from several experiments. There is a tendency in the literature for flow regime comparisons in several inclination ranges and at various gravity (acceleration) levels to be treated by separate models, resulting in a proliferation of models for the prediction of flow regimes. One set of mechanistic models can be used to model the transitions between stratified, slug, bubbly, and annular flow regimes in pipes for all acceleration vectors and magnitudes from earth gravity to microgravity

  17. An axisymmetric inertia-gravity wave generator

    Science.gov (United States)

    Maurer, P.; Ghaemsaidi, S. J.; Joubaud, S.; Peacock, T.; Odier, P.

    2017-10-01

    There has been a rich interplay between laboratory experimental studies of internal waves and advancing understanding of their role in the ocean and atmosphere. In this study, we present and demonstrate the concept for a new form of laboratory internal wave generator that can excite axisymmetric wave fields of arbitrary radial structure. The construction and operation of the generator are detailed, and its capabilities are demonstrated through a pair of experiments using a Bessel function and a bourrelet (i.e., ring-shaped) configuration. The results of the experiments are compared with the predictions of an accompanying analytical model.

  18. Active Absorption of Irregular Gravity Waves in BEM-Models

    DEFF Research Database (Denmark)

    Brorsen, Michael; Frigaard, Peter

    1992-01-01

    The boundary element method is applied to the computation of irregular gravity waves. The boundary conditions at the open boundaries are obtained by a digital filtering technique, where the surface elevations in front of the open boundary are filtered numerically yielding the velocity to be presc...... to be prescribed at the boundary. By numerical examples it is shown that well designed filters can reduce the wave reflection to a few per cent over a frequency range corresponding to a Jonswap spectrum....

  19. Field verification of ADCP surface gravity wave elevation spectra

    NARCIS (Netherlands)

    Hoitink, A.J.F.; Peters, H.C.; Schroevers, M.

    2007-01-01

    Acoustic Doppler current profilers (ADCPs) can measure orbital velocities induced by surface gravity waves, yet the ADCP estimates of these velocities are subject to a relatively high noise level. The present paper introduces a linear filtration technique to significantly reduce the influence of

  20. Atmospheric gravity waves in the Red Sea: a new hotspot

    KAUST Repository

    Magalhaes, J. M.; Araú jo, I. B.; da Silva, J. C. B.; Grimshaw, R. H. J.; Davis, K.; Pineda, J.

    2011-01-01

    The region of the Middle East around the Red Sea (between 32° E and 44° E longitude and 12° N and 28° N latitude) is a currently undocumented hotspot for atmospheric gravity waves (AGWs). Satellite imagery shows evidence that this region is prone

  1. Atmospheric gravity waves due to the Tohoku-Oki tsunami observed in the thermosphere by GOCE

    NARCIS (Netherlands)

    Garcia, R.F.; Doornbos, E.N.; Bruinsma, S.; Hebert, H.

    2014-01-01

    Oceanic tsunami waves couple with atmospheric gravity waves, as previously observed through ionospheric and airglow perturbations. Aerodynamic velocities and density variations are computed from Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) accelerometer and thruster data during

  2. Dynamics of flexural gravity waves: from sea ice to Hawking radiation and analogue gravity.

    Science.gov (United States)

    Das, S; Sahoo, T; Meylan, M H

    2018-01-01

    The propagation of flexural gravity waves, routinely used to model wave interaction with sea ice, is studied, including the effect of compression and current. A number of significant and surprising properties are shown to exist. The occurrence of blocking above a critical value of compression is illustrated. This is analogous to propagation of surface gravity waves in the presence of opposing current and light wave propagation in the curved space-time near a black hole, therefore providing a novel system for studying analogue gravity. Between the blocking and buckling limit of the compressive force, the dispersion relation possesses three positive real roots, contrary to an earlier observation of having a single positive real root. Negative energy waves, in which the phase and group velocity point in opposite directions, are also shown to exist. In the presence of an opposing current and certain critical ranges of compressive force, the second blocking point shifts from the positive to the negative branch of the dispersion relation. Such a shift is known as the Hawking effect from the analogous behaviour in the theory of relativity which leads to Hawking radiation. The theory we develop is illustrated with simulations of linear waves in the time domain.

  3. Analytical Solution of Unsteady Gravity Flows of A Power-Law Fluid ...

    African Journals Online (AJOL)

    We present an analytical study of unsteady non-linear rheological effects of a power-law fluid under gravity. The fluid flows through a porous medium. The governing equations are derived and similarity solutions are determined. The results show the existence of traveling waves. It is assumed that the viscosity is temperature ...

  4. Asymptotic expansion of unsteady gravity flow of a power-law fluid ...

    African Journals Online (AJOL)

    We present a paper on the asymptotic expansion of unsteady non-linear rheological effects of a power-law fluid under gravity. The fluid flows through a porous medium. The asymptotic expansion is employed to obtain solution of the nonlinear problem. The results show the existence of traveling waves. It is assumed that the ...

  5. Gravity's shadow the search for gravitational waves

    CERN Document Server

    Collins, Harry

    2004-01-01

    According to the theory of relativity, we are constantly bathed in gravitational radiation. When stars explode or collide, a portion of their mass becomes energy that disturbs the very fabric of the space-time continuum like ripples in a pond. But proving the existence of these waves has been difficult; the cosmic shudders are so weak that only the most sensitive instruments can be expected to observe them directly. Fifteen times during the last thirty years scientists have claimed to have detected gravitational waves, but so far none of those claims have survived the scrutiny of the scie

  6. Testing strong gravity with gravitational waves and Love numbers

    International Nuclear Information System (INIS)

    Franzin, E; Cardoso, V; Raposo, G; Pani, P

    2017-01-01

    The LIGO observation of GW150914 has inaugurated the gravitational-wave astronomy era and the possibility of testing gravity in extreme regimes. While distorted black holes are the most convincing sources of gravitational waves, similar signals might be produced also by other compact objects. In particular, we discuss what the gravitational-wave ringdown could tell us about the nature of the emitting object, and how measurements of the tidal Love numbers could help us in understanding the internal structure of compact dark objects. (paper)

  7. The Binary Pulsar: Gravity Waves Exist.

    Science.gov (United States)

    Will, Clifford

    1987-01-01

    Reviews the history of pulsars generally and the 1974 discovery of the binary pulsar by Joe Taylor and Russell Hulse specifically. Details the data collection and analysis used by Taylor and Hulse. Uses this discussion as support for Albert Einstein's theory of gravitational waves. (CW)

  8. A perturbative solution for gravitational waves in quadratic gravity

    International Nuclear Information System (INIS)

    Neto, Edgard C de Rey; Aguiar, Odylio D; Araujo, Jose C N de

    2003-01-01

    We find a gravitational wave solution to the linearized version of quadratic gravity by adding successive perturbations to Einstein's linearized field equations. We show that only the Ricci-squared quadratic invariant contributes to give a different solution to those found in Einstein's general relativity. The perturbative solution is written as a power series in the β parameter, the coefficient of the Ricci-squared term in the quadratic gravitational action. We also show that, for monochromatic waves of a given angular frequency ω, the perturbative solution can be summed out to give an exact solution to the linearized version of quadratic gravity, for 0 1/2 . This result may lead to implications for the predictions for gravitational wave backgrounds of cosmological origin

  9. Upper atmospheric gravity wave details revealed in nightglow satellite imagery

    Science.gov (United States)

    Miller, Steven D.; Straka, William C.; Yue, Jia; Smith, Steven M.; Alexander, M. Joan; Hoffmann, Lars; Setvák, Martin; Partain, Philip T.

    2015-01-01

    Gravity waves (disturbances to the density structure of the atmosphere whose restoring forces are gravity and buoyancy) comprise the principal form of energy exchange between the lower and upper atmosphere. Wave breaking drives the mean upper atmospheric circulation, determining boundary conditions to stratospheric processes, which in turn influence tropospheric weather and climate patterns on various spatial and temporal scales. Despite their recognized importance, very little is known about upper-level gravity wave characteristics. The knowledge gap is mainly due to lack of global, high-resolution observations from currently available satellite observing systems. Consequently, representations of wave-related processes in global models are crude, highly parameterized, and poorly constrained, limiting the description of various processes influenced by them. Here we highlight, through a series of examples, the unanticipated ability of the Day/Night Band (DNB) on the NOAA/NASA Suomi National Polar-orbiting Partnership environmental satellite to resolve gravity structures near the mesopause via nightglow emissions at unprecedented subkilometric detail. On moonless nights, the Day/Night Band observations provide all-weather viewing of waves as they modulate the nightglow layer located near the mesopause (∼90 km above mean sea level). These waves are launched by a variety of physical mechanisms, ranging from orography to convection, intensifying fronts, and even seismic and volcanic events. Cross-referencing the Day/Night Band imagery with conventional thermal infrared imagery also available helps to discern nightglow structures and in some cases to attribute their sources. The capability stands to advance our basic understanding of a critical yet poorly constrained driver of the atmospheric circulation. PMID:26630004

  10. Experimental investigation of gravity wave turbulence and of non-linear four wave interactions..

    Science.gov (United States)

    Berhanu, Michael

    2017-04-01

    Using the large basins of the Ecole Centrale de Nantes (France), non-linear interactions of gravity surface waves are experimentally investigated. In a first part we study statistical properties of a random wave field regarding the insights from the Wave Turbulence Theory. In particular freely decaying gravity wave turbulence is generated in a closed basin. No self-similar decay of the spectrum is observed, whereas its Fourier modes decay first as a time power law due to nonl-inear mechanisms, and then exponentially due to linear viscous damping. We estimate the linear, non-linear and dissipative time scales to test the time scale separation. By estimation of the mean energy flux from the initial decay of wave energy, the Kolmogorov-Zakharov constant of the weak turbulence theory is evaluated. In a second part, resonant interactions of oblique surface gravity waves in a large basin are studied. We generate two oblique waves crossing at an acute angle. These mother waves mutually interact and give birth to a resonant wave whose properties (growth rate, resonant response curve and phase locking) are fully characterized. All our experimental results are found in good quantitative agreement with four-wave interaction theory. L. Deike, B. Miquel, P. Gutiérrez, T. Jamin, B. Semin, M. Berhanu, E. Falcon and F. Bonnefoy, Role of the basin boundary conditions in gravity wave turbulence, Journal of Fluid Mechanics 781, 196 (2015) F. Bonnefoy, F. Haudin, G. Michel, B. Semin, T. Humbert, S. Aumaître, M. Berhanu and E. Falcon, Observation of resonant interactions among surface gravity waves, Journal of Fluid Mechanics (Rapids) 805, R3 (2016)

  11. A coupling modulation model of capillary waves from gravity waves: Theoretical analysis and experimental validation

    Science.gov (United States)

    Chen, Pengzhen; Wang, Xiaoqing; Liu, Li; Chong, Jinsong

    2016-06-01

    According to Bragg theory, capillary waves are the predominant scatterers of high-frequency band (such as Ka-band) microwave radiation from the surface of the ocean. Therefore, understanding the modulation mechanism of capillary waves is an important foundation for interpreting high-frequency microwave remote sensing images of the surface of the sea. In our experiments, we discovered that modulations of capillary waves are significantly larger than the values predicted by the classical theory. Further, analysis shows that the difference in restoring force results in an inflection point while the phase velocity changes from gravity waves region to capillary waves region, and this results in the capillary waves being able to resonate with gravity waves when the phase velocity of the gravity waves is equal to the group velocity of the capillary waves. Consequently, we propose a coupling modulation model in which the current modulates the capillary wave indirectly by modulating the resonant gravity waves, and the modulation of the former is approximated by that of the latter. This model very effectively explains the results discovered in our experiments. Further, based on Bragg scattering theory and this coupling modulation model, we simulate the modulation of normalized radar cross section (NRCS) of typical internal waves and show that the high-frequency bands are superior to the low-frequency bands because of their greater modulation of NRCS and better radiometric resolution. This result provides new support for choice of radar band for observation of wave-current modulation oceanic phenomena such as internal waves, fronts, and shears.

  12. Spontaneous development of rotating inertial gravity wave inside the cylindrical tank with combined in- and outflow

    Czech Academy of Sciences Publication Activity Database

    Fedorchenko, Alexander I.; Stachiv, Ivo; Trávníček, Zdeněk

    2013-01-01

    Roč. 20, č. 2 (2013), s. 133-138 ISSN 0869-8643 R&D Projects: GA ČR GAP107/10/0824; GA ČR(CZ) GCP101/11/J019 Institutional research plan: CEZ:AV0Z20760514 Keywords : inertial gravity wave * free surface * rotating flow Subject RIV: BK - Fluid Dynamics Impact factor: 0.295, year: 2013 http://link.springer.com/article/10.1134/S0869864313020017

  13. Interaction between ionization and gravity waves in the upper atmosphere

    International Nuclear Information System (INIS)

    Balcioglu, O.

    1982-10-01

    It is known that travelling ionospheric disturbances are produced by gravity waves. During their movement from the F region downwards to the E region, gravity waves can produce thin layers called transients on ionograms and, if the wave motion persists, 'h-type Esub(S) can be produced. To investigate the problem, the continuity equations for both the E and F regions are solved for a perturbation, the motion of which is taken to be a gravity wave. Hitherto, N'/N 0 , the ratio of the disturbed to the undisturbed electron density, has been calculated by using only the Hall conductivity and ignoring the diffusion term for the F region. In the present calculations we have used Pedersan and Hall conductivities and calculated the N'/N 0 ratio for both the E and F regions. Using CIRA standard atmosphere data we find for the F region that N' can exceed N 0 by up to 4 percent, depending on the horizontal wind velocity. In the E region, N' reaches much higher values than in the F region. Thus at 120 km if we take a typical horizontal wind velocity of 80 m/sec (wavelength 150 km), N' is about twice as large as N 0 . From these results we see that the diffusion term is important for the E region. (author)

  14. Stratospheric gravity wave activities inferred through the GPS radio occultation technique

    International Nuclear Information System (INIS)

    Wrasse, Cristiano Max; Takahashi, Hisao; Fechine, Joaquim; Denardini, Clezio Marcos; Wickert, Jens

    2007-01-01

    Stratospheric gravity wave activities were deduced from GPS radio occultation temperature profiles obtained by CHAMP satellite between 2001 and 2005. Potential energy profiles are used to analyze the gravity wave activity over South America. The results showed an inter-annual variation of the potential energy integrated between 24 and 34 km of altitude. The gravity wave activity is more concentrated around the equatorial region. In order to evaluate the seasonal variation of the gravity wave activity, a mean potential energy was determined over (10 deg N-10 deg S) and (100 deg W-20 deg W). The results showed a lower gravity wave activity during winter time, while during spring time the mean potential energy showed an increase in the wave activity. The results of the mean potential energy also showed that the gravity wave activity in the lower stratosphere exhibits a higher wave activity during 2002 and 2004 and a lower wave activity during 2003 and 2005. (author)

  15. An evaluation of gravity waves and gravity wave sources in the Southern Hemisphere in a 7 km global climate simulation.

    Science.gov (United States)

    Holt, L A; Alexander, M J; Coy, L; Liu, C; Molod, A; Putman, W; Pawson, S

    2017-07-01

    In this study, gravity waves (GWs) in the high-resolution GEOS-5 Nature Run are first evaluated with respect to satellite and other model results. Southern Hemisphere winter sources of non-orographic GWs in the model are then investigated by linking measures of tropospheric non-orographic gravity wave generation tied to precipitation and frontogenesis with absolute gravity wave momentum flux in the lower stratosphere. Finally, non-orographic GW momentum flux is compared to orographic gravity wave momentum flux and compared to previous estimates. The results show that the global patterns in GW amplitude, horizontal wavelength, and propagation direction are realistic compared to observations. However, as in other global models, the amplitudes are weaker and horizontal wavelengths longer than observed. The global patterns in absolute GW momentum flux also agree well with previous model and observational estimates. The evaluation of model non-orographic GW sources in the Southern Hemisphere winter shows that strong intermittent precipitation (greater than 10 mm h -1 ) is associated with GW momentum flux over the South Pacific, whereas frontogenesis and less intermittent, lower precipitation rates (less than 10 mm h -1 ) are associated with GW momentum flux near 60°S. In the model, orographic GWs contribute almost exclusively to a peak in zonal mean momentum flux between 70 and 75°S, while non-orographic waves dominate at 60°S, and non-orographic GWs contribute a third to a peak in zonal mean momentum flux between 25 and 30°S.

  16. Issues concerning gravity waves from first-order phase transitions

    International Nuclear Information System (INIS)

    Kosowsky, A.

    1993-01-01

    The stochastic background of gravitational radiation is a unique and potentially valuable source of information about the early universe. Photons thermally decoupled when the universe was around 100,000 years old; electromagnetic radiation cannot directly provide information about the epoch earlier than this. In contrast, gravitons presumably decoupled around the Planck time, when the universe was only 10 -44 seconds old. Since gravity wave propagate virtually unimpeded, any energetic event in the evolution of the universe will leave an imprint on the gravity wave background. Turner and Wilczek first suggested that first-order phase transitions, and particularly transitions which occur via the nucleation, expansion, and percolation of vacuum bubbles, will be a particularly efficient source of gravitational radiation. Detailed calculations with scalar-field vacuum bubbles confirm this conjecture and show that strongly first-order phase transitions are probably the strongest stochastic gravity-wave source yet conjectured. In this work the author first reviews the vacuum bubble calculations, stressing their physical assumptions. The author then discusses realistic scenarios for first-order phase transitions and describes how the calculations must be modified and extended to produce reliable results. 11 refs

  17. Breeze Gravity Current in a Uniform Flow of Air

    Directory of Open Access Journals (Sweden)

    M.V. Shokurov

    2017-02-01

    Full Text Available Breeze circulation is often observed nearby the water basin coasts and usually accompanied by a background synoptic wind. One of the basic dynamically important components of the breeze circulation is gravity current. In the present paper the latter is used as the breeze simplified model. The theory of interaction of gravity current and a uniform synoptic wind are developed. The gravity current in the domain of infinite height in a stationary environment and environment with background flow was considered. To solve this problem the law of conservation of mass and universal property of the Froude number was used, which is true in the steady state. It is shown that increase of a tail-wind is followed by growth of the gravity current velocity and decrease of its height. The opposite situation is observed at increase of a head wind: the current velocity reduces and its height increases. Using a Taylor series expansion for small values of the background flow velocity a linear dependence of gravity current velocity on background flow velocity can be obtained. The factor determining the slope of the velocity of gravity current propagation on the background wind speed, which is equal 2/3, is a universal constant. The theory explains the results of numerical simulation previously obtained by numerous authors. A physical interpretation of dependence of the height and velocity of the gravity current on the background flow velocity is presented.

  18. On the unstable mode merging of gravity-inertial waves with Rossby waves

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2011-08-01

    Full Text Available We recapitulate the results of the combined theory of gravity-inertial-Rossby waves in a rotating, stratified atmosphere. The system is shown to exhibit a "local" (JWKB instability whenever the phase speed of the low-frequency-long wavelength westward propagating Rossby wave exceeds the phase speed ("Kelvin" speed of the high frequency-short wavelength gravity-inertial wave. This condition ensures that mode merging, leading to instability, takes place in some intermediate band of frequencies and wave numbers. The contention that such an instability is "spurious" is not convincing. The energy source of the instability resides in the background enthalpy which can be released by the action of the gravitational buoyancy force, through the combined wave modes.

  19. Propagation and Breaking at High Altitudes of Gravity Waves Excited by Tropospheric Forcing

    Science.gov (United States)

    Prusa, Joseph M.; Smolarkiewicz, Piotr K.; Garcia, Rolando R.

    1996-01-01

    An anelastic approximation is used with a time-variable coordinate transformation to formulate a two-dimensional numerical model that describes the evolution of gravity waves. The model is solved using a semi-Lagrangian method with monotone (nonoscillatory) interpolation of all advected fields. The time-variable transformation is used to generate disturbances at the lower boundary that approximate the effect of a traveling line of thunderstorms (a squall line) or of flow over a broad topographic obstacle. The vertical propagation and breaking of the gravity wave field (under conditions typical of summer solstice) is illustrated for each of these cases. It is shown that the wave field at high altitudes is dominated by a single horizontal wavelength; which is not always related simply to the horizontal dimension of the source. The morphology of wave breaking depends on the horizontal wavelength; for sufficiently short waves, breaking involves roughly one half of the wavelength. In common with other studies, it is found that the breaking waves undergo "self-acceleration," such that the zonal-mean intrinsic frequency remains approximately constant in spite of large changes in the background wind. It is also shown that many of the features obtained in the calculations can be understood in terms of linear wave theory. In particular, linear theory provides insights into the wavelength of the waves that break at high altitudes, the onset and evolution of breaking. the horizontal extent of the breaking region and its position relative to the forcing, and the minimum and maximum altitudes where breaking occurs. Wave breaking ceases at the altitude where the background dissipation rate (which in our model is a proxy for molecular diffusion) becomes greater than the rate of dissipation due to wave breaking, This altitude, in effect, the model turbopause, is shown to depend on a relatively small number of parameters that characterize the waves and the background state.

  20. ANALYTICAL SOLUTION FOR WAVES IN PLANETS WITH ATMOSPHERIC SUPERROTATION. I. ACOUSTIC AND INERTIA-GRAVITY WAVES

    Energy Technology Data Exchange (ETDEWEB)

    Peralta, J.; López-Valverde, M. A. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Imamura, T. [Institute of Space and Astronautical Science-Japan Aerospace Exploration Agency 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Read, P. L. [Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford (United Kingdom); Luz, D. [Centro de Astronomia e Astrofísica da Universidade de Lisboa (CAAUL), Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa (Portugal); Piccialli, A., E-mail: peralta@iaa.es [LATMOS, UVSQ, 11 bd dAlembert, 78280 Guyancourt (France)

    2014-07-01

    This paper is the first of a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases when the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this first part, only waves that are direct solutions of the generic dispersion relation are studied—acoustic and inertia-gravity waves. Concerning inertia-gravity waves, we found that in the cases of short horizontal wavelengths, null background wind, or propagation in the equatorial region, only pure gravity waves are possible, while for the limit of large horizontal wavelengths and/or null static stability, the waves are inertial. The correspondence between classical atmospheric approximations and wave filtering has been examined too, and we carried out a classification of the mesoscale waves found in the clouds of Venus at different vertical levels of its atmosphere. Finally, the classification of waves in exoplanets is discussed and we provide a list of possible candidates with cyclostrophic regimes.

  1. Statistical analysis of thermospheric gravity waves from Fabry-Perot Interferometer measurements of atomic oxygen

    Directory of Open Access Journals (Sweden)

    E. A. K. Ford

    2008-02-01

    . This gives a clear indication of the direction of flow of the gravity waves, and corroborates that the source is the auroral oval. This is because the energy is dissipated through heating in each cycle of a wave, therefore, over a given distance, short period waves lose more energy than long and dissipate before they reach their target.

  2. On the Chemical Mixing Induced by Internal Gravity Waves

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, T. M. [School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne (United Kingdom); McElwaine, J. N. [Planetary Science Institute, Tucson, AZ 85721 (United States)

    2017-10-10

    Detailed modeling of stellar evolution requires a better understanding of the (magneto)hydrodynamic processes that mix chemical elements and transport angular momentum. Understanding these processes is crucial if we are to accurately interpret observations of chemical abundance anomalies, surface rotation measurements, and asteroseismic data. Here, we use two-dimensional hydrodynamic simulations of the generation and propagation of internal gravity waves in an intermediate-mass star to measure the chemical mixing induced by these waves. We show that such mixing can generally be treated as a diffusive process. We then show that the local diffusion coefficient does not depend on the local fluid velocity, but rather on the wave amplitude. We then use these findings to provide a simple parameterization for this diffusion, which can be incorporated into stellar evolution codes and tested against observations.

  3. Sensitivity of Gravity Wave Fluxes to Interannual Variations in Tropical Convection and Zonal Wind.

    Science.gov (United States)

    Alexander, M Joan; Ortland, David A; Grimsdell, Alison W; Kim, Ji-Eun

    2017-09-01

    Using an idealized model framework with high-frequency tropical latent heating variability derived from global satellite observations of precipitation and clouds, the authors examine the properties and effects of gravity waves in the lower stratosphere, contrasting conditions in an El Niño year and a La Niña year. The model generates a broad spectrum of tropical waves including planetary-scale waves through mesoscale gravity waves. The authors compare modeled monthly mean regional variations in wind and temperature with reanalyses and validate the modeled gravity waves using satellite- and balloon-based estimates of gravity wave momentum flux. Some interesting changes in the gravity spectrum of momentum flux are found in the model, which are discussed in terms of the interannual variations in clouds, precipitation, and large-scale winds. While regional variations in clouds, precipitation, and winds are dramatic, the mean gravity wave zonal momentum fluxes entering the stratosphere differ by only 11%. The modeled intermittency in gravity wave momentum flux is shown to be very realistic compared to observations, and the largest-amplitude waves are related to significant gravity wave drag forces in the lowermost stratosphere. This strong intermittency is generally absent or weak in climate models because of deficiencies in parameterizations of gravity wave intermittency. These results suggest a way forward to improve model representations of the lowermost stratospheric quasi-biennial oscillation winds and teleconnections.

  4. Atmospheric gravity waves in the Red Sea: a new hotspot

    KAUST Repository

    Magalhaes, J. M.

    2011-02-03

    The region of the Middle East around the Red Sea (between 32° E and 44° E longitude and 12° N and 28° N latitude) is a currently undocumented hotspot for atmospheric gravity waves (AGWs). Satellite imagery shows evidence that this region is prone to relatively high occurrence of AGWs compared to other areas in the world, and reveals the spatial characteristics of these waves. The favorable conditions for wave propagation in this region are illustrated with three typical cases of AGWs propagating in the lower troposphere over the sea. Using weakly nonlinear long wave theory and the observed characteristic wavelengths we obtain phase speeds which are consistent with those observed and typical for AGWs, with the Korteweg-de Vries theory performing slightly better than Benjamin-Davis-Acrivos-Ono theory as far as phase speeds are concerned. ERS-SAR and Envisat-ASAR satellite data analysis between 1993 and 2008 reveals signatures consistent with horizontally propagating large-scale internal waves. These signatures cover the entire Red Sea and are more frequently observed between April and September, although they also occur during the rest of the year. The region\\'s (seasonal) propagation conditions for AGWs, based upon average vertical atmospheric stratification profiles suggest that many of the signatures identified in the satellite images are atmospheric internal waves. © Author(s) 2011.

  5. Gravity wave vertical energy flux at 95 km

    Science.gov (United States)

    Jacob, P. G.; Jacka, F.

    1985-01-01

    A three-field photometer (3FP) located at Mt. Torrens near Adelaide, is capable of monitoring different airglow emissions from three spaced fields in the sky. A wheel containing up to six different narrow bandpass interference filters can be rotated, allowing each of the filters to be sequentially placed into each of the three fields. The airglow emission of interest is the 557.7 nm line which has an intensity maximum at 95 km. Each circular field of view is located at the apexes of an equilateral triangle centered on zenith with diameters of 5 km and field separations of 13 km when projected to the 95-km level. The sampling period was 30 seconds and typical data lengths were between 7 and 8 hours. The analysis and results from the interaction of gravity waves on the 557.7 nm emission layer are derived using an atmospheric model similar to that proposed by Hines (1960) where the atmosphere is assumed isothermal and perturbations caused by gravity waves are small and adiabatic, therefore, resulting in linearized equations of motion. In the absence of waves, the atmosphere is also considered stationary. Thirteen nights of quality data from January 1983 to October 1984, covering all seasons, are used in this analysis.

  6. Gravity wave influence on NLC: experimental results from ALOMAR, 69° N

    Directory of Open Access Journals (Sweden)

    H. Wilms

    2013-12-01

    Full Text Available The influence of gravity waves on noctilucent clouds (NLC at ALOMAR (69° N is analysed by relating gravity wave activity to NLC occurrence from common-volume measurements. Gravity wave kinetic energies are derived from MF-radar wind data and filtered into different period ranges by wavelet transformation. From the dataset covering the years 1999–2011, a direct correlation between gravity wave kinetic energy and NLC occurrence is not found, i.e., NLC appear independently of the simultaneously measured gravity wave kinetic energy. In addition, gravity wave activity is divided into weak and strong activity as compared to a 13 yr mean. The NLC occurrence rates during strong and weak activity are calculated separately for a given wave period and compared to each other. Again, for the full dataset no dependence of NLC occurrence on relative gravity wave activity is found. However, concentrating on 12 h of NLC detections during 2008, we do find an NLC-amplification with strong long-period gravity wave occurrence. Our analysis hence confirms previous findings that in general NLC at ALOMAR are not predominantly driven by gravity waves while exceptions to this rule are at least possible.

  7. An Estimation of Wave Attenuation Factor in Ultrasonic Assisted Gravity Drainage Process

    Directory of Open Access Journals (Sweden)

    Behnam Keshavarzi

    2014-01-01

    Full Text Available It has been proved that ultrasonic energy can considerably increase the amount of oil recovery in an immiscible displacement process. Although many studies have been performed on investigating the roles of ultrasonic waves, based on the best of our knowledge, little attention has been paid to evaluate wave attenuation parameter, which is an important parameter in the determination of the energy delivered to the porous medium. In this study, free fall gravity drainage process is investigated in a glass bead porous medium. Kerosene and Dorud crude oil are used as the wetting phases and air is used as the non-wetting phase. A piston-like displacement model with considering constant capillary pressure and applying Corey type approximation for relative permeabilities of both wetting and nonwetting phases is applied. A pressure term is considered to describe the presence of ultrasonic waves and the attenuation factor of ultrasonic waves is calculated by evaluating the value of external pressure applied to enhance the flow using the history matching of the data in the presence and absence of ultrasonic waves. The results introduce the attenuation factor as an important parameter in the process of ultrasonic assisted gravity drainage. The results show that only a low percentage of the ultrasonic energy (5.8% for Dorud crude oil and 3.3% for kerosene is delivered to the flow of the fluid; however, a high increase in oil recovery enhancement (15% for Dorud crude oil and 12% for Kerosene is observed in the experiments. This proves that the ultrasonic waves, even when the contribution is not substantial, can be a significantly efficient method for flow enhancement.

  8. Large-scale dynamical influence of a gravity wave generated over the Antarctic Peninsula – regional modelling and budget analysis

    Directory of Open Access Journals (Sweden)

    JOEL Arnault

    2013-03-01

    Full Text Available The case study of a mountain wave triggered by the Antarctic Peninsula on 6 October 2005, which has already been documented in the literature, is chosen here to quantify the associated gravity wave forcing on the large-scale flow, with a budget analysis of the horizontal wind components and horizontal kinetic energy. In particular, a numerical simulation using the Weather Research and Forecasting (WRF model is compared to a control simulation with flat orography to separate the contribution of the mountain wave from that of other synoptic processes of non-orographic origin. The so-called differential budgets of horizontal wind components and horizontal kinetic energy (after subtracting the results from the simulation without orography are then averaged horizontally and vertically in the inner domain of the simulation to quantify the mountain wave dynamical influence at this scale. This allows for a quantitative analysis of the simulated mountain wave's dynamical influence, including the orographically induced pressure drag, the counterbalancing wave-induced vertical transport of momentum from the flow aloft, the momentum and energy exchanges with the outer flow at the lateral and upper boundaries, the effect of turbulent mixing, the dynamics associated with geostrophic re-adjustment of the inner flow, the deceleration of the inner flow, the secondary generation of an inertia–gravity wave and the so-called baroclinic conversion of energy between potential energy and kinetic energy.

  9. On The Implications of Atmospheric Gravity Waves on Wind Power

    OpenAIRE

    Norris, Luke

    2011-01-01

    In view of the rapidly rising cost of fossil fuels and concerns over climate change, there can be little doubt that renewable energy is to play a large role in the future of our economic development. The impact of Atmospheric Gravity Waves (AGWs) on wind power is, at best, unclear. In this research, AGWs are successfully modelled both in theoretical and real world environments using the WindSim software package which has revealed a potential 7.4% drop in annual power output as a direct ...

  10. Can gravity waves significantly impact PSC occurrence in the Antarctic?

    Directory of Open Access Journals (Sweden)

    R. M. Woollands

    2009-11-01

    Full Text Available A combination of POAM III aerosol extinction and CHAMP RO temperature measurements are used to examine the role of atmospheric gravity waves in the formation of Antarctic Polar Stratospheric Clouds (PSCs. POAM III aerosol extinction observations and quality flag information are used to identify Polar Stratospheric Clouds using an unsupervised clustering algorithm.

    A PSC proxy, derived by thresholding Met Office temperature analyses with the PSC Type Ia formation temperature (TNAT, shows general agreement with the results of the POAM III analysis. However, in June the POAM III observations of PSC are more abundant than expected from temperature threshold crossings in five out of the eight years examined. In addition, September and October PSC identified using temperature thresholding is often significantly higher than that derived from POAM III; this observation probably being due to dehydration and denitrification. Comparison of the Met Office temperature analyses with corresponding CHAMP observations also suggests a small warm bias in the Met Office data in June. However, this bias cannot fully explain the differences observed.

    Analysis of CHAMP data indicates that temperature perturbations associated with gravity waves may partially explain the enhanced PSC incidence observed in June (relative to the Met Office analyses. For this month, approximately 40% of the temperature threshold crossings observed using CHAMP RO data are associated with small-scale perturbations. Examination of the distribution of temperatures relative to TNAT shows a large proportion of June data to be close to this threshold, potentially enhancing the importance of gravity wave induced temperature perturbations. Inspection of the longitudinal structure of PSC occurrence in June 2005 also shows that regions of enhancement are geographically associated with the Antarctic Peninsula; a known mountain wave "hotspot". The

  11. Transition from geostrophic turbulence to inertia–gravity waves in the atmospheric energy spectrum

    Science.gov (United States)

    Callies, Jörn; Ferrari, Raffaele; Bühler, Oliver

    2014-01-01

    Midlatitude fluctuations of the atmospheric winds on scales of thousands of kilometers, the most energetic of such fluctuations, are strongly constrained by the Earth’s rotation and the atmosphere’s stratification. As a result of these constraints, the flow is quasi-2D and energy is trapped at large scales—nonlinear turbulent interactions transfer energy to larger scales, but not to smaller scales. Aircraft observations of wind and temperature near the tropopause indicate that fluctuations at horizontal scales smaller than about 500 km are more energetic than expected from these quasi-2D dynamics. We present an analysis of the observations that indicates that these smaller-scale motions are due to approximately linear inertia–gravity waves, contrary to recent claims that these scales are strongly turbulent. Specifically, the aircraft velocity and temperature measurements are separated into two components: one due to the quasi-2D dynamics and one due to linear inertia–gravity waves. Quasi-2D dynamics dominate at scales larger than 500 km; inertia–gravity waves dominate at scales smaller than 500 km. PMID:25404349

  12. Transition from geostrophic turbulence to inertia-gravity waves in the atmospheric energy spectrum.

    Science.gov (United States)

    Callies, Jörn; Ferrari, Raffaele; Bühler, Oliver

    2014-12-02

    Midlatitude fluctuations of the atmospheric winds on scales of thousands of kilometers, the most energetic of such fluctuations, are strongly constrained by the Earth's rotation and the atmosphere's stratification. As a result of these constraints, the flow is quasi-2D and energy is trapped at large scales—nonlinear turbulent interactions transfer energy to larger scales, but not to smaller scales. Aircraft observations of wind and temperature near the tropopause indicate that fluctuations at horizontal scales smaller than about 500 km are more energetic than expected from these quasi-2D dynamics. We present an analysis of the observations that indicates that these smaller-scale motions are due to approximately linear inertia-gravity waves, contrary to recent claims that these scales are strongly turbulent. Specifically, the aircraft velocity and temperature measurements are separated into two components: one due to the quasi-2D dynamics and one due to linear inertia-gravity waves. Quasi-2D dynamics dominate at scales larger than 500 km; inertia-gravity waves dominate at scales smaller than 500 km.

  13. Capillary-gravity waves and the Navier-Stokes equation

    International Nuclear Information System (INIS)

    Behroozi, F.; Podolefsky, N.

    2001-01-01

    Water waves are a source of great fascination for undergraduates and thus provide an excellent context for introducing some important topics in fluid dynamics. In this paper we introduce the potential theory for incompressible and inviscid flow and derive the differential equation that governs the behaviour of the velocity potential. Next we obtain the harmonic solutions of the velocity potential by a very general argument. These solutions in turn yield the equations for the velocity and displacement of a water element under the action of a harmonic wave. Finally we obtain the dispersion relation for surface waves by requiring that the harmonic solutions satisfy the Navier-Stokes equation. (author)

  14. Atmosphere-ionosphere coupling from convectively generated gravity waves

    Science.gov (United States)

    Azeem, Irfan; Barlage, Michael

    2018-04-01

    Ionospheric variability impacts operational performances of a variety of technological systems, such as HF communication, Global Positioning System (GPS) navigation, and radar surveillance. The ionosphere is not only perturbed by geomagnetic inputs but is also influenced by atmospheric tides and other wave disturbances propagating from the troposphere to high altitudes. Atmospheric Gravity Waves (AGWs) excited by meteorological sources are one of the largest sources of mesoscale variability in the ionosphere. In this paper, Total Electron Content (TEC) data from networks of GPS receivers in the United States are analyzed to investigate AGWs in the ionosphere generated by convective thunderstorms. Two case studies of convectively generated gravity waves are presented. On April 4, 2014 two distinct large convective systems in Texas and Arkansas generated two sets of concentric AGWs that were observed in the ionosphere as Traveling Ionospheric Disturbances (TIDs). The period of the observed TIDs was 20.8 min, the horizontal wavelength was 182.4 km, and the horizontal phase speed was 146.4 m/s. The second case study shows TIDs generated from an extended squall line on December 23, 2015 stretching from the Gulf of Mexico to the Great Lakes in North America. Unlike the concentric wave features seen in the first case study, the extended squall line generated TIDs, which exhibited almost plane-parallel phase fronts. The TID period was 20.1 min, its horizontal wavelength was 209.6 km, and the horizontal phase speed was 180.1 m/s. The AGWs generated by both of these meteorological events have large vertical wavelength (>100 km), which are larger than the F2 layer thickness, thus allowing them to be discernible in the TEC dataset.

  15. Astrophysical flows near [Formula: see text] gravity black holes.

    Science.gov (United States)

    Ahmed, Ayyesha K; Azreg-Aïnou, Mustapha; Bahamonde, Sebastian; Capozziello, Salvatore; Jamil, Mubasher

    In this paper, we study the accretion process for fluids flowing near a black hole in the context of f ( T ) teleparallel gravity. Specifically, by performing a dynamical analysis by a Hamiltonian system, we are able to find the sonic points. After that, we consider different isothermal test fluids in order to study the accretion process when they are falling onto the black hole. We find that these flows can be classified according to the equation of state and the black hole features. Results are compared in f ( T ) and f ( R ) gravity.

  16. Astrophysical flows near f(T) gravity black holes

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Ayyesha K.; Jamil, Mubasher [National University of Sciences and Technology (NUST), Department of Mathematics, School of Natural Sciences (SNS), Islamabad (Pakistan); Azreg-Ainou, Mustapha [Baskent University, Baglica Campus, Engineering Faculty, Ankara (Turkey); Bahamonde, Sebastian [University College London, Department of Mathematics, London (United Kingdom); Capozziello, Salvatore [Universita di Napoli ' ' Federico II' ' , Dipartimento di Fisica, Naples (Italy); Gran Sasso Science Institute (INFN), L' Aquila (Italy); INFN Sezione di Napoli, Naples (Italy)

    2016-05-15

    In this paper, we study the accretion process for fluids flowing near a black hole in the context of f(T) teleparallel gravity. Specifically, by performing a dynamical analysis by a Hamiltonian system, we are able to find the sonic points. After that, we consider different isothermal test fluids in order to study the accretion process when they are falling onto the black hole. We find that these flows can be classified according to the equation of state and the black hole features. Results are compared in f(T) and f(R) gravity. (orig.)

  17. Exact RG flow equations and quantum gravity

    Science.gov (United States)

    de Alwis, S. P.

    2018-03-01

    We discuss the different forms of the functional RG equation and their relation to each other. In particular we suggest a generalized background field version that is close in spirit to the Polchinski equation as an alternative to the Wetterich equation to study Weinberg's asymptotic safety program for defining quantum gravity, and argue that the former is better suited for this purpose. Using the heat kernel expansion and proper time regularization we find evidence in support of this program in agreement with previous work.

  18. Gravitational wave echoes from macroscopic quantum gravity effects

    Energy Technology Data Exchange (ETDEWEB)

    Barceló, Carlos [Instituto de Astrofísica de Andalucía (IAA-CSIC),Glorieta de la Astronomía, 18008 Granada (Spain); Carballo-Rubio, Raúl [The Cosmology & Gravity Group and the Laboratory for Quantum Gravity & Strings,Department of Mathematics & Applied Mathematics, University of Cape Town,Private Bag, Rondebosch 7701 (South Africa); Garay, Luis J. [Departamento de Física Teórica II,Universidad Complutense de Madrid, 28040 Madrid (Spain); Instituto de Estructura de la Materia (IEM-CSIC),Serrano 121, 28006 Madrid (Spain)

    2017-05-10

    New theoretical approaches developed in the last years predict that macroscopic quantum gravity effects in black holes should lead to modifications of the gravitational wave signals expected in the framework of classical general relativity, with these modifications being characterized in certain scenarios by the existence of dampened repetitions of the primary signal. Here we use the fact that non-perturbative corrections to the near-horizon external geometry of black holes are necessary for these modifications to exist, in order to classify different proposals and paradigms with respect to this criterion and study in a neat and systematic way their phenomenology. Proposals that lead naturally to the existence of echoes in the late-time ringdown of gravitational wave signals from black hole mergers must share the replacement of black holes by horizonless configurations with a physical surface showing reflective properties in the relevant range of frequencies. On the other hand, proposals or paradigms that restrict quantum gravity effects on the external geometry to be perturbative, such as black hole complementarity or the closely related firewall proposal, do not display echoes. For the sake of completeness we exploit the interplay between the timescales associated with the formation of firewalls and the mechanism behind the existence of echoes in order to conclude that even unconventional distortions of the firewall concept (such as naked firewalls) do not lead to this phenomenon.

  19. Virtual Seafloor Reduces Internal Wave Generation by Tidal Flow

    Science.gov (United States)

    Zhang, Likun; Swinney, Harry L.

    2014-03-01

    Our numerical simulations of tidal flow of a stratified fluid over periodic knife-edge ridges and random topography reveal that the time-averaged tidal energy converted into internal gravity wave radiation arises only from the section of a ridge above a virtual seafloor. The average radiated power is approximated by the power predicted by linear theory if the height of the ridge is measured relative to the virtual floor. The concept of a virtual floor can extend the applicability of linear theory to global predictions of the conversion of tidal energy into internal wave energy in the oceans.

  20. Modulation of Precipitation in the Olympic Mountains by Trapped Gravity Waves

    Science.gov (United States)

    Heymsfield, G. M.; Tian, L.; Grecu, M.; McLinden, M.; Li, L.

    2017-12-01

    Precipitation over the Olympic Mountains was studied intensely with multiple aircraft and ground-based measurements during the Olympic Mountains Experiment (OLYMPEX) during the fall-winter season 2015-2016 as part of validation for the Global Precipitation Mission (GPM) (Houze et al. 2017) and the Radar Definition Experiment (RADEX) supported by the Aerosol Chemistry, Ecosystem (ACE) NASA Decadal Mission. This presentation focuses on observations of a broad frontal cloud system with strong flow over the mountains on 5 December 2015. Unique observations of trapped waves were obtained with in the three Goddard Space Flight Center nadir-looking, X- through W-band, Doppler radars on the NASA high-altitude ER-2: the High-altitude Wind and Rain Airborne Profiler (HIWRAP) at Ku and Ka-band, the W-band Cloud Radar System (CRS), and the ER-2 X-band Radar (EXRAD). Analysis of the aircraft measurements showed the presence of deep, trapped gravity waves on a scale ranging from 10-25 km in the nadir-looking Doppler and reflectivity observations. These waves cause localized vertical up/down motions on the order of 1-2 ms-1 and they are superimposed on the widespread south-southwest flow over the Olympic Mountains. While much of this widespread flow over the mountains produces copious amounts of snowfall, the gravity waves play an important role in modulating this precipitation indirectly through microphysical processes in the ice region. We will describe analyses of the interactions between the air motions and precipitation structure for this case and other cases we observed similar waves. We will present preliminary results from precipitation retrievals based on optimal estimation (Grecu et al. 2011).

  1. The response of superpressure balloons to gravity wave motions

    Directory of Open Access Journals (Sweden)

    R. A. Vincent

    2014-04-01

    Full Text Available Superpressure balloons (SPB, which float on constant density (isopycnic surfaces, provide a unique way of measuring the properties of atmospheric gravity waves (GW as a function of wave intrinsic frequency. Here we devise a quasi-analytic method of investigating the SPB response to GW motions. It is shown that the results agree well with more rigorous numerical simulations of balloon motions and provide a better understanding of the response of SPB to GW, especially at high frequencies. The methodology is applied to ascertain the accuracy of GW studies using 12 m diameter SPB deployed in the 2010 Concordiasi campaign in the Antarctic. In comparison with the situation in earlier campaigns, the vertical displacements of the SPB were measured directly using GPS. It is shown using a large number of Monte Carlo-type simulations with realistic instrumental noise that important wave parameters, such as momentum flux, phase speed and wavelengths, can be retrieved with good accuracy from SPB observations for intrinsic wave periods greater than ca. 10 min. The noise floor for momentum flux is estimated to be ca. 10−4 mPa.

  2. Making waves: visualizing fluid flows

    NARCIS (Netherlands)

    Zweers, Wout; Zwart, Valerie; Bokhove, Onno

    2013-01-01

    We explore the visualization of violent wave dynamics and erosion by waves and jets in laser-cut reliefs, laser engravings, and three-dimensional printing. For this purpose we built table-top experiments to cast breaking waves, and also explored the creation of extreme or rogue waves in larger wave

  3. Characteristics of equatorial gravity waves derived from mesospheric airglow imaging observations

    Directory of Open Access Journals (Sweden)

    S. Suzuki

    2009-04-01

    Full Text Available We present the characteristics of small-scale (<100 km gravity waves in the equatorial mesopause region derived from OH airglow imaging observations at Kototabang (100.3° E, 0.2° S, Indonesia, from 2002 to 2005. We adopted a method that could automatically detect gravity waves in the airglow images using two-dimensional cross power spectra of gravity waves. The propagation directions of the waves were likely controlled by zonal filtering due to stratospheric mean winds that show a quasi-biennial oscillation (QBO and the presence of many wave sources in the troposphere.

  4. Two-phase flow and heat transfer under low gravity

    Science.gov (United States)

    Frost, W.

    1981-01-01

    Spacelab experiment to investigate two-phase flow patterns under gravity uses a water-air mixture experiment. Air and water are circulated through the system. The quality or the mixture or air-water is controlled. Photographs of the test section are made and at the same time pressure drop across the test section is measured. The data establishes a flow regime map under reduced gravity conditions with corresponding pressure drop correlations. The test section is also equipped with an electrical resistance heater in order to allow a flow boiling experiment to be carried out using Freon II. High-speed photographs of the test section are used to determine flow patterns. The temperature gradient and pressure drop along the duct can be measured. Thus, quality change can be measured, and heat transfer calculated.

  5. On the nonlinear shaping mechanism for gravity wave spectrum in the atmosphere

    Directory of Open Access Journals (Sweden)

    I. P. Chunchuzov

    2009-11-01

    Full Text Available The nonlinear mechanism of shaping of a high vertical wave number spectral tail in the field of a few discrete internal gravity waves in the atmosphere is studied in this paper. The effects of advection of fluid parcels by interacting gravity waves are taken strictly into account by calculating wave field in Lagrangian variables, and performing a variable transformation from Lagrangian to Eulerian frame. The vertical profiles and vertical wave number spectra of the Eulerian displacement field are obtained for both the case of resonant and non-resonant wave-wave interactions. The evolution of these spectra with growing parameter of nonlinearity of the internal wave field is studied and compared to that of a broad band spectrum of gravity waves with randomly independent amplitudes and phases. The calculated vertical wave number spectra of the vertical displacements or relative temperature fluctuations are found to be consistent with the observed spectra in the middle atmosphere.

  6. Flow control for oblique shock wave reflections

    OpenAIRE

    Giepman, R.H.M.

    2016-01-01

    Shock wave-boundary layer interactions are prevalent in many aerospace applications that involve transonic or supersonic flows. Such interactions may lead to boundary layer separation, flow unsteadiness and substantial losses in the total pressure. Flow control techniques can help to mitigate these adverse effects and stabilize the interaction. This thesis focuses on passive flow control techniques for oblique shock wave reflections on flat plates and presents experimental results for both la...

  7. (abstract) Tropospheric Calibration for the Mars Observer Gravity Wave Experiment

    Science.gov (United States)

    Walter, Steven J.; Armstrong, John

    1994-01-01

    In spring 1993, microwave radiometer-based tropospheric calibration was provided for the Mars Observer gravitational wave search. The Doppler shifted X-band radio signals propagating between Earth and the Mars Observer satellite were precisely measured to determine path length variations that might signal passage of gravitational waves. Experimental sensitivity was restricted by competing sources of variability in signal transit time. Principally, fluctuations in the solar wind and ionospheric plasma density combined with fluctions in tropospheric refractivity determined the detection limit. Troposphere-induced path delay fluctions are dominated by refractive changes caused by water vapor inhomogeneities blowing through the signal path. Since passive microwave remote sensing techniques are able to determine atmospheric propagation delays, radiometer-based tropospheric calibration was provided at the Deep Space Network Uranus tracking site (DSS-15). Two microwave water vapor radiometers (WVRs), a microwave temperature profiler (MTP), and a ground based meterological station were deployed to determine line-of-sight vapor content and vertical temperature profile concurrently with Mars Observer tracking measurements. This calibration system provided the capability to correct Mars Observer Doppler data for troposphere-induced path variations. We present preliminary analysis of the Doppler and WVR data sets illustrating the utility of WVRs to calibrate Doppler data. This takes an important step toward realizing the ambitious system required to support future Ka-band Cassini satellite gravity wave tropospheric calibration system.

  8. WAVES IN THE COMMUNICATION FLOW

    Directory of Open Access Journals (Sweden)

    Fee-Alexandra Haase

    2007-11-01

    Full Text Available This article compares in case studies in the constitution, written laws, and other national institutions the influence of the state regarding the production and function of mass communication and related values in different countries. Our interest is to demonstrate the differences between countries under the aspects of national constitution and governmental institutions that provide or not provide guidelines in terms of the use and protection of communication national organizations that provide additional guidelines international organizations for the use of mass communication media in a country. The interplay of national constitution, legislative, and governmental institutions is the framework for the existence of national mass communication. Under the title “Waves in The Communication Flow“we will face the framework of exterior institutions of different national states regarding their influence on mass communication. As mass communication we can define all institutions producing information for a wide audience delivered in mass media. As a process we can define mass communication as a ‘flow of any information’ delivered by mass media. This flow can be promoted or prohibited by the framework of institutions named above. This article examines the extent and nature of the use of laws and constitutional systems with an interest in the methodology of comparative studies in constitutional law.

  9. Two-Phase Annular Flow in Helical Coil Flow Channels in a Reduced Gravity Environment

    Science.gov (United States)

    Keshock, Edward G.; Lin, Chin S.

    1996-01-01

    A brief review of both single- and two-phase flow studies in curved and coiled flow geometries is first presented. Some of the complexities of two-phase liquid-vapor flow in curved and coiled geometries are discussed, and serve as an introduction to the advantages of observing such flows under a low-gravity environment. The studies proposed -- annular two-phase air-water flow in helical coil flow channels are described. Objectives of the studies are summarized.

  10. The measurement of the total electron content applied to the observation of medium scale gravity wave

    International Nuclear Information System (INIS)

    Bertel, L.; Bertin, F.; Testud, J.

    1976-01-01

    The interpretation of the measurements of the integrated electron content in terms of gravity wave requires (1) a gravity wave model at thermospheric altitudes; (2) a gravity wave-ionization interaction model in the F-region of the ionosphere; and (3) a computing program for the resulting perturbation on the integrated electron content between the satellite and the earth station used. The gravity wave model considered in this paper takes into account the dissipative effects (viscosity, thermal conduction) which become very importanr above 250 km altitude and the effect of the base wind which is capable of affecting deeply the propagation of the waves of medium scale. Starting with this model, the domains of frequencies and the wavelength of atmospheric waves which may exist in the upper atmosphere are considered. The interaction of such waves and the ionization is examined. The theoretical results give information particularly on the selectivity of the ionospheric response to the wave passage. The deduced selectivity of the models appears to be smaller than that given by other authors who used simplified gravity wave models. The method for computing the perturbation of the of the integrated electron content introduced by the wave passage is given for a geostationary satellite. Computational results are presented for application to the case of medium scale gravity waves. (author)

  11. Propagation of internal gravity waves in the inhomogeneous atmosphere

    International Nuclear Information System (INIS)

    Deminov, M.G.; Ponomareva, L.I.

    1988-01-01

    Equations for disturbances of the density, temperature and speed of large-scale horizontally propagating internal gravity wave (IGM) wind are presented with regard to non-linearity, dispersion, molecular viscosity, thermal conductivity and background horizontal density and wind speed gradients. It is shown that values of wind speed and background atmosphere density decrease, typical of night conditions, provide for IGV amplitude increase near 250 km above the equator about 1.5 times, which with regard to the both hemispheres, fully compensates the effect of viscosity and thermal conductivity under increased solar activity. Speed and density decrease along IGW propagation can be provided both by background distribution of thermosphere parameters and by the front of a large-scale IGW on the background of which isolated IGW amplitude can grow

  12. Holographic p-wave superfluid in Gauss–Bonnet gravity

    International Nuclear Information System (INIS)

    Liu, Shancheng; Pan, Qiyuan; Jing, Jiliang

    2017-01-01

    We construct the holographic p-wave superfluid in Gauss–Bonnet gravity via a Maxwell complex vector field model and investigate the effect of the curvature correction on the superfluid phase transition in the probe limit. We obtain the rich phase structure and find that the higher curvature correction hinders the condensate of the vector field but makes it easier for the appearance of translating point from the second-order transition to the first-order one or for the emergence of the Cave of Winds. Moreover, for the supercurrents versus the superfluid velocity, we observe that our results near the critical temperature are independent of the Gauss–Bonnet parameter and agree well with the Ginzburg–Landau prediction.

  13. Holographic p-wave superfluid in Gauss–Bonnet gravity

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shancheng [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Pan, Qiyuan, E-mail: panqiyuan@126.com [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Jing, Jiliang, E-mail: jljing@hunnu.edu.cn [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China)

    2017-02-10

    We construct the holographic p-wave superfluid in Gauss–Bonnet gravity via a Maxwell complex vector field model and investigate the effect of the curvature correction on the superfluid phase transition in the probe limit. We obtain the rich phase structure and find that the higher curvature correction hinders the condensate of the vector field but makes it easier for the appearance of translating point from the second-order transition to the first-order one or for the emergence of the Cave of Winds. Moreover, for the supercurrents versus the superfluid velocity, we observe that our results near the critical temperature are independent of the Gauss–Bonnet parameter and agree well with the Ginzburg–Landau prediction.

  14. GRACILE: a comprehensive climatology of atmospheric gravity wave parameters based on satellite limb soundings

    Directory of Open Access Journals (Sweden)

    M. Ern

    2018-04-01

    Full Text Available Gravity waves are one of the main drivers of atmospheric dynamics. The spatial resolution of most global atmospheric models, however, is too coarse to properly resolve the small scales of gravity waves, which range from tens to a few thousand kilometers horizontally, and from below 1 km to tens of kilometers vertically. Gravity wave source processes involve even smaller scales. Therefore, general circulation models (GCMs and chemistry climate models (CCMs usually parametrize the effect of gravity waves on the global circulation. These parametrizations are very simplified. For this reason, comparisons with global observations of gravity waves are needed for an improvement of parametrizations and an alleviation of model biases. We present a gravity wave climatology based on atmospheric infrared limb emissions observed by satellite (GRACILE. GRACILE is a global data set of gravity wave distributions observed in the stratosphere and the mesosphere by the infrared limb sounding satellite instruments High Resolution Dynamics Limb Sounder (HIRDLS and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER. Typical distributions (zonal averages and global maps of gravity wave vertical wavelengths and along-track horizontal wavenumbers are provided, as well as gravity wave temperature variances, potential energies and absolute momentum fluxes. This global data set captures the typical seasonal variations of these parameters, as well as their spatial variations. The GRACILE data set is suitable for scientific studies, and it can serve for comparison with other instruments (ground-based, airborne, or other satellite instruments and for comparison with gravity wave distributions, both resolved and parametrized, in GCMs and CCMs. The GRACILE data set is available as supplementary data at https://doi.org/10.1594/PANGAEA.879658.

  15. GRACILE: a comprehensive climatology of atmospheric gravity wave parameters based on satellite limb soundings

    Science.gov (United States)

    Ern, Manfred; Trinh, Quang Thai; Preusse, Peter; Gille, John C.; Mlynczak, Martin G.; Russell, James M., III; Riese, Martin

    2018-04-01

    Gravity waves are one of the main drivers of atmospheric dynamics. The spatial resolution of most global atmospheric models, however, is too coarse to properly resolve the small scales of gravity waves, which range from tens to a few thousand kilometers horizontally, and from below 1 km to tens of kilometers vertically. Gravity wave source processes involve even smaller scales. Therefore, general circulation models (GCMs) and chemistry climate models (CCMs) usually parametrize the effect of gravity waves on the global circulation. These parametrizations are very simplified. For this reason, comparisons with global observations of gravity waves are needed for an improvement of parametrizations and an alleviation of model biases. We present a gravity wave climatology based on atmospheric infrared limb emissions observed by satellite (GRACILE). GRACILE is a global data set of gravity wave distributions observed in the stratosphere and the mesosphere by the infrared limb sounding satellite instruments High Resolution Dynamics Limb Sounder (HIRDLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). Typical distributions (zonal averages and global maps) of gravity wave vertical wavelengths and along-track horizontal wavenumbers are provided, as well as gravity wave temperature variances, potential energies and absolute momentum fluxes. This global data set captures the typical seasonal variations of these parameters, as well as their spatial variations. The GRACILE data set is suitable for scientific studies, and it can serve for comparison with other instruments (ground-based, airborne, or other satellite instruments) and for comparison with gravity wave distributions, both resolved and parametrized, in GCMs and CCMs. The GRACILE data set is available as supplementary data at https://doi.org/10.1594/PANGAEA.879658" target="_blank">https://doi.org/10.1594/PANGAEA.879658.

  16. 21 CFR 880.2420 - Electronic monitor for gravity flow infusion systems.

    Science.gov (United States)

    2010-04-01

    ... and Personal Use Monitoring Devices § 880.2420 Electronic monitor for gravity flow infusion systems. (a) Identification. An electronic monitor for gravity flow infusion systems is a device used to... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Electronic monitor for gravity flow infusion...

  17. A case study of typhoon-induced gravity waves and the orographic impacts related to Typhoon Mindulle (2004) over Taiwan

    OpenAIRE

    Wu, J. F.; Xue, X. H.; Hoffmann, L.; Dou, X. K.; Li, H. M.; Chen, T. D.

    2015-01-01

    Atmospheric gravity waves (GWs) significantly influence global circulation. Deep convection, particularly that associated with typhoons, is believed to be an important source of gravity waves. Stratospheric gravity waves induced by Typhoon Mindulle (2004) were detected by the Atmospheric Infrared Sounder (AIRS). Semicircular GWs with horizontal wavelengths of 100–400 km were found over Taiwan through an inspection of AIRS radiances at 4.3 μm. Characteristics of the stratospheric gravity waves...

  18. Smoothed-particle-hydrodynamics modeling of dissipation mechanisms in gravity waves.

    Science.gov (United States)

    Colagrossi, Andrea; Souto-Iglesias, Antonio; Antuono, Matteo; Marrone, Salvatore

    2013-02-01

    The smoothed-particle-hydrodynamics (SPH) method has been used to study the evolution of free-surface Newtonian viscous flows specifically focusing on dissipation mechanisms in gravity waves. The numerical results have been compared with an analytical solution of the linearized Navier-Stokes equations for Reynolds numbers in the range 50-5000. We found that a correct choice of the number of neighboring particles is of fundamental importance in order to obtain convergence towards the analytical solution. This number has to increase with higher Reynolds numbers in order to prevent the onset of spurious vorticity inside the bulk of the fluid, leading to an unphysical overdamping of the wave amplitude. This generation of spurious vorticity strongly depends on the specific kernel function used in the SPH model.

  19. Slope wavenumber spectrum models of capillary and capillary-gravity waves

    Institute of Scientific and Technical Information of China (English)

    贾永君; 张杰; 王岩峰

    2010-01-01

    Capillary and capillary-gravity waves possess a random character, and the slope wavenumber spectra of them can be used to represent mean distributions of wave energy with respect to spatial scale of variability. But simple and practical models of the slope wavenumber spectra have not been put forward so far. In this article, we address the accurate definition of the slope wavenumber spectra of water surface capillary and capillary-gravity waves. By combining the existing slope wavenumber models and using th...

  20. Gravity Waves in the Atmosphere of Mars as seen by the Radio Science Experiment MaRS on Mars Express

    Science.gov (United States)

    Tellmann, S.; Paetzold, M.; Häusler, B.; Bird, M. K.; Tyler, G. L.; Hinson, D. P.

    2016-12-01

    Gravity waves are atmospheric waves whose restoring force is the buoyancy. They are known to play an essential role in the redistribution of energy, momentum and atmospheric constituents in all stably stratified planetary atmospheres. Possible excitation mechanisms comprise convection in an adjacent atmospheric layer, other atmospheric instabilities like wind shear instabilities, or air flow over orographic obstacles especially in combination with the strong winter jets on Mars. Gravity waves on Mars were observed in the lower atmosphere [1,2] but are also expected to play a major role in the cooling of the thermosphere [3] and the polar warming [4]. A fundamental understanding of the possible source mechanisms is required to reveal the influence of small scale gravity waves on the global atmospheric circulation. Radio occultation profiles from the MaRS experiment on Mars Express [5] with their exceptionally high vertical resolution can be used to study small-scale vertical gravity waves and their global distribution in the lower atmosphere from the planetary boundary layer up to 40 km altitude. Atmospheric instabilities, which are clearly identified in the data, are used to gain further insight into possible atmospheric processes contributing to the excitation of gravity waves. [1] Creasey, J. E., et al.,(2006), Geophys. Res. Lett., 33, L01803, doi:10.1029/2005GL024037. [2]Tellmann, S., et al.(2013), J. Geophys. Res. Planets, 118, 306-320, doi:10.1002/jgre.20058. [3]Medvedev, A. S., et al.(2015), J. Geophys. Res. Planets, 120, 913-927. doi:10.1002/2015JE004802.[4] Barnes, J. R. (1990), J. Geophys. Res., 95, B2, 1401-1421. [5] Pätzold, M., et al. (2016), Planet. Space Sci., 127, 44 - 90.

  1. Topologically massive gravity and Ricci-Cotton flow

    Energy Technology Data Exchange (ETDEWEB)

    Lashkari, Nima; Maloney, Alexander, E-mail: lashkari@physics.mcgill.ca, E-mail: maloney@physics.mcgill.ca [McGill Physics Department, 3600 rue University, Montreal, QC H3A 2T8 (Canada)

    2011-05-21

    We consider topologically massive gravity (TMG), which is three-dimensional general relativity with a cosmological constant and a gravitational Chern-Simons term. When the cosmological constant is negative the theory has two potential vacuum solutions: anti-de Sitter space and warped anti-de Sitter space. The theory also contains a massive graviton state which renders these solutions unstable for certain values of the parameters and boundary conditions. We study the decay of these solutions due to the condensation of the massive graviton mode using Ricci-Cotton flow, which is the appropriate generalization of Ricci flow to TMG. When the Chern-Simons coupling is small the AdS solution flows to warped AdS by the condensation of the massive graviton mode. When the coupling is large the situation is reversed, and warped AdS flows to AdS. Minisuperspace models are constructed where these flows are studied explicitly.

  2. Topologically massive gravity and Ricci-Cotton flow

    International Nuclear Information System (INIS)

    Lashkari, Nima; Maloney, Alexander

    2011-01-01

    We consider topologically massive gravity (TMG), which is three-dimensional general relativity with a cosmological constant and a gravitational Chern-Simons term. When the cosmological constant is negative the theory has two potential vacuum solutions: anti-de Sitter space and warped anti-de Sitter space. The theory also contains a massive graviton state which renders these solutions unstable for certain values of the parameters and boundary conditions. We study the decay of these solutions due to the condensation of the massive graviton mode using Ricci-Cotton flow, which is the appropriate generalization of Ricci flow to TMG. When the Chern-Simons coupling is small the AdS solution flows to warped AdS by the condensation of the massive graviton mode. When the coupling is large the situation is reversed, and warped AdS flows to AdS. Minisuperspace models are constructed where these flows are studied explicitly.

  3. Flow control for oblique shock wave reflections

    NARCIS (Netherlands)

    Giepman, R.H.M.

    2016-01-01

    Shock wave-boundary layer interactions are prevalent in many aerospace applications that involve transonic or supersonic flows. Such interactions may lead to boundary layer separation, flow unsteadiness and substantial losses in the total pressure. Flow control techniques can help to mitigate these

  4. Ocular Blood Flow Measured Noninvasively in Zero Gravity

    Science.gov (United States)

    Ansari, Rafat R.; Manuel, Francis K.; Geiser, Martial; Moret, Fabrice; Messer, Russell K.; King, James F.; Suh, Kwang I.

    2003-01-01

    In spaceflight or a reduced-gravity environment, bodily fluids shift to the upper extremities of the body. The pressure inside the eye, or intraocular pressure, changes significantly. A significant number of astronauts report changes in visual acuity during orbital flight. To date this remains of unknown etiology. Could choroidal engorgement be the primary mechanism and a change in the curvature or shape of the cornea or lens be the secondary mechanism for this change in visual acuity? Perfused blood flow in the dense meshwork of capillaries of the choroidal tissue (see the preceding illustration) provides necessary nutrients to the outer layers of the retina (photoreceptors) to keep it healthy and maintain good vision. Unlike the vascular system, the choroid has no baroreceptors to autoregulate fluid shifts, so it can remain engorged, pushing the macula forward and causing a hyperopic (farsighted) shift of the eye. Experiments by researchers at the NASA Glenn Research Center could help answer this question and facilitate planning for long-duration missions. We are investigating the effects of zero gravity on the choroidal blood flow of volunteer subjects. This pilot project plans to determine if choroidal blood flow is autoregulated in a reduced-gravity environment.

  5. Propagation of waves in shear flows

    CERN Document Server

    Fabrikant, A L

    1998-01-01

    The state of the art in a theory of oscillatory and wave phenomena in hydrodynamical flows is presented in this book. A unified approach is used for waves of different physical origins. A characteristic feature of this approach is that hydrodynamical phenomena are considered in terms of physics; that is, the complement of the conventionally employed formal mathematical approach. Some physical concepts such as wave energy and momentum in a moving fluid are analysed, taking into account induced mean flow. The physical mechanisms responsible for hydrodynamic instability of shear flows are conside

  6. Instability-induced ordering, universal unfolding and the role of gravity in granular Couette flow

    Science.gov (United States)

    Alam, Meheboob; Arakeri, V. H.; Nott, P. R.; Goddard, J. D.; Herrmann, H. J.

    2005-01-01

    Linear stability theory and bifurcation analysis are used to investigate the role of gravity in shear-band formation in granular Couette flow, considering a kinetic-theory rheological model. We show that the only possible state, at low shear rates, corresponds to a "plug" near the bottom wall, in which the particles are densely packed and the shear rate is close to zero, and a uniformly sheared dilute region above it. The origin of such plugged states is shown to be tied to the spontaneous symmetry-breaking instabilities of the gravity-free uniform shear flow, leading to the formation of ordered bands of alternating dilute and dense regions in the transverse direction, via an infinite hierarchy of pitchfork bifurcations. Gravity plays the role of an "imperfection", thus destroying the "perfect" bifurcation structure of uniform shear. The present bifurcation problem admits universal unfolding of pitchfork bifurcations which subsequently leads to the formation of a sequence of a countably infinite number of "isolas", with the solution structures being a modulated version of their gravity-free counterpart. While the solution with a plug near the bottom wall looks remarkably similar to the shear-banding phenomenon in dense slow granular Couette flows, a "floating" plug near the top wall is also a solution of these equations at high shear rates. A two-dimensional linear stability analysis suggests that these floating plugged states are unstable to long-wave travelling disturbances.The unique solution having a bottom plug can also be unstable to long waves, but remains stable at sufficiently low shear rates. The implications and realizability of the present results are discussed in the light of shear-cell experiments under "microgravity" conditions.

  7. Comparison of Global Distributions of Zonal-Mean Gravity Wave Variance Inferred from Different Satellite Instruments

    Science.gov (United States)

    Preusse, Peter; Eckermann, Stephen D.; Offermann, Dirk; Jackman, Charles H. (Technical Monitor)

    2000-01-01

    Gravity wave temperature fluctuations acquired by the CRISTA instrument are compared to previous estimates of zonal-mean gravity wave temperature variance inferred from the LIMS, MLS and GPS/MET satellite instruments during northern winter. Careful attention is paid to the range of vertical wavelengths resolved by each instrument. Good agreement between CRISTA data and previously published results from LIMS, MLS and GPS/MET are found. Key latitudinal features in these variances are consistent with previous findings from ground-based measurements and some simple models. We conclude that all four satellite instruments provide reliable global data on zonal-mean gravity wave temperature fluctuations throughout the middle atmosphere.

  8. Gravity waves as a probe of the Hubble expansion rate during an electroweak scale phase transition

    International Nuclear Information System (INIS)

    Chung, Daniel J. H.; Zhou Peng

    2010-01-01

    Just as big bang nucleosynthesis allows us to probe the expansion rate when the temperature of the Universe was around 1 MeV, the measurement of gravity waves from electroweak scale first order phase transitions may allow us to probe the expansion rate when the temperature of the Universe was at the electroweak scale. We compute the simple transformation rule for the gravity wave spectrum under the scaling transformation of the Hubble expansion rate. We then apply this directly to the scenario of quintessence kination domination and show how gravity wave spectra would shift relative to Laser Interferometer Space Antenna and Big Bang Observer projected sensitivities.

  9. Temporal variability of tidal and gravity waves during a record long 10-day continuous lidar sounding

    Science.gov (United States)

    Baumgarten, Kathrin; Gerding, Michael; Baumgarten, Gerd; Lübken, Franz-Josef

    2018-01-01

    Gravity waves (GWs) as well as solar tides are a key driving mechanism for the circulation in the Earth's atmosphere. The propagation of gravity waves is strongly affected by tidal waves as they modulate the mean background wind field and vice versa, which is not yet fully understood and not adequately implemented in many circulation models. The daylight-capable Rayleigh-Mie-Raman (RMR) lidar at Kühlungsborn (54° N, 12° E) typically provides temperature data to investigate both wave phenomena during one full day or several consecutive days in the middle atmosphere between 30 and 75 km altitude. Outstanding weather conditions in May 2016 allowed for an unprecedented 10-day continuous lidar measurement, which shows a large variability of gravity waves and tides on timescales of days. Using a one-dimensional spectral filtering technique, gravity and tidal waves are separated according to their specific periods or vertical wavelengths, and their temporal evolution is studied. During the measurement period a strong 24 h wave occurs only between 40 and 60 km and vanishes after a few days. The disappearance is related to an enhancement of gravity waves with periods of 4-8 h. Wind data provided by ECMWF are used to analyze the meteorological situation at our site. The local wind structure changes during the observation period, which leads to different propagation conditions for gravity waves in the last days of the measurement period and therefore a strong GW activity. The analysis indicates a further change in wave-wave interaction resulting in a minimum of the 24 h tide. The observed variability of tides and gravity waves on timescales of a few days clearly demonstrates the importance of continuous measurements with high temporal and spatial resolution to detect interaction phenomena, which can help to improve parametrization schemes of GWs in general circulation models.

  10. Analyses of the stratospheric dynamics simulated by a GCM with a stochastic nonorographic gravity wave parameterization

    Science.gov (United States)

    Serva, Federico; Cagnazzo, Chiara; Riccio, Angelo

    2016-04-01

    The effects of the propagation and breaking of atmospheric gravity waves have long been considered crucial for their impact on the circulation, especially in the stratosphere and mesosphere, between heights of 10 and 110 km. These waves, that in the Earth's atmosphere originate from surface orography (OGWs) or from transient (nonorographic) phenomena such as fronts and convective processes (NOGWs), have horizontal wavelengths between 10 and 1000 km, vertical wavelengths of several km, and frequencies spanning from minutes to hours. Orographic and nonorographic GWs must be accounted for in climate models to obtain a realistic simulation of the stratosphere in both hemispheres, since they can have a substantial impact on circulation and temperature, hence an important role in ozone chemistry for chemistry-climate models. Several types of parameterization are currently employed in models, differing in the formulation and for the values assigned to parameters, but the common aim is to quantify the effect of wave breaking on large-scale wind and temperature patterns. In the last decade, both global observations from satellite-borne instruments and the outputs of very high resolution climate models provided insight on the variability and properties of gravity wave field, and these results can be used to constrain some of the empirical parameters present in most parameterization scheme. A feature of the NOGW forcing that clearly emerges is the intermittency, linked with the nature of the sources: this property is absent in the majority of the models, in which NOGW parameterizations are uncoupled with other atmospheric phenomena, leading to results which display lower variability compared to observations. In this work, we analyze the climate simulated in AMIP runs of the MAECHAM5 model, which uses the Hines NOGW parameterization and with a fine vertical resolution suitable to capture the effects of wave-mean flow interaction. We compare the results obtained with two

  11. Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

    International Nuclear Information System (INIS)

    Sugimoto, Norihiko

    2015-01-01

    Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone–anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone–anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (∼2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone–anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves

  12. Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, Norihiko, E-mail: nori@phys-h.keio.ac.jp [Department of Physics, Research and Education Center for Natural Sciences, Keio University, 4-1-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8521 (Japan)

    2015-12-15

    Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone–anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone–anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (∼2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone–anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves.

  13. The propagation of orographic gravity waves into the stratosphere. Linear theory, idealized and realistic numerical simulation; Die Ausbreitung orographisch angeregter Schwerewellen in die Stratosphaere. Lineare Theorie, idealisierte und realitaetsnahe numerische Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Leutbecher, M. [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Wessling (Germany). Inst. fuer Physik der Atmosphaere

    1998-07-01

    Flow over mountains in the stably stratified atmosphere excites gravity waves. The three-dimensional propagation of these waves into the stratosphere is studied using linear theority as well as idealized and realistic numerical simulations. Stagnation, momentum fluxes and temperature anomalies are analyzed for idealized types of flow. Isolated mountains with elliptical contours are considered. The unperturbed atmosphere has constant wind speed and constant static stability or two layers (troposphere/stratosphere) of constant stability each. Real flow over orography is investigated where gravity waves in the stratosphere have been observed. Characteristics of the gravity wave event over the southern tip of Greenland on 6 January 1992 were recorded on a flight of the ER-2 at an altitude of 20 km. In the second case polar stratospheric clouds (PSC) were observed by an airborne Lidar over Northern Scandinavia on 9 January 1997. The PSC were induced by temperature anomalies in orographic gravity waves. (orig.)

  14. Gravity waves, Tides and Planetary wave characteristics revealed by network of MLT radars over Indian region

    Science.gov (United States)

    Venkat Ratnam, Madineni; Karanam, Kishore Kumar; Sunkara, Eswaraiah; Vijaya Bhaskara Rao, S.; Subrahmanyam, K. V.; Ramanjaneyulu, L.

    2016-07-01

    Mesosphere and Lower Thermosphere (MLT) mean winds, gravity waves, tidal and planetary wave characteristics are investigated using two years (2013-2015) of advanced meteor radar installed at Tirupathi (13.63oN, 79.4oE), India. The observations reveal the presence of high frequency gravity waves (30-120 minutes), atmospheric tides (diurnal, semi-diurnal and terr-diurnal) along with long period oscillations in both zonal and meridional winds. Background mean zonal winds show clear semi-annual oscillation in the mesosphere, whereas meridional winds are characterized by annual oscillation as expected. Diurnal tide amplitudes are significantly larger (60-80 m/s) than semi-diurnal (10-20 m/s) and terr-diurnal (5-8 m/s) tides and larger in meridional than zonal winds. The measured meridional components are in good agreement with Global Scale Wave Model (GSWM-09) predictions than zonal up to ~90 km in all the seasons, except fall equinox. Diurnal tidal phase matches well than the amplitudes between observations and model predictions. However, no similarity is being found in the semi-diurnal tides between observations and model. The measurements are further compared with nearby Thumba meteor radar (8.5oN, 77oE) observations. Some differences do exist between the measurements from Tirupati and Thumba meteor radar and model outputs at greater heights and the possible reasons are discussed. SVU meteor radar observations clearly showed the dominance of well-known ultra-fast kelvin waves (3.5 days), 5-8 day, 16 day, 27 day, and 30-40 day oscillations. Due to higher meteor count extending up to 110 km, we could investigate the variability of these PWs and oscillations covering wider range (70-110 km) for the first time. Significant change above 100 km is noticed in all the above mentioned PW activity and oscillations. We also used ERA-Interim reanalysis data sets available at 0.125x0.125 degree grids for investigating the characteristics of these PW right from surface to 1 h

  15. Stratified Coastal Trapped Waves and Mean Flows

    National Research Council Canada - National Science Library

    Thompson, LuAnne

    1998-01-01

    Our long term goals are to identify the roles that rectified subinertial waves and mesoscale motions play in the mean-flow transport of fluid properties in the coastal ocean and to apply these ideas...

  16. Gravity wave life cycle (GW-LCYCLE): Initial results from a coordinated field program to trace gravity waves from the troposphere to the MLT-region

    Science.gov (United States)

    Rapp, Markus

    Gravity waves (GW) play an important role in the coupling between the troposphere and the middle atmosphere (˜10 - 120 km). GWs couple different atmospheric regions both in the vertical as well as in the horizontal directions by means of momentum and energy transport. Notably, this coupling is effective both from the troposphere upwards, and also in the opposite direction by indirect effects on circulation patterns. While the importance of GW for understanding atmospheric structure, dynamics and climate is now widely recognized, surprisingly little is still known about the details of the GW life cycle, i.e., the processes of GW excitation, propagation and dissipation. To address this issue a coordinated field program - named GW-LCYCLE - has been established in which ground based observations with radars, lidars and airglow imagers are combined with airborne observations, balloon soundings, and modelling to trace GWs from their source in the troposphere to their area of dissipation in the middle atmosphere. Within GW-LCYCLE an initial field campaign was conducted in December 2013 in Northern Scandinavia. The research aircraft DLR-FALCON was deployed to Kiruna, Sweden, from where several flights (with a total of 25 flight hours) were conducted to study mountain wave generation by flow over the Scandinavian mountain ridge. The FALCON was equipped with a downward looking wind lidar operating at a wavelength of 2 mum as well as with an in-flight system to measure winds, temperatures and pressures and with several in-situ instruments to detect wave signatures in trace gases like H _{2}O, CO _{2}, CO, CH _{4}, N _{2}O, HNO _{3} and SO _{2}. Ground based observations of winds and temperatures from the troposphere to the mesosphere/lower thermosphere (MLT-) region were conducted from Kiruna as well as from Andenes, Norway. These measurements were augmented by balloon soundings from the same places as well as from Sodankylä in Finland. Coordinated observations were

  17. Propagation of 3D internal gravity wave beams in a slowly varying stratification

    Science.gov (United States)

    Fan, Boyu; Akylas, T. R.

    2017-11-01

    The time-mean flows induced by internal gravity wave beams (IGWB) with 3D variations have been shown to have dramatic implications for long-term IGWB dynamics. While uniform stratifications are convenient both theoretically and in the laboratory, stratifications in the ocean can vary by more than an order of magnitude over the ocean depth. Here, in view of this fact, we study the propagation of a 3D IGWB in a slowly varying stratification. We assume that the stratification varies slowly relative to the local variations in the wave profile. In the 2D case, the IGWB bends in response to the changing stratification, but nonlinear effects are minor even in the finite amplitude regime. For a 3D IGWB, in addition to bending, we find that nonlinearity results in the transfer of energy from waves to a large-scale time-mean flow associated with the mean potential vorticity, similar to IGWB behavior in a uniform stratification. In a weakly nonlinear setting, we derive coupled evolution equations that govern this process. We also use these equations to determine the stability properties of 2D IGWB to 3D perturbations. These findings indicate that 3D effects may be relevant and possibly fundamental to IGWB dynamics in nature. Supported by NSF Grant DMS-1512925.

  18. Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry

    Directory of Open Access Journals (Sweden)

    A. J. Spargo

    2017-06-01

    Full Text Available Mesospheric gravity wave (GW momentum flux estimates using data from multibeam Buckland Park MF radar (34.6° S, 138.5° E experiments (conducted from July 1997 to June 1998 are presented. On transmission, five Doppler beams were symmetrically steered about the zenith (one zenith beam and four off-zenith beams in the cardinal directions. The received beams were analysed with hybrid Doppler interferometry (HDI (Holdsworth and Reid, 1998, principally to determine the radial velocities of the effective scattering centres illuminated by the radar. The methodology of Thorsen et al. (1997, later re-introduced by Hocking (2005 and since extensively applied to meteor radar returns, was used to estimate components of Reynolds stress due to propagating GWs and/or turbulence in the radar resolution volume. Physically reasonable momentum flux estimates are derived from the Reynolds stress components, which are also verified using a simple radar model incorporating GW-induced wind perturbations. On the basis of these results, we recommend the intercomparison of momentum flux estimates between co-located meteor radars and vertical-beam interferometric MF radars. It is envisaged that such intercomparisons will assist with the clarification of recent concerns (e.g. Vincent et al., 2010 of the accuracy of the meteor radar technique.

  19. Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry

    Science.gov (United States)

    Spargo, Andrew J.; Reid, Iain M.; MacKinnon, Andrew D.; Holdsworth, David A.

    2017-06-01

    Mesospheric gravity wave (GW) momentum flux estimates using data from multibeam Buckland Park MF radar (34.6° S, 138.5° E) experiments (conducted from July 1997 to June 1998) are presented. On transmission, five Doppler beams were symmetrically steered about the zenith (one zenith beam and four off-zenith beams in the cardinal directions). The received beams were analysed with hybrid Doppler interferometry (HDI) (Holdsworth and Reid, 1998), principally to determine the radial velocities of the effective scattering centres illuminated by the radar. The methodology of Thorsen et al. (1997), later re-introduced by Hocking (2005) and since extensively applied to meteor radar returns, was used to estimate components of Reynolds stress due to propagating GWs and/or turbulence in the radar resolution volume. Physically reasonable momentum flux estimates are derived from the Reynolds stress components, which are also verified using a simple radar model incorporating GW-induced wind perturbations. On the basis of these results, we recommend the intercomparison of momentum flux estimates between co-located meteor radars and vertical-beam interferometric MF radars. It is envisaged that such intercomparisons will assist with the clarification of recent concerns (e.g. Vincent et al., 2010) of the accuracy of the meteor radar technique.

  20. Tropical Gravity Wave Momentum Fluxes and Latent Heating Distributions

    Science.gov (United States)

    Geller, Marvin A.; Zhou, Tiehan; Love, Peter T.

    2015-01-01

    Recent satellite determinations of global distributions of absolute gravity wave (GW) momentum fluxes in the lower stratosphere show maxima over the summer subtropical continents and little evidence of GW momentum fluxes associated with the intertropical convergence zone (ITCZ). This seems to be at odds with parameterizations forGWmomentum fluxes, where the source is a function of latent heating rates, which are largest in the region of the ITCZ in terms of monthly averages. The authors have examined global distributions of atmospheric latent heating, cloud-top-pressure altitudes, and lower-stratosphere absolute GW momentum fluxes and have found that monthly averages of the lower-stratosphere GW momentum fluxes more closely resemble the monthly mean cloud-top altitudes rather than the monthly mean rates of latent heating. These regions of highest cloud-top altitudes occur when rates of latent heating are largest on the time scale of cloud growth. This, plus previously published studies, suggests that convective sources for stratospheric GW momentum fluxes, being a function of the rate of latent heating, will require either a climate model to correctly model this rate of latent heating or some ad hoc adjustments to account for shortcomings in a climate model's land-sea differences in convective latent heating.

  1. Simulation of non-hydrostatic gravity wave propagation in the upper atmosphere

    Directory of Open Access Journals (Sweden)

    Y. Deng

    2014-04-01

    Full Text Available The high-frequency and small horizontal scale gravity waves may be reflected and ducted in non-hydrostatic simulations, but usually propagate vertically in hydrostatic models. To examine gravity wave propagation, a preliminary study has been conducted with a global ionosphere–thermosphere model (GITM, which is a non-hydrostatic general circulation model for the upper atmosphere. GITM has been run regionally with a horizontal resolution of 0.2° long × 0.2° lat to resolve the gravity wave with wavelength of 250 km. A cosine wave oscillation with amplitude of 30 m s−1 has been applied to the zonal wind at the low boundary, and both high-frequency and low-frequency waves have been tested. In the high-frequency case, the gravity wave stays below 200 km, which indicates that the wave is reflected or ducted in propagation. The results are consistent with the theoretical analysis from the dispersion relationship when the wavelength is larger than the cutoff wavelength for the non-hydrostatic situation. However, the low-frequency wave propagates to the high altitudes during the whole simulation period, and the amplitude increases with height. This study shows that the non-hydrostatic model successfully reproduces the high-frequency gravity wave dissipation.

  2. Agradient velocity, vortical motion and gravity waves in a rotating shallow-water model

    Science.gov (United States)

    Sutyrin Georgi, G.

    2004-07-01

    A new approach to modelling slow vortical motion and fast inertia-gravity waves is suggested within the rotating shallow-water primitive equations with arbitrary topography. The velocity is exactly expressed as a sum of the gradient wind, described by the Bernoulli function,B, and the remaining agradient part, proportional to the velocity tendency. Then the equation for inverse potential vorticity,Q, as well as momentum equations for agradient velocity include the same source of intrinsic flow evolution expressed as a single term J (B, Q), where J is the Jacobian operator (for any steady state J (B, Q) = 0). Two components of agradient velocity are responsible for the fast inertia-gravity wave propagation similar to the traditionally used divergence and ageostrophic vorticity. This approach allows for the construction of balance relations for vortical dynamics and potential vorticity inversion schemes even for moderate Rossby and Froude numbers assuming the characteristic value of |J(B, Q)| = to be small. The components of agradient velocity are used as the fast variables slaved to potential vorticity that allows for diagnostic estimates of the velocity tendency, the direct potential vorticity inversion with the accuracy of 2 and the corresponding potential vorticity-conserving agradient velocity balance model (AVBM). The ultimate limitations of constructing the balance are revealed in the form of the ellipticity condition for balanced tendency of the Bernoulli function which incorporates both known criteria of the formal stability: the gradient wind modified by the characteristic vortical Rossby wave phase speed should be subcritical. The accuracy of the AVBM is illustrated by considering the linear normal modes and coastal Kelvin waves in the f-plane channel with topography.

  3. A global climatology of stratospheric gravity waves from Atmospheric Infrared Sounder observations

    Science.gov (United States)

    Hoffmann, Lars; Xue, Xianghui; Alexander, M. Joan

    2014-05-01

    We present the results of a new study that aims on the detection and classification of `hotspots' of stratospheric gravity waves on a global scale. The analysis is based on a nine-year record (2003 to 2011) of radiance measurements by the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite. We detect the presence of stratospheric gravity waves based on 4.3 micron brightness temperature variances. Our method is optimized for peak events, i.e., strong gravity wave events for which the local variance considerably exceeds background levels. We estimated the occurrence frequencies of these peak events for different seasons and time of day and used the results to find local maxima of gravity wave activity. In addition, we use AIRS radiances at 8.1 micron to simultaneously detect convective events, including deep convection in the tropics and mesoscale convective systems at mid latitudes. We classified the gravity waves according to their sources, based on seasonal occurrence frequencies for convection and by means of topographic data. Our study reproduces well-known hotspots of gravity waves, e.g., the mountain wave hotspots at the Andes and the Antarctic Peninsula or the convective hotspot during the thunderstorm season over the North American Great Plains. However, the high horizontal resolution of the AIRS observations also helped us to locate several smaller hotspots, which were partly unknown or poorly studied so far. Most of these smaller hotspots are found near orographic features like small mountain ranges, in coastal regions, in desert areas, or near isolated islands. This new study will help to select the most promising regions and seasons for future observational studies of gravity waves. Reference: Hoffmann, L., X. Xue, and M. J. Alexander, A global view of stratospheric gravity wave hotspots located with Atmospheric Infrared Sounder observations, J. Geophys. Res., 118, 416-434, doi:10.1029/2012JD018658, 2013.

  4. Detection of traveling ionospheric disturbances induced by atmospheric gravity waves using the global positioning system

    Science.gov (United States)

    Bassiri, Sassan; Hajj, George A.

    1993-01-01

    Natural and man-made events like earthquakes and nuclear explosions launch atmospheric gravity waves (AGW) into the atmosphere. Since the particle density decreases exponentially with height, the gravity waves increase exponentially in amplitude as they propagate toward the upper atmosphere and ionosphere. As atmospheric gravity waves approach the ionospheric heights, the neutral particles carried by gravity waves collide with electrons and ions, setting these particles in motion. This motion of charged particles manifests itself by wave-like fluctuations and disturbances that are known as traveling ionospheric disturbances (TID). The perturbation in the total electron content due to TID's is derived analytically from first principles. Using the tilted dipole magnetic field approximation and a Chapman layer distribution for the electron density, the variations of the total electron content versus the line-of-sight direction are numerically analyzed. The temporal variation associated with the total electron content measurements due to AGW's can be used as a means of detecting characteristics of the gravity waves. As an example, detection of tsunami generated earthquakes from their associated atmospheric gravity waves using the Global Positioning System is simulated.

  5. Renormalization group flow of scalar models in gravity

    International Nuclear Information System (INIS)

    Guarnieri, Filippo

    2014-01-01

    In this Ph.D. thesis we study the issue of renormalizability of gravitation in the context of the renormalization group (RG), employing both perturbative and non-perturbative techniques. In particular, we focus on different gravitational models and approximations in which a central role is played by a scalar degree of freedom, since their RG flow is easier to analyze. We restrict our interest in particular to two quantum gravity approaches that have gained a lot of attention recently, namely the asymptotic safety scenario for gravity and the Horava-Lifshitz quantum gravity. In the so-called asymptotic safety conjecture the high energy regime of gravity is controlled by a non-Gaussian fixed point which ensures non-perturbative renormalizability and finiteness of the correlation functions. We then investigate the existence of such a non trivial fixed point using the functional renormalization group, a continuum version of the non-perturbative Wilson's renormalization group. In particular we quantize the sole conformal degree of freedom, which is an approximation that has been shown to lead to a qualitatively correct picture. The question of the existence of a non-Gaussian fixed point in an infinite-dimensional parameter space, that is for a generic f(R) theory, cannot however be studied using such a conformally reduced model. Hence we study it by quantizing a dynamically equivalent scalar-tensor theory, i.e. a generic Brans-Dicke theory with ω=0 in the local potential approximation. Finally, we investigate, using a perturbative RG scheme, the asymptotic freedom of the Horava-Lifshitz gravity, that is an approach based on the emergence of an anisotropy between space and time which lifts the Newton's constant to a marginal coupling and explicitly preserves unitarity. In particular we evaluate the one-loop correction in 2+1 dimensions quantizing only the conformal degree of freedom.

  6. Influence of Gravity on Blood Volume and Flow Distribution

    Science.gov (United States)

    Pendergast, D.; Olszowka, A.; Bednarczyk, E.; Shykoff, B.; Farhi, L.

    1999-01-01

    In our previous experiments during NASA Shuttle flights SLS 1 and 2 (9-15 days) and EUROMIR flights (30-90 days) we observed that pulmonary blood flow (cardiac output) was elevated initially, and surprisingly remained elevated for the duration of the flights. Stroke volume increased initially and then decreased, but was still above 1 Gz values. As venous return was constant, the changes in SV were secondary to modulation of heart rate. Mean blood pressure was at or slightly below 1 Gz levels in space, indicating a decrease in total peripheral resistance. It has been suggested that plasma volume is reduced in space, however cardiac output/venous return do not return to 1 Gz levels over the duration of flight. In spite of the increased cardiac output, central venous pressure was not elevated in space. These data suggest that there is a change in the basic relationship between cardiac output and central venous pressure, a persistent "hyperperfusion" and a re-distribution of blood flow and volume during space flight. Increased pulmonary blood flow has been reported to increase diffusing capacity in space, presumably due to the improved homogeneity of ventilation and perfusion. Other studies have suggested that ventilation may be independent of gravity, and perfusion may not be gravity- dependent. No data for the distribution of pulmonary blood volume were available for flight or simulated microgravity. Recent studies have suggested that the pulmonary vascular tree is influenced by sympathetic tone in a manner similar to that of the systemic system. This implies that the pulmonary circulation is dilated during microgravity and that the distribution of blood flow and volume may be influenced more by vascular control than by gravity. The cerebral circulation is influenced by sympathetic tone similarly to that of the systemic and pulmonary circulations; however its effects are modulated by cerebral autoregulation. Thus it is difficult to predict if cerebral perfusion is

  7. Thermal effect on gravity waves in a compressible liquid layer over a ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Abstract. This paper deals with the effect of temperature on gravity waves in a compressible liquid layer over a solid half-space. It has been assumed that the liquid layer is under the action of gravity, while the solid half-space is under the influence of initial compressive hydrostatic stress. When the temperature of the.

  8. Thermal effect on gravity waves in a compressible liquid layer over a ...

    Indian Academy of Sciences (India)

    This paper deals with the effect of temperature on gravity waves in a compressible liquid layer over a solid half-space. It has been assumed that the liquid layer is under the action of gravity, while the solid half-space is under the influence of initial compressive hydrostatic stress. When the temperature of the half-space is ...

  9. Numerical Simulation of a Breaking Gravity Wave Event Over Greenland Observed During Fastex

    National Research Council Canada - National Science Library

    Doyle, James

    1997-01-01

    Measurements from the NOAA G4 research aircraft and high-resolution numerical simulations are used to study the evolution and dynamics of a large-amplitude gravity wave event over Greenland that took...

  10. Ultra-Low Noise Quad Photoreceiver for Space Based Laser Interferometric Gravity Wave Detection, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Gravity wave detection using space-based long-baseline laser interferometric sensors imposes stringent noise requirements on the system components, including the...

  11. Seasonal variation and sources of atmospheric gravity waves in the Antarctic

    Directory of Open Access Journals (Sweden)

    Kaoru Sato

    2010-12-01

    Full Text Available In the last recent ten years, our knowledge of gravity waves in the Antarctic has been significantly improved through numerous studies using balloon and satellite observations and high-resolution model simulations. In this report, we introduce results from two studies which were performed as a part of the NIPR project "Integrated analysis of the material circulation in the Antarctic atmosphere-cryosphere-ocean" (2004-2009, i.e., Yoshiki et al. (2004 and Sato and Yoshiki (2008. These two studies focused on the seasonal variation and sources of the gravity waves in the Antarctic, because horizontal wavelengths and phase velocities depend largely on the wave sources. The former study used original high-resolution data from operational radiosonde observations at Syowa Station. In the lowermost stratosphere, gravity waves do not exhibit characteristic seasonal variation; instead, the wave energy is intensified when lower latitude air intrudes into the area near Syowa Station in the upper troposphere. This intrusion is associated with blocking events or developed synoptic-scale waves. In the lower and middle stratosphere, the gravity wave energy is maximized in spring and particularly intensified when the axis of the polar night jet approaches Syowa Station. The latter study is based on intensive radiosonde observation campaigns that were performed in 2002 at Syowa Station as an activity of JARE-43. Gravity wave propagation was statistically examined using two dimensional (i.e., vertical wavenumber versus frequency spectra in each season. It was shown that the gravity waves are radiated upward and downward from an unbalanced region of the polar night jet. This feature is consistent with the gravity-wave resolving GCM simulation.

  12. A Comparison Between Gravity Wave Momentum Fluxes in Observations and Climate Models

    Science.gov (United States)

    Geller, Marvin A.; Alexadner, M. Joan; Love, Peter T.; Bacmeister, Julio; Ern, Manfred; Hertzog, Albert; Manzini, Elisa; Preusse, Peter; Sato, Kaoru; Scaife, Adam A.; hide

    2013-01-01

    For the first time, a formal comparison is made between gravity wave momentum fluxes in models and those derived from observations. Although gravity waves occur over a wide range of spatial and temporal scales, the focus of this paper is on scales that are being parameterized in present climate models, sub-1000-km scales. Only observational methods that permit derivation of gravity wave momentum fluxes over large geographical areas are discussed, and these are from satellite temperature measurements, constant-density long-duration balloons, and high-vertical-resolution radiosonde data. The models discussed include two high-resolution models in which gravity waves are explicitly modeled, Kanto and the Community Atmosphere Model, version 5 (CAM5), and three climate models containing gravity wave parameterizations,MAECHAM5, Hadley Centre Global Environmental Model 3 (HadGEM3), and the Goddard Institute for Space Studies (GISS) model. Measurements generally show similar flux magnitudes as in models, except that the fluxes derived from satellite measurements fall off more rapidly with height. This is likely due to limitations on the observable range of wavelengths, although other factors may contribute. When one accounts for this more rapid fall off, the geographical distribution of the fluxes from observations and models compare reasonably well, except for certain features that depend on the specification of the nonorographic gravity wave source functions in the climate models. For instance, both the observed fluxes and those in the high-resolution models are very small at summer high latitudes, but this is not the case for some of the climate models. This comparison between gravity wave fluxes from climate models, high-resolution models, and fluxes derived from observations indicates that such efforts offer a promising path toward improving specifications of gravity wave sources in climate models.

  13. F region manifestation of atmospheric gravity waves at a high magnetic dip station

    International Nuclear Information System (INIS)

    Yeh, K.C.; Dubroff, R.E.; Nagpal, O.P.

    1976-01-01

    An average power spectrum of the observed fluctuations in electron content at Urbana has been computed. Several features of the experimental results can be explained in terms of theoretical models of the ionospheric response to internal gravity waves. An extension of an earlier theory to include the effect of dissipation provides additional justification for the relation between the observed electron content fluctuations and internal gravity waves

  14. Gravitational Wave Polarizations in f (R Gravity and Scalar-Tensor Theory

    Directory of Open Access Journals (Sweden)

    Gong Yungui

    2018-01-01

    Full Text Available The detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory opens a new era to use gravitational waves to test alternative theories of gravity. We investigate the polarizations of gravitational waves in f (R gravity and Horndeski theory, both containing scalar modes. These theories predict that in addition to the familiar + and × polarizations, there are transverse breathing and longitudinal polarizations excited by the massive scalar mode and the new polarization is a single mixed state. It would be very difficult to detect the longitudinal polarization by interferometers, while pulsar timing array may be the better tool to detect the longitudinal polarization.

  15. Acoustic waves in unbounded shear flows

    International Nuclear Information System (INIS)

    Chagelishvili, G.D.; Khujadze, G.R.; Lominadze, J.G.; Rogava, A.D.

    1996-05-01

    The linear evolution of acoustic waves in fluid flow with constant density and uniform shear of velocity is investigated. The process of the mean flow energy extraction by the three-dimensional acoustic waves which is due to the non-normality of linear dynamics in shear flows is analyzed. The thorough examination of the dynamics of different physical quantities, specifying the wave evolution, is outlined. The revealing of the behaviour becomes possible owing to the nonmodal approach that has been extensively used in the study of the perturbations evolution in shear flows since the beginning of the nineties. In addition, a detailed analyses of the physics of shear energy gain by vortex and acoustic perturbations is presented. (author). 28 refs, 7 figs

  16. Stochastic Background of Relic Scalar Gravitational Waves tuned by Extended Gravity

    International Nuclear Information System (INIS)

    De Laurentis, Mariafelicia; Capozziello, Salvatore

    2009-01-01

    A stochastic background of relic gravitational waves is achieved by the so called adiabatically-amplified zero-point fluctuations process derived from early inflation. It provides a distinctive spectrum of relic gravitational waves. In the framework of scalar-tensor gravity, we discuss the scalar modes of gravitational waves and the primordial production of this scalar component which is generated beside tensorial one. Then analyze seven different viable f(R)-gravities towards the Solar System tests and stochastic gravitational waves background. It is demonstrated that seven viable f(R)-gravities under consideration not only satisfy the local tests, but additionally, pass the above PPN-and stochastic gravitational waves bounds for large classes of parameters.

  17. Rayleigh-Taylor Gravity Waves and Quasiperiodic Oscillation Phenomenon in X-ray Binaries

    Science.gov (United States)

    Titarchuk, Lev

    2002-01-01

    Accretion onto compact objects in X-ray binaries (black hole, neutron star (NS), white dwarf) is characterized by non-uniform flow density profiles. Such an effect of heterogeneity in presence of gravitational forces and pressure gradients exhibits Rayleigh-Taylor gravity waves (RTGW). They should be seen as quasiperiodic wave oscillations (QPO) of the accretion flow in the transition (boundary) layer between the Keplerian disk and the central object. In this paper the author shows that the main QPO frequency, which is very close to the Keplerian frequency, is split into separate frequencies (hybrid and low branch) under the influence of the gravitational forces in the rotational frame of reference. The RTGWs must be present and the related QPOs should be detected in any system where the gravity, buoyancy and Coriolis force effects cannot be excluded (even in the Earth and solar environments). The observed low and high QPO frequencies are an intrinsic signature of the RTGW. The author elaborates the conditions for the density profile when the RTGW oscillations are stable. A comparison of the inferred QPO frequencies with QPO observations is presented. The author finds that hectohertz frequencies detected from NS binaries can be identified as the RTGW low branch frequencies. The author also predicts that an observer can see the double NS spin frequency during the NS long (super) burst events when the pressure gradients and buoyant forces are suppressed. The Coriolis force is the only force which acts in the rotational frame of reference and its presence causes perfect coherent pulsations with a frequency twice of the NS spin. The QPO observations of neutron binaries have established that the high QPO frequencies do not go beyond of the certain upper limit. The author explains this observational effect as a result of the density profile inversions. Also the author demonstrates that a particular problem of the gravity waves in the rotational frame of reference in the

  18. Dynamical influence of gravity waves generated by the Vestfjella Mountains in Antarctica: radar observations, fine-scale modelling and kinetic energy budget analysis

    Directory of Open Access Journals (Sweden)

    Joel Arnault

    2012-02-01

    Full Text Available Gravity waves generated by the Vestfjella Mountains (in western Droning Maud Land, Antarctica, southwest of the Finnish/Swedish Aboa/Wasa station have been observed with the Moveable atmospheric radar for Antarctica (MARA during the SWEDish Antarctic Research Programme (SWEDARP in December 2007/January 2008. These radar observations are compared with a 2-month Weather Research Forecast (WRF model experiment operated at 2 km horizontal resolution. A control simulation without orography is also operated in order to separate unambiguously the contribution of the mountain waves on the simulated atmospheric flow. This contribution is then quantified with a kinetic energy budget analysis computed in the two simulations. The results of this study confirm that mountain waves reaching lower-stratospheric heights break through convective overturning and generate inertia gravity waves with a smaller vertical wavelength, in association with a brief depletion of kinetic energy through frictional dissipation and negative vertical advection. The kinetic energy budget also shows that gravity waves have a strong influence on the other terms of the budget, i.e. horizontal advection and horizontal work of pressure forces, so evaluating the influence of gravity waves on the mean-flow with the vertical advection term alone is not sufficient, at least in this case. We finally obtain that gravity waves generated by the Vestfjella Mountains reaching lower stratospheric heights generally deplete (create kinetic energy in the lower troposphere (upper troposphere–lower stratosphere, in contradiction with the usual decelerating effect attributed to gravity waves on the zonal circulation in the upper troposphere–lower stratosphere.

  19. Low-Gravity Mimicking Simulants and Evaluation of Simulant Flow, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This project will provide a new method for testing flow/no-flow conditions and other gravity-driven flow behavior of Lunar or planetary regolith under reduced...

  20. Atmospheric gravity waves observed by an international network of micro-barographs

    International Nuclear Information System (INIS)

    Marty, Julien

    2010-01-01

    The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) manages an international network of forty-two operational infra-sound stations recording the pressure fluctuations produced at the ground surface by infrasonic waves. This thesis demonstrates that most of these stations also accurately detect the pressure fluctuations in the entire gravity wave band. This work includes carrying out and analyzing several metrological laboratory experiments and a field campaign (M2008) in Mongolia in 2008. The layout of the experiments as well as the interpretation of their results gave rise to the development of a new linear spectral numerical model able to simulate the generation and propagation of gravity waves. This model was used to quantify the gravity waves produced by the atmospheric cooling that occurs during solar eclipses. The pressure fluctuations expected at ground level were estimated and compared to the data recorded during the 1 August 2008 solar eclipse by the CTBTO and M2008 stations. A detailed data analysis reveals two waves with similar time-frequency characteristics to those simulated for a stratospheric and tropospheric cooling. This constitutes, to our knowledge, a unique result. The validation of worldwide and pluri-annual pressure measurements in the entire gravity wave band allowed the statistical study of gravity wave spectra and atmospheric tides. The work presented throughout this thesis has led to the publication of two articles. A third one is in the drafting process. (author)

  1. On weakly singular and fully nonlinear travelling shallow capillary–gravity waves in the critical regime

    Energy Technology Data Exchange (ETDEWEB)

    Mitsotakis, Dimitrios, E-mail: dmitsot@gmail.com [Victoria University of Wellington, School of Mathematics, Statistics and Operations Research, PO Box 600, Wellington 6140 (New Zealand); Dutykh, Denys, E-mail: Denys.Dutykh@univ-savoie.fr [LAMA, UMR 5127 CNRS, Université Savoie Mont Blanc, Campus Scientifique, F-73376 Le Bourget-du-Lac Cedex (France); Assylbekuly, Aydar, E-mail: asylbekuly@mail.ru [Khoja Akhmet Yassawi International Kazakh–Turkish University, Faculty of Natural Science, Department of Mathematics, 161200 Turkestan (Kazakhstan); Zhakebayev, Dauren, E-mail: daurjaz@mail.ru [Al-Farabi Kazakh National University, Faculty of Mechanics and Mathematics, Department of Mathematical and Computer Modelling, 050000 Almaty (Kazakhstan)

    2017-05-25

    In this Letter we consider long capillary–gravity waves described by a fully nonlinear weakly dispersive model. First, using the phase space analysis methods we describe all possible types of localized travelling waves. Then, we especially focus on the critical regime, where the surface tension is exactly balanced by the gravity force. We show that our long wave model with a critical Bond number admits stable travelling wave solutions with a singular crest. These solutions are usually referred to in the literature as peakons or peaked solitary waves. They satisfy the usual speed-amplitude relation, which coincides with Scott–Russel's empirical formula for solitary waves, while their decay rate is the same regardless their amplitude. Moreover, they can be of depression or elevation type independent of their speed. The dynamics of these solutions are studied as well. - Highlights: • A model for long capillary–gravity weakly dispersive and fully nonlinear water waves is derived. • Shallow capillary–gravity waves are classified using phase plane analysis. • Peaked travelling waves are found in the critical regime. • The dynamics of peakons in Serre–Green–Naghdi equations is studied numerically.

  2. Low-gravity sensing of liquid/vapor interface and transient liquid flow

    Science.gov (United States)

    Jacobson, Saul A.; Korba, James M.; Lynnworth, Lawrence C.; Nguyen, Toan H.; Orton, George F.

    1987-03-01

    The work reported here deals mainly with tests on internally vaned cylindrical shell acrylic containers capped by hemispherical acrylic or aluminum end domes. Three different ultrasonic sensor techniques and one nucleonic technique presently are evaluated as possible solutions to the low-gravity liquid gauging problem. The ultrasonic techniques are as follows: use of a torsional wave sensor in which transit time is proportional to the integral of wetted distance x liquid density; integration of the flow rate output signal of a fast-response ultrasonic flowmeter; and use of multiplexed externally mounted 'point-sensor' transducers that sense transit times to liquid-gas interfaces. Using two commercial flowmeters and a thickness gauge modified for this particular project, bench tests were conducted at 1 g on liquids such as water, freon, and solvent 140, including both steady flow and pulsating flow with 40, 80, and 120 ms flow pulses. Subsequently, flight tests were conducted in the NASA KC-135 aircraft in which nearly 0-g conditions are obtainable for up to about 5 s in each of a number of repetitive parabolic flight trajectories. In some of these brief low-gravity flight tests freon was replaced with a higher-viscosity fuel to reduce sloshing and thereby obtain settled surfaces more quickly.

  3. Universal power law of the gravity wave manifestation in the AIM CIPS polar mesospheric cloud images

    Science.gov (United States)

    Rong, Pingping; Yue, Jia; Russell, James M., III; Siskind, David E.; Randall, Cora E.

    2018-01-01

    We aim to extract a universal law that governs the gravity wave manifestation in polar mesospheric clouds (PMCs). Gravity wave morphology and the clarity level of display vary throughout the wave population manifested by the PMC albedo data. Higher clarity refers to more distinct exhibition of the features, which often correspond to larger variances and a better-organized nature. A gravity wave tracking algorithm based on the continuous Morlet wavelet transform is applied to the PMC albedo data at 83 km altitude taken by the Aeronomy of Ice in the Mesosphere (AIM) Cloud Imaging and Particle Size (CIPS) instrument to obtain a large ensemble of the gravity wave detections. The horizontal wavelengths in the range of ˜ 20-60 km are the focus of the study. It shows that the albedo (wave) power statistically increases as the background gets brighter. We resample the wave detections to conform to a normal distribution to examine the wave morphology and display clarity beyond the cloud brightness impact. Sample cases are selected at the two tails and the peak of the normal distribution to represent the full set of wave detections. For these cases the albedo power spectra follow exponential decay toward smaller scales. The high-albedo-power category has the most rapid decay (i.e., exponent = -3.2) and corresponds to the most distinct wave display. The wave display becomes increasingly blurrier for the medium- and low-power categories, which hold the monotonically decreasing spectral exponents of -2.9 and -2.5, respectively. The majority of waves are straight waves whose clarity levels can collapse between the different brightness levels, but in the brighter background the wave signatures seem to exhibit mildly turbulent-like behavior.

  4. Atmospheric-like rotating annulus experiment: gravity wave emission from baroclinic jets

    Science.gov (United States)

    Rodda, Costanza; Borcia, Ion; Harlander, Uwe

    2017-04-01

    Large-scale balanced flows can spontaneously radiate meso-scale inertia-gravity waves (IGWs) and are thus in fact unbalanced. While flow-dependent parameterizations for the radiation of IGWs from orographic and convective sources do exist, the situation is less developed for spontaneously emitted IGWs. Observations identify increased IGW activity in the vicinity of jet exit regions. A direct interpretation of those based on geostrophic adjustment might be tempting. However, directly applying this concept to the parameterization of spontaneous imbalance is difficult since the dynamics itself is continuously re-establishing an unbalanced flow which then sheds imbalances by GW radiation. Examining spontaneous IGW emission in the atmosphere and validating parameterization schemes confronts the scientist with particular challenges. Due to its extreme complexity, GW emission will always be embedded in the interaction of a multitude of interdependent processes, many of which are hardly detectable from analysis or campaign data. The benefits of repeated and more detailed measurements, while representing the only source of information about the real atmosphere, are limited by the non-repeatability of an atmospheric situation. The same event never occurs twice. This argues for complementary laboratory experiments, which can provide a more focused dialogue between experiment and theory. Indeed, life cycles are also examined in rotating- annulus laboratory experiments. Thus, these experiments might form a useful empirical benchmark for theoretical and modelling work that is also independent of any sort of subgrid model. In addition, the more direct correspondence between experimental and model data and the data reproducibility makes lab experiments a powerful testbed for parameterizations. Joint laboratory experiment and numerical simulation have been conducted. The comparison between the data obtained from the experiment and the numerical simulations shows a very good

  5. The MaCWAVE program to study gravity wave influences on the polar mesosphere

    Directory of Open Access Journals (Sweden)

    R. A. Goldberg

    2006-07-01

    Full Text Available MaCWAVE (Mountain and Convective Waves Ascending VErtically was a highly coordinated rocket, ground-based, and satellite program designed to address gravity wave forcing of the mesosphere and lower thermosphere (MLT. The MaCWAVE program was conducted at the Norwegian Andøya Rocket Range (ARR, 69.3° N in July 2002, and continued at the Swedish Rocket Range (Esrange, 67.9° N during January 2003. Correlative instrumentation included the ALOMAR MF and MST radars and RMR and Na lidars, Esrange MST and meteor radars and RMR lidar, radiosondes, and TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite measurements of thermal structures. The data have been used to define both the mean fields and the wave field structures and turbulence generation leading to forcing of the large-scale flow. In summer, launch sequences coupled with ground-based measurements at ARR addressed the forcing of the summer mesopause environment by anticipated convective and shear generated gravity waves. These motions were measured with two 12-h rocket sequences, each involving one Terrier-Orion payload accompanied by a mix of MET rockets, all at ARR in Norway. The MET rockets were used to define the temperature and wind structure of the stratosphere and mesosphere. The Terrier-Orions were designed to measure small-scale plasma fluctuations and turbulence that might be induced by wave breaking in the mesosphere. For the summer series, three European MIDAS (Middle Atmosphere Dynamics and Structure rockets were also launched from ARR in coordination with the MaCWAVE payloads. These were designed to measure plasma and neutral turbulence within the MLT. The summer program exhibited a number of indications of significant departures of the mean wind and temperature structures from ``normal" polar summer conditions, including an unusually warm mesopause and a slowing of the formation of polar mesospheric summer echoes (PMSE and noctilucent clouds (NLC. This

  6. Persistent gravity wave coupling from the stratosphere to the MLT versus secondary wave generation in Antarctica

    Science.gov (United States)

    Zhao, J.; Geraghty, I.; Chu, X.; Vadas, S.; Becker, E.; Harvey, V. L.; Jones, R. M.; Chen, C.; Lu, X.

    2017-12-01

    After Antarctic persistent gravity waves (GWs) in the Mesosphere and Lower Thermosphere (MLT) were discovered from lidar observations [Chen et al., 2013, 2016], secondary wave generation theory was proposed to explain the source. Here we perform a source investigation of such persistent GWs through analyzing both stratospheric and MLT GWs at McMurdo using temperature measurements (30 - 50 km, year 2011 - 2015) obtained by Fe Boltzmann lidar. In the stratosphere, GW vertical wavelengths (λ) and periods exhibit seasonal cycles with winter maxima and summer minima, which linearly correlated with mean zonal wind velocities. GWs dissipate more in winter than in summer due to larger wave amplitudes. The potential energy density (Ep) are anti-correlated with wind rotation angles but positively correlated with surface and stratospheric winds. Critical level filtering, in-situ generation of GWs, and wave saturation changes play roles in Ep seasonal variations (winter maxima and summer minima). The large increase of Ep from summer to winter possibly results from the decrease in critical level filtering. The gradual variations of Ep from Mar to Oct are likely related both to the increased λ towards winter, allowing larger wave amplitudes before saturation, and to in-situ GW generation via geostrophic adjustment, secondary GW generation. Large Ep occur when McMurdo is inside the jet stream core 5-24º poleward from vortex edge. In winter MLT, the persistent GWs cause larger temperature perturbations (± 30 K, compared to ± 10 K in the stratosphere) with longer λ (23.5 km) and larger vertical phase speeds (1.8 m/s). More waves (95.4%) show downward phase progression compared to the stratospheric GWs (70.4%). Since the inferred horizontal wavelength of stratospheric GWs (350 - 450 km) are much shorter than those of the persistent GWs in the MLT (1000 - 2000 km), the dominant stratospheric GWs are not the direct source of the MLT persistent GWs. Secondary wave generation

  7. Observation of gravity waves during the extreme tornado outbreak of 3 April 1974

    Science.gov (United States)

    Hung, R. J.; Phan, T.; Smith, R. E.

    1978-01-01

    A continuous wave-spectrum high-frequency radiowave Doppler sounder array was used to observe upper-atmospheric disturbances during an extreme tornado outbreak. The observations indicated that gravity waves with two harmonic wave periods were detected at the F-region ionospheric height. Using a group ray path computational technique, the observed gravity waves were traced in order to locate potential sources. The signals were apparently excited 1-3 hours before tornado touchdown. Reverse ray tracing indicated that the wave source was located at the aurora zone with a Kp index of 6 at the time of wave excitation. The summation of the 24-hour Kp index for the day was 36. The results agree with existing theories (Testud, 1970; Titheridge, 1971; Kato, 1976) for the excitation of large-scale traveling ionospheric disturbances associated with geomagnetic activity in the aurora zone.

  8. Inertia-gravity waves in the troposphere and lower stratosphere associated with a jet stream exit region

    Directory of Open Access Journals (Sweden)

    L. Thomas

    Full Text Available Radar measurements at Aberystwyth (52.4° N, 4.1° W of winds at tropospheric and lower stratospheric heights are shown for 12-13 March 1994 in a region of highly curved flow, downstream of the jet maximum. The perturbations of horizontal velocity have comparable amplitudes in the troposphere and lower stratosphere with downward and upward phase propagation, respectively, in these two height regions. The sense of rotation with increasing height in hodographs of horizontal perturbation velocity derived for hourly intervals show downwards propagation of energy in the troposphere and upward propagation in the lower stratosphere with vertical wavelengths of 1.7 to 2.3 km. The results indicate inertia-gravity waves propagating in a direction similar to that of the jet stream but at smaller velocities. Some of the features observed contrast with those of previous observations of inertia-gravity waves propagating transverse to the jet stream. The interpretation of the hodographs to derive wave parameters has taken account of the vertical shear of the background wind transverse to the direction of wave propagation.

    Key words. Meteorology and atmospheric dynamics (mesoscale meteorology; middle atmosphere dynamics; waves and tides

  9. Study of gravity waves propagation in the thermosphere of Mars based on MAVEN/NGIMS density measurements

    Science.gov (United States)

    Vals, M.

    2017-09-01

    We use MAVEN/NGIMS CO2 density measurements to analyse gravity waves in the thermosphere of Mars. In particular the seasonal/latitudinal variability of their amplitude is studied and interpreted. Key background parameters controlling the activity of gravity waves are analysed with the help of the Mars Climate Database (MCD). Gravity waves activity presents a good anti-correlation to the temperature variability retrieved from the MCD. An analysis at pressure levels is ongoing.

  10. Improved analysis of all-sky meteor radar measurements of gravity wave variances and momentum fluxes

    Directory of Open Access Journals (Sweden)

    V. F. Andrioli

    2013-05-01

    Full Text Available The advantages of using a composite day analysis for all-sky interferometric meteor radars when measuring mean winds and tides are widely known. On the other hand, problems arise if this technique is applied to Hocking's (2005 gravity wave analysis for all-sky meteor radars. In this paper we describe how a simple change in the procedure makes it possible to use a composite day in Hocking's analysis. Also, we explain how a modified composite day can be constructed to test its ability to measure gravity wave momentum fluxes. Test results for specified mean, tidal, and gravity wave fields, including tidal amplitudes and gravity wave momentum fluxes varying strongly with altitude and/or time, suggest that the modified composite day allows characterization of monthly mean profiles of the gravity wave momentum fluxes, with good accuracy at least at the altitudes where the meteor counts are large (from 89 to 92.5 km. In the present work we also show that the variances measured with Hocking's method are often contaminated by the tidal fields and suggest a method of empirical correction derived from a simple simulation model. The results presented here greatly increase our confidence because they show that our technique is able to remove the tide-induced false variances from Hocking's analysis.

  11. Dynamics of Nearshore Sand Bars and Infra-gravity Waves: The Optimal Theory Point of View

    Science.gov (United States)

    Bouchette, F.; Mohammadi, B.

    2016-12-01

    It is well known that the dynamics of near-shore sand bars are partly controlled by the features (location of nodes, amplitude, length, period) of the so-called infra-gravity waves. Reciprocally, changes in the location, size and shape of near-shore sand bars can control wave/wave interactions which in their turn alter the infra-gravity content of the near-shore wave energy spectrum. The coupling infra-gravity / near-shore bar is thus definitely two ways. Regarding numerical modelling, several approaches have already been considered to analyze such coupled dynamics. Most of them are based on the following strategy: 1) define an energy spectrum including infra-gravity, 2) tentatively compute the radiation stresses driven by this energy spectrum, 3) compute sediment transport and changes in the seabottom elevation including sand bars, 4) loop on the computation of infra-gravity taking into account the morphological changes. In this work, we consider an alternative approach named Nearshore Optimal Theory, which is a kind of breakdown point of view for the modeling of near-shore hydro-morphodynamics and wave/ wave/ seabottom interactions. Optimal theory applied to near-shore hydro-morphodynamics arose with the design of solid coastal defense structures by shape optimization methods, and is being now extended in order to model dynamics of any near-shore system combining waves and sand. The basics are the following: the near-shore system state is through a functional J representative of the energy of the system in some way. This J is computed from a model embedding the physics to be studied only (here hydrodynamics forced by simple infra-gravity). Then the paradigm is to say that the system will evolve so that the energy J tends to minimize. No really matter the complexity of wave propagation nor wave/bottom interactions. As soon as J embeds the physics to be explored, the method does not require a comprehensive modeling. Near-shore Optimal Theory has already given

  12. Experimental study of the propgation and dispersion of internal atmospheric gravity waves

    International Nuclear Information System (INIS)

    Ballard, K.A.

    1981-01-01

    Traveling ionospheric disturbances (TID's) appear as large-scale transverse waves in the F-region (150 to 1000 km altitude), with frequencies on the order of 0.005 to 0.005 cycles per minute, which propagate horizontally over hundreds or even thousands of kilometers. These disturbances have been observed by various radiowave techniques over the past thirty-five years and are now generally accepted as being the manifestation, in the ionized medium, of internal atmospheric gravity waves. A model describing the propagation of gravity waves in an isothermal atmosphere is presented here. The dispersion relation is derived from fundamental principles, and the relation between phase velocity and group velocity is examined. The effects of the Coriolis force and horizontally stratified winds on wave propagation are also analyzed. Conservation of energy in the gravity wave requires increasing amplitude with increasing altitude, inasmuch as the atmospheric density decreases with height. However, this is counteracted by dissipation of wave energy by ion drag, thermal conductivity, and viscous damping. The production of TID's (in the ionized medium) by gravity waves (in the neutral medium) is discussed in quantitative terms, and the vertical predictive function is derived. Dartmouth College has operated a three-station ionosonde network in northern New Hampshire and Vermont on an intermittent basis since 1968. Seven large TID's, found in the 1969 data, are reexamined here in an exhaustive and successful comparison with the gravity wave model. Iso-true-height contours of electron density are used to determine several pertinent TID wave parameters as a function of height

  13. Sensitivity of Middle Atmospheric Temperature and Circulation in the UIUC Mesosphere-Stratosphere-Troposphere GCM to the Treatment of Subgrid-Scale Gravity-Wave Breaking

    Science.gov (United States)

    Yang, Fanglin; Schlesinger, Michael E.; Andranova, Natasha; Zubov, Vladimir A.; Rozanov, Eugene V.; Callis, Lin B.

    2003-01-01

    The sensitivity of the middle atmospheric temperature and circulation to the treatment of mean- flow forcing due to breaking gravity waves was investigated using the University of Illinois at Urbana-Champaign 40-layer Mesosphere-Stratosphere-Troposphere General Circulation Model (MST-GCM). Three GCM experiments were performed. The gravity-wave forcing was represented first by Rayleigh friction, and then by the Alexander and Dunkerton (AD) parameterization with weak and strong breaking effects of gravity waves. In all experiments, the Palmer et al. parameterization was included to treat the breaking of topographic gravity waves in the troposphere and lower stratosphere. Overall, the experiment with the strong breaking effect simulates best the middle atmospheric temperature and circulation. With Rayleigh friction and the weak breaking effect, a large warm bias of up to 60 C was found in the summer upper mesosphere and lower thermosphere. This warm bias was linked to the inability of the GCM to simulate the reversal of the zonal winds from easterly to westerly crossing the mesopause in the summer hemisphere. With the strong breaking effect, the GCM was able to simulate this reversal, and essentially eliminated the warm bias. This improvement was the result of a much stronger meridional transport circulation that possesses a strong vertical ascending branch in the summer upper mesosphere, and hence large adiabatic cooling. Budget analysis indicates that 'in the middle atmosphere the forces that act to maintain a steady zonal-mean zonal wind are primarily those associated with the meridional transport circulation and breaking gravity waves. Contributions from the interaction of the model-resolved eddies with the mean flow are small. To obtain a transport circulation in the mesosphere of the UIUC MST-GCM that is strong enough to produce the observed cold summer mesopause, gravity-wave forcing larger than 100 m/s/day in magnitude is required near the summer mesopause. In

  14. The Role of Gravity Waves in the Formation and Organization of Clouds during TWPICE

    Energy Technology Data Exchange (ETDEWEB)

    Reeder, Michael J. [Monash University; Lane, Todd P. [University of Melbourne; Hankinson, Mai Chi Nguyen [Monash University

    2013-09-27

    All convective clouds emit gravity waves. While it is certain that convectively-generated waves play important parts in determining the climate, their precise roles remain uncertain and their effects are not (generally) represented in climate models. The work described here focuses mostly on observations and modeling of convectively-generated gravity waves, using the intensive observations from the DoE-sponsored Tropical Warm Pool International Cloud Experiment (TWP-ICE), which took place in Darwin, from 17 January to 13 February 2006. Among other things, the research has implications the part played by convectively-generated gravity waves in the formation of cirrus, in the initiation and organization of further convection, and in the subgrid-scale momentum transport and associated large-scale stresses imposed on the troposphere and stratosphere. The analysis shows two groups of inertia-gravity waves are detected: group L in the middle stratosphere during the suppressed monsoon period, and group S in the lower stratosphere during the monsoon break period. Waves belonging to group L propagate to the south-east with a mean intrinsic period of 35 h, and have vertical and horizontal wavelengths of about 5-6 km and 3000-6000 km, respectively. Ray tracing calculations indicate that these waves originate from a deep convective region near Indonesia. Waves belonging to group S propagate to the south-south-east with an intrinsic period, vertical wavelength and horizontal wavelength of about 45 h, 2 km and 2000-4000 km, respectively. These waves are shown to be associated with shallow convection in the oceanic area within about 1000 km of Darwin. The intrinsic periods of high-frequency waves are estimated to be between 20-40 minutes. The high-frequency wave activity in the stratosphere, defined by mass-weighted variance of the vertical motion of the sonde, has a maximum following the afternoon local convection indicating that these waves are generated by local convection

  15. Relic gravitational wave spectrum, the trans-Planckian physics and Horava-Lifshitz gravity

    International Nuclear Information System (INIS)

    Koh, Seoktae

    2010-01-01

    We calculate the spectrum of the relic gravitational wave due to the trans-Planckian effect in which the standard linear dispersion relations may be modified. Of the modified dispersion relations suggested in the literature which has investigated the trans-Planckian effect, we especially use the Corley-Jacobson dispersion relations. The Corley-Jacobson-type modified dispersion relations can be obtained from Horava-Lifshitz gravity which is non-relativistic and UV complete. Although it is not clear how the transitions from Horava-Lifshitz gravity in the UV regime to Einstein gravity in the IR limit occur, we assume that the Horava-Lifshitz gravity regime is followed by the inflationary phase in Einstein gravity.

  16. Stoneley waves in a non-homogeneous orthotropic granular medium under the influence of gravity

    Directory of Open Access Journals (Sweden)

    S. M. Ahmed

    2005-01-01

    Full Text Available The aim of this paper is to investigate the Stoneley waves in a non-homogeneous orthotropic granular medium under the influence of a gravity field. The frequency equation obtained, in the form of a sixth-order determinantal expression, is in agreement with the corresponding result when both media are elastic. The frequency equation when the gravity field is neglected has been deduced as a particular case.

  17. Plane wave fast color flow mode imaging

    DEFF Research Database (Denmark)

    Bolic, Ibrahim; Udesen, Jesper; Gran, Fredrik

    2006-01-01

    A new Plane wave fast color flow imaging method (PWM) has been investigated, and performance evaluation of the PWM based on experimental measurements has been made. The results show that it is possible to obtain a CFM image using only 8 echo-pulse emissions for beam to flow angles between 45...... degrees and 75 degrees. Compared to the conventional ultrasound imaging the frame rate is similar to 30 - 60 times higher. The bias, B-est of the velocity profile estimate, based on 8 pulse-echo emissions, is between 3.3% and 6.1% for beam to flow angles between 45 degrees and 75 degrees, and the standard...

  18. Effects of gravity and planetary waves on the lower ionosphere as obtained from radio wave absorption measurements

    Czech Academy of Sciences Publication Activity Database

    Laštovička, Jan

    2001-01-01

    Roč. 26, 6, Part C (2001), s. 381-386 ISSN 1464-1917 R&D Projects: GA AV ČR IBS3012007; GA AV ČR IAA3042102; GA MŠk OC 271.10 Institutional research plan: CEZ:AV0Z3042911 Keywords : planetary wave * gravity wave * lower ionosphere Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.399, year: 2001

  19. Gravity flow and solute dispersion in variably saturated sand

    Science.gov (United States)

    Kumahor, Samuel K.; de Rooij, Gerrit H.; Vogel, Hans-Joerg

    2014-05-01

    Solute dispersion in porous media depends on the structure of the velocity field at the pore scale. Hence, dispersion is expected to change with water content and with mean flow velocity. We performed laboratory experiments using a column of repacked fine-grained quartz sand (0.1-0.3 mm grain size) with a porous plate at the bottom to controle the water potential at the lower boundary. We established gravity flow conditions - i.e. constant matric potential and water content throughout the column - for a number of different irrigation rates. We measured breakthrough curves during unit gradient flow for an inert tracer which could be described by the convection-dispersion equation. As the soil water content decreased we observed an initially gradual increase in dispersivity followed by an abrupt increase below a threshold water content (0.19) and pressure head (-38 hPa). This phenomena can be explained by the geometry of phase distribution which was simulated based on Xray-CT images of the porous structure.

  20. The Atmospheric Waves Experiment (AWE): Quantifying the Impact of Gravity Waves on the Edge of Space

    Science.gov (United States)

    Taylor, M. J.; Forbes, J. M.; Fritts, D. C.; Eckermann, S. D.; Snively, J. B.; Liu, H.; Janches, D.; Syrstad, E. A.; Esplin, R. W.; Pautet, P. D.; Zhao, Y.; Pendleton, W. R.

    2017-12-01

    New theory and modeling now indicate that upward-propagating gravity waves (GWs) originating in the lower atmosphere have profound effects on the variability and mean state of the ionosphere-thermosphere-mesosphere (ITM) system. A major unknown is the spectrum of small-scale ( 30-300 km) GWs entering this system from below. Yet, this part of the spectrum contains most of the waves that will produce the greatest ITM effects. To address this knowledge gap, the Atmospheric Waves Experiment (AWE) plans to deploy a high-resolution imager (based on the successful Utah State University Advanced Mesospheric Temperature Mapper) on the International Space Station (ISS) to gain a transformative set of GW-resolving temperature measurements using the OH nightglow emission (altitude 87 km). The ISS provides the ideal combination of altitude, geographic and local time coverage to accomplish our proposed science objectives, which seeks not only near-global measurements of GW characteristics in the mesopause region, but also quantification of GW momentum and energy fluxes driving the IT from below. Combined with state-of-the-art high-resolution models, the AWE mission will also assess the relative importance of sources versus propagation conditions in explaining the observed spatial and temporal variability of the GWs. The AWE mission was recently selected for a "Phase A" study as part of the NASA 2016 Heliophysics Explorers Mission of Opportunity (MO) Program. In this presentation, we describe the primary goals of this program and introduce our proposed research methods using proven IR instrument technology. AWE's exceptional capabilities are illustrated with recent discoveries in observing GWs from the ground and from aircraft during the NSF DEEPWAVE campaign, promising a major step forward in understanding how troposphere weather translates to space weather.

  1. Surface-acoustic-wave (SAW) flow sensor

    Science.gov (United States)

    Joshi, Shrinivas G.

    1991-03-01

    The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 deg rotated Y-cut lithium niobate substrate and heated to 55 C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cu cm/min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.

  2. Quintessential inflation on the brane and the relic gravity wave background

    International Nuclear Information System (INIS)

    Sami, M.; Sahni, V.

    2004-01-01

    Quintessential inflation describes a scenario in which both inflation and dark energy (quintessence) are described by the same scalar field. In conventional braneworld models of quintessential inflation gravitational particle-production is used to reheat the universe. This reheating mechanism is very inefficient and results in an excessive production of gravity waves which violate nucleosynthesis constraints and invalidate the model. We describe a new method of realizing quintessential inflation on the brane in which inflation is followed by 'instant preheating' (Felder, Kofman and Linde 1999). The larger reheating temperature in this model results in a smaller amplitude of relic gravity waves which is consistent with nucleosynthesis bounds. The relic gravity wave background has a 'blue' spectrum at high frequencies and is a generic byproduct of successful quintessential inflation on the brane

  3. Investigating Gravity Waves in Polar Mesospheric Clouds Using Tomographic Reconstructions of AIM Satellite Imagery

    Science.gov (United States)

    Hart, V. P.; Taylor, M. J.; Doyle, T. E.; Zhao, Y.; Pautet, P.-D.; Carruth, B. L.; Rusch, D. W.; Russell, J. M.

    2018-01-01

    This research presents the first application of tomographic techniques for investigating gravity wave structures in polar mesospheric clouds (PMCs) imaged by the Cloud Imaging and Particle Size instrument on the NASA AIM satellite. Albedo data comprising consecutive PMC scenes were used to tomographically reconstruct a 3-D layer using the Partially Constrained Algebraic Reconstruction Technique algorithm and a previously developed "fanning" technique. For this pilot study, a large region (760 × 148 km) of the PMC layer (altitude 83 km) was sampled with a 2 km horizontal resolution, and an intensity weighted centroid technique was developed to create novel 2-D surface maps, characterizing the individual gravity waves as well as their altitude variability. Spectral analysis of seven selected wave events observed during the Northern Hemisphere 2007 PMC season exhibited dominant horizontal wavelengths of 60-90 km, consistent with previous studies. These tomographic analyses have enabled a broad range of new investigations. For example, a clear spatial anticorrelation was observed between the PMC albedo and wave-induced altitude changes, with higher-albedo structures aligning well with wave troughs, while low-intensity regions aligned with wave crests. This result appears to be consistent with current theories of PMC development in the mesopause region. This new tomographic imaging technique also provides valuable wave amplitude information enabling further mesospheric gravity wave investigations, including quantitative analysis of their hemispheric and interannual characteristics and variations.

  4. The Effect of Aerosol on Gravity Wave Characteristics above the Boundary Layer over a Tropical Location

    Science.gov (United States)

    Rakshit, G.; Jana, S.; Maitra, A.

    2017-12-01

    The perturbations of temperature profile over a location give an estimate of the potential energy of gravity waves propagating through the atmosphere. Disturbances in the lower atmosphere due to tropical deep convection, orographic effects and various atmospheric disturbances generates of gravity waves. The present study investigates the gravity wave energy estimated from fluctuations in temperature profiles over the tropical location Kolkata (22°34' N, 88°22' E). Gravity waves are most intense during the pre-monsoon period (March-June) at the present location, the potential energy having high values above the boundary layer (2-4 km) as observed from radiosonde profiles. An increase in temperature perturbation, due to high ambient temperature in the presence of heat absorbing aerosols, causes an enhancement in potential energy. As the present study location is an urban metropolitan city experiencing high level of pollution, pollutant aerosols can go much above the normal boundary layer during daytime due to convection causing an extended boundary layer. The Aerosol Index (AAI) obtained from Global Ozone Monitoring Experiment-2 (GOME-2) on MetOp-A platform at 340 nm and 380 nm confirms the presence of absorbing aerosol particles over the present location. The Hysplit back trajectory analysis shows that the aerosol particles at those heights are of local origin and are responsible for depleting liquid water content due to cloud burning. The aerosol extinction coefficient obtained from CALIPSO data exhibits an increasing trend during 2006-2016 accompanied by a similar pattern of gravity wave energy. Thus the absorbing aerosols have a significant role in increasing the potential energy of gravity wave at an urban location in the tropical region.

  5. Atmospheric gravity wave detection following the 2011 Tohoku earthquakes combining COSMIC occultation and GPS observations

    Science.gov (United States)

    Yan, X.; Tao, Y.; Xia, C.; Qi, Y.; Zuo, X.

    2017-12-01

    Several studies have reported the earthquake-induced atmospheric gravity waves detected by some new technologies such as airglow (Makela et al., 2011), GOCE (Garcia et al., 2013), GRACE (Yang et al., 2014), F3/C radio occultation sounding (Coïsson et al., 2015). In this work, we collected all occultation events on 11 March, and selected four events to analyze at last. The original and filtered podTEC is represented as function of the altitude of the impact parameter and UT of the four events. Then, the travel time diagrams of filtered podTEC derived from the events were analyzed. The occultation signal from one event (marked as No.73) is consistent with the previous results reported by Coïsson. 2015, which is corresponds to the ionospheric signal induced from tsunami gravity wave. What is noticeable, in this work, is that three occultation events of No.403, 77 and 118 revealed a disturbance of atmospheric gravity wave with velocity 300m/s, preceding the tsunami. It would probably be correspond to the gravity waves caused by seismic rupture but not tsunami. In addition, it can be seen that the perturbation height of occultation observation TEC is concentrated at 200-400km, corresponding ionosphere F region. The signals detected above are compared with GPS measurements of TEC from GEONET and IGS. From GPS data, traveling ionospheric disturbances were observed spreading out from the epicenter as a quasi-circular propagation pattern with the time. Exactly, we observed an acoustic wave coupled with Rayleigh wave starting from the epicenter with a speed of 3.0km/s and a superimposed acoustic-gravity wave moving with a speed of 800m/s. The acoustic-gravity wave generated at the epicenter and gradually attenuated 800km away, then it is replaced by a gravity wave coupled with the tsunami that moves with a speed of between 100 and 300m/s. It is necessary to confirm the propagation process of the waves if we attempt to evaluate the use of ionospheric seismology as a

  6. A Study of Mesoscale Gravity Waves over the North Atlantic with Satellite Observations and a Mesoscale Model

    Science.gov (United States)

    Wu, Dong L.; Zhang, Fuqing

    2004-01-01

    Satellite microwave data are used to study gravity wave properties and variabilities over the northeastern United States and the North Atlantic in the December-January periods. The gravity waves in this region, found in many winters, can reach the stratopause with growing amplitude. The Advanced Microwave Sounding Unit-A (AMSU-A) observations show that the wave occurrences are correlated well with the intensity and location of the tropospheric baroclinic jet front systems. To further investigate the cause(s) and properties of the North Atlantic gravity waves, we focus on a series of wave events during 19-21 January 2003 and compare AMSU-A observations to simulations from a mesoscale model (MM5). The simulated gravity waves compare qualitatively well with the satellite observations in terms of wave structures, timing, and overall morphology. Excitation mechanisms of these large-amplitude waves in the troposphere are complex and subject to further investigations.

  7. Homogeneous wave turbulence driven by tidal flows

    Science.gov (United States)

    Favier, B.; Le Reun, T.; Barker, A.; Le Bars, M.

    2017-12-01

    When a moon orbits around a planet, the rotation of the induced tidal bulge drives a homogeneous, periodic, large-scale flow. The combination of such an excitation with the rotating motion of the planet has been shown to drive parametric resonance of a pair of inertial waves in a mechanism called the elliptical instability. Geophysical fluid layers can also be stratified: this is the case for instance of the Earth's oceans and, as suggested by several studies, of the upper part of the Earth's liquid Outer Core. We thus investigate the stability of a rotating and stratified layer undergoing tidal distortion in the limit where either rotation or stratification is dominant. We show that the periodic tidal flow drives a parametric subharmonic resonance of inertial (resp. internal) waves in the rotating (resp. stratified) case. The instability saturates into a wave turbulence pervading the whole fluid layer. In such a state, the instability mechanism conveys the tidal energy from the large scale tidal flow to the resonant modes, which then feed a succession of triadic resonances also generating small spatial scales. In the rotating case, we observe a kinetic energy spectrum with a k-2 slope for which the Coriolis force is dominant at all spatial scales. In the stratified case, where the timescale separation is increased between the tidal excitation and the Brunt-Väisälä frequencies, the temporal spectrum decays with a ω-2 power law up to the cut-off frequency beyond which waves do not exist. This result is reminiscent of the Garrett and Munk spectrum measured in the oceans and theoretically described as a manifestation of internal wave turbulence. In addition to revealing an instability driving homogeneous turbulence in geophysical fluid layers, our approach is also an efficient numerical tool to investigate the possibly universal properties of wave turbulence in a geophysical context.

  8. Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow

    International Nuclear Information System (INIS)

    Yu Tsvelodub, O

    2016-01-01

    The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. Weakly nonlinear steady-state traveling solutions of the equation with wave numbers in a vicinity of neutral wave numbers are constructed analytically. The nature of the wave branching from the undisturbed solution is investigated. Steady-state traveling solutions, whose wave numbers within the instability area are far from neutral wave numbers, are found numerically. (paper)

  9. Tidal and gravity waves study from the airglow measurements at ...

    Indian Academy of Sciences (India)

    E) during the period 2004–2007 are analyzed to study the dominant waves present in the 80–100 km altitude region of the atmosphere. The nocturnal intensity variations of different airglow emissions are observed using scanning temperature controlled filter photometers. Waves having period lying between 2 and 12 hours ...

  10. Geometric controls of the flexural gravity waves on the Ross Ice Shelf

    Science.gov (United States)

    Sergienko, O. V.

    2017-12-01

    Long-period ocean waves, formed locally or at distant sources, can reach sub-ice-shelf cavities and excite coupled motion in the cavity and the ice shelf - flexural gravity waves. Three-dimensional numerical simulations of the flexural gravity waves on the Ross Ice Shelf show that propagation of these waves is strongly controlled by the geometry of the system - the cavity shape, its water-column thickness and the ice-shelf thickness. The results of numerical simulations demonstrate that propagation of the waves is spatially organized in beams, whose orientation is determined by the direction of the of the open ocean waves incident on the ice-shelf front. As a result, depending on the beams orientation, parts of the Ross Ice Shelf experience significantly larger flexural stresses compared to other parts where the flexural gravity beams do not propagate. Very long-period waves can propagate farther away from the ice-shelf front exciting flexural stresses in the vicinity of the grounding line.

  11. On the Dynamics of Two-Dimensional Capillary-Gravity Solitary Waves with a Linear Shear Current

    Directory of Open Access Journals (Sweden)

    Dali Guo

    2014-01-01

    Full Text Available The numerical study of the dynamics of two-dimensional capillary-gravity solitary waves on a linear shear current is presented in this paper. The numerical method is based on the time-dependent conformal mapping. The stability of different kinds of solitary waves is considered. Both depression wave and large amplitude elevation wave are found to be stable, while small amplitude elevation wave is unstable to the small perturbation, and it finally evolves to be a depression wave with tails, which is similar to the irrotational capillary-gravity waves.

  12. Nonlinear internal gravity waves and their interaction with the mean wind

    International Nuclear Information System (INIS)

    Grimshaw, R.

    1975-01-01

    The interaction of a wave packet of internal gravity waves with the mean wind is investigated, for the case when there is a region of wind shear and hence a critical level. The principal equations are the Doppler-shifted dispersion relation, the equation for conservation of wave action and the mean momentum equation, in which the mean wind is accelerated by a 'radiation stress' tensor, due to the waves. These equations are integrated numerically to study the behaviour of a wave packet approaching a critical level, where the horizontal phase speed matches the mean wind. The results demonstrate the exchange of energy from the waves to the mean wind in the vicinity of the critical level. The interaction between the waves and the mean wind is also studied in the absence of any initial wind shear. (author)

  13. Asymptotic expansions for solitary gravity-capillary waves in two and three dimensions

    International Nuclear Information System (INIS)

    Ablowitz, M J; Haut, T S

    2010-01-01

    High-order asymptotic series are obtained for gravity-capillary solitary waves, where the first term in the series is the well-known sech 2 solution of the KdV equation. The asymptotic series is used, with nine terms included, to investigate the effects of surface tension on the height and energy of large amplitude waves, and waves close to the solitary version of Stokes' extreme wave. In particular, for surface tension below a critical value, the solitary wave with the maximum energy is obtained. For large surface tension, the series is also used to study the energy related to the solitary waves of depression. Energy considerations suggest that, for large enough surface tension, there are solitary waves that can get close to the fluid bottom. Comparisons are also made with recent experiments.

  14. Effect of Gravity Waves from Small Islands in the Southern Ocean on the Southern Hemisphere Atmospheric Circulation

    Science.gov (United States)

    Garfinkel, C. I.; Oman, L. D.

    2018-01-01

    The effect of small islands in the Southern Ocean on the atmospheric circulation in the Southern Hemisphere is considered with a series of simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model in which the gravity wave stress generated by these islands is increased to resemble observed values. The enhanced gravity wave drag leads to a 2 K warming of the springtime polar stratosphere, partially ameliorating biases in this region. Resolved wave drag declines in the stratospheric region in which the added orographic gravity waves deposit their momentum, such that changes in gravity waves are partially compensated by changes in resolved waves, though resolved wave drag increases further poleward. The orographic drag from these islands has impacts for surface climate, as biases in tropospheric jet position are also partially ameliorated. These results suggest that these small islands are likely contributing to the missing drag near 60 degrees S in the upper stratosphere evident in many data assimilation products.

  15. Analytical and numerical investigation of nonlinear internal gravity waves

    Directory of Open Access Journals (Sweden)

    S. P. Kshevetskii

    2001-01-01

    Full Text Available The propagation of long, weakly nonlinear internal waves in a stratified gas is studied. Hydrodynamic equations for an ideal fluid with the perfect gas law describe the atmospheric gas behaviour. If we neglect the term Ͽ dw/dt (product of the density and vertical acceleration, we come to a so-called quasistatic model, while we name the full hydro-dynamic model as a nonquasistatic one. Both quasistatic and nonquasistatic models are used for wave simulation and the models are compared among themselves. It is shown that a smooth classical solution of a nonlinear quasistatic problem does not exist for all t because a gradient catastrophe of non-linear internal waves occurs. To overcome this difficulty, we search for the solution of the quasistatic problem in terms of a generalised function theory as a limit of special regularised equations containing some additional dissipation term when the dissipation factor vanishes. It is shown that such solutions of the quasistatic problem qualitatively differ from solutions of a nonquasistatic nature. It is explained by the fact that in a nonquasistatic model the vertical acceleration term plays the role of a regularizator with respect to a quasistatic model, while the solution qualitatively depends on the regularizator used. The numerical models are compared with some analytical results. Within the framework of the analytical model, any internal wave is described as a system of wave modes; each wave mode interacts with others due to equation non-linearity. In the principal order of a perturbation theory, each wave mode is described by some equation of a KdV type. The analytical model reveals that, in a nonquasistatic model, an internal wave should disintegrate into solitons. The time of wave disintegration into solitons, the scales and amount of solitons generated are important characteristics of the non-linear process; they are found with the help of analytical and numerical investigations. Satisfactory

  16. Locating the Tohoku-Oki 2011 tsunami source using acoustic-gravity waves

    OpenAIRE

    Andriamiranto Raveloson; Rainer Kind; Xiaohui Yuan; L. Cerana

    2012-01-01

    The giant Tohoku-Oki earthquake of 11 March 2011 in offshore Japan did not only generate tsunami waves in the ocean but also infrasound (or acoustic-gravity) waves in the atmosphere. We indentified ultra-long-period signals (>500s) in the recordings of infrasound stations in northeast Asia, the northwest Pacific, and Alaska. Their source was fond close to the earthquake epicenter. Therefore, we conclude that in general, infrasound observations after a large offshore earthquake are evidence th...

  17. Horizontal velocities and propagation directions of gravity waves in the ionosphere over the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Chum, Jaroslav; Šindelářová, Tereza; Laštovička, Jan; Hruška, František; Burešová, Dalia; Baše, Jiří

    2010-01-01

    Roč. 115, - (2010), A11322/1-A11322/13 ISSN 0148-0227 R&D Projects: GA ČR GA205/07/1367; GA ČR GA205/09/1253 Grant - others:AV ČR(CZ) M100420901 Institutional research plan: CEZ:AV0Z30420517 Keywords : Ionosphere * gravity waves * wave propagation * remote sensing Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.303, year: 2010

  18. Acoustic–gravity waves during solar eclipses: Detection and characterization using wavelet transforms

    Czech Academy of Sciences Publication Activity Database

    Šauli, Petra; Roux, S. G.; Abry, P.; Boška, Josef

    2007-01-01

    Roč. 69, 17-18 (2007), s. 2465-2484 ISSN 1364-6826 R&D Projects: GA ČR GA205/06/1619; GA AV ČR IAA300420504 Grant - others:CNRS(FR) 18098 Institutional research plan: CEZ:AV0Z30420517 Keywords : Acoustic–gravity wave * Vertical ionospheric sounding * F-layer * Wavelet transform * Wave-packet characterization Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.566, year: 2007

  19. Convective cells of internal gravity waves in the earth's atmosphere with finite temperature gradient

    Directory of Open Access Journals (Sweden)

    O. Onishchenko

    2013-03-01

    Full Text Available In this paper, we have investigated vortex structures (e.g. convective cells of internal gravity waves (IGWs in the earth's atmosphere with a finite vertical temperature gradient. A closed system of nonlinear equations for these waves and the condition for existence of solitary convective cells are obtained. In the atmosphere layers where the temperature decreases with height, the presence of IGW convective cells is shown. The typical parameters of such structures in the earth's atmosphere are discussed.

  20. Secondary Flows and Sediment Transport due to Wave - Current Interaction

    Science.gov (United States)

    Ismail, Nabil; Wiegel, Robert

    2015-04-01

    Objectives: The main purpose of this study is to determine the modifications of coastal processes driven by wave-current interaction and thus to confirm hydrodynamic mechanisms associated with the interaction at river mouths and tidal inlets where anthropogenic impacts were introduced. Further, the aim of the work has been to characterize the effect of the relative strength of momentum action of waves to the opposing current on the nearshore circulation where river flow was previously effective to entrain sediments along the shoreline. Such analytical information are useful to provide guidelines for sustainable design of coastal defense structures. Methodology and Analysis: Use is made of an earlier study reported by the authors (1983) on the interaction of horizontal momentum jets and opposing shallow water waves at shorelines, and of an unpublished laboratory study (1980). The turbulent horizontal discharge was shore-normal, directed offshore, and the incident wave direction was shore-normal, travelling toward shore. Flow visualization at the smooth bottom and the water surface, velocity and water surface elevation measurements were made. Results were obtained for wave , current modifications as well as the flow pattern in the jet and the induced circulation on both sides of the jet, for a range of wave and jet characteristics. The experimental data, obtained from measurement in the 3-D laboratory basin, showed several distinct flow pattern regimes on the bottom and the water surface. The observed flow circulation regimes were found to depend on the ratio of the wave momentum action on the jet to the jet initial momentum. Based on the time and length scales of wave and current parameters and using the time average of the depth integrated conservation equations, it is found that the relative strength of the wave action on the jet could be represented by a dimensionless expression; Rsm ( ) 12ρSa20g-L0h-Cg- 2 Rsm ≈ (C0 - U) /ρ0U w (1) In the above dimensionless

  1. Quantum spreading of a self-gravitating wave-packet in singularity free gravity

    Energy Technology Data Exchange (ETDEWEB)

    Buoninfante, Luca [Universita di Salerno, Dipartimento di Fisica ' ' E.R. Caianiello' ' , Fisciano (Italy); INFN-Sezione di Napoli, Gruppo Collegato di Salerno, Fisciano (Italy); University of Groningen, Van Swinderen Institute, Groningen (Netherlands); Lambiase, Gaetano [Universita di Salerno, Dipartimento di Fisica ' ' E.R. Caianiello' ' , Fisciano (Italy); INFN-Sezione di Napoli, Gruppo Collegato di Salerno, Fisciano (Italy); Mazumdar, Anupam [University of Groningen, Van Swinderen Institute, Groningen (Netherlands); University of Groningen, Kapteyn Astronomical Institute, Groningen (Netherlands)

    2018-01-15

    In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein's general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1/r singularity in the potential - such that the gradient of the potential vanishes within the scale of non-locality. We will show that a quantum wave-packet spreads faster for a ghost-free and singularity-free gravity as compared to the Newtonian case, therefore providing us a unique scenario for testing classical and quantum properties of short-distance gravity in a laboratory in the near future. (orig.)

  2. Cosmic Tsunamis in Modified Gravity: Disruption of Screening Mechanisms from Scalar Waves.

    Science.gov (United States)

    Hagala, R; Llinares, C; Mota, D F

    2017-03-10

    Extending general relativity by adding extra degrees of freedom is a popular approach for explaining the accelerated expansion of the Universe and to build high energy completions of the theory of gravity. The presence of such new degrees of freedom is, however, tightly constrained from several observations and experiments that aim to test general relativity in a wide range of scales. The viability of a given modified theory of gravity, therefore, strongly depends on the existence of a screening mechanism that suppresses the extra degrees of freedom. We perform simulations, and find that waves propagating in the new degrees of freedom can significantly impact the efficiency of some screening mechanisms, thereby threatening the viability of these modified gravity theories. Specifically, we show that the waves produced in the symmetron model can increase the amplitude of the fifth force and the parametrized post Newtonian parameters by several orders of magnitude.

  3. Quantum spreading of a self-gravitating wave-packet in singularity free gravity

    Science.gov (United States)

    Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

    2018-01-01

    In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein's general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1 / r singularity in the potential - such that the gradient of the potential vanishes within the scale of non-locality. We will show that a quantum wave-packet spreads faster for a ghost-free and singularity-free gravity as compared to the Newtonian case, therefore providing us a unique scenario for testing classical and quantum properties of short-distance gravity in a laboratory in the near future.

  4. Investigation of Gravity Waves VIA the Rotational Temperature of Hydroxyl Nightglow

    National Research Council Canada - National Science Library

    Willingham, Erin

    2001-01-01

    ... monochrometer optimized for the visible and near infrared. Quantifying gravity wave activity was the ultimate objective of this experiment. No spectrum of OH nightglow was recorded. The instrumentation was not sensitive enough to pick up the weak signal. This thesis is primarily a characterization of the equipment, its capabilities, and its limitations.

  5. Quantum spreading of a self-gravitating wave-packet in singularity free gravity

    NARCIS (Netherlands)

    Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

    In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein’s general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1 / r singularity in the potential – such

  6. A statistical study of variations of internal gravity wave energy characteristics in meteor zone

    Science.gov (United States)

    Gavrilov, N. M.; Kalov, E. D.

    1987-01-01

    Internal gravity wave (IGW) parameters obtained by the radiometer method have been considered by many other researchers. The results of the processing of regular radiometeor measurements taken during 1979 to 1980 in Obninsk (55.1 deg N, 36.6 deg E) are presented.

  7. Application of dopplionograms and gonionograms to atmospheric gravity wave disturbances in the ionosphere

    International Nuclear Information System (INIS)

    Wright, J.W.; Pitteway, M.L.V.

    1982-01-01

    A sequence of digital ionograms is processed by dopplionogram and gonionogram methods. Together, these disclose a disturbance in the F region which descends in altitude with time. Two wavelike periods of the disturbance are evident. The Doppler and angle-of-arrival behavior are consistent with a semiquantitative model of the plasma perturbations caused by an internal atmospheric gravity wave

  8. Turbulent behaviour of non-cohesive sediment gravity flows at unexpectedly high flow density

    Science.gov (United States)

    Baker, Megan; Baas, Jaco H.; Malarkey, Jonathan; Kane, Ian

    2016-04-01

    Experimental lock exchange-type turbidity currents laden with non-cohesive silica-flour were found to be highly dynamic at remarkably high suspended sediment concentrations. These experiments were conducted to produce sediment gravity flows of volumetric concentrations ranging from 1% to 52%, to study how changes in suspended sediment concentration affects the head velocities and run-out distances of these flows, in natural seawater. Increasing the volumetric concentration of suspended silica-flour, C, up to C = 46%, within the flows led to a progressive increase in the maximum head velocity. This relationship suggests that suspended sediment concentration intensifies the density difference between the turbulent suspension and the ambient water, which drives the flow, even if almost half of the available space is occupied by sediment particles. However, from C = 46% to C = 52% a rapid reduction in the maximum head velocity was measured. It is inferred that at C = 46%, friction from grain-to-grain interactions begins to attenuate turbulence within the flows. At C > 46%, the frictional stresses become progressively more dominant over the turbulent forces and excess density, thus producing lower maximum head velocities. This grain interaction process started to rapidly reduce the run-out distance of the silica-flour flows at equally high concentrations of C ≥ 47%. All flows with C tank, but the head velocities gradually reduced along the tank. Bagnold (1954, 1963) estimated that, for sand flows, grain-to-grain interactions start to become important in modulating turbulence at C > 9%. Yet, the critical flow concentration at which turbulence modulation commenced for these silica-flour laden flows appeared to be much higher. We suggest that Bagnold's 9% criterion cannot be applied to flows that carry fine-grained sediment, because turbulent forces are more important than dispersive forces, and frictional forces start to affect the flows only at concentrations just

  9. Holographic RG flows from Quasi-Topological Gravity

    International Nuclear Information System (INIS)

    Camara da Silva, U.; Sotkov, G.M.

    2013-01-01

    We investigate the holographic Renormalization Group (RG) flows and the critical phenomena that take place in the QFT's dual to the d-dimensional cubic Quasi-Topological Gravity coupled to scalar matter. The knowledge of the corresponding flat Domain Walls (DW's) solutions allows us to derive the explicit form of the QFT's β-functions, as well as of the trace anomalies a(l) and c(l), in terms of the matter superpotential. As a consequence we are able to determine the complete set of CFT data characterizing the universality classes of the UV and IR critical points and to follow the particular RG evolution of this data. We further analyse the dependence of the critical properties of such dual QFT's on the values of the Lovelock couplings and on the shape of the superpotential. For odd values of d, the explicit form of the “a and c-central charges” as functions of the running coupling constant, enable us to establish the conditions under which the a and c-Theorems for their decreasing are valid. The restrictions imposed on the massless holographic RG flows by the requirements of the positivity of the energy fluxes are derived. The particular case of quartic Higgs-like superpotential is studied in detail. It provides an example of unitary dual QFT's having few c≠a-critical points representing second or infinite order phase transitions. Depending on the range of the values of the coupling constant they exhibit massive and massless phases, described by a chain of distinct DW's solutions sharing common boundaries

  10. Gravity wave generation from jets and fronts: idealized and real-case simulations

    Science.gov (United States)

    Plougonven, Riwal; Arsac, Antonin; Hertzog, Albert; Guez, Lionel; Vial, François

    2010-05-01

    The generation of gravity waves from jets and fronts remains an outstanding issue in the dynamics of the atmosphere. It is important to explain and quantify this emission because of the several impacts of these waves, in particular the induced momentum fluxes towards the middle atmosphere, and their contribution to turbulence and mixing, e.g. in the region of the tropopause. Yet, the mechanisms at the origin of these waves have been difficult to identify, the fundamental reason for this being the separation between the time scales of balanced motions and gravity waves. Recent simulations of idealized baroclinic life cycles and of dipoles have provided insights into the mechanisms determining the characteristics and the amplitude of gravity waves emitted by jets. It has been shown in particular that the environmental strain and shear play a crucial role in determining the characteristics and location of the emitted waves, emphasizing jet exit regions for the appearance of coherent low-frequency waves. It has also been shown how advection of relatively small-scales allow to overcome the separation of time scales alluded to above. Recent results, remaining open questions and ongoing work on these idealized simulations will be briefly summarized. Nevertheless, unavoidable shortcomings of such idealized simulations include the sensitivity of the emitted waves to model setup (resolution, diffusion, parameterizations) and uncertainty regarding the realism of this aspect of the simulations. Hence, it is necessary to compare simulations with observations in order to assess their relevance. Such comparison has been undertaken using the dataset from the Vorcore campaign (Sept. 2005 - Feb. 2006, Hertzog, J. Atmos. Ocean. Techno. 2007) during which 27 superpressure balloons drifted as quasi-Lagrangian tracers in the lower stratosphere above Antarctica and the Southern Ocean. High-resolution simulations (dx = 20 km) have been carried out using the Weather Research and Forecast

  11. Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data

    Directory of Open Access Journals (Sweden)

    N. F. Arnold

    1998-10-01

    Full Text Available Quasi-periodic fluctuations in the returned ground-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We have applied a technique that extracts the first radar range returns from the F-region to study the spatial extent and characteristics of these waves in the CUTLASS field-of-view. Some ray tracing was carried out to test the applicability of this method. The EISCAT radar facility at Tromsø is well within the CUTLASS field-of-view for these waves and provides a unique opportunity to assess independently the ability of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF radar was operating in its CP-1 mode, demonstrate that the radars were in good agreement, especially if one selects the electron density variations measured by EISCAT at around 235 km. CUTLASS and EISCAT gravity wave observations complement each other; the former extends the spatial field of view considerably, whilst the latter provides detailed vertical information about a range of ionospheric parameters.Key words. Ionosphere (ionosphere – atmosphere interactions · Meteorology and atmospheric dynamics (thermospheric dynamics · Radio science (ionospheric propagations

  12. Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data

    Directory of Open Access Journals (Sweden)

    N. F. Arnold

    Full Text Available Quasi-periodic fluctuations in the returned ground-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We have applied a technique that extracts the first radar range returns from the F-region to study the spatial extent and characteristics of these waves in the CUTLASS field-of-view. Some ray tracing was carried out to test the applicability of this method. The EISCAT radar facility at Tromsø is well within the CUTLASS field-of-view for these waves and provides a unique opportunity to assess independently the ability of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF radar was operating in its CP-1 mode, demonstrate that the radars were in good agreement, especially if one selects the electron density variations measured by EISCAT at around 235 km. CUTLASS and EISCAT gravity wave observations complement each other; the former extends the spatial field of view considerably, whilst the latter provides detailed vertical information about a range of ionospheric parameters.

    Key words. Ionosphere (ionosphere – atmosphere interactions · Meteorology and atmospheric dynamics (thermospheric dynamics · Radio science (ionospheric propagations

  13. Gravity induced corrections to quantum mechanical wave functions

    International Nuclear Information System (INIS)

    Singh, T.P.

    1990-03-01

    We perform a semiclassical expansion in the Wheeler-DeWitt equation, in powers of the gravitational constant. We then show that quantum gravitational fluctuations can provide a correction to the wave-functions which are solutions of the Schroedinger equation for matter. This also implies a correction to the expectation values of quantum mechanical observables. (author). 6 refs

  14. Thermal infrared sounding observations of lower atmospheric variances at Mars and their implications for gravity wave activity: a preliminary examination

    Science.gov (United States)

    Heavens, N. G.

    2017-12-01

    It has been recognized for over two decades that the mesoscale statistical variance observed by Earth-observing satellites at temperature-sensitive frequencies above the instrumental noise floor is a measure of gravity wave activity. These types of observation have been made by a variety of satellite instruments have been an important validation tool for gravity wave parameterizations in global and mesoscale models. At Mars, the importance of topographic and non-topographic sources of gravity waves for the general circulation is now widely recognized and the target of recent modeling efforts. However, despite several ingenious studies, gravity wave activity near hypothetical lower atmospheric sources has been poorly and unsystematically characterized, partly because of the difficulty of separating the gravity wave activity from baroclinic wave activity and the thermal tides. Here will be presented a preliminary analysis of calibrated radiance variance at 15.4 microns (635-665 cm-1) from nadir, off-nadir, and limb observations by the Mars Climate Sounder on board Mars Reconnaissance Orbiter. The overarching methodology follows Wu and Waters (1996, 1997). Nadir, off-nadir, and lowest detector limb observations should sample variability with vertical weighting functions centered high in the lower atmosphere (20-30 km altitude) and full width half maximum (FWHM) 20 km but be sensitive to gravity waves with different horizontal wavelengths and slightly different vertical wavelengths. This work is supported by NASA's Mars Data Analysis Program (NNX14AM32G). References Wu, D.L. and J.W. Waters, 1996, Satellite observations of atmospheric variances: A possible indication of gravity waves, GRL, 23, 3631-3634. Wu D.L. and J.W. Waters, 1997, Observations of Gravity Waves with the UARS Microwave Limb Sounder. In: Hamilton K. (eds) Gravity Wave Processes. NATO ASI Series (Series I: Environmental Change), vol 50. Springer, Berlin, Heidelberg.

  15. Gravity

    CERN Document Server

    Gamow, George

    2003-01-01

    A distinguished physicist and teacher, George Gamow also possessed a special gift for making the intricacies of science accessible to a wide audience. In Gravity, he takes an enlightening look at three of the towering figures of science who unlocked many of the mysteries behind the laws of physics: Galileo, the first to take a close look at the process of free and restricted fall; Newton, originator of the concept of gravity as a universal force; and Einstein, who proposed that gravity is no more than the curvature of the four-dimensional space-time continuum.Graced with the author's own draw

  16. Statistical comparisons of gravity wave features derived from OH airglow and SABER data

    Science.gov (United States)

    Gelinas, L. J.; Hecht, J. H.; Walterscheid, R. L.

    2017-12-01

    The Aerospace Corporation's near-IR camera (ANI), deployed at Andes Lidar Observatory (ALO), Cerro Pachon Chile (30S,70W) since 2010, images the bright OH Meinel (4,2) airglow band. The imager provides detailed observations of gravity waves and instability dynamics, as described by Hecht et al. (2014). The camera employs a wide-angle lens that views a 73 by 73 degree region of the sky, approximately 120 km x 120 km at 85 km altitude. Image cadence of 30s allows for detailed spectral analysis of the horizontal components of wave features, including the evolution and decay of instability features. The SABER instrument on NASA's TIMED spacecraft provides remote soundings of kinetic temperature profiles from the lower stratosphere to the lower thermosphere. Horizontal and vertical filtering techniques allow SABER temperatures to be analyzed for gravity wave variances [Walterscheid and Christensen, 2016]. Here we compare the statistical characteristics of horizontal wave spectra, derived from airglow imagery, with vertical wave variances derived from SABER temperature profiles. The analysis is performed for a period of strong mountain wave activity over the Andes spanning the period between June and September 2012. Hecht, J. H., et al. (2014), The life cycle of instability features measured from the Andes Lidar Observatory over Cerro Pachon on March 24, 2012, J. Geophys. Res. Atmos., 119, 8872-8898, doi:10.1002/2014JD021726. Walterscheid, R. L., and A. B. Christensen (2016), Low-latitude gravity wave variances in the mesosphere and lower thermosphere derived from SABER temperature observation and compared with model simulation of waves generated by deep tropical convection, J. Geophys. Res. Atmos., 121, 11,900-11,912, doi:10.1002/2016JD024843.

  17. Mesoscale variations in acoustic signals induced by atmospheric gravity waves.

    Science.gov (United States)

    Chunchuzov, Igor; Kulichkov, Sergey; Perepelkin, Vitaly; Ziemann, Astrid; Arnold, Klaus; Kniffka, Anke

    2009-02-01

    The results of acoustic tomographic monitoring of the coherent structures in the lower atmosphere and the effects of these structures on acoustic signal parameters are analyzed in the present study. From the measurements of acoustic travel time fluctuations (periods 1 min-1 h) with distant receivers, the temporal fluctuations of the effective sound speed and wind speed are retrieved along different ray paths connecting an acoustic pulse source and several receivers. By using a coherence analysis of the fluctuations near spatially distanced ray turning points, the internal wave-associated fluctuations are filtered and their spatial characteristics (coherences, horizontal phase velocities, and spatial scales) are estimated. The capability of acoustic tomography in estimating wind shear near ground is shown. A possible mechanism describing the temporal modulation of the near-ground wind field by ducted internal waves in the troposphere is proposed.

  18. Global Gravity Wave Variances from Aura MLS: Characteristics and Interpretation

    Science.gov (United States)

    2008-12-01

    slight longitudinal variations, with secondary high- latitude peaks occurring over Greenland and Europe . As the QBO changes to the westerly phase, the...equatorial GW temperature variances from suborbital data (e.g., Eck- ermann et al. 1995). The extratropical wave variances are generally larger in the...emanating from tropopause altitudes, presumably radiated from tropospheric jet stream in- stabilities associated with baroclinic storm systems that

  19. Propagation of acoustic-gravity waves in arctic zones with elastic ice-sheets

    Science.gov (United States)

    Kadri, Usama; Abdolali, Ali; Kirby, James T.

    2017-04-01

    We present an analytical solution of the boundary value problem of propagating acoustic-gravity waves generated in the ocean by earthquakes or ice-quakes in arctic zones. At the surface, we assume elastic ice-sheets of a variable thickness, and show that the propagating acoustic-gravity modes have different mode shape than originally derived by Ref. [1] for a rigid ice-sheet settings. Computationally, we couple the ice-sheet problem with the free surface model by Ref. [2] representing shrinking ice blocks in realistic sea state, where the randomly oriented ice-sheets cause inter modal transition at the edges and multidirectional reflections. We then derive a depth-integrated equation valid for spatially slowly varying thickness of ice-sheet and water depth. Surprisingly, and unlike the free-surface setting, here it is found that the higher acoustic-gravity modes exhibit a larger contribution. These modes travel at the speed of sound in water carrying information on their source, e.g. ice-sheet motion or submarine earthquake, providing various implications for ocean monitoring and detection of quakes. In addition, we found that the propagating acoustic-gravity modes can result in orbital displacements of fluid parcels sufficiently high that may contribute to deep ocean currents and circulation, as postulated by Refs. [1, 3]. References [1] U. Kadri, 2016. Generation of Hydroacoustic Waves by an Oscillating Ice Block in Arctic Zones. Advances in Acoustics and Vibration, 2016, Article ID 8076108, 7 pages http://dx.doi.org/10.1155/2016/8076108 [2] A. Abdolali, J. T. Kirby and G. Bellotti, 2015, Depth-integrated equation for hydro-acoustic waves with bottom damping, J. Fluid Mech., 766, R1 doi:10.1017/jfm.2015.37 [3] U. Kadri, 2014. Deep ocean water transportation by acoustic?gravity waves. J. Geophys. Res. Oceans, 119, doi:10.1002/ 2014JC010234

  20. Nonlinear drift waves in a dusty plasma with sheared flows

    Energy Technology Data Exchange (ETDEWEB)

    Vranjes, J. [K.U. Leuven (Belgium). Center for Plasma Astrophysics; Shukla, R.K. [Ruhr-Univ. Bochum (Germany). Inst. fuer Theoretische Physik IV

    2002-01-01

    Nonlinear properties of dust-modified drift waves and dust-drift waves in a dusty magnetoplasma with equilibrium sheared flows are examined. For this purpose, the relevant nonlinear equations for drift waves are analyzed for various profiles of the perpendicular and parallel plasma flows, and a variety of nonlinear solutions (viz. single and double vortex chains accompanied with zonal flows, tripolar and global vortices), which are driven by nommiform shear flows and nommiform dust density, is presented.

  1. Nonlinear drift waves in a dusty plasma with sheared flows

    International Nuclear Information System (INIS)

    Vranjes, J.; Shukla, R.K.

    2002-01-01

    Nonlinear properties of dust-modified drift waves and dust-drift waves in a dusty magnetoplasma with equilibrium sheared flows are examined. For this purpose, the relevant nonlinear equations for drift waves are analyzed for various profiles of the perpendicular and parallel plasma flows, and a variety of nonlinear solutions (viz. single and double vortex chains accompanied with zonal flows, tripolar and global vortices), which are driven by nommiform shear flows and nommiform dust density, is presented

  2. A statistical study of gravity waves from radiosonde observations at Wuhan (30° N, 114° E China

    Directory of Open Access Journals (Sweden)

    S. D. Zhang

    2005-03-01

    Full Text Available Several works concerning the dynamical and thermal structures and inertial gravity wave activities in the troposphere and lower stratosphere (TLS from the radiosonde observation have been reported before, but these works were concentrated on either equatorial or polar regions. In this paper, background atmosphere and gravity wave activities in the TLS over Wuhan (30° N, 114° E (a medium latitudinal region were statistically studied by using the data from radiosonde observations on a twice daily basis at 08:00 and 20:00 LT in the period between 2000 and 2002. The monthly-averaged temperature and horizontal winds exhibit the essential dynamic and thermal structures of the background atmosphere. For avoiding the extreme values of background winds and temperature in the height range of 11-18km, we studied gravity waves, respectively, in two separate height regions, one is from ground surface to 10km (lower part, and the other is within 18-25km (upper part. In total, 791 and 1165 quasi-monochromatic inertial gravity waves were extracted from our data set for the lower and upper parts, respectively. The gravity wave parameters (intrinsic frequencies, amplitudes, wavelengths, intrinsic phase velocities and wave energies are calculated and statistically studied. The statistical results revealed that in the lower part, there were 49.4% of gravity waves propagating upward, and the percentage was 76.4% in the upper part. Moreover, the average wave amplitudes and energies are less than those at the lower latitudinal regions, which indicates that the gravity wave parameters have a latitudinal dependence. The correlated temporal evolution of the monthly-averaged wave energies in the lower and upper parts and a subsequent quantitative analysis strongly suggested that at the observation site, dynamical instability (strong wind shear induced by the tropospheric jet is the main excitation source of inertial gravity waves in the TLS.

  3. Characteristics of atmospheric gravity waves observed using the MU (Middle and Upper atmosphere) radar and GPS (Global Positioning System) radio occultation.

    Science.gov (United States)

    Tsuda, Toshitaka

    2014-01-01

    The wind velocity and temperature profiles observed in the middle atmosphere (altitude: 10-100 km) show perturbations resulting from superposition of various atmospheric waves, including atmospheric gravity waves. Atmospheric gravity waves are known to play an important role in determining the general circulation in the middle atmosphere by dynamical stresses caused by gravity wave breaking. In this paper, we summarize the characteristics of atmospheric gravity waves observed using the middle and upper atmosphere (MU) radar in Japan, as well as novel satellite data obtained from global positioning system radio occultation (GPS RO) measurements. In particular, we focus on the behavior of gravity waves in the mesosphere (50-90 km), where considerable gravity wave attenuation occurs. We also report on the global distribution of gravity wave activity in the stratosphere (10-50 km), highlighting various excitation mechanisms such as orographic effects, convection in the tropics, meteorological disturbances, the subtropical jet and the polar night jet.

  4. 3-Space In-Flow Theory of Gravity: Boreholes, Blackholes and the Fine Structure Constant

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2006-04-01

    Full Text Available A theory of 3-space explains the phenomenon of gravity as arising from the time-dependence and inhomogeneity of the differential flow of this 3-space. The emergent theory of gravity has two gravitational constants: G - Newton's constant, and a dimensionless constant alpha. Various experiments and astronomical observations have shown that alpha is the fine structure constant ~1/137. Here we analyse the Greenland Ice Shelf and Nevada Test Site borehole g anomalies, and confirm with increased precision this value of alpha. This and other successful tests of this theory of gravity, including the supermassive black holes in globular clusters and galaxies, and the "dark-matter" effect in spiral galaxies, shows the validity of this theory of gravity. This success implies that the non-relativistic Newtonian gravity was fundamentally flawed from the beginning, and that this flaw was inherited by the relativistic General Relativity theory of gravity.

  5. 3-Space In-Flow Theory of Gravity: Boreholes, Blackholes and the Fine Structure Constant

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2006-04-01

    Full Text Available A theory of 3-space explains the phenomenon of gravity as arising from the time-dependence and inhomogeneity of the differential flow of this 3-space. The emergent theory of gravity has two gravitational constants: GN — Newton’s constant, and a dimensionless constant α. Various experiments and astronomical observations have shown that α is the fine structure constant ≈ 1/137. Here we analyse the Greenland Ice Shelf and Nevada Test Site borehole g anomalies, and confirm with increased precision this value of α. This and other successful tests of this theory of gravity, including the supermassive black holes in globular clusters and galaxies, and the “dark-matter” effect in spiral galaxies, shows the validity of this theory of gravity. This success implies that the non-relativistic Newtonian gravity was fundamentally flawed from the beginning, and that this flaw was inherited by the relativistic General Relativity theory of gravity.

  6. Effect of small floating disks on the propagation of gravity waves

    Energy Technology Data Exchange (ETDEWEB)

    Santi, F De; Olla, P, E-mail: olla@dsf.unica.it [ISAC-CNR, Sez. Cagliari, I-09042 Monserrato (Italy)

    2017-04-15

    A dispersion relation for gravity waves in water covered by disk-like impurities embedded in a viscous matrix is derived. The macroscopic equations are obtained by ensemble-averaging the fluid equations at the disk scale in the asymptotic limit of long waves and low disk surface fraction. Various regimes are identified depending on the disk radii and the thickness and viscosity of the top layer. Semi-quantitative analysis in the close-packing regime suggests dramatic modification of the dynamics, with orders of magnitude increase in wave damping and wave dispersion. A simplified model working in this regime is proposed. Possible applications to wave propagation in an ice-covered ocean are discussed and comparison with field data is provided. (paper)

  7. The evolution of a localized nonlinear wave of the Kelvin-Helmholtz instability with gravity

    Science.gov (United States)

    Orazzo, Annagrazia; Hoepffner, Jérôme

    2012-11-01

    At the interface between two fluids of different density and in the presence of gravity, there are well known periodic surface waves which can propagate for long distances with little attenuation, as it is for instance the case at the surface of the sea. If wind is present, these waves progressively accumulate energy as they propagate and grow to large sizes—this is the Kelvin-Helmholtz instability. On the other hand, we show in this paper that for a given wind strength, there is potential for the growth of a localized nonlinear wave. This wave can reach a size such that the hydrostatic pressure drop from top to bottom equals the stagnation pressure of the wind. This process for the disruption of the flat interface is localized and nonlinear. We study the properties of this wave using numerical simulations of the Navier-Stokes equations.

  8. Observation of mesospheric gravity waves at Comandante Ferraz Antarctica Station (62° S

    Directory of Open Access Journals (Sweden)

    P. B. Souza

    2009-06-01

    Full Text Available An airglow all-sky imager was operated at Comandante Ferraz Antarctica Station (62.1° S, 58.4° W, between April and October of 2007. Mesospheric gravity waves were observed using the OH airglow layer during 43 nights with good weather conditions. The waves presented horizontal wavelengths between 10 and 60 km and observed periods mainly distributed between 5 and 20 min. The observed phase speeds range between 5 m/s and 115 m/s; the majority of the wave velocities were between 10 and 60 m/s. The waves showed a preferential propagation direction towards the southwest in winter (May to July, while during spring (August to October there was an anisotropy with a preferential propagation direction towards the northwest. Unusual mesospheric fronts were also observed. The most probable wave source could be associated to orographic forcing, cold fronts or strong cyclonic activity in the Antarctica Peninsula.

  9. GPS-TEC Observation of Gravity Waves Generated in the Ionosphere During 21 August 2017 Total Solar Eclipse

    Science.gov (United States)

    Nayak, Chinmaya; Yiǧit, Erdal

    2018-01-01

    The present work investigates ionospheric effects of the 21 August 2017 total solar eclipse, particularly targeting eclipse-generated gravity waves in the ionosphere. Ionospheric total electron content (TEC) derived from Global Positioning System (GPS) data obtained from a number of stations located both along and across the path of eclipse totality has been utilized for this purpose. Distinct gravity wave-like signatures with wave periods around 20-90 min (with dominant peak at 25-30 min wave period) have been observed at all locations both in the path of totality and away from it. The observed gravity waves are more intense at locations closer to the path of totality, and the wave amplitudes decrease gradually with increasing distance from the path of totality. Our result highlights the manifestation of eclipse-generated waves in the variability of the terrestrial ionosphere.

  10. Detection of large-scale concentric gravity waves from a Chinese airglow imager network

    Science.gov (United States)

    Lai, Chang; Yue, Jia; Xu, Jiyao; Yuan, Wei; Li, Qinzeng; Liu, Xiao

    2018-06-01

    Concentric gravity waves (CGWs) contain a broad spectrum of horizontal wavelengths and periods due to their instantaneous localized sources (e.g., deep convection, volcanic eruptions, or earthquake, etc.). However, it is difficult to observe large-scale gravity waves of >100 km wavelength from the ground for the limited field of view of a single camera and local bad weather. Previously, complete large-scale CGW imagery could only be captured by satellite observations. In the present study, we developed a novel method that uses assembling separate images and applying low-pass filtering to obtain temporal and spatial information about complete large-scale CGWs from a network of all-sky airglow imagers. Coordinated observations from five all-sky airglow imagers in Northern China were assembled and processed to study large-scale CGWs over a wide area (1800 km × 1 400 km), focusing on the same two CGW events as Xu et al. (2015). Our algorithms yielded images of large-scale CGWs by filtering out the small-scale CGWs. The wavelengths, wave speeds, and periods of CGWs were measured from a sequence of consecutive assembled images. Overall, the assembling and low-pass filtering algorithms can expand the airglow imager network to its full capacity regarding the detection of large-scale gravity waves.

  11. The gravitational wave stress–energy (pseudo)-tensor in modified gravity

    Science.gov (United States)

    Saffer, Alexander; Yunes, Nicolás; Yagi, Kent

    2018-03-01

    The recent detections of gravitational waves by the advanced LIGO and Virgo detectors open up new tests of modified gravity theories in the strong-field and dynamical, extreme gravity regime. Such tests rely sensitively on the phase evolution of the gravitational waves, which is controlled by the energy–momentum carried by such waves out of the system. We here study four different methods for finding the gravitational wave stress–energy pseudo-tensor in gravity theories with any combination of scalar, vector, or tensor degrees of freedom. These methods rely on the second variation of the action under short-wavelength averaging, the second perturbation of the field equations in the short-wavelength approximation, the construction of an energy complex leading to a Landau–Lifshitz tensor, and the use of Noether’s theorem in field theories about a flat background. We apply these methods in general relativity, Jordan–Fierz–Brans–Dicky theoy, and Einstein-Æther theory to find the gravitational wave stress–energy pseudo-tensor and calculate the rate at which energy and linear momentum is carried away from the system. The stress–energy tensor and the rate of linear momentum loss in Einstein-Æther theory are presented here for the first time. We find that all methods yield the same rate of energy loss, although the stress–energy pseudo-tensor can be functionally different. We also find that the Noether method yields a stress–energy tensor that is not symmetric or gauge-invariant, and symmetrization via the Belinfante procedure does not fix these problems because this procedure relies on Lorentz invariance, which is spontaneously broken in Einstein-Æther theory. The methods and results found here will be useful for the calculation of predictions in modified gravity theories that can then be contrasted with observations.

  12. Temporal variability of gravity wave drag - vertical coupling and possible climate links

    Science.gov (United States)

    Miksovsky, Jiri; Sacha, Petr; Kuchar, Ales; Pisoft, Petr

    2017-04-01

    In the atmosphere, the internal gravity waves (IGW) are one of the fastest ways of natural information transfer in the vertical direction. Tropospheric changes that result in modification of sourcing, propagation or breaking conditions for IGWs almost immediately influence the distribution of gravity wave drag in the stratosphere. So far most of the related studies deal with IGW impacts higher in the upper stratospheric/mesospheric region and with the modulation of IGWs by planetary waves. This is most likely due to the fact that IGWs induce highest accelerations in the mesosphere and lower thermosphere region. However, the imposed drag force is much bigger in the stratosphere. In the presented analysis, we have assessed the relationship between the gravity wave activity in the stratosphere and other climatic phenomena through statistical techniques. Multivariable regression has been applied to investigate the IGW-related eastward and northward wind tendencies in the CMAM30-SD data, subject to the explanatory variables involving local circulation characteristics (derived from regional configuration of the thermobaric field) as well as the phases of the large-scale internal climate variability modes (ENSO, NAO, QBO). Our tests have highlighted several geographical areas with statistically significant responses of the orographic gravity waves effect to each of the variability modes under investigation; additional experiments have also indicated distinct signs of nonlinearity in some of the links uncovered. Furthermore, we have also applied composite analysis of displaced and split stratospheric polar vortex events (SPV) from CMAM30-SD to focus on how the strength and occurrence of the IGW hotspots can play a role in SPV occurrence and frequency.

  13. Chameleon fields, wave function collapse and quantum gravity

    International Nuclear Information System (INIS)

    Zanzi, A

    2015-01-01

    Chameleon fields are quantum (usually scalar) fields, with a density-dependent mass. In a high-density environment, the mass of the chameleon is large. On the contrary, in a small-density environment (e.g. on cosmological distances), the chameleon is very light. A model where the collapse of the wave function is induced by chameleon fields is presented. During this analysis, a Chameleonic Equivalence Principle (CEP) will be formulated: in this model, quantum gravitation is equivalent to a conformal anomaly. Further research efforts are necessary to verify whether this proposal is compatible with phenomeno logical constraints. (paper)

  14. Gravity dual of spin and charge density waves

    Science.gov (United States)

    Jokela, Niko; Järvinen, Matti; Lippert, Matthew

    2014-12-01

    At high enough charge density, the homogeneous state of the D3-D7' model is unstable to fluctuations at nonzero momentum. We investigate the end point of this instability, finding a spatially modulated ground state, which is a charge and spin density wave. We analyze the phase structure of the model as a function of chemical potential and magnetic field and find the phase transition from the homogeneous state to be first order, with a second-order critical point at zero magnetic field.

  15. Constraint on reconstructed f(R) gravity models from gravitational waves

    Science.gov (United States)

    Lee, Seokcheon

    2018-06-01

    The gravitational wave (GW) detection of a binary neutron star inspiral made by the Advanced LIGO and Advanced Virgo paves the unprecedented way for multi-messenger observations. The propagation speed of this GW can be scrutinized by comparing the arrival times between GW and neutrinos or photons. It provides the constraint on the mass of the graviton. f(R) gravity theories have the habitual non-zero mass gravitons in addition to usual massless ones. Previously, we show that the model independent f(R) gravity theories can be constructed from the both background evolution and the matter growth with one undetermined parameter. We show that this parameter can be constrained from the graviton mass bound obtained from GW detection. Thus, the GW detection provides the invaluable constraint on the validity of f(R) gravity theories.

  16. Quantum solitonic wave-packet of a meso-scopic system in singularity free gravity

    Science.gov (United States)

    Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

    2018-06-01

    In this paper we will discuss how to localise a quantum wave-packet due to self-gravitating meso-scopic object by taking into account gravitational self-interaction in the Schrödinger equation beyond General Relativity. In particular, we will study soliton-like solutions in infinite derivative ghost free theories of gravity, which resolves the gravitational 1 / r singularity in the potential. We will show a unique feature that the quantum spread of such a gravitational system is larger than that of the Newtonian gravity, therefore enabling us a window of opportunity to test classical and quantum properties of such theories of gravity in the near future at a table-top experiment.

  17. Studies of midlatitude mesospheric temperature variability and its relationship to gravity waves, tides, and planetary waves

    Science.gov (United States)

    Beissner, Kenneth C.

    1997-10-01

    Temperature observations of the middle atmosphere have been carried out from September 1993 through July 1995 using a Rayleigh backscatter lidar located at Utah State University (42oN, 111oW). Data have been analyzed to obtain absolute temperature profiles from 40 to 90 km. Various sources of error were reviewed in order to ensure the quality of the measurements. This included conducting a detailed examination of the data reduction procedure, integration methods, and averaging techniques, eliminating errors of 1-3%. The temperature structure climatology has been compared with several other mid-latitude data sets, including those from the French lidars, the SME spacecraft, the sodium lidars at Ft. Collins and Urbana, the MSISe90 model, and a high- latitude composite set from Andenes, Norway. In general, good agreement occurs at mid-latitudes, but areas of disagreement do exist. Among these, the Utah temperatures are significantly warmer than the MSISe90 temperatures above approximately 80 km, they are lower below 80 km than any of the others in summer, they show major year- to-year variability in the winter profiles, and they differ from the sodium lidar data at the altitudes where the temperature profiles should overlap. Also, comparisons between observations and a physics based global circulation model, the TIME-GCM, were conducted for a mid-latitude site. A photo-chemical model was developed to predict airglow intensity of OH based on output from the TIME-GCM. Many discrepancies between the model and observations were found, including a modeled summer mesopause too high, a stronger summer inversion not normally observed by lidar, a fall-spring asymmetry in the OH winds and lidar temperatures but not reproduced in the TIME-GCM equinoctial periods, larger winter seasonal wind tide than observed by the FPI, and a failure of the model to reverse the summertime mesospheric jet. It is our conclusion these discrepancies are due to a gravity wave parameterization in the

  18. Stratospheric gravity wave activities inferred through the GPS radio occultation technique; Ondas de gravidade na estratosfera terrestre inferida atraves da tecnica de radio ocultacao de GPS

    Energy Technology Data Exchange (ETDEWEB)

    Wrasse, Cristiano Max [Universidade do Vale do Paraiba (UNIVAP), Instituto de Pesquisa e Desenvolvimento (IPeD), Sao Jose dos Campos, SP (Brazil); Takahashi, Hisao; Fechine, Joaquim; Denardini, Clezio Marcos [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Wickert, Jens, E-mail: cmw@univap.br, E-mail: hisaotak@laser.inpe.br, E-mail: joaquim@laser.inpe.br, E-mail: denardin@dae.inpe.br, E-mail: jens.wickert@gfz-potsdam.de [GeoForschungsZentrum, Potsdam (GFZ), Department of Geodesy and Remote Sensing (Germany)

    2007-07-01

    Stratospheric gravity wave activities were deduced from GPS radio occultation temperature profiles obtained by CHAMP satellite between 2001 and 2005. Potential energy profiles are used to analyze the gravity wave activity over South America. The results showed an inter-annual variation of the potential energy integrated between 24 and 34 km of altitude. The gravity wave activity is more concentrated around the equatorial region. In order to evaluate the seasonal variation of the gravity wave activity, a mean potential energy was determined over (10 deg N-10 deg S) and (100 deg W-20 deg W). The results showed a lower gravity wave activity during winter time, while during spring time the mean potential energy showed an increase in the wave activity. The results of the mean potential energy also showed that the gravity wave activity in the lower stratosphere exhibits a higher wave activity during 2002 and 2004 and a lower wave activity during 2003 and 2005. (author)

  19. Sea surface temperature as a proxy for convective gravity wave excitation: a study based on global gravity wave observations in the middle atmosphere

    Directory of Open Access Journals (Sweden)

    J. Y. Jia

    2014-11-01

    Full Text Available Absolute values of gravity wave momentum flux (GWMF deduced from satellite measurements by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER instrument and the High Resolution Dynamics Limb Sounder (HIRDLS are correlated with sea surface temperature (SST with the aim of identifying those oceanic regions for which convection is a major source of gravity waves (GWs. Our study identifies those latitude bands where high correlation coefficients indicate convective excitation with confidence. This is based on a global ray-tracing simulation, which is used to delineate the source and wind-filtering effects. Convective GWs are identified at the eastern coasts of the continents and over the warm water regions formed by the warm ocean currents, in particular the Gulf Stream and the Kuroshio. Potential contributions of tropical cyclones to the excitation of the GWs are discussed. Convective excitation can be identified well into the mid-mesosphere. In propagating upward, the centers of GWMF formed by convection shift poleward. Some indications of the main forcing regions are even shown for the upper mesosphere/lower thermosphere (MLT.

  20. Modeling sheet-flow sand transport under progressive surface waves

    NARCIS (Netherlands)

    Kranenburg, Wouter

    2013-01-01

    In the near-shore zone, energetic sea waves generate sheet-flow sand transport. In present day coastal models, wave-induced sheet-flow sand transport rates are usually predicted with semi-empirical transport formulas, based on extensive research on this phenomenon in oscillatory flow tunnels.

  1. Short-period atmospheric gravity waves - A study of their statistical properties and source mechanisms

    Science.gov (United States)

    Gedzelman, S. D.

    1983-01-01

    Gravity waves for the one year period beginning 19 October 1976 around Palisades, New York, are investigated to determine their statistical properties and sources. The waves have typical periods of 10 min, pressure amplitudes of 3 Pa and velocities of 30 m/s. In general, the largest, amplitude waves occur during late fall and early winter when the upper tropospheric winds directly overhead are fastest and the static stability of the lower troposphere is greatest. Mean wave amplitudes correlate highly with the product of the mean maximum wind speed and the mean low level stratification directly aloft. A distinct diurnal variation of wave amplitudes with the largest waves occurring in the pre-dawn hours is also observed as a result of the increased static stability then. The majority of waves are generated by shear instability; however, a number of waves are generated by distant sources such as nuclear detonations or large thunderstorms. The waves with distant sources can be distinguished on the basis of their generally much higher coherency across the grid and velocities that depart markedly from the wind velocity at any point in the sounding.

  2. Internal gravity waves in Titan's atmosphere observed by Voyager radio occultation

    Science.gov (United States)

    Hinson, D. P.; Tyler, G. L.

    1983-01-01

    The radio scintillations caused by scattering from small-scale irregularities in Titan's neutral atmosphere during a radio occultation of Voyager 1 by Titan are investigated. Intensity and frequency fluctuations occurred on time scales from about 0.1 to 1.0 sec at 3.6 and 13 cm wavelengths whenever the radio path passed within 90 km of the surface, indicating the presence of variations in refractivity on length scales from a few hundred meters to a few kilometers. Above 25 km, the altitude profile of intensity scintillations closely agrees with the predictions of a simple theory based on the characteristics of internal gravity waves propagating with little or no attenuation through the vertical stratification in Titan's atmosphere. These observations support a hypothesis of stratospheric gravity waves, possibly driven by a cloud-free convective region in the lowest few kilometers of the stratosphere.

  3. Long-Term Observation of Small and Medium-Scale Gravity Waves over the Brazilian Equatorial Region

    Science.gov (United States)

    Essien, Patrick; Buriti, Ricardo; Wrasse, Cristiano M.; Medeiros, Amauri; Paulino, Igo; Takahashi, Hisao; Campos, Jose Andre

    2016-07-01

    This paper reports the long term observations of small and medium-scale gravity waves over Brazilian equatorial region. Coordinated optical and radio measurements were made from OLAP at Sao Joao do Cariri (7.400S, 36.500W) to investigate the occurrences and properties and to characterize the regional mesospheric gravity wave field. All-sky imager measurements were made from the site. for almost 11 consecutive years (September 2000 to November 2010). Most of the waves propagated were characterized as small-scale gravity. The characteristics of the two waves events agreed well with previous gravity wave studies from Brazil and other sites. However, significant differences in the wave propagation headings indicate dissimilar source regions. The observed medium-scale gravity wave events constitute an important new dataset to study their mesospheric properties at equatorial latitudes. These data exhibited similar propagation headings to the short period events, suggesting they originated from the same source regions. It was also observed that some of the medium-scale were capable of propagating into the lower thermosphere where they may have acted directly as seeds for the Rayleigh-Taylor instability development. The wave events were primarily generated by meteorological processes since there was no correlation between the evolution of the wave events and solar cycle F10.7.

  4. Destruction of coherence in nondemolition monitoring: quantum 'watchdog effect' in gravity wave detectors

    International Nuclear Information System (INIS)

    Zurek, W.H.

    1984-01-01

    The author shows that nondemolition monitoring of a Weber bar may prevent changes of the number of phonons, and thus influence the sensitivity of quantum-counting gravity wave detectors. This effect is similar to the Watchdog Effect which is predicted to delay decays of the monitored, unstable quantum system. Relations between watchdog effect and Environment-Induced Superselection Rules as well as its connections to the fundamental questions of the quantum theory of measurement are briefly considered. (Auth.)

  5. Second generation diffusion model of interacting gravity waves on the surface of deep fluid

    Directory of Open Access Journals (Sweden)

    A. Pushkarev

    2004-01-01

    Full Text Available We propose a second generation phenomenological model for nonlinear interaction of gravity waves on the surface of deep water. This model takes into account the effects of non-locality of the original Hasselmann diffusion equation still preserving important properties of the first generation model: physically consistent scaling, adherence to conservation laws and the existence of Kolmogorov-Zakharov solutions. Numerical comparison of both models with the original Hasselmann equation shows that the second generation models improves the angular distribution in the evolving wave energy spectrum.

  6. Gravitational waves from quasicircular black-hole binaries in dynamical Chern-Simons gravity.

    Science.gov (United States)

    Yagi, Kent; Yunes, Nicolás; Tanaka, Takahiro

    2012-12-21

    Dynamical Chern-Simons gravity cannot be strongly constrained with current experiments because it reduces to general relativity in the weak-field limit. This theory, however, introduces modifications in the nonlinear, dynamical regime, and thus it could be greatly constrained with gravitational waves from the late inspiral of black-hole binaries. We complete the first self-consistent calculation of such gravitational waves in this theory. For favorable spin orientations, advanced ground-based detectors may improve existing solar system constraints by 6 orders of magnitude.

  7. An Asymptotic and Stochastic Theory for the Effects of Surface Gravity Waves on Currents and Infragravity Waves

    Science.gov (United States)

    McWilliams, J. C.; Lane, E.; Melville, K.; Restrepo, J.; Sullivan, P.

    2004-12-01

    Oceanic surface gravity waves are approximately irrotational, weakly nonlinear, and conservative, and they have a much shorter time scale than oceanic currents and longer waves (e.g., infragravity waves) --- except where the primary surface waves break. This provides a framework for an asymptotic theory, based on separation of time (and space) scales, of wave-averaged effects associated with the conservative primary wave dynamics combined with a stochastic representation of the momentum transfer and induced mixing associated with non-conservative wave breaking. Such a theory requires only modest information about the primary wave field from measurements or operational model forecasts and thus avoids the enormous burden of calculating the waves on their intrinsically small space and time scales. For the conservative effects, the result is a vortex force associated with the primary wave's Stokes drift; a wave-averaged Bernoulli head and sea-level set-up; and an incremental material advection by the Stokes drift. This can be compared to the "radiation stress" formalism of Longuet-Higgins, Stewart, and Hasselmann; it is shown to be a preferable representation since the radiation stress is trivial at its apparent leading order. For the non-conservative breaking effects, a population of stochastic impulses is added to the current and infragravity momentum equations with distribution functions taken from measurements. In offshore wind-wave equilibria, these impulses replace the conventional surface wind stress and cause significant differences in the surface boundary layer currents and entrainment rate, particularly when acting in combination with the conservative vortex force. In the surf zone, where breaking associated with shoaling removes nearly all of the primary wave momentum and energy, the stochastic forcing plays an analogous role as the widely used nearshore radiation stress parameterizations. This talk describes the theoretical framework and presents some

  8. Gravity wave spectra in the lower stratosphere diagnosed from project loon balloon trajectories

    Science.gov (United States)

    Schoeberl, M. R.; Jensen, E.; Podglajen, A.; Coy, L.; Lodha, C.; Candido, S.; Carver, R.

    2017-08-01

    Project Loon has been launching superpressure balloons since January 2013 to provide worldwide Internet coverage. These balloons typically fly between 18 and 21 km and provide measurements of winds and pressure fluctuations in the lower stratosphere. We divide 1560 Loon flights into 3405 two-day segments for gravity wave analysis. We derive the kinetic energy spectrum from the horizontal balloon motion and estimate the temperature perturbation spectrum (proportional to the potential energy spectrum) from the pressure variations. We fit the temperature (and kinetic energy) data to the functional form T'2 = T'o2[ω/ωο)α, where ω is the wave frequency, ωο is daily frequency, T'o is the base temperature amplitude, and α is the spectral slope. Both the kinetic energy and temperature spectra show -1.9 ± 0.2 power-law dependence in the intrinsic frequency window 3-50 cycles/day. The temperature spectrum slope is weakly anticorrelated with the base temperature amplitude. We also find that the wave base temperature distribution is highly skewed. The tropical modal temperature is 0.77 K. The highest amplitude waves occur over the mountainous regions, the tropics, and the high southern latitudes. Temperature amplitudes show little height variation over our 18-21 km domain. Our results are consistent with other limited superpressure balloon analyses. The modal temperature is higher than the temperature currently used in high-frequency gravity wave parameterizations.

  9. Measurements of Overtopping Flow Time Series on the Wave Dragon, Wave Energy Converter

    DEFF Research Database (Denmark)

    Tedd, James; Kofoed, Jens Peter

    2009-01-01

    A study of overtopping flow series on the Wave Dragon prototype, a low crested device designed to maximise flow, in a real sea, is presented. This study aims to fill the gap in the literature on time series of flow overtopping low crested structures. By comparing to a simulated flow the character......A study of overtopping flow series on the Wave Dragon prototype, a low crested device designed to maximise flow, in a real sea, is presented. This study aims to fill the gap in the literature on time series of flow overtopping low crested structures. By comparing to a simulated flow...... the characteristics of the overtopping flow are discussed and the simulation algorithm is tested. Measured data is shown from a storm build up in October 2006, from theWave Dragon prototype situated in an inland sea in Northern Denmark. This wave energy converter extracts energy from the waves, by funnelling them...

  10. QBO Modulation of the Mesopause Gravity Wave Momentum Flux over Tierra del Fuego

    Science.gov (United States)

    De Wit, R. J.; Janches, D.; Fritts, D. C.; Hibbins, R. E.

    2016-01-01

    The interannual variability of the mesosphere and lower thermosphere (MLT) gravity wave momentum flux over southern mid latitudes (53.7degS) has been studied using more than 7 years of meteor radar observations at Ro Grande, Argentina. A modulation, with periods similar to that of the equatorial stratospheric quasi-biennial oscillation (QBO), is observed in the vertical flux of zonal as well as meridional momentum. The QBO signal is largest in the zonal component during summer and is in phase with the stratospheric QBO at 50 hPa (approx. 21 km). The relation between the stratospheric QBO and the QBO modulation in the MLT gravity wave forcing (derived from the divergence of the momentum flux) was found to be consistent with that expected from the Holton-Tan effect coupled to the interhemispheric coupling mechanism. These results provide the first observational support for the existence of the midlatitude gravity wave forcing anomalies as hypothesized in the interhemispheric coupling mechanism.

  11. Modeling Volcanic Eruption Parameters by Near-Source Internal Gravity Waves.

    Science.gov (United States)

    Ripepe, M; Barfucci, G; De Angelis, S; Delle Donne, D; Lacanna, G; Marchetti, E

    2016-11-10

    Volcanic explosions release large amounts of hot gas and ash into the atmosphere to form plumes rising several kilometers above eruptive vents, which can pose serious risk on human health and aviation also at several thousands of kilometers from the volcanic source. However the most sophisticate atmospheric models and eruptive plume dynamics require input parameters such as duration of the ejection phase and total mass erupted to constrain the quantity of ash dispersed in the atmosphere and to efficiently evaluate the related hazard. The sudden ejection of this large quantity of ash can perturb the equilibrium of the whole atmosphere triggering oscillations well below the frequencies of acoustic waves, down to much longer periods typical of gravity waves. We show that atmospheric gravity oscillations induced by volcanic eruptions and recorded by pressure sensors can be modeled as a compact source representing the rate of erupted volcanic mass. We demonstrate the feasibility of using gravity waves to derive eruption source parameters such as duration of the injection and total erupted mass with direct application in constraining plume and ash dispersal models.

  12. Ring waves as a mass transport mechanism in air-driven core-annular flows.

    Science.gov (United States)

    Camassa, Roberto; Forest, M Gregory; Lee, Long; Ogrosky, H Reed; Olander, Jeffrey

    2012-12-01

    Air-driven core-annular fluid flows occur in many situations, from lung airways to engineering applications. Here we study, experimentally and theoretically, flows where a viscous liquid film lining the inside of a tube is forced upwards against gravity by turbulent airflow up the center of the tube. We present results on the thickness and mean speed of the film and properties of the interfacial waves that develop from an instability of the air-liquid interface. We derive a long-wave asymptotic model and compare properties of its solutions with those of the experiments. Traveling wave solutions of this long-wave model exhibit evidence of different mass transport regimes: Past a certain threshold, sufficiently large-amplitude waves begin to trap cores of fluid which propagate upward at wave speeds. This theoretical result is then confirmed by a second set of experiments that show evidence of ring waves of annular fluid propagating over the underlying creeping flow. By tuning the parameters of the experiments, the strength of this phenomenon can be adjusted in a way that is predicted qualitatively by the model.

  13. Determination of gravity wave parameters in the airglow combining photometer and imager data

    Science.gov (United States)

    Nyassor, Prosper K.; Arlen Buriti, Ricardo; Paulino, Igo; Medeiros, Amauri F.; Takahashi, Hisao; Wrasse, Cristiano M.; Gobbi, Delano

    2018-05-01

    Mesospheric airglow measurements of two or three layers were used to characterize both vertical and horizontal parameters of gravity waves. The data set was acquired coincidentally from a multi-channel filter (Multi-3) photometer and an all-sky imager located at São João do Cariri (7.4° S, 36.5° W) in the equatorial region from 2001 to 2007. Using a least-square fitting and wavelet analysis technique, the phase and amplitude of each observed wave were determined, as well as the amplitude growth. Using the dispersion relation of gravity waves, the vertical and horizontal wavelengths were estimated and compared to the horizontal wavelength obtained from the keogram analysis of the images observed by an all-sky imager. The results show that both horizontal and vertical wavelengths, obtained from the dispersion relation and keogram analysis, agree very well for the waves observed on the nights of 14 October and 18 December 2006. The determined parameters showed that the observed wave on the night of 18 December 2006 had a period of ˜ 43.8 ± 2.19 min, with the horizontal wavelength of 235.66 ± 11.78 km having a downward phase propagation, whereas that of 14 October 2006 propagated with a period of ˜ 36.00 ± 1.80 min with a horizontal wavelength of ˜ 195 ± 9.80 km, and with an upward phase propagation. The observation of a wave taken by a photometer and an all-sky imager allowed us to conclude that the same wave could be observed by both instruments, permitting the investigation of the two-dimensional wave parameter.

  14. gravity

    Indian Academy of Sciences (India)

    We study the cosmological dynamics for R p exp( λ R ) gravity theory in the metric formalism, using dynamical systems approach. Considering higher-dimensional FRW geometries in case of an imperfect fluid which has two different scale factors in the normal and extra dimensions, we find the exact solutions, and study its ...

  15. Spectral energy transfer of atmospheric gravity waves through sum and difference nonlinear interactions

    Energy Technology Data Exchange (ETDEWEB)

    Huang, K.M. [Wuhan Univ. (China). School of Electronic Information; Chinese Academey of Sciences, Hefei (China). Key Lab. of Geospace Environment; Embry Riddle Aeronautical Univ., Daytona Beach, FL (United States). Dept. of Physical Science; Ministry of Education, Wuhan (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan (China); Liu, A.Z.; Li, Z. [Embry Riddle Aeronautical Univ., Daytona Beach, FL (United States). Dept. of Physical Science; Zhang, S.D.; Yi, F. [Wuhan Univ. (China). School of Electronic Information; Ministry of Education, Wuhan (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan (China)

    2012-07-01

    Nonlinear interactions of gravity waves are studied with a two-dimensional, fully nonlinear model. The energy exchanges among resonant and near-resonant triads are examined in order to understand the spectral energy transfer through interactions. The results show that in both resonant and near-resonant interactions, the energy exchange between two high frequency waves is strong, but the energy transfer from large to small vertical scale waves is rather weak. This suggests that the energy cascade toward large vertical wavenumbers through nonlinear interaction is inefficient, which is different from the rapid turbulence cascade. Because of considerable energy exchange, nonlinear interactions can effectively spread high frequency spectrum, and play a significant role in limiting wave amplitude growth and transferring energy into higher altitudes. In resonant interaction, the interacting waves obey the resonant matching conditions, and resonant excitation is reversible, while near-resonant excitation is not so. Although near-resonant interaction shows the complexity of match relation, numerical experiments show an interesting result that when sum and difference near-resonant interactions occur between high and low frequency waves, the wave vectors tend to approximately match in horizontal direction, and the frequency of the excited waves is also close to the matching value. (orig.)

  16. Contribution of wave-induced liquefaction in triggering hyperpycnal flows in Yellow River Estuary

    Science.gov (United States)

    Liu, X.; Jia, Y.

    2017-12-01

    Hyperpycnal flows, driven mainly by the gravity of near-bed negatively buoyant layers, are one of the most important processes for moving marine sediment across the earth. The issue of hyperpycnal flows existing in marine environment has drawn increasing scholars' attention since that was observed in situ off the Yellow River estuary in the 1980s. Most researches maintain that hyperpycnal flows in the Yellow River estuary are caused by the high-concentration sediments discharged from the Yellow River into sea, however, other mechanisms have been discounted since the sediment input from the river has been significantly changed due to climate and anthropogenic change. Here we demonstrate that wave-seabed interactions can generate hyperpycnal flows, without river input, by sediment flux convergence above an originally consolidated seabed. Using physical model experiments and multi-sensor field measurements, we characterize the composition-dependent liquefaction properties of the sediment due to wave-induced pore water pressure accumulation. This allows quantification of attenuation of sediment threshold velocity and critical shear stress (predominant variables in transport mechanics) during the liquefaction under waves. Parameterising the wave-seabed interactions in a new concept model shows that high waves propagating over the seabed sediment can act as a scarifier plough remoulding the seabed sediment. This contributes to marine hyperpycnal flows as the sediment is quickly resuspended under accumulating attenuation in strength. Therefore, the development of more integrative numerical models could supply realistic predictions of marine record in response to rising magnitude and frequency of storms.

  17. Mesospheric Temperature Measurements over Scandinavia During the Gravity Wave Life Cycle Campaign (GW-LCYCLE)

    Science.gov (United States)

    Pautet, P. D.; Taylor, M.; Kaifler, B.

    2016-12-01

    The Gravity Wave Life Cycle (GW-LCYCLE) project took place in Northern Scandinavia during the winter 2015-16. This international program focused on investigating the generation and deep propagation of atmospheric gravity waves, especially the orographic waves generated over the Scandinavian mountain range. A series of instruments was operated at several ground-based locations and on-board the DLR HALO Gulfstream V and Falcon aircrafts. As part of this project, Utah State University (USU) deployed 3 Advanced Mesospheric Temperature Mappers (AMTM) at the ALOMAR facility, Norway (operational since December 2010), at the IRF institute in Kiruna, Sweden, and at the FMI institute in Sodankylä, Finland. Each of these instruments measures the OH (3,1) rotational temperature over a large region (200x160km) at 87km altitude. During the campaign, their total coverage extended across the Scandinavian Mountain Range, from the wind side in the west to 500 km to the east in the lee of the mountains, allowing the investigation of the occurrence and evolution of gravity waves (GWs) over this part of Scandinavia. Furthermore, the AMTM in Sodankylä operated in the container housing a DLR Rayleigh lidar. Both instruments ran simultaneously and autonomously from November 2015 to April 2016, providing an unprecedented complementary high-quality data set. This presentation will introduce preliminary results obtained during this campaign, in particular the evolution of the mesospheric temperature through the winter, the analysis of mountain waves occurrence and dynamics at mesospheric altitude, as well as the investigation of interesting individual GW cases.

  18. The Origins of Air Parcels Uplifted in a Two Dimensional Gravity Wave in the Tropical Upper Troposphere During the NASA Stratosphere Troposphere Exchange Project (STEP)

    Science.gov (United States)

    Selkirk, Henry B.; Pfister, Leonhard; Chan, K. Roland; Kritz, Mark; Kelly, Ken

    1989-01-01

    During January and February 1987, as part of the Stratosphere-Troposphere Exchange Project, the NASA ER-2 made 11 flights from Darwin, Australia to investigate dehydration mechanisms in the vicinity of the tropical tropopause. After the monsoon onset in the second week of January, steady easterly flow of 15-25 ms (exp -1) was established in the upper troposphere and lower stratosphere over northern Australia and adjacent seas. Penetrating into this regime were elements of the monsoon convection such as overshooting convective turrets and extensive anvils including cyclone cloud shields. In cases of the latter, the resulting flow obstructions tended to produce mesoscale gravity waves. In several instances the ER- 2 meteorological and trace constituent measurements provide a detailed description of the structure of these gravity waves. Among these was STEP Flight 6, 22-23 January. It is of particular interest to STEP because of the close proximity of ice-laden and dehydrated air on the same isentropic surfaces. Convective events inject large amounts of ice into the upper troposphere and lower stratosphere which may not be completely removed by local precipitation processes. In the present instance, a gravity wave for removed from the source region appears to induce relativity rapid upward motion in the ice-laden air and subsequent dessication. Potential mechanisms for such a localized removal process are under investigation.

  19. A mechanistic determination of horizontal flow regime bound using void wave celerity

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.W. [Ajou Univ., Suwon (Korea, Republic of)

    1995-09-01

    The two-phase flow regime boundaries in a horizontal channel has been investigated by using the behavior of the second order void wave celerities. The average two-fluid model has been constituted with closure relations for horizontally stratified and bubbly flows. A vapor phase turbulent stress model for a smooth interface geometry has been included. It is found that the second order waves (i.e., eigenvalues) propagate in opposite direction with almost the same speed when the liquid phase is stationary. Using the well-posedness limit of the two-phase system, the dispersed-stratified flow regime boundary has been modeled. Two-phase Froude number has been theoretically found to be a convenient parameter in quantifying the flow regime boundary as a function of the void fraction. It is found that interaction between void wave celerities become stronger as the two-phase Froude number is reduced. This result should be interpreted as that gravity and the relative velocity are key parameters in determining flow regime boundaries in a horizontal flow. The influence of the vapor phase turbulent stress found to stabilize the flow stratification. This study clearly shows that the average two-fluid model is very effective for a mechanistic determination of horizontal flow regimes if appropriate closure relations are developed.

  20. A mechanistic determination of horizontal flow regime bound using void wave celerity

    International Nuclear Information System (INIS)

    Park, J.W.

    1995-01-01

    The two-phase flow regime boundaries in a horizontal channel has been investigated by using the behavior of the second order void wave celerities. The average two-fluid model has been constituted with closure relations for horizontally stratified and bubbly flows. A vapor phase turbulent stress model for a smooth interface geometry has been included. It is found that the second order waves (i.e., eigenvalues) propagate in opposite direction with almost the same speed when the liquid phase is stationary. Using the well-posedness limit of the two-phase system, the dispersed-stratified flow regime boundary has been modeled. Two-phase Froude number has been theoretically found to be a convenient parameter in quantifying the flow regime boundary as a function of the void fraction. It is found that interaction between void wave celerities become stronger as the two-phase Froude number is reduced. This result should be interpreted as that gravity and the relative velocity are key parameters in determining flow regime boundaries in a horizontal flow. The influence of the vapor phase turbulent stress found to stabilize the flow stratification. This study clearly shows that the average two-fluid model is very effective for a mechanistic determination of horizontal flow regimes if appropriate closure relations are developed

  1. Quantum Gravity Experiments

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2015-10-01

    Full Text Available A new quantum gravity experiment is reported with the data confirming the generali- sation of the Schrödinger equation to include the interaction of the wave function with dynamical space. Dynamical space turbulence, via this interaction process, raises and lowers the energy of the electron wave function, which is detected by observing conse- quent variations in the electron quantum barrier tunnelling rate in reverse-biased Zener diodes. This process has previously been reported and enabled the measurement of the speed of the dynamical space flow, which is consistent with numerous other detection experiments. The interaction process is dependent on the angle between the dynamical space flow velocity and the direction of the electron flow in the diode, and this depen- dence is experimentally demonstrated. This interaction process explains gravity as an emergent quantum process, so unifying quantum phenomena and gravity. Gravitational waves are easily detected.

  2. Testing effective quantum gravity with gravitational waves from extreme mass ratio inspirals

    International Nuclear Information System (INIS)

    Yunes, N; Sopuerta, C F

    2010-01-01

    Testing deviation of GR is one of the main goals of the proposed Laser Interferometer Space Antenna. For the first time, we consistently compute the generation of gravitational waves from extreme-mass ratio inspirals (stellar compact objects into supermassive black holes) in a well-motivated alternative theory of gravity, that to date remains weakly constrained by double binary pulsar observations. The theory we concentrate on is Chern-Simons (CS) modified gravity, a 4-D, effective theory that is motivated both from string theory and loop-quantum gravity, and which enhances the Einstein-Hilbert action through the addition of a dynamical scalar field and the parity-violating Pontryagin density. We show that although point particles continue to follow geodesics in the modified theory, the background about which they inspiral is a modification to the Kerr metric, which imprints a CS correction on the gravitational waves emitted. CS modified gravitational waves are sufficiently different from the General Relativistic expectation that they lead to significant dephasing after 3 weeks of evolution, but such dephasing will probably not prevent detection of these signals, but instead lead to a systematic error in the determination of parameters. We end with a study of radiation-reaction in the modified theory and show that, to leading-order, energy-momentum emission is not CS modified, except possibly for the subdominant effect of scalar-field emission. The inclusion of radiation-reaction will allow for tests of CS modified gravity with space-borne detectors that might be two orders of magnitude larger than current binary pulsar bounds.

  3. Comparison of the Effect of Horizontal Vibrations on Interfacial Waves in a Two-Layer System of Inviscid Liquids to Effective Gravity Inversion

    Science.gov (United States)

    Pimenova, Anastasiya V.; Goldobin, Denis S.; Lyubimova, Tatyana P.

    2018-02-01

    We study the waves at the interface between two thin horizontal layers of immiscible liquids subject to high-frequency tangential vibrations. Nonlinear governing equations are derived for the cases of two- and three-dimensional flows and arbitrary ratio of layer thicknesses. The derivation is performed within the framework of the long-wavelength approximation, which is relevant as the linear instability of a thin-layers system is long-wavelength. The dynamics of equations is integrable and the equations themselves can be compared to the Boussinesq equation for the gravity waves in shallow water, which allows one to compare the action of the vibrational field to the action of the gravity and its possible effective inversion.

  4. Quantum-Wave Equation and Heisenberg Inequalities of Covariant Quantum Gravity

    Directory of Open Access Journals (Sweden)

    Claudio Cremaschini

    2017-07-01

    Full Text Available Key aspects of the manifestly-covariant theory of quantum gravity (Cremaschini and Tessarotto 2015–2017 are investigated. These refer, first, to the establishment of the four-scalar, manifestly-covariant evolution quantum wave equation, denoted as covariant quantum gravity (CQG wave equation, which advances the quantum state ψ associated with a prescribed background space-time. In this paper, the CQG-wave equation is proved to follow at once by means of a Hamilton–Jacobi quantization of the classical variational tensor field g ≡ g μ ν and its conjugate momentum, referred to as (canonical g-quantization. The same equation is also shown to be variational and to follow from a synchronous variational principle identified here with the quantum Hamilton variational principle. The corresponding quantum hydrodynamic equations are then obtained upon introducing the Madelung representation for ψ , which provides an equivalent statistical interpretation of the CQG-wave equation. Finally, the quantum state ψ is proven to fulfill generalized Heisenberg inequalities, relating the statistical measurement errors of quantum observables. These are shown to be represented in terms of the standard deviations of the metric tensor g ≡ g μ ν and its quantum conjugate momentum operator.

  5. Impact of dissipation on the energy spectrum of experimental turbulence of gravity surface waves

    Science.gov (United States)

    Campagne, Antoine; Hassaini, Roumaissa; Redor, Ivan; Sommeria, Joël; Valran, Thomas; Viboud, Samuel; Mordant, Nicolas

    2018-04-01

    We discuss the impact of dissipation on the development of the energy spectrum in wave turbulence of gravity surface waves with emphasis on the effect of surface contamination. We performed experiments in the Coriolis facility, which is a 13-m-diam wave tank. We took care of cleaning surface contamination as well as possible, considering that the surface of water exceeds 100 m2. We observe that for the cleanest condition the frequency energy spectrum shows a power-law decay extending up to the gravity capillary crossover (14 Hz) with a spectral exponent that is increasing with the forcing strength and decaying with surface contamination. Although slightly higher than reported previously in the literature, the exponent for the cleanest water remains significantly below the prediction from the weak turbulence theory. By discussing length and time scales, we show that weak turbulence cannot be expected at frequencies above 3 Hz. We observe with a stereoscopic reconstruction technique that the increase with the forcing strength of energy spectrum beyond 3 Hz is mostly due to the formation and strengthening of bound waves.

  6. A one-dimensional model of the semiannual oscillation driven by convectively forced gravity waves

    Science.gov (United States)

    Sassi, Fabrizio; Garcia, Rolando R.

    1994-01-01

    A one-dimensional model that solves the time-dependent equations for the zonal mean wind and a wave of specified zonal wavenumber has been used to illustrate the ability of gravity waves forced by time-dependent tropospheric heating to produce a semiannual oscillation (SAO) in the middle atmosphere. When the heating has a strong diurnal cycle, as observed over tropical landmasses, gravity waves with zonal wavelengths of a few thousand kilometers and phase velocities in the range +/- 40-50 m/sec are excited efficiently by the maximum vertical projection criterion (vertical wavelength approximately equals 2 x forcing depth). Calculations show that these waves can account for large zonal mean wind accelerations in the middle atmosphere, resulting in realistic stratopause and mesopause oscillations. Calculations of the temporal evolution of a quasi-conserved tracer indicate strong down-welling in the upper stratosphere near the equinoxes, which is associated with the descent of the SAO westerlies. In the upper mesosphere, there is a semiannual oscillation in tracer mixing ratio driven by seasonal variability in eddy mixing, which increases at the solstices and decreases at the equinoxes.

  7. Correlation of Normal Gravity Mixed Convection Blowoff Limits with Microgravity Forced Flow Blowoff Limits

    Science.gov (United States)

    Marcum, Jeremy W.; Olson, Sandra L.; Ferkul, Paul V.

    2016-01-01

    The axisymmetric rod geometry in upward axial stagnation flow provides a simple way to measure normal gravity blowoff limits to compare with microgravity Burning and Suppression of Solids - II (BASS-II) results recently obtained aboard the International Space Station. This testing utilized the same BASS-II concurrent rod geometry, but with the addition of normal gravity buoyant flow. Cast polymethylmethacrylate (PMMA) rods of diameters ranging from 0.635 cm to 3.81 cm were burned at oxygen concentrations ranging from 14 to 18% by volume. The forced flow velocity where blowoff occurred was determined for each rod size and oxygen concentration. These blowoff limits compare favorably with the BASS-II results when the buoyant stretch is included and the flow is corrected by considering the blockage factor of the fuel. From these results, the normal gravity blowoff boundary for this axisymmetric rod geometry is determined to be linear, with oxygen concentration directly proportional to flow speed. We describe a new normal gravity 'upward flame spread test' method which extrapolates the linear blowoff boundary to the zero stretch limit in order to resolve microgravity flammability limits-something current methods cannot do. This new test method can improve spacecraft fire safety for future exploration missions by providing a tractable way to obtain good estimates of material flammability in low gravity.

  8. Traveling waves in a magnetized Taylor-Couette flow

    International Nuclear Information System (INIS)

    Liu Wei; Ji Hantao; Goodman, Jeremy

    2007-01-01

    We investigate numerically a traveling wave pattern observed in experimental magnetized Taylor-Couette flow at low magnetic Reynolds number. By accurately modeling viscous and magnetic boundaries in all directions, we reproduce the experimentally measured wave patterns and their amplitudes. Contrary to previous claims, the waves are shown to be transiently amplified disturbances launched by viscous boundary layers, rather than globally unstable magnetorotational modes

  9. A Note on Standing Internal Inertial Gravity Waves of Finite Amplitude

    Science.gov (United States)

    Thorpe, S. A.

    2003-01-01

    The effects of finite amplitude are examined in two-dimensional, standing, internal gravity waves in a rectangular container which rotates about a vertical axis at frequency f/2. Expressions are given for the velocity components, density fluctuations and isopycnal displacements to second order in the wave steepness in fluids with buoyancy frequency, N, of general form, and the effect of finite amplitude on wave frequency is given in an expansion to third order. The first order solutions, and the solutions to second order in the absence of rotation, are shown to conserve energy during a wave cycle. Analytical solutions are found to second order for the first two modes in a deep fluid with N proportional to sech(az), where z is the upward vertical coordinate and a is scaling factor. In the absence of rotation, results for the first mode in the latter stratification are found to be consistent with those for interfacial waves. An analytical solution to fourth order in a fluid with constant N is given and used to examine the effects of rotation on the development of static instability or of conditions in which shear instability may occur. As in progressive internal waves, an effect of rotation is to enhance the possibility of shear instability for waves with frequencies close to f. The analysis points to a significant difference between the dynamics of standing waves in containers of limited size and progressive internal waves in an unlimited fluid; the effect of boundaries on standing waves may inhibit the onset of instability. A possible application of the analysis is to transverse oscillations in long, narrow, steep-sided lakes such as Loch Ness, Scotland.

  10. Gravitational waves during inflation from a 5D large-scale repulsive gravity model

    International Nuclear Information System (INIS)

    Reyes, Luz M.; Moreno, Claudia; Madriz Aguilar, José Edgar; Bellini, Mauricio

    2012-01-01

    We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.

  11. Gravitational waves during inflation from a 5D large-scale repulsive gravity model

    Science.gov (United States)

    Reyes, Luz M.; Moreno, Claudia; Madriz Aguilar, José Edgar; Bellini, Mauricio

    2012-10-01

    We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.

  12. Gravitational waves during inflation from a 5D large-scale repulsive gravity model

    Energy Technology Data Exchange (ETDEWEB)

    Reyes, Luz M., E-mail: luzmarinareyes@gmail.com [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Moreno, Claudia, E-mail: claudia.moreno@cucei.udg.mx [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Madriz Aguilar, Jose Edgar, E-mail: edgar.madriz@red.cucei.udg.mx [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Bellini, Mauricio, E-mail: mbellini@mdp.edu.ar [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata (UNMdP), Funes 3350, C.P. 7600, Mar del Plata (Argentina); Instituto de Investigaciones Fisicas de Mar del Plata (IFIMAR) - Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina)

    2012-10-22

    We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.

  13. Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure

    Energy Technology Data Exchange (ETDEWEB)

    Lombriser, Lucas, E-mail: llo@roe.ac.uk; Lima, Nelson A.

    2017-02-10

    With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar–tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar–tensor modification of gravity.

  14. Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure

    Science.gov (United States)

    Lombriser, Lucas; Lima, Nelson A.

    2017-02-01

    With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar-tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar-tensor modification of gravity.

  15. Simple analytical methods for computing the gravity-wave contribution to the cosmic background radiation anisotropy

    International Nuclear Information System (INIS)

    Wang, Y.

    1996-01-01

    We present two simple analytical methods for computing the gravity-wave contribution to the cosmic background radiation (CBR) anisotropy in inflationary models; one method uses a time-dependent transfer function, the other methods uses an approximate gravity-mode function which is a simple combination of the lowest order spherical Bessel functions. We compare the CBR anisotropy tensor multipole spectrum computed using our methods with the previous result of the highly accurate numerical method, the open-quote open-quote Boltzmann close-quote close-quote method. Our time-dependent transfer function is more accurate than the time-independent transfer function found by Turner, White, and Lindsey; however, we find that the transfer function method is only good for l approx-lt 120. Using our approximate gravity-wave mode function, we obtain much better accuracy; the tensor multipole spectrum we find differs by less than 2% for l approx-lt 50, less than 10% for l approx-lt 120, and less than 20% for l≤300 from the open-quote open-quote Boltzmann close-quote close-quote result. Our approximate graviton mode function should be quite useful in studying tensor perturbations from inflationary models. copyright 1996 The American Physical Society

  16. Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure

    Directory of Open Access Journals (Sweden)

    Lucas Lombriser

    2017-02-01

    Full Text Available With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar–tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar–tensor modification of gravity.

  17. Gravity wave-driven fluctuations in OH nightglow from an extended, dissipative emission region

    International Nuclear Information System (INIS)

    Schubert, G.; Walterscheid, R.L.; Hickey, M.P.

    1991-01-01

    The theory of gravity wave-driven fluctuations in the OH nightglow from an extended source region is generalized to account for effects of eddy kinematic viscosity v and eddy thermal diffusivity κ. In the nondiffusive case, the amplitudes and phases of vertically integrated normalized intensity (δI)/(bar I) and temperature (δT 1 )/(bar T 1 ) perturbations and vertically integrated Krassovsky's ratio (η) as functions of period are influenced by the upper limit of vertical integration of the extended source, especially at long periods when vertical wavelengths γ v are small. The effects, which include oscillations in (δT)/(bar I), (δT 1 )/(bar T 1 ), and (η), particularly at long periods, are due to constructive and destructive interference of nightglow signals from vertically separated levels of the OH emitting region that occur when γ v is comparable to or smaller than the thickness of the main emission region. The sensitivity of these ratios to the upper limit of vertical integration occurs because of the relatively small rate of decay of the intensity of OH emission with height above the peak emission level and the exponential growth with altitude of nondissipative gravity waves. Because eddy diffusion increases γ v , especially at long periods, and reduces wave growth with height compared with the case v = κ = 0, inclusion of eddy diffusion removes the sensitivity of (η) and the other ratios ot the maximum height of vertical integration. It is essential to account for both eddy diffusion and emission from the entire vertically extended emission region to correctly predict (η), (δI)/(bar I), and (δT 1 )/(bar T 1 ) at long gravity wave periods

  18. Tsunami mitigation by resonant triad interaction with acoustic-gravity waves.

    Science.gov (United States)

    Kadri, Usama

    2017-01-01

    Tsunamis have been responsible for the loss of almost a half million lives, widespread long lasting destruction, profound environmental effects, and global financial crisis, within the last two decades. The main tsunami properties that determine the size of impact at the shoreline are its wavelength and amplitude in the ocean. Here, we show that it is in principle possible to reduce the amplitude of a tsunami, and redistribute its energy over a larger space, through forcing it to interact with resonating acoustic-gravity waves. In practice, generating the appropriate acoustic-gravity modes introduces serious challenges due to the high energy required for an effective interaction. However, if the findings are extended to realistic tsunami properties and geometries, we might be able to mitigate tsunamis and so save lives and properties. Moreover, such a mitigation technique would allow for the harnessing of the tsunami's energy.

  19. Acoustic Gravity Waves Generated by an Oscillating Ice Sheet in Arctic Zone

    Science.gov (United States)

    Abdolali, A.; Kadri, U.; Kirby, J. T., Jr.

    2016-12-01

    We investigate the formation of acoustic-gravity waves due to oscillations of large ice blocks, possibly triggered by atmospheric and ocean currents, ice block shrinkage or storms and ice-quakes.For the idealized case of a homogeneous weakly compressible water bounded at the surface by ice sheet and a rigid bed, the description of the infinite family of acoustic modes is characterized by the water depth h and angular frequency of oscillating ice sheet ω ; The acoustic wave field is governed by the leading mode given by: Nmax=\\floor {(ω h)/(π c)} where c is the sound speed in water and the special brackets represent the floor function (Fig1). Unlike the free-surface setting, the higher acoustic modes might exhibit a larger contribution and therefore all progressive acoustic modes have to be considered.This study focuses on the characteristics of acoustic-gravity waves generated by an oscillating elastic ice sheet in a weakly compressible fluid coupled with a free surface model [Abdolali et al. 2015] representing shrinking ice blocks in realistic sea state, where the randomly oriented ice sheets cause inter modal transition and multidirectional reflections. A theoretical solution and a 3D numerical model have been developed for the study purposes. The model is first validated against the theoretical solution [Kadri, 2016]. To overcome the computational difficulties of 3D models, we derive a depth-integrated equation valid for spatially varying ice sheet thickness and water depth. We show that the generated acoustic-gravity waves contribute significantly to deep ocean currents compared to other mechanisms. In addition, these waves travel at the sound speed in water carrying information on ice sheet motion, providing various implications for ocean monitoring and detection of ice-quakes. Fig1:Snapshots of dynamic pressure given by an oscillating ice sheet; h=4500m, c=1500m/s, semi-length b=10km, ζ =1m, omega=π rad/s. Abdolali, A., Kirby, J. T. and Bellotti, G

  20. Recent progress in mesospheric gravity wave studies using nightglow imaging system

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Michael J.; Pendleton Junior, William R.; Pautet, Pierre-Dominique; Zhao, Yucheng; Olsen, Chris; Babu, Hema Karnam Surendra [Center for Atmospheric and Space Sciences, Utah State University, Logan, Utah (United States); Medeiros, Amauri F. [Universidade Federal de Campina Grande, Centro de Ciencias e Tecnologia, Unidade Academica de Fisica, Campina Grande, PB (Brazil); Takahashi, Hisao, E-mail: mtaylor@cc.usu.edu, E-mail: wpen@cc.usu.edu, E-mail: dominiquepautet@gmail.com, E-mail: yucheng@cc.usu.edu, E-mail: cmellob@gmail.com, E-mail: hema_sb@rediffmail.com, E-mail: afragoso@df.ufcg.edu.br, E-mail: hisaotak@laser.inpe.br [INPE, Sao Jose dos Campos, SP (Brazil)

    2007-07-01

    A variety of optical remote sensing techniques have now revealed a rich spectrum of wave activity in the upper atmosphere. Many of these perturbations, with periodicities ranging from {approx} 5 min to many hours and horizontal scales of a few tens of km to several thousands km, are due to freely propagating atmospheric gravity waves and forced tidal oscillations. Passive optical observations of the spatial and temporal characteristics of these waves in the mesosphere and lower thermosphere (MLT) region ( {approx} 80-100 km) are facilitated by several naturally occurring, vertically distinct nightglow layers. This paper describes the use of state-of-the-art ground-based CCD imaging techniques to detect these waves in intensity and temperature. All-sky (180 deg ) image measurements are used to illustrate the characteristics of small-scale, short period ( < 1 hour) waves and to investigate their seasonal propagation and momentum impact on the MLT region. These results are then contrasted with measurements of mesospheric temperature made using a new temperature mapping imaging system capable of determining induced temperature amplitudes of a large range of wave motions and investigating night-to-night and seasonal variability in mesospheric temperature. (author)

  1. Instability of combined gravity-inertial-Rossby waves in atmospheres and oceans

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2011-06-01

    Full Text Available The properties of the instability of combined gravity-inertial-Rossby waves on a β-plane are investigated. The wave-energy exchange equation shows that there is an exchange of energy with the background stratified medium. The energy source driving the instability lies in the background enthalpy released by the gravitational buoyancy force. It is shown that if the phase speed of the westward propagating low frequency-long wavelength Rossby wave exceeds the Poincaré-Kelvin (or "equivalent" shallow water wave speed, instability arises from the merging of Rossby and Poincaré modes. There are two key parameters in this instability condition; namely, the equatorial/rotational Mach (or Froude number M and the latitude θ0 of the β-plane. In general waves equatorward of a critical latitude for given M can be driven unstable, with corresponding growth rates of the order of a day or so. Although these conclusions may only be safely drawn for short wavelengths corresponding to a JWKB wave packet propagating internally and located far from boundaries, nevertheless such a local instability may play a significant role in atmosphere-ocean dynamics.

  2. Opposed-Flow Flame Spread over Thin Solid Fuels in a Narrow Channel under Different Gravity

    Science.gov (United States)

    Zhang, Xia; Yu, Yong; Wan, Shixin; Wei, Minggang; Hu, Wen-Rui

    Flame spread over solid surface is critical in combustion science due to its importance in fire safety in both ground and manned spacecraft. Eliminating potential fuels from materials is the basic method to protect spacecraft from fire. The criterion of material screening is its flamma-bility [1]. Since gas flow speed has strong effect on flame spread, the combustion behaviors of materials in normal and microgravity will be different due to their different natural convec-tion. To evaluate the flammability of materials used in the manned spacecraft, tests should be performed under microgravity. Nevertheless, the cost is high, so apparatus to simulate mi-crogravity combustion under normal gravity was developed. The narrow channel is such an apparatus in which the buoyant flow is restricted effectively [2, 3]. The experimental results of the horizontal narrow channel are consistent qualitatively with those of Mir Space Station. Quantitatively, there still are obvious differences. However, the effect of the channel size on flame spread has only attracted little attention, in which concurrent-flow flame spread over thin solid in microgravity is numerically studied[4], while the similarity of flame spread in different gravity is still an open question. In addition, the flame spread experiments under microgravity are generally carried out in large wind tunnels without considering the effects of the tunnel size [5]. Actually, the materials are always used in finite space. Therefore, the flammability given by experiments using large wind tunnels will not correctly predict the flammability of materials in the real environment. In the present paper, the effect of the channel size on opposed-flow flame spread over thin solid fuels in both normal and microgravity was investigated and compared. In the horizontal narrow channel, the flame spread rate increased before decreased as forced flow speed increased. In low speed gas flows, flame spread appeared the same trend as that in

  3. Vertical Transport of Momentum by the Inertial-Gravity Internal Waves in a Baroclinic Current

    Directory of Open Access Journals (Sweden)

    A. A. Slepyshev

    2017-08-01

    Full Text Available When the internal waves break, they are one of the sources of small-scale turbulence. Small-scale turbulence causes the vertical exchange in the ocean. However, internal waves with regard to the Earth rotation in the presence of vertically inhomogeneous two-dimensional current are able to contribute to the vertical transport. Free inertial-gravity internal waves in a baroclinic current in a boundless basin of a constant depth are considered in the Bussinesq approximation. Boundary value problem of linear approximation for the vertical velocity amplitude of internal waves has complex coefficients when current velocity component, which is transversal to the wave propagation direction, depends on the vertical coordinate (taking into account the rotation of the Earth. Eigenfunction and wave frequency are complex, and it is shown that a weak wave damping takes place. Dispersive relation and wave damping decrement are calculated in the linear approximation. At a fixed wave number damping decrement of the second mode is larger (in the absolute value than the one of the first mode. The equation for vertical velocity amplitude for real profiles of the Brunt – Vaisala frequency and current velocity are numerically solved according to implicit Adams scheme of the third order of accuracy. The dispersive curves of the first two modes do not reach inertial frequency in the low-frequency area due to the effect of critical layers in which wave frequency of the Doppler shift is equal to the inertial one. Termination of the second mode dispersive curves takes place at higher frequency than the one of the first mode. In the second order of the wave amplitude the Stokes drift speed is determined. It is shown that the Stokes drift speed, which is transversal to the wave propagation direction, differs from zero if the transversal component of current velocity depends on the vertical coordinate. In this case, the Stokes drift speed in the second mode is lower than

  4. Instability of two-layer film flows due to the interacting effects of surfactants, inertia, and gravity

    Science.gov (United States)

    Kalogirou, Anna

    2018-03-01

    We consider a two-fluid shear flow where the interface between the two fluids is coated with an insoluble surfactant. An asymptotic model is derived in the thin-layer approximation, consisting of a set of nonlinear partial differential equations describing the evolution of the film and surfactant disturbances at the interface. The model includes important physical effects such as Marangoni forces (caused by the presence of surfactant), inertial forces arising in the thick fluid layer, as well as gravitational forces. The aim of this study is to investigate the effect of density stratification or gravity—represented through the Bond number Bo—on the flow stability and the interplay between the different (de)stabilisation mechanisms. It is found that gravity can either stabilise or destabilise the interface (depending on fluid properties) but not always as intuitively anticipated. Different traveling-wave branches are presented for varying Bo, and the destabilising mechanism associated with the Marangoni forces is discussed.

  5. Effective gravitational wave stress-energy tensor in alternative theories of gravity

    International Nuclear Information System (INIS)

    Stein, Leo C.; Yunes, Nicolas

    2011-01-01

    The inspiral of binary systems in vacuum is controlled by the stress-energy of gravitational radiation and any other propagating degrees of freedom. For gravitational waves, the dominant contribution is characterized by an effective stress-energy tensor at future null infinity. We employ perturbation theory and the short-wavelength approximation to compute this stress-energy tensor in a wide class of alternative theories. We find that this tensor is generally a modification of that first computed by Isaacson, where the corrections can dominate over the general relativistic term. In a wide class of theories, however, these corrections identically vanish at asymptotically flat, future, null infinity, reducing the stress-energy tensor to Isaacson's. We exemplify this phenomenon by first considering dynamical Chern-Simons modified gravity, which corrects the action via a scalar field and the contraction of the Riemann tensor and its dual. We then consider a wide class of theories with dynamical scalar fields coupled to higher-order curvature invariants and show that the gravitational wave stress-energy tensor still reduces to Isaacson's. The calculations presented in this paper are crucial to perform systematic tests of such modified gravity theories through the orbital decay of binary pulsars or through gravitational wave observations.

  6. Gravity Effect on Two-Phase Immiscible Flows in Communicating Layered Reservoirs

    DEFF Research Database (Denmark)

    Zhang, Xuan; Shapiro, Alexander; Stenby, Erling Halfdan

    2012-01-01

    An upscaling method is developed for two-phase immiscible incompressible flows in layered reservoirs with good communication between the layers. It takes the effect of gravity into consideration. Waterflooding of petroleum reservoirs is used as a basic example for application of this method....... An asymptotic analysis is applied to a system of 2D flow equations for incompressible fluids at high-anisotropy ratios, but low to moderate gravity ratios, which corresponds to the most often found reservoir conditions. The 2D Buckley–Leverett problem is reduced to a system of 1D parabolic equations...

  7. Air Flows in Gravity Sewers - Determination of Wastewater Drag Coefficient

    DEFF Research Database (Denmark)

    Bentzen, Thomas Ruby; Østertoft, Kristian; Vollertsen, Jes

    2016-01-01

    Several experiments have been conducted in order to improve the understanding of the wastewater drag and the wall frictional force acting on the headspace air in gravity sewers. The aim of the study is to improve the data basis for a numerical model of natural sewer ventilation. The results...... of the study shows that by integrating the top/side wall shear stresses the log-law models for the air velocity distribution along the unwetted perimeter resulted in a good agreement with the friction forces calculated by use of the Colebrook-White formula for hydraulic smooth pipes. Secondly, the water...

  8. Imaging gravity waves in lower stratospheric AMSU-A radiances, Part 2: Validation case study

    Directory of Open Access Journals (Sweden)

    S. D. Eckermann

    2006-01-01

    , horizontal structure and time evolution that closely match those observed in the AMSU-A data. These comparisons not only verify gravity wave detection and horizontal imaging capabilities for AMSU-A Channel 9, but provide an absolute validation of the anticipated radiance signals for a given three-dimensional gravity wave, based on the modeling of Eckermann and Wu (2006.

  9. Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign. Part I. Observations with collocated radars

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, P.; Serafimovich, A.; Peters, D.; Latteck, R. [Leibniz-Inst. fuer Atmosphaerenphysik, Kuehlungsborn (Germany); Dalin, P. [Swedish Inst. of Space Physics, Kiruna (Sweden); Goldberg, R. [NASA/Goddard Space Flight Center, Greenbelt, MD (United States)

    2006-07-01

    During the MaCWAVE campaign, combined rocket, radiosonde and ground-based measurements have been performed at the Norwegian Andoeya rocket range (ARR) near Andenes and the Swedish rocket range (ESRANGE) near Kiruna in January 2003 to study gravity waves in the vicinity of the Scandinavian mountain ridge. The investigations presented here are mainly based on the evaluation of continuous radar measurements with the ALWIN VHP radar in the upper troposphere/ lower stratosphere at Andenes (69.3 N, 16.0 E) and the ESRAD VHP radar near Kiruna (67.9 N, 21.9 E). Both radars are separated by about 260 km. Based on wavelet transformations of both data sets, the strongest activity of inertia gravity waves in the upper troposphere has been detected during the first period from 24-26 January 2003 with dominant vertical wavelengths of about 4-5 km as well as with dominant observed periods of about 13-14 h for the altitude range between 5 and 8 km under the additional influence of mountain waves. The results show the appearance of dominating inertia gravity waves with characteristic horizontal wavelengths of {proportional_to}200 km moving in the opposite direction than the mean background wind. The results show the appearance of dominating inertia gravity waves with intrinsic periods in the order of {proportional_to}5 h and with horizontal wavelengths of 200 km, moving in the opposite direction than the mean background wind. From the derived downward energy propagation it is supposed, that these waves are likely generated by a jet streak in the upper troposphere. The parameters of the jet-induced gravity waves have been estimated at both sites separately. The identified gravity waves are coherent at both locations and show higher amplitudes on the east-side of the Scandinavian mountain ridge, as expected by the influence of mountains. (orig.)

  10. Extreme gravity tests with gravitational waves from compact binary coalescences: (II) ringdown

    Science.gov (United States)

    Berti, Emanuele; Yagi, Kent; Yang, Huan; Yunes, Nicolás

    2018-05-01

    The LIGO/Virgo detections of binary black hole mergers marked a watershed moment in astronomy, ushering in the era of precision tests of Kerr dynamics. We review theoretical and experimental challenges that must be overcome to carry out black hole spectroscopy with present and future gravitational wave detectors. Among other topics, we discuss quasinormal mode excitation in binary mergers, astrophysical event rates, tests of black hole dynamics in modified theories of gravity, parameterized "post-Kerr" ringdown tests, exotic compact objects, and proposed data analysis methods to improve spectroscopic tests of Kerr dynamics by stacking multiple events.

  11. Distance measurement and wave dispersion in a Liouville-string approach to quantum gravity

    CERN Document Server

    Amelino-Camelia, G; Mavromatos, Nikolaos E; Nanopoulos, Dimitri V

    1997-01-01

    Within a Liouville approach to non-critical string theory, we discuss space-time foam effects on the propagation of low-energy particles. We find an induced frequency-dependent dispersion in the propagation of a wave packet, and observe that this would affect the outcome of measurements involving low-energy particles as probes. In particular, the maximum possible order of magnitude of the space-time foam effects would give rise to an error in the measurement of distance comparable to that independently obtained in some recent heuristic quantum-gravity analyses. We also briefly compare these error estimates with the precision of astrophysical measurements.

  12. Two-dimensional flow characteristics of wave interactions with a free-rolling rectangular structure

    Energy Technology Data Exchange (ETDEWEB)

    Kwang Hyo Jung; Kuang-An Chang [Texas A and M University, College Station, TX (United States). Dept. of Civil Engineering; Huang, E.T. [Naval Facilities Engineering Service Center, Port Hueneme, CA (United States). Amphibious System Div.

    2005-01-01

    This paper presents laboratory observations of flow characteristics for regular waves passing a rectangular structure in a two-dimensional wave tank. The structure with a draft one-half of its height was hinged at the center of gravity and free to roll (one degree of freedom) by waves. Particle image velocimetry (PIV) was used to measure the velocity field in the vicinity of the structure. The mean velocity and turbulence properties were obtained by phase-averaging the PIV velocity maps from repeated test runs. Since the viscous damping (also called the eddy making damping) in a vortical flow affects the roll motion of a blunt body, the quantitative flow pattern was represented to elucidate the coupled interactions between the body motion and the waves. Additionally, the turbulence properties including the turbulence length scale and the turbulent kinetic energy budget were investigated to characterize the interactions. The results show that vortices were generated near the structure corners at locations opposing to that of the roll damping effect for waves with a period longer than the roll natural period of the structure. (Author)

  13. Holography as a highly efficient renormalization group flow. I. Rephrasing gravity

    Science.gov (United States)

    Behr, Nicolas; Kuperstein, Stanislav; Mukhopadhyay, Ayan

    2016-07-01

    We investigate how the holographic correspondence can be reformulated as a generalization of Wilsonian renormalization group (RG) flow in a strongly interacting large-N quantum field theory. We first define a highly efficient RG flow as one in which the Ward identities related to local conservation of energy, momentum and charges preserve the same form at each scale. To achieve this, it is necessary to redefine the background metric and external sources at each scale as functionals of the effective single-trace operators. These redefinitions also absorb the contributions of the multitrace operators to these effective Ward identities. Thus, the background metric and external sources become effectively dynamical, reproducing the dual classical gravity equations in one higher dimension. Here, we focus on reconstructing the pure gravity sector as a highly efficient RG flow of the energy-momentum tensor operator, leaving the explicit constructive field theory approach for generating such RG flows to the second part of the work. We show that special symmetries of the highly efficient RG flows carry information through which we can decode the gauge fixing of bulk diffeomorphisms in the corresponding gravity equations. We also show that the highly efficient RG flow which reproduces a given classical gravity theory in a given gauge is unique provided the endpoint can be transformed to a nonrelativistic fixed point with a finite number of parameters under a universal rescaling. The results obtained here are used in the second part of this work, where we do an explicit field-theoretic construction of the RG flow and obtain the dual classical gravity theory.

  14. Planetary-Scale Inertio Gravity Waves in the Numerical Spectral Model

    Science.gov (United States)

    Mayr, H. G.; Mengel, J. R.; Talaat, E. R.; Porter, H. S.

    2004-01-01

    In the polar region of the upper mesosphere, horizontal wind oscillations have been observed with periods around 10 hours. Waves with such a period are generated in our Numerical Spectral Model (NSM), and they are identified as planetary-scale inertio gravity waves (IGW). These IGWs have periods between 9 and 11 hours and appear above 60 km in the zonal mean (m = 0), as well as in zonal wavenumbers m = 1 to 4. The waves can propagate eastward and westward and have vertical wavelengths around 25 km. The amplitudes in the wind field are typically between 10 and 20 m/s and can reach 30 m/s in the westward propagating component for m = 1 at the poles. In the temperature perturbations, the wave amplitudes above 100 km are typically 5 K and as large as 10 K for m = 0 at the poles. The IGWs are intermittent but reveal systematic seasonal variations, with the largest amplitudes occurring generally in late winter and spring. In the NSM, the IGW are generated like the planetary waves (PW). They are produced apparently by the instabilities that arise in the zonal mean circulation. Relative to the PWs, however, the IGWs propagate zonally with much larger velocities, such that they are not affected much by interactions with the background zonal winds. Since the IGWs can propagate through the mesosphere without much interaction, except for viscous dissipation, one should then expect that they reach the thermosphere with significant and measurable amplitudes.

  15. Identification of two-phase flow regimes under variable gravity conditions

    International Nuclear Information System (INIS)

    Kamiel S Gabriel; Huawei Han

    2005-01-01

    Full text of publication follows: Two-phase flow is becoming increasingly important as we move into new and more aggressive technologies in the twenty-first century. Some of its many applications include the design of efficient heat transport systems, the transfer and storage of cryogenic fluids, and condensation and flow boiling processes in heat exchangers and energy transport systems. Two-phase flow has many applications in reduced gravity environments experienced in orbiting spacecraft and earth observation satellites. Examples are heat transport systems, the transfer and storage of cryogenic fluids, and condensation and flow boiling processes in heat exchangers. A concave parallel plate capacitance sensor has been developed to measure void fraction for the purpose of objectively identifying flow regimes. The sensor has been used to collect void-fraction data at microgravity conditions aboard the NASA and ESA zero-gravity aircraft. It is shown that the flow regimes can be objectively determined from the probability density functions of the void fraction signals. It was shown that under microgravity conditions four flow regimes exist: bubbly flow, characterized by discrete gas bubbles flowing in the liquid; slug flow, consisting of Taylor bubbles separated by liquid slugs which may or may not contain several small gas bubbles; transitional flow, characterized by the liquid flowing as a film at the tube wall, and the gas phase flowing in the center with the frequent appearance of chaotic, unstable slugs; and annular flow in which the liquid flows as a film along the tube wall and the gas flows uninterrupted through the center. Since many two-phase flow models are flow regime dependent, a method that can accurately and objectively determine flow regimes is required. (authors)

  16. Identification of two-phase flow regimes under variable gravity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kamiel S Gabriel [University of Ontario Institute of Technology 2000 Simcoe Street North, Oshawa, ON L1H 7K4 (Canada); Huawei Han [Mechanical Engineering Department, University of Saskatchewan 57 Campus Dr., Saskatoon, Saskatchewan, S7N 5A9 (Canada)

    2005-07-01

    Full text of publication follows: Two-phase flow is becoming increasingly important as we move into new and more aggressive technologies in the twenty-first century. Some of its many applications include the design of efficient heat transport systems, the transfer and storage of cryogenic fluids, and condensation and flow boiling processes in heat exchangers and energy transport systems. Two-phase flow has many applications in reduced gravity environments experienced in orbiting spacecraft and earth observation satellites. Examples are heat transport systems, the transfer and storage of cryogenic fluids, and condensation and flow boiling processes in heat exchangers. A concave parallel plate capacitance sensor has been developed to measure void fraction for the purpose of objectively identifying flow regimes. The sensor has been used to collect void-fraction data at microgravity conditions aboard the NASA and ESA zero-gravity aircraft. It is shown that the flow regimes can be objectively determined from the probability density functions of the void fraction signals. It was shown that under microgravity conditions four flow regimes exist: bubbly flow, characterized by discrete gas bubbles flowing in the liquid; slug flow, consisting of Taylor bubbles separated by liquid slugs which may or may not contain several small gas bubbles; transitional flow, characterized by the liquid flowing as a film at the tube wall, and the gas phase flowing in the center with the frequent appearance of chaotic, unstable slugs; and annular flow in which the liquid flows as a film along the tube wall and the gas flows uninterrupted through the center. Since many two-phase flow models are flow regime dependent, a method that can accurately and objectively determine flow regimes is required. (authors)

  17. Seasonal and nightly variations of gravity-wave energy density in the middle atmosphere measured by the Purple Crow Lidar

    Directory of Open Access Journals (Sweden)

    R. J. Sica

    2007-11-01

    Full Text Available The Purple Crow Lidar (PCL is a large power-aperture product monostatic Rayleigh-Raman-Sodium-resonance-fluorescence lidar, which has been in operation at the Delaware Observatory (42.9° N, 81.4° W, 237 m elevation near the campus of The University of Western Ontario since 1992. Kinetic-energy density has been calculated from the Rayleigh-scatter system measurements of density fluctuations at temporal-spatial scales relevant for gravity waves, e.g. soundings at 288 m height resolution and 9 min temporal resolution in the upper stratosphere and mesosphere. The seasonal averages from 10 years of measurements show in all seasons some loss of gravity-wave energy in the upper stratosphere. During the equinox periods and summer the measurements are consistent with gravity waves growing in height with little saturation, in agreement with the classic picture of the variations in the height at which gravity waves break given by Lindzen (1981. The mean values compare favourably to previous measurements when computed as nightly averages, but the high temporal-spatial resolution measurements show considerable day-to-day variability. The variability over a night is often extremely large, with typical RMS fluctuations of 50 to 100% at all heights and seasons common. These measurements imply that using a daily or nightly-averaged gravity-wave energy density in numerical models may be highly unrealistic.

  18. Studies of Gravity Waves Using Michelson Interferometer Measurements of OH (3-1) Bands

    Science.gov (United States)

    Won, Young-In; Cho, Young-Min; Lee, Bang Yong; Kim, J.

    2001-06-01

    As part of a long-term program for polar upper atmospheric studies, temperatures and intensities of the OH (3-1) bands were derived from spectrometric observations of airglow emissions over King Sejong station (62.22o S, 301.25o E). These measurements were made with a Michelson interferometer to cover wavelength regions between 1000 nm and 2000 nm. A spectral analysis was performed to individual nights of data to acquire information on the waves in the upper mesosphere/lower thermosphere. It is assumed that the measured fluctuations in the intensity and temperature of the OH (3-1) airglow were caused by gravity waves propagating through the emission layer. Correlation of intensity and temperature variation revealed oscillations with periods ranging from 2 to 9 hours. We also calculated Krassovsky's parameter and compared with published values.

  19. Studies of Gravity Waves Using Michelson Interferometer Measurements of OH (3-1 Bands

    Directory of Open Access Journals (Sweden)

    Young-In Won

    2001-06-01

    Full Text Available As part of a long-term program for polar upper atmospheric studies, temperatures and intensities of the OH (3-1 bands were derived from spectrometric observations of airglow emissions over King Sejong station (62.22o S, 301.25o E. These measurements were made with a Michelson interferometer to cover wavelength regions between 1000 nm and 2000 nm. A spectral analysis was performed to individual nights of data to acquire information on the waves in the upper mesosphere/lower thermosphere. It is assumed that the measured fluctuations in the intensity and temperature of the OH (3-1 airglow were caused by gravity waves propagating through the emission layer. Correlation of intensity and temperature variation revealed oscillations with periods ranging from 2 to 9 hours. We also calculated Krassovsky's parameter and compared with published values.

  20. Secondary gravity waves from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere

    Science.gov (United States)

    Vadas, S.

    2017-12-01

    In this paper, we investigate the generation, propagation and effectsof secondary gravity waves (GWs) from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere in high-resolution GW-resolving models and in TEC/lidar/redline data. We show that secondary GWs generated from the dissipation of orographic GWs at McMurdo Station in Antarctica play a dominant role in the wave activity over McMurdo in the wintertime mesosphere. These secondary GWs are created in the stratosphere, and have been identified in models and data via their telltale "fishbone" appearance in z-t plots. We also show that secondary GWs from the dissipation of GWs excited by deep convectiongenerate concentric rings in the F-region ionosphere. These model results and data point to the importance of secondary GWs from momentumdeposition in the Earth's atmosphere and ionosphere.

  1. Coherent Structure Phenomena in Drift Wave-Zonal Flow Turbulence

    International Nuclear Information System (INIS)

    Smolyakov, A. I.; Diamond, P. H.; Malkov, M.

    2000-01-01

    Zonal flows are azimuthally symmetric plasma potential perturbations spontaneously generated from small-scale drift-wave fluctuations via the action of Reynolds stresses. We show that, after initial linear growth, zonal flows can undergo further nonlinear evolution leading to the formation of long-lived coherent structures which consist of self-bound wave packets supporting stationary shear layers. Such coherent zonal flow structures constitute dynamical paradigms for intermittency in drift-wave turbulence that manifests itself by the intermittent distribution of regions with a reduced level of anomalous transport. (c) 2000 The American Physical Society

  2. Plane waves and structures in turbulent channel flow

    Science.gov (United States)

    Sirovich, L.; Ball, K. S.; Keefe, L. R.

    1990-01-01

    A direct simulation of turbulent flow in a channel is analyzed by the method of empirical eigenfunctions (Karhunen-Loeve procedure, proper orthogonal decomposition). This analysis reveals the presence of propagating plane waves in the turbulent flow. The velocity of propagation is determined by the flow velocity at the location of maximal Reynolds stress. The analysis further suggests that the interaction of these waves appears to be essential to the local production of turbulence via bursting or sweeping events in the turbulent boundary layer, with the additional suggestion that the fast acting plane waves act as triggers.

  3. Imaging the Chicxulub central crater zone from large scale seismic acoustic wave propagation and gravity modeling

    Science.gov (United States)

    Fucugauchi, J. U.; Ortiz-Aleman, C.; Martin, R.

    2017-12-01

    Large complex craters are characterized by central uplifts that represent large-scale differential movement of deep basement from the transient cavity. Here we investigate the central sector of the large multiring Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Despite high contrasts in physical properties,contrasting results for the central uplift have been obtained, with seismic reflection surveys showing lack of resolution in the central zone. We develop an integrated seismic and gravity model for the main structural elements, imaging the central basement uplift and melt and breccia units. The 3-D velocity model built from interpolation of seismic data is validated using perfectly matched layer seismic acoustic wave propagation modeling, optimized at grazing incidence using shift in the frequency domain. Modeling shows significant lack of illumination in the central sector, masking presence of the central uplift. Seismic energy remains trapped in an upper low velocity zone corresponding to the sedimentary infill, melt/breccias and surrounding faulted blocks. After conversion of seismic velocities into a volume of density values, we use massive parallel forward gravity modeling to constrain the size and shape of the central uplift that lies at 4.5 km depth, providing a high-resolution image of crater structure.The Bouguer anomaly and gravity response of modeled units show asymmetries, corresponding to the crater structure and distribution of post-impact carbonates, breccias, melt and target sediments

  4. Gravity waves from the non-renormalizable electroweak vacua phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Greenwood, Eric [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Physics; Vaudrevange, Pascal M. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Physics; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2010-11-15

    It is currently believed that the Standard Model is an effective low energy theory which in principle may contain higher dimensional non-renormalizable operators. These operators may modify the standard model Higgs potential in many ways, one of which being the appearance of a second vacuum. For a wide range of parameters, this new vacuum becomes the true vacuum. It is then assumed that our universe is currently sitting in the false vacuum. Thus the usual second-order electroweak phase transition at early times will be followed by a second, first-order phase transition. In cosmology, a first-order phase transition is associated with the production of gravity waves. In this paper we present an analysis of the production of gravitational waves during such a second electroweak phase transition. We find that, for one certain range of parameters, the stochastic background of gravitational waves generated by bubble nucleation and collision have an amplitude which is estimated to be of order {omega}{sub GW}h{sup 2}{proportional_to}10{sup -11} at f=3 x 10{sup -4} Hz, which is within reach of the planned sensitivity of LISA. For another range of parameters, we find that the amplitude is estimated to be of order {omega}{sub GW}h{sup 2}{proportional_to} 0{sup -25} around f=10{sup 3} Hz, which is within reach of LIGO. Hence, it is possible to detect gravity waves from such a phase transition at two different detectors, with completely different amplitude and frequency ranges. (orig.)

  5. On the Importance of High Frequency Gravity Waves for Ice Nucleation in the Tropical Tropopause Layer

    Science.gov (United States)

    Jensen, Eric J.

    2016-01-01

    Recent investigations of the influence of atmospheric waves on ice nucleation in cirrus have identified a number of key processes and sensitivities: (1) ice concentrations produced by homogeneous freezing are strongly dependent on cooling rates, with gravity waves dominating upper tropospheric cooling rates; (2) rapid cooling driven by high-frequency waves are likely responsible for the rare occurrences of very high ice concentrations in cirrus; (3) sedimentation and entrainment tend to decrease ice concentrations as cirrus age; and (4) in some situations, changes in temperature tendency driven by high-frequency waves can quench ice nucleation events and limit ice concentrations. Here we use parcel-model simulations of ice nucleation driven by long-duration, constant-pressure balloon temperature time series, along with an extensive dataset of cold cirrus microphysical properties from the recent ATTREX high-altitude aircraft campaign, to statistically examine the importance of high-frequency waves as well as the consistency between our theoretical understanding of ice nucleation and observed ice concentrations. The parcel-model simulations indicate common occurrence of peak ice concentrations exceeding several hundred per liter. Sedimentation and entrainment would reduce ice concentrations as clouds age, but 1-D simulations using a wave parameterization (which underestimates rapid cooling events) still produce ice concentrations higher than indicated by observations. We find that quenching of nucleation events by high-frequency waves occurs infrequently and does not prevent occurrences of large ice concentrations in parcel simulations of homogeneous freezing. In fact, the high-frequency variability in the balloon temperature data is entirely responsible for production of these high ice concentrations in the simulations.

  6. Holography as a highly efficient RG flow I: Rephrasing gravity

    OpenAIRE

    Behr, Nicolas; Kuperstein, Stanislav; Mukhopadhyay, Ayan

    2015-01-01

    We investigate how the holographic correspondence can be reformulated as a generalisation of Wilsonian RG flow in a strongly interacting large $N$ quantum field theory. We firstly define a \\textit{highly efficient RG flow} as one in which the Ward identities related to local conservation of energy, momentum and charges preserve the same form at each scale -- to achieve this it is necessary to redefine the background metric and external sources at each scale as functionals of the effective sin...

  7. A Note on Unsteady Temperature Equation For Gravity Flow of A ...

    African Journals Online (AJOL)

    We present an analytical study of unsteady temperature energy equation for gravity of a fluid with non – Newtonian behaviour through a porous medium. For the case of radial axisymmetric flow, the governing partial differential equation is transformed into an ordinary differential equation through similarity variables.

  8. Analysis of the Effect of Electron Density Perturbations Generated by Gravity Waves on HF Communication Links

    Science.gov (United States)

    Fagre, M.; Elias, A. G.; Chum, J.; Cabrera, M. A.

    2017-12-01

    In the present work, ray tracing of high frequency (HF) signals in ionospheric disturbed conditions is analyzed, particularly in the presence of electron density perturbations generated by gravity waves (GWs). The three-dimensional numerical ray tracing code by Jones and Stephenson, based on Hamilton's equations, which is commonly used to study radio propagation through the ionosphere, is used. An electron density perturbation model is implemented to this code based upon the consideration of atmospheric GWs generated at a height of 150 km in the thermosphere and propagating up into the ionosphere. The motion of the neutral gas at these altitudes induces disturbances in the background plasma which affects HF signals propagation. To obtain a realistic model of GWs in order to analyze the propagation and dispersion characteristics, a GW ray tracing method with kinematic viscosity and thermal diffusivity was applied. The IRI-2012, HWM14 and NRLMSISE-00 models were incorporated to assess electron density, wind velocities, neutral temperature and total mass density needed for the ray tracing codes. Preliminary results of gravity wave effects on ground range and reflection height are presented for low-mid latitude ionosphere.

  9. Influences of Gravity Waves on Convectively Induced Turbulence (CIT): A Review

    Science.gov (United States)

    Sharman, Robert D.; Trier, S. B.

    2018-03-01

    Thunderstorms are known to produce turbulence. Such turbulence is commonly referred to as convectively induced turbulence or CIT, and can be hazardous to aviation. Although this turbulence can occur both within and outside the convection, out-of-cloud CIT is particularly hazardous, since it occurs in clear air and cannot be seen by eye or onboard radar. Furthermore, due to its small scale and its ties to the underlying convection, it is very difficult to forecast. Guidelines for out-of-cloud CIT avoidance are available, but they are oversimplified and can be misleading. In the search for more appropriate and physically based avoidance guidelines, considerable research has been conducted in recent years on the nature of the phenomenon, and in particular, its connection to gravity waves generated by the convection. This paper reviews the advances in our understanding of out-of-cloud CIT and its relation to convective gravity waves, and provides several detailed examples of observed cases to elucidate some of the underlying dynamics.

  10. Stability of interfacial waves in two-phase flows

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W S [Ontario Hydro, Toronto, ON (Canada)

    1996-12-31

    The influence of the interfacial pressure and the flow distribution in the one-dimensional two-fluid model on the stability problems of interfacial waves is discussed. With a proper formulation of the interfacial pressure, the following two-phase phenomena can be predicted from the stability and stationary criteria of the interfacial waves: onset of slug flow, stationary hydraulic jump in a stratified flow, flooding in a vertical pipe, and the critical void fraction of a bubbly flow. It can be concluded that the interfacial pressure plays an important role in the interfacial wave propagation of the two-fluid model. The flow distribution parameter may enhance the flow stability range, but only plays a minor role in the two-phase characteristics. (author). 20 refs., 3 tabs., 4 figs.

  11. Directional asymmetry of the nonlinear wave phenomena in a three-dimensional granular phononic crystal under gravity.

    Science.gov (United States)

    Merkel, A; Tournat, V; Gusev, V

    2014-08-01

    We report the experimental observation of the gravity-induced asymmetry for the nonlinear transformation of acoustic waves in a noncohesive granular phononic crystal. Because of the gravity, the contact precompression increases with depth inducing space variations of not only the linear and nonlinear elastic moduli but also of the acoustic wave dissipation. We show experimentally and explain theoretically that, in contrast to symmetric propagation of linear waves, the amplitude of the nonlinearly self-demodulated wave depends on whether the propagation of the waves is in the direction of the gravity or in the opposite direction. Among the observed nonlinear processes, we report frequency mixing of the two transverse-rotational modes belonging to the optical band of vibrations and propagating with negative phase velocities, which results in the excitation of a longitudinal wave belonging to the acoustic band of vibrations and propagating with positive phase velocity. We show that the measurements of the gravity-induced asymmetry in the nonlinear acoustic phenomena can be used to compare the in-depth distributions of the contact nonlinearity and of acoustic absorption.

  12. Three-Dimensional Coupled NLS Equations for Envelope Gravity Solitary Waves in Baroclinic Atmosphere and Modulational Instability

    Directory of Open Access Journals (Sweden)

    Baojun Zhao

    2018-01-01

    Full Text Available Envelope gravity solitary waves are an important research hot spot in the field of solitary wave. And the weakly nonlinear model equations system is a part of the research of envelope gravity solitary waves. Because of the lack of technology and theory, previous studies tried hard to reduce the variable numbers and constructed the two-dimensional model in barotropic atmosphere and could only describe the propagation feature in a direction. But for the propagation of envelope gravity solitary waves in real ocean ridges and atmospheric mountains, the three-dimensional model is more appropriate. Meanwhile, the baroclinic problem of atmosphere is also an inevitable topic. In the paper, the three-dimensional coupled nonlinear Schrödinger (CNLS equations are presented to describe the evolution of envelope gravity solitary waves in baroclinic atmosphere, which are derived from the basic dynamic equations by employing perturbation and multiscale methods. The model overcomes two disadvantages: (1 baroclinic problem and (2 propagation path problem. Then, based on trial function method, we deduce the solution of the CNLS equations. Finally, modulational instability of wave trains is also discussed.

  13. Influence of the inertia and gravity on the boiling flows stability

    International Nuclear Information System (INIS)

    Delmastro, D.F.; Clausse, A.

    1987-01-01

    A study of boiling flows stability on the basis of a linear analysis is presented. From the homogeneous flows' conservation equations, a distributed parameters model, which allows to deal with the frequency field system, is obtained. The adimensional parameters which characterize the inertia effects and the gravity on the impulse equation, are identified. On the other hand, a mean volumes model which permits to gather analytic criteria helpful for the design and comprehension of the problem is developed. (Author)

  14. Long-term Global Morphology of Gravity Wave Activity Using UARS Data

    Science.gov (United States)

    Eckermann, Stephen D.; Jackman, C. (Technical Monitor)

    2000-01-01

    This quarter was largely devoted to a detailed study of temperature data acquired by the Cryogenic Limb Array Etalon Spectrometer (CLAES) on UARS. Our analysis used the same sequence of methods that have been developed, tested and refined on a more limited subset of temperature data acquired by the CRISTA instrument. We focused on a limited subset of our reasoning that geographical and vertical trends in the small-scale temperature variability could be compared with similar trends observed in November 1994 by the CRISTA-SPAS satellite. Results, backed up with hindcasts from the Mountain Wave Forecast Model (MWFM), reveal strong evidence of mountain waves, most persuasively in the Himalayas on 16-17 November, 1992. These CLAES results are coherent over the 30-50 km range and compare well with MWFM hindcasts for the same period. This constitutes, we believe, the first clear evidence that CLAES explicitly resolved long wavelength gravity waves in its CO2 temperature channel. A series of other tasks, related to mesoscale modeling of mountain waves in CRISTA data and fitting of ground-based and HRDI data on global scales, were seen through to publication stage in peer-reviewed journals.

  15. Magnetoelastic shear wave propagation in pre-stressed anisotropic media under gravity

    Science.gov (United States)

    Kumari, Nirmala; Chattopadhyay, Amares; Singh, Abhishek K.; Sahu, Sanjeev A.

    2017-03-01

    The present study investigates the propagation of shear wave (horizontally polarized) in two initially stressed heterogeneous anisotropic (magnetoelastic transversely isotropic) layers in the crust overlying a transversely isotropic gravitating semi-infinite medium. Heterogeneities in both the anisotropic layers are caused due to exponential variation (case-I) and linear variation (case-II) in the elastic constants with respect to the space variable pointing positively downwards. The dispersion relations have been established in closed form using Whittaker's asymptotic expansion and were found to be in the well-agreement to the classical Love wave equations. The substantial effects of magnetoelastic coupling parameters, heterogeneity parameters, horizontal compressive initial stresses, Biot's gravity parameter, and wave number on the phase velocity of shear waves have been computed and depicted by means of a graph. As a special case, dispersion equations have been deduced when the two layers and half-space are isotropic and homogeneous. The comparative study for both cases of heterogeneity of the layers has been performed and also depicted by means of graphical illustrations.

  16. Alfven wave resonances and flow induced by nonlinear Alfven waves in a stratified atmosphere

    International Nuclear Information System (INIS)

    Stark, B. A.; Musielak, Z. E.; Suess, S. T.

    1996-01-01

    A nonlinear, time-dependent, ideal MHD code has been developed and used to compute the flow induced by nonlinear Alfven waves propagating in an isothermal, stratified, plane-parallel atmosphere. The code is based on characteristic equations solved in a Lagrangian frame. Results show that resonance behavior of Alfven waves exists in the presence of a continuous density gradient and that the waves with periods corresponding to resonant peaks exert considerably more force on the medium than off-resonance periods. If only off-peak periods are considered, the relationship between the wave period and induced longitudinal velocity shows that short period WKB waves push more on the background medium than longer period, non-WKB, waves. The results also show the development of the longitudinal waves induced by finite amplitude Alfven waves. Wave energy transferred to the longitudinal mode may provide a source of localized heating

  17. Properties of flooding waves in vertical churn flow

    International Nuclear Information System (INIS)

    Wang, K.; Bai, B.; Yang, B.; Xie, C.

    2011-01-01

    It is more accurate to predict the critical heat flux (CHF) from the start of churn flow rather than the start of annular flow. High-speed photography has been employed for qualitative investigation of entrainment in vertical two-phase flow under churn flow condition. This paper mainly focuses on the evolution of the flooding waves close to the water inlet section and liquid distribution in the cross-section of tube. The properties of flooding wave such as frequency and amplitude have been obtained. (author)

  18. Constraints on Born-Infeld gravity from the speed of gravitational waves after GW170817 and GRB 170817A

    Science.gov (United States)

    Jana, Soumya; Chakravarty, Girish Kumar; Mohanty, Subhendra

    2018-04-01

    The observations of gravitational waves from the binary neutron star merger event GW170817 and the subsequent observation of its electromagnetic counterparts from the gamma-ray burst GRB 170817A provide us a significant opportunity to study theories of gravity beyond general relativity. An important outcome of these observations is that they constrain the difference between the speed of gravity and the speed of light to less than 10-15c . Also, the time delay between the arrivals of gravitational waves at different detectors constrains the speed of gravity at the Earth to be in the range 0.55 c gravity: Eddington-inspired Born-Infeld (EiBI) gravity. We show that, in EiBI theory, the speed of gravitational waves in matter deviates from c . From the time delay in the arrival of gravitational wave signals at Earth-based detectors, we obtain the bound on the theory parameter κ as |κ |≲1021 m2 . Similarly, from the time delay between the signals of GW170817 and GRB 170817A, in a background Friedmann-Robertson-Walker universe, we obtain |κ |≲1037 m2 . Although the bounds on κ are weak compared to other earlier bounds from the study of neutron stars, stellar evolution, primordial nucleosynthesis, etc., our bounds are from direct observations and thus worth noting.

  19. Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow

    Science.gov (United States)

    Tsvelodub, O. Yu; Bocharov, A. A.

    2017-09-01

    The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. The paper studies nonlinear waves on a liquid film, flowing under the action of gravity in a known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. The periodic and soliton steady-state traveling solutions of this equation have been numerically found. The analysis of branching of new families of steady-state traveling solutions has been performed. In particular, it is shown that this model equation has solutions in the form of solitons-humps.

  20. The Two-Phase Flow Separator Experiment Breadboard Model: Reduced Gravity Aircraft Results

    Science.gov (United States)

    Rame, E; Sharp, L. M.; Chahine, G.; Kamotani, Y.; Gotti, D.; Owens, J.; Gilkey, K.; Pham, N.

    2015-01-01

    Life support systems in space depend on the ability to effectively separate gas from liquid. Passive cyclonic phase separators use the centripetal acceleration of a rotating gas-liquid mixture to carry out phase separation. The gas migrates to the center, while gas-free liquid may be withdrawn from one of the end plates. We have designed, constructed and tested a breadboard that accommodates the test sections of two independent principal investigators and satisfies their respective requirements, including flow rates, pressure and video diagnostics. The breadboard was flown in the NASA low-gravity airplane in order to test the system performance and design under reduced gravity conditions.

  1. Properties of internal planetary-scale inertio gravity waves in the mesosphere

    Directory of Open Access Journals (Sweden)

    H. G. Mayr

    2004-11-01

    Full Text Available At high latitudes in the upper mesosphere, horizontal wind oscillations have been observed with periods around 10h. Waves with such a period are generated in our Numerical Spectral Model (NSM, and they are identified as planetary-scale inertio gravity waves (IGW. These IGWs have periods between 9 and 11h and appear above 60km in the zonal mean (m=0, as well as in m=1 to 4, propagating eastward and westward. Under the influence of the Coriolis force, the amplitudes of the waves propagating westward are larger at high latitudes than those propagating eastward. The waves grow in magnitude at least up to about 100km and have vertical wavelengths around 25km. Applying a running window of 15 days for spectral analysis, the amplitudes in the wind field are typically between 10 and 20m/s and can reach 30m/s in the westward propagating component for m=1 at the poles. In the temperature perturbations, the wave amplitudes above 100km are typically 5K and as large as 10K for m=0 at the poles. The IGWs are intermittent but reveal systematic seasonal variations, with the largest amplitudes occurring generally in late winter and spring. Numerical experiments show that such waves are also generated without excitation of the migrating tides. The amplitudes and periods then are similar, indicating that the tides are not essential to generate the waves. However, the seasonal variations without tides are significantly different, which leads to the conclusion that non linear interactions between the semidiurnal tide and planetary waves must contribute to the excitation of the IGWs. Directly or indirectly through the planetary waves, the IGWs are apparently excited by the instabilities that arise in the zonal mean circulation. When the solar heating is turned off for m=0, both the PWs and IGWs essentially disappear. That the IGWs and PWs have common roots in their excitation mechanism is also indicated by the striking similarity of their seasonal variations in the

  2. Frozen-wave instability in near-critical hydrogen subjected to horizontal vibration under various gravity fields.

    Science.gov (United States)

    Gandikota, G; Chatain, D; Amiroudine, S; Lyubimova, T; Beysens, D

    2014-01-01

    The frozen-wave instability which appears at a liquid-vapor interface when a harmonic vibration is applied in a direction tangential to it has been less studied until now. The present paper reports experiments on hydrogen (H2) in order to study this instability when the temperature is varied near its critical point for various gravity levels. Close to the critical point, a liquid-vapor density difference and surface tension can be continuously varied with temperature in a scaled, universal way. The effect of gravity on the height of the frozen waves at the interface is studied by performing the experiments in a magnetic facility where effective gravity that results from the coupling of the Earth's gravity and magnetic forces can be varied. The stability diagram of the instability is obtained. The experiments show a good agreement with an inviscid model [Fluid Dyn. 21 849 (1987)], irrespective of the gravity level. It is observed in the experiments that the height of the frozen waves varies weakly with temperature and increases with a decrease in the gravity level, according to a power law with an exponent of 0.7. It is concluded that the wave height becomes of the order of the cell size as the gravity level is asymptotically decreased to zero. The interface pattern thus appears as a bandlike pattern of alternate liquid and vapor phases, a puzzling phenomenon that was observed with CO2 and H2 near their critical point in weightlessness [Acta Astron. 61 1002 (2007); Europhys. Lett. 86 16003 (2009)].

  3. The effect of breaking gravity waves on the dynamics and chemistry of the mesosphere and lower thermosphere (invited review)

    Science.gov (United States)

    Garcia, R. R.

    1986-01-01

    The influence of breaking gravity waves on the dynamics and chemical composition of the 60 to 110 km region is investigated with a two dimensional model that includes a parameterization of gravity wave momentum deposition and diffusion. The dynamical model is described by Garcia and Solomon (1983) and Solomon and Garcia (1983) and includes a complete chemical scheme for the mesosphere and lower thermosphere. The parameterization of Lindzen (1981) is used to calculate the momentum deposited and the turbulent diffusion produced by the gravity waves. It is found that wave momentum deposition drives a very vigorous mean meridional circulation, produces a very cold summer mesopause and reverse the zonal wind jets above about 85 km. The seasonal variation of the turbulent diffusion coefficient is consistent with the behavior of mesospheric turbulences inferred from MST radar echoes. The large degree of consistency between model results and various types of dynamical and chemical data supports very strongly the hypothesis that breaking gravity waves play a major role in determining the zonally-averaged dynamical and chemical structure of the 60 to 110 km region of the atmosphere.

  4. Low energy consumption vortex wave flow membrane bioreactor.

    Science.gov (United States)

    Wang, Zhiqiang; Dong, Weilong; Hu, Xiaohong; Sun, Tianyu; Wang, Tao; Sun, Youshan

    2017-11-01

    In order to reduce the energy consumption and membrane fouling of the conventional membrane bioreactor (MBR), a kind of low energy consumption vortex wave flow MBR was exploited based on the combination of biofilm process and membrane filtration process, as well as the vortex wave flow technique. The experimental results showed that the vortex wave flow state in the membrane module could be formed when the Reynolds number (Re) of liquid was adjusted between 450 and 1,050, and the membrane flux declined more slowly in the vortex wave flow state than those in the laminar flow state and turbulent flow state. The MBR system was used to treat domestic wastewater under the condition of vortex wave flow state for 30 days. The results showed that the removal efficiency for CODcr and NH 3 -N was 82% and 98% respectively, and the permeate quality met the requirement of 'Water quality standard for urban miscellaneous water consumption (GB/T 18920-2002)'. Analysis of the energy consumption of the MBR showed that the average energy consumption was 1.90 ± 0.55 kWh/m 3 (permeate), which was only two thirds of conventional MBR energy consumption.

  5. Crustal and Upper Mantle Structure from Joint Inversion of Body Wave and Gravity Data

    Science.gov (United States)

    2012-09-01

    We use both free-air and Bouguer gravity anomalies derived from the global gravity model of the GRACE satellite mission. The gravity data provide...relocation analysis. We use both free-air and Bouguer gravity anomalies derived from the global gravity model of the GRACE satellite mission. The gravity...topographic relief this effect needs to be removed; thus, we converted free-air anomalies into Bouguer anomalies assuming a standard density for crustal rocks

  6. Numerical simulation of convective generated gravity waves in the stratosphere and MLT regions.

    Science.gov (United States)

    Heale, C. J.; Snively, J. B.

    2017-12-01

    Convection is an important source of gravity wave generation, especially in the summer tropics and midlatitudes, and coherent wave fields above convection are now routinely measured in the stratosphere and mesosphere [e.g. Hoffmann et al., JGR, 118, 2013; Gong et al., JGR, 120, 2015; Perwitasari et al., GRL, 42, 22, 2016]. Numerical studies have been performed to investigate the generation mechanisms, source spectra, and their effects on the middle and upper atmosphere [e.g. Fovell et al., AMS, 49,16, 1992; Alexander and Holton, Atmos. Chem. Phys., 4 2004; Vincent et al., JGR, 1118, 2013], however there is still considerable work needed to fully describe these parameters. GCMs currently lack the resolution to explicitly simulate convection generation and rely on simplified parameterizations while full cloud resolving models are computationally expensive and often only extend into the stratosphere. More recent studies have improved the realism of these simulations by using radar derived precipitation rates to drive latent heating in models that simulate convection [Grimsdell et al., AMS, 67, 2010; Stephan and Alexander., J. Adv. Model. Earth. Syst, 7, 2015], however they too only consider wave propagation in the troposphere and stratosphere. We use a 2D nonlinear, fully compressible model [Snively and Pasko., JGR, 113, 2008] to excite convectively generated waves, based on NEXRAD radar data, using the Stephan and Alexander [2015] algorithms. We study the propagation, and spectral evolution of the generated waves up into the MLT region. Ambient atmosphere parameters are derived from observations and MERRA-2 reanalysis data, and stratospheric (AIRS) and mesospheric (Lidar, OH airglow) observations enable comparisons with simulation results.

  7. Gravity wave and neutrino bursts from stellar collapse: A sensitive test of neutrino masses

    International Nuclear Information System (INIS)

    Arnaud, N.; Barsuglia, M.; Bizouard, M.A.; Cavalier, F.; Davier, M.; Hello, P.; Pradier, T.

    2002-01-01

    New methods are proposed with the goal to determine absolute neutrino masses from the simultaneous observation of the bursts of neutrinos and gravitational waves emitted during a stellar collapse. It is shown that the neutronization electron neutrino flash and the maximum amplitude of the gravitational wave signal are tightly synchronized with the bounce occurring at the end of the core collapse on a time scale better than 1 ms. The existing underground neutrino detectors (SuperKamiokande, SNO,...) and the gravity wave antennas soon to operate (LIGO, VIRGO,...) are well matched in their performance for detecting galactic supernovae and for making use of the proposed approach. Several methods are described, which apply to the different scenarios depending on neutrino mixing. Given the present knowledge on neutrino oscillations, the methods proposed are sensitive to a mass range where neutrinos would essentially be mass degenerate. The 95% C.L. upper limit which can be achieved varies from 0.75 eV/c 2 for large ν e survival probabilities to 1.1 eV/c 2 when in practice all ν e 's convert into ν μ 's or ν τ 's. The sensitivity is nearly independent of the supernova distance

  8. Development of Flow Boiling and Condensation Experiment on the International Space Station- Normal and Low Gravity Flow Boiling Experiment Development and Test Results

    Science.gov (United States)

    Nahra, Henry K.; Hall, Nancy R.; Hasan, Mohammad M.; Wagner, James D.; May, Rochelle L.; Mackey, Jeffrey R.; Kolacz, John S.; Butcher, Robert L.; Frankenfield, Bruce J.; Mudawar, Issam; hide

    2013-01-01

    Flow boiling and condensation have been identified as two key mechanisms for heat transport that are vital for achieving weight and volume reduction as well as performance enhancement in future space systems. Since inertia driven flows are demanding on power usage, lower flows are desirable. However, in microgravity, lower flows are dominated by forces other than inertia (like the capillary force). It is of paramount interest to investigate limits of low flows beyond which the flow is inertial enough to be gravity independent. One of the objectives of the Flow Boiling and Condensation Flight Experiment sets to investigate these limits for flow boiling and condensation. A two-phase flow loop consisting of a Flow Boiling Module and two Condensation Modules has been developed to experimentally study flow boiling condensation heat transfer in the reduced gravity environment provided by the reduced gravity platform. This effort supports the development of a flow boiling and condensation facility for the International Space Station (ISS). The closed loop test facility is designed to deliver the test fluid, FC-72 to the inlet of any one of the test modules at specified thermodynamic and flow conditions. The zero-g-aircraft tests will provide subcooled and saturated flow boiling critical heat flux and flow condensation heat transfer data over wide range of flow velocities. Additionally, these tests will verify the performance of all gravity sensitive components, such as evaporator, condenser and accumulator associated with the two-phase flow loop. We will present in this paper the breadboard development and testing results which consist of detailed performance evaluation of the heater and condenser combination in reduced and normal gravity. We will also present the design of the reduced gravity aircraft rack and the results of the ground flow boiling heat transfer testing performed with the Flow Boiling Module that is designed to investigate flow boiling heat transfer and

  9. Free surface flow under gravity and surface tension due to an applied pressure distribution: i Bond number greater than one-third

    Energy Technology Data Exchange (ETDEWEB)

    Maleewong, Montri; Asavanant, Jack [Chulalongkorn University, Department of Mathematics and Advanced Virtual Intelligence Computing Center, Bangkok (Thailand); Grimshaw, Roger [Loughborough University, Department of Mathematical Sciences, Loughborough (United Kingdom)

    2005-08-01

    We consider steady free surface two-dimensional flow due to a localized applied pressure distribution under the effects of both gravity and surface tension in water of constant depth, and in the presence of a uniform stream. The fluid is assumed to be inviscid and incompressible, and the flow is irrotational. The behavior of the forced nonlinear waves is characterized by three parameters: the Froude number, F, the Bond number, {tau}>1/3, and the magnitude and sign of the pressure forcing parameter {epsilon}. The fully nonlinear wave problem is solved numerically by using a boundary integral method. For small amplitude waves and F<1 but not too close to 1, linear theory gives a good prediction for the numerical solution of the nonlinear problem in the case of bifurcation from the uniform flow. As F approaches 1, the nonlinear terms need to be taken account of. In this case the forced Korteweg-de Vries equation is found to be an appropriate model to describe bifurcations from an unforced solitary wave. In general, it is found that for given values of F<1 and {tau}>1/3, there exists both elevation and depression waves. In some cases, a limiting configuration in the form of a trapped bubble occurs in the depression wave solutions. (orig.)

  10. Simulation of flooding waves in vertical churn flow

    Energy Technology Data Exchange (ETDEWEB)

    Tekavčič, Matej, E-mail: matej.tekavcic@ijs.si; Končar, Boštjan; Kljenak, Ivo

    2016-04-01

    Highlights: • Flooding waves in air–water churn flow in a vertical pipe were studied. • Simulations using two-fluid model with interface sharpening were performed. • Calculated wave amplitudes agree with existing experimental data. • Contributions of force terms in the liquid momentum balance equation are presented. - Abstract: A transient simulation of flooding waves in the churn flow of air and water in a vertical pipe is performed by the means of two-fluid modelling approach with interface sharpening. The gas and liquid phases are considered immiscible and incompressible with no mass transfer between them. Inter-phase coupling of momentum is realized via interface drag force which is based on the interface area density and the relative velocity between the phases. Surface tension effects are modelled with the Continuum Surface Model. The flow is assumed isothermal. Turbulence is modelled for each phase separately using the two-equation eddy viscosity approach. Results are compared with the reported experimental data for churn flow regime in a vertical pipe (Wang et al., 2011a). Reynolds numbers of the gas flow are in the range from 6000 to 10,000, while the liquid mass flow rate upwards ranges from 25 to 32 g/s. Prediction of critical and maximum amplitudes of the flooding waves show good agreement with experimental values. Results for wave frequencies indicate significant deviations, which can be attributed to the choice of the liquid inlet model.

  11. Simulation of flooding waves in vertical churn flow

    International Nuclear Information System (INIS)

    Tekavčič, Matej; Končar, Boštjan; Kljenak, Ivo

    2016-01-01

    Highlights: • Flooding waves in air–water churn flow in a vertical pipe were studied. • Simulations using two-fluid model with interface sharpening were performed. • Calculated wave amplitudes agree with existing experimental data. • Contributions of force terms in the liquid momentum balance equation are presented. - Abstract: A transient simulation of flooding waves in the churn flow of air and water in a vertical pipe is performed by the means of two-fluid modelling approach with interface sharpening. The gas and liquid phases are considered immiscible and incompressible with no mass transfer between them. Inter-phase coupling of momentum is realized via interface drag force which is based on the interface area density and the relative velocity between the phases. Surface tension effects are modelled with the Continuum Surface Model. The flow is assumed isothermal. Turbulence is modelled for each phase separately using the two-equation eddy viscosity approach. Results are compared with the reported experimental data for churn flow regime in a vertical pipe (Wang et al., 2011a). Reynolds numbers of the gas flow are in the range from 6000 to 10,000, while the liquid mass flow rate upwards ranges from 25 to 32 g/s. Prediction of critical and maximum amplitudes of the flooding waves show good agreement with experimental values. Results for wave frequencies indicate significant deviations, which can be attributed to the choice of the liquid inlet model.

  12. Solitary impulse wave run-up and overland flow

    International Nuclear Information System (INIS)

    Fuchs, H.

    2013-04-01

    Impulse waves are generated by landslides, rockfalls or avalanches impacting a reservoir or natural lake. These long waves generated by the impulse transferred to the water body in combination with the usually short propagation distance within a lake lead to a large damage potential due to wave run-up or dam overtopping. Damages are then caused by (1) direct wave load on structures, (2) driftwood and float impact and (3) their deposits after water retreat. Major historic events occurred at Lituya Bay, Alaska, in 1958, or at the Vaiont Reservoir, Italy, in 1963. Recent events were observed at Lake Chehalis, Canada, or Lake Lucerne, Switzerland, both in 2007, or at the Lower Grindelwald proglacial lake, Switzerland, in 2009. Whereas previous VAW research aimed at the generation phase of landslide-generated impulse waves with a special focus on the wave characteristics, the current research concentrates on the opposite wave-shore interaction. A particular focus is given to the transition point from the shore slope to the horizontal plane where the orbital wave motion is transformed into a shore-parallel flow. As most literature relates only to plain wave run-up on a linearly-inclined plane and the few studies focussing on wave-induced overland flow are case studies considering only a specific bathymetry, currently no general conclusions on wave-induced overland flow can be drawn. The present study therefore intends to fill in this gap by physical modeling. Testing involved a new test-setup including a piston-type wave maker to generate solitary waves, and a smooth impermeable PVC shore of height w = 0.25 m with a connected horizontal overland flow portion. By varying the shore slope tanβ = 1/1.5, 1/2.5 and 1/5.0, the still water depth h = 0.16 - 0.24 m, and the relative wave height H/h = 0.1 -0.7, a wide range of basic parameters was covered. Overland flow depths and front velocities were measured along the shore using Ultrasonic Distance Sensors. Further, flow

  13. Solitary impulse wave run-up and overland flow

    Energy Technology Data Exchange (ETDEWEB)

    Fuchs, H.

    2013-04-15

    Impulse waves are generated by landslides, rockfalls or avalanches impacting a reservoir or natural lake. These long waves generated by the impulse transferred to the water body in combination with the usually short propagation distance within a lake lead to a large damage potential due to wave run-up or dam overtopping. Damages are then caused by (1) direct wave load on structures, (2) driftwood and float impact and (3) their deposits after water retreat. Major historic events occurred at Lituya Bay, Alaska, in 1958, or at the Vaiont Reservoir, Italy, in 1963. Recent events were observed at Lake Chehalis, Canada, or Lake Lucerne, Switzerland, both in 2007, or at the Lower Grindelwald proglacial lake, Switzerland, in 2009. Whereas previous VAW research aimed at the generation phase of landslide-generated impulse waves with a special focus on the wave characteristics, the current research concentrates on the opposite wave-shore interaction. A particular focus is given to the transition point from the shore slope to the horizontal plane where the orbital wave motion is transformed into a shore-parallel flow. As most literature relates only to plain wave run-up on a linearly-inclined plane and the few studies focussing on wave-induced overland flow are case studies considering only a specific bathymetry, currently no general conclusions on wave-induced overland flow can be drawn. The present study therefore intends to fill in this gap by physical modeling. Testing involved a new test-setup including a piston-type wave maker to generate solitary waves, and a smooth impermeable PVC shore of height w = 0.25 m with a connected horizontal overland flow portion. By varying the shore slope tanβ = 1/1.5, 1/2.5 and 1/5.0, the still water depth h = 0.16 - 0.24 m, and the relative wave height H/h = 0.1 -0.7, a wide range of basic parameters was covered. Overland flow depths and front velocities were measured along the shore using Ultrasonic Distance Sensors. Further, flow

  14. Satellite traces, range spread-F occurrence, and gravity wave propagation at the southern anomaly crest

    Energy Technology Data Exchange (ETDEWEB)

    Cabrera, M.A. [Universidad Tecnologica Nacional, Tucuman (Argentina). CIASUR, Facultad Regional Tucuman; Universidad Nacional de Tucuman (Argentina). Lab. de Ionosfera; Pezzopane, M.; Zuccheretti, E. [Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy); Ezquer, R.G. [Universidad Tecnologica Nacional, Tucuman (Argentina). CIASUR, Facultad Regional Tucuman; Universidad Nacional de Tucuman (Argentina). Lab. de Ionosfera; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Buenos Aires (Argentina)

    2010-07-01

    Range spread-F (RSF) and occurrence of ''satellite'' traces prior to RSF onset were studied at the southern peak of the ionospheric equatorial anomaly (EA). Ionograms recorded in September 2007 at the new ionospheric station of Tucuman, Argentina (26.9 S, 294.6 E, dip latitude 15.5 S), by the Advanced Ionospheric Sounder (AIS) developed at the Istituto Nazionale di Geofisica e Vulcanologia (INGV), were considered. Satellite traces (STs) are confirmed to be a necessary precursor to the appearance of an RSF trace on the ionograms. Moreover, an analysis of isoheight contours of electron density seems to suggest a relationship between RSF occurrence and gravity wave (GW) propagation. (orig.)

  15. Gauge/gravity duality for interactions of spherical membranes in 11-dimensional pp-wave

    International Nuclear Information System (INIS)

    Lee, Hok Kong; McLoughlin, Tristan; Wu Xinkai

    2005-01-01

    We investigate the gauge/gravity duality in the interaction between two spherical membranes in the 11-dimensional pp-wave background. On the supergravity side, we find the solution to the field equations at locations close to a spherical source membrane, and use it to obtain the light-cone Lagrangian of a spherical probe membrane very close to the source, i.e., with their separation much smaller than their radii. On the gauge theory side, using the BMN matrix model, we compute the one-loop effective potential between two membrane fuzzy spheres. Perfect agreement is found between the two sides. Moreover, the one-loop effective potential we obtain on the gauge theory side is valid beyond the small-separation approximation, giving the full interpolation between interactions of membrane-like objects and that of graviton-like objects

  16. Diffusion and mixing in gravity-driven dense granular flows.

    Science.gov (United States)

    Choi, Jaehyuk; Kudrolli, Arshad; Rosales, Rodolfo R; Bazant, Martin Z

    2004-04-30

    We study the transport properties of particles draining from a silo using imaging and direct particle tracking. The particle displacements show a universal transition from superdiffusion to normal diffusion, as a function of the distance fallen, independent of the flow speed. In the superdiffusive (but sub-ballistic) regime, which occurs before a particle falls through its diameter, the displacements have fat-tailed and anisotropic distributions. In the diffusive regime, we observe very slow cage breaking and Péclet numbers of order 100, contrary to the only previous microscopic model (based on diffusing voids). Overall, our experiments show that diffusion and mixing are dominated by geometry, consistent with long-lasting contacts but not thermal collisions, as in normal fluids.

  17. Averaging processes in granular flows driven by gravity

    Science.gov (United States)

    Rossi, Giulia; Armanini, Aronne

    2016-04-01

    One of the more promising theoretical frames to analyse the two-phase granular flows is offered by the similarity of their rheology with the kinetic theory of gases [1]. Granular flows can be considered a macroscopic equivalent of the molecular case: the collisions among molecules are compared to the collisions among grains at a macroscopic scale [2,3]. However there are important statistical differences in dealing with the two applications. In the two-phase fluid mechanics, there are two main types of average: the phasic average and the mass weighed average [4]. The kinetic theories assume that the size of atoms is so small, that the number of molecules in a control volume is infinite. With this assumption, the concentration (number of particles n) doesn't change during the averaging process and the two definitions of average coincide. This hypothesis is no more true in granular flows: contrary to gases, the dimension of a single particle becomes comparable to that of the control volume. For this reason, in a single realization the number of grain is constant and the two averages coincide; on the contrary, for more than one realization, n is no more constant and the two types of average lead to different results. Therefore, the ensamble average used in the standard kinetic theory (which usually is the phasic average) is suitable for the single realization, but not for several realization, as already pointed out in [5,6]. In the literature, three main length scales have been identified [7]: the smallest is the particles size, the intermediate consists in the local averaging (in order to describe some instability phenomena or secondary circulation) and the largest arises from phenomena such as large eddies in turbulence. Our aim is to solve the intermediate scale, by applying the mass weighted average, when dealing with more than one realizations. This statistical approach leads to additional diffusive terms in the continuity equation: starting from experimental

  18. Intermittency of gravity wave momentum flux in the mesopause region observed with an all-sky airglow imager

    Science.gov (United States)

    Cao, Bing; Liu, Alan Z.

    2016-01-01

    The intermittency of gravity wave momentum flux (MF) near the OH airglow layer (˜87 km) in the mesopause region is investigated for the first time using observation of all-sky airglow imager over Maui, Hawaii (20.7°N, 156.3°W), and Cerro Pachón, Chile (30.3°S, 70.7°W). At both sites, the probability density function (pdf) of gravity wave MF shows two distinct distributions depending on the magnitude of the MF. For MF smaller (larger) than ˜16 m2 s-2 (0.091 mPa), the pdf follows a lognormal (power law) distribution. The intermittency represented by the Bernoulli proxy and the percentile ratio shows that gravity waves have higher intermittency at Maui than at Cerro Pachón, suggesting more intermittent background variation above Maui. It is found that most of the MF is contributed by waves that occur very infrequently. But waves that individually contribute little MF are also important because of their higher occurrence frequencies. The peak contribution is from waves with MF around ˜2.2 m2 s-2 at Cerro Pachón and ˜5.5 m2 s-2 at Maui. Seasonal variations of the pdf and intermittency imply that the background atmosphere has larger influence on the observed intermittency in the mesopause region.

  19. Some Expressions for Gravity without the Big G and their Possible Wave-Theoretical-Explanation

    Directory of Open Access Journals (Sweden)

    Tank H. K.

    2013-01-01

    Full Text Available This letter presents some new expressions for gravity without the big G and proposes their possible wave-theoretical-explanation. This attempt leads to some insight that: (i We need the proportionality-constant G because we measure masses and distances in our arbitrarily-chosen units of kg and meters; but if we measure “mass” as a fraction of “total-mass of the universe” M 0 and measure distances as a fraction of “radius-of-the- universe” R 0 then there is no need for the proportionality-constant G . However, large uncertainties in the M 0 and R 0 limit the general application of this relation presently. (ii The strength of gravity would be different if the total-mass of the universe were different. Then this possibility is supported with the help of wave-theory. (iii This understanding of G leads to an insight that Plancks-length, Planck-mass and Planck’s unit of time are geometric-mean-values of astrophysical quantities like: total-mass of the universe and the smallest-possible-mass hH 0 = c 2 . (iv There appears a law followed by various systems-of-matter, like: the electron, the proton, the nucleus-of-atom, the globular-clusters, the spiral-galaxies, the galactic-clusters and the whole universe; that their ratio Mass / Radius 2 remains constant. This law seems to be more fundamental than the fundamental-forces because it is obeyed irrespective of the case, whether the system is bound by strong-force, electric-force, or gravitational-force.

  20. Gravity Waves in the Martian Atmosphere detected by the Radio Science Experiment MaRS on Mars Express

    Science.gov (United States)

    Tellmann, S.; Pätzold, M.; Häusler, B.; Tyler, G. L.; Hinson, D. P.

    2013-09-01

    Gravity waves are an ubiquitous feature in all stably stratified planetary atmospheres. They are known to play a significant role in the energy and momentum budget of the Earth, and they are assumed to be of importance for the redistribution of energy and momentum throughout the Martian atmosphere.

  1. Influence of vertically and obliquely propagating gravity waves on the polar summer mesosphere

    Science.gov (United States)

    Thurairajah, B.; Siskind, D. E.; Bailey, S. M.

    2017-12-01

    Polar Mesospheric Clouds (PMCs) are sensitive to changes in temperature of the cold polar summer mesosphere, which in turn are modulated by gravity waves (GWs). In this study we investigate the link between PMCs and GWs that propagate both vertically (i.e. wave propagation is directly above the source region) and obliquely (lateral or non-vertical propagation upward but away from the source region). Several observational studies have analyzed the link between PMCs and vertically propagating GWs and have reported both positive and negative correlations. Moreover, while modelling studies have noted the possibility of oblique propagation of GWs from the low-latitude stratosphere to the high-latitude mesosphere, observational studies of the influence of these waves on the polar summer mesosphere are sparse. We present a comprehensive analysis of the influence of vertically and obliquely propagating GWs on the northern hemisphere (NH) polar summer mesosphere using data from 8 PMC seasons. Temperature data from the SOFIE experiment on the AIM satellite and SABER instrument on the TIMED satellite are used to derive GW parameters. SOFIE PMC data in terms of Ice Water Content (IWC) are used to quantify the changes in the polar summer mesosphere. At high latitudes, preliminary analysis of vertically propagating waves indicate a weak but positive correlation between GWs at 50 km and GWs at the PMC altitude of 84 km. Overall there is a negative correlation between GWs at 50 km and IWC and a positive correlation between GWs at 84 km and IWC. These results and the presence of a slanted structure (slanted from the low-latitude stratosphere to the high-latitude mesosphere) in GW momentum flux suggest the possibility of a significant influence of obliquely propagating GWs on the polar summer mesosphere

  2. Integrating Unified Gravity Wave Physics into the NOAA Next Generation Global Prediction System

    Science.gov (United States)

    Alpert, J. C.; Yudin, V.; Fuller-Rowell, T. J.; Akmaev, R. A.

    2017-12-01

    The Unified Gravity Wave Physics (UGWP) project for the Next Generation Global Prediction System (NGGPS) is a NOAA collaborative effort between the National Centers for Environmental Prediction (NCEP), Environemntal Modeling Center (EMC) and the University of Colorado, Cooperative Institute for Research in Environmental Sciences (CU-CIRES) to support upgrades and improvements of GW dynamics (resolved scales) and physics (sub-grid scales) in the NOAA Environmental Modeling System (NEMS)†. As envisioned the global climate, weather and space weather models of NEMS will substantially improve their predictions and forecasts with the resolution-sensitive (scale-aware) formulations planned under the UGWP framework for both orographic and non-stationary waves. In particular, the planned improvements for the Global Forecast System (GFS) model of NEMS are: calibration of model physics for higher vertical and horizontal resolution and an extended vertical range of simulations, upgrades to GW schemes, including the turbulent heating and eddy mixing due to wave dissipation and breaking, and representation of the internally-generated QBO. The main priority of the UGWP project is unified parameterization of orographic and non-orographic GW effects including momentum deposition in the middle atmosphere and turbulent heating and eddies due to wave dissipation and breaking. The latter effects are not currently represented in NOAA atmosphere models. The team has tested and evaluated four candidate GW solvers integrating the selected GW schemes into the NGGPS model. Our current work and planned activity is to implement the UGWP schemes in the first available GFS/FV3 (open FV3) configuration including adapted GFDL modification for sub-grid orography in GFS. Initial global model results will be shown for the operational and research GFS configuration for spectral and FV3 dynamical cores. †http://www.emc.ncep.noaa.gov/index.php?branch=NEMS

  3. Rarefaction wave in relativistic steady magnetohydrodynamic flows

    Energy Technology Data Exchange (ETDEWEB)

    Sapountzis, Konstantinos, E-mail: ksapountzis@phys.uoa.gr; Vlahakis, Nektarios, E-mail: vlahakis@phys.uoa.gr [Faculty of Physics, University of Athens, 15784 Zografos, Athens (Greece)

    2014-07-15

    We construct and analyze a model of the relativistic steady-state magnetohydrodynamic rarefaction that is induced when a planar symmetric flow (with one ignorable Cartesian coordinate) propagates under a steep drop of the external pressure profile. Using the method of self-similarity, we derive a system of ordinary differential equations that describe the flow dynamics. In the specific limit of an initially homogeneous flow, we also provide analytical results and accurate scaling laws. We consider that limit as a generalization of the previous Newtonian and hydrodynamic solutions already present in the literature. The model includes magnetic field and bulk flow speed having all components, whose role is explored with a parametric study.

  4. Development of the Two Phase Flow Separator Experiment for a Reduced Gravity Aircraft Flight

    Science.gov (United States)

    Golliher, Eric; Gotti, Daniel; Owens, Jay; Gilkey, Kelly; Pham, Nang; Stehno, Philip

    2016-01-01

    The recent hardware development and testing of a reduced gravity aircraft flight experiment has provided valuable insights for the future design of the Two Phase Flow Separator Experiment (TPFSE). The TPFSE is scheduled to fly within the Fluids Integration Rack (FIR) aboard the International Space Station (ISS) in 2020. The TPFSE studies the operational limits of gas and liquid separation of passive cyclonic separators. A passive cyclonic separator utilizes only the inertia of the incoming flow to accomplish the liquid-gas separation. Efficient phase separation is critical for environmental control and life support systems, such as recovery of clean water from bioreactors, for long duration human spaceflight missions. The final low gravity aircraft flight took place in December 2015 aboard NASA's C9 airplane.

  5. Meteor radar observations of vertically propagating low-frequency inertia-gravity waves near the southern polar mesopause region

    Science.gov (United States)

    Song, I.-S.; Lee, C.; Kim, J.-H.; Jee, G.; Kim, Y.-H.; Choi, H.-J.; Chun, H.-Y.; Kim, Y. H.

    2017-04-01

    Vertically propagating low-frequency inertia-gravity waves (IGWs) are retrieved from meteor radar winds observed at King Sejong Station (KSS: 62.22°S, 58.78°W), Antarctica. IGW horizontal winds extracted from temporal band-pass filtering in regular time-height bins show the frequent occurrence of IGWs with the downward phase progression and the counterclockwise rotation of their horizontal wind vectors with time (i.e., upward energy propagation) near the mesopause region throughout the whole year of 2014. The vertical wavelengths of the observed IGWs roughly range from 14 km to more than 20 km, which is consistent with previous observational studies on the mesospheric IGWs over Antarctica. Stokes parameters and rotary spectra computed from the hodographs of the IGW horizontal wind components reveal that the intrinsic frequencies of the upward propagating IGWs are |f|-3|f| with seasonal variations of the relative predominance between |f|-2|f| and 2|f|-3|f|, where f is the Coriolis parameter at KSS. The hodograph analysis also indicates that the N-S propagation is dominant in austral summer, while the NE-SW propagation is pronounced in austral winter. The propagation direction is discussed in relation to the generation of IGWs due to dynamical imbalances occurring in the tropospheric and stratospheric jet flow systems. Ray tracing results indicate that the N-S propagation in summer may be due to the jet flow systems roughly north of KSS and the NE-SW propagation in winter may be either the SW propagation from the jet flow systems northeast of KSS or the NE propagation (around the South Pole) from the south of Australia and Southern Indian and Pacific Oceans.

  6. Effects of Rotation and Gravity Field on Surface Waves in Fibre-Reinforced Thermoelastic Media under Four Theories

    Directory of Open Access Journals (Sweden)

    A. M. Abd-Alla

    2013-01-01

    Full Text Available Estimation is done to investigate the gravitational and rotational parameters effects on surface waves in fibre-reinforced thermoelastic media. The theory of generalized surface waves has been firstly developed and then it has been employed to investigate particular cases of waves, namely, Stoneley waves, Rayleigh waves, and Love waves. The analytical expressions for surface waves velocity and attenuation coefficient are obtained in the physical domain by using the harmonic vibrations and four thermoelastic theories. The wave velocity equations have been obtained in different cases. The numerical results are given for equation of coupled thermoelastic theory (C-T, Lord-Shulman theory (L-S, Green-Lindsay theory (G-L, and the linearized (G-N theory of type II. Comparison was made with the results obtained in the presence and absence of gravity, rotation, and parameters for fibre-reinforced of the material media. The results obtained are displayed by graphs to clear the phenomena physical meaning. The results indicate that the effect of gravity, rotation, relaxation times, and parameters of fibre-reinforced of the material medium is very pronounced.

  7. Seasonal and height variation of gravity wave activities observed by a meteor radar at King Sejong Station (62°S, 57°W), Antarctica

    Science.gov (United States)

    Kim, Y.; Lee, C.; Kim, J.; Choi, J.; Jee, G.

    2010-12-01

    We have analyzed wind data from individual meteor echoes detected by a meteor radar at King Sejong Station, Antarctica to measure gravity wave activity in the mesopause region. Wind data in the meteor altitudes has been obtained routinely by the meteor radar since its installation in March 2007. The mean variances in the wind data that were filtered for large scale motions (mean winds and tides) can be regarded as the gravity wave activity. Monthly mean gravity wave activities show strong seasonal and height dependences in the altitude range of 80 to 100 km. The gravity wave activities except summer monotonically increase with altitude, which is expected since decreasing atmospheric densities cause wave amplitudes to increase. During summer (Dec. - Feb.) the height profiles of gravity wave activities show a minimum near 90 - 95 km, which may be due to different zonal wind and strong wind shear near 80 - 95 km. Our gravity wave activities are generally stronger than those of the Rothera station, implying sensitive dependency on location. The difference may be related to gravity wave sources in the lower atmosphere near Antarctic vortex.

  8. Experimental Modeling of the Overtopping Flow on the Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano; Kofoed, Jens Peter; Friis-Madsen, Erik

    2011-01-01

    The Wave Dragon Wave Energy Converter is currently facing a precommercial phase. At this stage of development a reliable overtopping model is highly required, in order to predict the performance of the device at possible deployment locations. A model formulation derived for an overtopping device...... with general geometry has been used so far. The paper presents an updated formulation drawn through the tank testing of a scaled model the Wave Dragon. The sensitivity analysis of the main features influencing the overtopping flow led to an updated model formulation which can be specifically suited...... for the Wave Dragon....

  9. Distortion of gravitational-wave packets due to their self-gravity

    International Nuclear Information System (INIS)

    Kocsis, Bence; Loeb, Abraham

    2007-01-01

    When a source emits a gravity-wave (GW) pulse over a short period of time, the leading edge of the GW signal is redshifted more than the inner boundary of the pulse. The GW pulse is distorted by the gravitational effect of the self-energy residing in between these shells. We illustrate this distortion for GW pulses from the final plunge of black hole binaries, leading to the evolution of the GW profile as a function of the radial distance from the source. The distortion depends on the total GW energy released ε and the duration of the emission τ, scaled by the total binary mass M. The effect should be relevant in finite box simulations where the waveforms are extracted within a radius of 2 M. For characteristic emission parameters at the final plunge between binary black holes of arbitrary spins, this effect could distort the simulated GW templates for LIGO and LISA by a fraction of 10 -3 . Accounting for the wave distortion would significantly decrease the waveform extraction errors in numerical simulations

  10. Flow profiling of a surface acoustic wave nanopump

    OpenAIRE

    Guttenberg, Z.; Rathgeber, A.; Keller, S.; Rädler, J. O.; Wixforth, A.; Kostur, M.; Schindler, M.; Talkner, P.

    2004-01-01

    The flow profile in a capillary gap and the pumping efficiency of an acoustic micropump employing Surface Acoustic Waves is investigated both experimentally and theoretically. Such ultrasonic surface waves on a piezoelectric substrate strongly couple to a thin liquid layer and generate an internal streaming within the fluid. Such acoustic streaming can be used for controlled agitation during, e.g., microarray hybridization. We use fluorescence correlation spectroscopy and fluorescence microsc...

  11. Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

    Directory of Open Access Journals (Sweden)

    Q. T. Trinh

    2018-03-01

    Full Text Available Atmospheric gravity waves (GWs are essential for the dynamics of the middle atmosphere. Recent studies have shown that these waves are also important for the thermosphere/ionosphere (T/I system. Via vertical coupling, GWs can significantly influence the mean state of the T/I system. However, the penetration of GWs into the T/I system is not fully understood in modeling as well as observations. In the current study, we analyze the correlation between GW momentum fluxes observed in the middle atmosphere (30–90 km and GW-induced perturbations in the T/I. In the middle atmosphere, GW momentum fluxes are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER satellite instrument. In the T/I, GW-induced perturbations are derived from neutral density measured by instruments on the Gravity field and Ocean Circulation Explorer (GOCE and CHAllenging Minisatellite Payload (CHAMP satellites. We find generally positive correlations between horizontal distributions at low altitudes (i.e., below 90 km and horizontal distributions of GW-induced density fluctuations in the T/I (at 200 km and above. Two coupling mechanisms are likely responsible for these positive correlations: (1 fast GWs generated in the troposphere and lower stratosphere can propagate directly to the T/I and (2 primary GWs with their origins in the lower atmosphere dissipate while propagating upwards and generate secondary GWs, which then penetrate up to the T/I and maintain the spatial patterns of GW distributions in the lower atmosphere. The mountain-wave related hotspot over the Andes and Antarctic Peninsula is found clearly in observations of all instruments used in our analysis. Latitude–longitude variations in the summer midlatitudes are also found in observations of all instruments. These variations and strong positive correlations in the summer midlatitudes suggest that GWs with origins related to convection also

  12. Satellite observations of middle atmosphere-thermosphere vertical coupling by gravity waves

    Science.gov (United States)

    Trinh, Quang Thai; Ern, Manfred; Doornbos, Eelco; Preusse, Peter; Riese, Martin

    2018-03-01

    Atmospheric gravity waves (GWs) are essential for the dynamics of the middle atmosphere. Recent studies have shown that these waves are also important for the thermosphere/ionosphere (T/I) system. Via vertical coupling, GWs can significantly influence the mean state of the T/I system. However, the penetration of GWs into the T/I system is not fully understood in modeling as well as observations. In the current study, we analyze the correlation between GW momentum fluxes observed in the middle atmosphere (30-90 km) and GW-induced perturbations in the T/I. In the middle atmosphere, GW momentum fluxes are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. In the T/I, GW-induced perturbations are derived from neutral density measured by instruments on the Gravity field and Ocean Circulation Explorer (GOCE) and CHAllenging Minisatellite Payload (CHAMP) satellites. We find generally positive correlations between horizontal distributions at low altitudes (i.e., below 90 km) and horizontal distributions of GW-induced density fluctuations in the T/I (at 200 km and above). Two coupling mechanisms are likely responsible for these positive correlations: (1) fast GWs generated in the troposphere and lower stratosphere can propagate directly to the T/I and (2) primary GWs with their origins in the lower atmosphere dissipate while propagating upwards and generate secondary GWs, which then penetrate up to the T/I and maintain the spatial patterns of GW distributions in the lower atmosphere. The mountain-wave related hotspot over the Andes and Antarctic Peninsula is found clearly in observations of all instruments used in our analysis. Latitude-longitude variations in the summer midlatitudes are also found in observations of all instruments. These variations and strong positive correlations in the summer midlatitudes suggest that GWs with origins related to convection also propagate up to the T

  13. Aggradational lobe fringes : The influence of subtle intrabasinal seabed topography on sediment gravity flow processes and lobe stacking patterns

    NARCIS (Netherlands)

    Spychala, Yvonne T.; Hodgson, David M.; Stevenson, Christopher J.; Flint, Stephen S.

    Seabed topography is ubiquitous across basin-floor environments, and influences sediment gravity flows and sediment dispersal patterns. The impact of steep (several degrees) confining slopes on sedimentary facies and depositional architecture has been widely documented. However, the influence of

  14. Quasilinear Hyperbolic Systems, Compressible Flows, and Waves

    CERN Document Server

    Sharma, Vishnu D

    2010-01-01

    Filled with practical examples, this book presents a self-contained discussion of quasilinear hyperbolic equations and systems with applications. It emphasizes nonlinear theory and introduces some of the most active research in the field. The author elucidates all necessary mathematical concepts in the first three chapters, including an introduction to general wave propagation problems. He highlights the application of various approaches, such as singular surface theory, asymptotic methods, and self-similarity, to solve practical physical problems from areas, including gasdynamics, radiation g

  15. Generation of Zonal Flow and Magnetic Field by Electromagnetic Planetary Waves in the Ionospheric E-Layer

    Science.gov (United States)

    Kahlon, L. Z.; Kaladze, T. D.

    2017-12-01

    We review the excitation of zonal flow and magnetic field by coupled electromagnetic (EM) ULF planetary waves in the Earth's ionospheric E layer. Coupling of different planetary low-frequency electromagnetic waves under the typical ionospheric E-layer conditions is revealed. Propagation of coupled internal-gravity-Alfvén (CIGA), coupled Rossby-Khantadze (CRK) and coupled Rossby-Alfvén-Khantadze (CRAK) waves is shown and studied. A set of appropriate nonlinear equations describing the interaction of such waves with sheared zonal flow is derived. The conclusion on the instability of short wavelength turbulence of such coupled waves with respect to the excitation of low-frequency and large-scale perturbation of the sheared zonal flow and sheared magnetic field is inferred. This nonlinear instability's mechanism is depended on the parametric excitation of triple finite-amplitude coupled waves leading to the inverse energy cascade towards the longer wavelength. The possibility of generation of the intense mean magnetic field is shown. Obtained growth rates are discussed for each considered coupled waves.

  16. First 3D measurements of temperature fluctuations induced by gravity wave with the infrared limb imager GLORIA

    Science.gov (United States)

    Krisch, Isabell; Preusse, Peter; Ungermann, Jörn; Friedl-Vallon, Felix; Riese, Martin

    2017-04-01

    Gravity waves (GWs) are one of the most important coupling mechanisms in the atmosphere. They couple different compartments of the atmosphere. The GW-LCYCLE (Gravity Wave Life Cycle) project aims on studying the excitation, propagation, and dissipation of gravity waves. An aircraft campaign has been performed in winter 2015/2016, during which the first 3D tomographic measurements of GWs were performed with the infrared limb imager GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere). GLORIA combines a classical Fourier Transform Spectrometer with a 2D detector array. The capability to image the atmosphere and thereby take several thousand spectra simultaneously improves the spatial sampling compared to conventional limb sounders by an order of magnitude. Furthermore GLORIA is able to pan the horizontal viewing direction and therefore measure the same volume of air under different angles. Due to these properties tomographic methods can be used to derive 3D temperature and tracer fields with spatial resolutions of better than 30km x 30km x 250m from measurements taken during circular flight patterns. Temperature distributions measured during a strong GW event on the 25.01.2016 during the GW-LCycle campaign over Iceland will be presented and analyzed for gravity waves. The three dimensional nature of the GLORIA measurements allows for the determination of the gravity wave momentum flux, including its horizontal direction. The calculated momentum fluxes rank this event under one of the strongest 1% observed in that latitude range in January 2016. The three dimensional wave vectors determined from the GLORIA measurements can be used for a ray tracing study with the Gravity wave Regional Or Global RAy Tracer (GROGRAT). Here 1D ray tracing, meaning solely vertical column propagation, as used by standard parameterizations in numerical weather prediction and climate models is compared to 4D ray tracing (spatially three dimensional with time varying

  17. Flow profiling of a surface-acoustic-wave nanopump

    Science.gov (United States)

    Guttenberg, Z.; Rathgeber, A.; Keller, S.; Rädler, J. O.; Wixforth, A.; Kostur, M.; Schindler, M.; Talkner, P.

    2004-11-01

    The flow profile in a capillary gap and the pumping efficiency of an acoustic micropump employing surface acoustic waves is investigated both experimentally and theoretically. Ultrasonic surface waves on a piezoelectric substrate strongly couple to a thin liquid layer and generate a quadrupolar streaming pattern within the fluid. We use fluorescence correlation spectroscopy and fluorescence microscopy as complementary tools to investigate the resulting flow profile. The velocity was found to depend on the applied power approximately linearly and to decrease with the inverse third power of the distance from the ultrasound generator on the chip. The found properties reveal acoustic streaming as a promising tool for the controlled agitation during microarray hybridization.

  18. Numerical modeling study of the momentum deposition of small amplitude gravity waves in the thermosphere

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X. [Chinese Academy of Sciences, Beijing (China). State Key Lab. of Space Weather; Henan Normal Univ., Xinxiang (China). College of Mathematics and Information Science; Xu, J. [Chinese Academy of Sciences, Beijing (China). State Key Lab. of Space Weather; Yue, J. [National Center for Atmospheric Research, Boulder, CO (United States). High Altitude Observatory; Hampton Univ., VA (United States). Atmospheric and Planetary Sciences; Vadas, S.L. [North West Research Associates, Inc., Boulder, CO (United States)

    2013-03-01

    We study the momentum deposition in the thermosphere from the dissipation of small amplitude gravity waves (GWs) within a wave packet using a fully nonlinear two-dimensional compressible numerical model. The model solves the nonlinear propagation and dissipation of a GW packet from the stratosphere into the thermosphere with realistic molecular viscosity and thermal diffusivity for various Prandtl numbers. The numerical simulations are performed for GW packets with initial vertical wavelengths ({lambda}{sub z}) ranging from 5 to 50 km. We show that {lambda}{sub z} decreases in time as a GW packet dissipates in the thermosphere, in agreement with the ray trace results of Vadas and Fritts (2005) (VF05). We also find good agreement for the peak height of the momentum flux (z{sub diss}) between our simulations and VF05 for GWs with initial {lambda}{sub z} {<=} 2{pi}H in an isothermal, windless background, where H is the density scale height.We also confirm that z{sub diss} increases with increasing Prandtl number. We include eddy diffusion in the model, and find that the momentum deposition occurs at lower altitudes and has two separate peaks for GW packets with small initial {lambda}{sub z}. We also simulate GW packets in a non-isothermal atmosphere. The net {lambda}{sub z} profile is a competition between its decrease from viscosity and its increase from the increasing background temperature. We find that the wave packet disperses more in the non-isothermal atmosphere, and causes changes to the momentum flux and {lambda}{sub z} spectra at both early and late times for GW packets with initial {lambda}{sub z} {>=} 10 km. These effects are caused by the increase in T in the thermosphere, and the decrease in T near the mesopause. (orig.)

  19. Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2009-11-01

    Full Text Available This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θc versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θc~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.

  20. Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2009-11-01

    Full Text Available This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θc versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θc~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.

  1. Turbulent Flow Modification With Thermoacoustic Waves for Separation Control

    Science.gov (United States)

    2017-08-24

    respectively. At the outlet, the time-average flow is set to be the target state of the sponge zone. In this section, the effects of momentum thickness...Turbulent Flow Modification With Thermoacoustic Waves For Separation Control The views, opinions and/or findings contained in this report are those...currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. Florida State University Sponsored Research Administration 874

  2. RG flow and thermodynamics of causal horizons in higher-derivative AdS gravity

    International Nuclear Information System (INIS)

    Banerjee, Shamik; Bhattacharyya, Arpan

    2016-01-01

    In http://arxiv.org/abs/1508.01343 [hep-th], one of the authors proposed that in AdS/CFT the gravity dual of the boundary c-theorem is the second law of thermodynamics satisfied by causal horizons in AdS and this was verified for Einstein gravity in the bulk. In this paper we verify this for higher derivative theories. We pick up theories for which an entropy expression satisfying the second law exists and show that the entropy density evaluated on the causal horizon in a RG flow geometry is a holographic c-function. We also prove that given a theory of gravity described by a local covariant action in the bulk a sufficient condition to ensure holographic c-theorem is that the second law of causal horizon thermodynamics be satisfied by the theory. This allows us to explicitly construct holographic c-function in a theory where there is curvature coupling between gravity and matter and standard null energy condition cannot be defined although second law is known to hold. Based on the duality between c-theorem and the second law of causal horizon thermodynamics proposed in http://arxiv.org/abs/1508.01343 [hep-th] and the supporting calculations of this paper we conjecture that every Unitary higher derivative theory of gravity in AdS satisfies the second law of causal horizon thermodynamics. If this is not true then c-theorem will be violated in a unitary Lorentz invariant field theory.

  3. Derivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning OH(3-1) airglow spectrometer

    Science.gov (United States)

    Wüst, Sabine; Offenwanger, Thomas; Schmidt, Carsten; Bittner, Michael; Jacobi, Christoph; Stober, Gunter; Yee, Jeng-Hwa; Mlynczak, Martin G.; Russell, James M., III

    2018-05-01

    For the first time, we present an approach to derive zonal, meridional, and vertical wavelengths as well as periods of gravity waves based on only one OH* spectrometer, addressing one vibrational-rotational transition. Knowledge of these parameters is a precondition for the calculation of further information, such as the wave group velocity vector.OH(3-1) spectrometer measurements allow the analysis of gravity wave ground-based periods but spatial information cannot necessarily be deduced. We use a scanning spectrometer and harmonic analysis to derive horizontal wavelengths at the mesopause altitude above Oberpfaffenhofen (48.09° N, 11.28° E), Germany for 22 nights in 2015. Based on the approximation of the dispersion relation for gravity waves of low and medium frequencies and additional horizontal wind information, we calculate vertical wavelengths. The mesopause wind measurements nearest to Oberpfaffenhofen are conducted at Collm (51.30° N, 13.02° E), Germany, ca. 380 km northeast of Oberpfaffenhofen, by a meteor radar.In order to compare our results, vertical temperature profiles of TIMED-SABER (thermosphere ionosphere mesosphere energetics dynamics, sounding of the atmosphere using broadband emission radiometry) overpasses are analysed with respect to the dominating vertical wavelength.

  4. Gravity flow operated small electricity generator retrofit kit to flour mill industry.

    Science.gov (United States)

    Shekara, Prithivi; Kumar V, Pavan; Hosamane, Gangadharappa Gundabhakthara

    2013-10-01

    Flour milling is a grinding process to produce flour from wheat through comprehensive stages of grinding and separation. The primary energy is required to provide power used in grinding of wheat. In wheat milling, tempering is the process of adding water to wheat before milling to toughen the bran and mellow the endosperm. Gravity flow of the wheat is utilized to rotate the dampener wheel with cups to add water. Low cost gravity flow operated small electricity generator retrofit kit for dampener was designed and developed to justify low cost energy production without expensive solutions. Results of statistical analysis indicated that there was significant difference in mean values for voltage, rpm and flow rate at the 95% probability level. The resulted maximum mechanical power and measured electrical power were 5.1 W and 4.9 W respectively at wheat flow rate of 1.6 Kg/s and dampener wheel rotational velocity of 4.4 rad/s.

  5. Gravity wave control on ESF day-to-day variability: An empirical approach

    Science.gov (United States)

    Aswathy, R. P.; Manju, G.

    2017-06-01

    The gravity wave control on the daily variation in nighttime ionization irregularity occurrence is studied using ionosonde data for the period 2002-2007 at magnetic equatorial location Trivandrum. Recent studies during low solar activity period have revealed that the seed perturbations should have the threshold amplitude required to trigger equatorial spread F (ESF), at a particular altitude and that this threshold amplitude undergoes seasonal and solar cycle changes. In the present study, the altitude variation of the threshold seed perturbations is examined for autumnal equinox of different years. Thereafter, a unique empirical model, incorporating the electrodynamical effects and the gravity wave modulation, is developed. Using the model the threshold curve for autumnal equinox season of any year may be delineated if the solar flux index (F10.7) is known. The empirical model is validated using the data for high, moderate, and low solar epochs in 2001, 2004, and 1995, respectively. This model has the potential to be developed further, to forecast ESF incidence, if the base height of ionosphere is in the altitude region where electrodynamics controls the occurrence of ESF. ESF irregularities are harmful for communication and navigation systems, and therefore, research is ongoing globally to predict them. In this context, this study is crucial for evolving a methodology to predict communication as well as navigation outages.Plain Language SummaryThe manifestation of nocturnal ionospheric irregularities at magnetic equatorial regions poses a major hazard for communication and navigation systems. It is therefore essential to arrive at prediction methodologies for these irregularities. The present study puts forth a novel empirical model which, using only solar flux index, successfully differentiates between days with and without nocturnal ionization irregularity occurrence. The model-derived curve is obtained such that the days with and without occurrence of

  6. Sedimentary gravity flows from subaerial fan-deltas in Loreto Bay, Baja California Sur, Mexico

    Science.gov (United States)

    Navarro-Lozano, José O.; Nava-Sánchez, Enrique H.; Godínez-Orta, Lucio

    2010-05-01

    Fan-deltas from Loreto Bay show recent evidences of sedimentary gravity flows as a result from catastrophic events during hurricane rainfalls. The knowledge of hydrological characteristics of these flows is important for understanding the effects of storms on fan-deltas geomorphology in this region, as well as for the urban developing planning of the city of Loreto in order to avoid hazardous zones. The analysis of precipitation and hurricane tracks data for the period 1945 to 2009 indicates that hurricanes have caused catastrophic floods every 20 years. Stratigraphy from the channel incision shows a sequence of stream flow and debris flow controlled by changes in the competence and capacity of the stream, which are associated to the gentle slope (<2 °) of the fan-deltas. However fans from the north of the bay (Arce and Gúa) show deposits of debris flows associated to catastrophic floods, which have caused the incision channel to drift towards the southern part of the fans, while flows from Las Parras fan-delta, from the middle of the bay, are dominated by stream flows. These differences in the type of the flows are controlled by lithology, shape and size of the drainage basin, and slope of the transit zone in the feeder channel.

  7. Interactions of solitary waves and compression/expansion waves in core-annular flows

    Science.gov (United States)

    Maiden, Michelle; Anderson, Dalton; El, Gennady; Franco, Nevil; Hoefer, Mark

    2017-11-01

    The nonlinear hydrodynamics of an initial step leads to the formation of rarefaction waves and dispersive shock waves in dispersive media. Another hallmark of these media is the soliton, a localized traveling wave whose speed is amplitude dependent. Although compression/expansion waves and solitons have been well-studied individually, there has been no mathematical description of their interaction. In this talk, the interaction of solitons and shock/rarefaction waves for interfacial waves in viscous, miscible core-annular flows are modeled mathematically and explored experimentally. If the interior fluid is continuously injected, a deformable conduit forms whose interfacial dynamics are well-described by a scalar, dispersive nonlinear partial differential equation. The main focus is on interactions of solitons with dispersive shock waves and rarefaction waves. Theory predicts that a soliton can either be transmitted through or trapped by the extended hydrodynamic state. The notion of reciprocity is introduced whereby a soliton interacts with a shock wave in a reciprocal or dual fashion as with the rarefaction. Soliton reciprocity, trapping, and transmission are observed experimentally and are found to agree with the modulation theory and numerical simulations. This work was partially supported by NSF CAREER DMS-1255422 (M.A.H.) and NSF GRFP (M.D.M.).

  8. Estimating Jupiter’s Gravity Field Using Juno Measurements, Trajectory Estimation Analysis, and a Flow Model Optimization

    International Nuclear Information System (INIS)

    Galanti, Eli; Kaspi, Yohai; Durante, Daniele; Finocchiaro, Stefano; Iess, Luciano

    2017-01-01

    The upcoming Juno spacecraft measurements have the potential of improving our knowledge of Jupiter’s gravity field. The analysis of the Juno Doppler data will provide a very accurate reconstruction of spatial gravity variations, but these measurements will be very accurate only over a limited latitudinal range. In order to deduce the full gravity field of Jupiter, additional information needs to be incorporated into the analysis, especially regarding the Jovian flow structure and its depth, which can influence the measured gravity field. In this study we propose a new iterative method for the estimation of the Jupiter gravity field, using a simulated Juno trajectory, a trajectory estimation model, and an adjoint-based inverse model for the flow dynamics. We test this method both for zonal harmonics only and with a full gravity field including tesseral harmonics. The results show that this method can fit some of the gravitational harmonics better to the “measured” harmonics, mainly because of the added information from the dynamical model, which includes the flow structure. Thus, it is suggested that the method presented here has the potential of improving the accuracy of the expected gravity harmonics estimated from the Juno and Cassini radio science experiments.

  9. Estimating Jupiter’s Gravity Field Using Juno Measurements, Trajectory Estimation Analysis, and a Flow Model Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Galanti, Eli; Kaspi, Yohai [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot (Israel); Durante, Daniele; Finocchiaro, Stefano; Iess, Luciano, E-mail: eli.galanti@weizmann.ac.il [Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Universita di Roma, Rome (Italy)

    2017-07-01

    The upcoming Juno spacecraft measurements have the potential of improving our knowledge of Jupiter’s gravity field. The analysis of the Juno Doppler data will provide a very accurate reconstruction of spatial gravity variations, but these measurements will be very accurate only over a limited latitudinal range. In order to deduce the full gravity field of Jupiter, additional information needs to be incorporated into the analysis, especially regarding the Jovian flow structure and its depth, which can influence the measured gravity field. In this study we propose a new iterative method for the estimation of the Jupiter gravity field, using a simulated Juno trajectory, a trajectory estimation model, and an adjoint-based inverse model for the flow dynamics. We test this method both for zonal harmonics only and with a full gravity field including tesseral harmonics. The results show that this method can fit some of the gravitational harmonics better to the “measured” harmonics, mainly because of the added information from the dynamical model, which includes the flow structure. Thus, it is suggested that the method presented here has the potential of improving the accuracy of the expected gravity harmonics estimated from the Juno and Cassini radio science experiments.

  10. Gravity-driven granular flow in a silo: Characterizing local forces and rearrangements

    Directory of Open Access Journals (Sweden)

    Thackray Emma

    2017-01-01

    Full Text Available While the gravity-driven flow of a granular material in a silo geometry can be modeled by the Beverloo equation, the mesoscale-level particle rearrangements and interactions that drive this flow are not wellunderstood. We have constructed a quasi-two-dimensional system of bidisperse, millimeter-scale disks with photoelastic properties that make force networks within the material visible. The system is contained in an acrylic box with an adjustable bottom opening. We can approach the clogging transition by adjusting this opening. By placing the system between cross-polarizers, we can obtain high-speed video of this system during flow, and extract intensity signals that can be used to identify and quantify localized, otherwise indeterminate forces. We can simultaneously track individual particle motions, which can be used to identify shear transformation zones in the system. In this paper, we present our results thus far.

  11. Enhanced gravity-wave activity and interhemispheric coupling during the MaCWAVE/MIDAS northern summer program 2002

    Directory of Open Access Journals (Sweden)

    E. Becker

    2006-07-01

    Full Text Available We present new sensitivity experiments that link observed anomalies of the mesosphere and lower thermosphere at high latitudes during the MaCWAVE/MIDAS summer program 2002 to enhanced planetary Rossby-wave activity in the austral winter troposphere.

    We employ the same general concept of a GCM having simplified representations of radiative and latent heating as in a previous study by Becker et al. (2004. In the present version, however, the model includes no gravity wave (GW parameterization. Instead we employ a high vertical and a moderate horizontal resolution in order to describe GW effects explicitly. This is supported by advanced, nonlinear momentum diffusion schemes that allow for a self-consistent generation of inertia and mid-frequency GWs in the lower atmosphere, their vertical propagation into the mesosphere and lower thermosphere, and their subsequent dissipation which is induced by prescribed horizontal and vertical mixing lengths as functions of height.

    The main anomalies in northern summer 2002 consist of higher temperatures than usual above 82 km, an anomalous eastward mean zonal wind between 70 and 90 km, an altered meridional flow, enhanced turbulent dissipation below 80 km, and enhanced temperature variations associated with GWs. These signals are all reasonably described by differences between two long-integration perpetual model runs, one with normal July conditions, and another run with modified latent heating in the tropics and Southern Hemisphere to mimic conditions that correspond to the unusual austral winter 2002. The model response to the enhanced winter hemisphere Rossby-wave activity has resulted in both an interhemispheric coupling through a downward shift of the GW-driven branch of the residual circulation and an increased GW activity at high summer latitudes. Thus a quantitative explanation of the dynamical state of the northern mesosphere and lower

  12. Excitation of nonlinear wave patterns in flowing complex plasmas

    Science.gov (United States)

    Jaiswal, S.; Bandyopadhyay, P.; Sen, A.

    2018-01-01

    We describe experimental observations of nonlinear wave structures excited by a supersonic mass flow of dust particles over an electrostatic potential hill in a dusty plasma medium. The experiments have been carried out in a Π- shaped experimental (DPEx) device in which micron sized Kaolin particles are embedded in a DC glow discharge Argon plasma. An equilibrium dust cloud is formed by maintaining the pumping speed and gas flow rate and the dust flow is induced either by suddenly reducing the height of a potential hill or by suddenly reducing the gas flow rate. For a supersonic flow of the dust fluid precursor solitons are seen to propagate in the upstream direction while wake structures propagate in the downstream direction. For flow speeds with a Mach number greater than 2 the dust particles flowing over the potential hill give rise to dispersive dust acoustic shock waves. The experimental results compare favorably with model theories based on forced K-dV and K-dV Burger's equations.

  13. Axisymmetric capillary-gravity waves at the interface of two viscous, immiscible fluids - Initial value problem

    Science.gov (United States)

    Farsoiya, Palas Kumar; Dasgupta, Ratul

    2017-11-01

    When the interface between two radially unbounded, viscous fluids lying vertically in a stable configuration (denser fluid below) at rest, is perturbed, radially propagating capillary-gravity waves are formed which damp out with time. We study this process analytically using a recently developed linearised theory. For small amplitude initial perturbations, the analytical solution to the initial value problem, represented as a linear superposition of Bessel modes at time t = 0 , is found to agree very well with results obtained from direct numerical simulations of the Navier-Stokes equations, for a range of initial conditions. Our study extends the earlier work by John W. Miles who studied this initial value problem analytically, taking into account, a single viscous fluid only. Implications of this study for the mechanistic understanding of droplet impact into a deep pool, will be discussed. Some preliminary, qualitative comparison with experiments will also be presented. We thank SERB Dept. Science & Technology, Govt. of India, Grant No. EMR/2016/000830 for financial support.

  14. Evidence for Gravity Wave Seeding of Convective Ionosphere Storms Initiated by Deep Troposphere Convection

    Science.gov (United States)

    Kelley, M. C.; Pfaff, R. F., Jr.; Dao, E. V.; Holzworth, R. H., II

    2014-12-01

    With the increase in solar activity, the Communications/Outage Forecast System satellite (C/NOFS) now goes below the F peak. As such, we now can study the development of Convective Ionospheric Storms (CIS) and, most importantly, large-scale seeding of the low growth-rate Rayleigh-Taylor (R-T) instability. Two mechanisms have been suggested for such seeding: the Collisional Kelvin-Helmholtz Instability (CKHI) and internal atmospheric gravity waves. A number of observations have shown that the spectrum of fully developed topside structures peaks at 600 km and extends to over 1000 km. These structures are exceedingly difficult to explain by CKHI. Here we show that sinusoidal plasma oscillations on the bottomside during daytime develop classical R-T structures on the nightside with the background 600 km structure still apparent. In two case studies, thunderstorm activity was observed east of the sinusoidal features in the two hours preceding the C/NOFS passes. Thus, we argue that convective tropospheric storms are a likely source of these sinusoidal features.

  15. Frequency variations of gravity waves interacting with a time-varying tide

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.M.; Zhang, S.D.; Yi, F.; Huang, K.M.; Gan, Q.; Gong, Y. [Wuhan Univ., Hubei (China). School of Electronic Information; Ministry of Education, Wuhan, Hubei (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan, Hubei (China); Zhang, Y.H. [Nanjing Univ. of Information Science and Technology (China). College of Hydrometeorolgy

    2013-11-01

    Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs) in a time-varying tide. Our simulations show that when aGW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative) accelerations induce frequency increases (decreases) with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal-GW interactions are more complicated than usually taken into account by GW parameterizations in global models.

  16. Inertia–gravity wave radiation from the elliptical vortex in the f -plane shallow water system

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, Norihiko, E-mail: nori@phys-h.keio.ac.jp [Research and Education Center for Natural Sciences, Department of Physics, Keio University, 4-1-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8521 (Japan)

    2017-04-15

    Inertia–gravity wave (IGW) radiation from the elliptical vortex is investigated in the f -plane shallow water system. The far field of IGW is analytically derived for the case of an almost circular Kirchhoff vortex with a small aspect ratio. Cyclone–anticyclone asymmetry appears at finite values of the Rossby number (Ro) caused by the source originating in the Coriolis acceleration. While the intensity of IGWs from the cyclone monotonically decreases as f increases, that from the anticyclone increases as f increases for relatively smaller f and has a local maximum at intermediate f . A numerical experiment is conducted on a model using a spectral method in an unbounded domain. The numerical results agree quite well with the analytical ones for elliptical vortices with small aspect ratios, implying that the derived analytical forms are useful for the verification of the numerical model. For elliptical vortices with larger aspect ratios, however, significant deviation from the analytical estimates appears. The intensity of IGWs radiated in the numerical simulation is larger than that estimated analytically. The reason is that the source of IGWs is amplified during the time evolution because the shape of the vortex changes from ideal ellipse to elongated with filaments. Nevertheless, cyclone–anticyclone asymmetry similar to the analytical estimate appears in all the range of aspect ratios, suggesting that this asymmetry is a robust feature. (paper)

  17. Some characteristics of atmospheric gravity waves observed by radio-interferometry

    Directory of Open Access Journals (Sweden)

    Claude Mercier

    Full Text Available Observations of atmospheric acoustic-gravity waves (AGWs are considered through their effect on the horizontal gradient G of the slant total electron content (slant TEC, which can be directly obtained from two-dimensional radio-interferometric observations of cosmic radio-sources with the Nançay radioheligraph (2.2°E, 47.3°N. Azimuths of propagation can be deduced (modulo 180°. The total database amounts to about 800 h of observations at various elevations, local time and seasons. The main results are:

    a AGWs are partially directive, confirming our previous results.

    b The propagation azimuths considered globally are widely scattered with a preference towards the south.

    c They show a bimodal time distribution with preferential directions towards the SE during daytime and towards the SW during night-time (rather than a clockwise rotation as reported by previous authors.

    d The periods are scattered but are larger during night-time than during daytime by about 60%.

    e The effects observed with the solar radio-sources are significantly stronger than with other radio-sources (particularly at higher elevations, showing the role of the geometry in line of sight-integrated observations.

  18. Precise response function for the magnetic component of gravitational waves in scalar-tensor gravity

    International Nuclear Information System (INIS)

    Corda, Christian

    2011-01-01

    The important issue of the magnetic component of gravitational waves (GWs) has been considered in various papers in the literature. From such analyses, it has been found that such a magnetic component becomes particularly important in the high-frequency portion of the frequency range of ground based interferometers for GWs which arises from standard general theory of relativity (GTR). Recently, such a magnetic component has been extended to GWs arising from scalar-tensor gravity (STG) too. After a review of some important issues on GWs in STG, in this paper we reanalyze the magnetic component in the framework of STG from a different point of view, by correcting an error in a previous paper and by releasing a more precise response function. In this way, we also show that if one neglects the magnetic contribution considering only the low-frequency approximation of the electric contribution, an important part of the signal could be, in principle, lost. The determination of a more precise response function for the magnetic contribution is important also in the framework of the possibility of distinguishing other gravitational theories from GTR. At the conclusion of this paper, an expansion of the main results is also shown in order to recall the presence of the magnetic component in GTR too.

  19. Electronics for the IBM gravity wave detector. Concept, implementation, and experience

    International Nuclear Information System (INIS)

    Levine, J.L.; Garwin, R.L.

    1975-01-01

    The apparatus - antenna, transducer, signal processor, and calibrator - was designed to settle the question of the existence of gravity waves at 1.7kHz of the numbers and intensities claimed at the time (end-1971). The design criteria were: modest sensitivity, sensitivity independent of signal arrival time and state of excitation of the antenna, absolute calibration with pulsed mechanical excitation of the antenna, full simulation of the apparatus, hands-off computer analysis with every point published. It was recognized that a single bar would ultimately be limited by some Boltzmann distribution of noise at sub-thermal temperature, and that such an ideal antenna would be equivalent to an ideal coincidence pair of antennas, each of half the mass. Transducer, amplifier, signal processor, and programming were all done by the experimenters in order to reduce the cycle time for introducing improvements. Before the antenna and amplifier were ready, the processing algorithms were developed and tested with digitally-simulated antenna output, and many problems avoided. Any excess local noise proved to be sufficiently infrequent so that the single antenna could negate claims by Weber of the detection of gravitational radiation. The computer processing obviated the need for temperature control of the antenna or for tracking of the bar resonant frequency with the reference oscillator

  20. Gravity Wave Dynamics in a Mesospheric Inversion Layer: 1. Reflection, Trapping, and Instability Dynamics

    Science.gov (United States)

    Laughman, Brian; Wang, Ling; Lund, Thomas S.; Collins, Richard L.

    2018-01-01

    Abstract An anelastic numerical model is employed to explore the dynamics of gravity waves (GWs) encountering a mesosphere inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. Instabilities occur within the MIL when the GW amplitude approaches that required for GW breaking due to compression of the vertical wavelength accompanying the increasing static stability. Thus, MILs can cause large‐amplitude GWs to yield instabilities and turbulence below the altitude where they would otherwise arise. Smaller‐amplitude GWs encountering a MIL do not lead to instability and turbulence but do exhibit partial reflection and transmission, and the transmission is a smaller fraction of the incident GW when instabilities and turbulence arise within the MIL. Additionally, greater GW transmission occurs for weaker MILs and for GWs having larger vertical wavelengths relative to the MIL depth and for lower GW intrinsic frequencies. These results imply similar dynamics for inversions due to other sources, including the tropopause inversion layer, the high stability capping the polar summer mesopause, and lower frequency GWs or tides having sufficient amplitudes to yield significant variations in stability at large and small vertical scales. MILs also imply much stronger reflections and less coherent GW propagation in environments having significant fine structure in the stability and velocity fields than in environments that are smoothly varying. PMID:29576994

  1. Nonlinear travelling waves in rotating Hagen–Poiseuille flow

    Science.gov (United States)

    Pier, Benoît; Govindarajan, Rama

    2018-03-01

    The dynamics of viscous flow through a rotating pipe is considered. Small-amplitude stability characteristics are obtained by linearizing the Navier–Stokes equations around the base flow and solving the resulting eigenvalue problems. For linearly unstable configurations, the dynamics leads to fully developed finite-amplitude perturbations that are computed by direct numerical simulations of the complete Navier–Stokes equations. By systematically investigating all linearly unstable combinations of streamwise wave number k and azimuthal mode number m, for streamwise Reynolds numbers {{Re}}z ≤slant 500 and rotational Reynolds numbers {{Re}}{{Ω }} ≤slant 500, the complete range of nonlinear travelling waves is obtained and the associated flow fields are characterized.

  2. Gravity-driven groundwater flow and slope failure potential: 1. Elastic effective-stress model

    Science.gov (United States)

    Iverson, Richard M.; Reid, Mark E.

    1992-01-01

    Hilly or mountainous topography influences gravity-driven groundwater flow and the consequent distribution of effective stress in shallow subsurface environments. Effective stress, in turn, influences the potential for slope failure. To evaluate these influences, we formulate a two-dimensional, steady state, poroelastic model. The governing equations incorporate groundwater effects as body forces, and they demonstrate that spatially uniform pore pressure changes do not influence effective stresses. We implement the model using two finite element codes. As an illustrative case, we calculate the groundwater flow field, total body force field, and effective stress field in a straight, homogeneous hillslope. The total body force and effective stress fields show that groundwater flow can influence shear stresses as well as effective normal stresses. In most parts of the hillslope, groundwater flow significantly increases the Coulomb failure potential Φ, which we define as the ratio of maximum shear stress to mean effective normal stress. Groundwater flow also shifts the locus of greatest failure potential toward the slope toe. However, the effects of groundwater flow on failure potential are less pronounced than might be anticipated on the basis of a simpler, one-dimensional, limit equilibrium analysis. This is a consequence of continuity, compatibility, and boundary constraints on the two-dimensional flow and stress fields, and it points to important differences between our elastic continuum model and limit equilibrium models commonly used to assess slope stability.

  3. Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign. Part II. Radar investigations and modelling studies

    Energy Technology Data Exchange (ETDEWEB)

    Serafimovich, A.; Zuelicke, C.; Hoffmann, P.; Peters, D.; Singer, W. [Leibniz-Inst. fuer Atmosphaerenphysik, Kuehlungsborn (Germany); Dalin, P. [Swedish Inst. of Space Physics, Kiruna (Sweden)

    2006-07-01

    We present an experimental and modelling study of a strong gravity wave event in the upper troposphere/lower stratosphere near the Scandinavian mountain ridge. Continuous VHP radar measurements during the MaCWAVE rocket and ground-based measurement campaign were performed at the Norwegian Andoya rocket range (ARR) near Andenes (69.3 N, 16 E) in January 2003. Detailed gravity wave investigations based on PSU/NCAR fifth-generation mesoscale model (MM5) data have been used for comparison with experimentally obtained results. The model data show the presence of a mountain wave and of an inertia gravity wave generated by a jet streak near the tropopause region. Temporal and spatial dependencies of jet induced inertia gravity waves with dominant observed periods of about 13 h and vertical wavelengths of {proportional_to}4.5-5 km are investigated with wavelet transform applied on radar measurements and model data. The jet induced wave packet is observed to move upstream and downward in the upper troposphere. The model data agree with the experimentally obtained results fairly well. Possible reasons for the observed differences, e.g. in the time of maximum of the wave activity, are discussed. Finally, the vertical fluxes of horizontal momentum are estimated with different methods and provide similar amplitudes. We found indications that the derived positive vertical flux of the horizontal momentum corresponds to the obtained parameters of the jet-induced inertia gravity wave, but only at the periods and heights of the strongest wave activity. (orig.)

  4. Simulations of large winds and wind shears induced by gravity wave breaking in the mesosphere and lower thermosphere (MLT) region

    OpenAIRE

    X. Liu; X. Liu; J. Xu; H.-L. Liu; J. Yue; W. Yuan

    2014-01-01

    Using a fully nonlinear two-dimensional (2-D) numerical model, we simulated gravity waves (GWs) breaking and their contributions to the formation of large winds and wind shears in the mesosphere and lower thermosphere (MLT). An eddy diffusion coefficient is used in the 2-D numerical model to parameterize realistic turbulent mixing. Our study shows that the momentum deposited by breaking GWs accelerates the mean wind. The resultant large background wind increases the GW's app...

  5. Planetary and gravity wave signatures in the F region ionosphere with impact on radio propagation predictions and variability

    Czech Academy of Sciences Publication Activity Database

    Altadill, D.; Apostolov, E. M.; Boška, Josef; Laštovička, Jan; Šauli, Petra

    2004-01-01

    Roč. 47, 2/3 (2004), s. 1109-1119 ISSN 1593-5213. [Final Meeting COST271 Action. Effects of the upper atmosphere on terrestrial and Earth-space communications (EACOS). Abingdon, 26.08.2004-27.08.2004] R&D Projects: GA MŠk OC 271.10; GA ČR GA205/01/1071; GA ČR GP205/02/P077 Institutional research plan: CEZ:AV0Z3042911 Keywords : ionosphere * planetary waves * gravity waves Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.413, year: 2004

  6. Wavelet characterisation of ionospheric acoustic and gravity waves occuring during the solar eclipse of August 11, 1999

    Czech Academy of Sciences Publication Activity Database

    Šauli, Petra; Abry, P.; Boška, Josef; Duchayne, L.

    2006-01-01

    Roč. 68, 3-5 (2006), s. 586-598 ISSN 1364-6826 R&D Projects: GA ČR GP205/02/P077; GA ČR(CZ) GA205/01/1071; GA AV ČR(CZ) IAA3042102 Grant - others:CNRS(FR) 18098 Institutional research plan: CEZ:AV0Z30420517 Keywords : Solar eclipse * Acoustic-gravity waves * Vertical ionospheric sounding * Wavelet decomposition * Wave packet characterisation Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.448, year: 2006

  7. Generation of Acoustic Gravity Waves by Periodic Radio Transmissions from a High-Power Ionospheric Heater

    Science.gov (United States)

    Frolov, Vladimir; Chernogor, Leonid; Rozumenko, Victor

    The Radiophysical Research Institute (Nizhny Novgorod, Russia) and Kharkiv V. N. Karazin National University (Kharkiv, Ukraine) have studied opportunities for the effective generation of acoustic gravity waves (AGWs) in 3 - 180-min period range. The excitation of such waves was conducted for the last several years using the SURA heating facility (Nizhny Novgorod). The detection of the HF-induced AGWs was carried out in the Radiophysical Observatory located near Kharkiv City at a distance of about 960 km from the SURA. A coherent radar for vertical sounding, an ionosonde, and magnetometer chains were used in our measurements. The main results are the following (see [1-5]): 1. Infrasound oscillation trains with a period of 6 min are detected during periodic SURA heater turn-on and -off. Similar oscillation trains are detected after long time pumping, during periodic transmissions with a period of 20 s, as well as after pumping turn-off. The train recordings begin 28 - 54 min after the heater turn-on or -off, and the train propagation speeds are about 300 - 570 m/s, the value of which is close to the sound speed at upper atmospheric altitudes. The amplitude of the Doppler shift frequency is of 10 - 40 mHz, which fits to the 0.1 - 0.3% electron density disturbances at ionospheric altitudes. The amplitude of the infrasound oscillations depends on the SURA mode of operation and the state of the upper atmosphere and ionosphere. 2. High-power radio transmissions stimulate the generation (or enhancement) of waves at ionospheric altitudes in the range of internal gravity wave periods. The HF-induced waves propagate with speeds of 360 - 460 m/s and produce changes in electron density with amplitudes of 2 - 3%. The generation of such periodic perturbations is more preferable with periods of 10 - 60 minutes. Their features depend significantly on the heater mode of operation. It should be stressed that perturbation intensity increases when a pumping wave frequency approaches

  8. Separation of acoustic waves in isentropic flow perturbations

    International Nuclear Information System (INIS)

    Henke, Christian

    2015-01-01

    The present contribution investigates the mechanisms of sound generation and propagation in the case of highly-unsteady flows. Based on the linearisation of the isentropic Navier–Stokes equation around a new pathline-averaged base flow, it is demonstrated for the first time that flow perturbations of a non-uniform flow can be split into acoustic and vorticity modes, with the acoustic modes being independent of the vorticity modes. Therefore, we can propose this acoustic perturbation as a general definition of sound. As a consequence of the splitting result, we conclude that the present acoustic perturbation is propagated by the convective wave equation and fulfils Lighthill’s acoustic analogy. Moreover, we can define the deviations of the Navier–Stokes equation from the convective wave equation as “true” sound sources. In contrast to other authors, no assumptions on a slowly varying or irrotational flow are necessary. Using a symmetry argument for the conservation laws, an energy conservation result and a generalisation of the sound intensity are provided. - Highlights: • First splitting of non-uniform flows in acoustic and non-acoustic components. • These result leads to a generalisation of sound which is compatible with Lighthill’s acoustic analogy. • A closed equation for the generation and propagation of sound is given

  9. A case study of the energy dissipation of the gravity wave field based on satellite altimeter measurements

    Science.gov (United States)

    Huang, N. E.; Parsons, C. L.; Long, S. R.; Bliven, L. F.

    1983-01-01

    Wave breaking is proposed as the primary energy dissipation mechanism for the gravity wave field. The energy dissipation rate is calculated based on the statistical model proposed by Longuet-Higgins (1969) with a modification of the breaking criterion incorporating the surface stress according to Phillips and Banner (1974). From this modified model, an analytic expression is found for the wave attenuation rate and the half-life time of the wave field which depend only on the significant slope of the wave field and the ratio of friction velocity to initial wave phase velocity. These expressions explain why the freshly generated wave field does not last long, but why swells are capable of propagating long distances without substantial change in energy density. It is shown that breaking is many orders of magnitude more effective in dissipating wave energy than the molecular viscosity, if the significant slope is higher than 0.01. Limited observational data from satellite and laboratory are used to compare with the analytic results, and show good agreement.

  10. The significance of ultra-refracted surface gravity waves on sheltered coasts, with application to San Francisco Bay

    Science.gov (United States)

    Hanes, D.M.; Erikson, L.H.

    2013-01-01

    Ocean surface gravity waves propagating over shallow bathymetry undergo spatial modification of propagation direction and energy density, commonly due to refraction and shoaling. If the bathymetric variations are significant the waves can undergo changes in their direction of propagation (relative to deepwater) greater than 90° over relatively short spatial scales. We refer to this phenomenon as ultra-refraction. Ultra-refracted swell waves can have a powerful influence on coastal areas that otherwise appear to be sheltered from ocean waves. Through a numerical modeling investigation it is shown that San Francisco Bay, one of the earth's largest and most protected natural harbors, is vulnerable to ultra-refracted ocean waves, particularly southwest incident swell. The flux of wave energy into San Francisco Bay results from wave transformation due to the bathymetry and orientation of the large ebb tidal delta, and deep, narrow channel through the Golden Gate. For example, ultra-refracted swell waves play a critical role in the intermittent closure of the entrance to Crissy Field Marsh, a small restored tidal wetland located on the sheltered north-facing coast approximately 1.5 km east of the Golden Gate Bridge.

  11. Multiphase flow simulation with gravity effect in anisotropic porous media using multipoint flux approximation

    KAUST Repository

    Negara, Ardiansyah

    2015-03-04

    Numerical investigations of two-phase flows in anisotropic porous media have been conducted. In the flow model, the permeability has been considered as a full tensor and is implemented in the numerical scheme using the multipoint flux approximation within the framework of finite difference method. In addition, the experimenting pressure field approach is used to obtain the solution of the pressure field, which makes the matrix of coefficient of the global system easily constructed. A number of numerical experiments on the flow of two-phase system in two-dimensional porous medium domain are presented. In this work, the gravity is included in the model to capture the possible buoyancy-driven effects due to density differences between the two phases. Different anisotropy scenarios have been considered. From the numerical results, interesting patterns of the flow, pressure, and saturation fields emerge, which are significantly influenced by the anisotropy of the absolute permeability field. It is found that the two-phase system moves along the principal direction of anisotropy. Furthermore, the effects of anisotropy orientation on the flow rates and the cross flow index are also discussed in the paper.

  12. Multiphase flow simulation with gravity effect in anisotropic porous media using multipoint flux approximation

    KAUST Repository

    Negara, Ardiansyah; Salama, Amgad; Sun, Shuyu

    2015-01-01

    Numerical investigations of two-phase flows in anisotropic porous media have been conducted. In the flow model, the permeability has been considered as a full tensor and is implemented in the numerical scheme using the multipoint flux approximation within the framework of finite difference method. In addition, the experimenting pressure field approach is used to obtain the solution of the pressure field, which makes the matrix of coefficient of the global system easily constructed. A number of numerical experiments on the flow of two-phase system in two-dimensional porous medium domain are presented. In this work, the gravity is included in the model to capture the possible buoyancy-driven effects due to density differences between the two phases. Different anisotropy scenarios have been considered. From the numerical results, interesting patterns of the flow, pressure, and saturation fields emerge, which are significantly influenced by the anisotropy of the absolute permeability field. It is found that the two-phase system moves along the principal direction of anisotropy. Furthermore, the effects of anisotropy orientation on the flow rates and the cross flow index are also discussed in the paper.

  13. Compositional modeling of three-phase flow with gravity using higher-order finite element methods

    KAUST Repository

    Moortgat, Joachim

    2011-05-11

    A wide range of applications in subsurface flow involve water, a nonaqueous phase liquid (NAPL) or oil, and a gas phase, such as air or CO2. The numerical simulation of such processes is computationally challenging and requires accurate compositional modeling of three-phase flow in porous media. In this work, we simulate for the first time three-phase compositional flow using higher-order finite element methods. Gravity poses complications in modeling multiphase processes because it drives countercurrent flow among phases. To resolve this issue, we propose a new method for the upwinding of three-phase mobilities. Numerical examples, related to enhanced oil recovery and carbon sequestration, are presented to illustrate the capabilities of the proposed algorithm. We pay special attention to challenges associated with gravitational instabilities and take into account compressibility and various phase behavior effects, including swelling, viscosity changes, and vaporization. We find that the proposed higher-order method can capture sharp solution discontinuities, yielding accurate predictions of phase boundaries arising in computational three-phase flow. This work sets the stage for a broad extension of the higher-order methods for numerical simulation of three-phase flow for complex geometries and processes.

  14. Flow-Boiling Critical Heat Flux Experiments Performed in Reduced Gravity

    Science.gov (United States)

    Hasan, Mohammad M.; Mudawar, Issam

    2005-01-01

    Poor understanding of flow boiling in microgravity has recently emerged as a key obstacle to the development of many types of power generation and advanced life support systems intended for space exploration. The critical heat flux (CHF) is perhaps the most important thermal design parameter for boiling systems involving both heatflux-controlled devices and intense heat removal. Exceeding the CHF limit can lead to permanent damage, including physical burnout of the heat-dissipating device. The importance of the CHF limit creates an urgent need to develop predictive design tools to ensure both the safe and reliable operation of a two-phase thermal management system under the reduced-gravity (like that on the Moon and Mars) and microgravity environments of space. At present, very limited information is available on flow-boiling heat transfer and the CHF under these conditions.

  15. The influence of gravity on regional lung blood flow in humans: SPECT in the upright and head-down posture.

    Science.gov (United States)

    Ax, M; Sanchez-Crespo, A; Lindahl, S G E; Mure, M; Petersson, J

    2017-06-01

    Previous studies in humans have shown that gravity has little influence on the distribution of lung blood flow while changing posture from supine to prone. This study aimed to evaluate the maximal influence of posture by comparison of regional lung blood flow in the upright and head-down posture in 8 healthy volunteers, using a tilt table. Regional lung blood flow was marked by intravenous injection of macroaggregates of human albumin labeled with 99m Tc or 113m In, in the upright and head-down posture, respectively, during tidal breathing. Both radiotracers remain fixed in the lung after administration. The distribution of radioactivity was mapped using quantitative single photon emission computed tomography (SPECT) corrected for attenuation and scatter. All images were obtained supine during tidal breathing. A shift from upright to the head-down posture caused a clear redistribution of blood flow from basal to apical regions. We conclude that posture plays a role for the distribution of lung blood flow in upright humans, and that the influence of posture, and thereby gravity, is much greater in the upright and head-down posture than in horizontal postures. However, the results of the study demonstrate that lung structure is the main determinant of regional blood flow and gravity is a secondary contributor to the distribution of lung blood flow in the upright and head-down positions. NEW & NOTEWORTHY Using a dual-isotope quantitative SPECT method, we demonstrated that although a shift in posture redistributes blood flow in the direction of gravity, the results are also consistent with lung structure being a greater determinant of regional blood flow than gravity. To our knowledge, this is the first study to use modern imaging methods to quantify the shift in regional lung blood flow in humans at a change between the upright and head-down postures. Copyright © 2017 the American Physiological Society.

  16. Energy flow characteristics of vector X-Waves

    KAUST Repository

    Salem, Mohamed; Bagci, Hakan

    2011-01-01

    The vector form of X-Waves is obtained as a superposition of transverse electric and transverse magnetic polarized field components. It is shown that the signs of all components of the Poynting vector can be locally changed using carefully chosen complex amplitudes of the transverse electric and transverse magnetic polarization components. Negative energy flux density in the longitudinal direction can be observed in a bounded region around the centroid; in this region the local behavior of the wave field is similar to that of wave field with negative energy flow. This peculiar energy flux phenomenon is of essential importance for electromagnetic and optical traps and tweezers, where the location and momenta of microand nanoparticles are manipulated by changing the Poynting vector, and in detection of invisibility cloaks. © 2011 Optical Society of America.

  17. First OH Airglow Observation of Mesospheric Gravity Waves Over European Russia Region

    Science.gov (United States)

    Li, Qinzeng; Yusupov, Kamil; Akchurin, Adel; Yuan, Wei; Liu, Xiao; Xu, Jiyao

    2018-03-01

    For the first time, we perform a study of mesospheric gravity waves (GWs) for four different seasons of 1 year in the latitudinal band from 45°N to 75°N using an OH all-sky airglow imager over Kazan (55.8°N, 49.2°E), Russia, during the period of August 2015 to July 2016. Our observational study fills a huge airglow imaging observation gap in Europe and Russia region. In total, 125 GW events and 28 ripple events were determined by OH airglow images in 98 clear nights. The observed GWs showed a strong preference of propagation toward northeast in all seasons, which was significantly different from airglow imager observations at other latitudes that the propagation directions were seasonal dependent. The middle atmosphere wind field is used to explain the lack of low phase speed GWs since these GWs were falling into the blocking region due to the filtering effects. Deep tropospheric convections derived from the European Centre for Medium-Range Weather Forecasts reanalysis data are determined near Caucasus Mountains region, which suggests that the convections are the dominant source of the GWs in spring, summer, and autumn seasons. This finding extends our knowledge that convection might also be an important source of GWs in the higher latitudes. In winter the generation mechanism of the GWs are considered to be jet stream systems. In addition, the occurrence frequency of ripple is much lower than other stations. This study provides some constraints on the range of GW parameters in GW parameterization in general circulation models in Europe and Russia region.

  18. Latitudinal and seasonal variations of lower atmospheric inertial gravity wave energy revealed by US radiosonde data

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S.D.; Yi, F. [Wuhan Univ., Hubei (China). School of Electronic Information; Ministry of Education, Wuhan, Hubei (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan (China); Huang, C.M. [Wuhan Univ., Hubei (China). School of Electronic Information; Ministry of Education, Wuhan, Hubei (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan (China); Miami Univ., Oxford, OH (United States). Electrical and Computer Engineering Dept.; Zhou, Q. [Miami Univ., Oxford, OH (United States). Electrical and Computer Engineering Dept.

    2010-07-01

    The latitudinal and seasonal variations of gravity wave (GW) potential energy density (E{sub P}), kinetic energy density (E{sub K}), and total energy density (E{sub T}), i.e, the sum of potential and kinetic energy densities in the tropospheric (typically 2-10 km) and lower stratospheric (typically 18- 25 km) segments have been derived from 10 years (1998- 2007) of radiosonde observations over 92 United States stations in the Northern Hemisphere. The latitudinal variation of E{sub P} in the lower stratosphere is in good agreement with satellite observations. However, E{sub K} and E{sub T} in the lower stratosphere are different from satellite observations and the difference is believed to be linked with the latitudinal dependence of GW sources. Our analysis reveals that GW energy properties exhibit distinctive latitudinal and seasonal variations. The upward-propagating GW energy in the troposphere is larger than that in the lower stratosphere at low latitudes but the opposite holds true at high latitudes. The transition latitude, where the upward- propagating energies in the two altitude regions are the same, occurs at 35 N throughout the year. So striking differences between GW activity in the troposphere and lower stratosphere are not likely explained only by the background wind Doppler shifting due to strong tropospheric jets. Our analysis indicates that the region around tropopause, roughly from 10 km to 18 km, is an important source region, especially at latitudes below 35 N. Our studies strongly suggest that in order to fully understand the global GW activity in the lower atmosphere, the GW kinetic energy and its geographical and seasonal variations should be included, and more attention should be given to GWs in the troposphere and GW sources within the intermediate region, especially the upper troposphere. (orig.)

  19. Latitudinal and seasonal variations of lower atmospheric inertial gravity wave energy revealed by US radiosonde data

    Directory of Open Access Journals (Sweden)

    S. D. Zhang

    2010-05-01

    Full Text Available The latitudinal and seasonal variations of gravity wave (GW potential energy density (EP, kinetic energy density (EK, and total energy density (ET, i.e, the sum of potential and kinetic energy densities in the tropospheric (typically 2–10 km and lower stratospheric (typically 18–25 km segments have been derived from 10 years (1998–2007 of radiosonde observations over 92 United States stations in the Northern Hemisphere. The latitudinal variation of EP in the lower stratosphere is in good agreement with satellite observations. However, EK and ET in the lower stratosphere are different from satellite observations and the difference is believed to be linked with the latitudinal dependence of GW sources. Our analysis reveals that GW energy properties exhibit distinctive latitudinal and seasonal variations. The upward-propagating GW energy in the troposphere is larger than that in the lower stratosphere at low latitudes but the opposite holds true at high latitudes. The transition latitude, where the upward- propagating energies in the two altitude regions are the same, occurs at 35° N throughout the year. So striking differences between GW activity in the troposphere and lower stratosphere are not likely explained only by the background wind Doppler shifting due to strong tropospheric jets. Our analysis indicates that the region around tropopause, roughly from 10 km to 18 km, is an important source region, especially at latitudes below 35° N. Our studies strongly suggest that in order to fully understand the global GW activity in the lower atmosphere, the GW kinetic energy and its geographical and seasonal variations should be included, and more attention should be given to GWs in the troposphere and GW sources within the intermediate region, especially the upper troposphere.

  20. Variations of global gravity waves derived from 14 years of SABER temperature observations

    Science.gov (United States)

    Liu, Xiao; Yue, Jia; Xu, Jiyao; Garcia, Rolando R.; Russell, James M.; Mlynczak, Martin; Wu, Dong L.; Nakamura, Takuji

    2017-06-01

    The global gravity wave (GW) potential energy (PE) per unit mass is derived from SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) temperature profiles over the past 14 years (2002-2015). Since the SABER data cover longer than one solar cycle, multivariate linear regression is applied to calculate the trend (means linear trend from 2002 to 2015) of global GW PE and the responses of global GW PE to solar activity, to QBO (quasi-biennial oscillation) and to ENSO (El Niño-Southern Oscillation). We find a significant positive trend of GW PE at around 50°N during July from 2002 to 2015, in agreement with ground-based radar observations at a similar latitude but from 1990 to 2010. Both the monthly and the deseasonalized trends of GW PE are significant near 50°S. Specifically, the deseasonalized trend of GW PE has a positive peak of 12-15% per decade at 40°S-50°S and below 60 km, which suggests that eddy diffusion is increasing in some places. A significant positive trend of GW PE near 50°S could be due to the strengthening of the polar stratospheric jets, as documented from Modern Era Retrospective-analysis for Research and Applications wind data. The response of GW PE to solar activity is negative in the lower and middle latitudes. The response of GW PE to QBO (as indicated by 30 hPa zonal winds over the equator) is negative in the tropical upper stratosphere and extends to higher latitudes at higher altitudes. The response of GW PE to ENSO (as indicated by the Multivariate ENSO Index) is positive in the tropical upper stratosphere.

  1. Energy from sea wave thrust and flow of water

    International Nuclear Information System (INIS)

    Sarkar, S.R.

    1996-01-01

    The area adjacent to the tidal rivers, irrigational canal, drain and also the seashore may be energized harnessing the energy from the flow/wave thrust by simply converting it into unidirectional rotating force to drive the generator for power generation. The existing plants are big in size and also fixed in place. A plant which will be a small/portable type is described. 7 refs., figs

  2. The non-Gaussian joint probability density function of slope and elevation for a nonlinear gravity wave field. [in ocean surface

    Science.gov (United States)

    Huang, N. E.; Long, S. R.; Bliven, L. F.; Tung, C.-C.

    1984-01-01

    On the basis of the mapping method developed by Huang et al. (1983), an analytic expression for the non-Gaussian joint probability density function of slope and elevation for nonlinear gravity waves is derived. Various conditional and marginal density functions are also obtained through the joint density function. The analytic results are compared with a series of carefully controlled laboratory observations, and good agreement is noted. Furthermore, the laboratory wind wave field observations indicate that the capillary or capillary-gravity waves may not be the dominant components in determining the total roughness of the wave field. Thus, the analytic results, though derived specifically for the gravity waves, may have more general applications.

  3. Simulation and Observation of Acoustic-Gravity Waves in the Ionosphere

    Science.gov (United States)

    Kunitsyn, Viacheslav; Andreeva, Elena; Krysanov, Boris; Nesterov, Ivan

    Atmospheric and ionospheric perturbations associated with the acoustic-gravity waves (AGW) with typical frequencies of a few hertz -millihertz are considered. These events may be caused by the influence from space and atmosphere as well as by oscillations of the Earth surface and other near-surface phenomena. The surface sources include long-period oscillations of the Earth's surface, earthquakes, explosions, thermal heating, seisches and tsunami waves. The wavelike phenomena manifest themself as travelling disturbances of air (in the atmosphere) and of electron density (in the ionosphere). Travelling ionospheric disturbances (TIDs) are well detected by radio physical methods. AGW generation by near-surface sources is modeled by the numerical solution of the equation of geophysical fluid dynamics for different sources in two-dimensional non-linear dissipative compressible atmosphere. The numerical calculations are based on the FCT (Flux Corrected Transport) technique of the second order accuracy in time and space. Different scenarios of AGW generation are analyzed. The AGW caused by the surface sources within a few hertz-millihertz frequency band appear at the altitudes of middle atmosphere and ionosphere as the disturbances with typical scales from a few kilometers to several hundreds kilometers. Such structures can be successfully monitored by the methods of satellite radio tomography (RT). For the purposes of RT diagnostics of such disturbances, low-orbiting navigational satellites like Transit and Tsikada and high-orbiting navigation systems GPS/GLONASS are used. The results of numerical modeling of AGW generation by the surface sources are compared with the data of RT sounding. Also, generation of AGW by volumetric sources such as particle precipitation, rocket launching, heating by high-frequency radiation and other are considered. The obtained results proved the capability of RT methods of detecting and distinguishing between TIDs caused by AGW generated by

  4. A novel method for the extraction of local gravity wave parameters from gridded three-dimensional data: description, validation, and application

    Directory of Open Access Journals (Sweden)

    L. Schoon

    2018-05-01

    Full Text Available For the local diagnosis of wave properties, we develop, validate, and apply a novel method which is based on the Hilbert transform. It is called Unified Wave Diagnostics (UWaDi. It provides the wave amplitude and three-dimensional wave number at any grid point for gridded three-dimensional data. UWaDi is validated for a synthetic test case comprising two different wave packets. In comparison with other methods, the performance of UWaDi is very good with respect to wave properties and their location. For a first practical application of UWaDi, a minor sudden stratospheric warming on 30 January 2016 is chosen. Specifying the diagnostics for hydrostatic inertia–gravity waves in analyses from the European Centre for Medium-Range Weather Forecasts, we detect the local occurrence of gravity waves throughout the middle atmosphere. The local wave characteristics are discussed in terms of vertical propagation using the diagnosed local amplitudes and wave numbers. We also note some hints on local inertia–gravity wave generation by the stratospheric jet from the detection of shallow slow waves in the vicinity of its exit region.

  5. Gravity wave propagation through a large semidiurnal tide and instabilities in the mesosphere and lower thermosphere during the winter 2003 MaCWAVE rocket campaign

    Directory of Open Access Journals (Sweden)

    B. P. Williams

    2006-07-01

    Full Text Available The winter MaCWAVE (Mountain and convective waves ascending vertically rocket campaign took place in January 2003 at Esrange, Sweden and the ALOMAR observatory in Andenes, Norway. The campaign combined balloon, lidar, radar, and rocket measurements to produce full temperature and wind profiles from the ground to 105 km. This paper will investigate gravity wave propagation in the mesosphere and lower thermosphere using data from the Weber sodium lidar on 28–29 January 2003. A very large semidiurnal tide was present in the zonal wind above 80 km that grew to a 90 m/s amplitude at 100 km. The superposition of smaller-scale gravity waves and the tide caused small regions of possible convective or shear instabilities to form along the downward progressing phase fronts of the tide. The gravity waves had periods ranging from the Nyquist period of 30 min up to 4 h, vertical wavelengths ranging from 7 km to more than 20 km, and the frequency spectra had the expected –5/3 slope. The dominant gravity waves had long vertical wavelengths and experienced rapid downward phase progression. The gravity wave variance grew exponentially with height up from 86 to 94 km, consistent with the measured scale height, suggesting that the waves were not dissipated strongly by the tidal gradients and resulting unstable regions in this altitude range.

  6. influence of gravity

    Directory of Open Access Journals (Sweden)

    Animesh Mukherjee

    1991-01-01

    Full Text Available Based upon Biot's [1965] theory of initial stresses of hydrostatic nature produced by the effect of gravity, a study is made of surface waves in higher order visco-elastic media under the influence of gravity. The equation for the wave velocity of Stonely waves in the presence of viscous and gravitational effects is obtained. This is followed by particular cases of surface waves including Rayleigh waves and Love waves in the presence of viscous and gravity effects. In all cases the wave-velocity equations are found to be in perfect agreement with the corresponding classical results when the effects of gravity and viscosity are neglected.

  7. Long-term MST radar observations of vertical wave number spectra of gravity waves in the tropical troposphere over Gadanki (13.5° N, 79.2° E: comparison with model spectra

    Directory of Open Access Journals (Sweden)

    S. Vijaya Bhaskara Rao

    2008-06-01

    Full Text Available The potential utility of Mesosphere-Stratosphere-Troposphere (MST radar measurements of zonal, meridional and vertical winds for divulging the gravity wave vertical wave number spectra is discussed. The data collected during the years 1995–2004 are used to obtain the mean vertical wave number spectra of gravity wave kinetic energy in the tropical troposphere over Gadanki (13.5° N, 79.2° E. First, the climatology of 3-dimensional wind components is developed using ten years of radar observations, for the first time, over this latitude. This climatology brought out the salient features of background tropospheric winds over Gadanki. Further, using the second order polynomial fit as background, the day-to-day wind anomalies are estimated. These wind anomalies in the 4–14 km height regions are used to estimate the profiles of zonal, meridional and vertical kinetic energy per unit mass, which are then used to estimate the height profile of total kinetic energy. Finally, the height profiles of total kinetic energy are subjected to Fourier analysis to obtain the monthly mean vertical wave number spectra of gravity wave kinetic energy. The monthly mean vertical wave number spectra are then compared with a saturation spectrum predicted by gravity wave saturation theory. A slope of 5/3 is used for the model gravity wave spectrum estimation. In general, the agreement is good during all the months. However, it is noticed that the model spectrum overestimates the PSD at lower vertical wave numbers and underestimates it at higher vertical wave numbers, which is consistently observed during all the months. The observed discrepancies are attributed to the differences in the slopes of theoretical and observed gravity wave spectra. The slopes of the observed vertical wave number spectra are estimated and compared with the model spectrum slope, which are in good agreement. The estimated slopes of the observed monthly vertical wave number spectra are in the

  8. Rethinking wave-kinetic theory applied to zonal flows

    Science.gov (United States)

    Parker, Jeffrey

    2017-10-01

    Over the past two decades, a number of studies have employed a wave-kinetic theory to describe fluctuations interacting with zonal flows. Recent work has uncovered a defect in this wave-kinetic formulation: the system is dominated by the growth of (arbitrarily) small-scale zonal structures. Theoretical calculations of linear growth rates suggest, and nonlinear simulations confirm, that this system leads to the concentration of zonal flow energy in the smallest resolved scales, irrespective of the numerical resolution. This behavior results from the assumption that zonal flows are extremely long wavelength, leading to the neglect of key terms responsible for conservation of enstrophy. A corrected theory, CE2-GO, is presented; it is free of these errors yet preserves the intuitive phase-space mathematical structure. CE2-GO properly conserves enstrophy as well as energy, and yields accurate growth rates of zonal flow. Numerical simulations are shown to be well-behaved and not dependent on box size. The steady-state limit simplifies into an exact wave-kinetic form which offers the promise of deeper insight into the behavior of wavepackets. The CE2-GO theory takes its place in a hierarchy of models as the geometrical-optics reduction of the more complete cumulant-expansion statistical theory CE2. The new theory represents the minimal statistical description, enabling an intuitive phase-space formulation and an accurate description of turbulence-zonal flow dynamics. This work was supported by an NSF Graduate Research Fellowship, a US DOE Fusion Energy Sciences Fellowship, and US DOE Contract Nos. DE-AC52-07NA27344 and DE-AC02-09CH11466.

  9. Plasma flux and gravity waves in the midlatitude ionosphere during the solar eclipse of 20 May 2012

    Science.gov (United States)

    Chen, Gang; Wu, Chen; Huang, Xueqin; Zhao, Zhengyu; Zhong, Dingkun; Qi, Hao; Huang, Liang; Qiao, Lei; Wang, Jin

    2015-04-01

    The solar eclipse effects on the ionosphere are very complex. Except for the ionization decay due to the decrease of the photochemical process, the couplings of matter and energy between the ionosphere and the regions above and below will introduce much more disturbances. Five ionosondes in the Northeast Asia were used to record the midlatitude ionospheric responses to the solar eclipse of 20 May 2012. The latitude dependence of the eclipse lag was studied first. The foF2 response to the eclipse became slower with increased latitude. The response of the ionosphere at the different latitudes with the same eclipse obscuration differed from each other greatly. The plasma flux from the protonsphere was possibly produced by the rapid temperature drop in the lunar shadow to make up the ionization loss. The greater downward plasma flux was generated at higher latitude with larger dip angle and delayed the ionospheric response later. The waves in the foEs and the plasma frequency at the fixed height in the F layer are studied by the time period analytic method. The gravity waves of 43-51 min center period during and after the solar eclipse were found over Jeju and I-Cheon. The northward group velocity component of the gravity waves was estimated as ~108.7 m/s. The vertical group velocities between 100 and 150 km height over the two stations were calculated as ~5 and ~4.3 m/s upward respectively, indicating that the eclipse-induced gravity waves propagated from below the ionosphere.

  10. Satellite Detection of Orographic Gravity-wave Activity in the Winter Subtropical Stratosphere over Australia and Africa

    Science.gov (United States)

    Eckermann, S. D.; Wu, D. L.

    2012-01-01

    Orographic gravity-wave (OGW) parameterizations in models produce waves over subtropical mountain ranges in Australia and Africa that propagate into the stratosphere during austral winter and deposit momentum, affecting weather and climate. Satellite sensors have measured stratospheric GWs for over a decade, yet find no evidence of these waves. So are parameterizations failing here? Here we argue that the short wavelengths of subtropical OGWs place them near or below the detection limits of satellite sensors. To test this hypothesis, we reanalyze nine years of stratospheric radiances from the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite during austral winter, applying new averaging techniques to maximize signal-to-noise and improve thresholds for OGW detection. Deep climatological enhancements in stratospheric OGW variance over specific mountain ranges in Australia and southern Africa are revealed for the first time, which exhibit temporal and vertical variations consistent with predicted OGW responses to varying background winds.

  11. Estimates of Lagrangian particle transport by wave groups: forward transport by Stokes drift and backward transport by the return flow

    Science.gov (United States)

    van den Bremer, Ton S.; Taylor, Paul H.

    2014-11-01

    Although the literature has examined Stokes drift, the net Lagrangian transport by particles due to of surface gravity waves, in great detail, the motion of fluid particles transported by surface gravity wave groups has received considerably less attention. In practice nevertheless, the wave field on the open sea often has a group-like structure. The motion of particles is different, as particles at sufficient depth are transported backwards by the Eulerian return current that was first described by Longuet-Higgins & Stewart (1962) and forms an inseparable counterpart of Stokes drift for wave groups ensuring the (irrotational) mass balance holds. We use WKB theory to study the variation of the Lagrangian transport by the return current with depth distinguishing two-dimensional seas, three-dimensional seas, infinite depth and finite depth. We then provide dimensional estimates of the net horizontal Lagrangian transport by the Stokes drift on the one hand and the return flow on the other hand for realistic sea states in all four cases. Finally we propose a simple scaling relationship for the transition depth: the depth above which Lagrangian particles are transported forwards by the Stokes drift and below which such particles are transported backwards by the return current.

  12. Accuracy and Precision of Plane Wave Vector Flow Imaging for Laminar and Complex Flow In Vivo

    DEFF Research Database (Denmark)

    Jensen, Jonas; Traberg, Marie Sand; Villagómez Hoyos, Carlos Armando

    2017-01-01

    In this study, a comparison between velocity fields for a plane wave 2-D vector flow imaging (VFI) method and a computational fluid dynamics (CFD) simulation is made. VFI estimates are obtained from the scan of a flow phantom, which mimics the complex flow conditions in the carotid artery....... Furthermore, the precision of the VFI method is investigated under laminar and complex flow conditions in vivo. The carotid bifurcation of a healthy volunteer was scanned using both fast plane wave ultrasound and magnetic resonance imaging (MRI). The acquired MRI geometry of the bifurcation was used...... difference within 15 %, however, it was 23 % in the external branch. For the in vivo scan, the precision in terms of mean standard deviation (SD) of estimates aligned to the cardiac cycle was highest in the center of the common carotid artery (SD 4.7◦ for angles) and lowest in the external branch and close...

  13. Flow equation of quantum Einstein gravity in a higher-derivative truncation

    International Nuclear Information System (INIS)

    Lauscher, O.; Reuter, M.

    2002-01-01

    Motivated by recent evidence indicating that quantum Einstein gravity (QEG) might be nonperturbatively renormalizable, the exact renormalization group equation of QEG is evaluated in a truncation of theory space which generalizes the Einstein-Hilbert truncation by the inclusion of a higher-derivative term (R 2 ). The beta functions describing the renormalization group flow of the cosmological constant, Newton's constant, and the R 2 coupling are computed explicitly. The fixed point properties of the 3-dimensional flow are investigated, and they are confronted with those of the 2-dimensional Einstein-Hilbert flow. The non-Gaussian fixed point predicted by the latter is found to generalize to a fixed point on the enlarged theory space. In order to test the reliability of the R 2 truncation near this fixed point we analyze the residual scheme dependence of various universal quantities; it turns out to be very weak. The two truncations are compared in detail, and their numerical predictions are found to agree with a surprisingly high precision. Because of the consistency of the results it appears increasingly unlikely that the non-Gaussian fixed point is an artifact of the truncation. If it is present in the exact theory QEG is probably nonperturbatively renormalizable and ''asymptotically safe.'' We discuss how the conformal factor problem of Euclidean gravity manifests itself in the exact renormalization group approach and show that, in the R 2 truncation, the investigation of the fixed point is not afflicted with this problem. Also the Gaussian fixed point of the Einstein-Hilbert truncation is analyzed; it turns out that it does not generalize to a corresponding fixed point on the enlarged theory space

  14. Acoustic-gravity waves generated by atmospheric and near-surface sources

    Science.gov (United States)

    Kunitsyn, Viacheslav E.; Kholodov, Alexander S.; Krysanov, Boris Yu.; Andreeva, Elena S.; Nesterov, Ivan A.; Vorontsov, Artem M.

    2013-04-01

    Numerical simulation of the acoustic-gravity waves (AGW) generated by long-period oscillations of the Earth's (oceanic) surface, earthquakes, explosions, thermal heating, seiches, and tsunami is carried out. Wavelike disturbances are quite frequent phenomena in the atmosphere and ionosphere. These events can be caused by the impacts from space and atmosphere, by oscillations of the Earth'as surface and other near-surface events. These wavelike phenomena in the atmosphere and ionosphere appear as the alternating areas of enhanced and depleted density (in the atmosphere) or electron concentration (in the ionosphere). In the paper, AGW with typical frequencies of a few hertz - millihertz are analyzed. AGW are often observed after the atmospheric perturbations, during the earthquakes, and some time (a few days to hours) in advance of the earthquakes. Numerical simulation of the generation of AGW by long-period oscillations of the Earth's and oceanic surface, earthquakes, explosions, thermal heating, seiches, and tsunami is carried out. The AGW generated by the near-surface phenomena within a few hertz-millihertz frequency range build up at the mid-atmospheric and ionospheric altitudes, where they assume their typical spatial scales of the order of a few hundred kilometers. Oscillations of the ionospheric plasma within a few hertz-millihertz frequency range generate electromagnetic waves with corresponding frequencies as well as travelling ionospheric irregularities (TIDs). Such structures can be successfully monitored using satellite radio tomography (RT) techniques. For the purposes of RT diagnostics, 150/400 MHz transmissions from low-orbiting navigational satellites flying in polar orbits at the altitudes of about 1000 km as well as 1.2-1.5 GHz signals form high-orbiting (orbital altitudes about 20000 km) navigation systems like GPS/GLONASS are used. The results of experimental studies on generation of wavelike disturbances by particle precipitation are presented

  15. Oblique shock waves in granular flows over bluff bodies

    Directory of Open Access Journals (Sweden)

    Gopan Nandu

    2017-01-01

    Full Text Available Granular flows around an object have been the focus of numerous analytical, experimental and simulation studies. The structure and nature of the oblique shock wave developed when a quasi-two dimensional flow of spherical granular particles streams past an immersed, fixed cylindrical obstacle forms the focus of this study. The binary granular mixture, consisting of particles of the same diameter but different material properties, is investigated by using a modified LIGGGHTS package as the simulation engine. Variations in the solid fraction and granular temperature within the resulting flow are studied. The Mach number is calculated and is used to distinguish between the subsonic and the supersonic regions of the bow shock.

  16. Surface gravity waves and their acoustic signatures, 1-30 Hz, on the mid-Pacific sea floor.

    Science.gov (United States)

    Farrell, W E; Munk, Walter

    2013-10-01

    In 1999, Duennebier et al. deployed a hydrophone and geophone below the conjugate depth in the abyssal Pacific, midway between Hawaii and California. Real time data were transmitted for 3 yr over an abandoned ATT cable. These data have been analyzed in the frequency band 1 to 30 Hz. Between 1 and 6 Hz, the bottom data are interpreted as acoustic radiation from surface gravity waves, an extension to higher frequencies of a non-linear mechanism proposed by Longuet-Higgins in 1950 to explain microseisms. The inferred surface wave spectrum for wave lengths between 6 m and 17 cm is saturated (wind-independent) and roughly consistent with the traditional Phillips κ(-4) wave number spectrum. Shorter ocean waves have a strong wind dependence and a less steep wave number dependence. Similar features are found in the bottom record between 6 and 30 Hz. But this leads to an enigma: The derived surface spectrum inferred from the Longuet-Higgins mechanism with conventional assumptions for the dispersion relation is associated with mean square slopes that greatly exceed those derived from glitter. Regardless of the generation mechanism, the measured bottom intensities between 10 and 30 Hz are well below minimum noise standards reported in the literature.

  17. Initial results from SKiYMET meteor radar at Thumba (8.5°N, 77°E): 2. Gravity wave observations in the MLT region

    Science.gov (United States)

    Kumar, Karanam Kishore; Antonita, T. Maria; Shelbi, S. T.

    2007-12-01

    In the present communication, allSKy interferometric METeor (SKiYMET) radar observations of gravity wave activity in the mesosphere lower thermosphere (MLT) region over Thumba (8.5°N, 77°E) are presented. The present meteor radar system provides hourly zonal and meridional winds in the MLT region, which can be readily used for studying the tides, planetary waves, gravity waves of periods 2-6 hours, and other long period oscillations in this region. However, these hourly winds are not sufficient for studying short period gravity waves having periods less than an hour, which demand high temporal resolution measurements. Even though the winds are estimated on an hourly basis, information such as zenith angle, azimuth angle, and radial velocity of each detected meteor are archived. Using these details of the meteor, an algorithm is developed to obtain the 15-min temporal resolution wind data. The output of the algorithm is compared with hourly wind data, and it showed a good agreement during the high meteor shower periods. Most of the times high meteor counts are observed during late night and early morning hours (local) over this latitude. Continuous wind measurements during the high meteor shower periods are used for studying the gravity wave activity in the MLT region. As the wave activity is intermittent and nonstationary, wavelet analysis has been used for delineating the wave features. The results showed the upward propagating intermittent gravity waves with periods 1-2 and 4-5 hours. The new aspect of the present communication is the usage of meteor radar for gravity wave studies for the first time over this latitude and studying their seasonal variability.

  18. Design and testing of a unique randomized gravity, continuous flow bioreactor

    Science.gov (United States)

    Lassiter, Carroll B.

    1993-01-01

    A rotating, null gravity simulator, or Couette bioreactor was successfully used for the culture of mammalian cells in a simulated microgravity environment. Two limited studies using Lipomyces starkeyi and Streptomyces clavuligerus were also conducted under conditions of simulated weightlessness. Although these studies with microorganisms showed promising preliminary results, oxygen limitations presented significant limitations in studying the biochemical and cultural characteristics of these cell types. Microbial cell systems such as bacteria and yeast promise significant potential as investigative models to study the effects of microgravity on membrane transport, as well as substrate induction of inactive enzyme systems. Additionally, the smaller size of the microorganisms should further reduce the gravity induced oscillatory particle motion and thereby improve the microgravity simulation on earth. Focus is on the unique conceptual design, and subsequent development of a rotating bioreactor that is compatible with the culture and investigation of microgravity effects on microbial systems. The new reactor design will allow testing of highly aerobic cell types under simulated microgravity conditions. The described reactor affords a mechanism for investigating the long term effects of reduced gravity on cellular respiration, membrane transfer, ion exchange, and substrate conversions. It offers the capability of dynamically altering nutrients, oxygenation, pH, carbon dioxide, and substrate concentration without disturbing the microgravity simulation, or Couette flow, of the reactor. All progeny of the original cell inoculum may be acclimated to the simulated microgravity in the absence of a substrate or nutrient. The reactor has the promise of allowing scientists to probe the long term effects of weightlessness on cell interactions in plants, bacteria, yeast, and fungi. The reactor is designed to have a flow field growth chamber with uniform shear stress, yet transfer

  19. Flow Control in Wells Turbines for Harnessing Maximum Wave Power

    Science.gov (United States)

    Garrido, Aitor J.; Garrido, Izaskun; Otaola, Erlantz; Maseda, Javier

    2018-01-01

    Oceans, and particularly waves, offer a huge potential for energy harnessing all over the world. Nevertheless, the performance of current energy converters does not yet allow us to use the wave energy efficiently. However, new control techniques can improve the efficiency of energy converters. In this sense, the plant sensors play a key role within the control scheme, as necessary tools for parameter measuring and monitoring that are then used as control input variables to the feedback loop. Therefore, the aim of this work is to manage the rotational speed control loop in order to optimize the output power. With the help of outward looking sensors, a Maximum Power Point Tracking (MPPT) technique is employed to maximize the system efficiency. Then, the control decisions are based on the pressure drop measured by pressure sensors located along the turbine. A complete wave-to-wire model is developed so as to validate the performance of the proposed control method. For this purpose, a novel sensor-based flow controller is implemented based on the different measured signals. Thus, the performance of the proposed controller has been analyzed and compared with a case of uncontrolled plant. The simulations demonstrate that the flow control-based MPPT strategy is able to increase the output power, and they confirm both the viability and goodness. PMID:29439408

  20. Flow Control in Wells Turbines for Harnessing Maximum Wave Power.

    Science.gov (United States)

    Lekube, Jon; Garrido, Aitor J; Garrido, Izaskun; Otaola, Erlantz; Maseda, Javier

    2018-02-10

    Oceans, and particularly waves, offer a huge potential for energy harnessing all over the world. Nevertheless, the performance of current energy converters does not yet allow us to use the wave energy efficiently. However, new control techniques can improve the efficiency of energy converters. In this sense, the plant sensors play a key role within the control scheme, as necessary tools for parameter measuring and monitoring that are then used as control input variables to the feedback loop. Therefore, the aim of this work is to manage the rotational speed control loop in order to optimize the output power. With the help of outward looking sensors, a Maximum Power Point Tracking (MPPT) technique is employed to maximize the system efficiency. Then, the control decisions are based on the pressure drop measured by pressure sensors located along the turbine. A complete wave-to-wire model is developed so as to validate the performance of the proposed control method. For this purpose, a novel sensor-based flow controller is implemented based on the different measured signals. Thus, the performance of the proposed controller has been analyzed and compared with a case of uncontrolled plant. The simulations demonstrate that the flow control-based MPPT strategy is able to increase the output power, and they confirm both the viability and goodness.

  1. The Influence of Waves on the Near-Wake of an Axial-Flow Marine Hydrokinetic Turbine

    Science.gov (United States)

    Lust, Ethan; Luznik, Luksa; Flack, Karen

    2017-11-01

    Flow field results are presented for the near-wake of an axial-flow hydrokinetic turbine in the presence of surface gravity waves. The turbine is a 1/25 scale, 0.8 m diameter, two bladed turbine based on the U.S. Department of Energy's Reference Model 1 tidal current turbine. Measurements were obtained in the large towing tank facility at the U.S. Naval Academy with the turbine towed at a constant carriage speed and a tip speed ratio selected to provide maximum power. The turbine has been shown to be nearly scale independent for these conditions. Velocity measurements were obtained using an in-house designed and manufactured, submersible, planar particle image velocimetry (PIV) system at streamwise distances of up to two diameters downstream of the rotor plane. Phase averaged results for steady and unsteady conditions are presented for comparison showing further expansion of the wake in the presence of waves as compared to the quiescent case. The impact of waves on turbine tip vortex characteristics is also examined showing variation in core radius, swirl velocity, and circulation with wave phase. Some aspects of the highly coherent wake observed in the steady case are recognized in the unsteady wake, however, the unsteady velocities imposed by the waves, particularly the vertical velocity component, appears to convect tip vortices into the wake, potentially enhancing energy transport and accelerating the re-energization process.

  2. A numerical model for ocean ultra-low frequency noise: wave-generated acoustic-gravity and Rayleigh modes.

    Science.gov (United States)

    Ardhuin, Fabrice; Lavanant, Thibaut; Obrebski, Mathias; Marié, Louis; Royer, Jean-Yves; d'Eu, Jean-François; Howe, Bruce M; Lukas, Roger; Aucan, Jerome

    2013-10-01

    The generation of ultra-low frequency acoustic noise (0.1 to 1 Hz) by the nonlinear interaction of ocean surface gravity waves is well established. More controversial are the quantitative theories that attempt to predict the recorded noise levels and their variability. Here a single theoretical framework is used to predict the noise level associated with propagating pseudo-Rayleigh modes and evanescent acoustic-gravity modes. The latter are dominant only within 200 m from the sea surface, in shallow or deep water. At depths larger than 500 m, the comparison of a numerical noise model with hydrophone records from two open-ocean sites near Hawaii and the Kerguelen islands reveal: (a) Deep ocean acoustic noise at frequencies 0.1 to 1 Hz is consistent with the Rayleigh wave theory, in which the presence of the ocean bottom amplifies the noise by 10 to 20 dB; (b) in agreement with previous results, the local maxima in the noise spectrum support the theoretical prediction for the vertical structure of acoustic modes; and (c) noise level and variability are well predicted for frequencies up to 0.4 Hz. Above 0.6 Hz, the model results are less accurate, probably due to the poor estimation of the directional properties of wind-waves with frequencies higher than 0.3 Hz.

  3. Extracting gravity wave parameters during the September 2002 Southern Hemisphere major sudden stratospheric warming using a SANAE imaging riometer

    Energy Technology Data Exchange (ETDEWEB)

    Mbatha, N. [South African National Space Agency, Hermanus (South Africa). Space Science; KwaZulu-Natal Univ., Durban (South Africa). School of Chemistry and Physics; Sivakumar, V. [KwaZulu-Natal Univ., Durban (South Africa). School of Chemistry and Physics; Bencherif, H. [La Reunion Univ. UMR 8105 CNRS, Saint-Denis (France). Lab. de l' Atmosphere et des Cyclones; Malinga, S. [South African National Space Agency, Hermanus (South Africa). Space Science

    2013-11-01

    Using absorption data measured by imaging riometer for ionospheric studies (IRIS) located at the South Africa National Antarctic Expedition (SANAE), Antarctica (72 S, 3 W), we extracted the parameters of gravity waves (GW) of periods between 40 and 50 min during late winter/ spring of the year 2002, a period of the unprecedented major sudden stratospheric warming (SSW) in the Southern Hemisphere middle atmosphere. During this period, an unprecedented substantial increase of temperature by about 25-30K throughout the stratosphere was observed. During the period of the occurrence of the major stratospheric warming, there was a reduction of both the GW horizontal phase speeds and the horizontal wavelengths at 90 km. The GW phase speeds and horizontal wavelengths were observed to reach minimum values of about 7ms{sup -1} and 19 km, respectively, while during the quiet period the average value of the phase speed and horizontal wavelength was approximately 23ms{sup -1} and 62 km, respectively. The observed event is discussed in terms of momentum flux and also a potential interaction of gravity waves, planetary waves and mean circulation.

  4. Acoustic-gravity nonlinear structures

    Directory of Open Access Journals (Sweden)

    D. Jovanović

    2002-01-01

    Full Text Available A catalogue of nonlinear vortex structures associated with acoustic-gravity perturbations in the Earth's atmosphere is presented. Besides the previously known Kelvin-Stewart cat's eyes, dipolar and tripolar structures, new solutions having the form of a row of counter-rotating vortices, and several weakly two-dimensional vortex chains are given. The existence conditions for these nonlinear structures are discussed with respect to the presence of inhomogeneities of the shear flows. The mode-coupling mechanism for the nonlinear generation of shear flows in the presence of linearly unstable acoustic-gravity waves, possibly also leading to intermittency and chaos, is presented.

  5. 22 July 2009 total solar eclipse induced gravity waves in ionosphere as inferred from GPS observations over EIA

    Science.gov (United States)

    Kumar, K. Vijay; Maurya, Ajeet K.; Kumar, Sanjay; Singh, Rajesh

    2016-11-01

    In the present contribution we investigate the variation in the Global Positioning System (GPS) derived ionospheric Total Electron Content (TEC) over Equatorial Ionization Anomaly (EIA) region on the rare occasional astronomical phenomenon of total solar eclipse of 22 July 2009. The aim is to study and identify the wave like structure enumerated due to solar eclipse induced gravity waves in the F-region ionosphere altitude. The work is aimed to understand features of horizontal and vertical variation of atmospheric gravity waves (AGWs) properties over the Equatorial Ionization Anomaly (EIA) region in Indian low latitude region. The ionospheric observations is from the site of Allahabad (lat 25.4° N; lon. 81.9° E; dip 38.6° N) located at the fringe of eclipse totality path. The estimated vertical electron density profile from FORMOSAT-3/COSMIC GPS-RO satellite, considering all the satellite line of sight around the time of eclipse totality shows maximum depletion of 43%. The fast fourier transform and wavelet transform of GPS DTEC data from Allahabad station (Allahabad: lat 25.4 N; lon. 81.9 E) shows the presence of periodic waves of ∼20 to 45 min and ∼70 to 90 min period at F-region altitude. The shorter period correspond to the sunrise time morning terminator and longer period can be associated with solar eclipse generated AGWs. The most important result obtained is that our results along with previous result for wave like signatures in D-region ionosphere from Allahabad station show that AGWs generated by sunrise time terminator have similarity in the D and F region of the ionosphere but solar eclipse induced AGWs show higher period in the F-region compared to D-region ionosphere.

  6. Gravity assisted recovery of liquid xenon at large mass flow rates

    Science.gov (United States)

    Virone, L.; Acounis, S.; Beaupère, N.; Beney, J.-L.; Bert, J.; Bouvier, S.; Briend, P.; Butterworth, J.; Carlier, T.; Chérel, M.; Crespi, P.; Cussonneau, J.-P.; Diglio, S.; Manzano, L. Gallego; Giovagnoli, D.; Gossiaux, P.-B.; Kraeber-Bodéré, F.; Ray, P. Le; Lefèvre, F.; Marty, P.; Masbou, J.; Morteau, E.; Picard, G.; Roy, D.; Staempflin, M.; Stutzmann, J.-S.; Visvikis, D.; Xing, Y.; Zhu, Y.; Thers, D.

    2018-06-01

    We report on a liquid xenon gravity assisted recovery method for nuclear medical imaging applications. The experimental setup consists of an elevated detector enclosed in a cryostat connected to a storage tank called ReStoX. Both elements are part of XEMIS2 (XEnon Medical Imaging System): an innovative medical imaging facility for pre-clinical research that uses pure liquid xenon as detection medium. Tests based on liquid xenon transfer from the detector to ReStoX have been successfully performed showing that an unprecedented mass flow rate close to 1 ton per hour can be reached. This promising achievement as well as future areas of improvement will be discussed in this paper.

  7. VLP seismicity from resonant modes of acoustic-gravity waves in a conduit-crack system filled with multiphase magma

    Science.gov (United States)

    Liang, C.; Prochnow, B. N.; OReilly, O. J.; Dunham, E. M.; Karlstrom, L.

    2016-12-01

    Oscillation of magma in volcanic conduits connected to cracks (dikes and sills) has been suggested as an explanation for very long period (VLP) seismic signals recorded at active basaltic volcanoes such as. Kilauea, Hawaii, and Erebus, Antarctica. We investigate the VLP seismicity using a linearized model for waves in and associated eigenmodes of a coupled conduit-crack system filled with multiphase magma, an extension of the Karlstrom and Dunham (2016) model for acoustic-gravity waves in volcanic conduits. We find that the long period surface displacement (as recorded on broadband seismometers) is dominated by opening/closing of the crack rather than the deformation of the conduit conduit walls. While the fundamental eigenmode is sensitive to the fluid properties and the geometry of the magma plumbing system, a closer scrutiny of various resonant modes reveals that the surface displacement is often more sensitive to higher modes. Here we present a systematic analysis of various long period acoustic-gravity wave resonant modes of a coupled conduit-crack system that the surface displacement is most sensitive to. We extend our previous work on a quasi-one-dimensional conduit model with inviscid magma to a more general axisymmetric conduit model that properly accounts for viscous boundary layers near the conduit walls, based on the numerical method developed by Prochnow et al. (submitted to Computers and Fluids, 2016). The surface displacement is dominated by either the fundamental or higher eigenmodes, depending on magma properties and the geometry of conduit and crack. An examination of the energetics of these modes reveals the complex interplay of different restoring forces (magma compressibility in the conduit, gravity, and elasticity of the crack) driving the VLP oscillations. Both nonequilibrium bubble growth and resorption and viscosity contribute to the damping of VLP signals. Our models thus provide a means to infer properties of open-vent basaltic volcanoes

  8. Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign – Part I: Observations with collocated radars

    Directory of Open Access Journals (Sweden)

    P. Hoffmann

    2006-11-01

    Full Text Available During the {MaCWAVE} campaign, combined rocket, radiosonde and ground-based measurements have been performed at the Norwegian Andøya Rocket Range (ARR near Andenes and the Swedish Rocket Range (ESRANGE near Kiruna in January 2003 to study gravity waves in the vicinity of the Scandinavian mountain ridge. The investigations presented here are mainly based on the evaluation of continuous radar measurements with the ALWIN VHF radar in the upper troposphere/ lower stratosphere at Andenes (69.3° N, 16.0° E and the ESRAD VHF radar near Kiruna (67.9° N, 21.9° E. Both radars are separated by about 260 km. Based on wavelet transformations of both data sets, the strongest activity of inertia gravity waves in the upper troposphere has been detected during the first period from 24–26 January 2003 with dominant vertical wavelengths of about 4–5 km as well as with dominant observed periods of about 13–14 h for the altitude range between 5 and 8 km under the additional influence of mountain waves. The results show the appearance of dominating inertia gravity waves with characteristic horizontal wavelengths of ~200 km moving in the opposite direction than the mean background wind. The results show the appearance of dominating inertia gravity waves with intrinsic periods in the order of ~5 h and with horizontal wavelengths of 200 km, moving in the opposite direction than the mean background wind. From the derived downward energy propagation it is supposed, that these waves are likely generated by a jet streak in the upper troposphere. The parameters of the jet-induced gravity waves have been estimated at both sites separately. The identified gravity waves are coherent at both locations and show higher amplitudes on the east-side of the Scandinavian mountain ridge, as expected by the influence of mountains.

  9. Biological nitrogen and carbon removal in a gravity flow biomass concentrator reactor for municipal sewage treatment.

    Science.gov (United States)

    Scott, Daniel; Hidaka, Taira; Campo, Pablo; Kleiner, Eric; Suidan, Makram T; Venosa, Albert D

    2013-01-01

    A novel membrane system, the Biomass Concentrator Reactor (BCR), was evaluated as an alternative technology for the treatment of municipal wastewater. Because the BCR is equipped with a membrane whose average poresize is 20 μm (18-28 μm), the reactor requires low-pressure differential to operate (gravity). The effectiveness of this system was evaluated for the removal of carbon and nitrogen using two identical BCRs, identified as conventional and hybrid, that were operated in parallel. The conventional reactor was operated under full aerobic conditions (i.e., organic carbon and ammonia oxidation), while the hybrid reactor incorporated an anoxic zone for nitrate reduction as well as an aerobic zone for organic carbon and ammonia oxidation. Both reactors were fed synthetic wastewater at a flow rate of 71 L d(-1), which resulted in a hydraulic retention time of 9 h. In the case of the hybrid reactor, the recycle flow from the aerobic zone to the anoxic zone was twice the feed flow rate. Reactor performance was evaluated under two solids retention times (6 and 15 d). Under these conditions, the BCRs achieved nearly 100% mixed liquor solids separation with a hydraulic head differential of less than 2.5 cm. The COD removal efficiency was over 90%. Essentially complete nitrification was achieved in both systems, and nitrogen removal in the hybrid reactor was close to the expected value (67%). Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. A solution of nonlinear equation for the gravity wave spectra from Adomian decomposition method: a first approach

    Directory of Open Access Journals (Sweden)

    Antonio Gledson Goulart

    2013-12-01

    Full Text Available In this paper, the equation for the gravity wave spectra in mean atmosphere is analytically solved without linearization by the Adomian decomposition method. As a consequence, the nonlinear nature of problem is preserved and the errors found in the results are only due to the parameterization. The results, with the parameterization applied in the simulations, indicate that the linear solution of the equation is a good approximation only for heights shorter than ten kilometers, because the linearization the equation leads to a solution that does not correctly describe the kinetic energy spectra.

  11. Plastic Models Designed to Produce Large Height-to-Length Ratio Steady-State Planar and Axisymmetric (Radial) Viscous Liquid Laminar Flow Gravity Currents

    Science.gov (United States)

    Blanck, Harvey F.

    2012-01-01

    Naturally occurring gravity currents include events such as air flowing through an open front door, a volcanic eruption's pyroclastic flow down a mountainside, and the spread of the Bhopal disaster's methyl isocyanate gas. Gravity currents typically have a small height-to-distance ratio. Plastic models were designed and constructed with a…

  12. Nonlinear damping of drift waves by strong flow curvature

    International Nuclear Information System (INIS)

    Sidikman, K.L.; Carreras, B.A.; Garcia, L.; Diamond, P.H.

    1993-01-01

    A single-equation model has been used to study the effect of a fixed poloidal flow (V 0 ) on turbulent drift waves. The electron dynamics come from a laminar kinetic equation in the dissipative trapped-electron regime. In the past, the authors have assumed that the mode frequency is close to the drift-wave frequency. Trapped-electron density fluctuations are then related to potential fluctuations by an open-quotes iδclose quotes term. Flow shear (V 0 ') and curvature (V 0 double-prime) both have a stabilizing effect on linear modes for this open-quotes iδclose quotes model. However, in the nonlinear regime, single-helicity effects inhibit the flow damping. Neither V 0 ' nor V 0 double-prime produces a nonlinear damping effect. The above assumption on the frequency can be relaxed by including the electron time-response in the linear part of the evolution. In this time-dependent model, instability drive due to trapped electrons is reduced when mode frequency is greater than drift-wave frequency. Since V 0 double-prime produces such a frequency shift, its linear effect is enhanced. There is also nonlinear damping, since single-helicity effects do not eliminate the shift. Renormalized theory for this model predicts nonlinear stability for sufficiently large curvature. Single-helicity calculations have already shown nonlinear damping, and this strong V 0 double-prime regime is being explored. In the theory, the Gaussian shape of the nonlinear diffusivity is expanded to obtain a quadratic potential. The implications of this assumption will be tested by solving the full renormalized equation using a shooting method

  13. Propagation of short-period gravity waves at high-latitudes during the MaCWAVE winter campaign

    Directory of Open Access Journals (Sweden)

    K. Nielsen

    2006-07-01

    Full Text Available As part of the MaCWAVE (Mountain and Convective Waves Ascending Vertically winter campaign an all-sky monochromatic CCD imager has been used to investigate the properties of short-period mesospheric gravity waves at high northern latitudes. Sequential measurements of several nightglow emissions were made from Esrange, Sweden, during a limited period from 27–31 January 2003. Coincident wind measurements over the altitude range (~80–100 km using two meteor radar systems located at Esrange and Andenes have been used to perform a novel investigation of the intrinsic properties of five distinct wave events observed during this period. Additional lidar and MSIS model temperature data have been used to investigate their nature (i.e. freely propagating or ducted. Four of these extensive wave events were found to be freely propagating with potential source regions to the north of Scandinavia. No evidence was found for strong orographic forcing by short-period waves in the airglow emission layers. The fifth event was most unusual exhibiting an extensive, but much smaller and variable wavelength pattern that appeared to be embedded in the background wind field. Coincident wind measurements indicated the presence of a strong shear suggesting this event was probably due to a large-scale Kelvin-Helmholtz instability.

  14. Shock wave of vapor-liquid two-phase flow

    Institute of Scientific and Technical Information of China (English)

    Liangju ZHAO; Fei WANG; Hong GAO; Jingwen TANG; Yuexiang YUAN

    2008-01-01

    The shock wave of vapor-liquid two-phase flow in a pressure-gain steam injector is studied by build-ing a mathematic model and making calculations. The results show that after the shock, the vapor is nearly com-pletely condensed. The upstream Mach number and the volume ratio of vapor have a great effect on the shock. The pressure and Mach number of two-phase shock con-form to the shock of ideal gas. The analysis of available energy shows that the shock is an irreversible process with entropy increase.

  15. Analysis of the fluid flow and heat transfer in a thin liquid film in the presence and absence of gravity

    Science.gov (United States)

    Rahman, M. M.; Hankey, W. L.; Faghri, A.

    1991-01-01

    The hydrodynamic and thermal behavior of a thin liquid film flowing over a solid horizontal surface is analyzed for both plane and radially spreading flows. The situations where the gravitational force is completely absent and where it is significant are analyzed separately and their practical relevance to a micro-gravity environment is discussed. In the presence of gravity, in addition to Reynolds number, the Froude number of the film is found to be an important parameter that determines the supercritical and subcritical flow regimes and any associated hydraulic jump. A closed-form solution is possible under some flow situations, whereas others require numerical integration of ordinary differential equations. The approximate analytical results are found to compare well with the available two-dimensional numerical solutions.

  16. Perturbed black holes in Einstein-dilaton-Gauss-Bonnet gravity: stability, ringdown, and gravitational-wave emission

    CERN Document Server

    Blázquez-Salcedo, Jose Luis

    2016-01-01

    Gravitational waves emitted by distorted black holes---such as those arising from the coalescence of two neutron stars or black holes---carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here we focus on a particularly appealing extension of general relativity, which corrects Einstein's theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory, and (i) find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations; (ii) discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally (iii) show that...

  17. Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign – Part II: Radar investigations and modelling studies

    Directory of Open Access Journals (Sweden)

    A. Serafimovich

    2006-11-01

    Full Text Available We present an experimental and modelling study of a strong gravity wave event in the upper troposphere/lower stratosphere near the Scandinavian mountain ridge. Continuous VHF radar measurements during the MaCWAVE rocket and ground-based measurement campaign were performed at the Norwegian Andoya Rocket Range (ARR near Andenes (69.3° N, 16° E in January 2003. Detailed gravity wave investigations based on PSU/NCAR Fifth-Generation Mesoscale Model (MM5 data have been used for comparison with experimentally obtained results. The model data show the presence of a mountain wave and of an inertia gravity wave generated by a jet streak near the tropopause region. Temporal and spatial dependencies of jet induced inertia gravity waves with dominant observed periods of about 13 h and vertical wavelengths of ~4.5–5 km are investigated with wavelet transform applied on radar measurements and model data. The jet induced wave packet is observed to move upstream and downward in the upper troposphere. The model data agree with the experimentally obtained results fairly well. Possible reasons for the observed differences, e.g. in the time of maximum of the wave activity, are discussed. Finally, the vertical fluxes of horizontal momentum are estimated with different methods and provide similar amplitudes. We found indications that the derived positive vertical flux of the horizontal momentum corresponds to the obtained parameters of the jet-induced inertia gravity wave, but only at the periods and heights of the strongest wave activity.

  18. A computational study of radiation and gravity effect on temperature and soot formation in a methane air co-flow diffusion flame

    Energy Technology Data Exchange (ETDEWEB)

    Bhowal, Arup Jyoti, E-mail: arupjyoti.bhowal@heritageit.edu [Department of Mechanical Engineering, Heritage Institute of Technology, Chowbaga Road, Anandapur, Kolkata-700 107, West Bengal (India); Mandal, Bijan Kumar, E-mail: bkm375@yahoo.co.in [Department of Mechanical Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah – 711103, West Bengal (India)

    2016-07-12

    An effort has been made for a quantitative assessment of the soot formed under steady state in a methane air co flow diffusion flame by a numerical simulation at normal gravity and at lower gravity levels of 0.5 G, 0.1 G and 0.0001 G (microgravity). The peak temperature at microgravity is reduced by about 50 K than that at normal gravity level. There is an augmentation of soot formation at lower gravity levels. Peak value at microgravity multiplies by a factor of ∼7 of that at normal gravity. However, if radiation is not considered, soot formation is found to be much more.

  19. Characterization of interfacial waves in horizontal core-annular flow

    Science.gov (United States)

    Tripathi, Sumit; Bhattacharya, Amitabh; Singh, Ramesh; Tabor, Rico F.

    2016-11-01

    In this work, we characterize interfacial waves in horizontal core annular flow (CAF) of fuel-oil and water. Experimental studies on CAF were performed in an acrylic pipe of 15.5mm internal diameter, and the time evolution of the oil-water interface shape was recorded with a high speed camera for a range of different flow-rates of oil (Qo) and water (Qw). The power spectrum of the interface shape shows a range of notable features. First, there is negligible energy in wavenumbers larger than 2 π / a , where a is the thickness of the annulus. Second, for high Qo /Qw , there is no single dominant wavelength, as the flow in the confined annulus does not allow formation of a preferred mode. Third, for lower Qo /Qw , a dominant mode arises at a wavenumber of 2 π / a . We also observe that the power spectrum of the interface shape depends weakly on Qw, and strongly on Qo, perhaps because the net shear rate in the annulus appears to depend weakly on Qw as well. We also attempt to build a general empirical model for CAF by relating the interfacial stress (calculated via the mean pressure gradient) to the flow rate in the annulus, the annular thickness and the core velocity. Authors are thankful to Orica Mining Services (Australia) for the financial support.

  20. Approximate Dispersion Relations for Waves on Arbitrary Shear Flows

    Science.gov (United States)

    Ellingsen, S. À.; Li, Y.

    2017-12-01

    An approximate dispersion relation is derived and presented for linear surface waves atop a shear current whose magnitude and direction can vary arbitrarily with depth. The approximation, derived to first order of deviation from potential flow, is shown to produce good approximations at all wavelengths for a wide range of naturally occuring shear flows as well as widely used model flows. The relation reduces in many cases to a 3-D generalization of the much used approximation by Skop (1987), developed further by Kirby and Chen (1989), but is shown to be more robust, succeeding in situations where the Kirby and Chen model fails. The two approximations incur the same numerical cost and difficulty. While the Kirby and Chen approximation is excellent for a wide range of currents, the exact criteria for its applicability have not been known. We explain the apparently serendipitous success of the latter and derive proper conditions of applicability for both approximate dispersion relations. Our new model has a greater range of applicability. A second order approximation is also derived. It greatly improves accuracy, which is shown to be important in difficult cases. It has an advantage over the corresponding second-order expression proposed by Kirby and Chen that its criterion of accuracy is explicitly known, which is not currently the case for the latter to our knowledge. Our second-order term is also arguably significantly simpler to implement, and more physically transparent, than its sibling due to Kirby and Chen.Plain Language SummaryIn order to answer key questions such as how the ocean surface affects the climate, erodes the coastline and transports nutrients, we must understand how waves move. This is not so easy when depth varying currents are present, as they often are in coastal waters. We have developed a modeling tool for accurately predicting wave properties in such situations, ready for use, for example, in the complex oceanographic computer models. Our

  1. Numerical simulation of travelling wave induced electrothermal fluid flow

    International Nuclear Information System (INIS)

    Perch-Nielsen, Ivan R; Green, Nicolas G; Wolff, Anders

    2004-01-01

    Many microdevices for manipulating particles and cells use electric fields to produce a motive force on the particles. The movement of particles in non-uniform electric fields is called dielectrophoresis, and the usual method of applying this effect is to pass the particle suspension over a microelectrode structure. If the suspension has a noticeable conductivity, one important side effect is that the electric field drives a substantial conduction current through the fluid, causing localized Joule-heating. The resulting thermal gradient produces local conductivity and permittivity changes in the fluid. Dielectrophoretic forces acting upon these pockets of fluid will then produce motion of both the fluid and the particles. This paper presents a numerical solution of the electrical force and the resulting electrothermal driven fluid flow on a travelling wave structure. This common electrode geometry consists of interdigitated electrodes laid down in a long array, with the phase of the applied potential shifted by 90 0 on each subsequent electrode. The resulting travelling electric field was simulated and the thermal field and electrical body force on the fluid calculated, for devices constructed from two typical materials: silicon and glass. The electrothermal fluid flow in the electrolyte over the electrode array was then numerically simulated. The model predicts that the thermal field depends on the conductivity and applied voltage, but more importantly on the geometry of the system and the material used in the construction of the device. The velocity of the fluid flow depends critically on the same parameters, with slight differences in the thermal field for glass and silicon leading to diametrically opposite flow direction with respect to the travelling field for the two materials. In addition, the imposition of slight external temperature gradients is shown to have a large effect on the fluid flow in the device, under certain conditions leading to a reversal of

  2. Towards New Constraints in Extended Theories of Gravity: Cosmography and Gravitational-Wave Signals from Neutron Stars

    Directory of Open Access Journals (Sweden)

    Álvaro de la Cruz Dombriz

    2018-02-01

    Full Text Available Combined cosmological, astrophysical and numerical tests may shed some light on the viability of theories of gravity beyond Einsteinian relativity. In this letter, we present two different techniques providing complementary ways of testing new physics beyond the Λ CDM cosmological paradigm. First, we shall present some of the latest progress and shortcomings in the cosmographic model-independent approach for several modified gravity theories using supernovae catalogues, baryonic acoustic oscillation data and H ( z differential age compilations. Second, we shall show how once the Einsteinian paradigm is abandoned, the phenomenology of neutron stars changes dramatically since neutron-star masses can be much larger than their General Relativity counterparts. Consequently, the total energy available for radiating gravitational waves could be of the order of several solar masses, and thus a merger of these stars constitutes a privileged wave source. Unfortunately at the present time our persisting lack of understanding in the strong interaction sector does not allow to distinguish the alternative theories from the usual General Relativity predictions.

  3. A single dumbbell falling under gravity in a cellular flow field

    CERN Document Server

    Piva, M F

    2003-01-01

    We study the motion of a single polymer chain settling under gravity in an ensemble of periodic, cellular flow fields, which are steady in time. The molecule is an elastic dumbbell composed of two beads connected by a nonbendable Hookean spring. Each bead is subject to a Stokes drag and a Brownian force from the flow. In the absence of particle inertia, the molecule settles out at a rate which depends on three parameters: the particle velocity in a fluid at rest, V sub g , the spring constant, B, and the diffusion coefficient, D. We investigate the dependence of the molecule settling velocity on B, for fixed V sub g and D. It is found that this velocity strongly depends on B and it has a minimum value less than V sub g. We also find that the molecule is temporarily trapped at fixed points for certain values of the parameters. We analyse one fixed point in detail and conclude that its stability is the main factor which contributes to slowing down the settling process.

  4. Dimensional flow and fuzziness in quantum gravity: Emergence of stochastic spacetime

    Directory of Open Access Journals (Sweden)

    Gianluca Calcagni

    2017-10-01

    Full Text Available We show that the uncertainty in distance and time measurements found by the heuristic combination of quantum mechanics and general relativity is reproduced in a purely classical and flat multi-fractal spacetime whose geometry changes with the probed scale (dimensional flow and has non-zero imaginary dimension, corresponding to a discrete scale invariance at short distances. Thus, dimensional flow can manifest itself as an intrinsic measurement uncertainty and, conversely, measurement-uncertainty estimates are generally valid because they rely on this universal property of quantum geometries. These general results affect multi-fractional theories, a recent proposal related to quantum gravity, in two ways: they can fix two parameters previously left free (in particular, the value of the spacetime dimension at short scales and point towards a reinterpretation of the ultraviolet structure of geometry as a stochastic foam or fuzziness. This is also confirmed by a correspondence we establish between Nottale scale relativity and the stochastic geometry of multi-fractional models.

  5. Dimensional flow and fuzziness in quantum gravity: Emergence of stochastic spacetime

    International Nuclear Information System (INIS)

    Calcagni, Gianluca; Ronco, Michele

    2017-01-01

    We show that the uncertainty in distance and time measurements found by the heuristic combination of quantum mechanics and general relativity is reproduced in a purely classical and flat multi-fractal spacetime whose geometry changes with the probed scale (dimensional flow) and has non-zero imaginary dimension, corresponding to a discrete scale invariance at short distances. Thus, dimensional flow can manifest itself as an intrinsic measurement uncertainty and, conversely, measurement-uncertainty estimates are generally valid because they rely on this universal property of quantum geometries. These general results affect multi-fractional theories, a recent proposal related to quantum gravity, in two ways: they can fix two parameters previously left free (in particular, the value of the spacetime dimension at short scales) and point towards a reinterpretation of the ultraviolet structure of geometry as a stochastic foam or fuzziness. This is also confirmed by a correspondence we establish between Nottale scale relativity and the stochastic geometry of multi-fractional models.

  6. Dimensional flow and fuzziness in quantum gravity: Emergence of stochastic spacetime

    Science.gov (United States)

    Calcagni, Gianluca; Ronco, Michele

    2017-10-01

    We show that the uncertainty in distance and time measurements found by the heuristic combination of quantum mechanics and general relativity is reproduced in a purely classical and flat multi-fractal spacetime whose geometry changes with the probed scale (dimensional flow) and has non-zero imaginary dimension, corresponding to a discrete scale invariance at short distances. Thus, dimensional flow can manifest itself as an intrinsic measurement uncertainty and, conversely, measurement-uncertainty estimates are generally valid because they rely on this universal property of quantum geometries. These general results affect multi-fractional theories, a recent proposal related to quantum gravity, in two ways: they can fix two parameters previously left free (in particular, the value of the spacetime dimension at short scales) and point towards a reinterpretation of the ultraviolet structure of geometry as a stochastic foam or fuzziness. This is also confirmed by a correspondence we establish between Nottale scale relativity and the stochastic geometry of multi-fractional models.

  7. Dilute suspensions in annular shear flow under gravity: simulation and experiment

    Directory of Open Access Journals (Sweden)

    Schröer Kevin

    2017-01-01

    Full Text Available A dilute suspension in annular shear flow under gravity was simulated using multi-particle collision dynamics (MPC and compared to experimental data. The focus of the analysis is the local particle velocity and density distribution under the influence of the rotational and gravitational forces. The results are further supported by a deterministic approximation of a single-particle trajectory and OpenFOAM CFD estimations of the overcritical frequency range. Good qualitative agreement is observed for single-particle trajectories between the statistical mean of MPC simulations and the deterministic approximation. Wall contact and detachment however occur earlier in the MPC simulation, which can be explained by the inherent thermal noise of the method. The multi-particle system is investigated at the point of highest particle accumulation that is found at 2/3 of the particle revolution, starting from the top of the annular gap. The combination of shear flow and a slowly rotating volumetric force leads to strong local accumulation in this section that increases the particle volume fraction from overall 0.7% to 4.7% at the outer boundary. MPC simulations and experimental observations agree well in terms of particle distribution and a close to linear velocity profile in radial direction.

  8. Investigation of fog structure affected by gravity waves and turbulence in the mountainous region of Pyeongchang, Korea, the place for the 2018 Winter Olympics and Paralympics

    Science.gov (United States)

    La, I.; Yum, S. S.; Yeom, J. M.; Gultepe, I.

    2017-12-01

    Since microphysical and dynamical processes of fog are not well-known and have non-linear relationships among processes that are related to fog formation, improving the accuracy of the fog forecasting/nowcasting system is challenging. For these reasons, understanding the fog mechanism is needed to develop the fog forecasting system. So, we focus on understanding fog-turbulence interactions and fog-gravity wave interactions. Many studies noted that turbulence plays important roles in fog. However, a discrepancy between arguments for the effect of turbulent mixing on fog formation exists. Several studies suggested that turbulent mixing suppresses fog formation. Some other studies reported that turbulent mixing contributes to fog formation. On the other hand, several quasi-periodic oscillations of temperature, visibility, and vertical velocity, which have period of 10-20 minutes, were observed to be related to gravity waves in fog; because gravity waves play significant dynamic roles in the atmosphere. Furthermore, a numerical study suggested that gravity waves, simulated near the top of the fog layer, may affect fog microphysics. Thus, we investigate the effects of turbulent mixing on fog formation and the influences of gravity waves on fog microphysics to understand fog structure in Pyeongchang. In these studies, we analyze the data that are obtained from doppler lidar and 3.5 m meteorological observation tower including 3D-ultrasonic anemometer, IR sensor, and fog monitor during ICE-POP (International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games) campaign. In these instruments, doppler lidar is a good instrument to observe the gravity waves near the fog top, while in situ measurements have small spatial coverage. The instruments are installed at the mountainous terrain of Pyeongchang, Korea. More details will be presented at the conference.

  9. ON THE VARIATION OF ZONAL GRAVITY COEFFICIENTS OF A GIANT PLANET CAUSED BY ITS DEEP ZONAL FLOWS

    International Nuclear Information System (INIS)

    Kong Dali; Zhang Keke; Schubert, Gerald

    2012-01-01

    Rapidly rotating giant planets are usually marked by the existence of strong zonal flows at the cloud level. If the zonal flow is sufficiently deep and strong, it can produce hydrostatic-related gravitational anomalies through distortion of the planet's shape. This paper determines the zonal gravity coefficients, J 2n , n = 1, 2, 3, ..., via an analytical method taking into account rotation-induced shape changes by assuming that a planet has an effective uniform density and that the zonal flows arise from deep convection and extend along cylinders parallel to the rotation axis. Two different but related hydrostatic models are considered. When a giant planet is in rigid-body rotation, the exact solution of the problem using oblate spheroidal coordinates is derived, allowing us to compute the value of its zonal gravity coefficients J-bar 2n , n=1,2,3,..., without making any approximation. When the deep zonal flow is sufficiently strong, we develop a general perturbation theory for estimating the variation of the zonal gravity coefficients, ΔJ 2n =J 2n -J-bar 2n , n=1,2,3,..., caused by the effect of the deep zonal flows for an arbitrarily rapidly rotating planet. Applying the general theory to Jupiter, we find that the deep zonal flow could contribute up to 0.3% of the J 2 coefficient and 0.7% of J 4 . It is also found that the shape-driven harmonics at the 10th zonal gravity coefficient become dominant, i.e., ΔJ 2n >=J-bar 2n for n ≥ 5.

  10. A bulk localized state and new holographic renormalization group flow in 3D spin-3 gravity

    Science.gov (United States)

    Nakayama, Ryuichi; Suzuki, Tomotaka

    2018-04-01

    We construct a localized state of a scalar field in 3D spin-3 gravity. 3D spin-3 gravity is thought to be holographically dual to W3-extended CFT on a boundary at infinity. It is known that while W3 algebra is a nonlinear algebra, in the limit of large central charge c a linear finite-dimensional subalgebra generated by Wn (n = 0,±1,±2) and Ln (n = 0,±1) is singled out. The localized state is constructed in terms of these generators. To write down an equation of motion for a scalar field which is satisfied by this localized state, it is necessary to introduce new variables for an internal space α±, β±, γ, in addition to ordinary coordinates x± and y. The higher-dimensional space, which combines the bulk space-time with the “internal space,” which is an analog of superspace in supersymmetric theory, is introduced. The “physical bulk space-time” is a 3D hypersurface with constant α±, β± and γ embedded in this space. We will work in Poincaré coordinates of AdS space and consider W-quasi-primary operators Φh(x+) with a conformal weight h in the boundary and study two and three point functions of W-quasi-primary operators transformed as eix+L‑1heβ+W‑1hΦh(0)e‑β+W‑1he‑ix+L‑1h. Here, Lnh and Wnh are sl(3,R) generators in the hyperbolic basis for Poincaré coordinates. It is shown that in the β+ →∞ limit, the conformal weight changes to a new value h‧ = h/2. This may be regarded as a Renormalization Group (RG) flow. It is argued that this RG flow will be triggered by terms ΔS ∝ β+W ‑1h + β‑W¯ ‑1h added to the action.

  11. Dynamics of zonal flows and self-regulating drift-wave turbulence

    International Nuclear Information System (INIS)

    Diamond, P.H.; Fleischer, J.; Rosenbluth, M.N.; Hinton, F.L.; Malkov, M.; Smolyakov, A.

    1999-01-01

    We present a theory of zonal flow - drift wave dynamics. Zonal flows are generated by modulational instability of a drift wave spectrum, and are damped by collisions. Drift waves undergo random shearing-induced refraction, resulting in increased mean square radial wavenumber. Drift waves and zonal flows together form a simple dynamical system, which has a single stable fixed point. In this state, the fluctuation intensity and turbulent diffusivity are ultimately proportional to the collisional zonal flow damping. The implications of these results for transport models is discussed. (author)

  12. Dynamics of zonal flows and self-regulating drift-wave turbulence

    International Nuclear Information System (INIS)

    Diamond, P.H.; Fleischer, J.; Rosenbluth, M.; Hinton, F.L.; Malkov, M.; Smolyakov, A.

    2001-01-01

    We present a theory of zonal flow - drift wave dynamics. Zonal flows are generated by modulational instability of a drift wave spectrum, and are damped by collisions. Drift waves undergo random shearing-induced refraction, resulting in increased mean square radial wavenumber. Drift waves and zonal flows together form a simple dynamical system, which has a single stable fixed point. In this state, the fluctuation intensity and turbulent diffusivity are ultimately proportional to the collisional zonal flow damping. The implications of these results for transport models is discussed. (author)

  13. Renormalization group flows in σ-models coupled to two-dimensional dynamical gravity

    International Nuclear Information System (INIS)

    Penati, S.; Santambrogio, A.; Zanon, D.

    1997-01-01

    We consider a bosonic σ-model coupled to two-dimensional gravity. In the semiclassical limit, c→-∞, we compute the gravity dressing of the β-functions at two-loop order in the matter fields. We find that the corrections due to the presence of dynamical gravity are not expressible simply in terms of a multiplicative factor as previously obtained at the one-loop level. Our result indicates that the critical points of the theory are non-trivially influenced and modified by the induced gravity. (orig.)

  14. Integrated flux-flow oscillators for submillimeter wave receivers

    International Nuclear Information System (INIS)

    Koshelets, V.P.; Shchukin, A.V.; Shitov, S.V.; Filippenko, L.V.; Fischer, G.M.; Mygind, J.

    1994-01-01

    A superconducting Flux-Flow Oscillator (FFO) integrated on the same chip with a small Josephson junction detector has been experimentally investigated in the frequency range 100 - 450 GHz. Both the emitted power and the frequency of the FFO can be varied by adjusting the dc bias current and/or the applied dc magnetic field. Microwave powers as high as 0.3 μW have been measured at 375 GHz. The spectral width of the FFO is about 1 MHz as estimated from harmonic mixing experiments. Also a fully integrated superconducting submillimeter wave receiver using the FFO as local oscillator has been successfully tested. The circuit included coupling transformers, a superconducting variable attenuator and a detector junction with tuned-out capacitance. (orig.)

  15. Sand Waves in Environmental Flows: Insights gained by LES

    Science.gov (United States)

    Sotiropoulos, Fotis

    2014-11-01

    In fluvial and coastal environments, sediment transport processes induced by near-bed coherent structures in the turbulent boundary layer developing over a mobile sediment bed result in the formation of dynamically rich sand waves, or bed forms, which grow and migrate continuously. Bed form migration alters streambed roughness and provides the primary mechanism for transporting large amounts of sediment through riverine systems impacting the morphology, streambank stability, and ecology of waterways. I will present recent computational advances, which have enabled coupled, hydro-morphodynamic large-eddy simulation (LES) of turbulent flow in mobile-bed open channels. Numerical simulations: 1) elucidate the role of near-bed sweeps in the turbulent boundary layer as the mechanism for initiating the instability of the initially flat sand bed; 2) show how near-bed processes give rise to aperiodic eruptions of suspended sediment at the free surface; and 3) clarify the mechanism via which sand waves migrate. Furthermore, in agreement with recent experimental observations, the computed spectra of the resolved velocity fluctuations above the bed exhibit a distinct spectral gap whose width increases with distance from the bed. The spectral gap delineates the spectrum of turbulence from that of slowly evolving coherent structures associated with sand wave migration. The talk will also present computational results demonstrating the feasibility of carrying out coupled, hydro-morphodynamic LES of large dunes migrating in meandering streams and rivers with embedded hydraulic structures and discuss future challenges and opportunities. This work was supported by NSF Grants EAR-0120914 and EAR-0738726, and National Cooperative Highway Research Program Grant NCHRP-HR 24-33.

  16. Genesis of Twin Tropical Cyclones as Revealed by a Global Mesoscale Model: The Role of Mixed Rossby Gravity Waves

    Science.gov (United States)

    Shen, Bo-Wen; Tao, Wei-Kuo; Lin, Yuh-Lang; Laing, Arlene

    2012-01-01

    In this study, it is proposed that twin tropical cyclones (TCs), Kesiny and 01A, in May 2002 formed in association with the scale interactions of three gyres that appeared as a convectively coupled mixed Rossby gravity (ccMRG) wave during an active phase of the Madden-Julian Oscillation (MJO). This is shown by analyzing observational data, including NCEP reanalysis data and METEOSAT 7 IR satellite imagery, and performing numerical simulations using a global mesoscale model. A 10-day control run is initialized at 0000 UTC 1 May 2002 with grid-scale condensation but no sub-grid cumulus parameterizations. The ccMRG wave was identified as encompassing two developing and one non-developing gyres, the first two of which intensified and evolved into the twin TCs. The control run is able to reproduce the evolution of the ccMRG wave and thus the formation of the twin TCs about two and five days in advance as well as their subsequent intensity evolution and movement within an 8-10 day period. Five additional 10-day sensitivity experiments with different model configurations are conducted to help understand the interaction of the three gyres, leading to the formation of the TCs. These experiments suggest the improved lead time in the control run may be attributed to the realistic simulation of the ccMRG wave with the following processes: (1) wave deepening (intensification) associated with a reduction in wavelength and/or the intensification of individual gyres, (2) poleward movement of gyres that may be associated with boundary layer processes, (3) realistic simulation of moist processes at regional scales in association with each of the gyres, and (4) the vertical phasing of low- and mid-level cyclonic circulations associated with a specific gyre.

  17. Fast wave power flow along SOL field lines in NSTX

    Science.gov (United States)

    Perkins, R. J.; Bell, R. E.; Diallo, A.; Gerhardt, S.; Hosea, J. C.; Jaworski, M. A.; Leblanc, B. P.; Kramer, G. J.; Phillips, C. K.; Roquemore, L.; Taylor, G.; Wilson, J. R.; Ahn, J.-W.; Gray, T. K.; Green, D. L.; McLean, A.; Maingi, R.; Ryan, P. M.; Jaeger, E. F.; Sabbagh, S.

    2012-10-01

    On NSTX, a major loss of high-harmonic fast wave (HHFW) power can occur along open field lines passing in front of the antenna over the width of the scrape-off layer (SOL). Up to 60% of the RF power can be lost and at least partially deposited in bright spirals on the divertor floor and ceiling [1,2]. The flow of HHFW power from the antenna region to the divertor is mostly aligned along the SOL magnetic field [3], which explains the pattern of heat deposition as measured with infrared (IR) cameras. By tracing field lines from the divertor back to the midplane, the IR data can be used to estimate the profile of HHFW power coupled to SOL field lines. We hypothesize that surface waves are being excited in the SOL, and these results should benchmark advanced simulations of the RF power deposition in the SOL (e.g., [4]). Minimizing this loss is critical optimal high-power long-pulse ICRF heating on ITER while guarding against excessive divertor erosion.[4pt] [1] J.C. Hosea et al., AIP Conf Proceedings 1187 (2009) 105. [0pt] [2] G. Taylor et al., Phys. Plasmas 17 (2010) 056114. [0pt] [3] R.J. Perkins et al., to appear in Phys. Rev. Lett. [0pt] [4] D.L. Green et al., Phys. Rev. Lett. 107 (2011) 145001.

  18. Analysis of Spring Development and Gravity Flow System to Capture Water for Local Communities

    Directory of Open Access Journals (Sweden)

    Adiningrum Cita

    2017-01-01

    Full Text Available Springs as water sources are relatively inexpensive but highly susceptible to contamination since they are fed by shallow groundwater. Proper spring development helps protect the water from contamination. This study presents an analysis and design of spring development including the type of broncaptering/collecting wall, the dimension for the spring box and the conduction line. In addition, a guideline on “Springwater Construction” published by the Ministry of Public Works has been used in this design. A concentrated spring in Wates, Magelang, Central Java is used as a case study. The design calls for the collection of water from a spring using sets of broncaptering and a spring box, then piping it by gravity a distance of 5.1 kilometers to Van Lith Senior High School. Analysis was done using a manual calculation, which is subsequently compared to the result of HYDROFLO 3 software. Results show that the spring with a flow rate of 0.12 litre/s (manual and 0.17 litre/s (software will be collected into a 5 m3 volume of spring box. The spring box with a +543 m water surface elevation is being supplied to Van Lith +384 m ground elevation using a uniform PVC pipelines with a ¾ inch of diameter.

  19. Medication and volume delivery by gravity-driven micro-drip intravenous infusion: potential variations during "wide-open" flow.

    Science.gov (United States)

    Pierce, Eric T; Kumar, Vikram; Zheng, Hui; Peterfreund, Robert A

    2013-03-01

    Gravity-driven micro-drip infusion sets allow control of medication dose delivery by adjusting drops per minute. When the roller clamp is fully open, flow in the drip chamber can be a continuous fluid column rather than discrete, countable, drops. We hypothesized that during this "wide-open" state, drug delivery becomes dependent on factors extrinsic to the micro-drip set and is therefore difficult to predict. We conducted laboratory experiments to characterize volume delivery under various clinically relevant conditions of wide-open flow in an in vitro laboratory model. A micro-drip infusion set, plugged into a bag of normal saline, was connected to a high-flow stopcock at the distal end. Vertically oriented IV catheters (gauges 14-22) were connected to the stopcock. The fluid meniscus height in the bag was fixed (60-120 cm) above the outflow point. The roller clamp on the infusion set was in fully open position for all experiments resulting in a continuous column of fluid in the drip chamber. Fluid volume delivered in 1 minute was measured 4 times with each condition. To model resistive effects of carrier flow, volumetric infusion pumps were used to deliver various flow rates of normal saline through a carrier IV set into which a micro-drip infusion was "piggybacked." We also compared delivery by micro-drip infusion sets from 3 manufacturers. The volume of fluid delivered by gravity-driven infusion under wide-open conditions (continuous fluid column in drip chamber) varied 2.9-fold (95% confidence interval, 2.84-2.96) depending on catheter size and fluid column height. Total model resistance of the micro-drip with stopcock and catheter varied with flow rate. Volume delivered by the piggybacked micro-drip decreased up to 29.7% ± 0.8% (mean ± SE) as the carrier flow increased from 0 to 1998 mL/min. Delivery characteristics of the micro-drip infusion sets from 3 different manufacturers were similar. Laboratory simulation of clinical situations with gravity

  20. Fermions in the 5D Gravity-Scalar Standing Wave Braneworld

    OpenAIRE

    Gogberashvili, Merab; Midodashvili, Pavle

    2014-01-01

    In the article we investigate localization problem for spinor fields within the 5D standing wave braneworld with the bulk real scalar field and show that there exist normalizable fermion field zero modes on the brane.

  1. Effects of traveling waves on flow separation and turbulence

    Science.gov (United States)

    Akbarzadeh, Amir Mahdi; Borazjani, Iman; scientific computing; biofluids laboratory Team

    2017-11-01

    Stable leading edge vortex (LEV) is observed in many flying, hovering and also some aquatic creatures. However, the LEV stability in aquatic animal, in contrast to hovering ones, is not well understood. Here, we study the flow over an inclined plate with an undulatory motion inspired from aquatic swimmers using our immersed boundary, large-eddy simulations (LES). The angle of attack is five degrees and Reynolds number (Re) is 20,000. The undulation is a traveling wave, which has a constant amplitude of 0.01 with respect to chord length and a different wavelength and Strouhal number (St =fA/U, f: frequency, A: amplitude, and U: free stream velocity) for each case. Over a fixed plate the LEV becomes unstable as it reaches the trailing edge and sheds to the wake, whereas over the undulating plate with St =0.2 the LEV becomes stable. The visualization of time average results shows there is a favorable pressure gradient along the tangential direction in cases the LEV becomes stable, which we explain analytically by showing the correlation between the average pressure gradient, St, and wavelength. Finally, the effects of undulatory moving walls of a channel flow on the turbulent statistics is shown. This work was partly supported by the National Science Foundation (NSF) CAREER Grant CBET 1453982, and the Center of Computational Research (CCR) of University at Buffalo.

  2. Hybrid upwind discretization of nonlinear two-phase flow with gravity

    Science.gov (United States)

    Lee, S. H.; Efendiev, Y.; Tchelepi, H. A.

    2015-08-01

    Multiphase flow in porous media is described by coupled nonlinear mass conservation laws. For immiscible Darcy flow of multiple fluid phases, whereby capillary effects are negligible, the transport equations in the presence of viscous and buoyancy forces are highly nonlinear and hyperbolic. Numerical simulation of multiphase flow processes in heterogeneous formations requires the development of discretization and solution schemes that are able to handle the complex nonlinear dynamics, especially of the saturation evolution, in a reliable and computationally efficient manner. In reservoir simulation practice, single-point upwinding of the flux across an interface between two control volumes (cells) is performed for each fluid phase, whereby the upstream direction is based on the gradient of the phase-potential (pressure plus gravity head). This upwinding scheme, which we refer to as Phase-Potential Upwinding (PPU), is combined with implicit (backward-Euler) time discretization to obtain a Fully Implicit Method (FIM). Even though FIM suffers from numerical dispersion effects, it is widely used in practice. This is because of its unconditional stability and because it yields conservative, monotone numerical solutions. However, FIM is not unconditionally convergent. The convergence difficulties are particularly pronounced when the different immiscible fluid phases switch between co-current and counter-current states as a function of time, or (Newton) iteration. Whether the multiphase flow across an interface (between two control-volumes) is co-current, or counter-current, depends on the local balance between the viscous and buoyancy forces, and how the balance evolves in time. The sensitivity of PPU to small changes in the (local) pressure distribution exacerbates the problem. The common strategy to deal with these difficulties is to cut the timestep and try again. Here, we propose a Hybrid-Upwinding (HU) scheme for the phase fluxes, then HU is combined with implicit

  3. Aggradational lobe fringes: the influence of subtle intrabasinal seabed topography on sediment gravity flow processes and lobe stacking patterns

    OpenAIRE

    Flint, Stephen; Hodgson, David; Stevenson, Christopher; Spychala, Yvonne

    2018-01-01

    Seabed topography is ubiquitous across basin-floor environments, and influences sediment gravity flows and sediment dispersal patterns. The impact of steep (several degrees) confining slopes on sedimentary facies and depositional architecture has been widely documented. However, the influence of gentle (fraction of a degree) confining slopes is less well-documented, largely due to outcrop limitations. Here, exceptional outcrop and research borehole data from Unit A of the Permian Laingsburg F...

  4. Development and trade competitiveness of the European wine sector: A gravity analysis of intra-EU flows

    OpenAIRE

    Pasquale Lombardi; Andrea Dal Bianco; Roberto Freda; Francesco Caracciolo; Luigi Cembalo

    2016-01-01

    This study analyses the intra-EU trade of the world׳s chief wine exporters, namely Italy, France and Spain. Using an augmented version of the gravity model we empirically assess which of the three countries have experienced growth in intra-EU market trade. Effects of transportation costs, as well as demand and supply gaps between origin and destination countries, on the size of bilateral trade flows were specifically taken into account. Estimation results highlight the differences between bul...

  5. Internal and vorticity waves in decaying stratified flows

    Science.gov (United States)

    Matulka, A.; Cano, D.

    2009-04-01

    Most predictive models fail when forcing at the Rossby deformation Radius is important and a large range of scales have to be taken into account. When mixing of reactants or pollutants has to be accounted, the range of scales spans from hundreds of Kilometers to the Bachelor or Kolmogorov sub milimiter scales. We present some theoretical arguments to describe the flow in terms of the three dimensional vorticity equations, using a lengthscale related to the vorticity (or enstrophy ) transport. Effect of intermittent eddies and non-homogeneity of diffusion are also key issues in the environment because both stratification and rotation body forces are important and cause anisotropy/non-homogeneity. These problems need further theoretical, numerical and observational work and one approach is to try to maximize the relevant geometrical information in order to understand and therefore predict these complex environmental dispersive flows. The importance of the study of turbulence structure and its relevance in diffusion of contaminants in environmental flows is clear when we see the effect of environmental disasters such as the Prestige oil spill or the Chernobil radioactive cloud spread in the atmosphere. A series of Experiments have been performed on a strongly stratified two layer fluid consisting of Brine in the bottom and freshwater above in a 1 square meter tank. The evolution of the vortices after the passage of a grid is video recorded and Particle tracking is applied on small pliolite particles floating at the interface. The combination of internal waves and vertical vorticity produces two separate time scales that may produce resonances. The vorticity is seen to oscilate in a complex way, where the frecuency decreases with time.

  6. Modeling magnetic field and TEC signatures of large-amplitude acoustic and gravity waves generated by natural hazard events

    Science.gov (United States)

    Zettergren, M. D.; Snively, J. B.; Inchin, P.; Komjathy, A.; Verkhoglyadova, O. P.

    2017-12-01

    Ocean and solid earth responses during earthquakes are a significant source of large amplitude acoustic and gravity waves (AGWs) that perturb the overlying ionosphere-thermosphere (IT) system. IT disturbances are routinely detected following large earthquakes (M > 7.0) via GPS total electron content (TEC) observations, which often show acoustic wave ( 3-4 min periods) and gravity wave ( 10-15 min) signatures with amplitudes of 0.05-2 TECU. In cases of very large earthquakes (M > 8.0) the persisting acoustic waves are estimated to have 100-200 m/s compressional velocities in the conducting ionospheric E and F-regions and should generate significant dynamo currents and magnetic field signatures. Indeed, some recent reports (e.g. Hao et al, 2013, JGR, 118, 6) show evidence for magnetic fluctuations, which appear to be related to AGWs, following recent large earthquakes. However, very little quantitative information is available on: (1) the detailed spatial and temporal dependence of these magnetic fluctuations, which are usually observed at a small number of irregularly arranged stations, and (2) the relation of these signatures to TEC perturbations in terms of relative amplitudes, frequency, and timing for different events. This work investigates space- and time-dependent behavior of both TEC and magnetic fluctuations following recent large earthquakes, with the aim to improve physical understanding of these perturbations via detailed, high-resolution, two- and three-dimensional modeling case studies with a coupled neutral atmospheric and ionospheric model, MAGIC-GEMINI (Zettergren and Snively, 2015, JGR, 120, 9). We focus on cases inspired by the large Chilean earthquakes from the past decade (viz., the M > 8.0 earthquakes from 2010 and 2015) to constrain the sources for the model, i.e. size, frequency, amplitude, and timing, based on available information from ocean buoy and seismometer data. TEC data are used to validate source amplitudes and to constrain

  7. Investigation of the relative effects of vascular branching structure and gravity on pulmonary arterial blood flow heterogeneity via an image-based computational model.

    Science.gov (United States)

    Burrowes, Kelly S; Hunter, Peter J; Tawhai, Merryn H

    2005-11-01