WorldWideScience

Sample records for surface temperature boundary

  1. Surface-to-subsurface temperature variations during the last century in a western boundary upwelling system (Southeastern, Brazil)

    Science.gov (United States)

    Venancio, Igor M.; Gomes, Vitor P.; Belem, Andre L.; Albuquerque, Ana Luiza S.

    2016-08-01

    The upper thermal gradient of a western boundary upwelling system was reconstructed for the last 100 years. The reconstruction was based on oxygen isotopic composition (δ18O) of four planktonic foraminifera species derived from two boxcores (BCCF10-01 and BCCF10-04) located in the southeastern Brazilian shelf. Calcification depths of the four planktonic foraminifera species were estimated in order to understand which layer of the water column was assessed. Changes in the upper thermal gradient were evaluated by using the δ18O difference from the surface-dwelling species Globigerinoides ruber (pink) and the deep-dwelling Neogloboquadrina dutertrei. The relative abundance of cold-water species and the δ13C of G. ruber (pink) were also used to evaluate changes on the surface layer. Our results demonstrate a trend to reduction on the temperature difference (∆T) between the surface and the thermocline layer towards the present for both cores, together with an increase on the relative abundance of cold-water species for the mid-shelf core (BCCF10-04) and a decrease in δ13C values of G. ruber (pink) for both cores. Despite the observable trend on the proxies, only the relative abundance of Turborotalita quinqueloba and the δ13C of G. ruber (pink) for the mid-shelf core presented statistically significant trends. These results were related to an increase in South Atlantic Central Water (SACW) intrusions in the sub-surface layer, especially on the middle shelf region. The SACW intrusions would lower the sea surface temperature and would bring a depleted δ13C of the dissolved inorganic carbon signature to the surface, which would be in agreement with our findings. Moreover, these mid-shelf SACW intrusions in the region were attributed to the Ekman pumping (wind stress curl-driven), which was previously reported to be an important mechanism in this upwelling system. The major outcomes to this western boundary current ecosystem from an intensification of the mid

  2. Transgressive Surface as Sequence Boundary

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Analysis of the four cases of the sequence boundary (SB)-transgressive surface (TS) relation in nature shows that applying transgressive surfaces as sequence boundaries has the following merits: it improves the methodology of stratigraphic subdivision; the position of transgressive surface in a sea level curve is relatively fixed; the transgressive surface is a transforming surface of the stratal structure; in platforms or ramps, the transgressive surface is the only choice for determining the sequence boundary; the transgressive surface is a readily recognized physical surface reflected by seismic records in seismostratigraphy. The paper reaches a conclusion that to delineate a SB in terms of the TS is theoretically and practically better than to delineate it between highstand and lowstand sediments as has been done traditionally.

  3. Scaling properties of velocity and temperature spectra above the surface friction layer in a convective atmospheric boundary layer

    Directory of Open Access Journals (Sweden)

    K. G. McNaughton

    2007-06-01

    Full Text Available We report velocity and temperature spectra measured at nine levels from 1.42 meters up to 25.7 m over a smooth playa in Western Utah. Data are from highly convective conditions when the magnitude of the Obukhov length (our proxy for the depth of the surface friction layer was less than 2 m. Our results are somewhat similar to the results reported from the Minnesota experiment of Kaimal et al. (1976, but show significant differences in detail. Our velocity spectra show no evidence of buoyant production of kinetic energy at at the scale of the thermal structures. We interpret our velocity spectra to be the result of outer eddies interacting with the ground, not "local free convection".

    We observe that velocity spectra represent the spectral distribution of the kinetic energy of the turbulence, so we use energy scales based on total turbulence energy in the convective boundary layer (CBL to collapse our spectra. For the horizontal velocity spectra this scale is (zi εo2/3, where zi is inversion height and εo is the dissipation rate in the bulk CBL. This scale functionally replaces the Deardorff convective velocity scale. Vertical motions are blocked by the ground, so the outer eddies most effective in creating vertical motions come from the inertial subrange of the outer turbulence. We deduce that the appropriate scale for the peak region of the vertical velocity spectra is (z εo2/3 where z is height above ground. Deviations from perfect spectral collapse under these scalings at large and small wavenumbers are explained in terms of the energy transport and the eddy structures of the flow.

    We find that the peaks of the temperature spectra collapse when wavenumbers are scaled using (z1/2 zi1/2. That is, the lengths of the thermal structures depend on both the lengths of the

  4. Surface free energy for systems with integrable boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Goehmann, Frank [Fachbereich C-Physik, Bergische Universitaet Wuppertal, 42097 Wuppertal (Germany); Bortz, Michael [Department of Theoretical Physics, Australian National University, Canberra ACT 0200 (Australia); Frahm, Holger [Institut fuer Theoretische Physik, Universitaet Hannover, 30167 Hannover (Germany)

    2005-12-16

    The surface free energy is the difference between the free energies for a system with open boundary conditions and the same system with periodic boundary conditions. We use the quantum transfer matrix formalism to express the surface free energy in the thermodynamic limit of systems with integrable boundary conditions as a matrix element of certain projection operators. Specializing to the XXZ spin-1/2 chain we introduce a novel 'finite temperature boundary operator' which characterizes the thermodynamical properties of surfaces related to integrable boundary conditions.

  5. Unsteady laminar mixed convection boundary layer flow near a vertical wedge due to oscillations in the free-stream and surface temperature

    Directory of Open Access Journals (Sweden)

    Roy N.C.

    2016-02-01

    Full Text Available The unsteady laminar boundary layer characteristics of mixed convection flow past a vertical wedge have been investigated numerically. The free-stream velocity and surface temperature are assumed to be oscillating in the magnitude but not in the direction of the oncoming flow velocity. The governing equations have been solved by two distinct methods, namely, the straightforward finite difference method for the entire frequency range, and the extended series solution for low frequency range and the asymptotic series expansion method for high frequency range. The results demonstrate the effects of the Richardson number, Ri, introduced to quantify the influence of mixed convection and the Prandtl number, Pr, on the amplitudes and phase angles of the skin friction and heat transfer. In addition, the effects of these parameters are examined in terms of the transient skin friction and heat transfer.

  6. The dynamic specification of surfaces and boundaries.

    Science.gov (United States)

    Cunningham, D W; Shipley, T F; Kellman, P J

    1998-01-01

    Sequential changes in small separated texture elements can produce perception of a moving form with continuous boundaries. This process of spatiotemporal boundary formation may exist to provide a robust means of detecting moving objects that occlude more distant textured surfaces. Whereas most research on spatiotemporal boundary formation has been focused on boundary and shape perception, two experiments are reported here on the perception of surface qualities in spatiotemporal boundary formation. In experiment 1 a free-report procedure was used to investigate whether surface perception can be determined by dynamic information alone, apart from static spatial differences. Results showed that dynamic information was sufficient to determine the appearance of a surface. This dynamic information may play an important role in other aspects of perception. In experiment 2, it was shown that dynamically specifying an extended, opaque surface facilitated edge perception. Implications for the relation of boundary and surface perception and for theories of perceptual transparency are discussed.

  7. Field observations and results of a 1-D boundary layer model for developing near-surface temperature maxima in the Western Arctic

    Directory of Open Access Journals (Sweden)

    Shawn G. Gallaher

    2017-03-01

    Full Text Available Summer sea ice extent in the Western Arctic has decreased significantly in recent years resulting in increased solar input into the upper ocean. Here, a comprehensive set of 'in situ' shipboard, on-ice, and autonomous ice-ocean measurements were made of the early stages of formation of the near-surface temperature maximum (NSTM in the Canada Basin. These observations along with the results from a 1-D turbulent boundary layer model indicate that heat storage associated with NSTM formation is largely due to the absorption of penetrating solar radiation just below a protective summer halocline. The depth of the summer halocline was found to be the most important factor for determining the amount of solar radiation absorbed in the NSTM layer, while halocline strength controlled the amount of heat removed from the NSTM by turbulent transport. Observations using the Naval Postgraduate School Turbulence Frame show that the NSTM was able to persist despite periods of intermittent turbulence because transport rates were too small to remove significant amounts of heat from the NSTM layer. The development of the early and late summer halocline and NSTM were found to be linked to summer season buoyancy and wind events. For the early summer NSTM, 1-D boundary layer model results show that melt pond drainage provides sufficient buoyancy to the summer halocline to prevent subsequent wind events from mixing out the NSTM. For the late summer NSTM, limited freshwater inputs reduce the strength of the summer halocline making the balance between interfacial stresses and buoyancy more tenuous. As a result, the late summer NSTM is an ephemeral feature dependent on local wind conditions, while the early summer NSTM is more persistent and able to store heat in the near-surface ocean beyond the summer season.

  8. Influence of small-scale North Atlantic sea surface temperature patterns on the marine boundary layer and free troposphere: a study using the atmospheric ARPEGE model

    Science.gov (United States)

    Piazza, Marie; Terray, Laurent; Boé, Julien; Maisonnave, Eric; Sanchez-Gomez, Emilia

    2016-03-01

    A high-resolution global atmospheric model is used to investigate the influence of the representation of small-scale North Atlantic sea surface temperature (SST) patterns on the atmosphere during boreal winter. Two ensembles of forced simulations are performed and compared. In the first ensemble (HRES), the full spatial resolution of the SST is maintained while small-scale features are smoothed out in the Gulf Stream region for the second ensemble (SMTH). The model shows a reasonable climatology in term of large-scale circulation and air-sea interaction coefficient when compared to reanalyses and satellite observations, respectively. The impact of small-scale SST patterns as depicted by differences between HRES and SMTH shows a strong meso-scale local mean response in terms of surface heat fluxes, convective precipitation, and to a lesser extent cloudiness. The main mechanism behind these statistical differences is that of a simple hydrostatic pressure adjustment related to increased SST and marine atmospheric boundary layer temperature gradient along the North Atlantic SST front. The model response to small-scale SST patterns also includes remote large-scale effects: upper tropospheric winds show a decrease downstream of the eddy-driven jet maxima over the central North Atlantic, while the subtropical jet exhibits a significant northward shift in particular over the eastern Mediterranean region. Significant changes are simulated in regard to the North Atlantic storm track, such as a southward shift of the storm density off the coast of North America towards the maximum SST gradient. A storm density decrease is also depicted over Greenland and the Nordic seas while a significant increase is seen over the northern part of the Mediterranean basin. Changes in Rossby wave breaking frequencies and weather regimes spatial patterns are shown to be associated to the jets and storm track changes.

  9. The temperature field and heat transfer in the porthole of the Space Shuttle - Outer surface under the 3rd kind nonlinear boundary condition

    Science.gov (United States)

    Tan, Heping; Yu, Qizheng; Zhang, Jizhou

    In this paper, the transient combined heat transfer in the silicon glass porthole of Space Shuttle is studied by control volume method, ray tracing method and spectral band model. The temperature field in the silicon glass and heat flux entering the space cabin are given under the 3rd kind nonlinear boundary condition. The computational results show, if the radiation in the silicon glass is omitted, the errors for temperature fields are not too evident, but for heat flux are quite large.

  10. SURFACE MESH PARAMETERIZATION WITH NATURAL BOUNDARY

    Institute of Scientific and Technical Information of China (English)

    Ye Ming; Zhu Xiaofeng; Wang Chengtao

    2003-01-01

    Using the projected curve of surface mesh boundary as parameter domain border, linear mapping parameterization with natural boundary is realized. A fast algorithm for least squares fitting plane of vertices in the mesh boundary is proposed. After the mesh boundary is projected onto the fitting plane, low-pass filtering is adopted to eliminate crossovers, sharp corners and cavities in the projected curve and convert it into an eligible convex parameter domain boundary. In order to facilitate quantitative evaluations of parameterization schemes, three distortion-measuring formulae are presented.

  11. Impact of storm-induced cooling of sea surface temperature on large turbulent eddies and vertical turbulent transport in the atmospheric boundary layer of Hurricane Isaac

    Science.gov (United States)

    Zhu, Ping; Wang, Yuting; Chen, Shuyi S.; Curcic, Milan; Gao, Cen

    2016-01-01

    Roll vortices in the atmospheric boundary layer (ABL) are important to oil operation and oil spill transport. This study investigates the impact of storm-induced sea surface temperature (SST) cooling on the roll vortices generated by the convective and dynamic instability in the ABL of Hurricane Isaac (2012) and the roll induced transport using hindcasting large eddy simulations (LESs) configured from the multiply nested Weather Research & Forecasting model. Two experiments are performed: one forced by the Unified Wave INterface - Coupled Model and the other with the SST replaced by the NCEP FNL analysis that does not include the storm-induced SST cooling. The simulations show that the roll vortices are the prevalent eddy circulations in the ABL of Isaac. The storm-induced SST cooling causes the ABL stability falls in a range that satisfies the empirical criterion of roll generation by dynamic instability, whereas the ABL stability without considering the storm-induced SST cooling meets the criterion of roll generation by convective instability. The ABL roll is skewed and the increase of convective instability enhances the skewness. Large convective instability leads to large vertical transport of heat and moisture; whereas the dominant dynamic instability results in large turbulent kinetic energy but relatively weak heat and moisture transport. This study suggests that failure to consider roll vortices or incorrect initiation of dynamic and convective instability of rolls in simulations may substantially affect the transport of momentum, energy, and pollutants in the ABL and the dispersion/advection of oil spill fume at the ocean surface.

  12. Restructuring surface tessellation with irregular boundary conditions

    Directory of Open Access Journals (Sweden)

    Tsung-Hsien Wang

    2014-12-01

    Full Text Available In this paper, the surface tessellation problem is explored, in particular, the task of meshing a surface with the added consideration of incorporating constructible building components. When a surface is tessellated into discrete counterparts, certain unexpected conditions usually occur at the boundary of the surface, in particular, when the surface is being trimmed. For example, irregularly shaped panels form at the trimmed edges. To reduce the number of irregular panels that may form during the tessellation process, this paper presents an algorithmic approach to restructuring the surface tessellation by investigating irregular boundary conditions. The objective of this approach is to provide an alternative way for freeform surface manifestation from a well-structured discrete model of the given surface.

  13. Boundary-layer temperatures in high accretion rate cataclysmic variables

    Energy Technology Data Exchange (ETDEWEB)

    Hoare, M.G.; Drew, J.E. (Oxford Univ. (UK). Dept. of Physics Oxford Univ. (UK). Dept. of Astrophysics)

    1991-04-01

    We use the Zanstra method to derive limits on boundary-layer temperatures in eclipsing dwarf novae during outburst and nova-like variables, using the observed He II {lambda}1640 and {lambda}4686 recombination lines. It is assumed that all the emission is produced in the wind rather than the accretion disc. This method constrains the boundary-layer temperatures to between 50 000 and 100 000 K depending on the degree of wind bipolarity. These estimates are lower than the T>or approx200 000 K predicted theoretically. Possible explanations include rapid rotation of the white dwarf and spreading of the boundary layer over the entire white-dwarf surface. (author).

  14. Studies of stability of blade cascade suction surface boundary layer

    Institute of Scientific and Technical Information of China (English)

    DONG Xue-zhi; YAN Pei-gang; HAN Wan-jin

    2007-01-01

    Compressible boundary layers stability on blade cascade suction surface was discussed by wind tunnel experiment and numerical solution. Three dimensional disturbance wave Parabolized Stability Equations(PSE) of orthogonal Curvilinear Coordinates in compressible flow was deducted. The surface pressure of blade in wind tunnel experiment was measured. The Falkner-Skan equation was solved under the boundary conditions of experiment result, and velocity, pressure and temperature of average flow were obtained. Substituted this result for discretization of the PSE Eigenvalue Problem, the stability problem can be solved.

  15. N-sided Surface Generation from Arbitrary Boundary Edges

    Science.gov (United States)

    2000-01-01

    Such surfaces are generally classified as transfinite surfaces, in which a surface is interpolated to span given curves. In the proposed method...the 3D space. Sabin calls the method of surface generation from boundary edges a " transfinite surface" in contrast with the one which is characterized...vectors. Thus, the surface is a transfinite surface in consideration of the boundary positions and cross-boundary derivatives on the given boundary

  16. Surface Temperature Data Analysis

    Science.gov (United States)

    Hansen, James; Ruedy, Reto

    2012-01-01

    Small global mean temperature changes may have significant to disastrous consequences for the Earth's climate if they persist for an extended period. Obtaining global means from local weather reports is hampered by the uneven spatial distribution of the reliably reporting weather stations. Methods had to be developed that minimize as far as possible the impact of that situation. This software is a method of combining temperature data of individual stations to obtain a global mean trend, overcoming/estimating the uncertainty introduced by the spatial and temporal gaps in the available data. Useful estimates were obtained by the introduction of a special grid, subdividing the Earth's surface into 8,000 equal-area boxes, using the existing data to create virtual stations at the center of each of these boxes, and combining temperature anomalies (after assessing the radius of high correlation) rather than temperatures.

  17. Effective Hydrodynamic Boundary Conditions for Corrugated Surfaces

    CERN Document Server

    Mongruel, Anne; Asmolov, Evgeny S; Vinogradova, Olga I

    2012-01-01

    We report measurements of the hydrodynamic drag force acting on a smooth sphere falling down under gravity to a plane decorated with microscopic periodic grooves. Both surfaces are lyophilic, so that a liquid (silicone oil) invades the surface texture being in the Wenzel state. A significant decrease in the hydrodynamic resistance force as compared with that predicted for two smooth surfaces is observed. To quantify the effect of roughness we use the effective no-slip boundary condition, which is applied at the imaginary smooth homogeneous isotropic surface located at an intermediate position between top and bottom of grooves. Such an effective condition fully characterizes the force reduction measured with the real surface, and the location of this effective plane is related to geometric parameters of the texture by a simple analytical formula.

  18. How will land use affect air temperature in the surface boundary layer? Lessons learned from a comparative study on the energy balance of an oak savanna and annual grassland in California, USA

    Directory of Open Access Journals (Sweden)

    Dennis Baldocchi

    2013-06-01

    Full Text Available We investigated the effect of land use on differences in air temperature. We based our analysis on a decade of weather and energy flux measurements, collected over two contrasting landscapes, an oak savanna and an annual grassland, growing under the same climate conditions. Over the decade, the daily-averaged, potential air temperature above the aerodynamically rougher and optically darker oak savanna was 0.5°C warmer than that above the aerodynamically smoother and optically brighter annual grassland. However, air temperature differences were seasonal. Smallest differences in potential air temperature occurred towards the end of spring, when much of the soil moisture reservoir was depleted. Largest differences in potential air temperature occurred during the winter rain season when the grass was green and transpiring and when the trees were senescent or deciduous. To understand the effect of land use on the local climate, we examined the concomitant changes in net radiation, sensible and latent heat exchange, the aerodynamic roughness (R a, the surface resistance to water transfer (R s, aerodynamic surface temperature and the growth of the planetary boundary layer, with measurements and model computations. Overall, these biophysical variables provide us with mechanistic information to diagnose and predict how changes in air temperature will follow changes in land use or management. In conclusion, land use change is responsible for having a marked impact on the local climate of a region. At the local level, the change in the surface energy balance, towards a darker and rougher surface, will produce an additive increment to climate warming induced by a greater greenhouse gas burden in the atmosphere.

  19. Interaction between surface and atmosphere in a convective boundary layer

    Science.gov (United States)

    Garai, Anirban

    Solar heating of the surface causes the near surface air to warm up and with sufficient buoyancy it ascends through the atmosphere as surface-layer plumes and thermals. The cold fluid from the upper part of the boundary layer descends as downdrafts. The downdrafts and thermals form streamwise roll vortices. All these turbulent coherent structures are important because they contribute most of the momentum and heat transport. While these structures have been studied in depth, their imprint on the surface through energy budget in a convective atmospheric boundary layer has received little attention. The main objective of the present study is to examine the turbulence-induced surface temperature fluctuations for different surface properties and stratification. Experiments were performed to measure atmospheric turbulence using sonic anemometers, fine wire thermocouples and LIDAR; and surface temperature using an infra-red camera over grass and artificial turf fields. The surface temperature fluctuations were found to be highly correlated to the turbulent coherent structures and follow the processes postulated in the surface renewal theory. The spatio-temporal scales and advection speed of the surface temperature fluctuation were found to match with those of turbulent coherent structures. A parametric direct numerical simulation (DNS) study was then performed by solving the solid-fluid heat transport mechanism numerically for varying solid thermal properties, solid thickness and strength of stratification. Even though there were large differences in the friction Reynolds and Richardson numbers between the experiments and numerical simulations, similar turbulent characteristics were observed. The ejection (sweep) events tend to be aligned with the streamwise direction to form roll vortices with unstable stratification. The solid-fluid interfacial temperature fluctuations increase with the decreases in solid thermal inertia; and with the increase in solid thickness to

  20. Infinitesimal nonrigidity of convex surfaces with planar boundary

    Institute of Scientific and Technical Information of China (English)

    LI Chunhe; HONG Jiaxing

    2005-01-01

    In the present paper infinitesimal nonrigidity of a class of convex surfaces with planar boundary is given. This result shows that if the image of the Gauss map of an evolution convex surface with planar boundary covers some hemisphere, this surface may be of infinitesimal nonrigidity for the isometric deformation of planar boundary.

  1. GODAE, SFCOBS - Surface Temperature Observations

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — GODAE, SFCOBS - Surface Temperature Observations: Ship, fixed/drifting buoy, and CMAN in-situ surface temperature. Global Telecommunication System (GTS) Data. The...

  2. Grain boundaries in high temperature superconductors

    NARCIS (Netherlands)

    Hilgenkamp, Johannes W.M.; Mannhart, J.

    2002-01-01

    Since the first days of high-Tc superconductivity, the materials science and the physics of grain boundaries in superconducting compounds have developed into fascinating fields of research. Unique electronic properties, different from those of the grain boundaries in conventional metallic

  3. Primary collector wall local temperature fluctuations in the area of water-steam phase boundary

    Energy Technology Data Exchange (ETDEWEB)

    Matal, O.; Klinga, J.; Simo, T. [Energovyzkum Ltd., Brno (Switzerland)

    1995-12-31

    A limited number of temperature sensors could be installed at the primary collector surface in the area of water - steam phase boundary. The surface temperatures as well WWER 440 steam generator process data were measured and stored for a long time and off-line evaluated. Selected results are presented in the paper. (orig.). 2 refs.

  4. GISS Surface Temperature Analysis

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The GISTEMP dataset is a global 2x2 gridded temperature anomaly dataset. Temperature data is updated around the middle of every month using current data files from...

  5. Local temperature measurement and Kapitza boundary resistance

    NARCIS (Netherlands)

    Maassen van den Brink, A.; Dekker, H.

    1996-01-01

    A calculation of the Kapitza boundary resistance between harmonic solids has been noted previously (Little, Can. J. Phys. 37 (1959) 334; Leung and Young, Phys. Rev. B 36 (1987) 4973) to lead to apparently paradoxical results in the limit of identical solids: instead of vanishing, the resistance tend

  6. Local temperature measurement and Kapitza boundary resistance

    NARCIS (Netherlands)

    Maassen van den Brink, A.; Dekker, H.

    1996-01-01

    A calculation of the Kapitza boundary resistance between harmonic solids has been noted previously (Little, Can. J. Phys. 37 (1959) 334; Leung and Young, Phys. Rev. B 36 (1987) 4973) to lead to apparently paradoxical results in the limit of identical solids: instead of vanishing, the resistance

  7. DYNAMIC SURFACE BOUNDARY-CONDITIONS - A SIMPLE BOUNDARY MODEL FOR MOLECULAR-DYNAMICS SIMULATIONS

    NARCIS (Netherlands)

    JUFFER, AH; BERENDSEN, HJC

    1993-01-01

    A simple model for the treatment of boundaries in molecular dynamics simulations is presented. The method involves the positioning of boundary atoms on a surface that surrounds a system of interest. The boundary atoms interact with the inner region and represent the effect of atoms outside the surfa

  8. Spatial heterogeneity of ocean surface boundary conditions under sea ice

    Science.gov (United States)

    Barthélemy, Antoine; Fichefet, Thierry; Goosse, Hugues

    2016-06-01

    The high heterogeneity of sea ice properties implies that its effects on the ocean are spatially variable at horizontal scales as small as a few meters. Previous studies have shown that taking this variability into account in models could be required to simulate adequately mixed layer processes and the upper ocean temperature and salinity structures. Although many advanced sea ice models include a subgrid-scale ice thickness distribution, potentially providing heterogeneous surface boundary conditions, the information is lost in the coupling with a unique ocean grid cell underneath. The present paper provides a thorough examination of boundary conditions at the ocean surface in the NEMO-LIM model, which can be used as a guideline for studies implementing subgrid-scale ocean vertical mixing schemes. Freshwater, salt, solar heat and non-solar heat fluxes are examined, as well as the norm of the surface stress. All of the thermohaline fluxes vary considerably between the open water and ice fractions of grid cells. To a lesser extent, this is also the case for the surface stress. Moreover, the salt fluxes in both hemispheres and the solar heat fluxes in the Arctic show a dependence on the ice thickness category, with more intense fluxes for thinner ice, which promotes further subgrid-scale heterogeneity. Our analysis also points out biases in the simulated open water fraction and in the ice thickness distribution, which should be investigated in more details in order to ensure that the latter is used to the best advantage.

  9. Temperature dependence of surface nanobubbles

    NARCIS (Netherlands)

    Berkelaar, R.P.; Seddon, James Richard Thorley; Zandvliet, Henricus J.W.; Lohse, Detlef

    2012-01-01

    The temperature dependence of nanobubbles was investigated experimentally using atomic force microscopy. By scanning the same area of the surface at temperatures from 51 °C to 25 °C it was possible to track geometrical changes of individual nanobubbles as the temperature was decreased.

  10. Hydrodynamic Boundary Conditions and Dynamic Forces between Bubbles and Surfaces

    Science.gov (United States)

    Manor, Ofer; Vakarelski, Ivan U.; Tang, Xiaosong; O'Shea, Sean J.; Stevens, Geoffrey W.; Grieser, Franz; Dagastine, Raymond R.; Chan, Derek Y. C.

    2008-07-01

    Dynamic forces between a 50μm radius bubble driven towards and from a mica plate using an atomic force microscope in electrolyte and in surfactant exhibit different hydrodynamic boundary conditions at the bubble surface. In added surfactant, the forces are consistent with the no-slip boundary condition at the mica and bubble surfaces. With no surfactant, a new boundary condition that accounts for the transport of trace surface impurities explains variations of dynamic forces at different speeds and provides a direct connection between dynamic forces and surface transport effects at the air-water interface.

  11. SurfCut: Free-Boundary Surface Extraction

    KAUST Repository

    Algarni, Marei

    2016-09-15

    We present SurfCut, an algorithm for extracting a smooth simple surface with unknown boundary from a noisy 3D image and a seed point. In contrast to existing approaches that extract smooth simple surfaces with boundary, our method requires less user input, i.e., a seed point, rather than a 3D boundary curve. Our method is built on the novel observation that certain ridge curves of a front propagated using the Fast Marching algorithm are likely to lie on the surface. Using the framework of cubical complexes, we design a novel algorithm to robustly extract such ridge curves and form the surface of interest. Our algorithm automatically cuts these ridge curves to form the surface boundary, and then extracts the surface. Experiments show the robustness of our method to errors in the data, and that we achieve higher accuracy with lower computational cost than comparable methods. © Springer International Publishing AG 2016.

  12. Turbulent Boundary Layer Flow over Superhydrophobic Surfaces

    Science.gov (United States)

    2013-05-10

    Figure 1 were a highly viscous fluid, such as honey , the boundary layer would be thick while if the fluid were water, a low-viscosity fluid, the boundary...drag has become even more important. In response to this need, and with the benefit of modern technology, the drag-reduction field is replete with...manufactured with “riblets,” small ridges on the order of fractions of millimeters, built-into the hull or skin that seek to reduce frictional drag. The

  13. Modelling near subsurface temperature with mixed type boundary condition for transient air temperature and vertical groundwater flow

    Indian Academy of Sciences (India)

    Rajeev Ranjan Kumar; D V Ramana; R N Singh

    2012-10-01

    Near-subsurface temperatures have signatures of climate change. Thermal models of subsurface have been constructed by prescribing time dependent Dirichlet type boundary condition wherein the temperature at the soil surface is prescribed and depth distribution of temperature is obtained. In this formulation it is not possible to include the relationship between air temperatures and the temperature of soil surface. However, if one uses a Robin type boundary condition, a transfer coefficient relates the air and soil surface temperatures which helps to determine both the temperature at the surface and at depth given near surface air temperatures. This coefficient is a function of meteorological conditions and is readily available. We have developed such a thermal model of near subsurface region which includes both heat conduction and advection due to groundwater flows and have presented numerical results for changes in the temperature–depth profiles for different values of transfer coefficient and groundwater flux. There are significant changes in temperature and depth profiles due to changes in the transfer coefficient and groundwater flux. The analytical model will find applications in the interpretation of the borehole geothermal data to extract both climate and groundwater flow signals.

  14. Surface and grain boundary scattering in nanometric Cu thin films: A quantitative analysis including twin boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Barmak, Katayun [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 and Department of Materials Science and Engineering and Materials Research Science and Engineering Center, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Darbal, Amith [Department of Materials Science and Engineering and Materials Research Science and Engineering Center, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Ganesh, Kameswaran J.; Ferreira, Paulo J. [Materials Science and Engineering, The University of Texas at Austin, 1 University Station, Austin, Texas 78712 (United States); Rickman, Jeffrey M. [Department of Materials Science and Engineering and Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015 (United States); Sun, Tik; Yao, Bo; Warren, Andrew P.; Coffey, Kevin R., E-mail: kb2612@columbia.edu [Department of Materials Science and Engineering, University of Central Florida, 4000 Central Florida Boulevard, Orlando, Florida 32816 (United States)

    2014-11-01

    The relative contributions of various defects to the measured resistivity in nanocrystalline Cu were investigated, including a quantitative account of twin-boundary scattering. It has been difficult to quantitatively assess the impact twin boundary scattering has on the classical size effect of electrical resistivity, due to limitations in characterizing twin boundaries in nanocrystalline Cu. In this study, crystal orientation maps of nanocrystalline Cu films were obtained via precession-assisted electron diffraction in the transmission electron microscope. These orientation images were used to characterize grain boundaries and to measure the average grain size of a microstructure, with and without considering twin boundaries. The results of these studies indicate that the contribution from grain-boundary scattering is the dominant factor (as compared to surface scattering) leading to enhanced resistivity. The resistivity data can be well-described by the combined Fuchs–Sondheimer surface scattering model and Mayadas–Shatzkes grain-boundary scattering model using Matthiessen's rule with a surface specularity coefficient of p = 0.48 and a grain-boundary reflection coefficient of R = 0.26.

  15. Variations of Boundary Surface in Chua’s Circuit

    Directory of Open Access Journals (Sweden)

    M. Guzan

    2015-09-01

    Full Text Available The paper compares the boundary surfaces with help of cross-sections in three projection planes, for the four changes of Chua’s circuit parameters. It is known that due to changing the parameters, the Chua’s circuit can be characterized in addition to a stable limit cycle also by one double scroll chaotic attractor, two single scroll chaotic attractors or other two stable limit cycles. Chua’s circuit can even start working as a binary memory. It is not known yet, how changes in parameters and conseqently in attractors in the circuit will affect the morphology of the boundary surface. The boundary surface separates the double scroll chaotic attractor from the stable limit cycle. In a variation of the parameters presented in this paper the boundary surface will separate even single scroll chaotic attractors from each other. Dividing the state space into regions of attractivity for different attractors, however, remains fundamentally the same.

  16. Fiber optic distributed temperature sensing for the determination of the nocturnal atmospheric boundary layer height

    Directory of Open Access Journals (Sweden)

    C. A. Keller

    2010-06-01

    Full Text Available A new method for measuring air temperature profiles in the atmospheric boundary layer at high spatial and temporal resolution is presented. The measurements are based on Raman scattering distributed temperature sensing (DTS with a fiber optic cable attached to a tethered balloon. These data were used to estimate the height of the stable nocturnal boundary layer. The experiment was successfully deployed during a two-day campaign in September 2009, providing evidence that DTS is well suited for this atmospheric application. Observed stable temperature profiles exhibit an exponential shape confirming similarity concepts of the temperature inversion close to the surface. The atmospheric mixing height (MH was estimated to vary between 5 m and 50 m as a result of the nocturnal boundary layer evolution. This value is in good agreement to the MH derived from concurrent Radon-222 (222Rn measurements and in previous studies.

  17. Fiber optic distributed temperature sensing for the determination of the nocturnal atmospheric boundary layer height

    Directory of Open Access Journals (Sweden)

    C. A. Keller

    2011-02-01

    Full Text Available A new method for measuring air temperature profiles in the atmospheric boundary layer at high spatial and temporal resolution is presented. The measurements are based on Raman scattering distributed temperature sensing (DTS with a fiber optic cable attached to a tethered balloon. These data were used to estimate the height of the stable nocturnal boundary layer. The experiment was successfully deployed during a two-day campaign in September 2009, providing evidence that DTS is well suited for this atmospheric application. Observed stable temperature profiles exhibit an exponential shape confirming similarity concepts of the temperature inversion close to the surface. The atmospheric mixing height (MH was estimated to vary between 5 m and 50 m as a result of the nocturnal boundary layer evolution. This value is in good agreement with the MH derived from concurrent Radon-222 (222Rn measurements and in previous studies.

  18. Surface modes in sheared boundary layers over impedance linings

    Science.gov (United States)

    Brambley, E. J.

    2013-08-01

    Surface modes, being duct modes localized close to the duct wall, are analysed within a lined cylindrical duct with uniform flow apart from a thin boundary layer. As well as full numerical solutions of the Pridmore-Brown equation, simplified mathematical models are given where the duct lining and boundary layer are lumped together and modelled using a single boundary condition (a modification of the Myers boundary condition previously proposed by the author), from which a surface mode dispersion relation is derived. For a given frequency, up to six surface modes are shown to exist, rather than the maximum of four for uniform slipping flow. Not only is the different number and behaviour of surface modes important for frequency-domain mode-matching techniques, which depend on having found all relevant modes during matching, but the thin boundary layer is also shown to lead to different convective and absolute stability than for uniform slipping flow. Numerical examples are given comparing the predictions of the surface mode dispersion relation to full solutions of the Pridmore-Brown equation, and the accuracy with which surface modes are predicted is shown to be significantly increased compared with the uniform slipping flow assumption. The importance of not only the boundary layer thickness but also its profile (tanh or linear) is demonstrated. A Briggs-Bers stability analysis is also performed under the assumption of a mass-spring-damper or Helmholtz resonator impedance model.

  19. Interpolated lattice Boltzmann boundary conditions for surface reaction kinetics.

    Science.gov (United States)

    Walsh, S D C; Saar, M O

    2010-12-01

    This paper describes a method for implementing surface reaction kinetics in lattice Boltzmann simulations. The interpolated boundary conditions are capable of simulating surface reactions and dissolution at both stationary and moving solid-fluid and fluid-fluid interfaces. Results obtained with the boundary conditions are compared to analytical solutions for first-order and constant-flux kinetic surface reactions in a one-dimensional half space, as well as to the analytical solution for evaporation from the surface of a cylinder. Excellent agreement between analytical and simulated results is obtained for a wide range of diffusivities, lattice velocities, and surface reaction rates. The boundary model's ability to represent dissolution in binary fluid mixtures is demonstrated by modeling diffusion from a rising bubble and dissolution of a droplet near a flat plate.

  20. The surface temperature of Europa

    CERN Document Server

    Ashkenazy, Yosef

    2016-01-01

    Previous estimates of the surface temperature of Jupiter's moon, Europa, neglected the effect of the eccentricity of Jupiter's orbit around the Sun, the effect of the eclipse of Europa (i.e., the relative time that Europa is within the shadow of Jupiter), and the effect of Europa's internal heating. Here we estimate the surface temperature of Europa, when Europa's obliquity, eclipse and internal heating, as well as the eccentricity of Jupiter, are all taken into account. For a typical internal heating rate of 0.05 W/m$^2$ (corresponding to an ice thickness of about 10 kms), the equator, pole, and global mean surface temperatures are 101.7 K, 45.26 K, and 94.75 K, respectively. We found that the temperature at the high latitudes is significantly affected by the internal heating. We also studied the effect of the internal heating on the mean thickness of Europa's icy shell and conclude that the polar region temperature can be used to constrain the internal heating and the depth of the ice. Our approach and form...

  1. Molecular dynamics study of grain boundary structure and properties at high temperatures

    Science.gov (United States)

    Fensin, Saryu Jindal

    This thesis reports research involving the development and application of atomistic simulation methods to study the effects of high homologous temperatures on the structural, thermodynamic, kinetic and mechanical properties of grain boundaries in metals. Our interest in these properties is due to the role they play in governing the evolution of microstructure and deformation of metals during solidification processing. The interest in developing more predictive models for the formation of solidification defects highlights a need to better understand the thermodynamic driving forces underlying grain-boundary premelting and the mobility and shear strength of these interfaces at high temperatures. In this work we study two different elemental systems, namely Ni and Cu, and consider a variety of grain boundary structures characterized by different misorientation angles, twist/tilt character and zero-temperature energies. A method to calculate the disjoining potential from molecular dynamics (MD) is developed and applied to grain boundaries in Ni. The disjoining potential characterizes the variation in grain-boundary free energy as a function of the width of a premelted interfacial layer. The MD method for the calculation of this property is applied to grain boundaries that display continuous premelting transitions, as well as a boundary characterized by a disordered atomic structure displaying a finite interfacial width at the melting temperature. The disjoining potential represents an important input property to larger scale models of solidification and grain coalescence. We further develop analysis methods to characterize the change in the atomic structure of an asymmetric tilt grain boundary in elemental Cu as a function of temperature. This boundary is characterized by a potential-energy surface with multiple minima as a function of the relative translation of the grains parallel to the interface plane. The more complex structure of this boundary, relative to the

  2. Surface transition on ice induced by the formation of a grain boundary.

    Directory of Open Access Journals (Sweden)

    Christian Pedersen

    Full Text Available Interfaces between individual ice crystals, usually referred to as grain boundaries, play an important part in many processes in nature. Grain boundary properties are, for example, governing the sintering processes in snow and ice which transform a snowpack into a glacier. In the case of snow sintering, it has been assumed that there are no variations in surface roughness and surface melting, when considering the ice-air interface of an individual crystal. In contrast to that assumption, the present work suggests that there is an increased probability of molecular surface disorder in the vicinity of a grain boundary. The conclusion is based on the first detailed visualization of the formation of an ice grain boundary. The visualization is enabled by studying ice crystals growing into contact, at temperatures between -20°C and -15°C and pressures of 1-2 Torr, using Environmental Scanning Electron Microscopy. It is observed that the formation of a grain boundary induces a surface transition on the facets in contact. The transition does not propagate across facet edges. The surface transition is interpreted as the spreading of crystal dislocations away from the grain boundary. The observation constitutes a qualitatively new finding, and can potentially increase the understanding of specific processes in nature where ice grain boundaries are involved.

  3. On the compressibility and temperature boundary of warm frozen soils

    Science.gov (United States)

    Qi, Jilin; Dang, Boxiang; Guo, Xueluan; Sun, Xiaoyu; Yan, Xu

    2017-04-01

    A silty-clay obtained along the Qinghai-Tibetan railway and a standard Chinese sand were taken as study objects. Saturated frozen soil samples were prepared for testing. Step-load was used and confined compression was carried out on the soils under different temperatures. Compression index and pseudo-preconsolidation pressure (PPC) were obtained. Unlike unfrozen soils, PPC is not associated with stress history. However, it is still the boundary of elastic and plastic deformations. Different compression indexes can be obtained from an individual compression curve under pressures before and after PPC. The parameters at different thermal and stress conditions were analyzed. It is found that temperature plays a critical role in mechanical behaviours of frozen soils. Efforts were then made on the silty-clay in order to suggest a convincing temperature boundary in defining warm frozen soil. Three groups of ice-rich samples with different ice contents were prepared and tested under confined compression. The samples were compressed under a constant load and with 5 stepped temperatures. Strain rates at different temperatures were examined. It was found that the strain rate at around -0.6°C increased abruptly. Analysis of compression index was performed on the data both from our own testing program and from the literature, which showed that at about -1°C was a turning point in the curves for compression index against temperature. Based on both our work and taking into account the unfrozen water content vs. temperature, the range of -1°C to -0.5°C seems to be the temperature where the mechanical properties change greatly. For convenience, -1.0°C can be defined as the boundary for warm frozen soils.

  4. A model of the planetary boundary layer over a snow surface

    Science.gov (United States)

    Halberstam, I.; Melendez, R.

    1979-01-01

    A model of the planetary boundary layer over a snow surface has been developed. It contains the vertical heat exchange processes due to radiation, conduction, and atmospheric turbulence. Parametrization of the boundary layer is based on similarity functions developed by Hoffert and Sud (1976), which involve a dimensionless variable, dependent on boundary-layer height and a localized Monin-Obukhov length. The model also contains the atmospheric surface layer and the snowpack itself, where snowmelt and snow evaporation are calculated. The results indicate a strong dependence of surface temperatures, especially at night, on the bursts of turbulence which result from the frictional damping of surface-layer winds during periods of high stability, as described by Businger (1973). The model also shows the cooling and drying effect of the snow on the atmosphere, which may be the mechanism for air mass transformation in sub-Arctic regions.

  5. Laminar mixed convection boundary layer flow induced by a permeable surface stretched with prescribed skin friction boundary conditions

    Directory of Open Access Journals (Sweden)

    Mohamed Ali

    2015-09-01

    Full Text Available The mixed laminar boundary layer flow and heat transfer on a permeable stretched surface moving with prescribed skin friction are studied. Three major cases, which correspond to complete similarity solutions, are considered. The cases are combinations of power law indices n and m representing temperature and skin friction distributions, respectively. The first case (n = 0, m = 0.5 corresponds to isothermal stretched surface with skin friction at the surface scales as x 1/4. The second case (n = 1, m = 1 is a linear temperature and skin friction distribution along the vertical stretched surface. The third case (n = −1, m = 0 represents inverse temperature variation along the surface with prescribed skin friction of the order of x −1/2. Similarity solutions are obtained for the surface stretched in a stagnant air with Prandtl number = 0.72. The effect of suction/injection velocity (fw and the buoyancy parameter (λ is studied in detail. The results show that the heat transfer coefficient along the surface is enhanced for assisting flow (λ > 0 at any value of fw for the first and second cases, while it is reduced for the third case. However, the opposite is true for the opposing flow (λ < 0. Furthermore, suction enhances the heat transfer coefficient, whereas injection degrades it at any fixed λ for the first and second prescribed skin friction boundary conditions, and the opposite is true for the third case.

  6. Body surface adaptations to boundary-layer dynamics.

    Science.gov (United States)

    Videler, J J

    1995-01-01

    Evolutionary processes have adapted nektonic animals to interact efficiently with the water that surrounds them. Not all these adaptations serve the same purpose. This paper concentrates on reduction of drag due to friction in the boundary layer close to the body surface. Mucus, compliant skins, scales, riblets and roughness may influence the flow velocity gradient, the type of flow and the thickness of the boundary layer around animals, and may seriously affect their drag in a positive or negative way. The long-chain polymers found in mucus decrease the pressure gradient and considerably reduced drag due to friction. The effect is probably due to channelling of the flow particles in the direction of the main flow, resulting in a reduction of turbulence. Compliant surfaces could probably reduce drag by equalising and distributing pressure pulses. However, the existing evidence that drag reduction actually occurs is not convincing. There is no indication that instantaneous heating, reducing the viscosity in the boundary layer, is used by animals as a drag-reducing technique. Small longitudinal ridges on rows of scales on fish can reduce shear stress in the boundary by a maximum of 10% compared with the shear stress of a smooth surface. The mechanism is based on the impedance of cross flow under well-defined conditions. The effect has been visualized with the use of particle image velocimetry techniques. The function of the swords and spears of several fast, pelagic, predatory fish species is still enigmatic. The surface structure of the sword of a swordfish is shown to be both rough and porous. The height of the roughness elements on the tip of the sword is close to the critical value for the induction of a laminar-to-turbulent flow transition at moderate cruising speeds. A flow tank is described that is designed to visualize the effects of surface imperfections on flow in the boundary layer in direct comparison with a smooth flat wall. The flow in a 1 m long, 10 cm

  7. Impact of Surface Chemistry on Grain Boundary Induced Intrinsic Stress Evolution during Polycrystalline Thin Film Growth

    Science.gov (United States)

    Qi, Y.; Sheldon, B. W.; Guo, H.; Xiao, X.; Kothari, A. K.

    2009-02-01

    First principles calculations were integrated with cohesive zone and growth chemistry models to demonstrate that adsorbed species can significantly alter stresses associated with grain boundary formation during polycrystalline film growth. Using diamond growth as an example, the results show that lower substrate temperatures increase the hydrogen content at the surface, which reduces tensile stress, widens the grain boundary separations, and permits additional atom insertions that can induce compressive stress. More generally, this work demonstrates that surface heteroatoms can lead to behavior which is not readily described by existing models of intrinsic stress evolution.

  8. Boundary conditions for soft glassy flows: slippage and surface fluidization.

    Science.gov (United States)

    Mansard, Vincent; Bocquet, Lydéric; Colin, Annie

    2014-09-28

    We explore the question of surface boundary conditions for the flow of a dense emulsion. We make use of microlithographic tools to create surfaces with well controlled roughness patterns and measure using dynamic confocal microscopy both the slip velocity and the shear rate close to the wall, which we relate to the notion of surface fluidization. Both slippage and wall fluidization depend non-monotonously on the roughness. We interpret this behavior within a simple model in terms of the building of a stratified layer and the activation of plastic events by the surface roughness.

  9. Body surface adaptations to boundary-layer dynamics

    NARCIS (Netherlands)

    Videler, J.J.

    1995-01-01

    Evolutionary processes have adapted nektonic animals to interact efficiently with the water that surrounds them. Not all these adaptations serve the same purpose. This paper concentrates on reduction of drag due to friction in the boundary layer close to the body surface. Mucus, compliant skins, sca

  10. Heat Flow for the Minimal Surface with Plateau Boundary Condition

    Institute of Scientific and Technical Information of China (English)

    Kung Ching CHANG; Jia Quan LIU

    2003-01-01

    The heat flow for the minimal surface under Plateau boundary condition is defined to be aparabolic variational inequality, and then the existence, uniqueness, regularity, continuous dependenceon the initial data and the asymptotics are studied. It is applied as a deformation of the level sets inthe critical point theory.

  11. Body surface adaptations to boundary-layer dynamics

    NARCIS (Netherlands)

    Videler, J.J.

    1995-01-01

    Evolutionary processes have adapted nektonic animals to interact efficiently with the water that surrounds them. Not all these adaptations serve the same purpose. This paper concentrates on reduction of drag due to friction in the boundary layer close to the body surface. Mucus, compliant skins,

  12. Convective boundary layers driven by nonstationary surface heat fluxes

    NARCIS (Netherlands)

    Van Driel, R.; Jonker, H.J.J.

    2011-01-01

    In this study the response of dry convective boundary layers to nonstationary surface heat fluxes is systematically investigated. This is relevant not only during sunset and sunrise but also, for example, when clouds modulate incoming solar radiation. Because the time scale of the associated change

  13. Hydrodynamic boundary condition of water on hydrophobic surfaces.

    Science.gov (United States)

    Schaeffel, David; Yordanov, Stoyan; Schmelzeisen, Marcus; Yamamoto, Tetsuya; Kappl, Michael; Schmitz, Roman; Dünweg, Burkhard; Butt, Hans-Jürgen; Koynov, Kaloian

    2013-05-01

    By combining total internal reflection fluorescence cross-correlation spectroscopy with Brownian dynamics simulations, we were able to measure the hydrodynamic boundary condition of water flowing over a smooth solid surface with exceptional accuracy. We analyzed the flow of aqueous electrolytes over glass coated with a layer of poly(dimethylsiloxane) (advancing contact angle Θ = 108°) or perfluorosilane (Θ = 113°). Within an error of better than 10 nm the slip length was indistinguishable from zero on all surfaces.

  14. A unified slip boundary condition for flow over a surface

    CERN Document Server

    Thalakkottor, Joseph John

    2015-01-01

    Interface between two phases of matter are ubiquitous in nature and technology. Determining the correct velocity condition at an interface is essential for understanding and designing of flows over a surface. We demonstrate that both the widely used no-slip and the Navier and Maxwell slip boundary conditions do not capture the complete physics associated with complex problems, such as spreading of liquids or corner flows. Hence, we present a unified boundary condition that is applicable to a wide-range of flow problems.

  15. Viscous boundary lubrication of hydrophobic surfaces by mucin.

    Science.gov (United States)

    Yakubov, Gleb E; McColl, James; Bongaerts, Jeroen H H; Ramsden, Jeremy J

    2009-02-17

    The lubricating behavior of the weakly charged short-side-chain glycoprotein mucin "Orthana" (Mw=0.55 MDa) has been investigated between hydrophobic and hydrophilic PDMS substrates using soft-contact tribometry. It was found that mucin facilitates lubrication between hydrophobic PDMS surfaces, leading to a 10-fold reduction in boundary friction coefficient for rough surfaces. The presence of mucin also results in a shift of the mixed lubrication regime to lower entrainment speeds. The observed boundary lubrication behavior of mucin was found to depend on the bulk concentration, and we linked this to the structure and dynamics of the adsorbed mucin films, which are assessed using optical waveguide light spectroscopy. We observe a composite structure of the adsorbed mucin layer, with its internal structure governed by entanglement. The film thickness of this adsorbed layer increases with concentration, while the boundary friction coefficient for rough surfaces was found to be inversely proportional to the thickness of the adsorbed film. This link between lubrication and structure of the film is consistent with a viscous boundary lubrication mechanism, i.e., a thicker adsorbed film, at a given sliding speed, results in a lower local shear rate and, hence, in a lower local shear stress. The estimated local viscosities of the adsorbed layer, derived from the friction measurements and the polymer layer density, are in agreement with each other.

  16. Extended Reconstructed Sea Surface Temperature (ERSST)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Extended Reconstructed Sea Surface Temperature (ERSST) dataset is a global monthly sea surface temperature analysis derived from the International Comprehensive...

  17. NOAA Global Surface Temperature (NOAAGlobalTemp)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Global Surface Temperature Dataset (NOAAGlobalTemp) is a merged land–ocean surface temperature analysis (formerly known as MLOST) (link is external). It is...

  18. Thermocouple Rakes for Measuring Boundary Layer Flows Extremely Close to Surface

    Science.gov (United States)

    Hwang, Danny P.; Fralick, Gustave C.; Martin, Lisa C.; Blaha, Charles A.

    2001-01-01

    Of vital interest to aerodynamic researchers is precise knowledge of the flow velocity profile next to the surface. This information is needed for turbulence model development and the calculation of viscous shear force. Though many instruments can determine the flow velocity profile near the surface, none of them can make measurements closer than approximately 0.01 in. from the surface. The thermocouple boundary-layer rake can measure much closer to the surface than conventional instruments can, such as a total pressure boundary layer rake, hot wire, or hot film. By embedding the sensors (thermocouples) in the region where the velocity is equivalent to the velocity ahead of a constant thickness strut, the boundary-layer flow profile can be obtained. The present device fabricated at the NASA Glenn Research Center microsystem clean room has a heater made of platinum and thermocouples made of platinum and gold. Equal numbers of thermocouples are placed both upstream and downstream of the heater, so that the voltage generated by each pair at the same distance from the surface is indicative of the difference in temperature between the upstream and downstream thermocouple locations. This voltage differential is a function of the flow velocity, and like the conventional total pressure rake, it can provide the velocity profile. In order to measure flow extremely close to the surface, the strut is made of fused quartz with extremely low heat conductivity. A large size thermocouple boundary layer rake is shown in the following photo. The latest medium size sensors already provide smooth velocity profiles well into the boundary layer, as close as 0.0025 in. from the surface. This is about 4 times closer to the surface than the previously used total pressure rakes. This device also has the advantage of providing the flow profile of separated flow and also it is possible to measure simultaneous turbulence levels within the boundary layer.

  19. Excitation of surface plasmons at the boundary of overdense plasma

    Institute of Scientific and Technical Information of China (English)

    Wang Liang; Cao Jin-Xiang; Wang Yan; Niu Tian-Ye; Liu Lei; Lü You

    2008-01-01

    The excitation of surface plasmons (SPs) with a strip grating at the boundary of an unmagnetized overdense plasma has been investigated theoretically and experimentally. An incident electromagnetic radiation was p-polarized at the frequency of 5 GHz. Experiments showed that when the plasma density was four times higher than the critical density with the grating present, and the SPs could be excited at the boundary of the overdense plasma. Contribution of the glass layer in the formation of the SP dispersion relation was examined. When the incident electromagnetic radiation was coupled into SPs the coupling order with the effective permittivity was simulated qualitatively. We find that the existence of SPs at the boundary of overdense plasma indicates that the reflection coefficient of the incident electromagnetic radiation reaches its minimum and even becomes total absorption. In this work the plasma density was diagnosed by a Langmuir double probe.

  20. Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

    Directory of Open Access Journals (Sweden)

    N. A. Brunsell

    2010-07-01

    Full Text Available The role of land-atmosphere interactions under heterogeneous surface conditions is investigated in order to identify mechanisms responsible for altering surface heat and moisture fluxes. Twelve coupled land surface – large eddy simulation scenarios with four different length scales of surface variability under three different horizontal wind speeds are used in the analysis. The base case uses Landsat ETM imagery over the Cloud Land Surface Interaction Campaign (CLASIC field site for 3 June 2007. Using wavelets, the surface fields are band-pass filtered in order to maintain the spatial mean and variances to length scales of 200 m, 1600 m, and 12.8 km as lower boundary conditions to the model. The simulations exhibit little variation in net radiation. Rather, a change in the partitioning of the surface energy between sensible and latent heat flux is responsible for differences in boundary layer dynamics. The sensible heat flux is dominant for intermediate surface length scales. For smaller and larger scales of surface heterogeneity, which can be viewed as being more homogeneous, the latent heat flux becomes increasingly important. The results reflect a general decrease of the Bowen ratio as the surface conditions transition from heterogeneous to homogeneous. Air temperature is less sensitive to surface heterogeneity than water vapor, which implies that the role of surface heterogeneity in modifying the local temperature gradients in order to maximize convective heat fluxes. More homogeneous surface conditions, on the other hand, tend to maximize latent heat flux. Scalar vertical profiles respond predictably to the partitioning of surface energy. Fourier spectra of the vertical wind speed, air temperature and specific humidity (w, T and q and associated cospectra (w'T', w'q' and T'q', however, are insensitive to the length scale of surface heterogeneity, but the near surface spectra are sensitive to the

  1. Tile Surface Thermocouple Measurement Challenges from the Orbiter Boundary Layer Transition Flight Experiment

    Science.gov (United States)

    Campbell, Charles H.; Berger, Karen; Anderson, Brian

    2012-01-01

    Hypersonic entry flight testing motivated by efforts seeking to characterize boundary layer transition on the Space Shuttle Orbiters have identified challenges in our ability to acquire high quality quantitative surface temperature measurements versus time. Five missions near the end of the Space Shuttle Program implemented a tile surface protuberance as a boundary layer trip together with tile surface thermocouples to capture temperature measurements during entry. Similar engineering implementations of these measurements on Discovery and Endeavor demonstrated unexpected measurement voltage response during the high heating portion of the entry trajectory. An assessment has been performed to characterize possible causes of the issues experienced during STS-119, STS-128, STS-131, STS-133 and STS-134 as well as similar issues encountered during other orbiter entries.

  2. Modeling Turbulence Generation in the Atmospheric Surface and Boundary Layers

    Science.gov (United States)

    2015-10-01

    index. In the boundary layer, atmospheric temperature fluctuations are primarily responsible for the variations in refractive index at ultraviolet...parameterization of the atmospheric emissivity, in the early 1980s a parallel study of the SEB was conducted by the US Army Waterways Experiment Station...period of rotation of the atmosphere can be defined as TI = 2π/fc. At most mid- latitude locations this period is approximately 17 h. This quantity is

  3. A Boundary Condition for Simulation of Flow Over Porous Surfaces

    Science.gov (United States)

    Frink, Neal T.; Bonhaus, Daryl L.; Vatsa, Veer N.; Bauer, Steven X. S.; Tinetti, Ana F.

    2001-01-01

    A new boundary condition is presented.for simulating the flow over passively porous surfaces. The model builds on the prior work of R.H. Bush to eliminate the need for constructing grid within an underlying plenum, thereby simplifying the numerical modeling of passively porous flow control systems and reducing computation cost. Code experts.for two structured-grid.flow solvers, TLNS3D and CFL3D. and one unstructured solver, USM3Dns, collaborated with an experimental porosity expert to develop the model and implement it into their respective codes. Results presented,for the three codes on a slender forebody with circumferential porosity and a wing with leading-edge porosity demonstrate a good agreement with experimental data and a remarkable ability to predict the aggregate aerodynamic effects of surface porosity with a simple boundary condition.

  4. Combined measurement of surface, grain boundary and lattice diffusion coefficients on olivine bi-crystals

    Science.gov (United States)

    Marquardt, Katharina; Dohmen, Ralf; Wagner, Johannes

    2014-05-01

    Diffusion along interface and grain boundaries provides an efficient pathway and may control chemical transport in rocks as well as their mechanical strength. Besides the significant relevance of these diffusion processes for various geologic processes, experimental data are still very limited (e.g., Dohmen & Milke, 2010). Most of these data were measured using polycrystalline materials and the formalism of LeClaire (1951) to fit integrated concentration depth profiles. To correctly apply this formalism, certain boundary conditions of the diffusion problem need to be fulfilled, e.g., surface diffusion is ignored, and furthermore the lattice diffusion coefficient has to be known from other studies or is an additional fitting parameter, which produces some ambiguity in the derived grain boundary diffusion coefficients. We developed an experimental setup where we can measure the lattice and grain boundary diffusion coefficients simultaneously but independent and demonstrate the relevance of surface diffusion for typical grain boundary diffusion experiments. We performed Mg2SiO4 bicrystal diffusion experiments, where a single grain boundary is covered by a thin-film of pure Ni2SiO4 acting as diffusant source, produced by pulsed laser deposition. The investigated grain boundary is a 60° (011)/[100]. This specific grain boundary configuration was modeled using molecular dynamics for comparison with the experimental observations in the transmission electron microscope (TEM). Both, experiment and model are in good agreement regarding the misorientation, whereas there are still some disagreements regarding the strain fields along the grain boundary that are of outmost importance for the strengths of the material. The subsequent diffusion experiments were carried out in the temperature range between 800° and 1450° C. The inter diffusion profiles were measured using the TEMs energy dispersive x-ray spectrometer standardized using the Cliff-Lorimer equation and EMPA

  5. The Pacific sea surface temperature

    Energy Technology Data Exchange (ETDEWEB)

    Douglass, David H., E-mail: douglass@pas.rochester.edu [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171 (United States)

    2011-12-05

    The Pacific sea surface temperature data contains two components: N{sub L}, a signal that exhibits the familiar El Niño/La Niña phenomenon and N{sub H}, a signal of one-year period. Analysis reveals: (1) The existence of an annual solar forcing F{sub S}; (2) N{sub H} is phase locked directly to F{sub S} while N{sub L} is frequently phase locked to the 2nd or 3rd subharmonic of F{sub S}. At least ten distinct subharmonic time segments of N{sub L} since 1870 are found. The beginning or end dates of these segments have a near one-to-one correspondence with the abrupt climate changes previously reported. Limited predictability is possible. -- Highlights: ► El Niño/La Niña consists of 2 components phase-locked to annual solar cycle. ► The first component N{sub L} is the familiar El Niño/La Niña effect. ► The second N{sub H} component has a period of 1 cycle/year. ► N{sub L} can be phase-locked to 2nd or 3rd subharmonic of annual cycle. ► Ends of phase-locked segments correspond to abrupt previously reported climate changes.

  6. Electrochemical and Numerical Studies of Surface, Grain-Boundary and Bulk Copper Diffusion Into Gold

    Science.gov (United States)

    Miller, Eric Todd

    Surface, grain-boundary, and bulk chemical diffusivities of copper into gold were measured by chronoamperometry -potentiometry applied to Cu|CuCl |Au solid state galvanic cells at 300-400^circC. The cells were constructed using a novel vapor deposition technique which is described. The automated data acquisition techniques utilizing unique hardware and custom designed software are also presented. Chronoamperometry and a two electrode limited potential cyclic voltammetry technique were comparatively used to determine cell capacitance and resistance. Both gave similar RC values at lower temperatures but diverged from each other at higher temperatures. Electron hole conductivity of CuCl could not be determined from intercept values in the chronoamperometry Cottrell analysis. The partial molar enthalpy and entropy of mixing copper into gold were determined from Emf vs temperature vs composition measurements of Cu|CuCl |Au-Cu alloy cells. The results support the regular solution model of mixing with interaction energy parameter {bf{cal Q}} = 10kJ. Diffusion coefficients were calculated from the chronoamperometry-potentiometry time/flux/concentration data in two ways: via the Cottrell equation, for an average diffusion coefficient; and via a simplex and finite difference program for the simultaneous determination of surface, grain-boundary, and bulk diffusion coefficients. This program was run on a MASPAR MP-2 massively parallel computer. The surface and grain-boundary diffusivities were numerically determinable in single and polycrystalline cathodes at short diffusion times. Bulk diffusivity was determinable at short and long diffusion times and agreed with previous data. Surface diffusivity was two orders of magnitude larger than the bulk with lower activation energy. Grain -boundary diffusivity was one order of magnitude larger than the bulk with similar activation energy. The Cottrell equation was only valid at very long diffusion times due to the transient interface

  7. Effect of non-uniform basic temperature gradients on Marangoni convection with a boundary slab of finite conductivity

    Directory of Open Access Journals (Sweden)

    Shivakumara I S,

    2011-05-01

    Full Text Available The linear stability analysis of Marangoni convection in a fluid layer with a boundary slab of finite conductivity is considered. The effects of various non uniform temperature gradients are investigated. The lower boundary is a considered to be a thin slab of finite conductivity instead of a regular rigid surface. At the contact surface between the thin slab and the fluid layer the thermalboundary conditions are used and the upper surface is considered to be free and insulating to temperature perturbation and also surface tension effects are allowed. The resulting eigen value problem is solved exactly. The critical values of the Marangoni numbers for the onset of Marangoni convection are calculated for different temperature profile and the latter is found to be critically dependent on the depth ratio and conductivity ratio. The effects of the thermal conductivity and the thickness of the solid plate on the onset of convective instability with different temperature profile arestudied in detail.

  8. Turbulent boundary layer measurements over high-porosity surfaces

    Science.gov (United States)

    Efstathiou, Christoph; Luhar, Mitul

    2016-11-01

    Porous surfaces are ubiquitous across a variety of turbulent boundary layer flows of scientific and engineering interest. While turbulent flows over smooth and rough walls have been studied extensively, experimental measurements over porous walls have thus far focused on packed beds, which are limited in porosity (Φ = 0 . 3 - 0 . 5) by their geometry. The current project seeks to address this limitation. A two-component laser doppler velocimeter (LDV) is used to generate velocity measurements in turbulent boundary layer flows over commercially available reticulated foams and 3D-printed porous media at Reynolds number Reθ 3000 - 4000 . Smooth wall profiles for mean and turbulent quantities are compared to data over substrates with porosity Φ > 0 . 8 and average pore sizes in the range 0.4-2.5mm (corresponding to 8 - 50 viscous units). Previous analytical and simulation efforts indicate that the effects of porous substrates on boundary layer flows depend on a modified Reynolds number defined using the length scale √{ κ}, where κ is substrate permeability. A custom permeameter is currently being developed to estimate κ for the substrates tested in the boundary layer experiments.

  9. Universal equations of unsteady two-dimensional MHD boundary layer whose temperature varies with time

    Directory of Open Access Journals (Sweden)

    Boričić Zoran

    2009-01-01

    Full Text Available This paper concerns with unsteady two-dimensional temperature laminar magnetohydrodynamic (MHD boundary layer of incompressible fluid. It is assumed that induction of outer magnetic field is function of longitudinal coordinate with force lines perpendicular to the body surface on which boundary layer forms. Outer electric filed is neglected and magnetic Reynolds number is significantly lower then one i.e. considered problem is in inductionless approximation. Characteristic properties of fluid are constant because velocity of flow is much lower than speed of light and temperature difference is small enough (under 50ºC . Introduced assumptions simplify considered problem in sake of mathematical solving, but adopted physical model is interesting from practical point of view, because its relation with large number of technically significant MHD flows. Obtained partial differential equations can be solved with modern numerical methods for every particular problem. Conclusions based on these solutions are related only with specific temperature MHD boundary layer problem. In this paper, quite different approach is used. First new variables are introduced and then sets of similarity parameters which transform equations on the form which don't contain inside and in corresponding boundary conditions characteristics of particular problems and in that sense equations are considered as universal. Obtained universal equations in appropriate approximation can be solved numerically once for all. So-called universal solutions of equations can be used to carry out general conclusions about temperature MHD boundary layer and for calculation of arbitrary particular problems. To calculate any particular problem it is necessary also to solve corresponding momentum integral equation.

  10. Surface temperature measurements of diamond

    CSIR Research Space (South Africa)

    Masina, BN

    2006-07-01

    Full Text Available ) and the waist position (z0) 3. TEMPERATURE MEASUREMENTS There are many methods to measure the temperature of a body. Here we used a thermocou- ple and a pyrometer, while future plans involve emission spectroscopy. A thermocouple is a temperature... sensor that consists of two wires con- nected together made from different metals, which produces an electrical voltage that is dependant on tem- perature. A Newport electronic thermocou- ple was used to meas- ured temperature. It can measure...

  11. Evolution of vortex-surface fields in transitional boundary layers

    Science.gov (United States)

    Yang, Yue; Zhao, Yaomin; Xiong, Shiying

    2016-11-01

    We apply the vortex-surface field (VSF), a Lagrangian-based structure-identification method, to the DNS database of transitional boundary layers. The VSFs are constructed from the vorticity fields within a sliding window at different times and locations using a recently developed boundary-constraint method. The isosurfaces of VSF, representing vortex surfaces consisting of vortex lines with different wall distances in the laminar stage, show different evolutionary geometries in transition. We observe that the vortex surfaces with significant deformation evolve from wall-parallel planar sheets through hairpin-like structures and packets into a turbulent spot with regeneration of small-scale hairpins. From quantitative analysis, we show that a small number of representative or influential vortex surfaces can contribute significantly to the increase of the drag coefficient in transition, which implies a reduced-order model based on VSF. This work has been supported in part by the National Natural Science Foundation of China (Grant Nos. 11472015, 11522215 and 11521091), and the Thousand Young Talents Program of China.

  12. Numerical Study of Thermal Boundary Layer on a Continuous Moving Surface in Power Law Fluids

    Institute of Scientific and Technical Information of China (English)

    Hao ZHANG; Xinxin ZHANG; Liancun ZHENG

    2007-01-01

    This paper investigates flow and heat transfer of power law fluids on a continuous moving surface. The temperature distribution is obtained numerically by considering the effect of the power law viscosity on thermal diffusivity and the characteristics of the flow and heat transfer are analyzed. The results show that the distribution of the thermal boundary layer depends not only on the velocity ratio parameter of the plate, but also on the power law index and Prandtl number of fluids.

  13. An efficient analytical decomposition and numerical procedure for boundary layer flow on a continuous stretching surface

    Institute of Scientific and Technical Information of China (English)

    Xuehui Chen; Liancun Zheng; Xinxin Zhang

    2006-01-01

    An efficient Adomian analytical decomposition technique for studying the momentum and heat boundary layer equations with exponentially stretching surface conditions was presented and an approximate analytical solution was obtained, which can be represented in terms of a rapid convergent power series with elegantly computable terms. The reliability and efficiency of the approximate solution were verified using numerical solutions in the literature. The approximate solution can be successfully applied to provide the values of skin friction and the temperature gradient coefficient.

  14. LIMIT BEHAVIOUR OF SOLUTIONS TO EQUIVALUED SURFACE BOUNDARY VALUE PROBLEM FOR PARABOLIC EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    LI Fengquan

    2002-01-01

    In this paper, we discuss the limit behaviour of solutions to equivalued surface boundary value problem for parabolic equations when the equivalued surface boundary shrinks to a point and the space dimension of the domain is two or more.

  15. MHD Natural Convection with Convective Surface Boundary Condition over a Flat Plate

    Directory of Open Access Journals (Sweden)

    Mohammad M. Rashidi

    2014-01-01

    Full Text Available We apply the one parameter continuous group method to investigate similarity solutions of magnetohydrodynamic (MHD heat and mass transfer flow of a steady viscous incompressible fluid over a flat plate. By using the one parameter group method, similarity transformations and corresponding similarity representations are presented. A convective boundary condition is applied instead of the usual boundary conditions of constant surface temperature or constant heat flux. In addition it is assumed that viscosity, thermal conductivity, and concentration diffusivity vary linearly. Our study indicates that a similarity solution is possible if the convective heat transfer related to the hot fluid on the lower surface of the plate is directly proportional to (x--1/2 where x- is the distance from the leading edge of the solid surface. Numerical solutions of the ordinary differential equations are obtained by the Keller Box method for different values of the controlling parameters associated with the problem.

  16. Modelling global fresh surface water temperature

    NARCIS (Netherlands)

    Beek, L.P.H. van; Eikelboom, T.; Vliet, M.T.H. van; Bierkens, M.F.P.

    2011-01-01

    Temperature directly determines a range of water physical properties including vapour pressure, surface tension, density and viscosity, and the solubility of oxygen and other gases. Indirectly water temperature acts as a strong control on fresh water biogeochemistry, influencing sediment

  17. Modelling global fresh surface water temperature

    NARCIS (Netherlands)

    Beek, L.P.H. van; Eikelboom, T.; Vliet, M.T.H. van; Bierkens, M.F.P.

    2011-01-01

    Temperature directly determines a range of water physical properties including vapour pressure, surface tension, density and viscosity, and the solubility of oxygen and other gases. Indirectly water temperature acts as a strong control on fresh water biogeochemistry, influencing sediment concentrati

  18. Satellite Sensed Skin Sea Surface Temperature

    Science.gov (United States)

    Donlon, Craig

    1997-01-01

    Quantitative predictions of spatial and temporal changes the global climate rely heavily on the use of computer models. Unfortunately, such models cannot provide the basis for climate prediction because key physical processes are inadequately treated. Consequently, fine tuning procedures are often used to optimize the fit between model output and observational data and the validation of climate models using observations is essential if model based predictions of climate change are to be treated with any degree of confidence. Satellite Sea Surface Temperature (SST) observations provide high spatial and temporal resolution data which is extremely well suited to the initialization, definition of boundary conditions and, validation of climate models. In the case of coupled ocean-atmosphere models, the SST (or more correctly the 'Skin' SST (SSST)) is a fundamental diagnostic variable to consider in the validation process. Daily global SST maps derived from satellite sensors also provide adequate data for the detection of global patterns of change which, unlike any other SST data set, repeatedly extend into the southern hemisphere extra-tropical regions. Such data are essential to the success of the spatial 'fingerprint' technique, which seeks to establish a north-south asymmetry where warming is suppressed in the high latitude Southern Ocean. Some estimates suggest that there is a greater than 80% chance of directly detecting significant change (97.5 % confidence level) after 10-12 years of consistent global observations of mean sea surface temperature. However, these latter statements should be qualified with the assumption that a negligible drift in the observing system exists and that biases between individual instruments required to derive a long term data set are small. Given that current estimates for the magnitude of global warming of 0.015 K yr(sup -1) - 0.025 K yr(sup -1), satellite SST data sets need to be both accurate and stable if such a warming trend is to

  19. Flow, slippage and a hydrodynamic boundary condition of polymers at surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, M; Pastorino, C; Servantie, J [Institut fuer Theoretische Physik, Georg-August-Universitaet, D-37077 Goettingen (Germany)], E-mail: mmueller@theorie.physik.uni-goettingen.de

    2008-12-10

    Tailoring surface interactions or grafting of polymers onto surfaces is a versatile tool for controlling wettability, lubrication, adhesion and interactions between surfaces. Using molecular dynamics of a coarse-grained, bead-spring model and dynamic single-chain-in-mean-field simulations, we investigate how structural changes near the surface affect the flow of a polymer melt over the surface and how these changes can be parameterized by a hydrodynamic boundary condition. We study the temperature dependence of the near-surface flow of a polymer melt at a corrugated, attractive surface. At weakly attractive surfaces, lubrication layers form, the slip length is large and increases upon cooling. Close to the glass transition temperature, very large slip lengths are observed. At a more attractive surface, a 'sticky surface layer' is build up, giving rise to a small slip length. Upon cooling, the slip length decreases at high temperatures, passes through a minimum and increases upon approaching the glass transition temperature. At strongly attractive surfaces, the Navier slip condition fails to describe Couette and Poiseuille flows simultaneously. A similar failure of the Navier slip condition is observed for the flow of a polymer melt over a brush comprised of identical molecules. The wetting and flow properties of this surface are rather complex. Most notably, the cyclic motion of the grafted molecules gives rise to a reversal of the flow direction at the grafting surface. The failure of the Navier slip condition in both cases can be rationalized within a schematic, two-layer model, which demonstrates that the Navier slip condition fails to simultaneously describe Poiseuille and Couette flow if the fluid at the surface exhibits a higher viscosity than the bulk.

  20. The Inner Boundary of the Habitable Zone: Loss Processes of Liquid Water from Terrestrial Planet Surfaces

    Science.gov (United States)

    Stracke, B.; Godolt, M.; Grenfell, J. L.; von Paris, P.; Patzer, B.; Rauer, H.

    2012-04-01

    The question of habitability is very important in the context of terrestrial extrasolar planets. Generally, the Habitable Zone (HZ) is defined as the orbital region around a star, in which life-supporting (habitable) planets can exist. Taking into account that liquid water is a commonly accepted, fundamental requirement for the development of life - as we know it - the habitable region around a star is mainly determined by the stellar insolation of radiation, which is sufficient to maintain liquid water at the planetary surface. This study focuses on different processes that can lead to the complete loss of a liquid water reservoir from the surface of a terrestrial planet to determine the inner boundary of the HZ. The investigated criteria are, for example, reaching the temperature of the critical point of water at the planetary surface, the runaway greenhouse effect and the diffusion-limited escape of water from the atmosphere, which could lead to the loss of the complete water reservoir within the lifetime of a planet. We investigate these criteria, which determine the inner boundary of the HZ, with a one-dimensional radiative-convective model of a planetary atmosphere, which extends from the surface to the mid-mesosphere. Our modelling approach involves the step-by-step increase of the incoming stellar flux and the subsequent iterative calculation of resulting changes in the temperature profiles, the atmospheric water vapour content and the radiative properties. Therefore, this climate model had to be adapted to account for high temperatures and water mixing ratios. For example, the infrared radiative transfer scheme was improved to be suitable for such high temperature and pressure conditions. Modelling results are presented determining the inner boundary of the HZ affected by these processes, which can result in no liquid water on the planetary surface. In this context, especially the role of the runaway greenhouse effect is discussed in detail.

  1. Total temperature probes for high-temperature hypersonic boundary-layer measurements

    Science.gov (United States)

    Albertson, Cindy W.; Bauserman, Willard A., Jr.

    1993-01-01

    The design and test results of two types of total temperature probes that were used for hypersonic boundary-layer measurements are presented. The intent of each design was to minimize the total error and to maintain minimal size for measurements in boundary layers 1.0 in. thick and less. A single platinum-20-percent-rhodium shield was used in both designs to minimize radiation heat transfer losses during exposure to the high-temperature test stream. The shield of the smaller design was flattened at the flow entrance to an interior height of 0.02 in., compared with 0.03 in. for the larger design. The resulting vent-to-inlet area ratios were 60 and 50 percent. A stainless steel structural support sleeve that was used in the larger design was excluded from the smaller design, which resulted in an outer diameter of 0.059 in., to allow closer placement of the probes to each other and to the wall. These small design changes to improve resolution did not affect probe performance. Tests were conducted at boundary-layer-edge Mach numbers of 5.0 and 6.2. The nominal free-stream total temperatures were 2600 degrees and 3200 degrees R. The probes demonstrated extremely good reliability. The best performance in terms of recovery factor occurred when the wire-based Nusselt number was at least 0.04. Recommendations for future probe designs are included.

  2. Role of surface temperature in fluorocarbon plasma-surface interactions

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Caleb T.; Overzet, Lawrence J.; Goeckner, Matthew J. [Department of Electrical Engineering, University of Texas at Dallas, PO Box 830688, Richardson, TX 75083 (United States)

    2012-07-15

    This article examines plasma-surface reaction channels and the effect of surface temperature on the magnitude of those channels. Neutral species CF{sub 4}, C{sub 2}F{sub 6}, and C{sub 3}F{sub 8} are produced on surfaces. The magnitude of the production channel increases with surface temperature for all species, but favors higher mass species as the temperature is elevated. Additionally, the production rate of CF{sub 2} increases by a factor of 5 as the surface temperature is raised from 25 Degree-Sign C to 200 Degree-Sign C. Fluorine density, on the other hand, does not change as a function of either surface temperature or position outside of the plasma glow. This indicates that fluorine addition in the gas-phase is not a dominant reaction. Heating reactors can result in higher densities of depositing radical species, resulting in increased deposition rates on cooled substrates. Finally, the sticking probability of the depositing free radical species does not change as a function of surface temperature. Instead, the surface temperature acts together with an etchant species (possibly fluorine) to elevate desorption rates on that surface at temperatures lower than those required for unassisted thermal desorption.

  3. Boundary conditions for free surface inlet and outlet problems

    KAUST Repository

    Taroni, M.

    2012-08-10

    We investigate and compare the boundary conditions that are to be applied to free-surface problems involving inlet and outlets of Newtonian fluid, typically found in coating processes. The flux of fluid is a priori known at an inlet, but unknown at an outlet, where it is governed by the local behaviour near the film-forming meniscus. In the limit of vanishing capillary number Ca it is well known that the flux scales with Ca 2/3, but this classical result is non-uniform as the contact angle approaches π. By examining this limit we find a solution that is uniformly valid for all contact angles. Furthermore, by considering the far-field behaviour of the free surface we show that there exists a critical capillary number above which the problem at an inlet becomes over-determined. The implications of this result for the modelling of coating flows are discussed. © 2012 Cambridge University Press.

  4. Near-Surface Boundary Layer Turbulence Along a Horizontally-Moving, Surface-Piercing Vertical Wall

    CERN Document Server

    Washuta, Nathan; Duncan, James H

    2016-01-01

    The complex interaction between turbulence and the free surface in boundary layer shear flow created by a vertical surface-piercing wall is considered. A laboratory-scale device was built that utilizes a surface-piercing stainless steel belt that travels in a loop around two vertical rollers, with one length of the belt between the rollers acting as a horizontally-moving flat wall. The belt is accelerated suddenly from rest until reaching constant speed in order to create a temporally-evolving boundary layer analogous to the spatially-evolving boundary layer that would exist along a surface-piercing towed flat plate. Surface profiles are measured with a cinematic laser-induced fluorescence system and sub-surface velocity fields are recorded using a high-speed planar particle image velocimetry system. It is found that the belt initially travels through the water without creating any significant waves, before the free surface bursts with activity close to the belt surface. These free surface ripples travel away...

  5. Heat transfer in a couple stress fluid over a continuous moving surface with internal hat generation and convective boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hayat, Tasawar [Quaid-i-Azam Univ., Islamabad (Pakistan). Dept. of Mathematics; King Saud Univ., Riyadh (Saudi Arabia). Dept. of Physics; Iqbal, Zahid [Quaid-i-Azam Univ., Islamabad (Pakistan). Dept. of Mathematics; Qasim, Muhammad [COMSATS Institute of Information Technology (CIIT), Islamabad (Pakistan). Dept. of Mathematics; Aldossary, Omar M. [King Saud Univ., Riyadh (Saudi Arabia). Dept. of Physics

    2012-05-15

    This investigation reports the boundary layer flow and heat transfer characteristics in a couple stress fluid flow over a continuos moving surface with a parallel free stream. The effects of heat generation in the presence of convective boundary conditions are also investigated. Series solutions for the velocity and temperature distributions are obtained by the homotopy analysis method (HAM). Convergence of obtained series solutions are analyzed. The results are obtained and discussed through graphs for physical parameters of interest. (orig.)

  6. LOTOS: A Proposed Lower Tropospheric Observing System from the Land Surface through the Atmospheric Boundary Layer

    Science.gov (United States)

    Cohn, S. A.; Lee, W. C.; Carbone, R. E.; Oncley, S.; Brown, W. O. J.; Spuler, S.; Horst, T. W.

    2015-12-01

    Advances in sensor capabilities, but also in electronics, optics, RF communication, and off-the-grid power are enabling new measurement paradigms. NCAR's Earth Observing Laboratory (EOL) is considering new sensors, new deployment modes, and integrated observing strategies to address challenges in understanding within the atmospheric boundary layer and the underlying coupling to the land surface. Our vision is of a network of deployable observing sites, each with a suite of complementary instruments that measure surface-atmosphere exchange, and the state and evolution of the boundary layer. EOL has made good progress on distributed surface energy balance and flux stations, and on boundary layer remote sensing of wind and water vapor, all suitable for deployments of combined instruments and as network of such sites. We will present the status of the CentNet surface network development, the 449-MHz modular wind profiler, and a water vapor and temperature profiling differential absorption lidar (DIAL) under development. We will further present a concept for a test bed to better understand the value of these and other possible instruments in forming an instrument suite flexible for multiple research purposes.

  7. Gravity increased by lunar surface temperature

    Science.gov (United States)

    Keene, James

    2013-04-01

    Quantitatively large effects of lunar surface temperature on apparent gravitational force measured by lunar laser ranging (LLR) and lunar perigee may challenge widely accepted theories of gravity. LLR data grouped by days from full moon shows the moon is about 5 percent closer to earth at full moon compared to 8 days before or after full moon. In a second, related result, moon perigees were least distant in days closer to full moon. Moon phase was used as proxy independent variable for lunar surface temperature. The results support the prediction by binary mechanics that gravitational force increases with object surface temperature.

  8. Turbulent boundary layer over a divergent convergent superhydrophobic surface

    Science.gov (United States)

    Jalalabadi, Razieh; Hwang, Jinyul; Nadeem, Muhammad; Yoon, Min; Sung, Hyung Jin

    2017-08-01

    A direct numerical simulation of a spatially developing turbulent boundary layer over a divergent and convergent superhydrophobic surface (SHS) was performed over the range 800 < Reθ < 1200. The surface patterns were aligned along the streamwise direction. The SHS was modeled as a pattern of free-slip and no-slip surfaces. The gas fraction of the divergent and convergent SHS was the same as that for the straight SHS for a given slip area. The divergent and convergent SHS gave 21% more drag reduction than the straight SHS. Although the maximum value of the streamwise slip velocity was larger over the divergent and convergent SHS, the average slip velocity (Uslip/U∞) was larger over the straight SHS. The greater drag reduction was attributed to the manipulation of the secondary flow in the y-z plane and the changes in the turbulence structure. The streamwise vortices generated by the secondary flow over the divergent and convergent SHS were diminished which reduced drag relative to the flow over the straight SHS. The ejection and sweep motions were weak, and the vortical structure was attenuated near the wall over the divergent and convergent SHS. The skin friction contributions were explored using the velocity-vorticity correlation. The vortex stretching contribution dominated the skin friction budget. The reduced skin friction over the divergent and convergent SHS resulted mainly from reduced vortex stretching.

  9. Electron scattering at surfaces and grain boundaries in thin Au films

    Energy Technology Data Exchange (ETDEWEB)

    Henriquez, Ricardo [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Casilla 110-V, Valparaíso (Chile); Flores, Marcos; Moraga, Luis [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Casilla 487-3, Santiago 8370449 (Chile); Kremer, German [Bachillerato, Universidad de Chile, Las Palmeras 3425, Santiago 7800024 (Chile); González-Fuentes, Claudio [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Casilla 110-V, Valparaíso (Chile); Munoz, Raul C., E-mail: ramunoz@ing.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Casilla 487-3, Santiago 8370449 (Chile)

    2013-05-15

    The electron scattering at surfaces and grain boundaries is investigated using polycrystalline Au films deposited onto mica substrates. We vary the three length scales associated with: (i) electron scattering in the bulk, that at temperature T is characterized by the electronic mean free path in the bulk ℓ{sub 0}(T); (ii) electron-surface scattering, that is characterized by the film thickness t; (iii) electron-grain boundary scattering, that is characterized by the mean grain diameter D. We varied independently the film thickness from approximately 50 nm to about 100 nm, and the typical grain size making up the samples from 12 nm to 160 nm. We also varied the scale of length associated with electron scattering in the bulk by measuring the resistivity of each specimen at temperatures T, 4 K < T < 300 K. Cooling the samples to 4 K increases ℓ{sub 0}(T) by approximately 2 orders of magnitude. Detailed measurements of the grain size distribution as well as surface roughness of each sample were performed with a Scanning Tunnelling Microscope (STM). We compare, for the first time, theoretical predictions with resistivity data employing the two theories available that incorporate the effect of both electron-surface as well as electron-grain boundary scattering acting simultaneously: the theory of A.F. Mayadas and M. Shatzkes, Phys. Rev. 1 1382 (1970) (MS), and that of G. Palasantzas, Phys. Rev. B 58 9685 (1998). We eliminate adjustable parameters from the resistivity data analysis, by using as input the grain size distribution as well as the surface roughness measured with the STM on each sample. The outcome is that both theories provide a fair representation of both the temperature as well as the thickness dependence of the resistivity data, but yet there are marked differences between the resistivity predicted by these theories. In the case of the MS theory, when the average grain diameter D is significantly smaller than ℓ{sub 0}(300) = 37 nm, the electron mean

  10. Sea ice edge position impact on the atmospheric boundary layer temperature structure

    Science.gov (United States)

    Khavina, Elena; Repina, Irina

    2016-04-01

    Processes happening in the Arctic region nowadays strongly influence global climate system; the polar amplification effect can be considered one of the main indicators of ongoing changes. Dramatic increase in amount of ice-free areas in the Arctic Ocean, which took place in 2000s, is one of the most significant examples of climate system dynamic in polar region. High amplitude of changes in Arctic climate, both observed and predicted, and existing inaccuracies of climate and weather forecasting models, enforce the development of a more accurate one. It is essential to understand the physics of the interaction between atmosphere and ocean in the Northern Polar area (particularly in boundary layer of the atmosphere) to improve the models. Ice conditions have a great influence on the atmospheric boundary layer in the Arctic. Sea ice inhibits the heat exchange between atmosphere and ocean water during the polar winter, while the heat exchange above the ice-free areas increases rapidly. Due to those significant temperature fluctuations, turbulence of heat fluxes grows greatly. The most intensive interaction takes place at marginal ice zones, especially in case of the cold outbreak - intrusion of cooled air mass from the ice to free water area. Still, thermal structure and dynamic of the atmosphere boundary layer are not researched and described thoroughly enough. Single radio sounding observations from the planes being done, bur they do not provide high-resolution data which is necessary for study. This research is based on continuous atmosphere boundary layer temperature and sea ice observation collected in the Arctic Ocean during the two NABOS expeditions in August and September in 2013 and 2015, as well as on ice conditions satellite data (NASA TEAM 2 and VASIA 2 data processing). Atmosphere temperature data has been obtained with Meteorological Temperature Profiler MTP-5 (ATTEX, Russia). It is a passive radiometer, which provides continuous data of atmospheric

  11. Planetary boundary layer depth in Global climate models induced biases in surface climatology

    CERN Document Server

    Davy, Richard

    2014-01-01

    The Earth has warmed in the last century with the most rapid warming occurring near the surface in the arctic. This enhanced surface warming in the Arctic is partly because the extra heat is trapped in a thin layer of air near the surface due to the persistent stable-stratification found in this region. The warming of the surface air due to the extra heat depends upon the amount of turbulent mixing in the atmosphere, which is described by the depth of the atmospheric boundary layer (ABL). In this way the depth of the ABL determines the effective response of the surface air temperature to perturbations in the climate forcing. The ABL depth can vary from tens of meters to a few kilometers which presents a challenge for global climate models which cannot resolve the shallower layers. Here we show that the uncertainties in the depth of the ABL can explain up to 60 percent of the difference between the simulated and observed surface air temperature trends and 50 percent of the difference in temperature variability...

  12. Sea Surface Temperature Average_SST_Master

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sea surface temperature collected via satellite imagery from http://www.esrl.noaa.gov/psd/data/gridded/data.noaa.ersst.html and averaged for each region using ArcGIS...

  13. OW NOAA GOES Sea-Surface Temperature

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The dataset contains satellite-derived sea-surface temperature measurements collected by means of the Geostationary Orbiting Environmental Satellite. The data is...

  14. evaluation of land surface temperature parameterization ...

    African Journals Online (AJOL)

    user

    1 DEPARTMENT OF PHYSICS, ADEYEMI COLLEGE OF EDUCATION, ONDO, ... Surface temperature (Ts) is vital to the study of land-atmosphere interactions and climate variabilities. .... value = 0.167 m3m-3), and very low for dry days (mean.

  15. Monthly Near-Surface Air Temperature Averages

    Data.gov (United States)

    National Aeronautics and Space Administration — Global surface temperatures in 2010 tied 2005 as the warmest on record. The International Satellite Cloud Climatology Project (ISCCP) was established in 1982 as part...

  16. Sea Surface Temperature (14 KM North America)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Product shows local sea surface temperatures (degrees C). It is a composite gridded-image derived from 8-km resolution SST Observations. It is generated every 48...

  17. Analysed foundation sea surface temperature, global

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The through-cloud capabilities of microwave radiometers provide a valuable picture of global sea surface temperature (SST). To utilize this, scientists at Remote...

  18. Importance of initial buoyancy field on evolution of mantle thermal structure: Implications of surface boundary conditions

    Directory of Open Access Journals (Sweden)

    Petar Glišović

    2015-01-01

    Full Text Available Although there has been significant progress in the seismic imaging of mantle heterogeneity, the outstanding issue that remains to be resolved is the unknown distribution of mantle temperature anomalies in the distant geological past that give rise to the present-day anomalies inferred by global tomography models. To address this question, we present 3-D convection models in compressible and self-gravitating mantle initialised by different hypothetical temperature patterns. A notable feature of our forward convection modelling is the use of self-consistent coupling of the motion of surface tectonic plates to the underlying mantle flow, without imposing prescribed surface velocities (i.e., plate-like boundary condition. As an approximation for the surface mechanical conditions before plate tectonics began to operate we employ the no-slip (rigid boundary condition. A rigid boundary condition demonstrates that the initial thermally-dominated structure is preserved, and its geographical location is fixed during the evolution of mantle flow. Considering the impact of different assumed surface boundary conditions (rigid and plate-like on the evolution of thermal heterogeneity in the mantle we suggest that the intrinsic buoyancy of seven superplumes is most-likely resolved in the tomographic images of present-day mantle thermal structure. Our convection simulations with a plate-like boundary condition reveal that the evolution of an initial cold anomaly beneath the Java-Indonesian trench system yields a long-term, stable pattern of thermal heterogeneity in the lowermost mantle that resembles the present-day Large Low Shear Velocity Provinces (LLSVPs, especially below the Pacific. The evolution of subduction zones may be, however, influenced by the mantle-wide flow driven by deeply-rooted and long-lived superplumes since Archean times. These convection models also detect the intrinsic buoyancy of the Perm Anomaly that has been identified as a unique

  19. Urban aerosol effects on surface insolation and surface temperature

    Science.gov (United States)

    Jin, M.; Burian, S. J.; Remer, L. A.; Shepherd, M. J.

    2007-12-01

    Urban aerosol particulates may play a fundamental role in urban microclimates and city-generated mesoscale circulations via its effects on energy balance of the surface. Key questions that need to be addressed include: (1) How do these particles affect the amount of solar energy reaching the surface and resulting surface temperature? (2) Is the effect the same in all cities? and (3) How does it vary from city to city? Using NASA AERONET in-situ observations, a radiative transfer model, and a regional climate mode (MM5), we assess aerosol effects on surface insolation and surf ace temperature for dense urban-polluted regions. Two big cities, one in a developing country (Beijing, P.R. China) and another in developed country (New York City, USA), are selected for inter-comparison. The study reveals that aerosol effects on surface temperature depends largely on aerosols' optical and chemical properties as well as atmosphere and land surface conditions, such as humidity and land cover. Therefore, the actual magnitudes of aerosol effects differ from city to city. Aerosol measurements from AERONET show both average and extreme cases for aerosol impacts on surface insolation. In general, aerosols reduce surface insolation by 30Wm-2. Nevertheless, in extreme cases, such reduction can exceed 100 Wm-2. Consequently, this reduces surface skin temperature 2-10C in an urban environment.

  20. Modeling of global surface air temperature

    Science.gov (United States)

    Gusakova, M. A.; Karlin, L. N.

    2012-04-01

    A model to assess a number of factors, such as total solar irradiance, albedo, greenhouse gases and water vapor, affecting climate change has been developed on the basis of Earth's radiation balance principle. To develop the model solar energy transformation in the atmosphere was investigated. It's a common knowledge, that part of the incoming radiation is reflected into space from the atmosphere, land and water surfaces, and another part is absorbed by the Earth's surface. Some part of outdoing terrestrial radiation is retained in the atmosphere by greenhouse gases (carbon dioxide, methane, nitrous oxide) and water vapor. Making use of the regression analysis a correlation between concentration of greenhouse gases, water vapor and global surface air temperature was obtained which, it is turn, made it possible to develop the proposed model. The model showed that even smallest fluctuations of total solar irradiance intensify both positive and negative feedback which give rise to considerable changes in global surface air temperature. The model was used both to reconstruct the global surface air temperature for the 1981-2005 period and to predict global surface air temperature until 2030. The reconstructions of global surface air temperature for 1981-2005 showed the models validity. The model makes it possible to assess contribution of the factors listed above in climate change.

  1. Implicit temperature-correction-based immersed-boundary thermal lattice Boltzmann method for the simulation of natural convection.

    Science.gov (United States)

    Seta, Takeshi

    2013-06-01

    In the present paper, we apply the implicit-correction method to the immersed-boundary thermal lattice Boltzmann method (IB-TLBM) for the natural convection between two concentric horizontal cylinders and in a square enclosure containing a circular cylinder. The Chapman-Enskog multiscale expansion proves the existence of an extra term in the temperature equation from the source term of the kinetic equation. In order to eliminate the extra term, we redefine the temperature and the source term in the lattice Boltzmann equation. When the relaxation time is less than unity, the new definition of the temperature and source term enhances the accuracy of the thermal lattice Boltzmann method. The implicit-correction method is required in order to calculate the thermal interaction between a fluid and a rigid solid using the redefined temperature. Simulation of the heat conduction between two concentric cylinders indicates that the error at each boundary point of the proposed IB-TLBM is reduced by the increment of the number of Lagrangian points constituting the boundaries. We derive the theoretical relation between a temperature slip at the boundary and the relaxation time and demonstrate that the IB-TLBM requires a small relaxation time in order to avoid temperature distortion around the immersed boundary. The streamline, isotherms, and average Nusselt number calculated by the proposed method agree well with those of previous numerical studies involving natural convection. The proposed IB-TLBM improves the accuracy of the boundary conditions for the temperature and velocity using an adequate discrete area for each of the Lagrangian nodes and reduces the penetration of the streamline on the surface of the body.

  2. Effective slip boundary conditions for arbitrary periodic surfaces: The surface mobility tensor

    CERN Document Server

    Kamrin, Ken; Stone, Howard A

    2009-01-01

    In a variety of applications, most notably microfluidic design, slip-based boundary conditions have been sought to characterize fluid flow over patterned surfaces. We focus on laminar shear flows over surfaces with periodic height fluctuations and/or fluctuating Navier scalar slip properties. We derive a general formula for the "effective slip", which describes equivalent fluid motion at the mean surface as depicted by the linear velocity profile that arises far from it. We show that the slip and the applied stress are related linearly through a tensorial mobility matrix, and the method of domain perturbation is then used to derive an approximate formula for the mobility law directly in terms of surface properties. The specific accuracy of the approximation is detailed, and the mobility relation is then utilized to address several questions, such as the determination of optimal surface shapes and the effect of random surface fluctuations on fluid slip.

  3. Earth's core-mantle boundary - Results of experiments at high pressures and temperatures

    Science.gov (United States)

    Knittle, Elise; Jeanloz, Raymond

    1991-01-01

    Laboratory experiments document that liquid iron reacts chemically with silicates at high pressures (above 2.4 x 10 to the 10th Pa) and temperatures. In particular, (Mg,Fe)SiO3 perovskite, the most abundant mineral of earth's lower mantle, is expected to react with liquid iron to produce metallic alloys (FeO and FeSi) and nonmetallic silicates (SiO2 stishovite and MgSiO3 perovskite) at the pressures of the core-mantle boundary, 14 x 10 to the 10th Pa. The experimental observations, in conjunction with seismological data, suggest that the lowermost 200 to 300 km of earth's mantle, the D-double-prime layer, may be an extremely heterogeneous region as a result of chemical reactions between the silicate mantle and the liquid iron alloy of earth's core. The combined thermal-chemical-electrical boundary layer resulting from such reactions offers a plausible explanation for the complex behavior of seismic waves near the core-mantle boundary and could influence earth's magnetic field observed at the surface.

  4. Boundary Conditions at the Walls with Thermionic Electron Emission in Two Temperature Modeling of "Thermal" Plasmas

    CERN Document Server

    Pekker, Leonid

    2015-01-01

    In this paper we propose new boundary conditions at the hot walls with thermionic electron emission for two-temperature thermal arc models. In the derived boundary conditions the walls are assumed to be made from refractory metals and that the erosion of the wall is small and, therefore, is not taken into account in the model. In these boundary conditions the plasma sheath formed at the electrode is considered as the interface between the plasma and the wall. The derived boundary conditions allow the calculation of the heat flux to the walls from the plasma and consequently the thermionic electron current that makes the two temperature thermal model self consistent.

  5. Effects of temperature boundary conditions on equiaxed dendritic growth in phase-field simulations of binary alloy

    Institute of Scientific and Technical Information of China (English)

    于艳梅; 杨根仓; 赵达文; 吕衣礼

    2002-01-01

    By the phase-field approach, the dendritic growth in binary alloy melt was simulated respectively using two types of temperature boundary conditions, i.e., the constant temperature boundary by which the boundary temperature was fixed at the initial temperature, and Zero-Neumann temperature boundary. The influences of the temperature boundary conditions on numerical results are investigated. How to choose appropriate temperature boundary conditions is proposed. The results show that: 1) when the computation region is limited to a changeless size, the Zero-Neumann and constant temperature boundary conditions lead to the different dendritic growth behaviors, and the Zero-Neumann condition is preferable to the constant temperature condition; 2) when the computation region is enlarged continually with the computational time according to the increasing thermal diffusion scale, the two types of temperature boundary conditions achieve the consistent tip velocities and tip radii, and they both are appropriate choices.

  6. Impacts of surface heterogeneity on dry planetary boundary layers in an urban-rural setting

    Science.gov (United States)

    Zhu, Xiaoliang; Ni, Guangheng; Cong, Zhentao; Sun, Ting; Li, Dan

    2016-10-01

    Understanding the impacts of land use and land-cover change such as urbanization is essential in many disciplines. This study investigates the impacts of urban-rural contrasts in terms of momentum roughness length (z0) and aerodynamic surface temperature (TSK) on dry planetary boundary layers (PBLs) using large-eddy simulations (LES) with the Weather Research and Forecasting (WRF) model. In addition, the impacts of small-scale heterogeneities within urban areas are also examined. The original WRF-LES is modified in order to use prescribed TSK as surface boundary conditions. Numerical simulations are then conducted to examine turbulence characteristics and mesoscale circulations resulting from large-scale urban-rural contrasts as well as small-scale heterogeneities in urban areas. The results indicate that (1) the urban-rural contrasts in z0 and TSK have significant but different impacts on surface heat fluxes, mesoscale circulations, and the wind and potential temperature profiles. Compared to the case where the whole domain is homogeneous, increases in z0 and/or TSK in urban areas in the center of domain induce stronger sensible heat fluxes, stronger urban circulations, and weaker inversions at the top of the PBL. (2) When the patch size that characterizes the urban heterogeneity scale is comparable to the size of the whole urban area, the simulated results are strongly dependent on both the heterogeneity scale and the specified surface temperature values. As the patch size decreases, the simulated results become more similar to those over a homogeneous urban surface.

  7. Unsteady Hydromagnetic Flow past a Moving Vertical Plate with Convective Surface Boundary Condition

    Directory of Open Access Journals (Sweden)

    Gauri Shanker Seth

    2016-01-01

    Full Text Available Investigation of unsteady MHD natural convection flow through a fluid-saturated porous medium of a viscous, incompressible, electrically-conducting and optically-thin radiating fluid past an impulsively moving semi-infinite vertical plate with convective surface boundary condition is carried out. With the aim to replicate practical situations, the heat transfer and thermal expansion coefficients are chosen to be constant and a new set of non-dimensional quantities and parameters are introduced to represent the governing equations along with initial and boundary conditions in dimensionless form. Solution of the initial boundary-value problem (IBVP is obtained by an efficient implicit finite-difference scheme of the Crank-Nicolson type which is one of the most popular schemes to solve IBVPs. The numerical values of fluid velocity and fluid temperature are depicted graphically whereas those of the shear stress at the wall, wall temperature and the wall heat transfer are presented in tabular form for various values of the pertinent flow parameters. A comparison with previously published papers is made for validation of the numerical code and the results are found to be in good agreement.

  8. International Surface Temperature Initiative (ISTI) Global Land Surface Temperature Databank - Stage 2 Monthly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The global land surface temperature databank contains monthly timescale mean, max, and min temperature for approximately 40,000 stations globally. It was developed...

  9. International Surface Temperature Initiative (ISTI) Global Land Surface Temperature Databank - Stage 2 Daily

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The global land surface temperature databank contains monthly timescale mean, max, and min temperature for approximately 40,000 stations globally. It was developed...

  10. International Surface Temperature Initiative (ISTI) Global Land Surface Temperature Databank - Stage 3 Monthly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Global Land Surface Temperature Databank contains monthly timescale mean, maximum, and minimum temperature for approximately 40,000 stations globally. It was...

  11. International Surface Temperature Initiative (ISTI) Global Land Surface Temperature Databank - Stage 1 Daily

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The global land surface temperature databank contains monthly timescale mean, max, and min temperature for approximately 40,000 stations globally. It was developed...

  12. International Surface Temperature Initiative (ISTI) Global Land Surface Temperature Databank - Stage 1 Monthly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The global land surface temperature databank contains monthly timescale mean, max, and min temperature for approximately 40,000 stations globally. It was developed...

  13. Modification of Turbulent Boundary Layer Flows by Superhydrophobic Surfaces

    Science.gov (United States)

    Gose, James W.; Golovin, Kevin; Barros, Julio; Schultz, Michael P.; Tuteja, Anish; Perlin, Marc; Ceccio, Steven L.

    2016-11-01

    Measurements of near zero pressure gradient turbulent boundary layer (TBL) flow over several superhydrophobic surfaces (SHSs) are presented and compared to those for a hydraulically smooth baseline. The surfaces were developed at the University of Michigan as part of an ongoing research thrust to investigate the feasibility of SHSs for skin-friction drag reduction in turbulent flow. The SHSs were previously evaluated in fully-developed turbulent channel flow and have been shown to provide meaningful drag reduction. The TBL experiments were conducted at the USNA in a water tunnel with a test section 2.0 m (L) x 0.2 m (W) x 0.2 m (H). The free-stream speed was set to 1.26 m/s which corresponded to a friction Reynolds number of 1,500. The TBL was tripped at the test section inlet with a 0.8 mm diameter wire. The upper and side walls provided optical access, while the lower wall was either the smooth baseline or a spray coated SHS. The velocity measurements were obtained with a TSI FSA3500 two-component Laser-Doppler Velocimeter (LDV) and custom-designed beam displacer operated in coincidence mode. The LDV probe volume diameter was 45 μm (approx. one wall-unit). The measurements were recorded 1.5 m downstream of the trip. When the measured quantities were normalized using the inner variables, the results indicated a significant reduction in the near wall viscous and total stresses with little effect on the flow outside the inner layer.

  14. Molecular dynamics simulation of temperature profile in partially hydrogenated graphene and graphene with grain boundary.

    Science.gov (United States)

    Lotfi, Erfan; Neek-Amal, M; Elahi, M

    2015-11-01

    Temperature profile in graphene, graphene with grain boundary and vacancy defects and hydrogenated graphene with different percentage of H-atoms are determined using molecular dynamics simulation. We also obtained the temperature profile in a graphene nanoribbon containing two types of grain boundaries with different misorientation angles, θ=21.8° and θ=32.2°. We found that a temperature gap appears in the temperature profile of a graphene nanoribbon with a grain boundary at the middle. Moreover, we found that the temperature profile in the partially hydrogenated graphene varies with the percentage of hydrogens, i.e. the C:H ratio. Our results show that a grain boundary line in the graphene sheet can change the thermal transport through the system which might be useful for controlling thermal flow in nanostructured graphene.

  15. Calibration of surface temperature on rocky exoplanets

    Science.gov (United States)

    Kashyap Jagadeesh, Madhu

    2016-07-01

    Study of exoplanets and the search for life elsewhere has been a very fascinating area in recent years. Presently, lots of efforts have been channelled in this direction in the form of space exploration and the ultimate search for the habitable planet. One of the parametric methods to analyse the data available from the missions such as Kepler, CoRoT, etc, is the Earth Similarity Index (ESI), defined as a number between zero (no similarity) and one (identical to Earth), introduced to assess the Earth likeness of exoplanets. A multi-parameter ESI scale depends on the radius, density, escape velocity and surface temperature of exoplanets. Our objective is to establish how exactly the individual parameters, entering the interior ESI and surface ESI, are contributing to the global ESI, using the graphical analysis. Presently, the surface temperature estimates are following a correction factor of 30 K, based on the Earth's green-house effect. The main objective of this work in calculations of the global ESI using the HabCat data is to introduce a new method to better estimate the surface temperature of exoplanets, from theoretical formula with fixed albedo factor and emissivity (Earth values). From the graphical analysis of the known data for the Solar System objects, we established the calibration relation between surface and equilibrium temperatures for the Solar System objects. Using extrapolation we found that the power function is the closest description of the trend to attain surface temperature. From this we conclude that the correction term becomes very effective way to calculate the accurate value of the surface temperature, for further analysis with our graphical methodology.

  16. Relation between the Atmospheric Boundary Layer and Impact Factors under Severe Surface Thermal Conditions

    Directory of Open Access Journals (Sweden)

    Yinhuan Ao

    2017-01-01

    Full Text Available This paper reported a comprehensive analysis on the diurnal variation of the Atmospheric Boundary Layer (ABL in summer of Badain Jaran Desert and discussed deeply the effect of surface thermal to ABL, including the Difference in Surface-Air Temperature (DSAT, net radiation, and sensible heat, based on limited GPS radiosonde and surface observation data during two intense observation periods of experiments. The results showed that (1 affected by topography of the Tibetan Plateau, the climate provided favorable external conditions for the development of Convective Boundary Layer (CBL, (2 deep CBL showed a diurnal variation of three- to five-layer structure in clear days and five-layer ABL structure often occurred about sunset or sunrise, (3 the diurnal variation of DSAT influenced thickness of ABL through changes of turbulent heat flux, (4 integral value of sensible heat which rapidly converted by surface net radiation had a significant influence on the growth of CBL throughout daytime. The cumulative effect of thick RML dominated the role after CBL got through SBL in the development stage, especially in late summer, and (5 the development of CBL was promoted and accelerated by the variation of wind field and distribution of warm advection in high and low altitude.

  17. Thermodynamic equilibrium studies of nanocrystallite SrTiO3 grain boundaries by high temperature photoelectron spectroscopy

    Institute of Scientific and Technical Information of China (English)

    刘振祥; 谢侃

    2000-01-01

    Nanostructured strontium titanate (SrTiO3) thin films are studied by high temperature pho-toelectron spectroscopy and thermal gravimetric analysis. The results indicate that ion migration and redistribution as well as transformation between lattice oxygen and gas phase oxygen take place near the grain boundaries during thermodynamic equilibrium process, which lead to obvious variation of the surface composition with temperature. The lattice oxygen ions migrate from bulk to grain surface with temperature rising up; meanwhile Ti ions also migrate to grain surface and combine with oxygen ions forming Ti-O complex. An opposite process takes place during temperature falling down, but the latter process is much slower than the former one. A primary model is proposed to explain this phenomenon.

  18. Thermodynamic equilibrium studies of nanocrystallite SrTiO3 grain boundaries by high temperature photoelectron spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Nanostructured strontium titanate (SrTiO3) thin films are studied by high temperature photoelectron spectroscopy and thermal gravimetric analysis. The results indicate that ion migration and redistribution as well as transformation between lattice oxygen and gas phase oxygen take place near the grain boundaries during thermodynamic equilibrium process, which lead to obvious variation of the surface composition with temperature. The lattice oxygen ions migrate from bulk to grain surface with temperature rising up; meanwhile Ti ions also migrate to grain surface and combine with oxygen ions forming Ti-O complex. An opposite process takes place during temperature falling down, but the latter process is much slower than the former one. A primary model is proposed to explain this phenomenon.

  19. Integrative inversion of land surface component temperature

    Institute of Scientific and Technical Information of China (English)

    FAN Wenjie; XU Xiru

    2005-01-01

    In this paper, the row winter wheat was selected as the example to study the component temperature inversion method of land surface target in detail. The result showed that the structural pattern of row crop can affect the inversion precision of component temperature evidently. Choosing appropriate structural pattern of row crop can improve the inversion precision significantly. The iterative method combining inverse matrix was a stable method that was fit for inversing component temperature of land surface target. The result of simulation and field experiment showed that the integrative method could remarkably improve the inversion accuracy of the lighted soil surface temperature and the top layer canopy temperature, and enhance inversion stability of components temperature. Just two parameters were sufficient for accurate atmospheric correction of multi-angle and multi-spectral thermal infrared data: atmospheric transmittance and the atmospheric upwelling radiance. If the atmospheric parameters and component temperature can be inversed synchronously, the really and truly accurate atmospheric correction can be achieved. The validation using ATSRII data showed that the method was useful.

  20. A statistical method to get surface level air-temperature from satellite observations of precipitable water

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Shikauchi, A.; Sugimori, Y.; Kubota, M.

    Vol. 49, pp. 551 to 558. 1993 A Statistical Method to Get Surface Level Air-Temperature from Satellite Observations of Precipitable Water PANKAJAKSHAN THADATHIL*, AKIRA SHIKAUCHI, YASUHIRO SUGIMORI and MASAHISA KUBOTA School of Marine Science... observations for getting the estimates of heat flux across the air-sea boundary (Miller, 1981; Liu, 1988). Bulk method has widely been used for this purpose and the parameters required are: sea surface temperature, and wind speed, air-temperature and specific...

  1. Evaluation of Haney-Type Surface Thermal Boundary Conditions Using a Coupled Atmosphere and Ocean Model

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A coupled atmosphere-ocean model developed at the Institute for Space Studies at NASA Goddard Space Flight Center (Russell et al., 1995) was used to verify the validity of Haney-type surface thermal boundary condition, which linearly connects net downward surface heat flux Q to air / sea temperature difference △T by a relaxation coefficient k. The model was initiated from the National Centers for Environmental Prediction (NCEP) atmospheric observations for 1 December 1977, and from the National Ocean Data Center (NODC) global climatological mean December temperature and salinity fields at 1° ×1° resolution. The time step is 7.5 minutes. We integrated the model for 450 days and obtained a complete model-generated global data set of daily mean downward net surface flux Q, surface air temperature TA,and sea surface temperature To. Then, we calculated the cross-correlation coefficients (CCC) between Q and △T. The ensemble mean CCC fields show (a) no correlation between Q and △T in the equatorial regions, and (b) evident correlation (CCC≥ 0.7) between Q and △T in the middle and high latitudes.Additionally, we did the variance analysis and found that when k= 120 W m-2K-1, the two standard deviations, σrq and σk△T, are quite close in the middle and high latitudes. These results agree quite well with a previous research (Chu et al., 1998) on analyzing the NCEP re-analyzed surface data, except that a smaller value of k (80 W m-2K-1) was found in the previous study.

  2. Growing season boundary layer climate and surface exchanges in a subarctic lichen woodland

    Science.gov (United States)

    Fitzjarrald, David R.; Moore, Kathleen E.

    1994-01-01

    Between June and August 1990, observations were made at two surface micrometeorological towers near Schefferville Quebec (54 deg 52 min N, 66 deg 40.5 min W), one in a fen and one in the subarctic lichen woodland, and at four surface climatological stations. Data from these surface stations were supplemented by regular radiosonde launches. Supporting measurements of radiative components and soil temperatures allowed heat and moisture balances to be obtained at two sites. The overall surface meteorological experiment design and results of micrometeorological observations made on a 30-m tower in the lichen woodland are presented here. Seasonal variation in the heat and water vapor transport characteristics illustrate the marked effect of the late summer climatological shift in air mass type. During the first half of the summer, average valley sidewalls only 100 m high are sufficient to channel winds along the valley in the entire convective boundary layer. Channeling effects at the surface, known for some time at the long-term climate station in Schefferville, are observed both at ridge top and in the valley, possibly the response of the flow to the NW-SE orientation of valleys in the region. Diurnal surface temperature amplitude at ridge top (approximately equal to 10 C) was found to be half that observed in the valley. Relatively large differences in precipitation among these stations and the climatological station at Schefferville airport were observed and attributed to the local topography. Eddy correlation observations of the heat, moisture and momentum transports were obtained from a 30-m tower above a sparse (approximately equal to 616 stems/ha) black spruce lichen woodland. Properties of the turbulent surface boundary layer agree well with previous wind tunnel studies over idealized rough surfaces. Daytime Bowen ratios of 2.5-3 are larger than those reported in previous studies. Surface layer flux data quality was assessed by looking at the surface layer heat

  3. Growing season boundary layer climate and surface exchanges in a subarctic lichen woodland

    Science.gov (United States)

    Fitzjarrald, David R.; Moore, Kathleen E.

    1994-01-01

    Between June and August 1990, observations were made at two surface micrometeorological towers near Schefferville Quebec (54 deg 52 min N, 66 deg 40.5 min W), one in a fen and one in the subarctic lichen woodland, and at four surface climatological stations. Data from these surface stations were supplemented by regular radiosonde launches. Supporting measurements of radiative components and soil temperatures allowed heat and moisture balances to be obtained at two sites. The overall surface meteorological experiment design and results of micrometeorological observations made on a 30-m tower in the lichen woodland are presented here. Seasonal variation in the heat and water vapor transport characteristics illustrate the marked effect of the late summer climatological shift in air mass type. During the first half of the summer, average valley sidewalls only 100 m high are sufficient to channel winds along the valley in the entire convective boundary layer. Channeling effects at the surface, known for some time at the long-term climate station in Schefferville, are observed both at ridge top and in the valley, possibly the response of the flow to the NW-SE orientation of valleys in the region. Diurnal surface temperature amplitude at ridge top (approximately equal to 10 C) was found to be half that observed in the valley. Relatively large differences in precipitation among these stations and the climatological station at Schefferville airport were observed and attributed to the local topography. Eddy correlation observations of the heat, moisture and momentum transports were obtained from a 30-m tower above a sparse (approximately equal to 616 stems/ha) black spruce lichen woodland. Properties of the turbulent surface boundary layer agree well with previous wind tunnel studies over idealized rough surfaces. Daytime Bowen ratios of 2.5-3 are larger than those reported in previous studies. Surface layer flux data quality was assessed by looking at the surface layer heat

  4. Characterisation of net type thermal insulators at 1.8 K low boundary temperature

    CERN Document Server

    Peón-Hernández, G; Szeless, Balázs

    1997-01-01

    The Large Hadron Collider's superconducting magnets are cooled by superfluid helium at 1.8 K and housed in cryostats that minimise the heat inleak to this temperature level by extracting heat at 70 and 5 K. In the first generation of prototype cryostats, the radiative heat to the 1.8 K temperature level accounted for 70 % of the total heat inleak. An alternative to enhance the cryostat thermal performance incorporates a thermalised radiation screen at 5 K. In order to avoid contact between the 5 K radiation screen and the cold mass, insulators are placed between both surfaces. Sets of commercial fibre glass nets are insulator candidates to minimise the heat inleak caused by a accidental contact between the two temperature levels. A model to estimate their performance is presented. A set-up to thermally characterise them has been designed and is also described in the paper. Finally, results as a function of the number of the spacer nets, the boundary temperatures and the compressive force in the spacer are pre...

  5. Evolution of microstructure and grain boundary character distribution of a tin bronze annealed at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Weijiu [College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Chongqing Municipal Key Laboratory of Institutions of Higher Education for Mould Technology, Chongqing University of Technology, Chongqing 400054 (China); Chai, Linjiang, E-mail: chailinjiang@cqut.edu.cn [College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Chongqing Municipal Key Laboratory of Institutions of Higher Education for Mould Technology, Chongqing University of Technology, Chongqing 400054 (China); Li, Zhijun; Yang, Xusheng [College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Guo, Ning; Song, Bo [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China)

    2016-04-15

    Specimens cut from a rolled tin bronze sheet were annealed at 400–800 °C for 1 h and evolution of their microstructures was then characterized in details by electron channeling contrast imaging and electron backscatter diffraction techniques. Particularly, statistics on special boundaries (SBs) with Σ ≤ 29 and network connectivity of random high angle boundaries (HABs) in the annealed specimens were examined to probe optimization potentials of grain boundary character distribution (GBCD) for this material. Results show that the deformed microstructure in the as-received material begins to be recrystallized when the annealing temperature increase to 500 °C and average grain sizes surge with further increasing temperatures. As a result of the recrystallization, a large number of annealing twins (with Σ3 misorientation) are produced, leading to remarkably increased fractions of SBs (f{sub SBs}). Thanks to preexisting dense low angle boundaries, the majority of SBs in the 500 °C specimen with only partial recrystallization are Σ3{sub ic} (incoherent) boundaries, which effectively disrupt connectivity of random HABs network. Although the f{sub SBs} can be further increased (up to 72.5%) in specimens with full recrystallization (at higher temperatures), the Σ3{sub ic} boundaries would be replaced to some extent by Σ3{sub c} (coherent) boundaries which do not contribute directly to optimizing the GBCD. This work should be able to provide clear suggestions on applying the concept of grain boundary engineering to tin bronze alloys. - Highlights: • The rolled tin bronze begins to be recrystallized as temperature increases to 500 °C. • A lot of SBs are produced after recrystallization and the highest f{sub SBs} is 72.5%. • Partially recrystallized specimen has the optimum GBCD due to more Σ3{sub ic} boundaries. • The Σ3{sub ic} boundaries are replaced by Σ3{sub c} boundaries after full recrystallization.

  6. Turbulence measurements in hypersonic boundary layers using constant-temperature anemometry and Reynolds stress measurements in hypersonic boundary layers

    Science.gov (United States)

    Spina, Eric F.

    1995-01-01

    The primary objective in the two research investigations performed under NASA Langley sponsorship (Turbulence measurements in hypersonic boundary layers using constant temperature anemometry and Reynolds stress measurements in hypersonic boundary layers) has been to increase the understanding of the physics of hypersonic turbulent boundary layers. The study began with an extension of constant-temperature thermal anemometry techniques to a Mach 11 helium flow, including careful examinations of hot-wire construction techniques, system response, and system calibration. This was followed by the application of these techniques to the exploration of a Mach 11 helium turbulent boundary layer (To approximately 290 K). The data that was acquired over the course of more than two years consists of instantaneous streamwise mass flux measurements at a frequency response of about 500 kHz. The data are of exceptional quality in both the time and frequency domain and possess a high degree of repeatability. The data analysis that has been performed to date has added significantly to the body of knowledge on hypersonic turbulence, and the data reduction is continuing. An attempt was then made to extend these thermal anemometry techniques to higher enthalpy flows, starting with a Mach 6 air flow with a stagnation temperature just above that needed to prevent liquefaction (To approximately 475 F). Conventional hot-wire anemometry proved to be inadequate for the selected high-temperature, high dynamic pressure flow, with frequent wire breakage and poor system frequency response. The use of hot-film anemometry has since been investigated for these higher-enthalpy, severe environment flows. The difficulty with using hot-film probes for dynamic (turbulence) measurements is associated with construction limitations and conduction of heat into the film substrate. Work continues under a NASA GSRP grant on the development of a hot film probe that overcomes these shortcomings for hypersonic

  7. LIMIT BEHAVIOUR OF SOLUTIONS TO EQUIVALUED SURFACE BOUNDARY VALUE PROBLEM FOR PARABOLIC EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    LiFengquan

    2002-01-01

    In this paper,we discuss the limit behaviour of solutions to equivalued surface boundayr value problem for parabolic equatiopns when the equivalued surface boundary shriks to a point and the space dimension of the domain is two or more.

  8. Dominance of pollutant aerosols over an urban region and its impact on boundary layer temperature profile

    Science.gov (United States)

    Talukdar, Shamitaksha; Jana, Soumyajyoti; Maitra, Animesh

    2017-01-01

    Collocated measurements of aerosol optical depth (AOD) and black carbon at different wavelengths over Kolkata, an urban region in eastern India, have been used to calculate aerosol single-scattering albedo (SSA). The wavelength dependence of SSA and AOD has been presented to discriminate the aerosol types over this highly populated metropolitan area. The spectral pattern shows that SSA decreases with wavelength for most of the time in a year and corresponding Ångström coefficient is greater than unity. These optical properties indicate the dominance of fine-mode pollutant particles over the city. The temperature lapse rate profile within the surface boundary layer has been found to be significantly influenced by the heating effect of fine-mode pollutants, and consequently, the growth of the convective processes in the lower troposphere is notably affected. In addition, a back trajectory analysis has also been presented to indicate that transported air masses can have significant impact on spectral pattern of SSA.

  9. Design and construction of a low-velocity boundary-layer temperature probe

    Science.gov (United States)

    Blackwell, B. F.; Moffat, R. J.

    1974-01-01

    This paper presents the results of a study performed to determine the probe geometry and thermal characteristics for a low-velocity boundary-layer temperature probe capable of eliminating conduction errors. Design curves for four common thermoelectric pairs are presented, and an experimental turbulent boundary-layer temperature profile is compared with the theoretical laminar sublayer equation to verify that the probe eliminates conduction errors.

  10. Nonlinear Radiation Effects on Hydromagnetic Boundary Layer Flow and Heat Transfer over a Shrinking Surface

    Directory of Open Access Journals (Sweden)

    anjali devi

    2015-01-01

    Full Text Available The effects of nonlinear radiation on hydromagnetic boundary layer flow and heat transfer over a shrinking surface is investigated in the present work. Using suitable similarity transformations, the governing nonlinear partial differential equations are transformed into nonlinear ordinary differential equations. The resultant equations which are highly nonlinear are solved numerically using Nachtsheim Swigert shooting iteration scheme together with Fourth Order Runge Kutta method. Numerical solutions for velocity, skin friction coefficient and temperature are obtained for various values of physical parameters involved in the study namely Suction parameter, Magnetic parameter, Prandtl number, Radiation parameter and Temperature ratio parameter. Numerical values for dimensionless rate of heat transfer are also obtained for various physical parameters and are shown through tables. The analytical solution of the energy equation when the radiation term is taken in linear form is obtained using Confluent hypergeometric function.

  11. Wind and temperature profiles in the boundary layer above the Kruger National Park during SAFARI-92

    Science.gov (United States)

    Held, G.

    1996-10-01

    The experimental phase of SAFARI-92 in the Kruger National Park took place from September 7 to 26, 1992. Eskom's Environmental Sciences was committed to provide meteorological support during the experimental burns in the Pretoriuskop area of the KNP and to characterize the boundary layer during the field campaign. Surface temperature inversions were found during most nights when vertical soundings were available. The inversion strength was generally ≤3.5° with a depth of ≤270 m above ground level (agl). Low-level elevated inversions with a base height of 350 to 500 m agl and a strength of ≤3.6°C were found on four occasions. The base height of the subsidence inversion, when observed, varied between 1500 and 2500 m agl. Significant superadiabatic temperature gradients, impacting directly on the vertical dispersion of pyrogenic products, have been observed to reach as high as several hundred meters above ground level. Vertical profiles of wind speed and direction varied greatly from day to day in response to the changes in the synoptic pattern. However, weak low-level wind maxima just above the surface inversion were observed during most nights, generally with speeds of <10 m s-1. Detailed case studies of boundary layer conditions during the major burns have been included. Since the observations were made during spring it is suggested that the results could be more characteristic of summer conditions. It can be assumed that the inversions will be stronger and the low-level wind maxima more pronounced during winter.

  12. A Low Temperature Analysis of the Boundary Driven Kawasaki Process

    Science.gov (United States)

    Maes, Christian; O'Kelly de Galway, Winny

    2013-12-01

    Low temperature analysis of nonequilibrium systems requires finding the states with the longest lifetime and that are most accessible from other states. We determine these dominant states for a one-dimensional diffusive lattice gas subject to exclusion and with nearest neighbor interaction. They do not correspond to lowest energy configurations even though the particle current tends to zero as the temperature reaches zero. That is because the dynamical activity that sets the effective time scale, also goes to zero with temperature. The result is a non-trivial asymptotic phase diagram, which crucially depends on the interaction coupling and the relative chemical potentials of the reservoirs.

  13. Temperature limit values for gripping cold surfaces

    NARCIS (Netherlands)

    Malchaire, J.; Geng, Q.; Den Hartog, E.; Havenith, G.; Holmer, I.; Piette, A.; Powell, S.L.; Rintamäki, H.; Rissanen, S.

    2002-01-01

    Objectives. At the request of the European Commission and in the framework of the European Machinery Directive, research was conducted jointly in five different laboratories to develop specifications for surface temperature limit values for the gripping and handling of cold items. Methods. Four

  14. Temperature limit values for gripping cold surfaces

    NARCIS (Netherlands)

    Malchaire, J.; Geng, Q.; Den Hartog, E.; Havenith, G.; Holmer, I.; Piette, A.; Powell, S.L.; Rintamäki, H.; Rissanen, S.

    2002-01-01

    Objectives. At the request of the European Commission and in the framework of the European Machinery Directive, research was conducted jointly in five different laboratories to develop specifications for surface temperature limit values for the gripping and handling of cold items. Methods. Four hund

  15. Surface temperature excess in heterogeneous catalysis

    NARCIS (Netherlands)

    Zhu, L.

    2005-01-01

    In this dissertation we study the surface temperature excess in heterogeneous catalysis. For heterogeneous reactions, such as gas-solid catalytic reactions, the reactions take place at the interfaces between the two phases: the gas and the solid catalyst. Large amount of reaction heats are released

  16. Surface temperature excess in heterogeneous catalysis

    NARCIS (Netherlands)

    Zhu, L.

    2005-01-01

    In this dissertation we study the surface temperature excess in heterogeneous catalysis. For heterogeneous reactions, such as gas-solid catalytic reactions, the reactions take place at the interfaces between the two phases: the gas and the solid catalyst. Large amount of reaction heats are released

  17. Trend patterns in global sea surface temperature

    DEFF Research Database (Denmark)

    Barbosa, S.M.; Andersen, Ole Baltazar

    2009-01-01

    Isolating long-term trend in sea surface temperature (SST) from El Nino southern oscillation (ENSO) variability is fundamental for climate studies. In the present study, trend-empirical orthogonal function (EOF) analysis, a robust space-time method for extracting trend patterns, is applied...

  18. DISAGGREGATION OF GOES LAND SURFACE TEMPERATURES USING SURFACE EMISSIVITY

    Science.gov (United States)

    Accurate temporal and spatial estimation of land surface temperatures (LST) is important for modeling the hydrological cycle at field to global scales because LSTs can improve estimates of soil moisture and evapotranspiration. Using remote sensing satellites, accurate LSTs could be routine, but unfo...

  19. Surface defects and temperature on atomic friction

    Energy Technology Data Exchange (ETDEWEB)

    Fajardo, O Y; Mazo, J J, E-mail: yovany@unizar.es [Departamento de Fisica de la Materia Condensada and Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain)

    2011-09-07

    We present a theoretical study of the effect of surface defects on atomic friction in the stick-slip dynamical regime of a minimalistic model. We focus on how the presence of defects and temperature change the average properties of the system. We have identified two main mechanisms which modify the mean friction force of the system when defects are considered. As expected, defects change the potential profile locally and thus affect the friction force. But the presence of defects also changes the probability distribution function of the tip slip length and thus the mean friction force. We corroborated both effects for different values of temperature, external load, dragging velocity and damping. We also show a comparison of the effects of surface defects and surface disorder on the dynamics of the system. (paper)

  20. Surface temperature distribution in broiler houses

    Directory of Open Access Journals (Sweden)

    MS Baracho

    2011-09-01

    Full Text Available In the Brazilian meat production scenario broiler production is the most dynamic segment. Despite of the knowledge generated in the poultry production chain, there are still important gaps on Brazilian rearing conditions as housing is different from other countries. This research study aimed at analyzing the variation in bird skin surface as function of heat distribution inside broiler houses. A broiler house was virtually divided into nine sectors and measurements were made during the first four weeks of the grow-out in a commercial broiler farm in the region of Rio Claro, São Paulo, Brazil. Rearing ambient temperature and relative humidity, as well as light intensity and air velocity, were recorded in the geometric center of each virtual sector to evaluate the homogeneity of these parameters. Broiler surface temperatures were recorded using infrared thermography. Differences both in surface temperature (Ts and dry bulb temperature (DBT were significant (p<0.05 as a function of week of rearing. Ts was different between the first and fourth weeks (p<0.05 in both flocks. Results showed important variations in rearing environment parameters (temperature and relative humidity and in skin surface temperature as a function of week and house sector. Air velocity data were outside the limits in the first and third weeks in several sectors. Average light intensity values presented low variation relative to week and house sector. The obtained values were outside the recommended ranges, indicating that broilers suffered thermal distress. This study points out the need to record rearing environment data in order to provide better environmental control during broiler grow-out.

  1. Boundary layer flow near a stagnation point on a permeable vertical surface immersed in a nanofluid

    Science.gov (United States)

    Othman, Noor Adila; Yacob, Nor Azizah; Bachok, Norfifah; Ramli, Nazirah; Ishak, Anuar

    2015-10-01

    A steady mixed convection boundary layer flow near a stagnation point on a permeable vertical surface immersed in a nanofluid is investigated. The velocity of the external flow is assumed to vary linearly with the distance from the stagnation-point. The governing partial differential equations are first transformed into ordinary differential equations, before being solved numerically using the Keller box method with the help of MATLAB software. The effects of physical parameters such as the suction/injection parameter, Brownian motion parameter, thermophoresis parameter and Lewis number on the heat and mass transfer rate at the surface as well as the temperature and concentration profiles are analyzed and discussed. Both assisting and opposing flows are considered. It is found that, increasing the thermophoresis parameter, Brownian motion parameter and Lewis number are to decrease the heat transfer rate at the surface, but on the other hand increase the mass transfer rate at the surface for both assisting and opposing flows. In addition, increasing suction parameter tends to increase the heat transfer rate at the surface. However, the opposite behavior occurs for the effect of mass transfer rate at the surface.

  2. On inferring isoprene emission surface flux from atmospheric boundary layer concentration measurements

    Directory of Open Access Journals (Sweden)

    J. Vilà-Guerau de Arellano

    2009-06-01

    Full Text Available We examine the dependence of the inferred isoprene surface emission flux from atmospheric concentration on the diurnal variability of the convective boundary layer (CBL. A series of systematic numerical experiments carried out using the mixed-layer technique enabled us to study the sensitivity of isoprene fluxes to the entrainment process, the partition of surface fluxes, the horizontal advection of warm/cold air masses and subsidence. Our findings demonstrate the key role played by the evolution of boundary layer height in modulating the retrieved isoprene flux. More specifically, inaccurate values of the potential temperature lapse rate lead to changes in the dilution capacity of the CBL and as a result the isoprene flux may be overestimated or underestimated by as much as 20%. The inferred emission flux estimated in the early morning hours is highly dependent on the accurate estimation of the discontinuity of the thermodynamic values between the residual layer and the rapidly forming CBL. Uncertainties associated with the partition of the sensible and latent heat flux also yield large deviations in the calculation of the isoprene surface flux. Similar results are obtained if we neglect the influence of warm or cold advection in the development of the CBL. We show that all the above-mentioned processes are non-linear, for which reason the dynamic and chemical evolutions of the CBL must be solved simultaneously. Based on the discussion of our results, we suggest the measurements needed to correctly apply the mixed-layer technique in order to minimize the uncertainties associated with the diurnal variability of the convective boundary layer.

  3. On inferring isoprene emission surface flux from atmospheric boundary layer concentration measurements

    Directory of Open Access Journals (Sweden)

    J. Vilà-Guerau de Arellano

    2009-02-01

    Full Text Available We examine the dependence of the inferred isoprene surface emission flux from atmospheric concentration on the diurnal variability of the convective boundary layer (CBL. A series of systematic numerical experiments carried out using the mixed-layer technique enabled us to study the sensitivity of isoprene fluxes to the entrainment process, the partition of surface fluxes, the horizontal advection of warm/cold air masses and subsidence. Our findings demonstrate the key role played by the evolution of boundary layer height in modulating the retrieved isoprene flux. More specifically, inaccurate values of the potential temperature lapse rate lead to changes in the dilution capacity of the CBL and as a result the isoprene flux may be overestimated or underestimated by as much as 20%. The inferred emission flux estimated in the early morning hours is highly dependent on the accurate estimation of the discontinuity of the thermodynamic values between the residual layer and the rapidly forming CBL. Uncertainties associated with the partition of the sensible and latent heat flux also yield large deviations in the calculation of the isoprene surface flux. Similar results are obtained if we neglect the influence of warm or cold advection in the development of the CBL. We show that all the above-mentioned processes are non-linear, for which reason the dynamic and chemical evolutions of the CBL must be solved simultaneously. Based on the discussion of our results, we suggest the measurements needed to correctly apply the mixed-layer technique in order to minimize the uncertainties associated with the diurnal variability of the convective boundary layer.

  4. Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

    Directory of Open Access Journals (Sweden)

    N. A. Brunsell

    2011-04-01

    Full Text Available The role of land-atmosphere interactions under heterogeneous surface conditions is investigated in order to identify mechanisms responsible for altering surface heat and moisture fluxes. Twelve coupled land surface – large eddy simulation scenarios with four different length scales of surface variability under three different horizontal wind speeds are used in the analysis. The base case uses Landsat ETM imagery over the Cloud Land Surface Interaction Campaign (CLASIC field site for 3 June 2007. Using wavelets, the surface fields are band-pass filtered in order to maintain the spatial mean and variances to length scales of 200 m, 1600 m, and 12.8 km as lower boundary conditions to the model (approximately 0.25, 1.2 and 9.5 times boundary layer height. The simulations exhibit little variation in net radiation. Rather, there is a pronounced change in the partitioning of the surface energy between sensible and latent heat flux. The sensible heat flux is dominant for intermediate surface length scales. For smaller and larger scales of surface heterogeneity, which can be viewed as being more homogeneous, the latent heat flux becomes increasingly important. The simulations showed approximately 50 Wm−2 difference in the spatially averaged latent heat flux. The results reflect a general decrease of the Bowen ratio as the surface conditions transition from heterogeneous to homogeneous. Air temperature is less sensitive to variations in surface heterogeneity than water vapor, which implies that the role of surface heterogeneity may be to maximize convective heat fluxes through modifying and maintaining local temperature gradients. More homogeneous surface conditions (i.e. smaller length scales, on the other hand, tend to maximize latent heat flux. The intermediate scale (1600 m this does not hold, and is a more complicated interaction of scales. Scalar vertical profiles respond predictably to the partitioning of surface energy. Fourier

  5. Geomagnetic effects on the average surface temperature

    Science.gov (United States)

    Ballatore, P.

    Several results have previously shown as the solar activity can be related to the cloudiness and the surface solar radiation intensity (Svensmark and Friis-Christensen, J. Atmos. Sol. Terr. Phys., 59, 1225, 1997; Veretenenkoand Pudovkin, J. Atmos. Sol. Terr. Phys., 61, 521, 1999). Here, the possible relationships between the averaged surface temperature and the solar wind parameters or geomagnetic activity indices are investigated. The temperature data used are the monthly SST maps (generated at RAL and available from the related ESRIN/ESA database) that represent the averaged surface temperature with a spatial resolution of 0.5°x0.5° and cover the entire globe. The interplanetary data and the geomagnetic data are from the USA National Space Science Data Center. The time interval considered is 1995-2000. Specifically, possible associations and/or correlations of the average temperature with the interplanetary magnetic field Bz component and with the Kp index are considered and differentiated taking into account separate geographic and geomagnetic planetary regions.

  6. Temperature statistics above a deep-ocean sloping boundary

    CERN Document Server

    Cimatoribus, Andrea A

    2015-01-01

    We present a detailed analysis of the statistics of temperature in an oceanographic observational dataset. The data is collected using a moored array of thermistors, 100m tall and starting 5m above the bottom, deployed during four months above the slopes of a seamount in the North Eastern Atlantic Ocean. Turbulence at this location is strongly affected by the semidiurnal tidal wave. Mean stratification is stable in the entire dataset. We compute structure functions, of order up to 10, of the distributions of temperature increments. Strong intermittency is observed in particular during the downslope phase of the tide, and farther from the solid bottom. In the lower half of the mooring during the upslope phase, the statistics of temperature are consistent with those of a passive scalar. In the upper half of the mooring, the statistics of temperature deviate from those of a passive scalar, and evidence of turbulent convective activity is found. The downslope phase is generally thought to be more shear dominated,...

  7. Boundary Slip and Surface Interaction: A Lattice Boltzmann Simulation

    Institute of Scientific and Technical Information of China (English)

    CHEN Yan-Yan; YI Hou-Hui; LI Hua-Bing

    2008-01-01

    The factors affecting slip length in Couette geometry flows are analysed by means of a two-phase mesoscopic lattice Boltzmann model including non-ideal fluid-fluid and fluid-wall interactions.The main factors influencing the boundary slip are the strength of interactions between fluid-fluid and fluid-wall particles.Other factors,such as fluid viscosity,bulk pressure may also change the slip length.We find that boundary slip only occurs under a certain density(bulk pressure).If the density is large enough,the slip length will tend to zero.In our simulations,a low density layer near the wall does not need to be postulated a priori but emerges naturally from the underlying non-ideal mesoscopic dynamics.It is the low density layer that induces the boundary slip.The results may be helpful to understand recent experimental observations on the slippage of micro flows.

  8. The asymptotic equivalence of fixed heat flux and fixed temperature thermal boundary conditions for rapidly rotating convection

    CERN Document Server

    Calkins, Michael A; Julien, Keith; Nieves, David; Driggs, Derek; Marti, Philippe

    2015-01-01

    The influence of fixed temperature and fixed heat flux thermal boundary conditions on rapidly rotating convection in the plane layer geometry is investigated for the case of stress-free mechanical boundary conditions. It is shown that whereas the leading order system satisfies fixed temperature boundary conditions implicitly, a double boundary layer structure is necessary to satisfy the fixed heat flux thermal boundary conditions. The boundary layers consist of a classical Ekman layer adjacent to the solid boundaries that adjust viscous stresses to zero, and a layer in thermal wind balance just outside the Ekman layers adjusts the temperature such that the fixed heat flux thermal boundary conditions are satisfied. The influence of these boundary layers on the interior geostrophically balanced convection is shown to be asymptotically weak, however. Upon defining a simple rescaling of the thermal variables, the leading order reduced system of governing equations are therefore equivalent for both boundary condit...

  9. Turbulent boundary layer on perforated surfaces with vector injection

    Science.gov (United States)

    Eroshenko, V. M.; Zaichik, L. I.; Klimov, A. A.; Ianovskii, L. S.; Kondratev, V. I.

    1980-10-01

    The paper presents an experimental investigation of a turbulent boundary layer on perforated plates with uniform vector injection at various angles to gas flow. It was shown that with strong injection at angles oriented in the flow direction the intensity of turbulent pulsation is decreased, while injection at angles in the opposite direction increase the intensity. A relationship was established between the critical parameters of the boundary layer injection angles; it was concluded that the asymptotic theory of Kutateladze and Leontiev can be used for determining the coefficient of friction of vector injection.

  10. Magnetohydrodynamic boundary layer nanofluid flow and heat transfer over a stretching surface

    Science.gov (United States)

    Ali, M.; Alim, M. A.; Nasrin, R.; Alam, M. S.; Chowdhury, M. Z. U.

    2017-06-01

    The present study is performed to investigate the effect of unsteadiness, stretching ratio, Brownian motion, thermophoresis and magnetic parameter on boundary layer such as momentum, thermal and nanoparticle concentration. In this respect we have considered the magnetohydrodynamic (MHD) unsteady boundary layer nanofluid flow and heat - mass transfer over a stretching surface. The dimensionless governing equations are unsteady, two-dimensional coupled and non-linear ordinary differential equations. The numerical solution is taken by applying the Nachtsgeim-Swigert shooting iteration technique along with Runge-Kutta integration scheme. The effects of various dimensionless parameters on velocity, temperature and nanoparticle concentration are discussed numerically and shown graphically. Therefore, from the figures it is observed that the results of velocity profile increases for increasing values of magnetic parameter and unsteadiness parameter but decreases for stretching ratio parameter, the temperature profile decreases in presence of Brownian motion, unsteadiness parameter, stretching ratio parameter and thermophoresis parameter but increases for magnetic parameter and, the nanoparticle concentration decreases for increasing values of thermophoresis parameter, unsteadiness parameter and stretching ratio parameter whereas the reverse trend arises for Brownian motion & magnetic parameter. For validity and accuracy the present results are compared with previously published work and found good agreement.

  11. Heat and mass transfer boundary conditions at the surface of a heated sessile droplet

    Science.gov (United States)

    Ljung, Anna-Lena; Lundström, T. Staffan

    2017-07-01

    This work numerically investigates how the boundary conditions of a heated sessile water droplet should be defined in order to include effects of both ambient and internal flow. Significance of water vapor, Marangoni convection, separate simulations of the external and internal flow, and influence of contact angle throughout drying is studied. The quasi-steady simulations are carried out with Computational Fluid Dynamics and conduction, natural convection and Marangoni convection are accounted for inside the droplet. For the studied conditions, a noticeable effect of buoyancy due to evaporation is observed. Hence, the inclusion of moisture increases the maximum velocities in the external flow. Marangoni convection will, in its turn, increase the velocity within the droplet with up to three orders of magnitude. Results furthermore show that the internal and ambient flow can be simulated separately for the conditions studied, and the accuracy is improved if the internal temperature gradient is low, e.g. if Marangoni convection is present. Simultaneous simulations of the domains are however preferred at high plate temperatures if both internal and external flows are dominated by buoyancy and natural convection. The importance of a spatially resolved heat and mass transfer boundary condition is, in its turn, increased if the internal velocity is small or if there is a large variation of the transfer coefficients at the surface. Finally, the results indicate that when the internal convective heat transport is small, a rather constant evaporation rate may be obtained throughout the drying at certain conditions.

  12. Retrieving 4-dimensional atmospheric boundary layer structure from surface observations and profiles over a single station

    Energy Technology Data Exchange (ETDEWEB)

    Pu, Zhaoxia [Univ. of Utah, Salt Lake City, UT (United States)

    2015-10-06

    Most routine measurements from climate study facilities, such as the Department of Energy’s ARM SGP site, come from individual sites over a long period of time. While single-station data are very useful for many studies, it is challenging to obtain 3-dimensional spatial structures of atmospheric boundary layers that include prominent signatures of deep convection from these data. The principal objective of this project is to create realistic estimates of high-resolution (~ 1km × 1km horizontal grids) atmospheric boundary layer structure and the characteristics of precipitating convection. These characteristics include updraft and downdraft cumulus mass fluxes and cold pool properties over a region the size of a GCM grid column from analyses that assimilate surface mesonet observations of wind, temperature, and water vapor mixing ratio and available profiling data from single or multiple surface stations. The ultimate goal of the project is to enhance our understanding of the properties of mesoscale convective systems and also to improve their representation in analysis and numerical simulations. During the proposed period (09/15/2011–09/14/2014) and the no-cost extension period (09/15/2014–09/14/2015), significant accomplishments have been achieved relating to the stated goals. Efforts have been extended to various research and applications. Results have been published in professional journals and presented in related science team meetings and conferences. These are summarized in the report.

  13. The Lowest Atmosphere: Atmospheric Boundary Layer Including Atmospheric Surface Layer.

    Science.gov (United States)

    1996-04-01

    of motion of the atmosphere— "second order closure"—to such applications as the SCIPUFF -PC code for tracer dispersion (see Sykes, 1994). Now, for...Turbulence, Methuen, London, 2nd Ed., 1955. Sykes, R.I., "The SCIPUFF -PC Code," ARAP Draft Report, 1994. Tennekes, H., "The Atmospheric Boundary Layer

  14. Radiation and Viscous Dissipation Effects on Laminar Boundary Layer Flow Nanofluid over a Vertical Plate with a Convective Surface Boundary Condition with Suction

    Directory of Open Access Journals (Sweden)

    K. Gangadhar

    2016-01-01

    Full Text Available The problem of laminar radiation and viscous dissipation effects on laminar boundary layer flow over a vertical plate with a convective surface boundary condition is studied using different types of nanoparticles. The general governing partial differential equations are transformed into a set of two nonlinear ordinary differential equations using unique similarity transformation. Numerical solutions of the similarity equations are obtained using the Nachtsheim-Swigert Shooting iteration technique along with the fourth order Runga Kutta method. Two different types of nanoparticles copper water nanofluid and alumina water nanofluid are studied. The effects of radiation and viscous dissipation on the heat transfer characteristics are discussed in detail. It is observed that as Radiation parameter increases, temperature decreases for copper water and alumina water nanofluid and the heat transfer coefficient of nanofluids increases with the increase of convective heat transfer parameter for copper water and alumina water nanofluids.

  15. Geometric Conversion Approach for the Numerical Evaluation of Hypersingular and Nearly Hypersingular Boundary Integrals over Curved Surface Boundary Elements

    Institute of Scientific and Technical Information of China (English)

    马杭

    2002-01-01

    With the aid of the properties of the hypersingular kernels,a geometric conversion approach was presented in this paper.The conversion leads to a general approach for the accurate and reliable numerical evaluation of the hypersingular surface boundary integrals encountered in a variety of applications with boundary element method.Based on the conversion,the hypersingularity in the boundary integrals could be lowered by one order,resulting in the simplification of the computer code.Moreover,an integral transformation was introduced to damp out the nearly singular behavior of the kernels by the distance function defined in the local polar coordinate system for the nearly hypersingular case.The approach is simple to use,which can be inserted readily to computer code,thus getting rid of the dull routine deduction of formulae before the numerical implementatins,as the expressions of these kernels are in general complicated.The numerical examples were gien in three-dimensional elasticity,verifying the effectiveness of the proposed approach,which makes it possible to observe numerically the behavior of the boundary integral values with hypersingular kernels across the boundary.

  16. Two-phase boundary layer flow and heat transfer with temperature-dependent viscosity and nonzero pressure gradient

    Energy Technology Data Exchange (ETDEWEB)

    Randelia, R.R.; Sahai, V.

    1987-01-01

    A numerical analysis of a two-phase, laminar boundary layer is carried out using the Keller Box method. The two phases are assumed to be immiscible. The problem considered involves the boundary layer flow of a compressible gas with variable properties over a flat surface in the presence of a thin liquid film with power law temperature dependent viscosity. Both zero and nonzero pressure gradients are considered. The main purpose of the study was to investigate the effect of the presence of the liquid layer on the velocity and temperature distributions. A limited set of results are presented in terms of varying liquid Prandtl numbers, film thickness, and viscosity exponents on these distributions as well as the shear stress and heat transfer parameters at the wall and at the interface between the two fluids.

  17. Towards operational determination of boundary layer height using sodar/RASS soundings and surface heat flux data

    Energy Technology Data Exchange (ETDEWEB)

    Kirtzel, H.J. [METEK GmbH, Elmshorn (Germany); Hennemuth, B.

    2008-06-15

    A method for the derivation of boundary layer height from measurements of sodar, RASS and sonic anemometer-thermometer data is presented. Datasets of the years 2004 and 2005 measured at the Meteorological Observatory Lindenberg (Germany) are used. The time resolution is 15 min. Special emphasis is laid on air pollution issues where mixing heights shallower than 500 m are important. A difference to the numerous methods already presented in the literature is twofold. Firstly, not only single vertical profiles of measured or derived parameters are used but also bulk information, e.g. histograms and boundary layer evolution over time intervals, is considered. Secondly, the presented method analyses sodar data and confirms or corrects the results by use of temperature profiles from RASS and by sonic surface heat flux data. The results are presented as frequency distributions for the whole period and for the four seasons, stratified by the hour of the day. The additional analysis of temperature profiles and surface heat flux is particularly helpful for the detection of stable boundary layers and increases the number of shallow boundary layers particularly in the evening. The comparison with radiosonde-derived boundary layer heights shows a good agreement, deviations are mostly due to a complicated boundary layer structure. Boundary layer depths derived after a formalism given in the German administrative regulation TA-Luft show - compared to the sodar/RASS-derived values - too many very small or partly very large values. The height range between 100 m and 300 m which is essential for pollutant dispersion issues is nearly missing. Requirements for a future operational use of the method are formulated. (orig.)

  18. MODIS Surface Temperatures for Cryosphere Studies (Invited)

    Science.gov (United States)

    Hall, D. K.; Comiso, J. C.; DiGirolamo, N. E.; Shuman, C. A.; Riggs, G. A.

    2013-12-01

    We have used Moderate-resolution Imaging Spectroradiometer (MODIS) land-surface temperature (LST) and ice-surface temperature (IST) products for several applications in studies of the cryosphere. A climate-quality climate data record (CDR) of the IST of the Greenland ice sheet has been developed and was one of the data sources used to monitor the extreme melt event covering nearly the entire Greenland ice sheet on 11 - 12 July 2012. The IST CDR is available online for users to employ in models, and to study temperature distributions and melt trends on the ice sheet. We continue to assess accuracy of the IST product through comparative analysis with air temperature data from the NOAA Logan temperature sensor at Summit Station, Greenland. We find a small offset between the air temperature and the IST with the IST being slightly lower which is consistent with findings of other studies. The LST data product has been applied in studies of snow melt in regions where snow is a significant water resource. We have used LST data in seasonally snow-covered areas such as the Wind River Range, Wyoming, to monitor the relationship between LST and seasonal streamflow. A close association between a sudden and sustained increase in LST and complete snowmelt, and between melt-season maximum LST and maximum daily streamflow has been documented. Use of LST and MODIS snow-cover and products in hydrological models increases the accuracy of the modeled prediction of runoff. The IST and LST products have also been applied to study of sea ice, e.g. extent and concentration, and lake ice, such as determining ice-out dates, and these efforts will also be described.

  19. Finite temperature effect on mechanical properties of graphene sheets with various grain boundaries

    Science.gov (United States)

    Yong, Ge; Hong-Xiang, Sun; Yi-Jun, Guan; Gan-He, Zeng

    2016-06-01

    The mechanical properties of graphene sheets with various grain boundaries are studied by molecular dynamics method at finite temperatures. The finite temperature reduces the ultimate strengths of the graphenes with different types of grain boundaries. More interestingly, at high temperatures, the ultimate strengths of the graphene with the zigzag-orientation grain boundaries at low tilt angles exhibit different behaviors from those at lower temperatures, which is determined by inner initial stress in grain boundaries. The results indicate that the finite temperature, especially the high one, has a significant effect on the ultimate strength of graphene with grain boundaries, which gives a more in-depth understanding of their mechanical properties and could be useful for potential graphene applications. Project supported by the Nation Natural Science Foundation of China (Grant Nos. 11347219 and 11404147), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20140519), the Training Project of Young Backbone Teacher of Jiangsu University, the Advanced Talents of Jiangsu University, China (Grant No. 11JDG118), the Practice Innovation Training Program Projects for Industrial Center of Jiangsu University, China, and the State Key Laboratory of Acoustics, Chinese Academy of Sciences (Grant No. SKLOA201308).

  20. Lie symmetry analysis of a double-diffusive free convective slip flow with a convective boundary condition past a radiating vertical surface embedded in a porous medium

    Science.gov (United States)

    Afify, A. A.; Uddin, Md. J.

    2016-09-01

    A numerical study of a steady two-dimensional double-diffusive free convection boundary layer flow over a vertical surface embedded in a porous medium with slip flow and convective boundary conditions, heat generation/absorption, and solar radiation effects is performed. A scaling group of transformations is used to obtain the governing boundary layer equations and the boundary conditions. The transformed equations are then solved by the fourth- and fifth-order Runge-Kutta-Fehlberg numerical method with Maple 13. The results for the velocity, temperature, and concentration profiles, as well as the skin friction coefficient, the Nusselt number, and the Sherwood number are presented and discussed.

  1. Sensitivity of Tropical-Cyclone Models to the Surface Drag Coefficient in Different Boundary-Layer Schemes

    Science.gov (United States)

    2014-04-01

    2006). The far-field temperature and humidity are based on Jordan’s Caribbean sounding for the hurricane season (Jordan, 1958). For the purpose of...in this direction. Key Words: hurricanes ; tropical cyclones; typhoons; surface drag coefficient; frictional drag; boundary layer Received 16 June 2010...using one of five available schemes were compared, not only between themselves, but where possible with recent observational analyses of hurricane

  2. Scaling analysis of the mean and variariance of temperature in a developing thermal boundary layer

    Science.gov (United States)

    Byers, Clayton; Hultmark, Marcus

    2016-11-01

    A developing thermal boundary layer in a turbulent boundary layer is investigated both theoretically and experimentally. A scaling analysis of the mean temperature field and temperature variance, 1/2 θ2 , is developed by utilizing the "Asymptotic Invariance Principle" developed by George and Castillo (1997), including the possible effects of the Reynolds and Prandtl number. The derived solution for the inner and outer scaling is then used to develop a "heat transfer law" for the wall heat flux, qw. The condition of constant wall temperature is utilized, with an analysis of the temperature field treated as a passive scalar through ensuring the temperature differences remain small. Data collection is performed with a nanoscale temperature sensor, providing an improvement to performance over previous cold wire data acquisition. Supported by NSF (CBET-1510100 program manager Dimitrios Papavassiliou) and ONR (N00014-12-1-0875 and N00014-12-1-0962 program manager Ki-Han Kim).

  3. Turbulent Prandtl number and space-time temperature correlation measurements in an incompressible turbulent boundary layer

    Science.gov (United States)

    Bagheri, Nader; Strataridakis, Constantine J.; White, Bruce R.

    1990-01-01

    Hot-wire anemometry measurements in an incompressible turbulent boundary laeyr flow over a heated flat plate at zero pressure gradient were made using an x-probe and temperature fluctuation probe. The experiments resulted in direct measurement of the turbulent Prandtl number as a function of height through the boundary layer for three temperature difference cases. Also, space-time correlations of temperature fluctuations T-prime were obtained with a pair of temperature fluctuation probes. The mean convection velocities of the T-prime large-scale structure are presented for the three temperature difference cases. The mean convection velocity of the T-prime structure is a function of position y(+) and is found to be independent of the temperature difference for the cases considered.

  4. Combined effects of surface conditions, boundary layer dynamics and chemistry on diurnal SOA evolution

    NARCIS (Netherlands)

    Janssen, R.H.H.; Vilà-Guerau de Arellano, J.; Ganzeveld, L.N.; Kabat, P.; Jimenez, J.L.; Farmer, D.K.; Heerwaarden, van C.C.; Mammarella, I.

    2012-01-01

    We study the combined effects of land surface conditions, atmospheric boundary layer dynamics and chemistry on the diurnal evolution of biogenic secondary organic aerosol in the atmospheric boundary layer, using a model that contains the essentials of all these components. First, we evaluate the mod

  5. Fixed-scale approach to finite-temperature lattice QCD with shifted boundaries

    CERN Document Server

    Umeda, Takashi

    2014-01-01

    We study the thermodynamics of the SU(3) gauge theory using the fixed-scale approach with shifted boundary conditions. The fixed-scale approach can reduce the numerical cost of the zero-temperature part in the equation of state calculations, while the number of possible temperatures is limited by the integer $N_t$, which represents the temporal lattice extent. The shifted boundary conditions can overcome such a limitation while retaining the advantages of the fixed-scale approach. Therefore, our approach enables the investigation of not only the equation of state in detail, but also the calculation of the critical temperature with increased precision even with the fixed-scale approach. We also confirm numerically that the boundary conditions suppress the lattice artifact of the equation of state, which has been confirmed in the non-interacting limit.

  6. Surface ozone-aerosol behaviour and atmospheric boundary layer structure in Saharan dusty scenario

    Science.gov (United States)

    Adame, Jose; Córdoba-Jabonero, Carmen; Sorrribas, Mar; Gil-Ojeda, Manuel; Toledo, Daniel; Yela, Margarita

    2016-04-01

    A research campaign was performed for the AMISOC (Atmospheric Minor Species relevant to the Ozone Chemistry) project at El Arenosillo observatory (southwest Spain) in May-June 2012. The campaign focused on the impact of Saharan dust intrusions at the Atmospheric Boundary Layer (ABL) and ozone-aerosol interactions. In-situ and remote-sensing techniques for gases and aerosols were used moreover to modelling analyses. Meteorology features, ABL structures and evolution, aerosol profiling distributions and aerosol-ozone interactions on the surface were analysed. Two four-day periods were selected according to non-dusty (clean conditions) and dusty (Saharan dust) situations. In both scenarios, sea-land breezes developed in the lower atmosphere, but differences were found in the upper levels. Results show that surface temperatures were greater than 3°C and humidity values were lower during dusty conditions than non-dusty conditions. Thermal structures on the surface layer (estimated using an instrument on a 100 m tower) show differences, mainly during nocturnal periods with less intense inversions under dusty conditions. The mixing layer during dusty days was 400-800 m thick, less than observed on non-dusty days. Dust also disturbed the typical daily ABL evolution. Stable conditions were observed during the early evening during intrusions. Aerosol extinction on dusty days was 2-3 times higher, and the dust was confined between 1500 and 5500 m. Back trajectory analyses confirmed that the dust had an African origin. On the surface, the particle concentration was approximately 3.5 times higher during dusty events, but the local ozone did not exhibit any change. The arrival of Saharan dust in the upper levels impacted the meteorological surface, inhibited the daily evolution of the ABL and caused an increase in aerosol loading on the surface and at higher altitudes; however, no dust influence was observed on surface ozone.

  7. The international surface temperature initiative's global land surface databank

    Science.gov (United States)

    Lawrimore, J. H.; Rennie, J.; Gambi de Almeida, W.; Christy, J.; Flannery, M.; Gleason, B.; Klein-Tank, A.; Mhanda, A.; Ishihara, K.; Lister, D.; Menne, M. J.; Razuvaev, V.; Renom, M.; Rusticucci, M.; Tandy, J.; Thorne, P. W.; Worley, S.

    2013-09-01

    The International Surface Temperature Initiative (ISTI) consists of an end-to-end process for land surface air temperature analyses. The foundation is the establishment of a global land surface Databank. This builds upon the groundbreaking efforts of scientists in the 1980s and 1990s. While using many of their principles, a primary aim is to improve aspects including data provenance, version control, openness and transparency, temporal and spatial coverage, and improved methods for merging disparate sources. The initial focus is on daily and monthly timescales. A Databank Working Group is focused on establishing Stage-0 (original observation forms) through Stage-3 data (merged dataset without quality control). More than 35 sources of data have already been added and efforts have now turned to development of the initial version of the merged dataset. Methods have been established for ensuring to the extent possible the provenance of all data from the point of observation through all intermediate steps to final archive and access. Databank submission procedures were designed to make the process of contributing data as easy as possible. All data are provided openly and without charge. We encourage the use of these data and feedback from interested users.

  8. Surface integrals approach to solution of some free boundary problems

    Directory of Open Access Journals (Sweden)

    Igor Malyshev

    1988-01-01

    Full Text Available Inverse problems in which it is required to determine the coefficients of an equation belong to the important class of ill-posed problems. Among these, of increasing significance, are problems with free boundaries. They can be found in a wide range of disciplines including medicine, materials engineering, control theory, etc. We apply the integral equations techniques, typical for parabolic inverse problems, to the solution of a generalized Stefan problem. The regularization of the corresponding system of nonlinear integral Volterra equations, as well as local existence, uniqueness, continuation of its solution, and several numerical experiments are discussed.

  9. Low Temperature Surface Carburization of Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Sunniva R; Heuer, Arthur H; Sikka, Vinod K

    2007-12-07

    Low-temperature colossal supersaturation (LTCSS) is a novel surface hardening method for carburization of austenitic stainless steels (SS) without the precipitation of carbides. The formation of carbides is kinetically suppressed, enabling extremely high or colossal carbon supersaturation. As a result, surface carbon concentrations in excess of 12 at. % are routinely achieved. This treatment increases the surface hardness by a factor of four to five, improving resistance to wear, corrosion, and fatigue, with significant retained ductility. LTCSS is a diffusional surface hardening process that provides a uniform and conformal hardened gradient surface with no risk of delamination or peeling. The treatment retains the austenitic phase and is completely non-magnetic. In addition, because parts are treated at low temperature, they do not distort or change dimensions. During this treatment, carbon diffusion proceeds into the metal at temperatures that constrain substitutional diffusion or mobility between the metal alloy elements. Though immobilized and unable to assemble to form carbides, chromium and similar alloying elements nonetheless draw enormous amounts of carbon into their interstitial spaces. The carbon in the interstitial spaces of the alloy crystals makes the surface harder than ever achieved before by more conventional heat treating or diffusion process. The carbon solid solution manifests a Vickers hardness often exceeding 1000 HV (equivalent to 70 HRC). This project objective was to extend the LTCSS treatment to other austenitic alloys, and to quantify improvements in fatigue, corrosion, and wear resistance. Highlights from the research include the following: • Extension of the applicability of the LTCSS process to a broad range of austenitic and duplex grades of steels • Demonstration of LTCSS ability for a variety of different component shapes and sizes • Detailed microstructural characterization of LTCSS-treated samples of 316L and other alloys

  10. The surface temperature of free evaporating drops

    Science.gov (United States)

    Borodulin, V. Y.; Letushko, V. N.; Nizovtsev, M. I.; Sterlyagov, A. N.

    2016-10-01

    Complex experimental and theoretical investigation of heat and mass transfer processes was performed at evaporation of free liquid drops. For theoretical calculation the emission-diffusion model was proposed. This allowed taking into account the characteristics of evaporation of small droplets, for which heat and mass transfer processes are not described in the conventional diffusion model. The calculation results of evaporation of droplets of different sizes were compared using two models: the conventional diffusion and emission-diffusion models. To verify the proposed physical model, the evaporation of droplets suspended on a polypropylene fiber was experimentally investigated. The form of droplets in the evaporation process was determined using microphotographing. The temperature was measured on the surfaces of evaporating drops using infrared thermography. The experimental results have showed good agreement with the numerical data for the time of evaporation and the temperature of evaporating drops.

  11. Low temperature surface conductivity of hydrogenated diamond

    Energy Technology Data Exchange (ETDEWEB)

    Sauerer, C.; Ertl, F.; Nebel, C.E.; Stutzmann, M. [Technische Univ. Muenchen, Garching (Germany). Walter-Schottky-Inst. fuer Physikalische Grundlagen der Halbleiterelektronik; Bergonzo, P. [LIST(CEA-Recherche Technology)/DIMIR/SIAR/Saclay, Gif-sur-Yvette (France); Williams, O.A.; Jackman, R.A. [University Coll., London (United Kingdom). Dept. of Electrical and Electronic Engineering

    2001-07-23

    Conductivity and Hall experiments are performed on hydrogenated poly-CVD, atomically flat homoepitaxially grown Ib and natural type IIa diamond layers in the regime 0.34 to 400 K. For all experiments hole transport is detected with sheet resistivities at room temperature in the range 10{sup 4} to 10{sup 5} {omega}/{radical}. We introduce a transport model where a disorder induced tail of localized states traps holes at very low temperatures (T < 70 K). The characteristic energy of the tail is in the range of 6 meV. Towards higher temperatures (T > 70 K) the hole density is approximately constant and the hole mobility {mu} is increasing two orders of magnitude. In the regime 70 K < T < 200 K, {mu} is exponentially activated with 22 meV, above it follows a {proportional_to}T{sup 3/2} law. The activation energy of the hole density at T < 70 K is governed by the energy gap between holes trapped in the tail and the mobility edge which they can propagate. In the temperature regime T < 25 K an increasing hole mobility is detected which is attributed to transport in delocalized states at the surface. (orig.)

  12. Surface boundary conditions for the numerical solution of the Euler equations

    Science.gov (United States)

    Dadone, A.; Grossman, B.

    1993-01-01

    We consider the implementation of boundary conditions at solid walls in inviscid Euler solutions by upwind, finite-volume methods. We review some current methods for the implementation of surface boundary conditions and examine their behavior for the problem of an oblique shock reflecting off a planar surface. We show the importance of characteristic boundary conditions for this problem and introduce a method of applying the classical flux-difference splitting of Roe as a characteristic boundary condition. Consideration of the equivalent problem of the intersection of two (equal and opposite) oblique shocks was very illuminating on the role of surface boundary conditions for an inviscid flow and led to the introduction of two new boundary-condition procedures, denoted as the symmetry technique and the curvature-corrected symmetry technique. Examples of the effects of the various surface boundary conditions considered are presented for the supersonic blunt body problem and the subcritical compressible flow over a circular cylinder. Dramatic advantages of the curvature-corrected symmetry technique over the other methods are shown, with regard to numerical entropy generation, total pressure loss, drag and grid convergence.

  13. On the Nature of Boundary Conditions for Flows with Moving Free Surfaces

    Science.gov (United States)

    Renardy, Michael; Renardy, Yuriko

    1991-04-01

    We consider small perturbations of plane parallel flow between a wall and a moving free surface. The problem is posed on a rectangle with inflow and outflow boundaries. The usual boundary conditions are posed at the wall and the free surface, and the fluid satisfies the Navier-Stokes equations. We examine the nature of boundary conditions which can be imposed at the inflow and outflow boundaries in order to yield a well-posed problem. This question turns out to be more delicate than is generally appreciated. Depending on the precise situation and on the regularity required of the solution, boundary conditions at just one or both endpoints of the free surface need to be imposed. For example, we show that if the velocities at te inflow and outflow boundaries are prescribed, then the position of the free surface at the inflow boundary can be prescribed, but not at the outflow if an H1-solution is desired. Numerical simulations with the FIDAP package are used to illustrate our analytical results.

  14. 3D automatic segmentation method for retinal optical coherence tomography volume data using boundary surface enhancement

    Directory of Open Access Journals (Sweden)

    Yankui Sun

    2016-03-01

    Full Text Available With the introduction of spectral-domain optical coherence tomography (SD-OCT, much larger image datasets are routinely acquired compared to what was possible using the previous generation of time-domain OCT. Thus, there is a critical need for the development of three-dimensional (3D segmentation methods for processing these data. We present here a novel 3D automatic segmentation method for retinal OCT volume data. Briefly, to segment a boundary surface, two OCT volume datasets are obtained by using a 3D smoothing filter and a 3D differential filter. Their linear combination is then calculated to generate new volume data with an enhanced boundary surface, where pixel intensity, boundary position information, and intensity changes on both sides of the boundary surface are used simultaneously. Next, preliminary discrete boundary points are detected from the A-Scans of the volume data. Finally, surface smoothness constraints and a dynamic threshold are applied to obtain a smoothed boundary surface by correcting a small number of error points. Our method can extract retinal layer boundary surfaces sequentially with a decreasing search region of volume data. We performed automatic segmentation on eight human OCT volume datasets acquired from a commercial Spectralis OCT system, where each volume of datasets contains 97 OCT B-Scan images with a resolution of 496×512 (each B-Scan comprising 512 A-Scans containing 496 pixels; experimental results show that this method can accurately segment seven layer boundary surfaces in normal as well as some abnormal eyes.

  15. Damage Susceptibility of Grain Boundaries in HT9 Steel Subjected to High-Temperature Creep

    Science.gov (United States)

    Leng, Zhe; Field, David P.

    2012-10-01

    HT9 steel is an attractive ferritic/martensitic steel that is used in components of nuclear and fossil power plants because of its high strength and good swelling resistance. Specific phenomena (such as segregation, voiding, cracking, etc.) are prevalent along grain boundaries since these interfaces act as efficient sources for vacancies. The accumulation of vacancies in grain boundaries may result in intergranular fracture. In this study, HT9 steel was subjected to creep tests at elevated temperature (about 0.5 T m) and two different creep conditions (where creep lifetimes were about 100 and about 1000 hours, respectively). The grain boundaries in HT9 steel after creep tests were studied by the use of scanning electron microscopy in order to establish the relationship between the grain boundary structure and creep damage. Images and data obtained using electron backscatter diffraction reveal a high susceptibility of high-angle boundaries to creep cavitation, as expected. In addition, the Σ3 boundaries are also susceptible to damage under these conditions at a similar or even higher rate as compared with random high-angle boundaries.

  16. Thermodynamic Equilibrium Studies of Nanocrystallite CeO2 Grain Boundaries by High Temperature X-Ray Photoelectron Spectroscopy and Thermal Gravimetric Analysis

    Institute of Scientific and Technical Information of China (English)

    LIU Zhen-Xiang; XIE Kan

    2000-01-01

    Nanostructured CeO2 thin films and powders are studied by high temperature x-ray photoelectron spectroscopy and thermal gravimetric analysis. The results indicate that the surface composition strongly depends on temperature, the surface O/Ce ratio initially increases with increasing temperature, then decreases with the further increase of temperature, the maximum surface O/Ce ratio is at about 300℃ C. The variation of the surface composition with temperature arises from the ion migration, redistribution and transformation between lattice oxygen and gas phase oxygen near the grain boundaries during the thermodynamic equilibrium process. The results also show that CeO2 has a weakly bond oxygen, high oxygen mobility in the bulk and a high molecular dissociation rate at the surface, especially for the sol-gel prepared nanocrystallite CeO2.

  17. On the coupling between a supersonic boundary layer and a flexible surface

    Science.gov (United States)

    Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

    1992-01-01

    The coupling between a two-dimensional, supersonic, laminar boundary layer and a flexible surface is studied using direct numerical computations of the Navier-Stokes equations coupled with the plate equation. The flexible surface is forced to vibrate by plane acoustic waves at normal incidence emanated by a sound source located on the side of the flexible surface opposite to the boundary layer. The effect of the source excitation frequency on the surface vibration and boundary layer stability is analyzed. We find that, for frequencies near the fifth natural frequency of the surface or lower, large disturbances are introduced in the boundary layer which may alter its stability characteristics. The interaction between a stable two-dimensional disturbance of Tollmien-Schlichting (TS) type with the vibrating surface is also studied. We find that the disturbance level is higher over the vibrating flexible surface than that obtained when the surface is rigid, which indicates a strong coupling between flow and structure. However, in the absence of the sound source the disturbance level over the rigid and flexible surfaces are identical. This result is due to the high frequency of the TS disturbance which does not couple with the flexible surface.

  18. Analysis of the Slab Temperature, Thermal Stresses and Fractures Computed with the Implementation of Local and Average Boundary Conditions in the Secondary Cooling Zones

    Directory of Open Access Journals (Sweden)

    Hadała B.

    2016-12-01

    Full Text Available The numerical simulations of the temperature fields have been accomplished for slab casting made of a low carbon steel. The casting process of slab of 1500 mm in width and 225 mm in height has been modeled. Two types of boundary condition models of heat transfer have been employed in numerical simulations. The heat transfer coefficient in the first boundary condition model was calculated from the formula which takes into account the slab surface temperature and water flow rate in each secondary cooling zone. The second boundary condition model defines the heat transfer coefficient around each water spray nozzle. The temperature fields resulting from the average in zones water flow rate and from the nozzles arrangement have been compared. The thermal stresses and deformations resulted from such temperature field have given higher values of fracture criterion at slab corners.

  19. Temperature Histories of Structural Steel Welds Calculated Using Solidification-Boundary Constraints

    Science.gov (United States)

    Lambrakos, S. G.

    2016-09-01

    Temperature histories of structural steel deep-penetration welds are presented, which are calculated using numerical-analytical basis functions and solidification-boundary constraints. These weld temperature histories can be adopted as input data to various types of computational procedures, which include numerical models for prediction of solid-state phase transformations and mechanical response. In addition, these temperature histories can be used parametrically for inverse thermal analysis of welds corresponding to other welding processes whose process conditions are within similar regimes. The present study applies an inverse thermal analysis procedure that uses three-dimensional constraint conditions whose two-dimensional projections are mapped within transverse cross sections of experimentally measured solidification boundaries. In addition, the present study uses experimentally measured estimates of the heat effect zone edge to examine the consistency of calculated temperature histories for steel welds.

  20. Near Continuum Velocity and Temperature Coupled Compressible Boundary Layer Flow over a Flat Plate

    Science.gov (United States)

    He, Xin; Cai, Chunpei

    2017-04-01

    The problem of a compressible gas flows over a flat plate with the velocity-slip and temperature-jump boundary conditions are being studied. The standard single- shooting method is applied to obtain the exact solutions for velocity and temperature profiles when the momentum and energy equations are weakly coupled. A double-shooting method is applied if these two equations are closely coupled. If the temperature affects the velocity directly, more significant velocity slip happens at locations closer to the plate's leading edge, and inflections on the velocity profiles appear, indicating flows may become unstable. As a consequence, the temperature-jump and velocity-slip boundary conditions may trigger earlier flow transitions from a laminar to a turbulent flow state.

  1. Improved low frequency room responses by considering finiteness of room boundary surfaces

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2013-01-01

    For room acoustic simulations, the acoustic characteristics of room boundary surfaces are typically calculated under the assumption that the surfaces are sufficiently large. In this study, a reflection coefficient for finite surfaces is suggested and its performance is assessed through case studies...... surface impedance values that are assigned to all the boundary surfaces, the suggested reflection coefficient is found to improve low frequency responses compared to the infinite panel theory; larger improvements are found for a more disproportionate room, more absorptive surfaces, and surfaces having...... larger negative phase angles of the surface impedance. A larger improvement is also found for a nonuniform absorption case than for a uniform absorption setting having a similar equivalent absorption coefficient....

  2. Accurate computation of surface stresses and forces with immersed boundary methods

    CERN Document Server

    Goza, Andres; Morley, Benjamin; Colonius, Tim

    2016-01-01

    Many immersed boundary methods solve for surface stresses that impose the velocity boundary conditions on an immersed body. These surface stresses may contain spurious oscillations that make them ill-suited for representing the physical surface stresses on the body. Moreover, these inaccurate stresses often lead to unphysical oscillations in the history of integrated surface forces such as the coefficient of lift. While the errors in the surface stresses and forces do not necessarily affect the convergence of the velocity field, it is desirable, especially in fluid-structure interaction problems, to obtain smooth and convergent stress distributions on the surface. To this end, we show that the equation for the surface stresses is an integral equation of the first kind whose ill-posedness is the source of spurious oscillations in the stresses. We also demonstrate that for sufficiently smooth delta functions, the oscillations may be filtered out to obtain physically accurate surface stresses. The filtering is a...

  3. The study of surface wetting, nanobubbles and boundary slip with an applied voltage: A review

    Directory of Open Access Journals (Sweden)

    Yunlu Pan

    2014-07-01

    Full Text Available The drag of fluid flow at the solid–liquid interface in the micro/nanoscale is an important issue in micro/nanofluidic systems. Drag depends on the surface wetting, nanobubbles, surface charge and boundary slip. Some researchers have focused on the relationship between these interface properties. In this review, the influence of an applied voltage on the surface wettability, nanobubbles, surface charge density and slip length are discussed. The contact angle (CA and contact angle hysteresis (CAH of a droplet of deionized (DI water on a hydrophobic polystyrene (PS surface were measured with applied direct current (DC and alternating current (AC voltages. The nanobubbles in DI water and three kinds of saline solution on a PS surface were imaged when a voltage was applied. The influence of the surface charge density on the nanobubbles was analyzed. Then the slip length and the electrostatic force on the probe were measured on an octadecyltrichlorosilane (OTS surface with applied voltage. The influence of the surface charge on the boundary slip and drag of fluid flow has been discussed. Finally, the influence of the applied voltage on the surface wetting, nanobubbles, surface charge, boundary slip and the drag of liquid flow are summarized. With a smaller surface charge density which could be achieved by applying a voltage on the surface, larger and fewer nanobubbles, a larger slip length and a smaller drag of liquid flow could be found.

  4. An inconvenient "truth" about using sensible heat flux as a surface boundary condition in models under stably stratified regimes

    NARCIS (Netherlands)

    Basu, S.; Holtslag, A.A.M.; Wiel, van de B.J.H.; Moene, A.F.; Steeneveld, G.J.

    2008-01-01

    In single column and large-eddy simulation studies of the atmospheric boundary layer, surface sensible heat flux is often used as a boundary condition. In this paper, we delineate the fundamental shortcomings of such a boundary condition in the context of stable boundary layer modelling and simulati

  5. Magnetohydrodynamic Stagnation Point Flow with a Convective Surface Boundary Condition

    Science.gov (United States)

    Jafar, Khamisah; Ishak, Anuar; Nazar, Roslinda

    2011-09-01

    This study analyzes the steady laminar two-dimensional stagnation point flow and heat transfer of an incompressible viscous fluid impinging normal to a horizontal plate, with the bottom surface of the plate heated by convection from a hot fluid. A uniform magnetic field is applied in a direction normal to the flat plate, with a free stream velocity varying linearly with the distance from the stagnation point. The governing partial differential equations are first transformed into ordinary differential equations, before being solved numerically. The analysis includes the effects of the magnetic parameter, the Prandtl number, and the convective parameter on the heat transfer rate at the surface. Results showed that the heat transfer rate at the surface increases with increasing values of these quantities.

  6. Magnetohydrodynamic stagnation point flow with a convective surface boundary condition

    Energy Technology Data Exchange (ETDEWEB)

    Jafar, Khamisah [Universiti Kebangsaan Malaysia, Bangi, Selangor (Malaysia). Faculty of Engineering and Built Environment; Ishak, Anuar; Nazar, Roslinda [Universiti Kebangsaan, Bangi, Selangor (Malaysia). School of Mathematical Sciences

    2011-08-15

    This study analyzes the steady laminar two-dimensional stagnation point flow and heat transfer of an incompressible viscous fluid impinging normal to a horizontal plate, with the bottom surface of the plate heated by convection from a hot fluid. A uniform magnetic field is applied in a direction normal to the flat plate, with a free stream velocity varying linearly with the distance from the stagnation point. The governing partial differential equations are first transformed into ordinary differential equations, before being solved numerically. The analysis includes the effects of the magnetic parameter, the Prandtl number, and the convective parameter on the heat transfer rate at the surface. Results showed that the heat transfer rate at the surface increases with increasing values of these quantities. (orig.)

  7. Dynamic forces between bubbles and surfaces and hydrodynamic boundary conditions.

    Science.gov (United States)

    Manor, Ofer; Vakarelski, Ivan U; Stevens, Geoffrey W; Grieser, Franz; Dagastine, Raymond R; Chan, Derek Y C

    2008-10-21

    A bubble attached to the end of an atomic force microscope cantilever and driven toward or away from a flat mica surface across an aqueous film is used to characterize the dynamic force that arises from hydrodynamic drainage and electrical double layer interactions across the nanometer thick intervening aqueous film. The hydrodynamic response of the air/water interface can range from a classical fully immobile, no-slip surface in the presence of added surfactants to a partially mobile interface in an electrolyte solution without added surfactants. A model that includes the convection and diffusion of trace surface contaminants can account for the observed behavior presented. This model predicts quantitatively different interfacial dynamics to the Navier slip model that can also be used to fit dynamic force data with a post hoc choice of a slip length.

  8. Extended Reconstructed Sea Surface Temperature (ERSST), Version 4

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Extended Reconstructed Sea Surface Temperature (ERSST) dataset is a global monthly sea surface temperature analysis on a 2x2 degree grid derived from the...

  9. NOAA Global Surface Temperature Dataset, Version 4.0

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Global Surface Temperature Dataset (NOAAGlobalTemp) is derived from two independent analyses: the Extended Reconstructed Sea Surface Temperature (ERSST)...

  10. HTPro: Low-temperature Surface Hardening of Stainless Steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Somers, Marcel A. J.

    2013-01-01

    Low-temperature surface hardening of stainless steel provides the required performance properties without affecting corrosion resistance.......Low-temperature surface hardening of stainless steel provides the required performance properties without affecting corrosion resistance....

  11. Merged Land and Ocean Surface Temperature, Version 3.5

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The historical Merged Land-Ocean Surface Temperature Analysis (MLOST) is derived from two independent analyses, an Extended Reconstructed Sea Surface Temperature...

  12. An algorithm for estimating surface normal from its boundary curves

    Directory of Open Access Journals (Sweden)

    Jisoon Park

    2015-01-01

    Full Text Available Recently, along with the improvements of geometry modeling methods using sketch-based interface, there have been a lot of developments in research about generating surface model from 3D curves. However, surfacing a 3D curve network remains an ambiguous problem due to the lack of geometric information. In this paper, we propose a new algorithm for estimating the normal vectors of the 3D curves which accord closely with user intent. Bending energy is defined by utilizing RMF(Rotation-Minimizing Frame of 3D curve, and we estimated this minimal energy frame as the one that accords design intent. The proposed algorithm is demonstrated with surface model creation of various curve networks. The algorithm of estimating geometric information in 3D curves which is proposed in this paper can be utilized to extract new information in the sketch-based modeling process. Also, a new framework of 3D modeling can be expected through the fusion between curve network and surface creating algorithm.

  13. Influence of diamond surface termination on thermal boundary conductance between Al and diamond

    Energy Technology Data Exchange (ETDEWEB)

    Monachon, Christian; Weber, Ludger [Laboratoire de Metallurgie Mecanique, Ecole Polytechnique Federale de Lausanne, Lausanne (Switzerland)

    2013-05-14

    The effect of diamond surface treatment on the Thermal Boundary Conductance (TBC) between Al and diamond is investigated. The treatments consist in either of the following: exposition to a plasma of pure Ar, Ar:H and Ar:O, and HNO{sub 3}:H{sub 2}SO{sub 4} acid dip for various times. The surface of diamond after treatment is analyzed by X-ray Photoelectron Spectroscopy, revealing hydrogen termination for the as-received and Ar:H plasma treated samples, pure sp{sup 2} termination for Ar treated ones and oxygen (keton-like) termination for the other treatments. At ambient, all the specific treatments improve the TBC between Al and diamond from 23 {+-} 2 MW m{sup -2} K{sup -1} for the as-received to 65 {+-} 5, 125 {+-} 20, 150 {+-} 20, 180 {+-} 20 MW m{sup -2} K{sup -1} for the ones treated by Ar:H plasma, acid, pure Ar plasma, and Ar:O plasma with an evaporated Al layer on top, respectively. The effect of these treatments on temperature dependence are also observed and compared with the most common models available in the literature as well as experimental values in the same system. The results obtained show that the values measured for an Ar:O plasma treated diamond with Al sputtered on top stay consistently higher than the values existing in the literature over a temperature range from 78 to 290 K, probably due a lower sample surface roughness. Around ambient, the TBC values measured lay close to or even somewhat above the radiation limit, suggesting that inelastic or electronic processes may influence the transfer of heat at this metal/dielectric interface.

  14. Dry Deposition, Surface Production and Dynamics of Aerosols in the Marine Boundary Layer

    DEFF Research Database (Denmark)

    Fairall, C.W.; Larsen, Søren Ejling

    1984-01-01

    A model of downward aerosol panicle flux characterized by dry deposition velocity, Vd, due to Slinn and Slinn (1980) is generalized to the case of nonzero surface concentration (absorbing surface with a surface source). A more general expression for the flux at some reference height is developed...... which includes Vd and an effective surface source strength, Si, which is a function of the true surface source strength, Si, and the particle transport properties below the reference height. The general expression for the surface flux is incorporated into a dynamic mixed layer model of the type...... developed by Davidson et al. (1983). This three layer model (diffusion sublayer, turbulent surface layer and mixed layer) is applied to an open ocean marine regime where boundary layer advection is ignored. The aerosol concentration in the boundary layer is considered to consist of sea salt particles...

  15. Middle Pliocene sea surface temperature variability

    Science.gov (United States)

    Dowsett, H.J.; Chandler, M.A.; Cronin, T. M.; Dwyer, G.S.

    2005-01-01

    Estimates of sea surface temperature (SST) based upon foraminifer, diatom, and ostracod assemblages from ocean cores reveal a warm phase of the Pliocene between about 3.3 and 3.0 Ma. Pollen records and plant megafossils, although not as well dated, show evidence for a warmer climate at about the same time. Increased greenhouse forcing and altered ocean heat transport are the leading candidates for the underlying cause of Pliocene global warmth. Despite being a period of global warmth, this interval encompasses considerable variability. Two new SST reconstructions are presented that are designed to provide a climatological error bar for warm peak phases of the Pliocene and to document the spatial distribution and magnitude of SST variability within the mid-Pliocene warm period. These data suggest long-term stability of low-latitude SST and document greater variability in regions of maximum warming. Copyright 2005 by the American Geophysical Union.

  16. Land-surface and boundary layer processes in a semi-arid heterogeneous landscape

    NARCIS (Netherlands)

    Jochum, A.M.

    2003-01-01

    The European Field Experiment in a Desertification-threatened Area (EFEDA) provides a comprehensive land-surface dataset for a semiarid Mediterranean environment. It is used here to study heat and moisture transport processes in the atmospheric boundary layer (ABL), to derive grid-scale surface flux

  17. Impact of Atlantic sea surface temperatures on the warmest global surface air temperature of 1998

    Science.gov (United States)

    Lu, Riyu

    2005-03-01

    The year 1998 is the warmest year in the record of instrumental measurements. In this study, an atmospheric general circulation model is used to investigate the role of sea surface temperatures (SSTs) in this warmth, with a focus on the role of the Atlantic Ocean. The model forced with the observed global SSTs captures the main features of land surface air temperature anomalies in 1998. A sensitivity experiment shows that in comparison with the global SST anomalies, the Atlantic SST anomalies can explain 35% of the global mean surface air temperature (GMAT) anomaly, and 57% of the land surface air temperature anomaly in 1998. The mechanisms through which the Atlantic Ocean influences the GMAT are likely different from season to season. Possible detailed mechanisms involve the impact of SST anomalies on local convection in the tropical Atlantic region, the consequent excitation of a Rossby wave response that propagates into the North Atlantic and the Eurasian continent in winter and spring, and the consequent changes in tropical Walker circulation in summer and autumn that induce changes in convection over the tropical Pacific. This in turn affects climate in Asia and Australia. The important role of the Atlantic Ocean suggests that attention should be paid not only to the tropical Pacific Ocean, but also to the tropical Atlantic Ocean in understanding the GMAT variability and its predictability.

  18. Unsteady boundary layer nanofluid flow and heat transfer along a porous stretching surface with magnetic field

    Science.gov (United States)

    Alam, M. S.; Ali, M.; Alim, M. A.; Munshi, M. J. Haque

    2017-06-01

    The present study is performed to find the similarity solution like Blasius solution and also analyzed the effect of various dimensionless parameters on the momentum, thermal and nanoparticle concentration. In this respect we have considered the magnetohydrodynamic (MHD) unsteady boundary layer nanofluid flow and heat - mass transfer along a porous stretching surface. So the governing partial differential equations are transformed to ordinary differential equations by using similarity transformations. The numerical solution is taken by applying the Nachtsgeim-Swigert shooting iteration technique along with Runge-Kutta integration scheme. The effects of various dimensionless parameters on velocity, temperature and nanoparticle concentration are discussed numerically and shown graphically. Therefore, from the figures it is observed that the results of velocity profile increases for increasing values of unsteadiness parameter, permeability parameter and stretching ratio parameter but there is no effect for magnetic parameter, the temperature profile decreases for increasing values of Brownian motion, unsteadiness, thermophoresis and stretching ratio but increases for magnetic parameter, the nanoparticle concentration decreases for increasing values of unsteadiness parameter, thermophoresis parameter, suction parameter, stretching ratio parameter and Lewis number but increases for magnetic parameter and Brownian motion parameter. For validity and accuracy the present results are compared with previously published work and found to in good agreement.

  19. Low Temperature Surface Carburization of Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Sunniva R; Heuer, Arthur H; Sikka, Vinod K

    2007-12-07

    Low-temperature colossal supersaturation (LTCSS) is a novel surface hardening method for carburization of austenitic stainless steels (SS) without the precipitation of carbides. The formation of carbides is kinetically suppressed, enabling extremely high or colossal carbon supersaturation. As a result, surface carbon concentrations in excess of 12 at. % are routinely achieved. This treatment increases the surface hardness by a factor of four to five, improving resistance to wear, corrosion, and fatigue, with significant retained ductility. LTCSS is a diffusional surface hardening process that provides a uniform and conformal hardened gradient surface with no risk of delamination or peeling. The treatment retains the austenitic phase and is completely non-magnetic. In addition, because parts are treated at low temperature, they do not distort or change dimensions. During this treatment, carbon diffusion proceeds into the metal at temperatures that constrain substitutional diffusion or mobility between the metal alloy elements. Though immobilized and unable to assemble to form carbides, chromium and similar alloying elements nonetheless draw enormous amounts of carbon into their interstitial spaces. The carbon in the interstitial spaces of the alloy crystals makes the surface harder than ever achieved before by more conventional heat treating or diffusion process. The carbon solid solution manifests a Vickers hardness often exceeding 1000 HV (equivalent to 70 HRC). This project objective was to extend the LTCSS treatment to other austenitic alloys, and to quantify improvements in fatigue, corrosion, and wear resistance. Highlights from the research include the following: • Extension of the applicability of the LTCSS process to a broad range of austenitic and duplex grades of steels • Demonstration of LTCSS ability for a variety of different component shapes and sizes • Detailed microstructural characterization of LTCSS-treated samples of 316L and other alloys

  20. Realization of Holographic Entaglement Temperature for a Nearly-AdS boundary

    CERN Document Server

    Momeni, D; Gholizade, H; Myrzakulov, R

    2015-01-01

    Computation from the holographic entanglement entropy proposal of Ryu-Takayanagi shows that thermal near boundary region in $AdS_3$ has a maximum of the temperature. The absolute maxima of temperature is $T^{Max}_{E}= \\frac{4G_3 \\epsilon_{\\infty}}{l}$. By simple physical investigations it has become possible to predict a phase transition of first order at critical temperature $T_c\\leq T_{E}$ . It is pertinent to mention here that our structure is comprising the properties of metamaterials-an artificial material build with the composition of real materials, whose properties are triggered on the desired basis. The Phase transitions of this form have received a striking experimental verification in so far as they predict a tail or root towards which the AdS space ultimately tend when the boundary is considered thermalized.

  1. Remote sensing of Arctic boundary layer clouds above snow surfaces

    Science.gov (United States)

    Ehrlich, André; Bierwirth, Eike; Wendisch, Manfred

    2015-04-01

    In the Arctic remote sensing of clouds using reflected solar radiation is mostly related to high uncertainties as the contrast between the bright sea ice and snow surface and the clouds is low. Additionally, uncertainties result from variation of the snow grain size which changes the absorption of solar radiation similarly to the size of cloud particles. This is a major issue for understanding the response of Arctic clouds to climate warming as the quantification of cloud properties in this remote region mostly relies on satellite observations. We used spectral radiation measurements of the Spectral Modular Airborne Radiation measurement sysTem (SMART-Albedometer) to improve common used cloud remote sensing algorithms in case of snow surfaces. The measurements were collected during the airborne research campaign Vertical distribution of ice in Arctic mixed-phase clouds (VERDI, April/May 2012) above the Canadian Beaufort where both sea ice covered and ice free ocean areas were present during the observation period. Based on the spectral absorption characteristics of snow and clouds (assuming to be dominated by the liquid fraction) a combination of wavelengths was found which allows to separate the impact of clouds and snow surface on the reflected radiation measured above the clouds. While snow grain size dominates the absorption at a wavelength of 1.0 μm, information on cloud optical thickness and cloud particle effective radius can be extracted at wavelengths of 1.7 μm and 2.1 μm, respectively. Based on radiative transfer simulations lookup tables for the retrieval algorithm were calculated and used to estimate the theoretical uncertainties of the retrieval. It was found that using ratios instead of absolute radiances reduces the uncertainties significantly. The new algorithm was applied to a specific case observed during the VERDI campaign where a stratocumulus clouds was located above an ice edge. It could be shown that the method works also over water

  2. Turbulent Flow past High Temperature Surfaces

    Science.gov (United States)

    Mehmedagic, Igbal; Thangam, Siva; Carlucci, Pasquale; Buckley, Liam; Carlucci, Donald

    2014-11-01

    Flow over high-temperature surfaces subject to wall heating is analyzed with applications to projectile design. In this study, computations are performed using an anisotropic Reynolds-stress model to study flow past surfaces that are subject to radiative flux. The model utilizes a phenomenological treatment of the energy spectrum and diffusivities of momentum and heat to include the effects of wall heat transfer and radiative exchange. The radiative transport is modeled using Eddington approximation including the weighted effect of nongrayness of the fluid. The time-averaged equations of motion and energy are solved using the modeled form of transport equations for the turbulence kinetic energy and the scalar form of turbulence dissipation with an efficient finite-volume algorithm. The model is applied for available test cases to validate its predictive capabilities for capturing the effects of wall heat transfer. Computational results are compared with experimental data available in the literature. Applications involving the design of projectiles are summarized. Funded in part by U.S. Army, ARDEC.

  3. Flux measurements in the surface Marine Atmospheric Boundary Layer over the Aegean Sea, Greece.

    Science.gov (United States)

    Kostopoulos, V E; Helmis, C G

    2014-10-01

    Micro-meteorological measurements within the surface Marine Atmospheric Boundary Layer took place at the shoreline of two islands at northern and south-eastern Aegean Sea of Greece. The primary goal of these experimental campaigns was to study the momentum, heat and humidity fluxes over this part of the north-eastern Mediterranean Sea, characterized by limited spatial and temporal scales which could affect these exchanges at the air-sea interface. The great majority of the obtained records from both sites gave higher values up to factor of two, compared with the estimations from the most widely used parametric formulas that came mostly from measurements over open seas and oceans. Friction velocity values from both campaigns varied within the same range and presented strong correlation with the wind speed at 10 m height while the calculated drag coefficient values at the same height for both sites were found to be constant in relation with the wind speed. Using eddy correlation analysis, the heat flux values were calculated (virtual heat fluxes varied from -60 to 40 W/m(2)) and it was found that they are affected by the limited spatial and temporal scales of the responding air-sea interaction mechanism. Similarly, the humidity fluxes appeared to be strongly influenced by the observed intense spatial heterogeneity of the sea surface temperature.

  4. Use of satellite land surface temperatures in the EUSTACE global surface air temperature analysis

    Science.gov (United States)

    Ghent, D.; Good, E.; Rayner, N. A.

    2015-12-01

    EUSTACE (EU Surface Temperatures for All Corners of Earth) is a Horizon2020 project that will produce a spatially complete, near-surface air temperature (NSAT) analysis for the globe for every day since 1850. The analysis will be based on both satellite and in situ surface temperature observations over land, sea, ice and lakes, which will be combined using state-of-the-art statistical methods. The use of satellite data will enable the EUSTACE analysis to offer improved estimates of NSAT in regions that are poorly observed in situ, compared with existing in-situ based analyses. This presentation illustrates how satellite land surface temperature (LST) data - sourced from the European Space Agency (ESA) Data User Element (DUE) GlobTemperature project - will be used in EUSTACE. Satellite LSTs represent the temperature of the Earth's skin, which can differ from the corresponding NSAT by several degrees or more, particularly during the hottest part of the day. Therefore the first challenge is to develop an approach to estimate global NSAT from satellite observations. Two methods will be trialled in EUSTACE, both of which are summarised here: an established empirical regression-based approach for predicting NSAT from satellite data, and a new method whereby NSAT is calculated from LST and other parameters using a physics-based model. The second challenge is in estimating the uncertainties for the satellite NSAT estimates, which will determine how these data are used in the final blended satellite-in situ analysis. This is also important as a key component of EUSTACE is in delivering accurate uncertainty information to users. An overview of the methods to estimate the satellite NSATs is also included in this presentation.

  5. Applications of surface analysis techniques to photovoltaic research: Grain and grain boundary studies

    Science.gov (United States)

    Kazmerski, L. L.

    Complementary surface analysis techniques (AES, SIMS, XPS) are applied to photovoltaic devices in order to assess the limiting factors of grain and grain boundary chemistry to the performance of polycrystalline solar cells. Results of these compositional and chemical studies are directly correlated with electrical measurements (EBIC) and with resulting device performance. Examples of grain boundary passivation in polycrystalline Si and GaAs solar cells are cited. The quality of the intragrain material used in these devices is shown to be equally important to the grain boundary activity in determining overall photovoltaic performance.

  6. Radiation, Heat Generation and Viscous Dissipation Effects on MHD Boundary Layer Flow for the Blasius and Sakiadis Flows with a Convective Surface Boundary Condition

    Directory of Open Access Journals (Sweden)

    K. GANGADHAR

    2015-01-01

    Full Text Available This study is devoted to investigate the radiation, heat generation viscous dissipation and magnetohydrodynamic effects on the laminar boundary layer about a flat-plate in a uniform stream of fluid (Blasius flow, and about a moving plate in a quiescent ambient fluid (Sakiadis flow both under a convective surface boundary condition. Using a similarity variable, the governing nonlinear partial differential equations have been transformed into a set of coupled nonlinear ordinary differential equations, which are solved numerically by using shooting technique alongside with the forth order of Runge-Kutta method and the variations of dimensionless surface temperature and fluid-solid interface characteristics for different values of Magnetic field parameter M, Grashof number Gr, Prandtl number Pr, radiation parameter NR, Heat generation parameter Q, Convective parameter  and the Eckert number Ec, which characterizes our convection processes are graphed and tabulated. Quite different and interesting behaviors were encountered for Blasius flow compared with a Sakiadis flow. A comparison with previously published results on special cases of the problem shows excellent agreement.

  7. A neural network for enhancing boundaries and surfaces in synthetic aperture radar images.

    Science.gov (United States)

    Mingolla, Ennio; Ross, William; Grossberg, Stephen

    1999-04-01

    A neural network system for boundary segmentation and surface representation, inspired by a new local-circuit model of visual processing in the cerebral cortex, is used to enhance images of range data gathered by a synthetic aperture radar (SAR) sensor. Boundary segmentation is accomplished by an improved Boundary Contour System (BCS) model which completes coherent boundaries that retain their sensitivity to image contrasts and locations. A Feature Contour System (FCS) model compensates for local contrast variations and uses the compensated signals to diffusively fill-in surface regions within the BCS boundaries. Image noise pixels that are not supported by BCS boundaries are hereby eliminated. More generally, BCS/FCS processing normalizes input dynamic range, reduces noise, and enhances contrasts between surface regions. BCS/FCS processing hereby makes structures such as motor vehicles, roads, and buildings more salient to human observers than in original imagery. The new BCS model improves image enhancement with significant reductions in processing time and complexity over previous BCS applications. The new system also outperforms several established techniques for image enhancement.

  8. Long-Term High-Latitude Sea and Ice Surface Temperature Record from AVHRR GAC Data

    Science.gov (United States)

    Luis, C. S.; Dybkjær, G.; Eastwood, S.; Tonboe, R. T.; Høyer, J. L.

    2014-12-01

    Surface temperature is among the most important variables in the surface energy balance equation and it significantly affects the atmospheric boundary layer structure, the turbulent heat exchange and, over ice, the ice growth rate. Here we measure the surface temperature using thermal infrared sensors from 10-12 μm wavelength, a method whose primary limitation over sea ice is the detection of clouds. However, in the Arctic and around Antarctica there are very few conventional observations of surface temperature from buoys, and it is sometimes difficult to determine if the temperature is measured at the surface or within the snowpack, the latter of which often results in a warm bias. To reduce this bias, much interest is being paid to alternative remote sensing methods for monitoring high latitude surface temperature. We used Advanced Very High Resolution Radiometer (AVHRR) global area coverage (GAC) data to produce a high latitude sea surface temperature (SST), ice surface temperature (IST) and ice cap skin temperature dataset spanning 27 years (1982-2009). This long-term climate record is the first of its kind for IST. In this project we used brightness temperatures from the infrared channels of AVHRR sensors aboard NOAA and Metop polar-orbiting satellites. Surface temperatures were calculated using separate split window algorithms for day SST, night SST, and IST. The snow surface emissivity across all angles of the swath were simulated specifically for all sensors using an emission model. Additionally, all algorithms were tuned to the Arctic using simulated brightness temperatures from a radiative transfer model with atmospheric profiles and skin temperatures from European Centre for Medium-Range Forecasts (ECMWF) re-analysis data (ERA-Interim). Here we present the results of product quality as compared to in situ measurements from buoys and infrared radiometers, as well as a preliminary analysis of climate trends revealed by the record.

  9. The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere

    Directory of Open Access Journals (Sweden)

    J. Moen

    2004-06-01

    Full Text Available A continuous band of high ion temperature, which persisted for about 8h and zigzagged north-south across more than five degrees in latitude in the dayside (07:00-15:00MLT auroral ionosphere, was observed by the EISCAT VHF radar on 23 November 1999. Latitudinal gradients in the temperature of the F-region electron and ion gases (Te and Ti, respectively have been compared with concurrent observations of particle precipitation and field-perpendicular convection by DMSP satellites, in order to reveal a physical explanation for the persistent band of high Ti, and to test the potential role of Ti and Te gradients as possible markers for the open-closed field line boundary. The north/south movement of the equatorward Ti boundary was found to be consistent with the contraction/expansion of the polar cap due to an unbalanced dayside and nightside reconnection. Sporadic intensifications in Ti, recurring on ~10-min time scales, indicate that frictional heating was modulated by time-varying reconnection, and the band of high Ti was located on open flux. However, the equatorward Ti boundary was not found to be a close proxy of the open-closed boundary. The closest definable proxy of the open-closed boundary is the magnetosheath electron edge observed by DMSP. Although Te appears to be sensitive to magnetosheath electron fluxes, it is not found to be a suitable parameter for routine tracking of the open-closed boundary, as it involves case dependent analysis of the thermal balance. Finally, we have documented a region of newly-opened sunward convecting flux. This region is situated between the convection reversal boundary and the magnetosheath electron edge defining the open-closed boundary. This is consistent with a delay of several minutes between the arrival of the first (super-Alfvénic magnetosheath electrons and the response in the ionospheric

  10. Reduction of the temperature jump in the immersed boundary-thermal lattice Boltzmann method

    Science.gov (United States)

    Seta, Takeshi; Hayashi, Kosuke; Tomiyama, Akio

    2015-11-01

    We analytically and numerically investigate the boundary errors computed by the immersed boundary-thermal lattice Boltzmann method (IB-TLBM) with the two-relaxation-time (TRT) collision operator. In the linear collision operator of the TRT, we decompose the distribution function into symmetric and antisymmetric components and define the relaxation parameters for each part. We derive the theoretical relation between the relaxation parameters for the symmetric and antisymmetric parts of the distribution function so as to eliminate the temperature jump. The simple TRT collision operator succeeds in reducing the temperature jump occurring at the high relaxation time in the IB-TLBM calculation. The porous plate problem numerically and analytically demonstrate that the velocity squared terms should be neglected in the equilibrium distribution function in order to eliminate the effect of the advection velocity on the temperature jump in the IB-TLBMs. The passive scalar model without the velocity squared terms more accurately calculates the incompressible temperature equation in the IB-TLBMs, compared to the double distribution model, which is based on the relation of the distribution function gk = (ek - u)2fk / 2 . We apply the passive scalar model without the velocity squared terms to the simulation of the natural convection between a hot circular cylinder and a cold square enclosure. The proposed method adequately sets the boundary values and provides reasonable average Nusselt numbers and maximum absolute values of the stream function.

  11. Simulation of a free-surface and seepage face using boundary-fitted coordinate system method

    Science.gov (United States)

    Lee, Kang-Kun; Leap, Darrell I.

    1997-09-01

    The boundary-fitted coordinate (BFC) system method is applied to simulate steady groundwater seepage with a free-surface and seepage face using the finite-difference method. The BFC system method eliminates the difficulty of fitting finite-difference grids to a changeable free-surface which is not known a priori but will be obtained as part of a solution. Also, grid generation with this approach is simpler than with the finite-element method. At each iterative sweep, the changeable free-surface becomes a part of the boundary-fitted grid lines, making boundary condition implementation easy and accurate. An example problem demonstrating the simulation procedure and numerical results compares very well with the analytical solution.

  12. Validation of AIRS V6 Surface Temperature over Greenland with GCN and NOAA Stations

    Science.gov (United States)

    Lee, Jae N.; Hearty, Thomas; Cullather, Richard; Nowicki, Sophie; Susskind, Joel

    2016-01-01

    This work compares the temporal and spatial characteristics of the AIRSAMSU (Atmospheric Infrared Sounder Advanced Microwave Sounding Unit A) Version 6 and MODIS (Moderate resolution Imaging Spectroradiometer) Collection 5 derived surface temperatures over Greenland. To estimate uncertainties in space-based surface temperature measurements, we re-projected the MODIS Ice Surface Temperature (IST) to 0.5 by 0.5 degree spatial resolution. We also re-gridded AIRS Skin Temperature (Ts) into the same grid but classified with different cloud conditions and surface types. These co-located data sets make intercomparison between the two instruments relatively straightforward. Using this approach, the spatial comparison between the monthly mean AIRS Ts and MODIS IST is in good agreement with RMS 2K for May 2012. This approach also allows the detection of any long-term calibration drift and the careful examination of calibration consistency in the MODIS and AIRS temperature data record. The temporal correlations between temperature data are also compared with those from in-situ measurements from GC-Net (GCN) and NOAA stations. The coherent time series of surface temperature evident in the correlation between AIRS Ts and GCN temperatures suggest that at monthly time scales both observations capture the same climate signal over Greenland. It is also suggested that AIRS surface air temperature (Ta) can be used to estimate the boundary layer inversion.

  13. Importance of initial buoyancy field on evolution of mantle thermal structure:Implications of surface boundary conditions

    Institute of Scientific and Technical Information of China (English)

    Petar Glisovic; Alessandro M. Forte

    2015-01-01

    Although there has been significant progress in the seismic imaging of mantle heterogeneity, the outstanding issue that remains to be resolved is the unknown distribution of mantle temperature anomalies in the distant geological past that give rise to the present-day anomalies inferred by global tomography models. To address this question, we present 3-D convection models in compressible and self-gravitating mantle initialised by different hypothetical temperature patterns. A notable feature of our forward convection modelling is the use of self-consistent coupling of the motion of surface tectonic plates to the underlying mantle flow, without imposing prescribed surface velocities (i.e., plate-like boundary condition). As an approximation for the surface mechanical conditions before plate tectonics began to operate we employ the no-slip (rigid) boundary condition. A rigid boundary condition dem-onstrates that the initial thermally-dominated structure is preserved, and its geographical location is fixed during the evolution of mantle flow. Considering the impact of different assumed surface boundary conditions (rigid and plate-like) on the evolution of thermal heterogeneity in the mantle we suggest that the intrinsic buoyancy of seven superplumes is most-likely resolved in the tomographic images of present-day mantle thermal structure. Our convection simulations with a plate-like boundary condition reveal that the evolution of an initial cold anomaly beneath the Java-Indonesian trench system yields a long-term, stable pattern of thermal heterogeneity in the lowermost mantle that resembles the present-day Large Low Shear Velocity Provinces (LLSVPs), especially below the Pacific. The evolution of sub-duction zones may be, however, influenced by the mantle-wide flow driven by deeply-rooted and long-lived superplumes since Archean times. These convection models also detect the intrinsic buoyancy of the Perm Anomaly that has been identified as a unique slow feature

  14. Martian Surface Temperature and Spectral Response from the MSL REMS Ground Temperature Sensor

    Science.gov (United States)

    Martin-Torres, Javier; Martínez-Frías, Jesús; Zorzano, María-Paz; Serrano, María; Mendaza, Teresa; Hamilton, Vicky; Sebastián, Eduardo; Armiens, Carlos; Gómez-Elvira, Javier; REMS Team

    2013-04-01

    The Rover Environmental Monitoring Station (REMS) on the Mars Science Laboratory (MSL) offers the opportunity to explore the near surface atmospheric conditions and, in particular will shed new light into the heat budget of the Martian surface. This is important for studies of the atmospheric boundary layer (ABL), as the ground and air temperatures measured directly by REMS control the coupling of the atmosphere with the surface [Zurek et al., 1992]. This coupling is driven by solar insolation. The ABL plays an important role in the general circulation and the local atmospheric dynamics of Mars. One of the REMS sensors, the ground temperature sensor (GTS), provides the data needed to study the thermal inertia properties of the regolith and rocks beneath the MSL rover. The GTS includes thermopile detectors, with infrared bands of 8-14 µm and 16-20 µm [Gómez-Elvira et al., 2012]. These sensors are clustered in a single location on the MSL mast and the 8-14 µm thermopile sounds the surface temperature. The infrared radiation reaching the thermopile is proportional to the emissivity of the surface minerals across these thermal wavelengths. We have developed a radiative transfer retrieval method for the REMS GTS using a database of thermal infrared laboratory spectra of analogue minerals and their mixtures. [Martín Redondo et al. 2009, Martínez-Frías et al. 2012 - FRISER-IRMIX database]. This method will be used to assess the perfomance of the REMS GTS as well as determine, through the error analysis, the surface temperature and emissivity values where MSL is operating. Comparisons with orbiter data will be performed. References Gómez-Elvira et al. [2012], REMS: The Environmental Sensor Suite for the Mars Science Laboratory Rover, Space Science Reviews, Volume 170, Issue 1-4, pp. 583-640. Martín-Redondo et al. [2009] Journal of Environmental Monitoring 11:, pp. 1428-1432. Martínez-Frías et al. [2012] FRISER-IRMIX database http

  15. Seasonality of submesoscale flows in the ocean surface boundary layer

    Science.gov (United States)

    Buckingham, Christian E.; Naveira Garabato, Alberto C.; Thompson, Andrew F.; Brannigan, Liam; Lazar, Ayah; Marshall, David P.; George Nurser, A. J.; Damerell, Gillian; Heywood, Karen J.; Belcher, Stephen E.

    2016-03-01

    A signature of submesoscale flows in the upper ocean is skewness in the distribution of relative vorticity. Expected to result for high Rossby number flows, such skewness has implications for mixing, dissipation, and stratification within the upper ocean. An array of moorings deployed in the Northeast Atlantic for 1 year as part of the experiment of the Ocean Surface Mixing, Ocean Submesoscale Interaction Study (OSMOSIS) reveals that relative vorticity is positively skewed during winter even though the scale of the Rossby number is less than 0.5. Furthermore, this skewness is reduced to zero during spring and autumn. There is also evidence of modest seasonal variations in the gradient Rossby number. The proposed mechanism by which relative vorticity is skewed is that the ratio of lateral to vertical buoyancy gradients, as summarized by the inverse gradient Richardson number, restricts its range during winter but less so at other times of the year. These results support recent observations and model simulations suggesting that the upper ocean is host to a seasonal cycle in submesoscale turbulence.

  16. Laboratory investigation of a thermally stable boundary layer subject to a step change in wall temperature

    Science.gov (United States)

    van Buren, Tyler; Williams, Owen J.; Smits, Alexander J.

    2014-11-01

    Thermally stable boundary layers with a step change in boundary condition are seen in industrial applications (e.g. plate heat exchangers) as well as in nature (e.g. onshore breezes). Previous studies indicate that bulk indicators of stability are often insufficient to describe the local state of turbulence because the local flow strongly depends on its upstream history. Experiments were conducted to gain further insight into these flows. A low-speed wind tunnel was used to generate a rough-wall boundary layer at up to Reθ = 1500 . After a development length of approximately 22 δ , the downstream half of the tunnel wall was heated, creating a step change in wall temperature of up to 135° C . Particle image velocimetry and a thermocouple rake were used to measure the fluctuating velocity field and mean temperature profile at three locations downstream of the step change. We examine the rate of growth of the internal boundary layer and the corresponding evolution of the turbulent stresses in relation to changes in mean local stratification. This work was supported by the Princeton University Cooperative Institute for Climate Science.

  17. Finite-temperature effective boundary theory of the quantized thermal Hall effect

    Science.gov (United States)

    Nakai, Ryota; Ryu, Shinsei; Nomura, Kentaro

    2016-02-01

    A finite-temperature effective free energy of the boundary of a quantized thermal Hall system is derived microscopically from the bulk two-dimensional Dirac fermion coupled with a gravitational field. In two spatial dimensions, the thermal Hall conductivity of fully gapped insulators and superconductors is quantized and given by the bulk Chern number, in analogy to the quantized electric Hall conductivity in quantum Hall systems. From the perspective of effective action functionals, two distinct types of the field theory have been proposed to describe the quantized thermal Hall effect. One of these, known as the gravitational Chern-Simons action, is a kind of topological field theory, and the other is a phenomenological theory relevant to the Strěda formula. In order to solve this problem, we derive microscopically an effective theory that accounts for the quantized thermal Hall effect. In this paper, the two-dimensional Dirac fermion under a static background gravitational field is considered in equilibrium at a finite temperature, from which an effective boundary free energy functional of the gravitational field is derived. This boundary theory is shown to explain the quantized thermal Hall conductivity and thermal Hall current in the bulk by assuming the Lorentz symmetry. The bulk effective theory is consistently determined via the boundary effective theory.

  18. Temperature Reconstruction and Biomarker Variation across the Cretaceous-Paleogene Boundary, Mid-Waipara River, New Zealand

    Science.gov (United States)

    Taylor, K. W.; Hollis, C. J.; Pancost, R. D.

    2010-12-01

    The Cretaceous-Paleogene (K/Pg) boundary marks a catastrophic global extinction event, believed to be caused by an asteroid impact in northern Yucatan. Whilst the extent of mass extinction is well documented, there is ongoing debate about the immediate and longer term climatic and environmental changes triggered by the event. The northern South Island of New Zealand has several records of the K/Pg boundary, representing a range of terrestrial and marine environments. Previous studies of terrestrial palynomorphs and siliceous microfossils from these sections suggested significant cooling and terrestrial vegetation reconfiguration in the earliest Paleocene. Extinctions or local disappearances of thermophilic taxa at the K/Pg boundary are consistent with the hypothesis of a short-lived “impact winter”. The Mid-Waipara K/Pg boundary section, north Canterbury, has been identified as suitable for organic geochemical study because sufficient organic carbon is present in the siliciclastic sediments and is thermally immature. Sediments were deposited in outer shelf to upper slope depths under a neritic watermass. New estimates of sea surface temperature variation based on TEX86 elucidate the relationship between biological and climatic changes that followed the K/Pg event. Within the 0.25 m-thick interval identified as the “fern spike” in basal Paleocene sediments in this section there is no indication of a significant change in temperature relative to the Cretaceous (22-25°C). Foraminiferal and radiolarian biostratigraphy indicates that this interval spans ~100 kyrs and includes a fern succession from colonising ground ferns to tree ferns, the latter suggesting a temperate, humid climate. The transition from ferns to a conifer-dominated pollen assemblage corresponds with a remarkable decrease in temperature recorded in the TEX86 record. These cool temperatures persist over 10 m. The dominant conifer pollen type over this interval is Phyllocladites mawsonii

  19. Long-term climate patterns in Alaskan surface temperature and precipitation and their biological consequences

    Science.gov (United States)

    Simpson, James J.; Hufford, Gary L.; Fleming, Michael D.; Berg, Jared S.; Ashton, J.B.

    2002-01-01

    Mean monthly climate maps of Alaskan surface temperature and precipitation produced by the parameter-elevation regression on independent slopes model (PRISM) were analyzed. Alaska is divided into interior and coastal zones with consistent but different climatic variability separated by a transition region; it has maximum interannual variability but low long-term mean variability. Pacific decadal oscillation (PDO)- and El Nin??o southern oscillation (ENSO)-type events influence Alaska surface temperatures weakly (1-2 ??C) statewide. PDO has a stronger influence than ENSO on precipitation but its influence is largely localized to coastal central Alaska. The strongest influence of Arctic oscillation (AO) occurs in northern and interior Alaskan precipitation. Four major ecosystems are defined. A major eco-transition zone occurs between the interior boreal forest and the coastal rainforest. Variability in insolation, surface temperature, precipitation, continentality, and seasonal changes in storm track direction explain the mapped ecosystems. Lack of westward expansion of the interior boreal forest into the western shrub tundra is influenced by the coastal marine boundary layer (enhanced cloud cover, reduced insolation, cooler surface and soil temperatures). In this context, the marine boundary layer acts in an analogous fashion to the orographic features which form the natural boundaries of other Alaskan ecosystems. Variability in precipitation may play a secondary role.

  20. Monitoring temperature and pressure over surfaces using sensitive paints

    Science.gov (United States)

    Guerrero-Viramontes, J. Ascención; Moreno Hernández, David; Mendoza Santoyo, Fernando; Morán Loza, José Miguel; García Arreola, Alicia

    2007-03-01

    Two techniques for monitoring temperature and pressure variations over surfaces using sensitive paints are presented. The analysis is done by the acquisition of a set of images of the surface under analysis. The surface is painted by a paint called Pressure Sensitive Paint (PSP) for pressure measurements and Temperature Sensitive Paints (TSP) for temperature measurements. These kinds of paints are deposited over the surface under analysis. The recent experimental advances in calibration process are presented in this paper.

  1. Free surface simulation of a two-layer fluid by boundary element method

    Directory of Open Access Journals (Sweden)

    Weoncheol Koo

    2010-09-01

    Full Text Available A two-layer fluid with free surface is simulated in the time domain by a two-dimensional potential-based Numerical Wave Tank (NWT. The developed NWT is based on the boundary element method and a leap-frog time integration scheme. A whole domain scheme including interaction terms between two layers is applied to solve the boundary integral equation. The time histories of surface elevations on both fluid layers in the respective wave modes are verified with analytic results. The amplitude ratios of upper to lower elevation for various density ratios and water depths are also compared.

  2. Boundary layer flow past a stretching surface in a porous medium saturated by a nanofluid: Brinkman-Forchheimer model.

    Directory of Open Access Journals (Sweden)

    Waqar A Khan

    Full Text Available In this study, the steady forced convection flow and heat transfer due to an impermeable stretching surface in a porous medium saturated with a nanofluid are investigated numerically. The Brinkman-Forchheimer model is used for the momentum equations (porous medium, whereas, Bongiorno's model is used for the nanofluid. Uniform temperature and nanofluid volume fraction are assumed at the surface. The boundary layer equations are transformed to ordinary differential equations in terms of the governing parameters including Prandtl and Lewis numbers, viscosity ratio, porous medium, Brownian motion and thermophoresis parameters. Numerical results for the velocity, temperature and concentration profiles, as well as for the reduced Nusselt and Sherwood numbers are obtained and presented graphically.

  3. Heat transfer, velocity-temperature correlation, and turbulent shear stress from Navier-Stokes computations of shock wave/turbulent boundary layer interaction flows

    Science.gov (United States)

    Wang, C. R.; Hingst, W. R.; Porro, A. R.

    1991-01-01

    The properties of 2-D shock wave/turbulent boundary layer interaction flows were calculated by using a compressible turbulent Navier-Stokes numerical computational code. Interaction flows caused by oblique shock wave impingement on the turbulent boundary layer flow were considered. The oblique shock waves were induced with shock generators at angles of attack less than 10 degs in supersonic flows. The surface temperatures were kept at near-adiabatic (ratio of wall static temperature to free stream total temperature) and cold wall (ratio of wall static temperature to free stream total temperature) conditions. The computational results were studied for the surface heat transfer, velocity temperature correlation, and turbulent shear stress in the interaction flow fields. Comparisons of the computational results with existing measurements indicated that (1) the surface heat transfer rates and surface pressures could be correlated with Holden's relationship, (2) the mean flow streamwise velocity components and static temperatures could be correlated with Crocco's relationship if flow separation did not occur, and (3) the Baldwin-Lomax turbulence model should be modified for turbulent shear stress computations in the interaction flows.

  4. Evaluation of simulated climatological diurnal temperature range in CMIP5 models from the perspective of planetary boundary layer turbulent mixing

    Science.gov (United States)

    Wei, Nan; Zhou, Liming; Dai, Yongjiu

    2017-07-01

    This study examines the effects of modeled planetary boundary layer (PBL) mixing on the simulated temperature diurnal cycle climatology over land in 20 CMIP5 models with AMIP simulations. When compared with observations, the magnitude of diurnal temperature range (DTR) is systematically underestimated over almost all land areas due to a widespread warm bias of daily minimum temperature (Tmin) and mostly a cold bias of daily maximum temperature (Tmax). Analyses of the CMIP5 multi-model ensemble means suggest that the biases of the simulated PBL mixing could very likely contribute to the temperature biases. For the regions with the cold bias in Tmax, the daytime PBL mixing is generally underestimated. The consequent more dry air entrainment from the free atmosphere could help maintain the surface humidity gradient, and thus produce more surface evaporation and potentially lower the Tmax. The opposite situation holds true for the regions with the warm bias of Tmax. This mechanism could be particularly applicable to the regions with moderate and wet climate conditions where surface evaporation depends more on the surface humidity gradient, but less on the available soil moisture. For the widespread warm bias of Tmin, the widely-recognized overestimated PBL mixing at nighttime should play a dominant role by transferring more heat from the atmosphere to the near-surface to warm the Tmin. Further analyses using the high resolution CFMIP2 output also support the CMIP5 results about the connections of the biases between the simulated turbulent mixing and the temperature diurnal cycle. The large inter-model variations of the simulated temperature diurnal cycle primarily appear over the arid and semi-arid regions and boreal arctic regions where the model differences in the PBL turbulence mixing could make equally significant contributions to the inter-model variations of DTR, Tmax and Tmin compared to the model differences in surface radiative processes. These results

  5. Evaluation of simulated climatological diurnal temperature range in CMIP5 models from the perspective of planetary boundary layer turbulent mixing

    Science.gov (United States)

    Wei, Nan; Zhou, Liming; Dai, Yongjiu

    2016-08-01

    This study examines the effects of modeled planetary boundary layer (PBL) mixing on the simulated temperature diurnal cycle climatology over land in 20 CMIP5 models with AMIP simulations. When compared with observations, the magnitude of diurnal temperature range (DTR) is systematically underestimated over almost all land areas due to a widespread warm bias of daily minimum temperature (Tmin) and mostly a cold bias of daily maximum temperature (Tmax). Analyses of the CMIP5 multi-model ensemble means suggest that the biases of the simulated PBL mixing could very likely contribute to the temperature biases. For the regions with the cold bias in Tmax, the daytime PBL mixing is generally underestimated. The consequent more dry air entrainment from the free atmosphere could help maintain the surface humidity gradient, and thus produce more surface evaporation and potentially lower the Tmax. The opposite situation holds true for the regions with the warm bias of Tmax. This mechanism could be particularly applicable to the regions with moderate and wet climate conditions where surface evaporation depends more on the surface humidity gradient, but less on the available soil moisture. For the widespread warm bias of Tmin, the widely-recognized overestimated PBL mixing at nighttime should play a dominant role by transferring more heat from the atmosphere to the near-surface to warm the Tmin. Further analyses using the high resolution CFMIP2 output also support the CMIP5 results about the connections of the biases between the simulated turbulent mixing and the temperature diurnal cycle. The large inter-model variations of the simulated temperature diurnal cycle primarily appear over the arid and semi-arid regions and boreal arctic regions where the model differences in the PBL turbulence mixing could make equally significant contributions to the inter-model variations of DTR, Tmax and Tmin compared to the model differences in surface radiative processes. These results

  6. Parallel Higher-order Boundary Integral Electrostatics Computation on Molecular Surfaces with Curved Triangulation

    CERN Document Server

    Geng, Weihua

    2013-01-01

    In this paper, we present a parallel higher-order boundary integral method to solve the linear Poisson-Boltzmann (PB) equation. In our method, a well-posed boundary integral formulation is used to ensure the fast convergence of Krylov subspace linear solver such as GMRES. The molecular surfaces are first discretized with flat triangles and then converted to curved triangles with the assistance of normal information at vertices. To maintain the desired accuracy, four-point Gauss-Radau quadratures are used on regular triangles and sixteen-point Gauss-Legendre quadratures together with regularization transformations are applied on singular triangles. To speed up our method, we take advantage of the embarrassingly parallel feature of boundary integral formulation, and parallelize the schemes with the message passing interface (MPI) implementation. Numerical tests show significantly improved accuracy and convergence of the proposed higher-order boundary integral Poisson-Boltzmann (HOBI-PB) solver compared with bou...

  7. The effect of surface charge on the boundary slip of various oleophilic/phobic surfaces immersed in liquids.

    Science.gov (United States)

    Li, Yifan; Bhushan, Bharat

    2015-10-14

    The reduction of fluid drag is an important issue in many fluid flow applications at the micro/nanoscale. Boundary slip is believed to affect fluid drag. Slip length has been measured on various surfaces with different degrees of hydrophobicity and oleophobicity immersed in various liquids of scientific interest. Surface charge has been found to affect slip length in water and electrolytes. However, there are no studies on the effect of surface charge on slip at solid-oil interfaces. This study focuses on the effect of surface charge on the boundary slip of superoleophilic, oleophilic, oleophobic, and superoleophobic surfaces immersed in deionized (DI) water and hexadecane and ethylene glycol, based on atomic force microscopy (AFM). The surface charge was changed by applying a positive electric field to the solid-liquid interface, and by using liquids with different pH values. The results show that slip length increases with an increase in applied positive electric field voltage. Slip length also increases with a decrease in the pH of the solutions. The change in slip length is dependent on the absolute value of the surface charge, and a larger surface charge density results in a smaller slip length. In addition, the surface charge density at different solid-liquid interfaces is related to the dielectric properties of the surface. The underlying mechanisms are analyzed.

  8. Estimation of sea surface temperature (SST) using marine seismic data

    Digital Repository Service at National Institute of Oceanography (India)

    Sinha, S.K.; Dewangan, P.; Sain, K.

    .g. Wu et al. [1999]). However, due to the skin effect, sea surface temperatures as measured by satellites can be very different from temperatures a few centimeters below the sea surface (i.e. in-situ temperatures) [Emery et al., 1994]. Therefore...

  9. Noncontact Monitoring of Surface Temperature Distribution by Laser Ultrasound Scanning

    Science.gov (United States)

    Yamada, Hiroyuki; Kosugi, Akira; Ihara, Ikuo

    2011-07-01

    A laser ultrasound scanning method for measuring a surface temperature distribution of a heated material is presented. An experiment using an aluminum plate heated up to 120 °C is carried out to verify the feasibility of the proposed method. A series of one-dimensional surface acoustic wave (SAW) measurements within an area of a square on the aluminum surface are performed by scanning a pulsed laser for generating SAW using a galvanometer system, where the SAWs are detected at a fixed location on the surface. An inverse analysis is then applied to SAW data to determine the surface temperature distribution in a certain direction. The two-dimensional distribution of the surface temperature in the square is constructed by combining the one-dimensional surface temperature distributions obtained within the square. The surface temperature distributions obtained by the proposed method almost agrees with those obtained using an infrared radiation camera.

  10. Extension of physical component BFC method for the analysis of free-surface flows coupled with moving boundaries

    Science.gov (United States)

    Lu, D.; Takizawa, A.; Kondo, S.

    A newly developed ``physical component boundary fitted coordinate (PCBFC) method'' is extended for the analysis of free-surface flows coupled with moving boundaries. Extra techniques are employed to deal with the coupling movement of the free surface and moving boundaries. After the validation of the extension by several benchmark problems, the method is successfully applied for the first time to the simulation of overflow-induced vibration of the weir coupled with sloshing of the free-surface liquid.

  11. Localized electronic states at grain boundaries on the surface of graphene and graphite

    Science.gov (United States)

    Luican-Mayer, Adina; Barrios-Vargas, Jose E.; Toft Falkenberg, Jesper; Autès, Gabriel; Cummings, Aron W.; Soriano, David; Li, Guohong; Brandbyge, Mads; Yazyev, Oleg V.; Roche, Stephan; Andrei, Eva Y.

    2016-09-01

    Recent advances in large-scale synthesis of graphene and other 2D materials have underscored the importance of local defects such as dislocations and grain boundaries (GBs), and especially their tendency to alter the electronic properties of the material. Understanding how the polycrystalline morphology affects the electronic properties is crucial for the development of applications such as flexible electronics, energy harvesting devices or sensors. We here report on atomic scale characterization of several GBs and on the structural-dependence of the localized electronic states in their vicinity. Using low temperature scanning tunneling microscopy and spectroscopy, together with tight binding and ab initio numerical simulations we explore GBs on the surface of graphite and elucidate the interconnection between the local density of states and their atomic structure. We show that the electronic fingerprints of these GBs consist of pronounced resonances which, depending on the relative orientation of the adjacent crystallites, appear either on the electron side of the spectrum or as an electron-hole symmetric doublet close to the charge neutrality point. These two types of spectral features will impact very differently the transport properties allowing, in the asymmetric case to introduce transport anisotropy which could be utilized to design novel growth and fabrication strategies to control device performance.

  12. Method of determination of temperature and heat resistance of the points on the integrated circuit crystal surface

    Directory of Open Access Journals (Sweden)

    Popov V. M.

    2011-12-01

    Full Text Available Method for visualization of integrated circuit (IC surface temperature by means of the liquid crystal film deposited from solution on its surface is proposed. The boundaries of local regions represent isotherms with corresponding phase transitions. On the base of isotherms positions and consumed by IC power thermal resistances between crystal and environment are determined.

  13. Effect of the severe plastic deformation temperature on the diffusion properties of the grain boundaries in ultrafine-grained metals

    Science.gov (United States)

    Chuvil'deev, V. N.; Myshlyaev, M. M.; Nokhrin, A. V.; Kopylov, V. I.; Lopatin, Yu. G.; Pirozhnikova, O. E.; Piskunov, A. V.; Semenycheva, A. V.; Bobrov, A. A.

    2017-05-01

    A model is proposed to explain the effect of the severe plastic deformation (SPD) temperature on the diffusion properties of the grain boundaries in ultrafine-grained (UFG) metals and alloys. It is shown that an increase in the SPD temperature in UFG metals leads to an increase in the activation energy of grainboundary diffusion from (3-5) k B T m, which corresponds to the diffusion parameters of nonequilibrium grain boundaries, to (8-10) k B T m, which corresponds to the diffusion parameters of equilibrium grain boundaries ( k B is the Boltzmann constant, T m is the melting temperature). The dependence of the activation energy of grain-boundary diffusion on the SPD temperature is found to be determined by the kinetics of the competing processes of defect accumulation at grain boundaries and the diffusion accommodation of defects.

  14. Analytic Approximate Solutions for MHD Boundary-Layer Viscoelastic Fluid Flow over Continuously Moving Stretching Surface by Homotopy Analysis Method with Two Auxiliary Parameters

    Directory of Open Access Journals (Sweden)

    M. M. Rashidi

    2012-01-01

    Full Text Available In this study, a steady, incompressible, and laminar-free convective flow of a two-dimensional electrically conducting viscoelastic fluid over a moving stretching surface through a porous medium is considered. The boundary-layer equations are derived by considering Boussinesq and boundary-layer approximations. The nonlinear ordinary differential equations for the momentum and energy equations are obtained and solved analytically by using homotopy analysis method (HAM with two auxiliary parameters for two classes of visco-elastic fluid (Walters’ liquid B and second-grade fluid. It is clear that by the use of second auxiliary parameter, the straight line region in ℏ-curve increases and the convergence accelerates. This research is performed by considering two different boundary conditions: (a prescribed surface temperature (PST and (b prescribed heat flux (PHF. The effect of involved parameters on velocity and temperature is investigated.

  15. Combined effects of surface conditions, boundary layer dynamics and chemistry on diurnal SOA evolution

    Directory of Open Access Journals (Sweden)

    R. H. H. Janssen

    2012-08-01

    Full Text Available We study the combined effects of land surface conditions, atmospheric boundary layer dynamics and chemistry on the diurnal evolution of biogenic secondary organic aerosol in the atmospheric boundary layer, using a model that contains the essentials of all these components. First, we evaluate the model for a case study in Hyytiälä, Finland, and find that it is able to satisfactorily reproduce the observed dynamics and gas-phase chemistry. We show that the exchange of organic aerosol between the free troposphere and the boundary layer (entrainment must be taken into account in order to explain the observed diurnal cycle in organic aerosol (OA concentration. An examination of the budgets of organic aerosol and terpene concentrations show that the former is dominated by entrainment, while the latter is mainly driven by emission and chemical transformation. We systematically investigate the role of the land surface, which governs both the surface energy balance partitioning and terpene emissions, and the large-scale atmospheric process of vertical subsidence. Entrainment is especially important for the dilution of organic aerosol concentrations under conditions of dry soils and low terpene emissions. Subsidence suppresses boundary layer growth while enhancing entrainment. Therefore, it influences the relationship between organic aerosol and terpene concentrations. Our findings indicate that the diurnal evolution of secondary organic aerosols (SOA in the boundary layer is the result of coupled effects of the land surface, dynamics of the atmospheric boundary layer, chemistry, and free troposphere conditions. This has potentially some consequences for the design of both field campaigns and large-scale modeling studies.

  16. Interactions of the land-surface with the atmospheric boundary layer

    NARCIS (Netherlands)

    Ek, M.B.

    2005-01-01

    We study daytime land-atmosphere interaction using a one-dimensional (column) coupled land-surface - atmospheric boundary-Iayer (ABL) model and data sets gathered at Cabauw (1978, central Netherlands) and during the Hydrological and Atmospheric Pilot Experiment - Modélisation du Bilan Hydrique (HAPE

  17. Impact of Bay-Breeze Circulations on Surface Air Quality and Boundary Layer Export

    Science.gov (United States)

    Loughner, Christopher P.; Tzortziou, Maria; Follette-Cook, Melanie; Pickering, Kenneth E.; Goldberg, Daniel; Satam, Chinmay; Weinheimer, Andrew; Crawford, James H.; Knapp, David J.; Montzka, Denise D.; hide

    2014-01-01

    Meteorological and air-quality model simulations are analyzed alongside observations to investigate the role of the Chesapeake Bay breeze on surface air quality, pollutant transport, and boundary layer venting. A case study was conducted to understand why a particular day was the only one during an 11-day ship-based field campaign on which surface ozone was not elevated in concentration over the Chesapeake Bay relative to the closest upwind site and why high ozone concentrations were observed aloft by in situ aircraft observations. Results show that southerly winds during the overnight and early-morning hours prevented the advection of air pollutants from the Washington, D.C., and Baltimore, Maryland, metropolitan areas over the surface waters of the bay. A strong and prolonged bay breeze developed during the late morning and early afternoon along the western coastline of the bay. The strength and duration of the bay breeze allowed pollutants to converge, resulting in high concentrations locally near the bay-breeze front within the Baltimore metropolitan area, where they were then lofted to the top of the planetary boundary layer (PBL). Near the top of the PBL, these pollutants were horizontally advected to a region with lower PBL heights, resulting in pollution transport out of the boundary layer and into the free troposphere. This elevated layer of air pollution aloft was transported downwind into New England by early the following morning where it likely mixed down to the surface, affecting air quality as the boundary layer grew.

  18. Null exact controllability of the parabolic equations with equivalued surface boundary condition

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available This paper is devoted to showing the null exact controllability for a class of parabolic equations with equivalued surface boundary condition. Our method is based on the duality argument and global Carleman-type estimate for a parabolic operator.

  19. On inferring isoprene emission surface flux from atmospheric boundary layer concentration measurements

    NARCIS (Netherlands)

    Vilà-Guerau de Arellano, J.; Dries, van den K.; Pino, D.

    2009-01-01

    We examine the dependence of the inferred isoprene surface emission flux from atmospheric concentration on the diurnal variability of the convective boundary layer (CBL). A series of systematic numerical experiments carried out using the mixed-layer technique enabled us to study the sensitivity of i

  20. A second-order boundary-fitted projection method for free-surface flow computations

    NARCIS (Netherlands)

    Yang, B.; Prosperetti, A.

    2006-01-01

    This paper describes a new approach to the high-fidelity simulation of axisymmetric free-surface flows. A boundary-fitted grid is coupled with a new projection method for the solution of the Navier–Stokes equations with second-order accuracy in space and time. Two variants of this new method are dev

  1. Tuning of turbulent boundary layer anisotropy for improved surface pressure and trailing-edge noise modeling

    DEFF Research Database (Denmark)

    Bertagnolio, Franck; Fischer, Andreas; Zhu, Wei Jun

    2014-01-01

    The modeling of the surface pressure spectrum beneath a turbulent boundary layer is investigated, focusing on the case of airfoil flows and associated trailing edge noise prediction using the so-called TNO model. This type of flow is characterized by the presence of an adverse pressure gradient a...

  2. Technique for the estimation of surface temperatures from embedded temperature sensing for rapid, high energy surface deposition.

    Energy Technology Data Exchange (ETDEWEB)

    Watkins, Tyson R.; Schunk, Peter Randall; Roberts, Scott Alan

    2014-07-01

    Temperature histories on the surface of a body that has been subjected to a rapid, highenergy surface deposition process can be di cult to determine, especially if it is impossible to directly observe the surface or attach a temperature sensor to it. In this report, we explore two methods for estimating the temperature history of the surface through the use of a sensor embedded within the body very near to the surface. First, the maximum sensor temperature is directly correlated with the peak surface temperature. However, it is observed that the sensor data is both delayed in time and greatly attenuated in magnitude, making this approach unfeasible. Secondly, we propose an algorithm that involves tting the solution to a one-dimensional instantaneous energy solution problem to both the sensor data and to the results of a one-dimensional CVFEM code. This algorithm is shown to be able to estimate the surface temperature 20 C.

  3. The Turbulent Boundary Layer on a Horizontally Moving, Partially Submerged, Surface-Piercing Vertical Wall

    CERN Document Server

    Washuta, Nathan; Duncan, James H

    2016-01-01

    The complex interactions between turbulence and the free surface, including air entrainment processes, in boundary layer shear flows created by vertical surface-piercing plates are considered. A laboratory-scale device was built that utilizes a surface-piercing stainless steel belt that travels in a loop around two vertical rollers, with one length of the belt between the rollers acting as a horizontally-moving flat wall. The belt is operated both as a suddenly-started plate to reproduce boundary layer flow or at steady state in the presence of a stationary flat plate positioned parallel to the belt to create a Couette flow with a free surface. Surface profiles are measured with a cinematic laser-induced fluorescence system in both experiments and air entrainment events and bubble motions are observed with stereo underwater white-light movies in the suddenly started belt experiment. It is found that the RMS surface height fluctuations, $\\eta$, peak near the boundaries of the flows and increase approximately l...

  4. Evaluation of near-surface temperature, humidity, and equivalent temperature from regional climate models applied in type II downscaling

    Science.gov (United States)

    Pryor, S. C.; Schoof, J. T.

    2016-04-01

    Atmosphere-surface interactions are important components of local and regional climates due to their key roles in dictating the surface energy balance and partitioning of energy transfer between sensible and latent heat. The degree to which regional climate models (RCMs) represent these processes with veracity is incompletely characterized, as is their ability to capture the drivers of, and magnitude of, equivalent temperature (Te). This leads to uncertainty in the simulation of near-surface temperature and humidity regimes and the extreme heat events of relevance to human health, in both the contemporary and possible future climate states. Reanalysis-nested RCM simulations are evaluated to determine the degree to which they represent the probability distributions of temperature (T), dew point temperature (Td), specific humidity (q) and Te over the central U.S., the conditional probabilities of Td|T, and the coupling of T, q, and Te to soil moisture and meridional moisture advection within the boundary layer (adv(Te)). Output from all RCMs exhibits discrepancies relative to observationally derived time series of near-surface T, q, Td, and Te, and use of a single layer for soil moisture by one of the RCMs does not appear to substantially degrade the simulations of near-surface T and q relative to RCMs that employ a four-layer soil model. Output from MM5I exhibits highest fidelity for the majority of skill metrics applied herein, and importantly most realistically simulates both the coupling of T and Td, and the expected relationships of boundary layer adv(Te) and soil moisture with near-surface T and q.

  5. Determination of Land Surface Temperature (LST) and Potential ...

    African Journals Online (AJOL)

    Determination of Land Surface Temperature (LST) and Potential Urban Heat Island Effect in Parts of Lagos State using Satellite ... Changes in temperature appear to be closely related to concentrations of atmospheric carbon dioxide.

  6. The Diurnal Cycle of the Boundary Layer, Convection, Clouds, and Surface Radiation in a Coastal Monsoon Environment (Darwin Australia)

    Energy Technology Data Exchange (ETDEWEB)

    May, Peter T.; Long, Charles N.; Protat, Alain

    2012-08-01

    The diurnal variation of convection and associated cloud and radiative properties remains a significant issue in global NWP and climate models. This study analyzes observed diurnal variability of convection in a coastal monsoonal environment examining the interaction of convective rain clouds, their associated cloud properties, and the impact on the surface radiation and corresponding boundary layer structure during periods where convection is suppressed or active on the large scale. The analysis uses data from the Tropical Warm Pool International Cloud Experiment (TWP-ICE) as well as routine measurements from the Australian Bureau of Meteorology and the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program. Both active monsoonal and large-scale suppressed (buildup and break) conditions are examined and demonstrate that the diurnal variation of rainfall is much larger during the break periods and the spatial distribution of rainfall is very different between the monsoon and break regimes. During the active monsoon the total net radiative input to the surface is decreased by more than 3 times the amount than during the break regime - this total radiative cloud forcing is found to be dominated by the shortwave (SW) cloud effects because of the much larger optical thicknesses and persistence of long-lasting anvils and cirrus cloud decks associated with the monsoon regime. These differences in monsoon versus break surface radiative energy contribute to low-level air temperature differences in the boundary layer over the land surfaces.

  7. Conformal field theory of critical Casimir forces between surfaces with alternating boundary conditions in two dimensions

    Science.gov (United States)

    Dubail, J.; Santachiara, R.; Emig, T.

    2017-03-01

    Systems as diverse as binary mixtures and inclusions in biological membranes, and many more, can be described effectively by interacting spins. When the critical fluctuations in these systems are constrained by boundary conditions, critical Casimir forces (CCF) emerge. Here we analyze CCF between boundaries with alternating boundary conditions in two dimensions, employing conformal field theory (CFT). After presenting the concept of boundary changing operators, we specifically consider two different boundary configurations for a strip of critical Ising spins: (I) alternating equi-sized domains of up and down spins on both sides of the strip, with a possible lateral shift, and (II) alternating domains of up and down spins of different size on one side and homogeneously fixed spins on the other side of the strip. Asymptotic results for the CCF at small and large distances are derived. We introduce a novel modified Szegö formula for determinants of real antisymmetric block Toeplitz matrices to obtain the exact CCF and the corresponding scaling functions at all distances. We demonstrate the existence of a surface renormalization group flow between universal force amplitudes of different magnitude and sign. The Casimir force can vanish at a stable equilibrium position that can be controlled by parameters of the boundary conditions. Lateral Casimir forces assume a universal simple cosine form at large separations.

  8. Temperature-Sensing Behavior Based on Upconversion Luminescence at the Rhombohedral-Tetragonal Phase Boundary

    Science.gov (United States)

    Zou, Hua; Hu, Yifeng; Zhu, Xiaoqin; Zhang, Jianhao; Wang, Xusheng; Song, Zhitang

    2016-10-01

    In this work, (1- x)(K0.48Na0.52)(Nb0.95Sb0.05)O3- x - xEr0.5(Na0.82K0.18)0.5ZrO3 ( x = 0-0.05) ceramics were fabricated by solid-state reaction techniques. The rhombohedral-tetragonal (R-T) phase boundary of the ceramics was identified at 0.04 ≤ x, thus providing an opportunity to investigate the upconversion emission derived from the Er3+ ions at the R-T phase boundary. Under 980 nm laser excitation, the R-T phase ceramics exhibited a strong green emission. In addition, the fluorescence intensity ratios of green emissions at 530 nm and 550 nm were investigated in a temperature range of 180-510 K, and maximum sensing sensitivity was found to be 0.0037 K-1. The results indicate that Er3+-doped ceramics with R-T phase boundaries can be applied to new multifunctional electro-optical temperature sensors. Laser excitation heating effects were also observed in detail.

  9. Grain boundary void nucleation in astroloy produced by room temperature deformation and anneal

    Science.gov (United States)

    Saegusa, T.; Uemura, M.; Weertman, J. R.

    1980-08-01

    Dyson and co-workers have shown that the creep life of a nickel base superalloy can be greatly shortened if the material is strained at room temperature before the creep test is carried out. They found that a prestrain followed by a short annealing time produces small grain boundary cavities, and it is the presence of these prenucleated voids which so seriously degrades service life at elevated temperatures. The present work explores the relationship between microstructure and prestrain void nucleation. Samples of the nickel base superalloy astroloy were given various heat treatments which led to significantly different microstructures. It was found that voids resulting from a prestrain-anneal treatment form preferentially at the ends of carbides on grain boundaries oriented roughly parallel to the prestrain tensile axis or rolling direction. Void spacing in the various microstructures is proportional to (but larger than) carbide spacing. The growth of these cavities during annealing is attributed to the presence of tensile residual stresses arising from the difference in deformability between grain boundary regions and the relatively soft matrix.

  10. Boundary slip study on hydrophilic, hydrophobic, and superhydrophobic surfaces with dynamic atomic force microscopy.

    Science.gov (United States)

    Bhushan, Bharat; Wang, Yuliang; Maali, Abdelhamid

    2009-07-21

    Slip length has been measured using the dynamic atomic force microscopy (AFM) method. Unlike the contact AFM method, the sample surface approaches an oscillating sphere with a very low velocity in the dynamic AFM method. During this process, the amplitude and phase shift data are recorded to calculate the hydrodynamic damping coefficient, which is then used to obtain slip length. In this study, a glass sphere with a large radius was glued to the end of an AFM cantilever to measure the slip length on rough surfaces. Experimental results for hydrophilic, hydrophobic, and superhydrophobic surfaces show that the hydrodynamic damping coefficient decreases from the hydrophilic surface to the hydrophobic surface and from the hydrophobic one to the superhydrophobic one. The slip lengths obtained on the hydrophobic and superhydrophobic surfaces are 43 and 236 nm, respectively, which indicates increasing boundary slip from the hydrophobic surface to the superhydrophobic one.

  11. Temperature dependent droplet impact dynamics on flat and textured surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Azar Alizadeh; Vaibhav Bahadur; Sheng Zhong; Wen Shang; Ri Li; James Ruud; Masako Yamada; Liehi Ge; Ali Dhinojwala; Manohar S Sohal (047160)

    2012-03-01

    Droplet impact dynamics determines the performance of surfaces used in many applications such as anti-icing, condensation, boiling and heat transfer. We study impact dynamics of water droplets on surfaces with chemistry/texture ranging from hydrophilic to superhydrophobic and across a temperature range spanning below freezing to near boiling conditions. Droplet retraction shows very strong temperature dependence especially for hydrophilic surfaces; it is seen that lower substrate temperatures lead to lesser retraction. Physics-based analyses show that the increased viscosity associated with lower temperatures can explain the decreased retraction. The present findings serve to guide further studies of dynamic fluid-structure interaction at various temperatures.

  12. Nitrogen recombination on high-temperature reusable surface insulation and the analysis of its effect on surface catalysis

    Science.gov (United States)

    Kolodziej, Paul; Stewart, David A.

    1987-01-01

    The energy transfer catalytic recombination coefficients for nitrogen and oxygen on a borosilicate glass are determined in nitrogen and air hypersonic arc jet streams. These data, obtained from a reacting boundary-layer analysis with first-order surface reaction kinetics, compare well with earlier results from a Goulard frozen boundary-layer model up to 1600 K. The apparent surface recombination rates increase up to 1600 K, then begin to decrease. To illustrate the effects of temperature and nitrogen dissociation on energy transfer to the glass, a diffusional heat-flux is calculated using the present results from 1450 K up to 1850 K. This diffusional heat-flux is the contribution to the total heating rate by atom recombination, and is used to compare the present results with coefficients from three previous studies.

  13. The influence of temperature and grain boundary volume on the resistivity of nanocrystalline nickel

    Energy Technology Data Exchange (ETDEWEB)

    Darnbrough, J. E., E-mail: J.E.Darnbrough@bristol.ac.uk; Flewitt, P. E. J. [Interface Analysis Centre, School of Physics, University of Bristol, H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8 1TL (United Kingdom); Roebuck, B. [National Physical Laboratory, Hampton Rd, Teddington, Middlesex, TW11 0LW (United Kingdom)

    2015-11-14

    The thermal stability and modes of recrystallisation of nanocrystalline nickel has been observed through a conduction-based non-destructive test. Resistivity measurements have been utilised to quantify grain boundary volume fraction and microstructure. This observation makes clear the distinction of the factors that contribute to resistivity and demonstrates that these contributions are related to microstructure, either directly or in-directly. In static systems, the contribution of ordered grains and low-order grain boundary atomic arrangements in small grained material has been measured and correlated with resistivity. Measurements of in-situ resistivity conducted at high temperature gives changes with time which are related to grain growth, during heat treatment. This shows that resistivity can be used as a technique for observing the microstructure and grain growth of small grained material.

  14. The boundary layer over turbine blade models with realistic rough surfaces

    Science.gov (United States)

    McIlroy, Hugh M., Jr.

    The impact of turbine blade surface roughness on aerodynamic performance and heat loads is well known. Over time, as the turbine blades are exposed to heat loads, the external surfaces of the blades become rough. Also, for film-cooled blades, surface degradation can have a significant impact on film-cooling effectiveness. Many studies have been conducted on the effects of surface degradation/roughness on engine performance but most investigations have modeled the rough surfaces with uniform or two-dimensional roughness patterns. The objective of the present investigation is to conduct measurements that will reveal the influence of realistic surface roughness on the near-wall behavior of the boundary layer. Measurements have been conducted at the Matched-Index-of-Refraction (MIR) Facility at the Idaho National Engineering and Environmental Laboratory with a laser Doppler velocimeter. A flat plate model of a turbine blade has been developed that produces a transitional boundary layer, elevated freestream turbulence and an accelerating freestream in order to simulate conditions on the suction side of a high-pressure turbine blade. Boundary layer measurements have been completed over a smooth plate model and over a model with a strip of realistic rough surface. The realistic rough surface was developed by scaling actual turbine blade surface data that was provided by U.S. Air Force Research Laboratory. The results indicate that bypass transition occurred very early in the flow over the model and that the boundary layer remained unstable throughout the entire length of the test plate; the boundary layer thickness and momentum thickness Reynolds numbers increased over the rough patch; and the shape factor increased over the rough patch but then decreased downstream of the patch relative to the smooth plate case; in the rough patch case the flow experienced two transition reversals with laminar-like behavior achieved by the end of the test plate; streamwise turbulence

  15. Thalamocortical dynamics of the McCollough effect: boundary-surface alignment through perceptual learning.

    Science.gov (United States)

    Grossberg, Stephen; Hwang, Seungwoo; Mingolla, Ennio

    2002-05-01

    This article further develops the FACADE neural model of 3-D vision and figure-ground perception to quantitatively explain properties of the McCollough effect (ME). The model proposes that many ME data result from visual system mechanisms whose primary function is to adaptively align, through learning, boundary and surface representations that are positionally shifted due to the process of binocular fusion. For example, binocular boundary representations are shifted by binocular fusion relative to monocular surface representations, yet the boundaries must become positionally aligned with the surfaces to control binocular surface capture and filling-in. The model also includes perceptual reset mechanisms that use habituative transmitters in opponent processing circuits. Thus the model shows how ME data may arise from a combination of mechanisms that have a clear functional role in biological vision. Simulation results with a single set of parameters quantitatively fit data from 13 experiments that probe the nature of achromatic/chromatic and monocular/binocular interactions during induction of the ME. The model proposes how perceptual learning, opponent processing, and habituation at both monocular and binocular surface representations are involved, including early thalamocortical sites. In particular, it explains the anomalous ME utilizing these multiple processing sites. Alternative models of the ME are also summarized and compared with the present model.

  16. Accurate computation of surface stresses and forces with immersed boundary methods

    Science.gov (United States)

    Goza, Andres; Liska, Sebastian; Morley, Benjamin; Colonius, Tim

    2016-09-01

    Many immersed boundary methods solve for surface stresses that impose the velocity boundary conditions on an immersed body. These surface stresses may contain spurious oscillations that make them ill-suited for representing the physical surface stresses on the body. Moreover, these inaccurate stresses often lead to unphysical oscillations in the history of integrated surface forces such as the coefficient of lift. While the errors in the surface stresses and forces do not necessarily affect the convergence of the velocity field, it is desirable, especially in fluid-structure interaction problems, to obtain smooth and convergent stress distributions on the surface. To this end, we show that the equation for the surface stresses is an integral equation of the first kind whose ill-posedness is the source of spurious oscillations in the stresses. We also demonstrate that for sufficiently smooth delta functions, the oscillations may be filtered out to obtain physically accurate surface stresses. The filtering is applied as a post-processing procedure, so that the convergence of the velocity field is unaffected. We demonstrate the efficacy of the method by computing stresses and forces that converge to the physical stresses and forces for several test problems.

  17. Semi-analytical analysis of the response of the air temperature over the land surface to the global vegetation distribution

    Institute of Scientific and Technical Information of China (English)

    LIU Fei; CHAO JiPing

    2009-01-01

    Response of the air temperature over the land surface to the global vegetation distribution is investigated, using a three-dimensional governing equation to simulate the steady, large-scale, limited amplitude perturbation of the free, inviscid and adiabatic atmosphere. The adoption of the static equation leads to a temperature governing equation in the terrain following coordinate. With the prescribed temperature as the upper boundary condition and the radiation balance as the lower boundary condition, the semi-analytical solution of the global circulation temperature can be calculated. In this article, only the air temperature (at 2 m height) over the land surface is analyzed, and the result suggests that this model can simulate the air temperature pattern over the land surface reasonably. A better simulation occurs when a simple feedback of the albedo on the temperature is included. Two sensitivity experiments are analyzed through this model. One suggests that the air temperature over the land surface descends obviously when the land surface is covered with ice all over, while another suggests that the air temperature rises a little when the land surface is covered with forest except the ice-covered area. This model appears to be a good tool to study the response of the air temperature to the vegetation distribution. Limitations of the model are also discussed.

  18. An eigenfunction expansion method for the elastodynamic response of an elastic solid with mixed boundary surfaces

    Institute of Scientific and Technical Information of China (English)

    Liguo Tang; Jianchun Cheng

    2008-01-01

    The method of eigenfunction expansion is one of the most elegant methods for solving elastodynamic problems.The solution obtained from it is more concise than that obtained from the integral transform technique.Traditional eigenfunction expansion method is used for the elastodynamic problems with displacement and traction boundary conditions.In this paper,the method is generalized to study the elastodynamic response of an elastic solid with mixed boundary surfaces,and the exact analytical solution is derived.The dynamic response of a finite-length solid aluminum cylinder with two mixed end boundaries is numerically evaluated.The result com-puted from the analytical solution agrees very well with that obtained from finite element method(FEM).

  19. Boundary conditions at the ablative walls in two-temperature modelling of thermal plasmas with reactive working gas

    Science.gov (United States)

    Pekker, Leonid; Murphy, Anthony B.

    2016-09-01

    In this paper, we propose a new set of boundary conditions at ablative hot walls with thermionic electron emission for two-temperature thermal arc models in which the temperature of electrons can deviate from the temperature of heavy particles,~{{T}\\text{e}}\

  20. Estimation of Surface Heat Flux and Surface Temperature during Inverse Heat Conduction under Varying Spray Parameters and Sample Initial Temperature

    Directory of Open Access Journals (Sweden)

    Muhammad Aamir

    2014-01-01

    Full Text Available An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27 mm and thickness (mm 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2 MPa to 1.8 MPa, while sample initial temperature varied from 600°C to 900°C. Beck’s sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024 MW/m2 was estimated for a thickness of 8.5 mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8 MPa.

  1. Estimation of surface heat flux and surface temperature during inverse heat conduction under varying spray parameters and sample initial temperature.

    Science.gov (United States)

    Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong; Zubair, Muhammad

    2014-01-01

    An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27 mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2 MPa to 1.8 MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024 MW/m(2) was estimated for a thickness of 8.5 mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8 MPa.

  2. Long-term surface temperature modeling of Pluto

    Science.gov (United States)

    Earle, Alissa M.; Binzel, Richard P.; Young, Leslie A.; Stern, S. A.; Ennico, K.; Grundy, W.; Olkin, C. B.; Weaver, H. A.

    2017-05-01

    NASA's New Horizons' reconnaissance of the Pluto system has revealed at high resolution the striking albedo contrasts from polar to equatorial latitudes on Pluto, as well as the sharpness of boundaries for longitudinal variations. These contrasts suggest that Pluto must undergo dynamic evolution that drives the redistribution of volatiles. Using the New Horizons results as a template, we explore the surface temperature variations driven seasonally on Pluto considering multiple timescales. These timescales include the current orbit (248 years) as well as the timescales for obliquity precession (peak-to-peak amplitude of 23° over 3 million years) and regression of the orbital longitude of perihelion (3.7 million years). These orbital variations create epochs of ;Extreme Seasons; where one pole receives a short, relatively warm summer and long winter, while the other receives a much longer, but less intense summer and short winter. We use thermal modeling to build upon the long-term insolation history model described by Earle and Binzel (2015) and investigate how these seasons couple with Pluto's albedo contrasts to create temperature effects. From this study we find that a bright region at the equator, once established, can become a site for net deposition. We see the region informally known as Sputnik Planitia as an example of this, and find it will be able to perpetuate itself as an ;always available; cold trap, thus having the potential to survive on million year or substantially longer timescales. Meanwhile darker, low-albedo, regions near the equator will remain relative warm and generally not attract volatile deposition. We argue that the equatorial region is a ;preservation zone; for whatever albedo is seeded there. This offers insight as to why the equatorial band of Pluto displays the planet's greatest albedo contrasts.

  3. Boundary conditions on the plasma emitter surface in the presence of a particle counter flow: I. Ion emitter

    Energy Technology Data Exchange (ETDEWEB)

    Astrelin, V. T., E-mail: V.T.Astrelin@inp.nsk.su; Kotelnikov, I. A. [Russian Academy of Sciences, Budker Institute of Nuclear Physics, Siberian Branch (Russian Federation)

    2017-02-15

    Emission of positively charged ions from a plasma emitter irradiated by a counterpropagating electron beam is studied theoretically. A bipolar diode with a plasma emitter in which the ion temperature is lower than the electron temperature and the counter electron flow is extracted from the ion collector is calculated in the one-dimensional model. An analog of Bohm’s criterion for ion emission in the presence of a counterpropagating electron beam is derived. The limiting density of the counterpropagating beam in a bipolar diode operating in the space-charge-limited-emission regime is calculated. The full set of boundary conditions on the plasma emitter surface that are required for operation of the high-current optics module in numerical codes used to simulate charged particle sources is formulated.

  4. Kinetic effect of high energy ions on the temperature profile in the boundary plasma region

    Energy Technology Data Exchange (ETDEWEB)

    Ezumi, N., E-mail: ezumi@nagano-nct.ac.jp [Nagano National College of Technology, 716 Tokuma, Nagano 381-8550 (Japan); Hayashi, Y.; Todoroki, K. [Nagano National College of Technology, 716 Tokuma, Nagano 381-8550 (Japan); Okazaki, K. [Graduated School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Tanaka, H.; Masuzaki, S. [National Institute for Fusion Science, Toki 509-5292 (Japan); Ohno, N. [Graduated School of Engineering, Nagoya University, Nagoya 464-8603 (Japan)

    2013-07-15

    Importance of ion dynamics in the boundary region has been discussed with experimental results of ion temperature (T{sub i}) measurements in linear plasma devices and its analytical model. Radial profiles of T{sub i} have been measured by using an ion sensitive probe in the linear devices CTP-HC and NAGDIS-II. The experiments indicate that T{sub i} is growing radially. Analytical ion-mean-energy profiles based on the ion Larmor motion are qualitatively consistent with the experimental T{sub i} profiles. These results clarify that the higher energy ions exist in the outside region of plasma flux tube.

  5. Time and Space Resolved Wall Temperature Measurements during Nucleate Boiling with Constant Heat Flux Boundary Conditions

    Science.gov (United States)

    Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Yerramilli, Vamsee K.; Kim, Jungho

    2005-01-01

    The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work is to acquire time and space resolved temperature distributions under nucleate bubbles on a constant heat flux surface. This was performed using a microheater array with 100 micron resolution that allowed effectively simultaneous measurements of surface temperature while supplying a constant dissipative heat flux. This data is then correlated with high speed (> 1000Hz) visual recordings of the bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that a significant source of energy during bubble nucleation and initial growth is the superheated layer around the bubble. Bubble coalescence was not observed to decrease surface temperature as significantly as bubble departure from the surface. Since bubble departure is typically followed by a sharp increase in the heater surface temperature, it is surmised that the departing bubble effectively removes the superheated layer, allowing a high local heat transfer rate with the bulk fluid through transient conduction/micro-convection during rewetting.

  6. Exact Solutions of Chemically Reactive Solute Distribution in MHD Boundary Layer Flow over a Shrinking Surface

    Institute of Scientific and Technical Information of China (English)

    Chandaneswar Midya

    2012-01-01

    An analytical study of the distribution of a reactant solute undergoing a first-order chemical reaction in the boundary layer flow of an electrically conducting incompressible Buid over a linearly shrinking surface is presented. The Row is permeated by an externally applied magnetic Geld normal to the plane of the flow. The equations governing the Row and concentration Reid are reduced into a set of nonlinear ordinary differential equations using similarity variables. Closed form exact solutions of the reduced concentration equation are obtained for both prescribed power-law surface concentration (PSC) and power-law wall mass flux (PMF) as boundary conditions. The study reveals that the concentration over a shrinking sheet is signiRcantly different from that of a stretching surface. It s found that te solute boundary layer thickness is enhanced with the increasing values of the Schmidt number and the power-law index parameter, but decreases with enhanced vaJues of magnetic and reaction rate parameters for the PSC case. For the PMF case, the solute boundary layer thickness decreases with the increase of the Schmidt number, magnetic and reaction rate parameter for power-law index parameter n = 0. Negative solute boundary layer thickness is observed for the PMF case when n = 1 and 2, and these facts may not be realized in real-world applications.%An analytical study of the distribution of a reactant solute undergoing a first-order chemical reaction in the boundary layer flow of an electrically conducting incompressible fluid over a linearly shrinking surface is presented.The flow is permeated by an externally applied magnetic field normal to the plane of the flow.The equations governing the flow and concentration field are reduced into a set of nonlinear ordinary differential equations using similarity variables.Closed form exact solutions of the reduced concentration equation are obtained for both prescribed power-law surface concentration (PSC) and power-law wall

  7. Digital particle velocimetry technique for free-surface boundary layer measurements: Application to vortex pair interactions

    Energy Technology Data Exchange (ETDEWEB)

    Hirsa, A.H.; Vogel, M.J.; Gayton, J.D. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Mechanical Engineering

    2001-08-01

    A variation of the digital particle image velocimetry (DPIV) technique was developed for the measurement of velocity at a free surface for low Froude number flows. The two-step process involves first determining the location of the free surface in the digital images of the seeded flow using the fast Fourier transform-based method of surface elevation mapping (SEM), which takes advantage of total internal reflection at the interface. The boundary-fitted DPIV code positions the interrogation windows below the computed location of the interface to allow for extrapolation of interfacial velocities. This technique was designed specifically to handle large surface-parallel vorticity which can occur when the Reynolds number is large and surface-active materials are present. The SEM technique was verified on capillary-gravity waves and the full boundary-fitted DPIV technique was applied to the interaction of vortex pairs with a free surface covered by an insoluble monolayer. The local rise and fall of the free surface as well as the passage and return of a contamination front was clearly observed in the DPIV data. (orig.)

  8. Predicting monsoon rainfall and pressure indices from sea surface temperature

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.

    The relationship between the sea surface temperature (SST) in the Indian Ocean and monsoon rainfall has been examined by using 21 years data set (1967-87) of MOHSST.6 (Met. Office Historical Sea Surface Temperature data set, obtained from U.K. Met...

  9. Metal surface temperature induced by moving laser beams

    NARCIS (Netherlands)

    Römer, G.R.B.E.; Meijer, J.

    1995-01-01

    Whenever a metal is irradiated with a laser beam, electromagnetic energy is transformed into heat in a thin surface layer. The maximum surface temperature is the most important quantity which determines the processing result. Expressions for this maximum temperature are provided by the literature fo

  10. Recent trends in sea surface temperature off Mexico

    NARCIS (Netherlands)

    Lluch-Cota, S.E.; Tripp-Valdéz, M.; Lluch-Cota, D.B.; Lluch-Belda, D.; Verbesselt, J.; Herrera-Cervantes, H.; Bautista-Romero, J.

    2013-01-01

    Changes in global mean sea surface temperature may have potential negative implications for natural and socioeconomic systems; however, measurements to predict trends in different regions have been limited and sometimes contradictory. In this study, an assessment of sea surface temperature change si

  11. Recent trends in sea surface temperature off Mexico

    NARCIS (Netherlands)

    Lluch-Cota, S.E.; Tripp-Valdéz, M.; Lluch-Cota, D.B.; Lluch-Belda, D.; Verbesselt, J.; Herrera-Cervantes, H.; Bautista-Romero, J.

    2013-01-01

    Changes in global mean sea surface temperature may have potential negative implications for natural and socioeconomic systems; however, measurements to predict trends in different regions have been limited and sometimes contradictory. In this study, an assessment of sea surface temperature change

  12. Reintroducing radiometric surface temperature into the Penman-Monteith formulation

    DEFF Research Database (Denmark)

    Mallick, Kaniska; Bøgh, Eva; Trebs, Ivonne;

    2015-01-01

    Here we demonstrate a novel method to physically integrate radiometric surface temperature (TR) into the Penman-Monteith (PM) formulation for estimating the terrestrial sensible and latent heat fluxes (H and λE) in the framework of a modified Surface Temperature Initiated Closure (STIC). It combi...

  13. Interferometric measurements of sea surface temperature and emissivity

    Science.gov (United States)

    Fiedler, Lars; Bakan, Stephan

    1997-09-01

    A new multispectral method to derive sea surface emissivity and temperature by using interferometer measurements of the near surface upwelling radiation in the infrared window region is presented. As reflected sky radiation adds substantial spectral variability to the otherwise spectrally smooth surface radiation, an appropriate estimate of surface emissivity allows the measured upwelling radiation to be corrected for the reflected sky component. The remaining radiation, together with the estimated surface emissivity, yields an estimate of the sea surface temperature. Measurements from an ocean pier in the Baltic Sea in October 1995 indicate an accuracy of about 0.1 K for the sea surface temperature thus derived. A strong sea surface skin effect of about 0.6 K is found in that particular case.

  14. Evolution of grain boundary conduction with increasing temperature in pure and Ti doped Co ferrite materials

    Energy Technology Data Exchange (ETDEWEB)

    Vaithyanathan, V. [Research and Development Centre, Bharathiar University, Coimbatore-641 046 (India); Patro, L. N., E-mail: laxminar@chemie.uni-marburg.de, E-mail: kkamalabharathi@gmail.com [Department of Chemistry, Philips University of Marburg, 35032, Marburg (Germany); Kodam, Ugendar [Advanced Magnetic Materials Laboratory (AMMLa), Department of Physics, Indian Institute of Technology Madras, Chennai-600 036 (India); Tan, H. [Theiss Research, La Jolla, California 92037 (United States); Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Inbanathan, S. S. R. [Post Graduate and Research Department of Physics, The American College, Madurai-625002 (India); Kamala Bharathi, K., E-mail: laxminar@chemie.uni-marburg.de, E-mail: kkamalabharathi@gmail.com [Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742 (United States)

    2015-09-21

    We report on the structural, temperature, and frequency dependent impedance studies of Ti doped cobalt ferrite material (CoFe{sub 1.95}Ti{sub 0.05}O{sub 4}) in comparison with the pure CoFe{sub 2}O{sub 4}. XRD and Raman spectroscopy studies confirm the inverse spinel crystallization of the materials with space group of Fd-3 m. Scanning electron microscope images shows the microcrystalline nature of the particles. Homogeneity, stoichiometry, and ionic states of the ions in the composition were confirmed by energy dispersive X-ray analysis and X-ray photoelectron spectroscopic studies. Temperature and frequency dependent real (Z′) and imaginary (Z″) part of the impedance shows the existence of relaxation processes and their distribution in CoFe{sub 2}O{sub 4} and CoFe{sub 1.95}Ti{sub 0.05}O{sub 4} materials. Complex impedance spectroscopy studies at low temperatures shows that the conductivity in these materials is predominantly due to the intrinsic bulk grains. With increasing the temperature, evolution of grain boundary conduction is clearly seen through the appearance of a second semi-circle in the complex impedance plots. Room temperature total dc conductivity of both CoFe{sub 2}O{sub 4} and CoFe{sub 1.95}Ti{sub 0.05}O{sub 4} materials is found to be 5.78 × 10{sup −8} and 1.61 × 10{sup −7} S/cm, respectively. Temperature variation of dc electrical conductivity follows the Arrhenius relationship and the activation energies for CoFe{sub 2}O{sub 4} corresponding to grain (0.55 eV for CoFe{sub 2}O{sub 4}), grain boundary (0.52 eV), and total conduction (0.54 eV) are discussed. Observation of well distinguishable grain and grain boundary conductions and the low conductivity values in CoFe{sub 2}O{sub 4} and CoFe{sub 1.95}Ti{sub 0.05}O{sub 4} materials indicates that these materials are promising candidates for the high frequency applications.

  15. Age-surface temperature estimation model: When will oil palm plantation reach the same surface temperature as natural forest?

    Science.gov (United States)

    Rushayati, S. B.; Hermawan, R.; Meilani, R.

    2017-01-01

    Oil palm plantation has often been accused as the cause of global warming. However, along with its growth, it would be able to decrease surface temperature. The question is ‘when will the plantation be able to reach the same surface temperature as natural forest’. This research aimed to estimate the age of oil palm plantation that create similar surface temperature to those in natural forest (land cover before the opening and planting of oil palm). The method used in this research was spatial analysis of land cover and surface temperature distribution. Based on the spatial analysis of surface temperature, five points was randomly taken from each planting age (age 1 15 years). Linear regression was then employed in the analysis. The linear regression formula between surface temperature and age of oil palm plantation was Y = 26.002 – 0.1237X. Surface temperature will decrease as much as 0.1237 ° C with one year age growth oil palm. Surface temperature that was similar to the initial temperature, when the land cover was natural forest (23.04 °C), was estimated to occur when the oil palm plantation reach the age 24 year.

  16. The boundary-constraint method for constructing vortex-surface fields

    Science.gov (United States)

    Xiong, Shiying; Yang, Yue

    2016-11-01

    We develop a boundary-constraint method for constructing the vortex-surface field (VSF) in a three-dimensional fluid velocity field. The isosurface of VSF is a vortex surface consisting of vortex lines, which can be used to identify and track the evolution of vortical structures in a Lagrangian sense. The evolution equation with pseudo-time is solved under the boundary constraint of VSF to obtain an approximate solution of VSF. Using the boundary-constraint method, we construct the VSFs in Taylor-Green flow and transitional channel flow. The uniqueness of VSF are demonstrated with different initial conditions, and the consistency of this boundary-constraint method and the previous two-time approach for constructing VSF is discussed. In addition, the convergence error in the calculation of VSF is analyzed. This work has been supported in part by the National Natural Science Foundation of China (Grant Nos. 11522215 and 11521091), and the Thousand Young Talents Program of China.

  17. Using a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to Simulate the Interaction between Land Surface Processes and Atmospheric Boundary Layer in Semi-Arid Regions

    Institute of Scientific and Technical Information of China (English)

    刘树华; 乐旭; 胡非; 刘辉志

    2004-01-01

    This paper uses a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to study the interaction between land surface and atmospheric boundary layer processes. The scheme is composed of two main parts:atmospheric boundary layer processes and land surface processes. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feasibility of the model is well proved in this paper. The numerical simulation results from MSPAS show good agreement with reality. The scheme is used to obtain reasonable simulations for diurnal variations of heat balance, potential temperature of boundary layer, and wind field, and spatial distributions of temperature, specific humidity, vertical velocity,turbulence kinetic energy, and turbulence exchange coefficient over desert and oasis. In addition, MSPAS is used to simulate the interaction between desert and oasis at night, and again it obtains reasonable results.This indicates that MSPAS can be used to study the interaction between land surface processes and the atmospheric boundary layer over various underlying surfaces and can be extended for regional climate and numerical weather prediction study.

  18. Relationship between boundary misorientation angle and true strain during high temperature deformation of 7050 aluminum alloy

    Institute of Scientific and Technical Information of China (English)

    HU Hui-e; YANG Li; ZHEN Liang; SHAO Wen-zhu; ZHANG Bao-you

    2008-01-01

    Tensile tests of solid solution treated 7050 aluminum alloy were conducted to different strain degrees (0.1, 0.4, 0.6 and failure) at 460 ℃ with the strain rate of 1.0×10-4-1.0×10-1s-1. The boundary misorientation angle evolution during hot deformation of the 7050 aluminum alloy was studied by EBSD technique and the fracture surfaces were observed using SEM. A linear relationship between the increase in the average boundary misorientation angle and the true strain at different strain rates is assumed when aluminum alloy is deformed at 460 ℃. The increasing rate of average boundary misorientation angle is 15.1-, 15.7- and -0.75- corresponding to the strain rate of 1.0×10-4, 1.0×10-2 and 0.1 s-1, respectively. The main softening mechanism is continuous dynamic recrystallization when the strain rates are 1.0×10-4 and 1.0×10-2 s-1, and it is dynamic recovery when strain rate is 0.1 s-1.

  19. The groundwater-land-surface-atmosphere connection: soil moisture effects on the atmospheric boundary layer in fully-coupled simulations

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, R M; Chow, F K; Kollet, S J

    2007-02-02

    This study combines a variably-saturated groundwater flow model and a mesoscale atmospheric model to examine the effects of soil moisture heterogeneity on atmospheric boundary layer processes. This parallel, integrated model can represent spatial variations in land-surface forcing driven by three-dimensional (3D) atmospheric and subsurface components. The development of atmospheric flow is studied in a series of idealized test cases with different initial soil moisture distributions generated by an offline spin-up procedure or interpolated from a coarse-resolution dataset. These test cases are performed with both the fully-coupled model (which includes 3D groundwater flow and surface water routing) and the uncoupled atmospheric model. The effects of the different soil moisture initializations and lateral subsurface and surface water flow are seen in the differences in atmospheric evolution over a 36-hour period. The fully-coupled model maintains a realistic topographically-driven soil moisture distribution, while the uncoupled atmospheric model does not. Furthermore, the coupled model shows spatial and temporal correlations between surface and lower atmospheric variables and water table depth. These correlations are particularly strong during times when the land surface temperatures trigger shifts in wind behavior, such as during early morning surface heating.

  20. THE MECHANISM OF FRICTION BETWEEN SURFACES WITH REGULAR MICRO GROOVES UNDER BOUNDARY LUBRICATION

    Directory of Open Access Journals (Sweden)

    Mykhaylo Pashechko

    2012-12-01

    Full Text Available The results of researches related to the influence of partially regular microrelief parameters on the adhesion component of the friction factor under boundary lubrication have been given. A special ring-on tape test rig is proposed in order to avoid errors during running-in process. Special technique is used to form sinusoidal microgrooves what helped to create a partially regular microrelief on the surface with controlled contour and nominal contact areas. Fatigue and deformation components of wear process are considered. We proved that microtexturing with proposed parameters decreases the adhesion component of friction and reduces the probability of microwelding. It has been shown that under boundary friction micro grooves are effective on precision surfaces with low roughness when lack of film and probability of seizure appear.

  1. 2D-Manifold Boundary Surfaces Extraction from Heterogeneous Object on GPU

    Institute of Scientific and Technical Information of China (English)

    Ming Wang; Jie-Qing Feng

    2012-01-01

    The conventional isosurface techniques are not competent for meshing a heterogeneous object because they assume that the object is homogeneous.Thus the visualization method taking the heterogeneity into account is desired.In this paper,we propose a novel algorithm to extract the boundary surfaces from a heterogeneous object in one pass,whose remarkable advantage is free of the number of materials contained.The heterogeneous object is first classified into a series of homogeneous material components.Then each component is enclosed with a 2D-manifold boundary surface extracted via our algorithm.The information important to the heterogeneous object is also provided,such as the interface between two materials,the intersection curve where three materials meet and the intersection point where four materials meet.To improve the performance,the algorithm is also designed and implemented on GPU.Experimental results demonstrate the effectiveness and efficiency of the proposed algorithm.

  2. Guest editor - Material exchanges at marine boundaries and surface ocean processes: Forcings and feedbacks

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.

    -1 Special section on: Material exchanges at marine boundaries and surface ocean processes: Forcings and feedbacks Preface Exchanges across marine interfaces are important in global material cycles and in the modification of atmospheric composition. Climate... and feedbacks was held during the 2nd Annual Meeting of the Asia?Oceania Geosciences Society (AOGS) in Singapore during 20?24 June 2005. The following Special section contains some of the papers presented at that session. The first article by Sarma addresses...

  3. A novel perovskite oxide chemically designed to show multiferroic phase boundary with room-temperature magnetoelectricity

    Science.gov (United States)

    Fernández-Posada, Carmen M.; Castro, Alicia; Kiat, Jean-Michel; Porcher, Florence; Peña, Octavio; Algueró, Miguel; Amorín, Harvey

    2016-09-01

    There is a growing activity in the search of novel single-phase multiferroics that could finally provide distinctive magnetoelectric responses at room temperature, for they would enable a range of potentially disruptive technologies, making use of the ability of controlling polarization with a magnetic field or magnetism with an electric one (for example, voltage-tunable spintronic devices, uncooled magnetic sensors and the long-searched magnetoelectric memory). A very promising novel material concept could be to make use of phase-change phenomena at structural instabilities of a multiferroic state. Indeed, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of the perovskite BiFeO3-BiCoO3 solid solution, specifically at its morphotropic phase boundary between multiferroic polymorphs of rhombohedral and tetragonal symmetries. Here, we report a novel perovskite oxide that belongs to the BiFeO3-BiMnO3-PbTiO3 ternary system, chemically designed to present such multiferroic phase boundary with enhanced ferroelectricity and canted ferromagnetism, which shows distinctive room-temperature magnetoelectric responses.

  4. Arctic surface temperatures from Metop AVHRR compared to in situ ocean and land data

    Directory of Open Access Journals (Sweden)

    G. Dybkjær

    2012-11-01

    Full Text Available The ice surface temperature (IST is an important boundary condition for both atmospheric and ocean and sea ice models and for coupled systems. An operational ice surface temperature product using satellite Metop AVHRR infra-red data was developed for MyOcean. The IST can be mapped in clear sky regions using a split window algorithm specially tuned for sea ice. Clear sky conditions prevail during spring in the Arctic, while persistent cloud cover limits data coverage during summer. The cloud covered regions are detected using the EUMETSAT cloud mask. The Metop IST compares to 2 m temperature at the Greenland ice cap Summit within STD error of 3.14 °C and to Arctic drifting buoy temperature data within STD error of 3.69 °C. A case study reveals that the in situ radiometer data versus satellite IST STD error can be much lower (0.73 °C and that the different in situ measurements complicate the validation. Differences and variability between Metop IST and in situ data are analysed and discussed. An inter-comparison of Metop IST, numerical weather prediction temperatures and in situ observation indicates large biases between the different quantities. Because of the scarcity of conventional surface temperature or surface air temperature data in the Arctic, the satellite IST data with its relatively good coverage can potentially add valuable information to model analysis for the Arctic atmosphere.

  5. Arctic surface temperatures from Metop AVHRR compared to in situ ocean and land data

    Directory of Open Access Journals (Sweden)

    G. Dybkjær

    2012-03-01

    Full Text Available The ice surface temperature (IST is an important boundary condition for both atmospheric and ocean and sea ice models and for coupled systems. An operational ice surface temperature product using satellite Metop AVHRR infra-red data was developed for MyOcean. The IST can be mapped in clear sky regions using a split window algorithm specially tuned for sea ice. Clear sky conditions are prevailing during spring in the Arctic while persistent cloud cover limits data coverage during summer. The cloud covered regions are detected using the EUMETSAT cloud mask. The Metop IST compares to 2 m temperature at the Greenland ice cap Summit within STD error of 3.14 °C and to Arctic drifting buoy temperature data within STD error of 3.69 °C. A case study reveal that the in situ radiometer data versus satellite IST STD error can be much lower (0.73 °C and that the different in situ measures complicates the validation. Differences and variability between Metop IST and in situ data are analysed and discussed. An inter-comparison of Metop IST, numerical weather prediction temperatures and in situ observation indicates large biases between the different quantities. Because of the scarcity of conventional surface temperature or surface air temperature data in the Arctic the satellite IST data with its relatively good coverage can potentially add valuable information to model analysis for the Arctic atmosphere.

  6. Receptivity of the Boundary Layer to Vibrations of the Wing Surface

    Science.gov (United States)

    Bernots, Tomass; Ruban, Anatoly; Pryce, David; Laminar Flow Control UK Group Team

    2014-11-01

    In this work we study generation of Tollmien-Schlichting (T-S) waves in the boundary layer due to elastic vibrations of the wing surface. The flow is investigated based on the asymptotic analysis of the Navier-Stokes equations at large values of the Reynolds number. It is assumed that in the spectrum of the wing vibrations there is a harmonic which comes in resonance with the T-S wave on the lower branch of the stability curve. It was found that the vibrations of the wing surface produce pressure perturbations in the flow outside the boundary layer which can be calculated with the help of the piston theory. As the pressure perturbations penetrate into the boundary layer, a Stokes layer forms on the wing surface which appears to be influenced significantly by the compressibility of the flow, and is incapable of producing the T-S waves. The situation changes when the Stokes layer encounters an roughness; near which the flow is described using the triple-deck theory. The solution of the triple-deck problem can be found in an analytic form. Our main concern is with the flow behaviour downstream of the roughness and, in particular, with the amplitude of the generated Tollmien-Schlichting waves. This research was performed in the Laminar Flow Control Centre (LFC-UK) at Imperial College London. The centre is supported by EPSRC, Airbus UK and EADS Innovation Works.

  7. Ground surface temperature and humidity, ground temperature cycles and the ice table depths in University Valley, McMurdo Dry Valleys of Antarctica

    Science.gov (United States)

    Fisher, David A.; Lacelle, Denis; Pollard, Wayne; Davila, Alfonso; McKay, Christopher P.

    2016-11-01

    In the upper McMurdo Dry Valleys, 90% of the measured ice table depths range from 0 to 80 cm; however, numerical models predict that the ice table is not in equilibrium with current climate conditions and should be deeper than measured. This study explored the effects of boundary conditions (air versus ground surface temperature and humidity), ground temperature cycles, and their diminishing amplitude with depth and advective flows (Darcy flow and wind pumping) on water vapor fluxes in soils and ice table depths using the REGO vapor diffusion model. We conducted a series of numerical experiments that illustrated different hypothetical scenarios and estimated the water vapor flux and ice table depth using the conditions in University Valley, a small high elevation valley. In situ measurements showed that while the mean annual ground surface temperature approximates that in the air, the mean annual ground surface relative humidity (>85%ice) was significantly higher than in the atmosphere ( 50%ice). When ground surface temperature and humidity were used as boundary conditions, along with damping diurnal and annual temperature cycles within the sandy soil, REGO predicted that measured ice table depths in the valley were in equilibrium with contemporary conditions. Based on model results, a dry soil column can become saturated with ice within centuries. Overall, the results from the new soil data and modeling have implications regarding the factors and boundary conditions that affect the stability of ground ice in cold and hyperarid regions where liquid water is rare.

  8. Nonlinear Nanofluid Flow over Heated Vertical Surface with Sinusoidal Wall Temperature Variations

    Directory of Open Access Journals (Sweden)

    S. S. Motsa

    2014-01-01

    Full Text Available The nonlinear density temperature variations in two-dimensional nanofluid flow over heated vertical surface with a sinusoidal wall temperature are investigated. The model includes the effects of Brownian motion and thermophoresis. Using the boundary layer approximation, the two-dimensional momentum, heat, and mass transfer equations are transferred to nonlinear partial differential equations form and solved numerically using a new method called spectral local linearisation method. The effects of the governing parameters on the fluid properties and on the heat and nanomass transfer coefficients are determined and shown graphically.

  9. Wind tunnel experiment of drag of isolated tree models in surface boundary layer

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    For very sparse tree land individual tree was the basic element of interaction between atmosphere and the surface. Drag of isolated tree was preliminary aerodynamic index for analyzing the atmospheric boundary layer of this kind of surface. A simple pendulum method was designed and carried out in wind tunnel to measure drag of isolated tree models according to balance law of moment of force. The method was easy to conduct and with small error. The results showed that the drag and drag coefficient of isolated tree increased with decreasing of its permeability or porosity. Relationship between drag coefficient and permeability of isolated tree empirically was expressed by quadric curve.

  10. Sustained drag reduction in a turbulent flow using a low-temperature Leidenfrost surface

    Science.gov (United States)

    Saranadhi, Dhananjai; Chen, Dayong; Kleingartner, Justin A.; Srinivasan, Siddarth; Cohen, Robert E.; McKinley, Gareth H.

    2016-01-01

    Skin friction drag contributes a major portion of the total drag for small and large water vehicles at high Reynolds number (Re). One emerging approach to reducing drag is to use superhydrophobic surfaces to promote slip boundary conditions. However, the air layer or “plastron” trapped on submerged superhydrophobic surfaces often diminishes quickly under hydrostatic pressure and/or turbulent pressure fluctuations. We use active heating on a superhydrophobic surface to establish a stable vapor layer or “Leidenfrost” state at a relatively low superheat temperature. The continuous film of water vapor lubricates the interface, and the resulting slip boundary condition leads to skin friction drag reduction on the inner rotor of a custom Taylor-Couette apparatus. We find that skin friction can be reduced by 80 to 90% relative to an unheated superhydrophobic surface for Re in the range 26,100 ≤ Re ≤ 52,000. We derive a boundary layer and slip theory to describe the hydrodynamics in the system and show that the plastron thickness is h = 44 ± 11 μm, in agreement with expectations for a Leidenfrost surface. PMID:27757417

  11. Evaluation of MODIS Land Surface Temperature with In Situ Snow Surface Temperature from CREST-SAFE

    Science.gov (United States)

    Perez Diaz, C. L.; Lakhankar, T.; Romanov, P.; Munoz, J.; Khanbilvardi, R.; Yu, Y.

    2016-12-01

    This paper presents the procedure and results of a temperature-based validation approach for the Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) product provided by the National Aeronautics and Space Administration (NASA) Terra and Aqua Earth Observing System satellites using in situ LST observations recorded at the Cooperative Remote Sensing Science and Technology Center - Snow Analysis and Field Experiment (CREST-SAFE) during the years of 2013 (January-April) and 2014 (February-April). A total of 314 day and night clear-sky thermal images, acquired by the Terra and Aqua satellites, were processed and compared to ground-truth data from CREST-SAFE with a frequency of one measurement every 3 min. Additionally, this investigation incorporated supplementary analyses using meteorological CREST-SAFE in situ variables (i.e. wind speed, cloud cover, incoming solar radiation) to study their effects on in situ snow surface temperature (T-skin) and T-air. Furthermore, a single pixel (1km2) and several spatially averaged pixels were used for satellite LST validation by increasing the MODIS window size to 5x5, 9x9, and 25x25 windows for comparison. Several trends in the MODIS LST data were observed, including the underestimation of daytime values and nighttime values. Results indicate that, although all the data sets (Terra and Aqua, diurnal and nocturnal) showed high correlation with ground measurements, day values yielded slightly higher accuracy ( 1°C), both suggesting that MODIS LST retrievals are reliable for similar land cover classes and atmospheric conditions. Results from the CREST-SAFE in situ variables' analyses indicate that T-air is commonly higher than T-skin, and that a lack of cloud cover results in: lower T-skin and higher T-air minus T-skin difference (T-diff). Additionally, the study revealed that T-diff is inversely proportional to cloud cover, wind speed, and incoming solar radiation. Increasing the MODIS window size

  12. Estimation of minimum surface temperature at stage ll (Short Communication

    Directory of Open Access Journals (Sweden)

    A. P. Dimri

    2001-04-01

    Full Text Available Forecasting minimum surface temperature at a station, Stage II, located in mountainous region requires information on the meteorological fields. An attempt has been made to develop a statistical model for forecasting minimum temperature at ground level using previous years' data. Surface data were collected at StageII (longitude 73 oB, latitude 34 oN, and altitude 2650 m. Atmospheric variables are influenced by complex orography and surface features to a great extent. In the present study, statistical relationship between atmosphere parameters and minimum temperature at the site has been established. Multivariate linear regression analysis has been used to establish the relationship to predict the minimum surface temperature for the following day. A comparison between the observed and the calculated forecast minimum temperature has been made. Most of the cases are well predicted (multiple correlation coefficient of 0.94.

  13. Investigating the Impact of Surface Heterogeneity on the Convective Boundary Layer Over Urban Areas Through Coupled Large-Eddy Simulation and Remote Sensing

    Science.gov (United States)

    Dominguez, Anthony; Kleissl, Jan P.; Luvall, Jeffrey C.

    2011-01-01

    Large-eddy Simulation (LES) was used to study convective boundary layer (CBL) flow through suburban regions with both large and small scale heterogeneities in surface temperature. Constant remotely sensed surface temperatures were applied at the surface boundary at resolutions of 10 m, 90 m, 200 m, and 1 km. Increasing the surface resolution from 1 km to 200 m had the most significant impact on the mean and turbulent flow characteristics as the larger scale heterogeneities became resolved. While previous studies concluded that scales of heterogeneity much smaller than the CBL inversion height have little impact on the CBL characteristics, we found that further increasing the surface resolution (resolving smaller scale heterogeneities) results in an increase in mean surface heat flux, thermal blending height, and potential temperature profile. The results of this study will help to better inform sub-grid parameterization for meso-scale meteorological models. The simulation tool developed through this study (combining LES and high resolution remotely sensed surface conditions) is a significant step towards future studies on the micro-scale meteorology in urban areas.

  14. North American regional climate reconstruction from ground surface temperature histories

    Science.gov (United States)

    Jaume-Santero, Fernando; Pickler, Carolyne; Beltrami, Hugo; Mareschal, Jean-Claude

    2016-12-01

    Within the framework of the PAGES NAm2k project, 510 North American borehole temperature-depth profiles were analyzed to infer recent climate changes. To facilitate comparisons and to study the same time period, the profiles were truncated at 300 m. Ground surface temperature histories for the last 500 years were obtained for a model describing temperature changes at the surface for several climate-differentiated regions in North America. The evaluation of the model is done by inversion of temperature perturbations using singular value decomposition and its solutions are assessed using a Monte Carlo approach. The results within 95 % confidence interval suggest a warming between 1.0 and 2.5 K during the last two centuries. A regional analysis, composed of mean temperature changes over the last 500 years and geographical maps of ground surface temperatures, show that all regions experienced warming, but this warming is not spatially uniform and is more marked in northern regions.

  15. The Sensitivity of African Easterly Waves to Eastern Tropical Atlantic Sea-Surface Temperatures

    Science.gov (United States)

    Druyan, Leonard M.; Fulakeza, Matthew

    2011-01-01

    The results of two regional atmospheric model simulations are compared to assess the influence of the eastern tropical Atlantic sea-surface temperature maximum on local precipitation, transient easterly waves and the West African summer monsoon. Both model simulations were initialized with reanalysis 2 data (US National Center for Environmental Prediction and Department of Energy) on 15 May 2006 and extended through 6 October 2006, forced by synchronous reanalysis 2 lateral boundary conditions introduced four times daily. One simulation uses 2006 reanalysis 2 sea-surface temperatures, also updated four times daily, while the second simulation considers ocean forcing absent the sea-surface temperature maximum, achieved here by subtracting 3 K at every ocean grid point between 0 and 15 N during the entire simulation. The simulation with 2006 sea-surface temperature forcing produces a realistic distribution of June-September mean precipitation and realistic westward propagating swaths of maximum rainfall, based on validation against Tropical Rainfall Measuring Mission (TRMM) estimates. The simulation without the sea-surface temperature maximum produces only 57% of the control June-September total precipitation over the eastern tropical Atlantic and about 83% of the Sahel precipitation. The simulation with warmer ocean temperatures generates generally stronger circulation, which in turn enhances precipitation by increasing moisture convergence. Some local precipitation enhancement is also attributed to lower vertical thermal stability above the warm water. The study shows that the eastern tropical Atlantic sea-surface temperature maximum enhances the strength of transient easterly waves and broadens the spatial extent of associated precipitation. However, large-scale circulation and its interaction with the African continent, and not sea-surface temperatures, control the timing and trajectories of the waves.

  16. Fluid-structure interaction of turbulent boundary layer over a compliant surface

    Science.gov (United States)

    Anantharamu, Sreevatsa; Mahesh, Krishnan

    2016-11-01

    Turbulent flows induce unsteady loads on surfaces in contact with them, which affect material stresses, surface vibrations and far-field acoustics. We are developing a numerical methodology to study the coupled interaction of a turbulent boundary layer with the underlying surface. The surface is modeled as a linear elastic solid, while the fluid follows the spatially filtered incompressible Navier-Stokes equations. An incompressible Large Eddy Simulation finite volume flow approach based on the algorithm of Mahesh et al. is used in the fluid domain. The discrete kinetic energy conserving property of the method ensures robustness at high Reynolds number. The linear elastic model in the solid domain is integrated in space using finite element method and in time using the Newmark time integration method. The fluid and solid domain solvers are coupled using both weak and strong coupling methods. Details of the algorithm, validation, and relevant results will be presented. This work is supported by NSWCCD, ONR.

  17. Ground-based measurement of surface temperature and thermal emissivity

    Science.gov (United States)

    Owe, M.; Van De Griend, A. A.

    1994-01-01

    Motorized cable systems for transporting infrared thermometers have been used successfully during several international field campaigns. Systems may be configured with as many as four thermal sensors up to 9 m above the surface, and traverse a 30 m transect. Ground and canopy temperatures are important for solving the surface energy balance. The spatial variability of surface temperature is often great, so that averaged point measurements result in highly inaccurate areal estimates. The cable systems are ideal for quantifying both temporal and spatial variabilities. Thermal emissivity is also necessary for deriving the absolute physical temperature, and measurements may be made with a portable measuring box.

  18. Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

    Directory of Open Access Journals (Sweden)

    W. Choi

    2010-11-01

    Full Text Available In this study the atmospheric boundary layer (ABL height (zi over complex, forested terrain is estimated based on the power spectra and the integral length scale of horizontal winds obtained from a three-axis sonic anemometer during the BEARPEX (Biosphere Effects on Aerosol and Photochemistry Experiment. The zi values estimated with this technique showed very good agreement with observations obtained from balloon tether sonde (2007 and rawinsonde (2009 measurements under unstable conditions (z/L < 0 at the coniferous forest in the California Sierra Nevada. The behavior of the nocturnal boundary layer height (h and power spectra of lateral winds and temperature under stable conditions (z/L > 0 is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007, although it was observed to only vary from 60–80 m during the experiment. Finally, significant directional wind shear was observed during both day and night with winds backing from the prevailing west-southwesterlies in the ABL (anabatic cross-valley circulation to consistent southerlies in a layer ~1 km thick just above the ABL before veering to the prevailing westerlies further aloft. We show that this is consistent with the forcing of a thermal wind driven by the regional temperature gradient directed due east in the lower troposphere.

  19. Effect of milling temperatures on surface area, surface energy and cohesion of pharmaceutical powders.

    Science.gov (United States)

    Shah, Umang V; Wang, Zihua; Olusanmi, Dolapo; Narang, Ajit S; Hussain, Munir A; Tobyn, Michael J; Heng, Jerry Y Y

    2015-11-10

    Particle bulk and surface properties are influenced by the powder processing routes. This study demonstrates the effect of milling temperatures on the particle surface properties, particularly surface energy and surface area, and ultimately on powder cohesion. An active pharmaceutical ingredient (API) of industrial relevance (brivanib alaninate, BA) was used to demonstrate the effect of two different, but most commonly used milling temperatures (cryogenic vs. ambient). The surface energy of powders milled at both cryogenic and room temperatures increased with increasing milling cycles. The increase in surface energy could be related to the generation of surface amorphous regions. Cohesion for both cryogenic and room temperature milled powders was measured and found to increase with increasing milling cycles. For cryogenic milling, BA had a surface area ∼ 5× higher than the one obtained at room temperature. This was due to the brittle nature of this compound at cryogenic temperature. By decoupling average contributions of surface area and surface energy on cohesion by salinization post-milling, the average contribution of surface energy on cohesion for powders milled at room temperature was 83% and 55% at cryogenic temperature.

  20. TEMPERATURE CONTROL CIRCUIT FOR SURFACE ACOUSTIC WAVE (SAW RESONATORS

    Directory of Open Access Journals (Sweden)

    Zainab Mohamad Ashari

    2011-10-01

    Full Text Available Surface Acoustic Wave (SAW resonators are key components in oscillators, frequency synthesizers and transceivers. One of the drawbacks of SAW resonators are that its piezoelectric substrates are highly sensitive to ambient temperature resulting in performance degradation. This work propose a simple circuit design which stabalizes the temperature of the SAW resonator, making it independet of temperature change. This circuit is based on the oven control method which elevates the temperature of the resonator to a high temperature, making it tolerant to minor changes in ambient temperature.This circuit consist of a temperature sensor, heaters and a comparator which turn the heater on or off depending on the ambient temperature. Several SAW resonator were tested using this circuit. Experimental results indicate the temperature coefficient of frequency (TCF decreases from maximum of 130.44/°C to a minimum of -1.11/°C. 

  1. Turbulent dusty boundary layer in an ANFO surface-burst explosion

    Science.gov (United States)

    Kuhl, A. L.; Ferguson, R. E.; Chien, K. Y.; Collins, J. P.

    1992-01-01

    This paper describes the results of numerical simulations of the dusty, turbulent boundary layer created by a surface burst explosion. The blast wave was generated by the detonation of a 600-T hemisphere of ANFO, similar to those used in large-scale field tests. The surface was assumed to be ideally noncratering but contained an initial loose layer of dust. The dust-air mixture in this fluidized bed was modeled as a dense gas (i.e., an equilibrium model, valid for very small-diameter dust particles). The evolution of the flow was calculated by a high-order Godunov code that solves the nonsteady conservation laws. Shock interactions with dense layer generated vorticity near the wall, a result that is similar to viscous, no-slip effects found in clean flows. The resulting wall shear layer was unstable, and rolled up into large-scale rotational structures. These structures entrained dense material from the wall layer and created a chaotically striated flow. The boundary layer grew due to merging of the large-scale structures and due to local entrainment of the dense material from the fluidized bed. The chaotic flow was averaged along similarity lines (i.e., lines of constant values of x = r/Rs and y = z/Rs where R(sub s) = ct(exp alpha)) to establish the mean-flow profiles and the r.m.s. fluctuating-flow profiles of the boundary layer.

  2. Observation of distinct, temperature dependent flux noise near bicrystal grain boundaries in YBa2Cu3O7-x films

    DEFF Research Database (Denmark)

    Bukh, K. R.; Jacobsen, Claus Schelde; Hansen, Jørn Bindslev

    2000-01-01

    The characteristics of the magnetic flux noise in high temperature superconducting thin-films of yttrium-barium-copper-oxide (YBa2Cu3O7) in the vicinity of artificial grain boundaries have been studied by means of a low critical temperature superconducting quantum interference device (SQUID...

  3. Surface Tension of Methanol as a Function of cut-off Radius and Temperature Controllers

    Science.gov (United States)

    Obeidat, Abdalla; Jaradat, Adnan; Hamdan, Bushra

    Molecular dynamics is used to calculate the surface tension of van Leeuwen methanol. The van Leeuwen model of methanol is chosen over other models of methanol, since this model is widely used to study nucleation at low temperature. Usually, scientists use the cut-off radius to be three order of magnitude of segment diameter. In this study, we varied the cut-off radius to estimate the best cut-off at which the surface tension reaches its plateau. After deciding the best cut-off radius for van der Waals and Coulomb interactions (CUT-OFF and PME were used for Coulomb interaction), we varied the temperature controller (van-Housen, Berendsen, and v-rescale) to decide the best temperature controller to be used to study methanol. In all simulations, Gromacs is used at T =200-300K with periodic boundary conditions in all dimensions. JUST.

  4. Finite-temperature Casimir pistons for an electromagnetic field with mixed boundary conditions and its classical limit

    Energy Technology Data Exchange (ETDEWEB)

    Teo, L P [Faculty of Information Technology, Multimedia University, Jalan Multimedia, Cyberjaya, 63100, Selangor Darul Ehsan (Malaysia)], E-mail: lpteo@mmu.edu.my

    2009-03-13

    In this paper, the finite-temperature Casimir force acting on a two-dimensional Casimir piston due to an electromagnetic field is computed. It was found that if mixed boundary conditions are assumed on the piston and its opposite wall, then the Casimir force always tends to restore the piston toward the equilibrium position, regardless of the boundary conditions assumed on the walls transverse to the piston. In contrast, if pure boundary conditions are assumed on the piston and the opposite wall, then the Casimir force always tends to pull the piston toward the closer wall and away from the equilibrium position. The nature of the force is not affected by temperature. However, in the high-temperature regime, the magnitude of the Casimir force grows linearly with respect to temperature. This shows that the Casimir effect has a classical limit as has been observed in other literature.

  5. Ultra-fast grain boundary diffusion and its contribution to surface segregation on a martensitic steel. Experiments and modeling

    Science.gov (United States)

    Christien, F.; Le Gall, R.

    2011-09-01

    Phosphorus surface segregation was measured by Auger Electron Spectroscopy on a 17-4 PH martensitic stainless steel at 450, 550 and 600 °C. Surface segregation was shown to be much faster than expected which was attributed to a high contribution of phosphorus diffusion along the former austenitic grain boundaries. A model of surface segregation was developed following the Darken-du Plessis approach and taking account of both bulk and grain boundary solute diffusion. The phosphorus grain boundary diffusion coefficient in 17-4 PH was estimated: DGB17-4 PH steel than in α-iron.

  6. Spectral simulation of thermocapillary convection with a deformable free surface using boundary-fitted coordinates

    Science.gov (United States)

    Ahmed, Ikramuddin

    A Chebyshev-spectral collocation scheme has been developed to simulate thermocapillary convection processes in a differentially heated cavity with and without buoyancy effects. The time-dependent Navier- Stokes equations in primitive variables were solved with a semi-implicit scheme using the influence matrix technique. The deformable free surface was incorporated by means of a boundary-fitted coordinate (BFC) system. The BFC grid was generated by solving a system of elliptic equations. An iterative scheme based on finite difference methods was found to be sufficient for calculating a smooth distribution of grid-points for relatively low degrees of deformation of the free surface. The metrics of transformation, however, were calculated spectrally in order to achieve a high order of accuracy in the a posteriori mapping of the physical grid to the computational grid. The overall scheme was found to be efficient, economical, and capable of resolving the complex hydrodynamic and thermal structures in thermocapillarity driven flows with deformable free surfaces. The scheme was also modified to study problems with very high Marangoni numbers and non-deformable free surfaces, and later extended to three dimensions with periodic boundary conditions in order to explore the transitions to fully three dimensional phenomena that are anticipated in industrially relevant flow configurations.

  7. Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

    Directory of Open Access Journals (Sweden)

    W. Choi

    2011-07-01

    Full Text Available The atmospheric boundary layer (ABL height (zi over complex, forested terrain is estimated based on the power spectra and the integral length scale of cross-stream winds obtained from a three-axis sonic anemometer during the two summers of the BEARPEX (Biosphere Effects on Aerosol and Photochemistry Experiment. The zi values estimated with this technique show very good agreement with observations obtained from balloon tether sondes (2007 and rawinsondes (2009 under unstable conditions (z/L < 0 at the coniferous forest in the California Sierra Nevada. On the other hand, the low frequency behavior of the streamwise upslope winds did not exhibit significant variations and was therefore not useful in predicting boundary layer height. The behavior of the nocturnal boundary layer height (h with respect to the power spectra of the v-wind component and temperature under stable conditions (z/L > 0 is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007, although it was observed to only vary from 60–80 m during the 2009 experiment in which it was measured. Finally, significant directional wind shear was observed during both day and night soundings. The winds were found to be consistently backing from the prevailing west-southwesterlies within the ABL (the anabatic cross-valley circulation to southerlies in a layer ~1–2 km thick just above the ABL before veering to the prevailing westerlies further aloft. This shear pattern is shown to be consistent with the forcing of a thermal wind driven by the regional temperature gradient directed east-southeast in the lower troposphere.

  8. Mapping the body surface temperature of cattle by infrared thermography.

    Science.gov (United States)

    Salles, Marcia Saladini Vieira; da Silva, Suelen Corrêa; Salles, Fernando André; Roma, Luiz Carlos; El Faro, Lenira; Bustos Mac Lean, Priscilla Ayleen; Lins de Oliveira, Celso Eduardo; Martello, Luciane Silva

    2016-12-01

    Infrared thermography (IRT) is an alternative non-invasive method that has been studied as a tool for identifying many physiological and pathological processes related to changes in body temperature. The objective of the present study was to evaluate the body surface temperature of Jersey dairy cattle in a thermoneutral environment in order to contribute to the determination of a body surface temperature pattern for animals of this breed in a situation of thermal comfort. Twenty-four Jersey heifers were used over a period of 35 days at APTA Brazil. Measurements were performed on all animals, starting with the physiological parameters. Body surface temperature was measured by IRT collecting images in different body regions: left and right eye area, right and left eye, caudal left foreleg, cranial left foreleg, right and left flank, and forehead. High correlations were observed between temperature and humidity index (THI) and right flank, left flank and forehead temperatures (0.85, 0.81, and 0.81, respectively). The IRT variables that exhibited the five highest correlation coefficients in principal component 1 were, in decreasing order: forehead (0.90), right flank (0.87), left flank (0.84), marker 1 caudal left foreleg (0.83), marker 2 caudal left foreleg (0.74). The THI showed a high correlation coefficient (0.88) and moderate to low correlations were observed for the physiological variables rectal temperature (0.43), and respiratory frequency (0.42). The thermal profile obtained indicates a surface temperature pattern for each region studied in a situation of thermal comfort and may contribute to studies investigating body surface temperature. Among the body regions studied, IRT forehead temperature showed the highest association with rectal temperature, and forehead and right and left flank temperatures are strongly associated with THI and may be adopted in future studies on thermoregulation and body heat production.

  9. eMODIS Global Land Surface Temperature Version 6

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The EROS Moderate Resolution Imaging Spectroradiometer (eMODIS) Aqua Land Surface Temperature (LST) product is similar to the Land Processes Distributed Active...

  10. 2002 Average Monthly Sea Surface Temperature for California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA/ NASA AVHRR Oceans Pathfinder sea surface temperature data are derived from the 5-channel Advanced Very High Resolution Radiometers (AVHRR) on board the...

  11. 2003 Average Monthly Sea Surface Temperature for California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA/ NASA AVHRR Oceans Pathfinder sea surface temperature data are derived from the 5-channel Advanced Very High Resolution Radiometers (AVHRR) on board the...

  12. Sea surface temperature anomalies in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.

    . Further analysis has shown that the sea surface anomalies are well correlated to the anomalies of air temperature and latent heat flux values; whereas they are least correlated to the anomalies of wind stress and net radiation values, except over...

  13. An Estimation of Land Surface Temperatures from Landsat ETM+ ...

    African Journals Online (AJOL)

    Dr-Adeline

    2 National Authority for Remote Sensing and Space Sciences, Cairo, Egypt. 3University of ... Keywords: Urban growth, urban heat Island, land surface temperatures, satellite remote sensing .... observed target includes green vegetation or not.

  14. Global 1-km Sea Surface Temperature (G1SST)

    Data.gov (United States)

    National Aeronautics and Space Administration — JPL OurOcean Portal: A daily, global Sea Surface Temperature (SST) data set is produced at 1-km (also known as ultra-high resolution) by the JPL ROMS (Regional Ocean...

  15. COBE-SST2 Sea Surface Temperature and Ice

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A new sea surface temperature (SST) analysis on a centennial time scale is presented. The dataset starts in 1850 with monthly 1x1 means and is periodically updated....

  16. Surface layer temperature inversion in the Arabian Sea during winter

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Ghosh, A.K.

    Surface layer temperature inversion in the south eastern Arabian Sea, during winter has been studied using Bathythermograph data collected from 1132 stations. It is found that the inversion in this area is a stable seasonal feature...

  17. Seasonal Sea Surface Temperature Averages, 1985-2001 - Direct Download

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set consists of four images showing seasonal sea surface temperature (SST) averages for the entire earth. Data for the years 1985-2001 are averaged to...

  18. 1996 Average Monthly Sea Surface Temperature for California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA/ NASA AVHRR Oceans Pathfinder sea surface temperature data are derived from the 5-channel Advanced Very High Resolution Radiometers (AVHRR) on board the...

  19. 2000 Average Monthly Sea Surface Temperature for California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA/ NASA AVHRR Oceans Pathfinder sea surface temperature data are derived from the 5-channel Advanced Very High Resolution Radiometers (AVHRR) on board the...

  20. OW NOAA Pathfinder/GAC Sea-Surface Temperature

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The dataset contains satellite-derived sea-surface temperature measurements collected by means of the Advanced Very High Resolution Radiometer - Global Area Coverage...

  1. OW NOAA AVHRR-GAC Sea-Surface Temperature

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The dataset contains satellite-derived sea-surface temperature measurements collected by means of the Advanced Very High Resolution Radiometer - Global Area Coverage...

  2. NOAA High-Resolution Sea Surface Temperature (SST) Analysis Products

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archive covers two high resolution sea surface temperature (SST) analysis products developed using an optimum interpolation (OI) technique. The analyses have a...

  3. Tropical sea surface temperatures and the earth's orbital eccentricity cycles

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.; Fernandes, A.A.; Mohan, R.

    The tropical oceanic warm pools are climatologically important regions because their sea surface temperatures (SSTs) are positively related to atmospheric greenhouse effect and the cumulonimbus-cirrus cloud anvil. Such a warm pool is also present...

  4. Snell's law for particles moving on piecewise homogeneous two dimensional surface with linear boundaries

    CERN Document Server

    Mandrekar, Pratik

    2011-01-01

    We study the properties of least time trajectories for particles moving on a two dimensional surface which consists of piecewise homogeneous regions. The particles are assumed to move with different constant speeds on different regions and on the boundary between regions. The speed of the particle is assumed to be highest when it moves along the edges formed by the boundary of two regions. We get an analogous behavior to Snell's Law of light refraction, but in a more generalized form. The model could be used for studying properties of animal and insect trails which tend to form predominantly along edges. The model predicts three types of behavior for the trajectories near a corner forming edge: fully edge following, partial edge following and complete avoidance of the edge, which are indeed observed in natural ant trails.

  5. Experimental Study of Turbulent Boundary Layers on Groove/Smooth Flat Surfaces

    Institute of Scientific and Technical Information of China (English)

    Hongwei MA; Qiao TIAN; Hui WU

    2005-01-01

    This paper presents an experimental investigation of the turbulent boundary layers on both groove and smooth flat surfaces. The flow structures were shown in a water tunnel using the hydrogen-bubble flow visualization technique. The measurement results indicate that: (1) the grooves can effectively reduce accumulation of low-speed fluids, decrease the number of the low-speed streaks and depress oscillation of the streaks in the sublayer; (2) the grooves can restrain forming of the horseshoe vortices in the buffer region; (3) the grooves bate oscillation and kinking of the quasi-streamwise vortices and restrain production of the hairpin vortices and the ring vortices, reducing both frequency and intensity of the turbulence bursting; (4) the grooves directly affect the flow structures in the sublayer of the boundary layer and then modulate the flow field up to the buffer region and the logarithmic region by restraining development and interaction of the vortices.

  6. Heat transfer and fluid mechanics measurements in transitional boundary layers on convex-curved surfaces

    Science.gov (United States)

    Wang, T.; Simon, T. W.

    1987-01-01

    The test section of the present experiment to ascertain the effects of convex curvature and freestream turbulence on boundary layer momentum and heat transfer during natural transition provided a two-dimensional boundary layer flow on a uniformly heated curved surface, with bending to various curvature radii, R. Attention is given to results for the cases of R = infinity, 180 cm, and 90 cm, each with two freestream turbulence intensity levels. While the mild convex curvature of R = 180 cm delays transition, further bending to R = 90 cm leads to no signifucant further delay of transition. Cases with both curvature and higher freestream disturbance effects exhibit the latter's pronounced dominance. These data are pertinent to the development of transition prediction models for gas turbine blade design.

  7. Temperature Distribution Measurement of The Wing Surface under Icing Conditions

    Science.gov (United States)

    Isokawa, Hiroshi; Miyazaki, Takeshi; Kimura, Shigeo; Sakaue, Hirotaka; Morita, Katsuaki; Japan Aerospace Exploration Agency Collaboration; Univ of Notre Dame Collaboration; Kanagawa Institute of Technology Collaboration; Univ of Electro-(UEC) Team, Comm

    2016-11-01

    De- or anti-icing system of an aircraft is necessary for a safe flight operation. Icing is a phenomenon which is caused by a collision of supercooled water frozen to an object. For the in-flight icing, it may cause a change in the wing cross section that causes stall, and in the worst case, the aircraft would fall. Therefore it is important to know the surface temperature of the wing for de- or anti-icing system. In aerospace field, temperature-sensitive paint (TSP) has been widely used for obtaining the surface temperature distribution on a testing article. The luminescent image from the TSP can be related to the temperature distribution. (TSP measurement system) In icing wind tunnel, we measured the surface temperature distribution of the wing model using the TSP measurement system. The effect of icing conditions on the TSP measurement system is discussed.

  8. Josephson oscillations and noise temperatures in YBa2Cu3O7-x grain-boundary junctions

    DEFF Research Database (Denmark)

    Yu, Ya. Divin; Mygind, Jesper; Pedersen, Niels Falsig;

    1992-01-01

    The ac Josephson effect was studied in YBa2Cu3O7−x grain-boundary junctions (GBJ) in the temperature range from 4 to 90 K. The temperature dependence of the linewidth of millimeter-wave Josephson oscillations was measured and it is shown that the derived effective noise temperatures may be as low...... as the physical temperature in the temperature range investigated. In the millimeter-wave range, linewidths as low as 380 MHz were found at liquid-nitrogen temperatures. Applied Physics Letters is copyrighted by The American Institute of Physics....

  9. High temperature photoelectron emission and surface photovoltage in semiconducting diamond

    Science.gov (United States)

    Williams, G. T.; Cooil, S. P.; Roberts, O. R.; Evans, S.; Langstaff, D. P.; Evans, D. A.

    2014-08-01

    A non-equilibrium photovoltage is generated in semiconducting diamond at above-ambient temperatures during x-ray and UV illumination that is sensitive to surface conductivity. The H-termination of a moderately doped p-type diamond (111) surface sustains a surface photovoltage up to 700 K, while the clean (2 × 1) reconstructed surface is not as severely affected. The flat-band C 1s binding energy is determined from 300 K measurement to be 283.87 eV. The true value for the H-terminated surface, determined from high temperature measurement, is (285.2 ± 0.1) eV, corresponding to a valence band maximum lying 1.6 eV below the Fermi level. This is similar to that of the reconstructed (2 × 1) surface, although this surface shows a wider spread of binding energy between 285.2 and 285.4 eV. Photovoltage quantification and correction are enabled by real-time photoelectron spectroscopy applied during annealing cycles between 300 K and 1200 K. A model is presented that accounts for the measured surface photovoltage in terms of a temperature-dependent resistance. A large, high-temperature photovoltage that is sensitive to surface conductivity and photon flux suggests a new way to use moderately B-doped diamond in voltage-based sensing devices.

  10. Seasonally and diurnally different response of surface air temperature to historical urbanization in Sapporo, North Japan

    Science.gov (United States)

    Sato, T.; Sugimoto, S.; Sasaki, T.

    2014-12-01

    Anthropogenic landscape changes have dramatically altered near surface climate in many regions of the world. In particular, regional/local-scale land use change is attributed to the long-term change in observed surface air temperature through changes in surface radiation budget and energy partitioning. This study analyses the response of surface air temperature characteristics to the historical urbanization in Sapporo, a snowy city in North Japan. Around Sapporo, natural forest has been cleared and replaced with urban since the late 19th century. Annual mean temperature in Sapporo has increased dramatically, whose rate being approximately twice of that in the station without urbanization. The rate of temperature increase shows asymmetric feature among seasons and dependent on time of the day; a prominent warming in winter daily minimum temperature and no significant trend in summer daily maximum temperature. In order to clarify the seasonal and diurnal dependence of the response to land use change, two 27-year simulations were conducted using WRF-ARW model nudged to reanalysis data during 19872/1983 winter to 2008/2009 winter; a control run uses past land cover and a sensitivity run uses present land cover. The numerical experiments successfully replicate the observed influence of urbanization with higher temperature change in winter nights and smaller temperature change in summer days. An analysis on surface energy balance indicates the changes in Bowen ratio is a primal cause of increasing sensible heat in both summer and winter. However, atmospheric response to the elevated sensible heat flux is very different depending on boundary layer structure between winter and summer or between night and day. This mechanism could clearly explain the asymmetric temperature trend observed worldwide, especially in cold regions where nocturnal inversion develops.

  11. The sensitivity of OMI-derived nitrogen dioxide to boundary layer temperature inversions

    Science.gov (United States)

    Wallace, Julie; Kanaroglou, Pavlos

    We assess the sensitivity of tropospheric nitrogen dioxide (NO 2) derived from the Ozone Monitoring Instrument (OMI), to episodes of temperature inversion in the lower boundary layer. Vertical temperature data were obtained from a 91-m meteorological tower located in the study area, which is centered on the Hamilton Census Metropolitan Area, Ontario, Canada. Hamilton is an industrial city with high traffic volumes, and is therefore subjected to high levels of pollution. Pollution buildup is amplified by frequent temperature inversions which are commonly radiative, but are also induced by local physiography, proximity to Lake Ontario, and regional meteorology. The four-year period from January 2005 to December 2008 was investigated. Ground-level data for validation were obtained from in situ air quality monitors located in the study area. The results indicate that OMI is sensitive to changes in the NO 2 levels during temperature inversions, and exhibits changes which roughly parallel those of in situ monitors. Overall, an 11% increase in NO 2 was identified by OMI on inversion days, compared to a 44% increase measured by in situ monitors. The weekend effect was clearly exhibited under both normal and inversion scenarios with OMI. Seasonal and wind direction patterns also correlated fairly well with ground-level data. Temperature inversions have resulted in poor air quality episodes which have severely compromised the health of susceptible populations, sometime leading to premature death. The rationale for this study is to further assess the usefulness of OMI for population exposure studies in areas with sparse resources for ground-level monitoring.

  12. Temperature Compensation of Surface Acoustic Waves on Berlinite

    Science.gov (United States)

    Searle, David Michael Marshall

    The surface acoustic wave properties of Berlinite (a-AlPO4) have been investigated theoretically and experimentally, for a variety of crystallographic orientations, to evaluate its possible use as a substrate material for temperature compensated surface acoustic wave devices. A computer program has been developed to calculate the surface wave properties of a material from its elastic, piezoelectric, dielectric and lattice constants and their temperature derivatives. The program calculates the temperature coefficient of delay, the velocity of the surface wave, the direction of power flow and a measure of the electro-mechanical coupling. These calculations have been performed for a large number of orientations using a modified form of the data given by Chang and Barsch for Berlinite and predict several new temperature compensated directions. Experimental measurements have been made of the frequency-temperature response of a surface acoustic wave oscillator on an 80° X axis boule cut which show it to be temperature compensated in qualitative agreement with the theoretical predictions. This orientation shows a cubic frequency-temperature dependence instead of the expected parabolic response. Measurements of the electro-mechanical coupling coefficient k gave a value lower than predicted. Similar measurements on a Y cut plate gave a value which is approximately twice that of ST cut quartz, but again lower than predicted. The surface wave velocity on both these cuts was measured to be slightly higher than predicted by the computer program. Experimental measurements of the lattice parameters a and c are also presented for a range of temperatures from 25°C to just above the alpha-beta transition at 584°C. These results are compared with the values obtained by Chang and Barsch. The results of this work indicate that Berlinite should become a useful substrate material for the construction of temperature compensated surface acoustic wave devices.

  13. The Diurnal Temperature Cycle and Its Relation to Boundary-Layer Structure During the Morning Transition

    Science.gov (United States)

    Ketzler, G.

    2014-05-01

    The morning portion of the near-surface diurnal temperature cycle is analyzed in combination with heat-flux and vertical temperature-gradient data. During summer, mean diurnal cycles of temperature rates-of-change show periods that can be related to defined points of the morning transition (MT). The start of the MT is clearly marked with a temperature discontinuity, apparent even on individual days, while the end of the transition is apparent only when using averages over many days. The findings concerning the timing of the MT using temperature cycle analysis correspond well with studies using heat-flux measurements. Mean diurnal cycles of temperature rates-of-change for stations in different urban and valley positions show differences that can partly be explained by apparent effects of the surroundings. For the valley situation, the timing differences and their relation to station position in the valley are generally plausible, while urban effects on the diurnal cycle are apparent but less distinct, which may be due to the small number of stations used. The results indicate that warming already begins before heat-flux crossover, which is the current definition of the beginning of the MT. This definition should be extended to include the phase between the temperature rate-of-change crossover and heat-flux crossover, which represents the early part of the MT before warming reaches instrument level.

  14. Axisymmetric Stagnation-Point Flow with a General Slip Boundary Condition over a Lubricated Surface

    Institute of Scientific and Technical Information of China (English)

    M. Sajid; K. Mahmood; Z. Abbas

    2012-01-01

    We investigate the axisymmetric stagnation-point flow of a viscous fluid over a lubricated surface by imposing a generalized slip condition at the fluid-fluid interface.The power law non-Newtonian fluid is considered as a lubricant.The lubrication layer is thin and assumed to have a variable thickness.The transformed nonlinear ordinary differential equation governing the flow is linearized using quasilinearization.The method of superposition is adopted to convert the boundary value problem into an initial value problem and the solution is obtained numerically by using the fourth-order RungeKutta method.The results are discussed to see the influence of pertinent parameters.The limiting cases of Navier and no-slip boundary conditions are obtained as the special cases and found to be in excellent agreement with the existing results in the literature.%We investigate the axisymmetric stagnation-point flow of a viscous fluid over a lubricated surface by imposing a generalized slip condition at the fluid-fluid interface. The power law non-Newtonian fluid is considered as a lubricant. The lubrication layer is thin and assumed to have a variable thickness. The transformed nonlinear ordinary differential equation governing the flow is linearized using quasilinearization. The method of superposition is adopted to convert the boundary value problem into an initial value problem and the solution is obtained numerically by using the fourth-order Runge Kutta method. The results arc discussed to see the influence of pertinent parameters. The limiting cases of Navier and no-slip boundary conditions are obtained as the special cases and found to be in excellent agreement with the existing results in the literature.

  15. SURFACE TEMPERATURES ON TITAN DURING NORTHERN WINTER AND SPRING

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, D. E.; Cottini, V.; Nixon, C. A.; Achterberg, R. K.; Flasar, F. M.; Kunde, V. G.; Romani, P. N.; Samuelson, R. E. [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mamoutkine, A. [ADNET Systems, Inc., Bethesda, MD 20817 (United States); Gorius, N. J. P. [The Catholic University of America, Washington, DC 20064 (United States); Coustenis, A. [Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique (LESIA), Observatoire de Paris, CNRS, UPMC Univ. Paris 06, Univ. Paris-Diderot, 5, place Jules Janssen, F-92195 Meudon Cedex (France); Tokano, T., E-mail: donald.e.jennings@nasa.gov [Universität zu Köln, Albertus-Magnus-Platz, D-50923 Köln (Germany)

    2016-01-01

    Meridional brightness temperatures were measured on the surface of Titan during the 2004–2014 portion of the Cassini mission by the Composite Infrared Spectrometer. Temperatures mapped from pole to pole during five two-year periods show a marked seasonal dependence. The surface temperature near the south pole over this time decreased by 2 K from 91.7 ± 0.3 to 89.7 ± 0.5 K while at the north pole the temperature increased by 1 K from 90.7 ± 0.5 to 91.5 ± 0.2 K. The latitude of maximum temperature moved from 19 S to 16 N, tracking the sub-solar latitude. As the latitude changed, the maximum temperature remained constant at 93.65 ± 0.15 K. In 2010 our temperatures repeated the north–south symmetry seen by Voyager one Titan year earlier in 1980. Early in the mission, temperatures at all latitudes had agreed with GCM predictions, but by 2014 temperatures in the north were lower than modeled by 1 K. The temperature rise in the north may be delayed by cooling of sea surfaces and moist ground brought on by seasonal methane precipitation and evaporation.

  16. Temperature dependence of surface enhanced Raman scattering on C70

    Institute of Scientific and Technical Information of China (English)

    GAO Ying; Zhang Zhenlong; DU Yinxiao; DONG Hua; MO Yujun

    2005-01-01

    The temperature dependence of surface enhanced Raman scattering of the C70 molecule is reported.The Raman scattering of C70 molecules adsorbed on the surface of a silver mirror was measured at different temperatures. The experimental results indicate that the relative intensities of the Raman features vary with the temperature of the sample. When the temperature decreases from room temperature to 0℃, the relative intensities of certain Raman bands decrease abruptly. If we take the strongest band 1565cm-1 as a standard value 100, the greatest decrease approaches to 43%. However, with the further decrease in the temperature these relative intensities increase and resume the value at room temperature. And such a temperature dependence is reversible. Our results show that the adsorption state of the C70 molecules on the silver surface around 0℃changes greatly with the temperature, resulting in a decrease in relative intensities for some main Raman features of C70molecule. When the temperature is lower than 0℃, the adsorption state changes continually and more slowly. Synchronously, eight new Raman featu res, which have not ever been reported in literature, are observed in our experiment and this enriches the basic information of the vibrational modes for C70 molecule.

  17. Sea Surface Temperature from EUMETSAT Including Sentinel-3 SLSTR

    Science.gov (United States)

    O'Carroll, Anne; Bonekamp, Hans; Montagner, Francois; Santacesaria, Vincenzo; Tomazic, Igor

    2015-12-01

    The paper gives an overview of sea surface temperature (SST) activities at EUMETSAT including information on SST planned from the Sea and Land Surface Temperature Radiometer (SLSTR). Operational oceanography activities within the Marine Applications group at EUMETSAT continue with a focus on SST, sea surface winds, sea-ice products, radiative fluxes, significant wave height and sea surface topography. These are achieved through the mandatory, optional and third-party programmes, and for some products with the EUMETSAT Ocean and Sea-Ice Satellite Application Facility (OSI SAF). Progress towards products from sea-ice surface temperature, ocean colour products, turbidity and aerosol optical depth over water continue. Information on oceanography products from EUMETSAT can be found through the product navigator (http://navigator.eumetsat.int). EUMETSAT have been collaborating with ESA for a number of years on the development of SST for SLSTR.

  18. Numerical Analysis of the Slip Velocity and Temperature-Jump in Microchannel Using Langmuir Slip Boundary Condition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Woo; Kim, Hyun Goo; Lee, Do Hyung [Hanyang University, Seoul (Korea, Republic of)

    2009-03-15

    The slip velocity and the temperature jumps for low-speed flow in microchannels are investigated using Langmuir slip boundary condition. This slip boundary condition is suggested to simulate micro flow. The current study analyzes Langmuir slip boundary condition theoretically and it analyzed numerically micro-Couette flow, micro-Poiseuille flow and grooved microchannel flow. First, to prove validity for Langmuir slip condition, an analytical solution for micro-Couette flow is derived from Navier-Stokes equations with Langmuir slip conditions and is compared with DSMC and an analytical solution with Maxwell slip boundary condition. Second, the numerical analysis is performed for micro-Poiseuille flow and grooved microchannel flow. The slip velocity and temperature distribution are compared with results of DSMC or Maxwell slip condition and those are shown in good agreement.

  19. Are boundary conditions in surface productivity at the Southern Polar Front reflected in benthic activity?

    Science.gov (United States)

    Brandt, Angelika; Vanreusel, Ann; Bracher, Astrid; Jule Marie Hoppe, Clara; Lins, Lidia; Meyer-Löbbecke, Anna; Altenburg Soppa, Mariana; Würzberg, Laura

    2014-10-01

    In austral summer 2012, during the expedition ANT-XXVIII/3 on board RV Polarstern, two sites were sampled 1600 km apart in the South Polar Front area (52°S) at the boundary of different productivity regimes for meio- and macrobenthos using a multiple-corer and an epibenthic sledge, respectively. Patterns in density and abundance data were compared between different size classes of the benthos and interpreted in relation to surface primary productivity data and sediment oxygen consumption. We tested the hypothesis that long-term satellite-derived surface phytoplankton biomass, in situ real time biomass, and productivity measurements at the surface and throughout the euphotic zone are reflected in abyssal benthos densities, abundances and activity. Specifically, we investigated the effect of boundary conditions for lower and higher surface productivity. Surface and integrated to 100 m depth biomass and primary productivity measurements vary stations, with the lowest values at station 85 (0.083 mg Chl-a m-3 at surface, 9 mg Chl-a m-2 and 161 mg C m-2 d-1- integrated over the first 100 m depth), and the highest values at station 86 (2.231 mg Chl-a m-3 at surface, 180 mg Chl-a m-2 and 2587 mg C m-2 d-1 integrated over first 100 m depth). Total meiofaunal densities varied between 102 and 335 individuals/10 cm². Densities were the highest at station 86-30 (335 individuals) and lowest at station 81-13 (102 individuals). Total macrofaunal densities (individuals/1000 m²) varied between 26 individuals at station 81-17 and 194 individuals at station 86-24. However, three EBS hauls were taken at station 86 with a minimum of 80 and a maximum of 194 individuals. Sediment oxygen consumption did not vary significantly between stations from east to west. Bentho-pelagic coupling of meio- and macrobenthic communities could not be observed in the South Polar Front at the boundary conditions from low to high surface productivity between stations 81 and 86.

  20. Wind-tunnel experiments of turbulent flow over a surface-mounted 2-D block in a thermally-stratified boundary layer

    Science.gov (United States)

    Zhang, Wei; Markfort, Corey; Porté-Agel, Fernando

    2014-11-01

    Turbulent flows over complex surface topography have been of great interest in the atmospheric science and wind engineering communities. The geometry of the topography, surface roughness and temperature characteristics as well as the atmospheric thermal stability play important roles in determining momentum and scalar flux distribution. Studies of turbulent flow over simplified topography models, under neutrally stratified boundary-layer conditions, have provided insights into fluid dynamics. However, atmospheric thermal stability has rarely been considered in laboratory experiments, e.g., wind-tunnel experiments. Series of wind-tunnel experiments of thermally-stratified boundary-layer flow over a surface-mounted 2-D block, in a well-controlled boundary-layer wind tunnel, will be presented. Measurements using high-resolution PIV, x-wire/cold-wire anemometry and surface heat flux sensors were conducted to quantify the turbulent flow properties, including the size of the recirculation zone, coherent vortex structures and the subsequent boundary layer recovery. Results will be shown to address thermal stability effects on momentum and scalar flux distribution in the wake, as well as dominant mechanism of turbulent kinetic energy generation and consumption. The authors gratefully acknowledge funding from the Swiss National Foundation (Grant 200021-132122), the National Science Foundation (Grant ATM-0854766) and NASA (Grant NNG06GE256).

  1. Boundary layer flow on a moving surface in otherwise quiescent pseudo-plastic non-Newtonian fluids

    Institute of Scientific and Technical Information of China (English)

    Liancun Zheng; Liu Ting; Xinxin Zhang

    2008-01-01

    A theoretical analysis for the boundary layer flow over a continuous moving surface in an otherwise quiescent pseudo-plastic non-Newtonian fluid medium was presented. The types of potential flows necessary for similar solutions to the boundary layer equations were determined and the solutions were numerically presented for different values of power law exponent.

  2. Stick-slip control in nanoscale boundary lubrication by surface wettability.

    Science.gov (United States)

    Chen, Wei; Foster, Adam S; Alava, Mikko J; Laurson, Lasse

    2015-03-06

    We study the effect of atomic-scale surface-lubricant interactions on nanoscale boundary-lubricated friction by considering two example surfaces-hydrophilic mica and hydrophobic graphene-confining thin layers of water in molecular dynamics simulations. We observe stick-slip dynamics for thin water films confined by mica sheets, involving periodic breaking-reforming transitions of atomic-scale capillary water bridges formed around the potassium ions of mica. However, only smooth sliding without stick-slip events is observed for water confined by graphene, as well as for thicker water layers confined by mica. Thus, our results illustrate how atomic-scale details affect the wettability of the confining surfaces and consequently control the presence or absence of stick-slip dynamics in nanoscale friction.

  3. Local surface sampling step estimation for extracting boundaries of planar point clouds

    Science.gov (United States)

    Brie, David; Bombardier, Vincent; Baeteman, Grégory; Bennis, Abdelhamid

    2016-09-01

    This paper presents a new approach to estimate the surface sampling step of planar point clouds acquired by Terrestrial Laser Scanner (TLS) which is varying with the distance to the surface and the angular positions. The local surface sampling step is obtained by doing a first order Taylor expansion of planar point coordinates. Then, it is shown how to use it in Delaunay-based boundary point extraction. The resulting approach, which is implemented in the ModiBuilding software, is applied to two facade point clouds of a building. The first is acquired with a single station and the second with two stations. In both cases, the proposed approach performs very accurately and appears to be robust to the variations of the point cloud density.

  4. Chemically Reactive Solute Distribution in a Steady MHD Boundary Layer Flow over a Stretching Surface

    Directory of Open Access Journals (Sweden)

    M.S Uddin

    2011-01-01

    Full Text Available The paper is concerned to find the distribution of the chemically reactant solute in the MHD flow of an electrically conducting viscous incompressible fluid over a stretching surface. The first order chemical reaction and the variable solute distribution along the surface are taken into consideration. The governing partial differential equations along with appropriate boundary conditions for flow field and reactive solute are transformed into a set of non-linear self-similar ordinary differential equations by using scaling group of transformations. An exact analytic solution is obtained for the velocity field. Using this velocity field, we obtain numerical solution for the reactant concentration field. It reveals from the study that the values of concentration profile enhances with the increase of the magnetic field and decreases with increase of Schmidt number as well as the reaction rate parameter. Most importantly, when the solute distribution along the surface increases then the concentration profile decreases.

  5. Effect of roughness lengths on surface energy and the planetary boundary layer height over high-altitude Ngoring Lake

    Science.gov (United States)

    Li, Zhaoguo; Lyu, Shihua; Wen, Lijuan; Zhao, Lin; Meng, Xianhong; Ao, Yinhuan

    2017-08-01

    The special climate environment creates a distinctive air-lake interaction characteristic in the Tibetan Plateau (TP) lakes, where the variations of surface roughness lengths also differ somewhat from those of other regions. However, how different categories of roughness lengths affect the lake surface energy exchange and the planetary boundary layer height (PBLH) remains unclear in the TP lakes. In this study, we used a tuned Weather Research and Forecasting (WRF) model version 3.6.1 to investigate the responses of the freeze-up date, turbulent fluxes, meteorological variables, and PBLH to surface roughness length variations in Ngoring Lake. Of all meteorological variables, the lake surface temperature responded to roughness length variations most sensitively; increasing roughness lengths can put the lake freeze-up date forward. The effect of momentum roughness length on wind speed was significantly affected by the fetch length. The increase in the roughness length for heat can induce the increment of the nightly PBLH in most months, especially for the central lake area in autumn. The primary factors that contribute to sensible heat flux (H) and latent heat flux (LE) were the roughness lengths for heat and momentum during the ice-free period, respectively. Increasing roughness length for heat can increase the nightly PBLH, and decreasing roughness length for moisture can also promote growth of the PBLH, but there was no obvious correlation between the momentum roughness length and the PBLH.

  6. A model of the ground surface temperature for micrometeorological analysis

    Science.gov (United States)

    Leaf, Julian S.; Erell, Evyatar

    2017-07-01

    Micrometeorological models at various scales require ground surface temperature, which may not always be measured in sufficient spatial or temporal detail. There is thus a need for a model that can calculate the surface temperature using only widely available weather data, thermal properties of the ground, and surface properties. The vegetated/permeable surface energy balance (VP-SEB) model introduced here requires no a priori knowledge of soil temperature or moisture at any depth. It combines a two-layer characterization of the soil column following the heat conservation law with a sinusoidal function to estimate deep soil temperature, and a simplified procedure for calculating moisture content. A physically based solution is used for each of the energy balance components allowing VP-SEB to be highly portable. VP-SEB was tested using field data measuring bare loess desert soil in dry weather and following rain events. Modeled hourly surface temperature correlated well with the measured data (r 2 = 0.95 for a whole year), with a root-mean-square error of 2.77 K. The model was used to generate input for a pedestrian thermal comfort study using the Index of Thermal Stress (ITS). The simulation shows that the thermal stress on a pedestrian standing in the sun on a fully paved surface, which may be over 500 W on a warm summer day, may be as much as 100 W lower on a grass surface exposed to the same meteorological conditions.

  7. Determination of temperature of moving surface by sensitivity analysis

    CERN Document Server

    Farhanieh, B

    2002-01-01

    In this paper sensitivity analysis in inverse problem solutions is employed to estimate the temperature of a moving surface. Moving finite element method is used for spatial discretization. Time derivatives are approximated using Crank-Nicklson method. The accuracy of the solution is assessed by simulation method. The convergence domain is investigated for the determination of the temperature of a solid fuel.

  8. A new interpolation method for Antarctic surface temperature

    Institute of Scientific and Technical Information of China (English)

    Yetang Wang; Shugui Hou

    2009-01-01

    We propose a new methodology for the spatial interpolation of annual mean temperature into a regular grid with a geographic resolution of 0.01° for Antarctica by applying a recent compilation of the Antarctic temperature data.A multiple linear regression model of the dependence of temperature on some geographic parameters (i.e.,latitude,longitude,and elevation) is proposed empirically,and the kriging method is used to determine the spatial distribution of regional and local deviations from the temperature calculated from the multiple linear regression model.The modeled value and residual grids are combined to derive a high-resolution map of surface air temperature.The performance of our new methodology is superior to a variety of benchmark methods (e.g.,inverse distance weighting,kriging,and spline methods) via cross-validation techniques.Our simulation resembles well with those distinct spatial features of surface temperature,such as the decrease in annual mean surface temperature with increasing latitude and the distance away from the coast line;and it also reveals the complex topographic effects on the spatial distribution of surface temperature.

  9. Electrical properties of bilayer graphene synthesized using surface wave microwave plasma techniques at low temperature

    Science.gov (United States)

    Yamada, Takatoshi; Kato, Hiromitsu; Okigawa, Yuki; Ishihara, Masatou; Hasegawa, Masataka

    2017-01-01

    Bilayer graphene was synthesized at low temperature using surface wave microwave plasma techniques where poly(methyl metacrylate) (PMMA) and methane (CH4) were used as carbon sources. Temperature-dependent Hall effect measurements were carried out in a helium atmosphere. Sheet resistance, sheet carrier density and mobility showed weak temperature dependence for graphene from PMMA, and the highest carrier mobility is 740 cm2 V-1 s-1. For graphene from CH4, tunneling of the domain boundary limited carrier transport. The difference in average domain size was determined by Raman signal maps. In addition, residuals of PMMA were detected on graphene from PMMA. The low sheet resistances of graphene synthesized at a temperature of 280 °C using plasma techniques were explained by the PMMA related residuals rather than the domain sizes.

  10. Analysis of Anomaly in Land Surface Temperature Using MODIS Products

    Science.gov (United States)

    Yorozu, K.; Kodama, T.; Kim, S.; Tachikawa, Y.; Shiiba, M.

    2011-12-01

    Atmosphere-land surface interaction plays a dominant role on the hydrologic cycle. Atmospheric phenomena cause variation of land surface state and land surface state can affect on atmosphereic conditions. Widely-known article related in atmospheric-land interaction was published by Koster et al. in 2004. The context of this article is that seasonal anomaly in soil moisture or soil surface temperature can affect summer precipitation generation and other atmospheric processes especially in middle North America, Sahel and south Asia. From not only above example but other previous research works, it is assumed that anomaly of surface state has a key factor. To investigate atmospheric-land surface interaction, it is necessary to analyze anomaly field in land surface state. In this study, soil surface temperature should be focused because it can be globally and continuously observed by satellite launched sensor. To land surface temperature product, MOD11C1 and MYD11C1 products which are kinds of MODIS products are applied. Both of them have 0.05 degree spatial resolution and daily temporal resolution. The difference of them is launched satellite, MOD11C1 is Terra and MYD11C1 is Aqua. MOD11C1 covers the latter of 2000 to present and MYD11C1 covers the early 2002 to present. There are unrealistic values on provided products even if daily product was already calibrated or corrected. For pre-analyzing, daily data is aggregated into 8-days data to remove irregular values for stable analysis. It was found that there are spatial and temporal distribution of 10-years average and standard deviation for each 8-days term. In order to point out extreme anomaly in land surface temperature, standard score for each 8-days term is applied. From the analysis of standard score, it is found there are large anomaly in land surface temperature around north China plain in early April 2005 and around Bangladesh in early May 2009.

  11. Hydrogen embrittlement, grain boundary segregation, and stress corrosion cracking of alloy X-750 in low- and high-temperature water

    Energy Technology Data Exchange (ETDEWEB)

    Mills, W. J.; Lebo, M. R.; Kearns, J. J. [Bettis Atomic Power Lab., West Mifflin, PA (United States)

    1997-04-01

    The nature of intergranular stress corrosion cracking (SCC) of alloy X-750 was characterized in low- and high-temperature water by testing as-notched and precracked fracture mechanics specimens. Materials given the AH, BH, and HTH heat treatments were studied. While all heat treatments were susceptible to rapid low-temperature crack propagation (LTCP) below 150 C, conditions AH and BH were particularly susceptible. Low-temperature tests under various loading conditions (e.g., constant displacement, constant load, and increasing load) revealed that the maximum stress intensity factors (K{sub P{sub max}}) from conventional rising load tests provide conservative estimates of the critical loading conditions in highly susceptible heats, regardless of the load path history. For resistant heats, K{sub P{sub max}} provides a reasonable, but not necessarily conservative, estimate of the critical stress intensity factor for LTCP. Testing of as-notched specimens showed that LTCP will not initiate at a smooth surface or notch, but will readily occur if a cracklike defect is present. Comparison of the cracking response in water with that for hydrogen-precharged specimens tested in air demonstrated that LTCP is associated with hydrogen embrittlement of grain boundaries. The stress corrosion crack initiation and growth does occur in high-temperature water (>250 C), but crack growth rates are orders of magnitude lower than LTCP rates. The SCC resistance of HTH heats is far superior to that of AH heats as crack initiation times are two to three orders of magnitude greater and growth rates are one to two orders of magnitude lower.

  12. Influence of surface structure of (0001 sapphire substrate on the elimination of small-angle grain boundary in AlN epilayer

    Directory of Open Access Journals (Sweden)

    Ryan G. Banal

    2015-09-01

    Full Text Available AlN epilayers were grown on (0001 sapphire substrates by metal-organic vapor phase epitaxy, and the influence of the substrate’s surface structure on the formation of in-plane rotation domain is studied. The surface structure is found to change with increasing temperature under H2 ambient. The ML steps of sapphire substrate formed during high-temperature (HT thermal cleaning is found to cause the formation of small-angle grain boundary (SAGB. To suppress the formation of such structure, the use of LT-AlN BL technique was demonstrated, thereby eliminating the SAGB. The BL growth temperature (Tg is also found to affect the surface morphology and structural quality of AlN epilayer. The optical emission property by cathodoluminescence (CL measurement showed higher emission intensity from AlN without SAGB. The LT-AlN BL is a promising technique for eliminating the SAGB.

  13. Radar Backscatter Across the Gulf Stream Sea Surface Temperature Front

    Science.gov (United States)

    Nghiem, S. V.; Li, F. K.; Walsh, E. J.; Lou, S. H.

    1998-01-01

    Ocean backscatter signatures were measured by the Jet Propulsion Laboratory airborne NUSCAT K(sub u)-band scatterometer across the Gulf Stream sea surface temperature front. The measurements were made during the Surface Wave Dynamics Experiment (SWADE) off the coast of Virginia and Maryland in the winter of 1991.

  14. estimation of land surface temperature of kaduna metropolis, nigeria

    African Journals Online (AJOL)

    Zaharaddeen et. al

    Understanding the spatial variation of Land Surface Temperature. (LST), will be ... positive correlation between mean of surface emissivity with date and ... deviation of 1.92 of LST and coefficient determinant R2 (0.46) show a ... (LST), as the prime and basic physical parameter of the earth's ..... thorough review of the paper.

  15. Surface compositional variations of Mo-47Re alloy as a function of temperature

    Energy Technology Data Exchange (ETDEWEB)

    Hoekje, S.J.; Outlaw, R.A.; Sankaran, S.N.

    1993-12-01

    Molybdenum-rhenium alloys are candidate materials for the National Aero-Space Plane (NASP) as well as for other applications in generic hypersonics. These materials are expected to be subjected to high-temperature (above 1200 C) casual hydrogen (below 50 torr), which could potentially degrade the material strength. Since the uptake of hydrogen may be controlled by the contaminant surface barriers, a study of Mo-47Re was conducted to examine the variations in surface composition as a function of temperature from 25 C to 1000 C. Pure molybdenum and rhenium were also examined and the results compared with those for the alloy. The analytical techniques employed were Auger electron spectroscopy, electron energy loss spectroscopy, ion scattering spectroscopy, and x ray photoelectron spectroscopy. The native surface was rich in metallic oxides that disappeared at elevated temperatures. As the temperature increased, the carbon and oxygen disappeared by 800 C and the surface was subsequently populated by the segregation of silicon, presumably from the grain boundaries. The alloy readily chemisorbed oxygen, which disappeared with heating. The disappearance temperature progressively increased for successive dosings. When the alloy was exposed to 800 torr of hydrogen at 900 C for 1 hour, no hydrogen interaction was observed.

  16. High Reynolds number rough wall turbulent boundary layer experiments using Braille surfaces

    Science.gov (United States)

    Harris, Michael; Monty, Jason; Nova, Todd; Allen, James; Chong, Min

    2007-11-01

    This paper details smooth, transitional and fully rough turbulent boundary layer experiments in the New Mexico State high Reynolds number rough wall wind tunnel. The initial surface tested was generated with a Braille printer and consisted of an uniform array of Braille points. The average point height being 0.5mm, the spacing between the points in the span was 0.5mm and the surface consisted of span wise rows separated by 4mm. The wavelength to peak ratio was 8:1. The boundary layer thickness at the measurement location was 190mm giving a large separation of roughness height to layer thickness. The maximum friction velocity was uτ=1.5m/s at Rex=3.8 x10^7. Results for the skin friction co-efficient show that this surface follows a Nikuradse type inflectional curve and that Townsends outer layer similarity hypothesis is valid for rough wall flows with a large separation of scales. Mean flow and turbulence statistics will be presented.

  17. Temperature dependent surface modification of molybdenum due to low energy He{sup +} ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, J.K., E-mail: jtripat@purdue.edu [Center for Materials Under Extreme Environment (CMUXE), School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States); Novakowski, T.J.; Joseph, G. [Center for Materials Under Extreme Environment (CMUXE), School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States); Linke, J. [Forschungszentrum Jülich GmbH, EURATOM Association, Jülich D-52425 (Germany); Hassanein, A. [Center for Materials Under Extreme Environment (CMUXE), School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States)

    2015-09-15

    In this paper, we report on the temperature dependent surface modifications in molybdenum (Mo) samples due to 100 eV He{sup +} ion irradiation in extreme conditions as a potential candidate to plasma-facing components in fusion devices alternative to tungsten. The Mo samples were irradiated at normal incidence, using an ion fluence of 2.6 × 10{sup 24} ions m{sup −2} (with a flux of 7.2 × 10{sup 20} ions m{sup −2} s{sup −1}). Surface modifications have been studied using high-resolution field emission scanning electron-(SEM) and atomic force (AFM) microscopy. At 773 K target temperature homogeneous evolution of molybdenum nanograins on the entire Mo surface were observed. However, at 823 K target temperature appearance of nano-pores and pin-holes nearby the grain boundaries, and Mo fuzz in patches were observed. The fuzz density increases significantly with target temperatures and continued until 973 K. However, at target temperatures beyond 973 K, counterintuitively, a sequential reduction in the fuzz density has been seen till 1073 K temperatures. At 1173 K and above temperatures, only molybdenum nano structures were observed. Our temperature dependent studies confirm a clear temperature widow, 823–1073 K, for Mo fuzz formation. Ex-situ high resolution X-ray photoelectron spectroscopy studies on Mo fuzzy samples show the evidence of MoO{sub 3} 3d doublets. This elucidates that almost all the Mo fuzz were oxidized during open air exposure and are thick enough as well. Likewise the microscopy studies, the optical reflectivity measurements also show a sequential reduction in the reflectivity values (i.e., enhancement in the fuzz density) up to 973 K and after then a sequential enhancement in the reflectivity values (i.e., reduction in the fuzz density) with target temperatures. This is in well agreement with microscopy studies where we observed clear temperature window for Mo fuzz growth.

  18. Grain boundaries at the surface of consolidated MgO nanocrystals and acid-base functionality.

    Science.gov (United States)

    Vingurt, Dima; Fuks, David; Landau, Miron V; Vidruk, Roxana; Herskowitz, Moti

    2013-09-21

    The increase of the surface basicity-acidity of MgO material by factors of 1.8-3.0 due to consolidation of its nanocrystals was demonstrated by the indicator titration. It was shown that the parallel increase of surface acidity and basicity is attributed to the formation of grain boundaries (GB) after MgO aerogel densification. A simple model predicting the increase of surface acidity-basicity of MgO that correlates with the results of direct measurements was proposed. The model is based on the study of the fine atomic structure at GB surface areas in consolidated MgO nanocrystals in the framework of Density Functional Theory. It is found that the displacements of coordinatively unsaturated surface ions near the GB are significant at the distances ~3-4 atomic layers from the geometrical contact plane between nanocrystals. The detailed analysis of atomic positions inside GB demonstrated the coordination deficiency of surface atoms at the GB areas leading to the formation of stretched bonds and to creation of low coordinated surface ions due to splitting of coordination numbers of surface atoms belonging to GB areas. Density of states for electrons shows the existence of additional states in the band gap close to the bottom of the conduction band. The adsorption energy of CO2 molecules atop oxygen atoms exposed at surface GB areas is of the same order of magnitude as that reported for oxygen atoms at crystallographic edges and corners of MgO crystals. It provides additional options for bonding of molecules at the surface of nanocrystalline MgO increasing the adsorption capacity and catalytic activity.

  19. Determination of regional surface heat fluxes over heterogeneous landscapes by integrating satellite remote sensing with boundary layer observations

    NARCIS (Netherlands)

    Ma, Y.M.

    2006-01-01

    Keywords: satellite remote sensing, surface layer observations, atmospheric boundary layer observations, land surface variables, vegetation variables, land surface heat fluxes, validation, heterogeneous landscape, GAME/Tibet

  20. ESTIMATION OF PV MODULE SURFACE TEMPERATURE USING ARTIFICIAL NEURAL NETWORKS

    Directory of Open Access Journals (Sweden)

    Can Coskun

    2016-12-01

    Full Text Available This study aimed to use the artificial neural network (ANN method to estimate the surface temperature of a photovoltaic (PV panel. Using the experimentally obtained PV data, the accuracy of the ANN model was evaluated. To train the artificial neural network (ANN, outer temperature solar radiation and wind speed values were inputs and surface temperature was an output. The ANN was used to estimate PV panel surface temperature. Using the Levenberg-Marquardt (LM algorithm the feed forward artificial neural network was trained. Two back propagation type ANN algorithms were used and their performance was compared with the estimate from the LM algorithm. To train the artificial neural network, experimental data were used for two thirds with the remaining third used for testing. Additionally scaled conjugate gradient (SCG back propagation and resilient back propagation (RB type ANN algorithms were used for comparison with the LM algorithm. The performances of these three types of artificial neural network were compared and mean error rates of between 0.005962 and 0.012177% were obtained. The best estimate was produced by the LM algorithm. Estimation of PV surface temperature with artificial neural networks provides better results than conventional correlation methods. This study showed that artificial neural networks may be effectively used to estimate PV surface temperature.

  1. Weak solutions to the Landau-Lifshitz-Maxwell system with nonlinear Neumann boundary conditions arising from surface energies

    Directory of Open Access Journals (Sweden)

    Gilles Carbou

    2015-02-01

    Full Text Available We study the Landau-Lifshitz system associated with Maxwell equations in a bilayered ferromagnetic body when super-exchange and surface anisotropy interactions are present in the spacer in-between the layers. In the presence of these surface energies, the Neumann boundary condition becomes nonlinear. We prove, in three dimensions, the existence of global weak solutions to the Landau-Lifshitz-Maxwell system with nonlinear Neumann boundary conditions.

  2. Influence of rigid boundary on the propagation of torsional surface wave in an inhomogeneous layer

    Indian Academy of Sciences (India)

    Shishir Gupta; Rehena Sultana; Santimoy Kundu

    2015-02-01

    The present work illustrates a theoretical study on the effect of rigid boundary for the propagation of torsional surface wave in an inhomogeneous crustal layer over an inhomogeneous half space. It is believed that the inhomogeneity in the half space arises due to hyperbolic variation in shear modulus and density whereas the layer has linear variation in shear modulus and density. The dispersion equation has been obtained in a closed form by using Whittaker’s function, which shows the variation of phase velocity with corresponding wave number. Numerical results show the dispersion equations, which are discussed and presented by means of graphs. Results in some special cases are also compared with existing solutions available from analytical methods, which show a close resemblance. It is also observed that, for a layer over a homogeneous half space, the velocity of torsional waves does not coincide with that of Love waves in the presence of the rigid boundary, whereas it does at the free boundary. Graphical user interface (GUI) software has been developed using MATLAB 7.5 to generalize the effect of various parameter discussed.

  3. Precision polyimide single surface thin film shell apertures and active boundary control

    Science.gov (United States)

    Flint, Eric M.; Lindler, Jason E.; Hall, Jonathan L.; Rankine, Charles; Reggelbrugge, Mark

    2006-06-01

    This paper discusses the current status of self supporting precision membrane optical shell technology (MOST) apertures based on thin (25 to 125 um thick) polyimide and polyester films primary shell. Optically relevant doubly curved reflective apertures are realized by inducing permanent curvature into thin substrates that can then be coated. The initial thin nature provides both very low areal density (20 to 200 grams/m2) and compatibility with compact roll stowage. The induced curvature/depth provides the ability to support the shell around the periphery at discrete locations and considerable structural and dynamic stiffness. The discrete mounts also provide an excellent location with which to improve the surface figure and to reject environmental and host structure induced errors. Material microroughness on the leading substrate/coating combination has been measured to down to 3 nm rms over small (100x100um's) sample sizes with white light interferometry. A variety of reflective coated substrates have also been shown to have sub micron rms surface roughness over up to 100mm diameter test apertures using interferometric measurements. Best materials currently have 20nm rms surface roughness noise floors at these sizes. The ability to fabricate shells over a range of prescriptions (R/0.9 to R/2.2) and a range of sizes (0.1 to 0.75m diameter) has been demonstrated. Global surface figure accuracies of 2 to 4 microns rms have been demonstrated at the 0.2m size, and further improvements are anticipated through ongoing improved fabrication techniques (preliminary results indicate sub-micron rms values). The ability of discrete boundary control to improve the shape and maintain it in the face of disturbances (gravity for example) is demonstrated as is the ability to implement high amplitude (multi-wave) Zernike mode surface figure control. Results extending boundary control to interferometric optical level are also presented.

  4. On the segregation of chemical species in a clear boundary layer over heterogeneous land surfaces

    Directory of Open Access Journals (Sweden)

    H. G. Ouwersloot

    2011-07-01

    Full Text Available We have systematically studied the inability of boundary layer turbulence to efficiently mix reactive species. This creates regions where the species are accumulated in a correlated or anti-correlated way, thereby modifying the mean reactivity. Here, we quantify this modification by the intensity of segregation, IS, and analyse the driving mechanisms: heterogeneity of the surface moisture and heat fluxes, various background wind patterns and non-uniform isoprene emissions. For typical conditions in the Amazon rain forest, applying homogeneous surface forcings, the isoprene-OH reaction rate is altered by less than 10 %. This is substantially smaller than the previously assumed IS of 50 % in recent large-scale model analyses of tropical rain forest chemistry. Spatial heterogeneous surface emissions enhance the segregation of species, leading to alterations of the chemical reaction rates of up to 20 %. For these cases, spatial segregation is induced by heterogeneities of the surface properties: a cool and wet forested patch characterized by high isoprene emissions is alternated with a warm and dry patch that represents pasture with relatively low isoprene emissions. The intensities of segregation are enhanced when the background wind direction is parallel to the borders between the patches and reduced in case of a perpendicular wind direction. The effects of segregation on trace gas concentrations vary per species. For the highly reactive OH, the differences in concentration averaged over the boundary layer are less than 2 % compared to homogeneous surface conditions, while the isoprene concentration is increased by as much as 12 % due to the reduced chemical reaction rates. These processes take place at the sub-grid scale of chemistry transport models and therefore need to be parameterized.

  5. Parameterization of a surface drag coefficient in conventionally neutral planetary boundary layer

    Directory of Open Access Journals (Sweden)

    I. N. Esau

    2004-11-01

    Full Text Available Modern large-scale models (LSMs rely on surface drag coefficients to parameterize turbulent exchange between surface and the first computational level in the atmosphere. A classical parameterization in an Ekman boundary layer is rather simple. It is based on a robust concept of a layer of constant fluxes. In such a layer (log-layer, the mean velocity profile is logarithmic. It results in an universal dependence of the surface drag coefficient on a single internal non-dimensional parameter, namely the ratio of a height within this layer to a surface roughness length scale. A realistic near-neutral planetary boundary layer (PBL is usually much more shallow than the idealized Ekman layer. The reason is that the PBL is developing against a stably stratified free atmosphere. The ambient atmospheric stratification reduces the PBL depth and simultaneously the depth of the log-layer. Therefore, the first computational level in the LSMs may be placed above the log-layer. In such a case, the classical parameterization is unjustified and inaccurate.

    The paper proposes several ways to improve the classical parameterization of the surface drag coefficient for momentum. The discussion is focused on a conventionally neutral PBL, i.e. on the neutrally stratified PBL under the stably stratified free atmosphere. The analysis is based on large eddy simulation (LES data. This data reveals that discrepancy between drag coefficients predicted by the classical parameterization and the actual drag coefficients can be very large in the shallow PBL. The improved parameterizations provide a more accurate prediction. The inaccuracy is reduced to one-tenth of the actual values of the coefficients.

  6. Parameterization of a surface drag coefficient in conventionally neutral planetary boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Esau, I.N. [Nansen Environmental and Remote Sensing Center, Bergen (Norway)

    2004-07-01

    Modern large-scale models (LSMs) rely on surface drag coefficients to parameterize turbulent exchange between surface and the first computational level in the atmosphere. A classical parameterization in an Ekman boundary layer is rather simple. It is based on a robust concept of a layer of constant fluxes. In such a layer (log-layer), the mean velocity profile is logarithmic. It results in an universal dependence of the surface drag coefficient on a single internal non-dimensional parameter, namely the ratio of a height within this layer to a surface roughness length scale. A realistic near-neutral planetary boundary layer (PBL) is usually much more shallow than the idealized Ekman layer. The reason is that the PBL is developing against a stably stratified free atmosphere. The ambient atmospheric stratification reduces the PBL depth and simultaneously the depth of the log-layer. Therefore, the first computational level in the LSMs may be placed above the log-layer. In such a case, the classical parameterization is unjustified and inaccurate. The paper proposes several ways to improve the classical parameterization of the surface drag coefficient for momentum. The discussion is focused on a conventionally neutral PBL, i.e. on the neutrally stratified PBL under the stably stratified free atmosphere. The analysis is based on large eddy simulation (LES) data. This data reveals that discrepancy between drag coefficients predicted by the classical parameterization and the actual drag coefficients can be very large in the shallow PBL. The improved parameterizations provide a more accurate prediction. The inaccuracy is reduced to one-tenth of the actual values of the coefficients. (orig.)

  7. The boundary condition for vertical velocity and its interdependence with surface gas exchange

    Science.gov (United States)

    Kowalski, Andrew S.

    2017-07-01

    The law of conservation of linear momentum is applied to surface gas exchanges, employing scale analysis to diagnose the vertical velocity (w) in the boundary layer. Net upward momentum in the surface layer is forced by evaporation (E) and defines non-zero vertical motion, with a magnitude defined by the ratio of E to the air density, as w = E/ρ. This is true even right down at the surface where the boundary condition is w|0 = E/ρ|0 (where w|0 and ρ|0 represent the vertical velocity and density of air at the surface). This Stefan flow velocity implies upward transport of a non-diffusive nature that is a general feature of the troposphere but is of particular importance at the surface, where it assists molecular diffusion with upward gas migration (of H2O, for example) but opposes that of downward-diffusing species like CO2 during daytime. The definition of flux-gradient relationships (eddy diffusivities) requires rectification to exclude non-diffusive transport, which does not depend on scalar gradients. At the microscopic scale, the role of non-diffusive transport in the process of evaporation from inside a narrow tube - with vapour transport into an overlying, horizontal airstream - was described long ago in classical mechanics and is routinely accounted for by chemical engineers, but has been neglected by scientists studying stomatal conductance. Correctly accounting for non-diffusive transport through stomata, which can appreciably reduce net CO2 transport and marginally boost that of water vapour, should improve characterisations of ecosystem and plant functioning.

  8. Mathematical model of the metal mould surface temperature optimization

    Energy Technology Data Exchange (ETDEWEB)

    Mlynek, Jaroslav, E-mail: jaroslav.mlynek@tul.cz; Knobloch, Roman, E-mail: roman.knobloch@tul.cz [Department of Mathematics, FP Technical University of Liberec, Studentska 2, 461 17 Liberec, The Czech Republic (Czech Republic); Srb, Radek, E-mail: radek.srb@tul.cz [Institute of Mechatronics and Computer Engineering Technical University of Liberec, Studentska 2, 461 17 Liberec, The Czech Republic (Czech Republic)

    2015-11-30

    The article is focused on the problem of generating a uniform temperature field on the inner surface of shell metal moulds. Such moulds are used e.g. in the automotive industry for artificial leather production. To produce artificial leather with uniform surface structure and colour shade the temperature on the inner surface of the mould has to be as homogeneous as possible. The heating of the mould is realized by infrared heaters located above the outer mould surface. The conceived mathematical model allows us to optimize the locations of infrared heaters over the mould, so that approximately uniform heat radiation intensity is generated. A version of differential evolution algorithm programmed in Matlab development environment was created by the authors for the optimization process. For temperate calculations software system ANSYS was used. A practical example of optimization of heaters locations and calculation of the temperature of the mould is included at the end of the article.

  9. Heat transfer and wall temperature effects in shock wave turbulent boundary layer interactions

    Science.gov (United States)

    Bernardini, M.; Asproulias, I.; Larsson, J.; Pirozzoli, S.; Grasso, F.

    2016-12-01

    Direct numerical simulations are carried out to investigate the effect of the wall temperature on the behavior of oblique shock wave turbulent boundary layer interactions at free-stream Mach number 2.28 and shock angle of the wedge generator φ =8∘ . Five values of the wall-to-recovery-temperature ratio (Tw/Tr ) are considered, corresponding to cold, adiabatic, and hot wall thermal conditions. We show that the main effect of cooling is to decrease the characteristic scales of the interaction in terms of upstream influence and extent of the separation bubble. The opposite behavior is observed in the case of heating, which produces a marked dilatation of the interaction region. The distribution of the Stanton number shows that a strong amplification of the heat transfer occurs across the interaction, with the maximum thermal and dynamic loads found for the case of the cold wall. The analysis reveals that the fluctuating heat flux exhibits a strong intermittent behavior, characterized by scattered spots with extremely high values compared to the mean. Furthermore, the analogy between momentum and heat transfer, typical of compressible, wall-bounded, equilibrium turbulent flows, does not apply for most of the interaction domain. The premultiplied spectra of the wall heat flux do not show any evidence of the influence of the low-frequency shock motion, and the primary mechanism for the generation of peak heating is found to be linked with the turbulence amplification in the interaction region.

  10. Heat transfer and wall temperature effects in shock wave turbulent boundary layer interactions

    CERN Document Server

    Bernardini, Matteo; Pirozzoli, Sergio; Grasso, Francesco

    2016-01-01

    Direct numerical simulations are carried out to investigate the effect of the wall temperature on the behavior of oblique shock-wave/turbulent boundary layer interactions at freestream Mach number $2.28$ and shock angle of the wedge generator $\\varphi = 8^{\\circ}$. Five values of the wall-to-recovery-temperature ratio ($T_w/T_r$) are considered, corresponding to cold, adiabatic and hot wall thermal conditions. We show that the main effect of cooling is to decrease the characteristic scales of the interaction in terms of upstream influence and extent of the separation bubble. The opposite behavior is observed in the case of heating, that produces a marked dilatation of the interaction region. The distribution of the Stanton number shows that a strong amplification of the heat transfer occurs across the interaction, and the maximum values of thermal and dynamic loads are found in the case of cold wall. The analysis reveals that the fluctuating heat flux exhibits a strong intermittent behavior, characterized by ...

  11. Influence of Annealing Temperature on CZTS Thin Film Surface Properties

    Science.gov (United States)

    Feng, Wenmei; Han, Junfeng; Ge, Jun; Peng, Xianglin; Liu, Yunong; Jian, Yu; Yuan, Lin; Xiong, Xiaolu; Cha, Limei; Liao, Cheng

    2017-01-01

    In this work, copper zinc tin sulfide (CZTS) films were deposited by direct current sputtering and the samples were annealed in different oven-set temperatures and atmosphere (Ar and H2S). The surface evolution was investigated carefully by using scanning electron microscopy (SEM), Raman spectroscopy and x-ray photoelectron spectroscopy. The surface of the as-sputtered precursor contained little Cu and large amounts of Zn and Sn. The metallic precursor was continuous and compact without pinholes or cracks. With the increase of the temperature from room temperature to 250°C, Cu atoms diffused to the film surface to form Cu1- x S and covered other compounds. Some small platelets were smaller than 500 nm spreading randomly in the holes of the film surfaces. When the temperature reached 350°C, Zn and Sn atoms began to diffuse to the surface and react with S or Cu1- x S. At 400°C, SEM showed the melting of large particles and small particles with a size from 100 nm to 200 nm in the background of the film surface. Excess Zn segregated towards the surface regions and formed ZnS phase on the surface. In addition, the signal of sodium in the CZTS surface was observed above 400°C. At 600°C, a large amount of regular structures with clear edges and corners were observed in the film surface in SEM images. A clear recrystallized process on the surface was assumed from those observations.

  12. Climate Change Signal Analysis for Northeast Asian Surface Temperature

    Institute of Scientific and Technical Information of China (English)

    Jeong-Hyeong LEE; Byungsoo KIM; Keon-Tae SOHN; Won-Tae KOWN; Seung-Ki MIN

    2005-01-01

    Climate change detection, attribution, and prediction were studied for the surface temperature in the Northeast Asian region using NCEP/NCAR reanalysis data and three coupled-model simulations from ECHAM4/OPYC3, HadCM3, and CCCma GCMs (Canadian Centre for Climate Modeling and Analysis general circulation model). The Bayesian fingerprint approach was used to perform the detection and attribution test for the anthropogenic climate change signal associated with changes in anthropogenic carbon dioxide (CO2) and sulfate aerosol (SO42-) concentrations for the Northeast Asian temperature. It was shown that there was a weak anthropogenic climate change signal in the Northeast Asian temperature change. The relative contribution of CO2 and SOl- effects to total temperature change in Northeast Asia was quantified from ECHAM4/OPYC3 and CCCma GCM simulations using analysis of variance. For the observed temperature change for the period of 1959-1998, the CO2 effect contributed 10%-21% of the total variance and the direct cooling effect of SO42- played a less important role (0% 7%) than the CO2effect. The prediction of surface temperature change was estimated from the second CO2+SO24- scenario run of ECHAM4/OPYC3 which has the least error in the simulation of the present-day temperature field near the Korean Peninsula. The result shows that the area-mean surface temperature near the Korean Peninsula will increase by about 1.1° by the 2040s relative to the 1990s.

  13. Laboratory investigations of the heat and momentum transfer in the stably stratified air turbulent boundary layer above the wavy surface

    Science.gov (United States)

    Sergeev, Daniil; Troitskaya, Yuliya; Vdovin, Maxim

    2015-04-01

    Investigation of small scale transfer processes between the ocean and atmosphere in the boundary and its parameterization on the meteorological conditions (wind and surface waves parameters) is very important for weather forecasts modeling [1]. The accuracy of the predictions taking in to account the so named bulk-formulas strongly depends on the quality empirical data. That is why the laboratory modeling sometimes is preferable (see [2]) then in situ measurements for obtaining enough ensembles of the data with a good accuracy in control conditions, first of all in a case of severe conditions (strong winds with intensive wave breaking and sprays generation). In this investigation laboratory modeling was performed on the Thermostratified Wind-Wave Channel of the IAP RAS (see. [3]). Experiments were carried out for the wind speeds up to 18.5 m/s (corresponding the equivalent 10-m wind speed 30 m/s). For the possibility of varying parameters of surface roughness independently on the wind flow a special system basing on the submerged mosquito mesh (cell of 2*2 mm) was used (see [4]). The roughness was controlled by the depth of the mesh installation under the free surface (no waves when the mesh was on the surface and maximum wave amplitude for the maximum depth). So, for each wind speed several cases of the waves parameters were investigated. During experiments a stable stratification of the boundary layer of air flow was obtained. Temperature of the heating air was 33-37 degrees (depending on the reference wind speed), and the water temperature was 14-16 degrees. The Pitote gauge and hotwire were used together for measuring velocity and temperature profiles. Also indirect estimations of the total volume of the phase of sprays were obtained by analyzing hotwire signals errors during droplets hits. Then aerodynamic drag CD and heat transfer Ch coefficients were obtained by profiling method. It was shown that that these parameters are very sensitive to the intensity of

  14. Long-Term Record of Arctic and Antarctic Sea and Ice Surface Temperatures from Thermal Infrared Satellite Sensors

    Science.gov (United States)

    Luis, Cristina; Dybkjær, Gorm; Eastwood, Steinar; Tonboe, Rasmus; Høyer, Jacob

    2015-04-01

    Surface temperature is among the most important variables in the surface energy balance equation and it significantly affects the atmospheric boundary layer structure, the turbulent heat exchange and, over ice, the ice growth rate. Here we measure the surface temperature using thermal infrared sensors from 10-12 µm wavelength, a method whose primary limitation over sea ice is the detection of clouds. However, in the Arctic and around Antarctica there are very few conventional observations of surface temperature from buoys, and it is sometimes difficult to determine if the temperature is measured at the surface or within the snowpack, the latter of which often results in a warm bias. To reduce this bias, much interest is being paid to alternative remote sensing methods for monitoring high latitude surface temperature. We used Advanced Very High Resolution Radiometer (AVHRR) global area coverage (GAC) data to produce a high latitude sea surface temperature (SST), ice surface temperature (IST) and ice cap skin temperature dataset spanning 27 years (1982-2009). This long-term climate record is the first of its kind for IST. In this project we used brightness temperatures from the infrared channels of AVHRR sensors aboard NOAA and Metop polar-orbiting satellites. Surface temperatures were calculated using separate split window algorithms for day SST, night SST, and IST. The snow surface emissivity across all angles of the swath were simulated specifically for all sensors using an emission model. Additionally, all algorithms were tuned to the Arctic using simulated brightness temperatures from a radiative transfer model with atmospheric profiles and skin temperatures from European Centre for Medium-Range Forecasts (ECMWF) re-analysis data (ERA-Interim). Here we present the results of product quality as compared to in situ measurements from buoys and infrared radiometers, as well as a preliminary analysis of climate trends revealed by the record.

  15. Comparison of MODIS Land Surface Temperature and Air Temperature over the Continental USA Meteorological Stations

    Science.gov (United States)

    Zhang, Ping; Bounoua, Lahouari; Imhoff, Marc L.; Wolfe, Robert E.; Thome, Kurtis

    2014-01-01

    The National Land Cover Database (NLCD) Impervious Surface Area (ISA) and MODIS Land Surface Temperature (LST) are used in a spatial analysis to assess the surface-temperature-based urban heat island's (UHIS) signature on LST amplitude over the continental USA and to make comparisons to local air temperatures. Air-temperature-based UHIs (UHIA), calculated using the Global Historical Climatology Network (GHCN) daily air temperatures, are compared with UHIS for urban areas in different biomes during different seasons. NLCD ISA is used to define urban and rural temperatures and to stratify the sampling for LST and air temperatures. We find that the MODIS LST agrees well with observed air temperature during the nighttime, but tends to overestimate it during the daytime, especially during summer and in nonforested areas. The minimum air temperature analyses show that UHIs in forests have an average UHIA of 1 C during the summer. The UHIS, calculated from nighttime LST, has similar magnitude of 1-2 C. By contrast, the LSTs show a midday summer UHIS of 3-4 C for cities in forests, whereas the average summer UHIA calculated from maximum air temperature is close to 0 C. In addition, the LSTs and air temperatures difference between 2006 and 2011 are in agreement, albeit with different magnitude.

  16. New expressions for the surface roughness length and displacement height in the atmospheric boundary layer

    Institute of Scientific and Technical Information of China (English)

    Lin Jian-Zhong; Li Hui-Jun; Zhang Kai

    2007-01-01

    An alternative model for the prediction of surface roughness length is developed. In the model a new factor is introduced to compensate for the effects of wake diffusion and interactions between the wake and roughness obstacles.The experiments are carried out by the use of the hot wire anemometry in the simulated atmospheric boundary layer in a wind tunnel. Based on the experimental data, a new expression for the zero-plane displacement height is proposed for the square arrays of roughness elements, which highlights the influence of free-stream speed on the roughness length. It appears that the displacement height increases with the wind speed while the surface roughness length decreases with Reynolds number increasing. It is shown that the calculation results based on the new expressions are in reasonable agreement with the experimental data.

  17. Surface layer similarity in the nocturnal boundary layer: the application of Hilbert-Huang transform

    Directory of Open Access Journals (Sweden)

    J. Hong

    2009-10-01

    Full Text Available Turbulence statistics such as flux-variance relationship is critical information in measuring and modeling carbon, water, energy, and momentum exchanges at the biosphere-atmosphere interface. Using a recently proposed mathematical technique, the Hilbert-Huang transform (HHT, this study highlights its possibility to quantify impacts of non-turbulent flows on turbulence statistics in the stable surface layer. The HHT is suitable for the analysis of non-stationary and intermittent data and thus very useful for better understanding of the interplay of the surface layer similarity with complex nocturnal environment. Our analysis showed that the HHT can successfully sift non-turbulent components and be used as a tool to estimate the relationships between turbulence statistics and atmospheric stability in complex environment such as nocturnal stable boundary layer.

  18. Surface layer similarity in the nocturnal boundary layer: the application of Hilbert-Huang transform

    Directory of Open Access Journals (Sweden)

    J. Hong

    2010-04-01

    Full Text Available Turbulence statistics such as flux-variance relationship are critical information in measuring and modeling ecosystem exchanges of carbon, water, energy, and momentum at the biosphere-atmosphere interface. Using a recently proposed mathematical technique, the Hilbert-Huang transform (HHT, this study highlights its possibility to quantify impacts of non-turbulent flows on turbulence statistics in the stable surface layer. The HHT is suitable for the analysis of non-stationary and intermittent data and thus very useful for better understanding the interplay of the surface layer similarity with complex nocturnal environment. Our analysis showed that the HHT can successfully sift non-turbulent components and be used as a tool to estimate the relationships between turbulence statistics and atmospheric stability in complex environments such as nocturnal stable boundary layer.

  19. A rigid surface boundary element for soil-structure interaction analysis in the direct time domain

    Science.gov (United States)

    Rizos, D. C.

    Many soil-structure interaction problems involve studies of single or multiple rigid bodies of arbitrary shape and soil media. The commonly used boundary element methods implement the equations of the rigid body in a form that depends on the particulars of the geometry and requires partitioning and condensation of the associated algebraic system of equations. The present work employs the direct time domain B-Spline BEM for 3D elastodynamic analysis and presents an efficient implementation of rigid bodies of arbitrary shape in contact with, or embedded in, elastic media. The formulation of a rigid surface boundary element introduced herein is suitable for direct superposition in the BEM system of algebraic equations. Consequently, solutions are computed in a single analysis step, eliminating, thus, the need for partitioning of the system of equations. Computational efficiency is also achieved due to the extremely sparse form of the associated coefficient matrices. The proposed element can be used for the modeling of single or multiple rigid bodies of arbitrary shape within the framework of the BEM method. The efficiency and general nature of the proposed element is demonstrated through applications related to the dynamic analysis of rigid surface and embedded foundations and their interaction with embedded rigid bodies of arbitrary shape.

  20. Drag reduction by means of dimpled surfaces in turbulent boundary layers

    Science.gov (United States)

    van Nesselrooij, M.; Veldhuis, L. L. M.; van Oudheusden, B. W.; Schrijer, F. F. J.

    2016-09-01

    Direct force measurements and particle image velocimetry (PIV) were used to investigate the drag and flow structure caused by surfaces with patterns of shallow spherical dimples with rounded edges subject to turbulent boundary layers. Drag reduction of up to 4 % is found compared to a flat surface. The largest drag reduction was found at the highest tested Reynolds number of 40,000 (based on dimple diameter). A favorable trend promises further improvements at higher Reynolds numbers. PIV revealed the absence of significant separation inside the dimples but did show the existence of a converging/diverging flow in the upstream and downstream dimple half, respectively. This leads to the rejection of theories proposed by other authors concerning the mechanism responsible for drag reduction. Instead, a fundamental dependence on pattern orientation is observed. Furthermore, preliminary Reynolds-averaged Navier-Stokes (RANS) simulations have been compared with the PIV data. Although the large-scale mean flows show good agreement, the numerical simulation predicts no drag reduction. As the RANS approach is inherently incapable of resolving effects on the behavior of small-scale turbulence structure, the origin of drag reduction is attributed to effects on the small-scale turbulence, which is not resolved in the simulations. It is argued that dimples, when placed in well-designed patterns to create the necessary large-scale flow structure, lead to drag reduction by affecting the turbulent structures in the boundary layer, possibly in a way similar to spanwise oscillations of the wall.

  1. Molecular kinetic theory of boundary slip on textured surfaces by molecular dynamics simulations

    Science.gov (United States)

    Wang, LiYa; Wang, FengChao; Yang, FuQian; Wu, HengAn

    2014-11-01

    A theoretical model extended from the Frenkel-Eyring molecular kinetic theory (MKT) was applied to describe the boundary slip on textured surfaces. The concept of the equivalent depth of potential well was adopted to characterize the solid-liquid interactions on the textured surfaces. The slip behaviors on both chemically and topographically textured surfaces were investigated using molecular dynamics (MD) simulations. The extended MKT slip model is validated by our MD simulations under various situations, by constructing different complex surfaces and varying the surface wettability as well as the shear stress exerted on the liquid. This slip model can provide more comprehensive understanding of the liquid flow on atomic scale by considering the influence of the solid-liquid interactions and the applied shear stress on the nano-flow. Moreover, the slip velocity shear-rate dependence can be predicted using this slip model, since the nonlinear increase of the slip velocity under high shear stress can be approximated by a hyperbolic sine function.

  2. Molecular kinetic theory of boundary slip on textured surfaces by molecular dynamics simulations

    Institute of Scientific and Technical Information of China (English)

    WANG LiYa; WANG FengChao; YANG FuQian; WU HengAn

    2014-01-01

    A theoretical model extended from the Frenkel-Eyring molecular kinetic theory (MKT) was applied to describe the boundary slip on textured surfaces.The concept of the equivalent depth of potential well was adopted to characterize the solid-liquid interactions on the textured surfaces.The slip behaviors on both chemically and topographically textured surfaces were investigated using molecular dynamics (MD) simulations.The extended MKT slip model is validated by our MD simulations under various situations,by constructing different complex surfaces and varying the surface wettability as well as the shear stress exerted on the liquid.This slip model can provide more comprehensive understanding of the liquid flow on atomic scale by considering the influence of the solid-liquid interactions and the applied shear stress on the nano-flow.Moreover,the slip velocity shear-rate dependence can be predicted using this slip model,since the nonlinear increase of the slip velocity under high shear stress can be approximated by a hyperbolic sine function.

  3. Fiber-Optic Surface Temperature Sensor Based on Modal Interference

    Directory of Open Access Journals (Sweden)

    Frédéric Musin

    2016-07-01

    Full Text Available Spatially-integrated surface temperature sensing is highly useful when it comes to controlling processes, detecting hazardous conditions or monitoring the health and safety of equipment and people. Fiber-optic sensing based on modal interference has shown great sensitivity to temperature variation, by means of cost-effective image-processing of few-mode interference patterns. New developments in the field of sensor configuration, as described in this paper, include an innovative cooling and heating phase discrimination functionality and more precise measurements, based entirely on the image processing of interference patterns. The proposed technique was applied to the measurement of the integrated surface temperature of a hollow cylinder and compared with a conventional measurement system, consisting of an infrared camera and precision temperature probe. As a result, the optical technique is in line with the reference system. Compared with conventional surface temperature probes, the optical technique has the following advantages: low heat capacity temperature measurement errors, easier spatial deployment, and replacement of multiple angle infrared camera shooting and the continuous monitoring of surfaces that are not visually accessible.

  4. Assessment of broiler surface temperature variation when exposed to different air temperatures

    Directory of Open Access Journals (Sweden)

    GR Nascimento

    2011-12-01

    Full Text Available This study was conducted to determine the effect of the air temperature variation on the mean surface temperature (MST of 7- to 35-day-old broiler chickens using infrared thermometry to estimate MST, and to study surface temperature variation of the wings, head, legs, back and comb as affected by air temperature and broiler age. One hundred Cobb® broilers were used in the experiment. Starting on day 7, 10 birds were weekly selected at random, housed in an environmental chamber and reared under three distinct temperatures (18, 25 and 32 ºC to record their thermal profile using an infrared thermal camera. The recorded images were processed to estimate MST by selecting the whole area of the bird within the picture and comparing it with the values obtained using selected equations in literature, and to record the surface temperatures of the body parts. The MST estimated by infrared images were not statistically different (p > 0.05 from the values obtained by the equations. MST values significantly increased (p < 0.05 when the air temperature increased, but were not affected by bird age. However, age influenced the difference between MST and air temperature, which was highest on day 14. The technique of infrared thermal image analysis was useful to estimate the mean surface temperature of broiler chickens.

  5. UAS and DTS: Using Drones and Fiber Optics to Measure High Resolution Temperature of the Atmospheric Boundary Layer

    Science.gov (United States)

    Predosa, R. A.; Darricau, B.; Higgins, C. W.

    2015-12-01

    The atmospheric boundary layer (ABL) is the lowest part of the atmosphere that directly interacts with the planet's surface. The development of the ABL plays a vital role, as it affects the transport of atmospheric constituents such as air pollutants, water vapor, and greenhouse gases. Measurements of the processes in the ABL have been difficult due to the limitations in the spatial and temporal resolutions of the equipment as well as the height of the traditional flux tower. Recent advances in the unmanned aerial vehicle (UAV) and distributed temperature sensing (DTS) technologies have provided us with new tools to study the complex processes in ABL. We conducted a series of pioneering experiments in Eastern Oregon using a platform that combines UAV and DTS to collect data during morning and evening transitions in the ABL. The major components of this platform consists of a quad-copter, a DTS computer unit, and a set of customized fiber optic cables. A total of 75 flights were completed to investigate: (1) the capability of a duplexed fiber optic cable to reduce noise in the high spatial and temporal temperature measurements taken during the morning transition; (2) the possibility of using fiber optic cable as "wet bulb" thermometer to calculate relative humidity in the ABL at high spatial and temporal resolution. The preliminary results showed that using a fiber optic cable in a duplexed configuration with the UAV-DTS platform can effectively reduce noise level during the morning transition data collection. The customized "wet bulb" fiber optic cable is capable of providing information for the calculation of relative humidity in the ABL at unprecedented spatial and temporal resolutions. From this study, the UAV-DTS platform demonstrated great potential in collecting temperature data in the ABL and with the development of atmospheric sensor technologies, it will have more applications in the future.

  6. Investigating the effect of surface water - groundwater interactions on stream temperature using Distributed temperature sensing and instream temperature model

    DEFF Research Database (Denmark)

    Karthikeyan, Matheswaran; Blemmer, Morten; Mortensen, Julie Flor;

    2011-01-01

    Surface water–groundwater interactions at the stream interface influences, and at times controls the stream temperature, a critical water property driving biogeochemical processes. This study investigates the effects of these interactions on temperature of Stream Elverdamsåen in Denmark using...... the Distributed Temperature Sensing (DTS) system and instream temperature modelling. Locations of surface water–groundwater interactions were identified from the temperature data collected over a 2-km stream reach using a DTS system with 1-m spatial and 5-min temporal resolution. The stream under consideration...... exhibits three distinct thermal regimes within a 2 km reach length due to two major interactions. An energy balance model is used to simulate the instream temperature and to quantify the effect of these interactions on the stream temperature. This research demonstrates the effect of reach level small scale...

  7. Effects of Thermal Radiation and Chemical Reaction on MHD Free Convection Flow past a Flat Plate with Heat Source and Convective Surface Boundary Condition

    Directory of Open Access Journals (Sweden)

    E.Hemalatha

    2015-09-01

    Full Text Available This paper analyzes the radiation and chemical reaction effects on MHD steady two-dimensional laminar viscous incompressible radiating boundary layer flow over a flat plate in the presence of internal heat generation and convective boundary condition. It is assumed that lower surface of the plate is in contact with a hot fluid while a stream of cold fluid flows steadily over the upper surface with a heat source that decays exponentially. The Rosseland approximation is used to describe radiative heat transfer as we consider optically thick fluids. The governing boundary layer equations are transformed into a system of ordinary differential equations using similarity transformations, which are then solved numerically by employing fourth order Runge-Kutta method along with shooting technique. The effects of various material parameters on the velocity, temperature and concentration as well as the skin friction coefficient, the Nusselt number, the Sherwood number and the plate surface temperature are illustrated and interpreted in physical terms. A comparison of present results with previously published results shows an excellent agreement.

  8. Boundary conditions at the walls with thermionic electron emission in two temperature modeling of “thermal” plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Pekker, Leonid; Hussary, Nakhleh [Victor Technologies, West Lebanon, New Hampshire 03781 (United States)

    2015-08-15

    In this paper, we propose new boundary conditions for the electric potential, the electron energy equation, and the energy equation for heavy particles (ions and neutrals) at the hot walls with thermionic electron emission for two-temperature thermal arc models. The derived boundary conditions assume that the walls are made from refractory metals and, consequently, the erosion of the wall is small and can be neglected. In these boundary conditions, the plasma sheath formed at the electrode is viewed as the interface between the plasma and the wall. The derived boundary conditions allow the calculation of the heat flux to the walls from the plasma. This allows the calculation of the thermionic electron current that makes the model of electrode-plasma interaction self-consistent.

  9. The effect of high temperature induced variation of specific heat on the hypersonic turbulent boundary layer and its computation

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    For hypersonic vehicles,as the temperature in its boundary layer usually exceeds 600 K,for which the molecular vibrational degree of freedom is excited,the perfect gas model is no longer valid.In this paper,the effect of high temperature induced variation of specific heat on the hypersonic turbulent boundary layer of flat plates is investigated by direct numerical simulations with the perfect gas model,i.e.with constant specific heat,as well as with a variable specific heat gas model.The comparison of the results from the two gas models has found that the effect of the variation of specific heat on the velocity of the turbulent boundary layers is relatively small,while its effect on temperature,such as the mean temperature,the temperature fluctuations,is appreciable.It is also found that the mean specific heat is quite close to the specific heat calculated by using the mean temperature,indicating that it is possible to do turbulence modeling.The modeling is done under the variable specific heat gas model with the mean temperature as the variable.The feasibility of such consideration is verified by applying the SST model for variable specific heat turbulence computation.

  10. Uncertainties and shortcomings of ground surface temperature histories derived from inversion of temperature logs

    OpenAIRE

    Hartmann, Andreas; Rath, Volker

    2008-01-01

    Analysing borehole temperature data in terms of ground surface history can add useful information to reconstructions of past climates. Therefore, a rigorous assessment of uncertainties and error sources is a necessary prerequisite for the meaningful interpretation of such ground surface temperature histories. This study analyses the most prominent sources of uncertainty. The diffusive nature of the process makes the inversion relatively robust against incomplete knowledge of the thermal diffu...

  11. Boundary|Time|Surface: Art and Geology Meet in Gros Morne National Park, NL, Canada

    Science.gov (United States)

    Lancaster, Sydney; Waldron, John

    2015-04-01

    Environmental Art works range in scope from major permanent interventions in the landscape to less intrusive, more ephemeral site-specific installations constructed of materials from the local environment. Despite this range of intervention, however, these works all share in a tradition of art making that situates the artwork in direct response to the surrounding landscape. Andy Goldsworthy and Richard Long, for example, both favour methods that combine elements of both sculpture and performance in the creation of non-permanent interventions in the landscape, and both rely upon photographic, text-based, or video documentation as the only lasting indication of the works' existence. Similarly, Earth Scientists are responsible for interventions in the landscape, both physical and conceptual. For example, in Earth science, the periods of the geologic timescale - Cambrian, Ordovician, Silurian, etc. - were established by 19th century pioneers of geology at a time when they were believed to represent natural chapters in Earth history. Since the mid-20th century, stratigraphers have attempted to resolve ambiguities in the original definitions by defining stratotypes: sections of continuously deposited strata where a single horizon is chosen as a boundary. One such international stratotype, marking the Cambrian-Ordovician boundary, is defined at Green Point in Gros Morne National Park, Newfoundland. Boundary|Time|Surface was an ephemeral sculptural installation work constructed in June 2014. The main installation work was a fence of 52 vertical driftwood poles, 2-3 m tall, positioned precisely along the boundary stratotype horizon at Green Point in Newfoundland. The fence extended across a 150 m wave-cut platform from sea cliffs to the low-water mark, separating Ordovician from Cambrian strata. The installation was constructed by hand (with volunteer assistance) on June 22, as the wave-cut platform was exposed by the falling tide. During the remainder of the tidal cycle

  12. Variability in the coupling between sea surface temperature and wind stress in the global coastal ocean

    Science.gov (United States)

    Wang, Yuntao; Castelao, Renato M.

    2016-08-01

    Mesoscale ocean-atmosphere interaction between sea surface temperature (SST) and wind stress throughout the global coastal ocean was investigated using 7 years of satellite observations. Coupling coefficients between crosswind SST gradients and wind stress curl and between downwind SST gradients and wind stress divergence were used to quantify spatial and temporal variability in the strength of the interaction. The use of a consistent data set and standardized methods allow for direct comparisons between coupling coefficients in the different coastal regions. The analysis reveals that strong coupling is observed in many mid-latitude regions throughout the world, especially in regions with strong fronts like Eastern and Western Boundary Currents. Most upwelling regions in Eastern Boundary Currents are characterized by strong seasonal variability in the strength of the coupling, which generally peaks during summer in mid latitudes and during winter at low latitudes. Seasonal variability in coastal regions along Western Boundary Currents is comparatively smaller. Intraseasonal variability is especially important in regions of strong eddy activity (e.g., Western Boundary Currents), being particularly relevant for the coupling between crosswind SST gradients and wind stress curl. Results from the analysis can be used to guide modeling studies, since it allows for the a priori identification of regions in which regional models need to properly represent the ocean-atmosphere interaction to accurately represent local variability.

  13. Measurements of Multi-Layer Insulation at High Boundary Temperature, using a Simple Non-Calorimetric Method

    CERN Document Server

    Mazzone, L; Rieubland, Jean Michel; Vandoni, Giovanna

    2002-01-01

    In spite of abundant literature, the thermal performance of Multi-Layer Insulation (MLI) still deserves dedicated investigation for specific applications, as the achievable insulation strongly depends on installation details. Furthermore, less accurate information is available for warm than for cold boundaries, since errors due to edge effects in small test benches increase strongly with warm boundary temperature. We establish here the thermal performance of MLI between 300 K and 77 K or 4 K, without bringing calorimetric methods into play, through the accurate measurement of a temperature profile. A cylinder in thin copper, wrapped with MLI, is cooled at one extremity while suspended under vacuum inside a sheath at room temperature. For known thermal conductivity and thickness of the tube, the heat flux can be inferred from the temperature profile. In-situ measurement of the thermal conductivity is obtained by applying a know heat flow at the warm extremity of the cylinder. Results, cross-checked with a cali...

  14. Estimation of Surface Temperature and Heat Flux by Inverse Heat Transfer Methods Using Internal Temperatures Measured While Radiantly Heating a Carbon/Carbon Specimen up to 1920 F

    Science.gov (United States)

    Pizzo, Michelle; Daryabeigi, Kamran; Glass, David

    2015-01-01

    The ability to solve the heat conduction equation is needed when designing materials to be used on vehicles exposed to extremely high temperatures; e.g. vehicles used for atmospheric entry or hypersonic flight. When using test and flight data, computational methods such as finite difference schemes may be used to solve for both the direct heat conduction problem, i.e., solving between internal temperature measurements, and the inverse heat conduction problem, i.e., using the direct solution to march forward in space to the surface of the material to estimate both surface temperature and heat flux. The completed research first discusses the methods used in developing a computational code to solve both the direct and inverse heat transfer problems using one dimensional, centered, implicit finite volume schemes and one dimensional, centered, explicit space marching techniques. The developed code assumed the boundary conditions to be specified time varying temperatures and also considered temperature dependent thermal properties. The completed research then discusses the results of analyzing temperature data measured while radiantly heating a carbon/carbon specimen up to 1920 F. The temperature was measured using thermocouple (TC) plugs (small carbon/carbon material specimens) with four embedded TC plugs inserted into the larger carbon/carbon specimen. The purpose of analyzing the test data was to estimate the surface heat flux and temperature values from the internal temperature measurements using direct and inverse heat transfer methods, thus aiding in the thermal and structural design and analysis of high temperature vehicles.

  15. High-Temperature Surface-Acoustic-Wave Transducer

    Science.gov (United States)

    Zhao, Xiaoliang; Tittmann, Bernhard R.

    2010-01-01

    Aircraft-engine rotating equipment usually operates at high temperature and stress. Non-invasive inspection of microcracks in those components poses a challenge for the non-destructive evaluation community. A low-profile ultrasonic guided wave sensor can detect cracks in situ. The key feature of the sensor is that it should withstand high temperatures and excite strong surface wave energy to inspect surface/subsurface cracks. As far as the innovators know at the time of this reporting, there is no existing sensor that is mounted to the rotor disks for crack inspection; the most often used technology includes fluorescent penetrant inspection or eddy-current probes for disassembled part inspection. An efficient, high-temperature, low-profile surface acoustic wave transducer design has been identified and tested for nondestructive evaluation of structures or materials. The development is a Sol-Gel bismuth titanate-based surface-acoustic-wave (SAW) sensor that can generate efficient surface acoustic waves for crack inspection. The produced sensor is very thin (submillimeter), and can generate surface waves up to 540 C. Finite element analysis of the SAW transducer design was performed to predict the sensor behavior, and experimental studies confirmed the results. One major uniqueness of the Sol-Gel bismuth titanate SAW sensor is that it is easy to implement to structures of various shapes. With a spray coating process, the sensor can be applied to surfaces of large curvatures. Second, the sensor is very thin (as a coating) and has very minimal effect on airflow or rotating equipment imbalance. Third, it can withstand temperatures up to 530 C, which is very useful for engine applications where high temperature is an issue.

  16. Investigation of surface properties of high temperature nitrided titanium alloys

    Directory of Open Access Journals (Sweden)

    E. Koyuncu

    2009-12-01

    Full Text Available Purpose: The purpose of paper is to investigate surface properties of high temperature nitrided titanium alloys.Design/methodology/approach: In this study, surface modification of Ti6Al4V titanium alloy was made at various temperatures by plasma nitriding process. Plasma nitriding treatment was performed in 80% N2-20% H2 gas mixture, for treatment times of 2-15 h at the temperatures of 700-1000°C. Surface properties of plasma nitrided Ti6Al4V alloy were examined by metallographic inspection, X-Ray diffraction and Vickers hardness.Findings: Two layers were determined by optic inspection on the samples that were called the compound and diffusion layers. Compound layer contain TiN and Ti2N nitrides, XRD results support in this formations. Maximum hardness was obtained at 10h treatment time and 1000°C treatment temperature. Micro hardness tests showed that hardness properties of the nitrided samples depend on treatment time and temperature.Practical implications: Titanium and its alloys have very attractive properties for many industries. But using of titanium and its alloys is of very low in mechanical engineering applications because of poor tribological properties.Originality/value: The nitriding of titanium alloy surfaces using plasma processes has already reached the industrial application stage in the biomedical field.

  17. Surface Intermediates on Metal Electrodes at High Temperature

    DEFF Research Database (Denmark)

    Zachau-Christiansen, Birgit; Jacobsen, Torben; Bay, Lasse

    1997-01-01

    The mechanisms widely suggested for the O2-reduc-tion or H2-oxidation SOFC reactions involve inter-mediate O/H species adsorbed on the electrode surface. The presence of these intermediates is investigated by linear sweep voltammetry. In airat moderate temperatures (500øC) Pt in contact with YSZ ...... is covered with adsorbed oxygen which vanishes at high temperature (1000øC). On Ni (YSZ) a specific layer of NiO is observed abovethe equilibrium potential while no surface species can identified at SOFC anode conditions....

  18. Determination of sea surface temperatures from microwave and IR data

    Science.gov (United States)

    Rangaswamy, S.; Grover, J.

    1982-01-01

    Microwave measurements from the Nimbus 7 SMMR were used to derive the atmospheric precipitable water, which was then used to obtain the atmospheric correction for use with AVHRR thermal IR measurements to obtain sea surface temperature (SST). The resulting SST's were compared with the NOAA operational sea surface temperature measurements, and the two sets of measurements were found to be in reasonable agreement. The average residuals between the two sets of measurements was 0.15 K with the NOAA operational SST's being slightly greater.

  19. Surface intermediates on metal electrodes at high temperatures

    DEFF Research Database (Denmark)

    Zachau-Christiansen, Birgit; Jacobsen, Torben; Bay, Lasse;

    1998-01-01

    in contact with YSZ is covered with adsorbed oxygen which vanishes at high temperature (1000 degrees C). On Ni (YSZ) a specific layer of NiO is observed above the equilibrium potential while no surface species involving hydrogen can be identified at SOFC anode conditions. (C) 1998 Published by Elsevier......The mechanisms widely conceived for the O(2)-reduction or H(2)-oxidation reactions in SOFC's involve intermediate O/H species adsorbed on the electrode surface. The presence of these intermediates is investigated by linear sweep voltammetry. In air at moderate temperatures (500 degrees C) Pt...

  20. Surface air temperature variability in global climate models

    CERN Document Server

    Davy, Richard

    2012-01-01

    New results from the Coupled Model Inter-comparison Project phase 5 (CMIP5) and multiple global reanalysis datasets are used to investigate the relationship between the mean and standard deviation in the surface air temperature. A combination of a land-sea mask and orographic filter were used to investigate the geographic region with the strongest correlation and in all cases this was found to be for low-lying over-land locations. This result is consistent with the expectation that differences in the effective heat capacity of the atmosphere are an important factor in determining the surface air temperature response to forcing.

  1. The role of atmospheric boundary layer-surface interactions on the development of coastal fronts

    Directory of Open Access Journals (Sweden)

    D. Malda

    2007-03-01

    Full Text Available Frictional convergence and thermal difference between land and sea surface are the two surface conditions that govern the intensity and evolution of a coastal front. By means of the mesoscale model MM5, we investigate the influence of these two processes on wind patterns, temperature and precipitation amounts, associated with a coastal front, observed on the west coast of The Netherlands in the night between 12 and 13 August 2004. The mesoscale model MM5 is further compared with available observations and the results of two operational models (ECMWF and HIRLAM. HIRLAM is not capable to reproduce the coastal front, whereas ECMWF and MM5 both calculate precipitation for the coastal region. The precipitation pattern, calculated by MM5, agrees satisfactorily with the accumulated radar image. The failure of HIRLAM is mainly due to a different stream pattern at the surface and consequently, a different behaviour of the frictional convergence at the coastline.

    The sensitivity analysis of frictional convergence is carried out with the MM5 model, by varying land surface roughness length (z0. For the sensitivity analysis of thermal difference between sea and land surface, we changed the sea surface temperature (SST. Increasing surface roughness implies stronger convergence near the surface and consequently stronger upward motions and intensification of the development of the coastal front. Setting land surface roughness equal to the sea surface roughness means an elimination of frictional convergence and results in a diminishing coastal front structure of the precipitation pattern. The simulation with a high SST produces much precipitation above the sea, but less precipitation in the coastal area above land. A small increment of the SST results in larger precipitation amounts above the sea; above land increments are calculated for areas near the coast. A decrease of the SST shifts the precipitation maxima inland, although the

  2. The effect of temperature on the boundary of polymer melts in the modeling of two-layers flow

    Science.gov (United States)

    Bondarenko, A. V.; Kozitsyna, M. V.; Trufanova, N. M.

    2016-10-01

    The article is devoted to determine the velocity fields, temperatures and boundary flows of bi layers of polymer coating when both of them are applied simultaneously. The mathematical model of the flow was developed using finite - elements method with was the part of Ansys Cfx software packet.

  3. Observing the Agulhas Current with sea surface temperature and altimetry data: challenges and perspectives

    CSIR Research Space (South Africa)

    Krug, Marjolaine, J

    2014-06-01

    Full Text Available -Red Sea Surface Temperature datasets still suffer from inadequate cloud masking algorithms, particularly in regions of strong temperature gradient. Despite both Sea Surface Height and Sea Surface Temperature observations being severely compromised...

  4. Influences of the boundary layer evolution on surface ozone variations at a tropical rural site in India

    Indian Academy of Sciences (India)

    K K Reddy; M Naja; N Ojha; P Mahesh; S Lal

    2012-08-01

    Collocated measurements of the boundary layer evolution and surface ozone, made for the first time at a tropical rural site (Gadanki 13.5°N, 79.2°E, 375 m amsl) in India, are presented here. The boundary layer related observations were made utilizing a lower atmospheric wind profiler and surface ozone observations were made using a UV analyzer simultaneously in April month. Daytime average boundary layer height varied from 1.5 km (on a rainy day) to a maximum of 2.5 km (on a sunny day). Correlated day-to-day variability in the daytime boundary layer height and ozone mixing ratios is observed. Days of higher ozone mixing ratios are associated with the higher boundary layer height and vice versa. It is shown that higher height of the boundary layer can lead to the mixing of near surface air with the ozone rich air aloft, resulting in the observed enhancements in surface ozone. A chemical box model simulation indicates about 17% reduction in the daytime ozone levels during the conditions of suppressed PBL in comparison with those of higher PBL conditions. On a few occasions, substantially elevated ozone levels (as high as 90 ppbv) were observed during late evening hours, when photochemistry is not intense. These events are shown to be due to southwesterly wind with uplifting and northeasterly winds with downward motions bringing ozone rich air from nearby urban centers. This was further corroborated by backward trajectory simulations.

  5. The Land Surface Temperature Impact to Land Cover Types

    Science.gov (United States)

    Ibrahim, I.; Abu Samah, A.; Fauzi, R.; Noor, N. M.

    2016-06-01

    Land cover type is an important signature that is usually used to understand the interaction between the ground surfaces with the local temperature. Various land cover types such as high density built up areas, vegetation, bare land and water bodies are areas where heat signature are measured using remote sensing image. The aim of this study is to analyse the impact of land surface temperature on land cover types. The objectives are 1) to analyse the mean temperature for each land cover types and 2) to analyse the relationship of temperature variation within land cover types: built up area, green area, forest, water bodies and bare land. The method used in this research was supervised classification for land cover map and mono window algorithm for land surface temperature (LST) extraction. The statistical analysis of post hoc Tukey test was used on an image captured on five available images. A pixel-based change detection was applied to the temperature and land cover images. The result of post hoc Tukey test for the images showed that these land cover types: built up-green, built up-forest, built up-water bodies have caused significant difference in the temperature variation. However, built up-bare land did not show significant impact at p<0.05. These findings show that green areas appears to have a lower temperature difference, which is between 2° to 3° Celsius compared to urban areas. The findings also show that the average temperature and the built up percentage has a moderate correlation with R2 = 0.53. The environmental implications of these interactions can provide some insights for future land use planning in the region.

  6. Daytime sensible heat flux estimation over heterogeneous surfaces using multitemporal land-surface temperature observations

    Science.gov (United States)

    Castellví, F.; Cammalleri, C.; Ciraolo, G.; Maltese, A.; Rossi, F.

    2016-05-01

    Equations based on surface renewal (SR) analysis to estimate the sensible heat flux (H) require as input the mean ramp amplitude and period observed in the ramp-like pattern of the air temperature measured at high frequency. A SR-based method to estimate sensible heat flux (HSR-LST) requiring only low-frequency measurements of the air temperature, horizontal mean wind speed, and land-surface temperature as input was derived and tested under unstable conditions over a heterogeneous canopy (olive grove). HSR-LST assumes that the mean ramp amplitude can be inferred from the difference between land-surface temperature and mean air temperature through a linear relationship and that the ramp frequency is related to a wind shear scale characteristic of the canopy flow. The land-surface temperature was retrieved by integrating in situ sensing measures of thermal infrared energy emitted by the surface. The performance of HSR-LST was analyzed against flux tower measurements collected at two heights (close to and well above the canopy top). Crucial parameters involved in HSR-LST, which define the above mentioned linear relationship, were explained using the canopy height and the land surface temperature observed at sunrise and sunset. Although the olive grove can behave as either an isothermal or anisothermal surface, HSR-LST performed close to H measured using the eddy covariance and the Bowen ratio energy balance methods. Root mean square differences between HSR-LST and measured H were of about 55 W m-2. Thus, by using multitemporal thermal acquisitions, HSR-LST appears to bypass inconsistency between land surface temperature and the mean aerodynamic temperature. The one-source bulk transfer formulation for estimating H performed reliable after calibration against the eddy covariance method. After calibration, the latter performed similar to the proposed SR-LST method.

  7. New indexing and surface temperature analysis of exoplanets

    CERN Document Server

    Kashyap, J M; Safonova, M

    2016-01-01

    Study of exoplanets is the holy grail of present research in planetary sciences and astrobiology. Analysis of huge planetary data from space missions such as CoRoT and Kepler is directed ultimately at finding a planet similar to Earth\\-the Earth's twin, and answering the question of potential exo-habitability. The Earth Similarity Index (ESI) is a first step in this quest, ranging from 1 (Earth) to 0 (totally dissimilar to Earth). It was defined for the four physical parameters of a planet: radius, density, escape velocity and surface temperature. The ESI is further sub-divided into interior ESI (geometrical mean of radius and density) and surface ESI (geometrical mean of escape velocity and surface temperature). The challenge here is to determine which exoplanet parameter(s) is important in finding this similarity; how exactly the individual parameters entering the interior ESI and surface ESI are contributing to the global ESI. Since the surface temperature entering surface ESI is a non-observable quantity,...

  8. The Impact of Surface Boundary Forcing on Simulation of the 1998 Summer Drought Over the US Midwest Using Factor Separation Technique

    Science.gov (United States)

    Stein, Uri; Fox-Rabinovitz, Michael

    1999-01-01

    The factor separation (FS) technique has been utilized to evaluate quantitatively the impact of surface boundary forcings on simulation of the 1988 summer drought over the Midwestern part of the U.S. The four surface boundary forcings used are: (1)Sea Surface Temperature (SST), (2) soil moisture, (3) snow cover, and (4) sea ice. The Goddard Earth Observing System(GEOS) General Circulation Model (GCM) is used to simulate the 1988 U.S. drought. A series of sixteen simulations are performed with climatological and real 1988 surface boundary conditions. The major single and mutual synergistic factors/impacts are analyzed. The results show that SST and soil moisture are the major single pro-drought factors. The couple synergistic effect of SST and soil moisture is the major anti-drought factor. The triple synergistic impact of SST, soil moisture, and snow cover is the strongest pro-drought impact and is, therefore, the main contributor to the generation of the drought. The impact of the snow cover and sea ice anomalies for June 1988 on the drought is significant only when combined with the SST and soil moisture anomalies.

  9. INVESTIGATION OF SURFACE TEMPERATURE IN HIGH-EFFICIENCY DEEP GRINDING

    Institute of Scientific and Technical Information of China (English)

    Zhao Henghua; Cai Guangqi; Jin Tan

    2005-01-01

    A new thermal model with triangular heat flux distribution is given in high-efficiency deep grinding. The mathematical expressions are driven to calculate the surface temperature. The transient behavior of the maximum temperature on contact area is investigated in different grinding conditions with a J-type thermocouple. The maximum contact temperatures measured in different conditions are found to be between 1 000 ℃ and 1 500 ℃ in burn-out conditions. The experiment results show good agreement with the new thermal model.

  10. Friction velocity u* and roughness length z0 of atmospheric surface boundary layer in sparse-tree land

    Institute of Scientific and Technical Information of China (English)

    Guan Dexin; Zhu Tingyao; Han Shijie

    1999-01-01

    Sparse-tree land is one of the typical lands and can be considered as one typical rough surface in boundary layer meteorology. Many lands can be classified into the kind surface in the view of scale and distribution feature of the roughness elements such as agroforest, scatter planted or growing trees, savanna and so on. The structure of surface boundary layer in sparse-tree land is analyzed and the parameters, friction velocity u* and roughness length z0 are deduced based on energy balance law and other physical hypothesis. The models agree well with data of wind tunnel experiments and field measurements.

  11. Modeling Heat Transfer to Explain Observed Temperature Anomalies in Near-Surface Ice, Greenland Ice Sheet Ablation Area

    Science.gov (United States)

    Hills, B. H.; Harper, J. T.; Meierbachtol, T. W.; Humphrey, N. F.; Johnson, J. V.

    2016-12-01

    Measured ice temperatures in over 30 boreholes at 6 different field sites within the Greenland Ice Sheet ablation area indicate that the near-surface ice temperature warms toward the margin. The rate of warming is significantly greater than the atmospheric lapse rate, meaning that the mean annual ice temperature is far warmer than the mean annual air temperature near the margin. Theoretically, ice within 15 meters of the surface should oscillate seasonally around the mean air temperature. However, observations of mean ice and air temperatures differ by as much as 5 degrees Celsius. Here we numerically model heat transfer in ice to investigate the physical processes that could drive this discrepancy. Modeling results are compared to measured ice temperatures in the first 20 meters of ice below the surface. First, we model pure conduction to analyze the thermal effect of snow accumulation, a fixed melting temperature, ablation at the ice surface, emergent flow of ice, and long-term changes in the mean air temperature. Next, we consider a secondary process beyond pure conduction with the air - a latent heat flux which adds energy by refreezing meltwater below the surface. While our measurement locations have no open crevasses exposed to the surface, borehole field observations reveal that void spaces exist below the ice surface. These subsurface voids could provide a route for water to move to depth where it then refreezes and adds energy to the surrounding ice, thus warming ice above the mean air temperature. Finally, we use the near-surface results as a boundary condition for heat transfer through the full thickness of the ice column. The subsequent model output is compared to borehole temperature measurements at depth to examine the effect of near-surface heat transfer on the rest of the ice column.

  12. Methods for estimating pressure and thermal loads induced by elevon deflections on hypersonic-vehicle surfaces with turbulent boundary layers

    Science.gov (United States)

    Kaufman, L. G., II; Johnson, C. B.

    1981-01-01

    Empirical anaytic methods are presented for calculating thermal and pressure distributions in three-dimensional, shock-wave turbulent-boundary-layer, interaction-flow regions on the surface of controllable hypersonic aircraft and missiles. The methods, based on several experimental investigations, are useful and reliable for estimating both the extent and magnitude of the increased thermal and pressure loads on the vehicle surfaces.

  13. Comparison of surface fluxes and boundary-layer measurements at Arctic terrestrial sites

    Science.gov (United States)

    Grachev, Andrey; Uttal, Taneil; Persson, Ola; Stone, Robert; Crepinsek, Sara; Albee, Robert; Makshtas, Alexander; Kustov, Vasily; Repina, Irina; Artamonov, Arseniy

    2014-05-01

    Observational evidence suggests that atmospheric energy fluxes are a major contributor to the decrease of the Arctic pack ice, seasonal land snow cover and the warming of the surrounding land areas and permafrost layers. To better understand the atmosphere-surface exchange mechanisms, improve models, and to diagnose climate variability in the Arctic, accurate measurements are required of all components of the net surface energy budget and the carbon dioxide cycle over representative areas and over multiple years. This study analyzes and discusses variability of surface fluxes and basic meteorological parameters based on measurements made at several long-term research observatories near the coast of the Arctic Ocean located in USA (Barrow), Canada (Eureka), and Russia (Tiksi). Tower-based eddy covariance and solar radiation measurements provide a long-term near continuous temporal record of hourly average mass and energy fluxes respectively. The turbulent fluxes of the momentum, sensible heat, water vapor, and carbon dioxide are supported by additional atmospheric and surface/snow/permafrost measurements (mean wind speed, air temperature and humidity, upwelling and downwelling short-wave and long-wave atmospheric and surface radiation, snow depth, surface albedo, soil heat flux, active layer temperature profiles etc.) In this study we compare annual cycles of surface fluxes including solar radiation and other ancillary data to describe four seasons in the Arctic including spring onset of melt and fall onset of snow accumulation. Particular interest is a transition through freezing point, i.e. during transition from winter to spring and from summer to fall, when the carbon dioxide and/or water vapor turbulent fluxes change their direction. According to our data, in a summer period observed temporal variability of the carbon dioxide flux was generally in anti-phase with water vapor flux (downward CO2 flux and upward H2O flux). On average the turbulent flux of carbon

  14. The Remote Sensing of Surface Radiative Temperature over Barbados.

    Science.gov (United States)

    remote sensing of surface radiative temperature over Barbados was undertaken using a PRT-5 attached to a light aircraft. Traverses across the centre of the island, over the rugged east coast area, and the urban area of Bridgetown were undertaken at different times of day and night in the last week of June and the first week of December, 1969. These traverses show that surface variations in long-wave radiation emission lie within plus or minus 5% of the observations over grass at a representative site. The quick response of the surface to sunset and sunrise was

  15. A comparison of all-weather land surface temperature products

    Science.gov (United States)

    Martins, Joao; Trigo, Isabel F.; Ghilain, Nicolas; Goettche, Frank-M.; Ermida, Sofia; Olesen, Folke-S.; Gellens-Meulenberghs, Françoise; Arboleda, Alirio

    2017-04-01

    The Satellite Application Facility on Land Surface Analysis (LSA-SAF, http://landsaf.ipma.pt) has been providing land surface temperature (LST) estimates using SEVIRI/MSG on an operational basis since 2006. The LSA-SAF service has since been extended to provide a wide range of satellite-based quantities over land surfaces, such as emissivity, albedo, radiative fluxes, vegetation state, evapotranspiration, and fire-related variables. Being based on infra-red measurements, the SEVIRI/MSG LST product is limited to clear-sky pixels only. Several all-weather LST products have been proposed by the scientific community either based on microwave observations or using Soil-Vegetation-Atmosphere Transfer models to fill the gaps caused by clouds. The goal of this work is to provide a nearly gap-free operational all-weather LST product and compare these approaches. In order to estimate evapotranspiration and turbulent energy fluxes, the LSA-SAF solves the surface energy budget for each SEVIRI pixel, taking into account the physical and physiological processes occurring in vegetation canopies. This task is accomplished with an adapted SVAT model, which adopts some formulations and parameters of the Tiled ECMWF Scheme for Surface Exchanges over Land (TESSEL) model operated at the European Center for Medium-range Weather Forecasts (ECMWF), and using: 1) radiative inputs also derived by LSA-SAF, which includes surface albedo, down-welling fluxes and fire radiative power; 2) a land-surface characterization obtained by combining the ECOCLIMAP database with both LSA-SAF vegetation products and the H(ydrology)-SAF snow mask; 3) meteorological fields from ECMWF forecasts interpolated to SEVIRI pixels, and 4) soil moisture derived by the H-SAF and LST from LSA-SAF. A byproduct of the SVAT model is surface skin temperature, which is needed to close the surface energy balance. The model skin temperature corresponds to the radiative temperature of the interface between soil and atmosphere

  16. Enzyme surface rigidity tunes the temperature dependence of catalytic rates.

    Science.gov (United States)

    Isaksen, Geir Villy; Åqvist, Johan; Brandsdal, Bjørn Olav

    2016-07-12

    The structural origin of enzyme adaptation to low temperature, allowing efficient catalysis of chemical reactions even near the freezing point of water, remains a fundamental puzzle in biocatalysis. A remarkable universal fingerprint shared by all cold-active enzymes is a reduction of the activation enthalpy accompanied by a more negative entropy, which alleviates the exponential decrease in chemical reaction rates caused by lowering of the temperature. Herein, we explore the role of protein surface mobility in determining this enthalpy-entropy balance. The effects of modifying surface rigidity in cold- and warm-active trypsins are demonstrated here by calculation of high-precision Arrhenius plots and thermodynamic activation parameters for the peptide hydrolysis reaction, using extensive computer simulations. The protein surface flexibility is systematically varied by applying positional restraints, causing the remarkable effect of turning the cold-active trypsin into a variant with mesophilic characteristics without changing the amino acid sequence. Furthermore, we show that just restraining a key surface loop causes the same effect as a point mutation in that loop between the cold- and warm-active trypsin. Importantly, changes in the activation enthalpy-entropy balance of up to 10 kcal/mol are almost perfectly balanced at room temperature, whereas they yield significantly higher rates at low temperatures for the cold-adapted enzyme.

  17. Temperature limit values for touching cold surfaces with the fingertip

    NARCIS (Netherlands)

    Geng, Q.; Holme, I.; Hartog, E.A. den; Havenith, G.; Jay, O.; Malchaires, J.; Piette, A.; Rintama, H.; Rissanen, S.

    2006-01-01

    Objectives: At the request of the European Commission and in the framework of the European Machinery Directive, research was performed in five different laboratories to develop specifications for surface temperature limit values for the short-term accidental touching of the fingertip with cold

  18. Temperature limit values for touching cold surfaces with the fingertip

    NARCIS (Netherlands)

    Geng, Q.; Holme, I.; Hartog, E.A. den; Havenith, G.; Jay, O.; Malchaires, J.; Piette, A.; Rintama, H.; Rissanen, S.

    2006-01-01

    Objectives: At the request of the European Commission and in the framework of the European Machinery Directive, research was performed in five different laboratories to develop specifications for surface temperature limit values for the short-term accidental touching of the fingertip with cold surfa

  19. Climate Prediction Center (CPC) Global Land Surface Air Temperature Analysis

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A station observation-based global land monthly mean surface air temperature dataset at 0.5 x 0.5 latitude-longitude resolution for the period from 1948 to the...

  20. Quantifying and specifying the solar influence on terrestrial surface temperature

    NARCIS (Netherlands)

    de Jager, C.; Duhau, S.; van Geel, B.

    2010-01-01

    This investigation is a follow-up of a paper in which we showed that both major magnetic components of the solar dynamo, viz. the toroidal and the poloidal ones, are correlated with average terrestrial surface temperatures. Here, we quantify, improve and specify that result and search for their caus

  1. A physically based model of global freshwater surface temperature

    NARCIS (Netherlands)

    Beek, van L.P.H.; Eikelboom, T.; Vliet, van M.T.H.; Bierkens, M.F.P.

    2012-01-01

    Temperature determines a range of physical properties of water and exerts a strong control on surface water biogeochemistry. Thus, in freshwater ecosystems the thermal regime directly affects the geographical distribution of aquatic species through their growth and metabolism and indirectly through

  2. Climate Prediction Center (CPC) Global Land Surface Air Temperature Analysis

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A station observation-based global land monthly mean surface air temperature dataset at 0.5 0.5 latitude-longitude resolution for the period from 1948 to the present...

  3. Processes of India's offshore summer intraseasonal sea surface temperature variability

    Digital Repository Service at National Institute of Oceanography (India)

    Kurian, N.; Lengaigne, M.; Gopalakrishna, V.V.; Vialard, J.; Pous, S.; Peter, A-C.; Durand; Naik, Shweta

    ., vol.63; 2013; 329-346 Processes of India’s offshore summer intraseasonal sea surface temperature variability K. Nisha1, M. Lengaigne1,2, V.V. Gopalakrishna,1 J. Vialard2, S. Pous2, A.-C. Peter2, F. Durand3, S.Naik1 1. NIO, CSIR, Goa, India 2...

  4. A physically based model of global freshwater surface temperature

    NARCIS (Netherlands)

    Beek, van L.P.H.; Eikelboom, T.; Vliet, van M.T.H.; Bierkens, M.F.P.

    2012-01-01

    Temperature determines a range of physical properties of water and exerts a strong control on surface water biogeochemistry. Thus, in freshwater ecosystems the thermal regime directly affects the geographical distribution of aquatic species through their growth and metabolism and indirectly through

  5. Surface temperature maps for II Peg during 1999-2002

    CERN Document Server

    Lindborg, M; Tuominen, I; Hackman, T; Ilyin, I; Piskunov, N

    2009-01-01

    The active RS CVn star II Peg has been spectroscopically monitored for almost 18 years with the SOFIN spectrograph at NOT, La Palma, Spain. In this paper we present five new surface temperature maps of the object for the years 1999 (two maps), 2001 (one map) and 2002 (two maps).

  6. On the effectiveness of surface assimilation in probabilistic nowcasts of planetary boundary layer profiles

    Science.gov (United States)

    Rostkier-Edelstein, Dorita; Hacker, Joshua

    2013-04-01

    Surface observations comprise a wide, non-expensive and reliable source of information about the state of the near-surface planetary boundary layer (PBL). Operational data assimilation systems have encountered several difficulties in effectively assimilating them, among others due to their local-scale representativeness, the transient coupling between the surface and the atmosphere aloft and the balance constraints usually used. A long-term goal of this work is to find an efficient system for probabilistic PBL nowcasting that can be employed wherever surface observations are present. Earlier work showed that surface observations can be an important source of information with a single column model (SCM) and an ensemble filter (EF). Here we extend that work to quantify the probabilistic skill of ensemble SCM predictions with a model including added complexity. We adopt a factor separation analysis to quantify the contribution of surface assimilation relative to that of selected model components (parameterized radiation and externally imposed horizontal advection) to the probabilistic skill of the system, and of any beneficial or detrimental interactions between them. To assess the real utility of the flow-dependent covariances estimated with the EF and of the SCM of the PBL we compare the skill of the SCM/EF system to that of a reference one based on climatological covariances and a 30-min persistence model. It consists of a dressing technique, whereby a deterministic 3D mesoscale forecast (e.g. from WRF model) is adjusted and dressed with uncertainty using a seasonal sample of mesoscale forecasts and surface forecast errors. Results show that assimilation of surface observations can improve deterministic and probabilistic profile predictions more significantly than major model improvements. Flow-dependent covariances estimated with the SCM/EF show clear advantage over the use of climatological covariances when the flow is characterized by wide variability, when

  7. On the Boundary Condition for Water at a Hydrophobic, Dense Surface

    Science.gov (United States)

    Walther, J. H.; Jaffe, R. L.; Werder, T.; Halicioglu, T.; Koumoutsakos, P.

    2002-01-01

    We study the no-slip boundary conditions for water at a hydrophobic (graphite) surface using non-equilibrium molecular-dynamics simulations. For the planar Couette flow, we find a slip length of 64 nm at 1 bar and 300 K, decreasing with increasing system pressure to a value of 31 nm at 1000 bar. Changing the properties of the interface to from hydrophobic to strongly hydrophilic reduces the slip to 14 nm. Finally, we study the flow of water past an array of carbon nanotubes mounted in an inline configuration with a spacing of 16.4 x 16.4 nm. For tube diameters of 1.25 and 2.50 nm we find drag coefficients in good agreement with the macroscopic, Navier-Stokes values. For carbon nanotubes, the no-slip condition is valid to within the definition of the position of the interface.

  8. Accurate computation of Galerkin double surface integrals in the 3-D boundary element method

    CERN Document Server

    Adelman, Ross; Duraiswami, Ramani

    2015-01-01

    Many boundary element integral equation kernels are based on the Green's functions of the Laplace and Helmholtz equations in three dimensions. These include, for example, the Laplace, Helmholtz, elasticity, Stokes, and Maxwell's equations. Integral equation formulations lead to more compact, but dense linear systems. These dense systems are often solved iteratively via Krylov subspace methods, which may be accelerated via the fast multipole method. There are advantages to Galerkin formulations for such integral equations, as they treat problems associated with kernel singularity, and lead to symmetric and better conditioned matrices. However, the Galerkin method requires each entry in the system matrix to be created via the computation of a double surface integral over one or more pairs of triangles. There are a number of semi-analytical methods to treat these integrals, which all have some issues, and are discussed in this paper. We present novel methods to compute all the integrals that arise in Galerkin fo...

  9. Colloidal Surfaces with Boundaries, Apex Boojums, and Nested Elastic Self-Assembly of Nematic Colloids

    Science.gov (United States)

    Park, Sungoh; Liu, Qingkun; Smalyukh, Ivan I.

    2016-12-01

    Self-assembly of colloidal particles is poised to become a powerful composite material fabrication technique, but remains challenged by a limited control over the ensuing structures. We develop a new breed of nematic colloids that are physical analogs of a mathematical surface with boundary, interacting with the molecular alignment field without inducing defects when flat. However, made from a thin nanofoil, they can be shaped to prompt formation of self-compensating defects that drive preprogramed elastic interactions mediated by the nematic host. To show this, we wrap the nanofoil on all triangular side faces of a pyramid, except its square base. The ensuing pyramidal cones induce point defects with fractional hedgehog charges of opposite signs, spontaneously align with respect to the far-field director to form elastic dipoles and nested assemblies with tunable spacing. Nanofoils shaped into octahedrons interact as elastic quadrupoles. Our findings may drive realization of low-symmetry colloidal phases.

  10. A Physically Constrained Calibration Database for Land Surface Temperature Using Infrared Retrieval Algorithms

    Directory of Open Access Journals (Sweden)

    João P. A. Martins

    2016-09-01

    Full Text Available Land surface temperature (LST is routinely retrieved from remote sensing instruments using semi-empirical relationships between top of atmosphere (TOA radiances and LST, using ancillary data such as total column water vapor or emissivity. These algorithms are calibrated using a set of forward radiative transfer simulations that return the TOA radiances given the LST and the thermodynamic profiles. The simulations are done in order to cover a wide range of surface and atmospheric conditions and viewing geometries. This study analyzes calibration strategies while considering some of the most critical factors that need to be taken into account when building a calibration dataset, covering the full dynamic range of relevant variables. A sensitivity analysis of split-windows and single channel algorithms revealed that selecting a set of atmospheric profiles that spans the full range of surface temperatures and total column water vapor combinations that are physically possible seems beneficial for the quality of the regression model. However, the calibration is extremely sensitive to the low-level structure of the atmosphere, indicating that the presence of atmospheric boundary layer features such as temperature inversions or strong vertical gradients of thermodynamic properties may affect LST retrievals in a non-trivial way. This article describes the criteria established in the EUMETSAT Land Surface Analysis—Satellite Application Facility to calibrate its LST algorithms, applied both for current and forthcoming sensors.

  11. A Microring Temperature Sensor Based on the Surface Plasmon Wave

    Directory of Open Access Journals (Sweden)

    Wenchao Li

    2015-01-01

    Full Text Available A structure of microring sensor suitable for temperature measurement based on the surface plasmon wave is put forward in this paper. The sensor uses surface plasmon multilayer waveguiding structure in the vertical direction and U-shaped microring structure in the horizontal direction and utilizes SOI as the thermal material. The transfer function derivation of the structure of surface plasmon microring sensor is according to the transfer matrix method. While the change of refractive index of Si is caused by the change of ambient temperature, the effective refractive index of the multilayer waveguiding structure is changed, resulting in the drifting of the sensor output spectrum. This paper focuses on the transmission characteristics of multilayer waveguide structure and the impact on the output spectrum caused by refractive index changes in temperature parts. According to the calculation and simulation, the transmission performance of the structure is stable and the sensitivity is good. The resonance wavelength shift can reach 0.007 μm when the temperature is increased by 100 k and FSR can reach about 60 nm. This structure achieves a high sensitivity in the temperature sense taking into account a wide range of filter frequency selections, providing a theoretical basis for the preparation of microoptics.

  12. The response of the Ocean Surface Boundary Layer and Langmuir turbulence to tropical cyclones

    Science.gov (United States)

    Wang, Dong; Kukulka, Tobias; Reichl, Brandon; Hara, Tetsu; Ginis, Isaac

    2016-11-01

    The interaction of turbulent ocean surface boundary layer (OSBL) currents and the surface waves' Stokes drift generates Langmuir turbulence (LT), which enhances OSBL mixing. This study investigates the response of LT to extreme wind and complex wave forcing under tropical cyclones (TCs), using a large eddy simulation (LES) approach based on the wave-averaged Navier-Stokes equations. We simulate the OSBL response to TC systems by imposing the wind forcing of an idealized TC storm model, covering the entire horizontal extent of the storm systems. The Stokes drift vector that drives the wave forcing in the LES is determined from realistic spectral wave simulations forced by the same wind fields. We find that the orientations of Langmuir cells are vertically uniform and aligned with the wind in most regions despite substantial wind-wave misalignment in TC conditions. LT's penetration depth is related to Stokes drift depth and limited by OSBL depth. A wind-projected surface layer Langmuir number is proposed and successfully applied to scale turbulent vertical velocity variance in extreme TC conditions. Current affiliation: Princeton University/NOAA GFDL.

  13. Visualization of pre-set vortices in boundary layer flow over wavy surface in rectangular channel

    KAUST Repository

    Budiman, Alexander Christantho

    2014-12-04

    Abstract: Smoke-wire flow visualization is used to study the development of pre-set counter-rotating streamwise vortices in boundary layer flow over a wavy surface in a rectangular channel. The formation of the vortices is indicated by the vortical structures on the cross-sectional plane normal to the wavy surface. To obtain uniform spanwise vortex wavelength which will result in uniform vortex size, two types of spanwise disturbances were used: a series of perturbation wires placed prior and normal to the leading edge of the wavy surface, and a jagged pattern in the form of uniform triangles cut at the leading edge. These perturbation wires and jagged pattern induce low-velocity streaks that result in the formation of counter-rotating streamwise vortices that evolve downstream to form the mushroom-like structures on the cross-sectional plane of the flow. The evolution of the most amplified disturbances can be attributed to the formation of these mushroom-like structures. It is also shown that the size of the mushroom-like structures depends on the channel entrance geometry, Reynolds number, and the channel gap.Graphical Abstract: [Figure not available: see fulltext.

  14. A numerical study of turbulent boundary layer flow over a dimpled surface

    Energy Technology Data Exchange (ETDEWEB)

    Kithcart, M.E. [North Carolina A and T State Univ., CAR, Greensboro, North Carolina (United States)]. E-mail: kithcart@ncat.edu; Klett, D.E. [North Carolina A and T State Univ., Mechanical Engineering, Greensboro, North Carolina (United States)]. E-mail: klett@ncat.edu

    2002-07-01

    Turbulent boundary layer flow over a flat surface with a single dimple, and a surface with two dimples in tandem has been investigated numerically using the FLUENT CFD software package, and compared to an experiment, which studied the same configuration. The impetus for this work came as a result of previous studies, which indicate that dimple surfaces enhance heat transfer comparably to protrusion roughness elements, but the heat transfer augmentation does come with the penalty of increased drag. However, the exact physical mechanisms involved in the effects associated with dimples were not well known prior this study. Results for the single dimple configuration are in good agreement with an experiment, which studied the same configuration, particularly the confirmation of the existence of a region of enhanced heat transfer created by the dimple. In addition, it can be determined from the numerical study that the heat transfer enhancement is a consequence of the development of a stagnation flow region within the dimple geometry. In the two-dimple roughness simulation, the elements were spaced one half diameter apart, in order to observe any possible interaction. The results of the simulation indicate that the local flow-field in the vicinity of a dimple is unaffected by the presence of a neighboring element. (author)

  15. Ground Boundary Conditions for Thermal Convection Over Horizontal Surfaces at High Rayleigh Numbers

    Science.gov (United States)

    Hanjalić, K.; Hrebtov, M.

    2016-07-01

    We present "wall functions" for treating the ground boundary conditions in the computation of thermal convection over horizontal surfaces at high Rayleigh numbers using coarse numerical grids. The functions are formulated for an algebraic-flux model closed by transport equations for the turbulence kinetic energy, its dissipation rate and scalar variance, but could also be applied to other turbulence models. The three-equation algebraic-flux model, solved in a T-RANS mode ("Transient" Reynolds-averaged Navier-Stokes, based on triple decomposition), was shown earlier to reproduce well a number of generic buoyancy-driven flows over heated surfaces, albeit by integrating equations up to the wall. Here we show that by using a set of wall functions satisfactory results are found for the ensemble-averaged properties even on a very coarse computational grid. This is illustrated by the computations of the time evolution of a penetrative mixed layer and Rayleigh-Bénard (open-ended, 4:4:1 domain) convection, using 10 × 10 × 100 and 10 × 10 × 20 grids, compared also with finer grids (e.g. 60 × 60 × 100), as well as with one-dimensional treatment using 1 × 1 × 100 and 1 × 1 × 20 nodes. The approach is deemed functional for simulations of a convective boundary layer and mesoscale atmospheric flows, and pollutant transport over realistic complex hilly terrain with heat islands, urban and natural canopies, for diurnal cycles, or subjected to other time and space variations in ground conditions and stratification.

  16. Modeling the surface temperature of Earth-like planets

    CERN Document Server

    Vladilo, G; Murante, G; Filippi, L; Provenzale, A

    2015-01-01

    We introduce a novel Earth-like planet surface temperature model (ESTM) for habitability studies based on the spatial-temporal distribution of planetary surface temperatures. The ESTM adopts a surface Energy Balance Model complemented by: radiative-convective atmospheric column calculations, a set of physically-based parameterizations of meridional transport, and descriptions of surface and cloud properties more refined than in standard EBMs. The parameterization is valid for rotating terrestrial planets with shallow atmospheres and moderate values of axis obliquity (epsilon >= 45^o). Comparison with a 3D model of atmospheric dynamics from the literature shows that the equator-to-pole temperature differences predicted by the two models agree within ~5K when the rotation rate, insolation, surface pressure and planet radius are varied in the intervals 0.5 <= Omega/Omega_o <= 2, 0.75 <= S/S_o <= 1.25, 0.3 <= p/(1 bar) <= 10, and 0.5 <= R/R_o <= 2, respectively. The ESTM has an extremely l...

  17. Modeling Apple Surface Temperature Dynamics Based on Weather Data

    Directory of Open Access Journals (Sweden)

    Lei Li

    2014-10-01

    Full Text Available The exposure of fruit surfaces to direct sunlight during the summer months can result in sunburn damage. Losses due to sunburn damage are a major economic problem when marketing fresh apples. The objective of this study was to develop and validate a model for simulating fruit surface temperature (FST dynamics based on energy balance and measured weather data. A series of weather data (air temperature, humidity, solar radiation, and wind speed was recorded for seven hours between 11:00–18:00 for two months at fifteen minute intervals. To validate the model, the FSTs of “Fuji” apples were monitored using an infrared camera in a natural orchard environment. The FST dynamics were measured using a series of thermal images. For the apples that were completely exposed to the sun, the RMSE of the model for estimating FST was less than 2.0 °C. A sensitivity analysis of the emissivity of the apple surface and the conductance of the fruit surface to water vapour showed that accurate estimations of the apple surface emissivity were important for the model. The validation results showed that the model was capable of accurately describing the thermal performances of apples under different solar radiation intensities. Thus, this model could be used to more accurately estimate the FST relative to estimates that only consider the air temperature. In addition, this model provides useful information for sunburn protection management.

  18. A model of the tropical Pacific sea surface temperature climatology

    Science.gov (United States)

    Seager, Richard; Zebiak, Stephen E.; Cane, Mark A.

    1988-01-01

    A model for the climatological mean sea surface temperature (SST) of the tropical Pacific Ocean is developed. The upper ocean response is computed using a time dependent, linear, reduced gravity model, with the addition of a constant depth frictional surface layer. The full three-dimensional temperature equation and a surface heat flux parameterization that requires specification of only wind speed and total cloud cover are used to evaluate the SST. Specification of atmospheric parameters, such as air temperature and humidity, over which the ocean has direct influence, is avoided. The model simulates the major features of the observed tropical Pacific SST. The seasonal evolution of these features is generally captured by the model. Analysis of the results demonstrates the control the ocean has over the surface heat flux from ocean to atmosphere and the crucial role that dynamics play in determining the mean SST in the equatorial Pacific. The sensitivity of the model to perturbations in the surface heat flux, cloud cover specification, diffusivity, and mixed layer depth is discussed.

  19. Temperature maps measurements on 3D surfaces with infrared thermography

    Energy Technology Data Exchange (ETDEWEB)

    Cardone, Gennaro; Ianiro, Andrea [University of Naples Federico II, Department of Aerospace Engineering (DIAS), Naples (Italy); Ioio, Gennaro dello [University of Cambridge, BP Institute for Multiphase Flow, Cambridge, England (United Kingdom); Passaro, Andrea [Alta SpA, Ospedaletto, PI (Italy)

    2012-02-15

    The use of the infrared camera as a temperature transducer in wind tunnel applications is convenient and widespread. Nevertheless, the infrared data are available in the form of 2D images while the observed surfaces are often not planar and the reconstruction of temperature maps over them is a critical task. In this work, after recalling the principles of IR thermography, a methodology to rebuild temperature maps on the surfaces of 3D object is proposed. In particular, an optical calibration is applied to the IR camera by means of a novel target plate with control points. The proposed procedure takes also into account the directional emissivity by estimating the viewing angle. All the needed steps are described and analyzed. The advantages given by the proposed method are shown with an experiment in a hypersonic wind tunnel. (orig.)

  20. Dynamics of ordering in highly degenerate models with anisotropic grain-boundary potential: Effects of temperature and vortex formation

    DEFF Research Database (Denmark)

    Jeppesen, Claus; Flyvbjerg, Henrik; Mouritsen, Ole G.

    1989-01-01

    Monte Carlo computer-simulation techniques are used to elucidate the equilibrium phase behavior as well as the late-stage ordering dynamics of some two-dimensional models with ground-state ordering of a high degeneracy, Q. The models are Q-state Potts models with anisotropic grain......, like the standard Potts models do, nor a wetting of the boundaries, as the standard clock models do. Thermal fluctuations nevertheless cause wetting to occur for not too small temperatures. Specifically, we have studied models with Q=12 and 48. The models are quenched from infinite to zero as well......, for quenches to finite temperatures in the Potts-ordered phase there is a distinct crossover to the classical Lifshitz-Allen-Cahn exponent value, n=1 / 2, for both values of Q. This supports the conjecture that the zero-temperature dynamics for models with soft domain boundaries belong to a special...

  1. A Surface Temperature Initiated Closure (STIC) for surface energy balance fluxes

    DEFF Research Database (Denmark)

    Mallick, Kaniska; Jarvis, Andrew J.; Boegh, Eva;

    2014-01-01

    of four state equations. Taking advantage of the psychrometric relationship between temperature and vapor pressure, the present method also estimates the near surface moisture availability (M) from TS, air temperature (TA) and relative humidity (RH), thereby being capable of decomposing λ...

  2. Prediction of acoustic radiation from axisymmetric surfaces with arbitrary boundary conditions using the boundary element method on a distributed computing system.

    Science.gov (United States)

    Wright, Louise; Robinson, Stephen P; Humphrey, Victor F

    2009-03-01

    This paper presents a computational technique using the boundary element method for prediction of radiated acoustic waves from axisymmetric surfaces with nonaxisymmetric boundary conditions. The aim is to predict the far-field behavior of underwater acoustic transducers based on their measured behavior in the near-field. The technique is valid for all wavenumbers and uses a volume integral method to calculate the singular integrals required by the boundary element formulation. The technique has been implemented on a distributed computing system to take advantage of its parallel nature, which has led to significant reductions in the time required to generate results. Measurement data generated by a pair of free-flooding underwater acoustic transducers encapsulated in a polyurethane polymer have been used to validate the technique against experiment. The dimensions of the outer surface of the transducers (including the polymer coating) were an outer diameter of 98 mm with an 18 mm wall thickness and a length of 92 mm. The transducers were mounted coaxially, giving an overall length of 185 mm. The cylinders had resonance frequencies at 13.9 and 27.5 kHz, and the data were gathered at these frequencies.

  3. Assessment Of Surface-Catalyzed Reaction Products From High Temperature Materials In Plasmas

    Science.gov (United States)

    Allen, Luke Daniel

    Current simulations of atmospheric entry into both Mars and Earth atmospheres for the design of thermal protections systems (TPS) typically invoke conservative assumptions regarding surface-catalyzed recombination and the amount of energy deposited on the surface. The need to invoke such assumptions derives in part from lack of adequate experimental data on gas-surface interactions at trajectory relevant conditions. Addressing this issue, the University of Vermont's Plasma Test and Diagnostics Laboratory has done extensive work to measure atomic specie consumption by measuring the concentration gradient over various material surfaces. This thesis extends this work by attempting to directly diagnose molecular species production in air plasmas. A series of spectral models for the A-X and B-X systems of nitric oxide (NO), and the B-X system of boron monoxide (BO) have been developed. These models aim to predict line positions and strengths for the respective molecules in a way that is best suited for the diagnostic needs of the UVM facility. From the NO models, laser induced fluorescence strategies have been adapted with the intent of characterizing the relative quantity and thermodynamic state of NO produced bysurface-catalyzed recombination, while the BO model adds a diagnostic tool for the testing of diboride-based TPS materials. Boundary layer surveys of atomic nitrogen and NO have been carried out over water-cooled copper and nickel surfaces in air/argon plasmas. Translation temperatures and relative number densities throughout the boundary layer are reported. Additional tests were also conducted over a water-cooled copper surface to detect evidence of highly non-equilibrium effects in the form of excess population in elevated vibrational levels of the A-X system of NO. The tests showed that near the sample surface there is a much greater population in the upsilon'' = 1ground state than is predicted by a Boltzmann distribution.

  4. Designing high-temperature steels via surface science and thermodynamics

    Science.gov (United States)

    Gross, Cameron T.; Jiang, Zilin; Mathai, Allan; Chung, Yip-Wah

    2016-06-01

    Electricity in many countries such as the US and China is produced by burning fossil fuels in steam-turbine-driven power plants. The efficiency of these power plants can be improved by increasing the operating temperature of the steam generator. In this work, we adopted a combined surface science and computational thermodynamics approach to the design of high-temperature, corrosion-resistant steels for this application. The result is a low-carbon ferritic steel with nanosized transition metal monocarbide precipitates that are thermally stable, as verified by atom probe tomography. High-temperature Vickers hardness measurements demonstrated that these steels maintain their strength for extended periods at 700 °C. We hypothesize that the improved strength of these steels is derived from the semi-coherent interfaces of these thermally stable, nanosized precipitates exerting drag forces on impinging dislocations, thus maintaining strength at elevated temperatures.

  5. Surface layer temperature inversion in the Bay of Bengal

    Science.gov (United States)

    Thadathil, Pankajakshan; Gopalakrishna, V. V.; Muraleedharan, P. M.; Reddy, G. V.; Araligidad, Nilesh; Shenoy, Shrikant

    2002-10-01

    Surface layer temperature inversion occurring in the Bay of Bengal has been addressed. Hydrographic data archived in the Indian Oceanographic Data Center are used to understand various aspects of the temperature inversion of surface layer in the Bay of Bengal, such as occurrence time, characteristics, stability, inter-annual variability and generating mechanisms. Spatially organized temperature inversion occurs in the coastal waters of the western and northeastern Bay during winter (November-February). Although the inversion in the northeastern Bay is sustained until February (with remnants seen even in March), in the western Bay it becomes less organized in January and almost disappears by February. Inversion is confined to the fresh water induced seasonal halocline of the surface layer. Inversions of large temperature difference (of the order of 1.6-2.4°C) and thin layer thickness (10-20 m) are located adjacent to major fresh water inputs from the Ganges, Brahmaputra, Irrawaddy, Krishna and Godavari rivers. The inversion is stable with a mean stability of 3600×10 -8 m -1. Inter-annual variability of the inversion is significantly high and it is caused by the inter-annual variability of fresh water flux and surface cooling in the northern Bay. Fresh water flux leads the occurrence process in association with surface heat flux and advection. The leading role of fresh water flux is understood from the observation that the two occurrence regions of inversion (the western and northeastern Bay) have proximity to the two low salinity (with values about 28-29‰) zones. In the western Bay, the East India Coastal Current brings less saline and cold water from the head of the Bay to the south-west Bay, where it advects over warm, saline water, promoting temperature inversion in this region in association with the surface heat loss. For inversion occurring in the northeastern Bay (where the surface water gains heat from atmosphere), surface advection of the less saline

  6. New Measurements from Old Boreholes: A Look at Interaction Between Surface Air Temperature and Ground Surface Temperature

    Science.gov (United States)

    Heinle, S. M.; Gosnold, W. D.

    2007-12-01

    We recently logged new field measurements of several boreholes throughout the Midwest, including North Dakota, South Dakota, and Nebraska. We then compared these new measurements against measurements previously obtained. Our comparisons included inverse modeling of past and recent measurements as well as climate modeling based on past surface air temperatures obtained from the weather stations. The data show a good correlation between climate warming in the last century and ground surface warming. Of particular importance is that cooling of air temperatures beginning in the mid 1990s reflects in the ground surface temperatures. The boreholes included in the study consist of three boreholes located in north central North Dakota, including two deeper than 200 meters. Two boreholes in the southwestern part of South Dakota, and two from southeastern South Dakota, all approximately 180 meters deep. Also included, were two boreholes (135 meters and over 200 meters deep) located in southwestern Nebraska, and two boreholes in the panhandle of Nebraska, each over 100 meters deep. We obtained historical surface air temperature from climate stations located near the boreholes, both from the United States Historical Climatology Network and from the Western Regional Climate Center.

  7. Surface emissivity and temperature retrieval for a hyperspectral sensor

    Energy Technology Data Exchange (ETDEWEB)

    Borel, C.C.

    1998-12-01

    With the growing use of hyper-spectral imagers, e.g., AVIRIS in the visible and short-wave infrared there is hope of using such instruments in the mid-wave and thermal IR (TIR) some day. The author believes that this will enable him to get around using the present temperature-emissivity separation algorithms using methods which take advantage of the many channels available in hyper-spectral imagers. A simple fact used in coming up with a novel algorithm is that a typical surface emissivity spectrum are rather smooth compared to spectral features introduced by the atmosphere. Thus, a iterative solution technique can be devised which retrieves emissivity spectra based on spectral smoothness. To make the emissivities realistic, atmospheric parameters are varied using approximations, look-up tables derived from a radiative transfer code and spectral libraries. One such iterative algorithm solves the radiative transfer equation for the radiance at the sensor for the unknown emissivity and uses the blackbody temperature computed in an atmospheric window to get a guess for the unknown surface temperature. By varying the surface temperature over a small range a series of emissivity spectra are calculated. The one with the smoothest characteristic is chosen. The algorithm was tested on synthetic data using MODTRAN and the Salisbury emissivity database.

  8. Sea-surface temperature and salinity mapping from remote microwave radiometric measurements of brightness temperature

    Science.gov (United States)

    Hans-Juergen, C. B.; Kendall, B. M.; Fedors, J. C.

    1977-01-01

    A technique to measure remotely sea surface temperature and salinity was demonstrated with a dual frequency microwave radiometer system. Accuracies in temperature of 1 C and in salinity of part thousand for salinity greater than 5 parts per thousand were attained after correcting for the influence of extraterrestrial background radiation, atmospheric radiation and attenuation, sea-surface roughness, and antenna beamwidth. The radiometers, operating at 1.43 and 2.65 GHz, comprise a third-generation system using null balancing and feedback noise injection. Flight measurements from an aircraft at an altitude of 1.4 km over the lower Chesapeake Bay and coastal areas of the Atlantic Ocean resulted in contour maps of sea-surface temperature and salinity with a spatial resolution of 0.5 km.

  9. Ultraviolet surface plasmon-mediated low temperature hydrazine decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Siying; Sheldon, Matthew T.; Atwater, Harry A. [Thomas J. Watson Laboratories of Applied Physics, California Institute of Technology, Pasadena, California 91125 (United States); Liu, Wei-Guang; Jaramillo-Botero, Andres; Goddard, William Andrew [Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125 (United States)

    2015-01-12

    Conventional methods require elevated temperatures in order to dissociate high-energy nitrogen bonds in precursor molecules such as ammonia or hydrazine used for nitride film growth. We report enhanced photodissociation of surface-absorbed hydrazine (N{sub 2}H{sub 4}) molecules at low temperature by using ultraviolet surface plasmons to concentrate the exciting radiation. Plasmonic nanostructured aluminum substrates were designed to provide resonant near field concentration at λ = 248 nm (5 eV), corresponding to the maximum optical cross section for hydrogen abstraction from N{sub 2}H{sub 4}. We employed nanoimprint lithography to fabricate 1 mm × 1 mm arrays of the resonant plasmonic structures, and ultraviolet reflectance spectroscopy confirmed resonant extinction at 248 nm. Hydrazine was cryogenically adsorbed to the plasmonic substrate in a low-pressure ambient, and 5 eV surface plasmons were resonantly excited using a pulsed KrF laser. Mass spectrometry was used to characterize the photodissociation products and indicated a 6.2× overall enhancement in photodissociation yield for hydrazine adsorbed on plasmonic substrates compared with control substrates. The ultraviolet surface plasmon enhanced photodissociation demonstrated here may provide a valuable method to generate reactive precursors for deposition of nitride thin film materials at low temperatures.

  10. The dependence of surface temperature on IGBTs load and ambient temperature

    Science.gov (United States)

    Alexander, Čaja; Marek, Patsch

    2015-05-01

    Currently, older power electronics and electrotechnics are improvement and at the same time developing new and more efficient devices. These devices produce in their activities a significant part of the heat which, if not effectively drained, causing damage to these elements. In this case, it is important to develop new and more efficient cooling system. The most widespread of modern methods of cooling is the cooling by heat pipe. This contribution is aimed at cooling the insulated-gate bipolar transistor (IGBT) elements by loop heat pipe (LHP). IGBTs are very prone to damage due to high temperatures, and therefore is the important that the surface temperature was below 100°C. It was therefore created a model that examined what impact of surface temperature on the IGBT element and heat removal at different load and constant ambient temperature.

  11. The dependence of surface temperature on IGBTs load and ambient temperature

    Directory of Open Access Journals (Sweden)

    Alexander Čaja

    2015-01-01

    Full Text Available Currently, older power electronics and electrotechnics are improvement and at the same time developing new and more efficient devices. These devices produce in their activities a significant part of the heat which, if not effectively drained, causing damage to these elements. In this case, it is important to develop new and more efficient cooling system. The most widespread of modern methods of cooling is the cooling by heat pipe. This contribution is aimed at cooling the insulated-gate bipolar transistor (IGBT elements by loop heat pipe (LHP. IGBTs are very prone to damage due to high temperatures, and therefore is the important that the surface temperature was below 100°C. It was therefore created a model that examined what impact of surface temperature on the IGBT element and heat removal at different load and constant ambient temperature.

  12. Reconstruction of MODIS daily land surface temperature under clouds

    Science.gov (United States)

    Sun, L.; Gao, F.; Chen, Z.; Song, L.; Xie, D.

    2015-12-01

    Land surface temperature (LST), generally defined as the skin temperature of the Earth's surface, controls the process of evapotranspiration, surface energy balance, soil moisture change and climate change. Moderate Resolution Imaging Spectrometer (MODIS) is equipped with 1km resolution thermal sensor andcapable of observing the earth surface at least once per day.Thermal infrared bands cannot penetrate cloud, which means we cannot get consistency drought monitoring condition at one area. However, the cloudy-sky conditions represent more than half of the actual day-to-day weather around the global. In this study, we developed an LST filled model based on the assumption that under good weather condition, LST difference between two nearby pixels are similar among the closest 8 days. We used all the valid pixels covered by a 9*9 window to reconstruct the gap LST. Each valid pixel is assigned a weight which is determined by the spatial distance and the spectral similarity. This model is applied in the Middle-East of China including Gansu, Ningxia, Shaanxi province. The terrain is complicated in this area including plain and hill. The MODIS daily LST product (MOD11A3) from 2000 to 2004 is tested. Almost all the gap pixels are filled, and the terrain information is reconstructed well and smoothly. We masked two areas in order to validate the model, one located in the plain, another located in the hill. The correlation coefficient is greater than 0.8, even up to 0.92 in a few days. We also used ground measured day maximum and mean surface temperature to valid our model. Although both the temporal and spatial scale are different between ground measured temperature and MODIS LST, they agreed well in all the stations. This LST filled model is operational because it only needs LST and reflectance, and does not need other auxiliary information such as climate factors. We will apply this model to more regions in the future.

  13. Piglets’ Surface Temperature Change at Different Weights at Birth

    Science.gov (United States)

    Caldara, Fabiana Ribeiro; dos Santos, Luan Sousa; Machado, Sivanilza Teixeira; Moi, Marta; de Alencar Nääs, Irenilza; Foppa, Luciana; Garcia, Rodrigo Garófallo; de Kássia Silva dos Santos, Rita

    2014-01-01

    The study was carried out in order to verify the effects of piglets’ weight at birth on their surface temperature change (ST) after birth, and its relationship with ingestion time of colostrum. Piglets from four different sows were weighed at birth and divided into a totally randomized design with three treatments according to birth weight (PBW): T1 - less than 1.00 kg, T2 - 1.00 to 1.39 kg, and T3 - higher than or equal to 1.40 kg. The time spent for the first colostrum ingestion was recorded (TFS). Images of piglets’ surface by thermal imaging camera were recorded at birth (STB) and 15, 30, 45, 60, and 120 min after birth. The air temperature and relative humidity were recorded every 30 min and the indexes of temperature and humidity (THI) were calculated. A ST drop after 15 min from birth was observed, increasing again after sixty minutes. Positive correlations were found between the PBW and the ST at 30 and 45 min after birth. The PBW was negatively correlated with the TFS. The THI showed high negative correlations (−0.824 and −0.815) with STB and after 15 min from birth. The piglet’s surface temperature at birth was positively correlated with temperature thereof to 15 min, influencing therefore the temperatures in the interval of 45 to 120 min. The birth weight contributes significantly to postnatal hypothermia and consequently to the time it takes for piglets ingest colostrum, requiring special attention to those of low birth weight. PMID:25049971

  14. Piglets' surface temperature change at different weights at birth.

    Science.gov (United States)

    Caldara, Fabiana Ribeiro; Dos Santos, Luan Sousa; Machado, Sivanilza Teixeira; Moi, Marta; de Alencar Nääs, Irenilza; Foppa, Luciana; Garcia, Rodrigo Garófallo; de Kássia Silva Dos Santos, Rita

    2014-03-01

    The study was carried out in order to verify the effects of piglets' weight at birth on their surface temperature change (ST) after birth, and its relationship with ingestion time of colostrum. Piglets from four different sows were weighed at birth and divided into a totally randomized design with three treatments according to birth weight (PBW): T1 - less than 1.00 kg, T2 - 1.00 to 1.39 kg, and T3 - higher than or equal to 1.40 kg. The time spent for the first colostrum ingestion was recorded (TFS). Images of piglets' surface by thermal imaging camera were recorded at birth (STB) and 15, 30, 45, 60, and 120 min after birth. The air temperature and relative humidity were recorded every 30 min and the indexes of temperature and humidity (THI) were calculated. A ST drop after 15 min from birth was observed, increasing again after sixty minutes. Positive correlations were found between the PBW and the ST at 30 and 45 min after birth. The PBW was negatively correlated with the TFS. The THI showed high negative correlations (-0.824 and -0.815) with STB and after 15 min from birth. The piglet's surface temperature at birth was positively correlated with temperature thereof to 15 min, influencing therefore the temperatures in the interval of 45 to 120 min. The birth weight contributes significantly to postnatal hypothermia and consequently to the time it takes for piglets ingest colostrum, requiring special attention to those of low birth weight.

  15. Piglets’ Surface Temperature Change at Different Weights at Birth

    Directory of Open Access Journals (Sweden)

    Fabiana Ribeiro Caldara

    2014-03-01

    Full Text Available The study was carried out in order to verify the effects of piglets’ weight at birth on their surface temperature change (ST after birth, and its relationship with ingestion time of colostrum. Piglets from four different sows were weighed at birth and divided into a totally randomized design with three treatments according to birth weight (PBW: T1 - less than 1.00 kg, T2 - 1.00 to 1.39 kg, and T3 - higher than or equal to 1.40 kg. The time spent for the first colostrum ingestion was recorded (TFS. Images of piglets’ surface by thermal imaging camera were recorded at birth (STB and 15, 30, 45, 60, and 120 min after birth. The air temperature and relative humidity were recorded every 30 min and the indexes of temperature and humidity (THI were calculated. A ST drop after 15 min from birth was observed, increasing again after sixty minutes. Positive correlations were found between the PBW and the ST at 30 and 45 min after birth. The PBW was negatively correlated with the TFS. The THI showed high negative correlations (−0.824 and −0.815 with STB and after 15 min from birth. The piglet’s surface temperature at birth was positively correlated with temperature thereof to 15 min, influencing therefore the temperatures in the interval of 45 to 120 min. The birth weight contributes significantly to postnatal hypothermia and consequently to the time it takes for piglets ingest colostrum, requiring special attention to those of low birth weight.

  16. Use of Sensor Imagery Data for Surface Boundary Conditions in Regional Climate Modeling

    Science.gov (United States)

    Choi, Hyun Il

    2011-01-01

    Mesoscale climate and hydrology modeling studies have increased in sophistication and are being run at increasingly higher resolutions. Data resolution sufficiently finer than that of the computational model is required not only to support sophisticated linkages and process interactions at small scales but to assess their cumulative impact at larger scales. The global distributions at fine spatial and temporal scales can be described by means of various senor imagery data collected through remote sensing techniques, sensor image and photo programs, scanning and digitizing skills for existing maps, etc. The availability of global sensor imagery maps facilitates assimilation in land surface models to account for terrestrial dynamics. This study focuses on the use of global imagery data for development and construction of surface boundary conditions (SBCs) specifically designed for mesoscale regional climate model (RCM) applications. The several SBCs are currently presented in a RCM domain for the continent of Asia at 30-km spacing by using sensor imagery data. Geographic Information System (GIS) software application tools are mainly used to convert data information from various raw data onto RCM-specific grids. The raw data sources and processing procedures are elaborated in detail, by which the SBCs can be readily constructed for any specific RCM domain anywhere in the world. PMID:22163982

  17. Bathymetric controls on Pliocene North Atlantic and Arctic sea surface temperature and deepwater production

    Science.gov (United States)

    Robinson, M.M.; Valdes, P.J.; Haywood, A.M.; Dowsett, H.J.; Hill, D.J.; Jones, S.M.

    2011-01-01

    The mid-Pliocene warm period (MPWP; ~. 3.3 to 3.0. Ma) is the most recent interval in Earth's history in which global temperatures reached and remained at levels similar to those projected for the near future. The distribution of global warmth, however, was different than today in that the high latitudes warmed more than the tropics. Multiple temperature proxies indicate significant sea surface warming in the North Atlantic and Arctic Oceans during the MPWP, but predictions from a fully coupled ocean-atmosphere model (HadCM3) have so far been unable to fully predict the large scale of sea surface warming in the high latitudes. If climate proxies accurately represent Pliocene conditions, and if no weakness exists in the physics of the model, then model boundary conditions may be in error. Here we alter a single boundary condition (bathymetry) to examine if Pliocene high latitude warming was aided by an increase in poleward heat transport due to changes in the subsidence of North Atlantic Ocean ridges. We find an increase in both Arctic sea surface temperature and deepwater production in model experiments that incorporate a deepened Greenland-Scotland Ridge. These results offer both a mechanism for the warming in the North Atlantic and Arctic Oceans indicated by numerous proxies and an explanation for the apparent disparity between proxy data and model simulations of Pliocene northern North Atlantic and Arctic Ocean conditions. Determining the causes of Pliocene warmth remains critical to fully understanding comparisons of the Pliocene warm period to possible future climate change scenarios. ?? 2011.

  18. Near–surface air temperature and snow skin temperature comparison from CREST-SAFE station data with MODIS land surface temperature data

    Directory of Open Access Journals (Sweden)

    C. L. Pérez Díaz

    2015-08-01

    Full Text Available Land Surface Temperature (LST is a key variable (commonly studied to understand the hydrological cycle that helps drive the energy balance and water exchange between the Earth's surface and its atmosphere. One observable constituent of much importance in the land surface water balance model is snow. Snow cover plays a critical role in the regional to global scale hydrological cycle because rain-on-snow with warm air temperatures accelerates rapid snow-melt, which is responsible for the majority of the spring floods. Accurate information on near-surface air temperature (T-air and snow skin temperature (T-skin helps us comprehend the energy and water balances in the Earth's hydrological cycle. T-skin is critical in estimating latent and sensible heat fluxes over snow covered areas because incoming and outgoing radiation fluxes from the snow mass and the air temperature above make it different from the average snowpack temperature. This study investigates the correlation between MODerate resolution Imaging Spectroradiometer (MODIS LST data and observed T-air and T-skin data from NOAA-CREST-Snow Analysis and Field Experiment (CREST-SAFE for the winters of 2013 and 2014. LST satellite validation is imperative because high-latitude regions are significantly affected by climate warming and there is a need to aid existing meteorological station networks with the spatially continuous measurements provided by satellites. Results indicate that near-surface air temperature correlates better than snow skin temperature with MODIS LST data. Additional findings show that there is a negative trend demonstrating that the air minus snow skin temperature difference is inversely proportional to cloud cover. To a lesser extent, it will be examined whether the surface properties at the site are representative for the LST properties within the instrument field of view.

  19. Near-surface air temperature and snow skin temperature comparison from CREST-SAFE station data with MODIS land surface temperature data

    Science.gov (United States)

    Pérez Díaz, C. L.; Lakhankar, T.; Romanov, P.; Muñoz, J.; Khanbilvardi, R.; Yu, Y.

    2015-08-01

    Land Surface Temperature (LST) is a key variable (commonly studied to understand the hydrological cycle) that helps drive the energy balance and water exchange between the Earth's surface and its atmosphere. One observable constituent of much importance in the land surface water balance model is snow. Snow cover plays a critical role in the regional to global scale hydrological cycle because rain-on-snow with warm air temperatures accelerates rapid snow-melt, which is responsible for the majority of the spring floods. Accurate information on near-surface air temperature (T-air) and snow skin temperature (T-skin) helps us comprehend the energy and water balances in the Earth's hydrological cycle. T-skin is critical in estimating latent and sensible heat fluxes over snow covered areas because incoming and outgoing radiation fluxes from the snow mass and the air temperature above make it different from the average snowpack temperature. This study investigates the correlation between MODerate resolution Imaging Spectroradiometer (MODIS) LST data and observed T-air and T-skin data from NOAA-CREST-Snow Analysis and Field Experiment (CREST-SAFE) for the winters of 2013 and 2014. LST satellite validation is imperative because high-latitude regions are significantly affected by climate warming and there is a need to aid existing meteorological station networks with the spatially continuous measurements provided by satellites. Results indicate that near-surface air temperature correlates better than snow skin temperature with MODIS LST data. Additional findings show that there is a negative trend demonstrating that the air minus snow skin temperature difference is inversely proportional to cloud cover. To a lesser extent, it will be examined whether the surface properties at the site are representative for the LST properties within the instrument field of view.

  20. Effective boundary condition at a rough surface starting from a slip condition

    CERN Document Server

    Dalibard, Anne-Laure

    2010-01-01

    We consider the homogenization of the Navier-Stokes equation, set in a channel with a rough boundary, of small amplitude and wavelength $\\epsilon$. It was shown recently that, for any non-degenerate roughness pattern, and for any reasonable condition imposed at the rough boundary, the homogenized boundary condition in the limit $\\epsilon = 0$ is always no-slip. We give in this paper error estimates for this homogenized no-slip condition, and provide a more accurate effective boundary condition, of Navier type. Our result extends those obtained in previous works, in which the special case of a Dirichlet condition at the rough boundary was examined.

  1. Temperature-dependent photoluminescence of surface-engineered silicon nanocrystals

    Science.gov (United States)

    Mitra, Somak; Švrček, Vladimir; Macias-Montero, Manual; Velusamy, Tamilselvan; Mariotti, Davide

    2016-01-01

    In this work we report on temperature-dependent photoluminescence measurements (15–300 K), which have allowed probing radiative transitions and understanding of the appearance of various transitions. We further demonstrate that transitions associated with oxide in SiNCs show characteristic vibronic peaks that vary with surface characteristics. In particular we study differences and similarities between silicon nanocrystals (SiNCs) derived from porous silicon and SiNCs that were surface-treated using a radio-frequency (RF) microplasma system. PMID:27296771

  2. Biological control of surface temperature in the Arabian Sea

    Science.gov (United States)

    Sathyendranath, Shubha; Gouveia, Albert D.; Shetye, Satish R.; Ravindran, P.; Platt, Trevor

    1991-01-01

    In the Arabian Sea, the southwest monsoon promotes seasonal upwelling of deep water, which supplies nutrients to the surface layer and leads to a marked increase in phytoplankton growth. Remotely sensed data on ocean color are used here to show that the resulting distribution of phytoplankton exerts a controlling influence on the seasonal evolution of sea surface temperature. This results in a corresponding modification of ocean-atmosphere heat exchange on regional and seasonal scales. It is shown that this biological mechanism may provide an important regulating influence on ocean-atmosphere interactions.

  3. Study on the effect of subcooling on vapor film collapse on high temperature particle surface

    Energy Technology Data Exchange (ETDEWEB)

    Abe, Yutaka; Tochio, Daisuke; Yanagida, Hiroshi [Department of Mechanical Systems Engineering, Yamagata Univ., Yonezawa, Yamagata (Japan)

    2000-11-01

    Thermal detonation model is proposed to describe vapor explosion. According to this model, vapor film on pre-mixed high temperature droplet surface is needed to be collapsed for the trigger of the vapor explosion. It is pointed out that the vapor film collapse behavior is significantly affected by the subcooling of low temperature liquid. However, the effect of subcooling on micro-mechanism of vapor film collapse behavior is not experimentally well identified. The objective of the present research is to experimentally investigate the effect of subcooling on micro-mechanism of film boiling collapse behavior. As the results, it is experimentally clarified that the vapor film collapse behavior in low subcooling condition is qualitatively different from the vapor film collapse behavior in high subcooling condition. In case of vapor film collapse by pressure pulse, homogeneous vapor generation occurred all over the surface of steel particle in low subcooling condition. On the other hand, heterogeneous vapor generation was observed for higher subcooling condition. In case of vapor film collapse spontaneously, fluctuation of the gas-liquid interface after quenching propagated from bottom to top of the steel particle heterogeneously in low subcooling condition. On the other hand, simultaneous vapor generation occurred for higher subcooling condition. And the time transient of pressure, particle surface temperature, water temperature and visual information were simultaneously measured in the vapor film collapse experiment by external pressure pulse. Film thickness was estimated by visual data processing technique with the pictures taken by the high-speed video camera. Temperature and heat flux at the vapor-liquid interface were estimated by solving the heat condition equation with the measured pressure, liquid temperature and vapor film thickness as boundary conditions. Movement of the vapor-liquid interface were estimated with the PIV technique with the visual observation

  4. A moving boundary solution for solidification of lava lake and magma intrusion in the presence of time-varying contact temperature

    Indian Academy of Sciences (India)

    Ajay Manglik

    2005-04-01

    During the solidification of a lava lake heat is released convectively from the top surface as well as conductively into the country rock from the base, leading to non-uniform solidification. The upper solidified layer grows at a faster rate than the lower solidified layer. Similarly, solidification of magma intrusion within the crust is also non-uniform due to the presence of thermal gradient in the crust. Available analytical solution for solidification of a melt layer assumes only symmetric cooling about the centre of the layer. In the present work a moving boundary solution for thermal evolution and non-uniform solidification of a melt layer incorporating time-varying contact temperature conditions at both of its boundaries is developed. The solution is obtained by using the Fourier spectral approach in the space domain and a modified finite difference scheme in the time domain, and is validated with available analytical solutions for simple cases and a semi-analytical solution for the case involving temperature gradient in the country rock. This solution can be used to analyse solidification of lava lakes and magma intrusions experiencing time-dependent temperature variation at their contacts with the country rock.

  5. Chemical nature of alkaline polyphosphate boundary film at heated rubbing surfaces

    Science.gov (United States)

    Wan, Shanhong; Tieu, A. Kiet; Zhu, Qiang; Zhu, Hongtao; Cui, Shaogang; Mitchell, David R. G.; Kong, Charlie; Cowie, Bruce; Denman, John A.; Liu, Rong

    2016-05-01

    Alkaline polyphosphate has been demonstrated to be able to reduce significant wear and friction of sliding interfaces under heavy loads (>1 GPa) and elevated temperature (800 °C and above) conditions, e.g. hot metal manufacturing. The chemical composition and fine structure of polyphosphate lubricating film is not well understood as well as the role of alkaline elements within the reaction film at hot rubbing surface. This work makes use of the coupling surface analytical techniques on the alkaline polyphosphate tribofilm, XANES, TOF-SIMS and FIB/TEM. The data show the composition in gradient distribution and trilaminar structure of tribofilm: a shorter chain phosphate overlying a long chain polyphosphate that adheres onto oxide steel base through a short chain phosphate. The chemical hardness model well explains the anti-abrasive mechanism of alkaline polyphosphate at elevated temperatures and also predicts a depolymerisation and simultaneous cross-linking of the polyphosphate glass. The role of alkaline elements in the lubrication mechanism is especially explained. This work firstly serves as a basis for a detailed study of alkaline polyphosphate tribofilm at temperature over 600 °C.

  6. Estimating Temperature Fields from MODIS Land Surface Temperature and Air Temperature Observations in a Sub-Arctic Alpine Environment

    Directory of Open Access Journals (Sweden)

    Scott N. Williamson

    2014-01-01

    Full Text Available Spatially continuous satellite infrared temperature measurements are essential for understanding the consequences and drivers of change, at local and regional scales, especially in northern and alpine environments dominated by a complex cryosphere where in situ observations are scarce. We describe two methods for producing daily temperature fields using MODIS “clear-sky” day-time Land Surface Temperatures (LST. The Interpolated Curve Mean Daily Surface Temperature (ICM method, interpolates single daytime Terra LST values to daily means using the coincident diurnal air temperature curves. The second method calculates daily mean LST from daily maximum and minimum LST (MMM values from MODIS Aqua and Terra. These ICM and MMM models were compared to daily mean air temperatures recorded between April and October at seven locations in southwest Yukon, Canada, covering characteristic alpine land cover types (tundra, barren, glacier at elevations between 1,408 m and 2,319 m. Both methods for producing mean daily surface temperatures have advantages and disadvantages. ICM signals are strongly correlated with air temperature (R2 = 0.72 to 0.86, but have relatively large variability (RMSE = 4.09 to 4.90 K, while MMM values had a stronger correlation to air temperature (R2 = 0.90 and smaller variability (RMSE = 2.67 K. Finally, when comparing 8-day LST averages, aggregated from the MMM method, to air temperature, we found a high correlation (R2 = 0.84 with less variability (RMSE = 1.54 K. Where the trend was less steep and the y-intercept increased by 1.6 °C compared to the daily correlations. This effect is likely a consequence of LST temperature averages being differentially affected by cloud cover over warm and cold surfaces. We conclude that satellite infrared skin temperature (e.g., MODIS LST, which is often aggregated into multi-day composites to mitigate data reductions caused by cloud cover, changes in its relationship to air temperature

  7. Calibration plan for the sea and land surface temperature radiometer

    Science.gov (United States)

    Smith, David L.; Nightingale, Tim J.; Mortimer, Hugh; Middleton, Kevin; Edeson, Ruben; Cox, Caroline V.; Mutlow, Chris T.; Maddison, Brian J.

    2013-10-01

    The Sea and Land Surface Temperature Radiometer (SLSTR) to be flown on ESA's Sentinel-3 mission is a multichannel scanning radiometer that will continue the 21-year datasets of the Along Track Scanning Radiometer (ATSR) series. As its name implies, measurements from SLSTR will be used to retrieve global sea surface temperatures to an uncertainty of SLSTR instrument, infrared calibration sources and alignment equipment. The calibration rig has been commissioned and results of these tests will be presented. Finally the authors will present the planning for the on-orbit monitoring and calibration activities to ensure that calibration is maintained. These activities include vicarious calibration techniques that have been developed through previous missions, and the deployment of ship-borne radiometers.

  8. Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems

    Directory of Open Access Journals (Sweden)

    V. Rossi

    2009-08-01

    Full Text Available Eastern Boundary Upwelling Systems (EBUS are characterized by a high productivity of plankton associated with large commercial fisheries, thus playing key biological and socio-economical roles. Since they are populated by several physical oceanic structures such as filaments and eddies, which interact with the biological processes, it is a major challenge to study this sub- and mesoscale activity in connection with the chlorophyll distribution. The aim of this work is to make a comparative study of these four upwelling systems focussing on their surface stirring, using the Finite Size Lyapunov Exponents (FSLEs, and their biological activity, based on satellite data. First, the spatial distribution of horizontal mixing is analysed from time averages and from probability density functions of FSLEs, which allow us to divide each areas in two different subsystems. Then we studied the temporal variability of surface stirring focussing on the annual and seasonal cycle. We also proposed a ranking of the four EBUS based on the averaged mixing intensity. When investigating the links with chlorophyll concentration, the previous subsystems reveal distinct biological signatures. There is a global negative correlation between surface horizontal mixing and chlorophyll standing stocks over the four areas. To try to better understand this inverse relationship, we consider the vertical dimension by looking at the Ekman-transport and vertical velocities. We suggest the possibility of a changing response of the phytoplankton to sub/mesoscale turbulence, from a negative effect in the very productive coastal areas to a positive one in the open ocean. This study provides new insights for the understanding of the variable biological productivity in the ocean, which results from both dynamics of the marine ecosystem and of the 3-D turbulent medium.

  9. Estimation of Regional Evapotranspiration Using Remotely Sensed Land Surface Temperature. Part 2: Application of Equilibrium Evaporation Model to Estimate Evapotranspiration by Remote Sensing Technique. [Japan

    Science.gov (United States)

    Kotoda, K.; Nakagawa, S.; Kai, K.; Yoshino, M. M.; Takeda, K.; Seki, K.

    1985-01-01

    In a humid region like Japan, it seems that the radiation term in the energy balance equation plays a more important role for evapotranspiration then does the vapor pressure difference between the surface and lower atmospheric boundary layer. A Priestley-Taylor type equation (equilibrium evaporation model) is used to estimate evapotranspiration. Net radiation, soil heat flux, and surface temperature data are obtained. Only temperature data obtained by remotely sensed techniques are used.

  10. A surface acoustic wave ICP sensor with good temperature stability.

    Science.gov (United States)

    Zhang, Bing; Hu, Hong; Ye, Aipeng; Zhang, Peng

    2017-07-20

    Intracranial pressure (ICP) monitoring is very important for assessing and monitoring hydrocephalus, head trauma and hypertension patients, which could lead to elevated ICP or even devastating neurological damage. The mortality rate due to these diseases could be reduced through ICP monitoring, because precautions can be taken against the brain damage. This paper presents a surface acoustic wave (SAW) pressure sensor to realize ICP monitoring, which is capable of wireless and passive transmission with antenna attached. In order to improve the temperature stability of the sensor, two methods were adopted. First, the ST cut quartz was chosen as the sensor substrate due to its good temperature stability. Then, a differential temperature compensation method was proposed to reduce the effects of temperature. Two resonators were designed based on coupling of mode (COM) theory and the prototype was fabricated and verified using a system established for testing pressure and temperature. The experiment result shows that the sensor has a linearity of 2.63% and hysteresis of 1.77%. The temperature stability of the sensor has been greatly improved by using the differential compensation method, which validates the effectiveness of the proposed method.

  11. A New Estimate of the Earth's Land Surface Temperature History

    Science.gov (United States)

    Muller, R. A.; Curry, J. A.; Groom, D.; Jacobsen, B.; Perlmutter, S.; Rohde, R. A.; Rosenfeld, A.; Wickham, C.; Wurtele, J.

    2011-12-01

    The Berkeley Earth Surface Temperature team has re-evaluated the world's atmospheric land surface temperature record using a linear least-squares method that allow the use of all the digitized records back to 1800, including short records that had been excluded by prior groups. We use the Kriging method to estimate an optimal weighting of stations to give a world average based on uniform weighting of the land surface. We have assembled a record of the available data by merging 1.6 billion temperature reports from 16 pre-existing data archives; this data base will be made available for public use. The former Global Historic Climatology Network (GHCN) monthly data base shows a sudden drop in the number of stations reporting monthly records from 1980 to the present; we avoid this drop by calculating monthly averages from the daily records. By using all the data, we reduce the effects of potential data selection bias. We make an independent estimate of the urban heat island effect by calculating the world land temperature trends based on stations chosen to be far from urban sites. We calculate the effect of poor station quality, as documented in the US by the team led by Anthony Watts by estimating the temperature trends based solely on the stations ranked good (1,2 or 1,2,3 in the NOAA ranking scheme). We avoid issues of homogenization bias by using raw data; at times when the records are discontinuous (e.g. due to station moves) we break the record into smaller segments and analyze those, rather than attempt to correct the discontinuity. We estimate the uncertainties in the final results using the jackknife procedure developed by J. Tukey. We calculate spatial uncertainties by measuring the effects of geographical exclusion on recent data that have good world coverage. The results we obtain are compared to those published by the groups at NOAA, NASA-GISS, and Hadley-CRU in the UK.

  12. Effect of floor surface temperature on blood flow and skin temperature in the foot.

    Science.gov (United States)

    Song, G-S

    2008-12-01

    A total of 16 healthy college students participated as subjects to elucidate the hypothesis that blood flow and skin temperature in foot are affected by the floor surface temperature. The floor surface temperature was controlled by varying the temperature of water (tw) flowing underneath the floor, and it ranged from tw 15 to 40 degrees C at 5 degrees C intervals. The blood flow rate was measured in the dorsal right toe, and skin temperatures were measured for 60 min at 8 points: the neck, right scapular, left hand, right shin, left bottom of the toe, right instep, left finger, and rectum. The blood flow rate in the foot tissue was increased until the foot skin temperature warmed up to 34 degrees C (P = 0.000). The final skin temperatures on the bottom of the toe were 19.4 +/- 2.44 degrees C for tw 15 degrees C, 22.4 +/- 2.45 degrees C for tw 20 degrees C, 24.8 +/- 2.80 degrees C for tw 25 degrees C, 27.7 +/- 2.13 degrees C for tw 30 degrees C, 30.6 +/- 2.06 degrees C for tw 35 degrees C, 33.2 +/- 1.45 degrees C for tw 40 degrees C, 34.2 +/- 1.55 degrees C for tw 45 degrees C, and 35.2 +/- 1.65 degrees C for tw 50 degrees C. Considering blood flow and comfort, the partial floor heating system is suggested and the recommended floor surface temperature range is 27-33 degrees C. A warm floor surface can serve to satisfy occupants when the ambient temperature maintained at 20 degrees C which represents an energy conscious temperature. A warm floor can induce high blood perfusion in the feet and consequently improve an occupant's health by treating many vascular-related disorders. Even in a well-insulated residential building, a partially heated floor system could prevent overheating while providing surface warmth.

  13. Actual evaporation estimation from infrared measurement of soil surface temperature

    Directory of Open Access Journals (Sweden)

    Davide Pognant

    2013-09-01

    Full Text Available Within the hydrological cycle, actual evaporation represents the second most important process in terms of volumes of water transported, second only to the precipitation phenomena. Several methods for the estimation of the Ea were proposed by researchers in scientific literature, but the estimation of the Ea from potential evapotranspiration often requires the knowledge of hard-to-find parameters (e.g.: vegetation morphology, vegetation cover, interception of rainfall by the canopy, evaporation from the canopy surface and uptake of water by plant roots and many existing database are characterized by missing or incomplete information that leads to a rough estimation of the actual evaporation amount. Starting from the above considerations, the aim of this study is to develop and validate a method for the estimation of the Ea based on two steps: i the potential evaporation estimation by using the meteorological data (i.e. Penman-Monteith; ii application of a correction factor based on the infrared soil surface temperature measurements. The dataset used in this study were collected during two measurement campaigns conducted both in a plain testing site (Grugliasco, Italy, and in a mountain South-East facing slope (Cogne, Italy. During those periods, hourly measurement of air temperature, wind speed, infrared surface temperature, soil heat flux, and soil water content were collected. Results from the dataset collected in the two testing sites show a good agreement between the proposed method and reference methods used for the Ea estimation.

  14. Land surface temperature shaped by urban fractions in megacity region

    Science.gov (United States)

    Zhang, Xiaoxuan; Hu, Yonghong; Jia, Gensuo; Hou, Meiting; Fan, Yanguo; Sun, Zhongchang; Zhu, Yuxiang

    2017-02-01

    Large areas of cropland and natural vegetation have been replaced by impervious surfaces during the recent rapid urbanization in China, which has resulted in intensified urban heat island effects and modified local or regional warming trends. However, it is unclear how urban expansion contributes to local temperature change. In this study, we investigated the relationship between land surface temperature (LST) change and the increase of urban land signals. The megacity of Tianjin was chosen for the case study because it is representative of the urbanization process in northern China. A combined analysis of LST and urban land information was conducted based on an urban-rural transect derived from Landsat 8 Thermal Infrared Sensor (TIRS), Terra Moderate Resolution Imaging Spectrometer (MODIS), and QuickBird images. The results indicated that the density of urban land signals has intensified within a 1-km2 grid in the urban center with an impervious land fraction >60 %. However, the construction on urban land is quite different with low-/mid-rise buildings outnumbering high-rise buildings in the urban-rural transect. Based on a statistical moving window analysis, positive correlation ( R 2 > 0.9) is found between LST and urban land signals. Surface temperature change (ΔLST) increases by 0.062 °C, which was probably caused by the 1 % increase of urbanized land (ΔIF) in this case region.

  15. High temperature surface degradation of III-V nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Vartuli, C.B.; Pearton, S.J.; Abernathy, C.R.; MacKenzie, J.D.; Lambers, E.S. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States)

    1996-05-01

    The surface stoichiometry, surface morphology and electrical conductivity of AlN, GaN, InN, InGaN and InAlN was examined at rapid thermal annealing temperatures up to 1,150 C. The sheet resistance of the AlN dropped steadily with annealing, but the surface showed signs of roughening only above 1,000 C. Auger Electronic Spectroscopy (AES) analysis showed little change in the surface stoichiometry even at 1,150 C. GaN root mean square (RMS) surface roughness showed an overall improvement with annealing, but the surface became pitted at 1,000 C, at which point the sheet resistance also dropped by several orders of magnitude, and AES confirmed a loss of N from the surface. The InN surface had roughened considerably even at 650 C, and scanning electron microscopy (SEM) showed significant degradation. In contrast to the binary nitrides the sheet resistance of InAlN was found to increase by {approximately} 10{sup 2} from the as grown value after annealing at 800 C and then remain constant up to 1,000 C, while that of InGaN increased rapidly above 700 C. The RMS roughness increased above 800 C and 700 C respectively for InAlN and InGaN samples. In droplets began to form on the surface at 900 C for InAlN and at 800 C for InGaN, and then evaporate at 1,000 C leaving pits. AES analysis showed a decrease in the N concentration in the top 500 {angstrom} of the sample for annealing {ge} 800 C in both materials.

  16. Thermal resistance optimization of GaN/substrate stacks considering thermal boundary resistance and temperature-dependent thermal conductivity

    Science.gov (United States)

    Park, K.; Bayram, C.

    2016-10-01

    Here, we investigate the effects of thermal boundary resistance (TBR) and temperature-dependent thermal conductivity on the thermal resistance of GaN/substrate stacks. A combination of parameters such as substrates {diamond, silicon carbide, silicon, and sapphire}, thermal boundary resistance {10-60 m2K/GW}, heat source lengths {10 nm-20 μm}, and power dissipation levels {1-8 W} are studied by using technology computer-aided design (TCAD) software Synopsys. Among diamond, silicon carbide, silicon, and sapphire substrates, the diamond provides the lowest thermal resistance due to its superior thermal conductivity. We report that due to non-zero thermal boundary resistance and localized heating in GaN-based high electron mobility transistors, an optimum separation between the heat source and substrate exists. For high power (i.e., 8 W) heat dissipation on high thermal conductive substrates (i.e., diamond), the optimum separation between the heat source and substrate becomes submicron thick (i.e., 500 nm), which reduces the hotspot temperature as much as 50 °C compared to conventional multi-micron thick case (i.e., 4 μm). This is attributed to the thermal conductivity drop in GaN near the heat source. Improving the TBR between GaN and diamond increases temperature reduction by our further approach. Overall, we provide thermal management design guidelines for GaN-based devices.

  17. Surface Tensions and Their Variations with Temperature and Impurities

    Science.gov (United States)

    Hardy, S. C.; Fine, J.

    1985-01-01

    The surface tensions in this work were determined using the sessile drop technique. This method is based on a comparison of the profile of a liquid drop with the profile calculated by solving the Young-Laplace equation. The comparison can be made in several ways; the traditional Bashforth-Adams procedure was used in conjunction with recently calculated drop shape tables which virtually eliminate interpolation errors. Although previous study has found little difference in measurements with pure and oxygen doped silicon, there is other evidence suggesting that oxygen in dilute concentrations severely depresses the surface tension of silicon. The surface tension of liquid silicon in purified argon atmospheres was measured. A temperature coefficient near -0.28 mJ/square meters K was found. The experiments show a high sensitivity of the surface tension to what is believed are low concentrations of oxygen. Thus one cannot rule out some effect of low levels of oxygen in the results. However, the highest surface tension values obtained in conditions which minimized the residual oxygen pressure are in good agreement with a previous measurement in pure hydrogen. Therefore, depression of the surface tension by oxygen is insignificant in these measurements.

  18. HEAT TRANSFER IN THREE DIMENSIONAL MHD BOUNDARY LAYER FLOW OVER A CONTINUOUS POROUS SURFACE MOVING IN A PARALLEL FREE STREAM

    Directory of Open Access Journals (Sweden)

    KHEM CHAND

    2011-07-01

    Full Text Available The heat transfer and hydromagnetic boundary layer flow of an electrically conducting viscous ,incompressible fluid over a continuous flat surface moving in a parallel free stream is investigated. The porous infinite surface is subjected to a slightly sinusoidal transverse suction velocity distribution. The flow becomes three dimensional due to this type of suction velocity without taking into account the induced magnetic field; the mathematical analysis is presented for the hydromagnetic laminar boundary layer flow. For the asymptotic flow condition, the components of the surface skin friction and the rate of heat transfer are obtained. During discussion it is found that with the increase of Hartmann number M, the skin friction factor F1 increase sharply for lower values of theReynolds number, but for the large value it increases steadily. But if the surface velocity is more than that of free stream velocity then the reverse trend is observed.

  19. Discretization of three-dimensional free surface flows and moving boundary problems via elliptic grid methods based on variational principles

    Science.gov (United States)

    Fraggedakis, D.; Papaioannou, J.; Dimakopoulos, Y.; Tsamopoulos, J.

    2017-09-01

    A new boundary-fitted technique to describe free surface and moving boundary problems is presented. We have extended the 2D elliptic grid generator developed by Dimakopoulos and Tsamopoulos (2003) [19] and further advanced by Chatzidai et al. (2009) [18] to 3D geometries. The set of equations arises from the fulfillment of the variational principles established by Brackbill and Saltzman (1982) [21], and refined by Christodoulou and Scriven (1992) [22]. These account for both smoothness and orthogonality of the grid lines of tessellated physical domains. The elliptic-grid equations are accompanied by new boundary constraints and conditions which are based either on the equidistribution of the nodes on boundary surfaces or on the existing 2D quasi-elliptic grid methodologies. The capabilities of the proposed algorithm are first demonstrated in tests with analytically described complex surfaces. The sequence in which these tests are presented is chosen to help the reader build up experience on the best choice of the elliptic grid parameters. Subsequently, the mesh equations are coupled with the Navier-Stokes equations, in order to reveal the full potential of the proposed methodology in free surface flows. More specifically, the problem of gas assisted injection in ducts of circular and square cross-sections is examined, where the fluid domain experiences extreme deformations. Finally, the flow-mesh solver is used to calculate the equilibrium shapes of static menisci in capillary tubes.

  20. Computer vision-based recognition of liquid surfaces and phase boundaries in transparent vessels, with emphasis on chemistry applications

    OpenAIRE

    Eppel, Sagi; Kachman, Tal

    2014-01-01

    The ability to recognize the liquid surface and the liquid level in transparent containers is perhaps the most commonly used evaluation method when dealing with fluids. Such recognition is essential in determining the liquid volume, fill level, phase boundaries and phase separation in various fluid systems. The recognition of liquid surfaces is particularly important in solution chemistry, where it is essential to many laboratory techniques (e.g., extraction, distillation, titration). A gener...

  1. Numerical simulations of sink-flow boundary layers over rough surfaces

    Science.gov (United States)

    Yuan, J.; Piomelli, U.

    2014-01-01

    Turbulent sink flows over smooth or rough walls with sand-grain roughness are studied using large-eddy and direct numerical simulations. Mild and strong levels of acceleration are applied, yielding a wide range of Reynolds number (Reθ = 372 - 2748) and cases close to the reverse-transitional state. Flow acceleration and roughness are shown to exert opposite effects on boundary-layer integral parameters, on the Reynolds stresses, budgets of turbulent kinetic energy, and properties of turbulent structures in the vicinity of the rough surface; statistics exhibit similarity when plotted using inner scaling for cases with the same roughness Reynolds number, k+. Acceleration leads to a decrease of k+, while roughness increases it. For cases with higher k+, the low-speed streaks become destabilized, and turbulent structures near the wall are distributed more uniformly in the wall-parallel plane; they are less extended in the streamwise direction, but more densely packed. Higher k+ also causes decorrelation of the outer-layer hairpin packets with the near-wall structures, probably due to the direct impact of random roughness elements on the hairpin legs. Wall-similarity applies for the fully turbulent cases, in which the outer-layer turbulent statistics are affected by acceleration only. It is shown that being in the hydraulically smooth regime is a necessary condition for reverse-transition, supporting the idea that relaminarization starts from the inner region, where roughness effects dominate.

  2. Eddy Surface properties and propagation at Southern Hemisphere western boundary current systems

    Directory of Open Access Journals (Sweden)

    G. S. Pilo

    2015-02-01

    Full Text Available Oceanic eddies occur in all world oceans, but are more energetic when associated to western boundary currents (WBC systems. In these regions, eddies play an important role on mixing and energy exchange. Therefore, it is important to quantify and qualify eddies occurring within these systems. Previous studies performed eddy censuses in Southern Hemisphere WBC systems. However, important aspects of local eddy population are still unknown. Main questions to be answered relate to eddies' spatial distribution, propagation and lifetime within each system. Here, we use a global eddy dataset to qualify eddies based on their surface characteristics at the Agulhas Current (AC, the Brazil Current (BC and the East Australian Current (EAC Systems. We show that eddy propagation within each system is highly forced by the local mean flow and bathymetry. In the AC System, eddy polarity dictates its propagation distance. BC system eddies do not propagate beyond the Argentine Basin, and are advected by the local ocean circulation. EAC System eddies from both polarities cross south of Tasmania, but only anticyclonics reach the Great Australian Bight. Eddies in all systems and from both polarities presented a geographical segregation according to size. Large eddies occur along the Agulhas Retroflection, the Agulhas Return Current, the Brazil-Malvinas Confluence and the Coral Sea. Small eddies occur in the systems southernmost domains. Understanding eddies' propagation helps to establish monitoring programs, and to better understand how these features would affect local mixing.

  3. Constraining Planetary Boundary Layer Retrievals with Surface Reflections from GNSS Radio Occultation Measurements

    Science.gov (United States)

    Ao, C. O.; Shume, E. B.; Hajj, G. A.; Meehan, T. K.

    2016-12-01

    In an earlier study, we demonstrated that grazing surface reflection observed from GNSS radio occultation (RO) data yields frequency shifts that are sensitive to refractivity within the planetary boundary layer (PBL). In this presentation, we show our latest progress in retrieving PBL refractivity using a combination of direct and reflected RO data. Through forward simulations, we first assess how the reflected Doppler frequency will vary as a function of refractivity parameters in the PBL. Next, we describe our method for extracting the reflected Doppler signal from actual COSMIC and TerraSAR-X observations and discuss its associated uncertainty. We focus our attention to RO soundings from the subtropical Eastern oceans where large negative refractivity biases within the PBL have been reported. We investigate the feasibility of using the inferred reflected signal to correct the negative bias. Finally, we discuss how future RO observations such as those from COSMIC-2 can be enhanced to provide stronger reflection signals through changes in the GNSS receiver configurations.

  4. Construction of boundary-surface-based Chinese female astronaut computational phantom and proton dose estimation.

    Science.gov (United States)

    Sun, Wenjuan; Jia, Xianghong; Xie, Tianwu; Xu, Feng; Liu, Qian

    2013-03-01

    With the rapid development of China's space industry, the importance of radiation protection is increasingly prominent. To provide relevant dose data, we first developed the Visible Chinese Human adult Female (VCH-F) phantom, and performed further modifications to generate the VCH-F Astronaut (VCH-FA) phantom, incorporating statistical body characteristics data from the first batch of Chinese female astronauts as well as reference organ mass data from the International Commission on Radiological Protection (ICRP; both within 1% relative error). Based on cryosection images, the original phantom was constructed via Non-Uniform Rational B-Spline (NURBS) boundary surfaces to strengthen the deformability for fitting the body parameters of Chinese female astronauts. The VCH-FA phantom was voxelized at a resolution of 2 × 2 × 4 mm(3)for radioactive particle transport simulations from isotropic protons with energies of 5000-10 000 MeV in Monte Carlo N-Particle eXtended (MCNPX) code. To investigate discrepancies caused by anatomical variations and other factors, the obtained doses were compared with corresponding values from other phantoms and sex-averaged doses. Dose differences were observed among phantom calculation results, especially for effective dose with low-energy protons. Local skin thickness shifts the breast dose curve toward high energy, but has little impact on inner organs. Under a shielding layer, organ dose reduction is greater for skin than for other organs. The calculated skin dose per day closely approximates measurement data obtained in low-Earth orbit (LEO).

  5. Blocking effect of twin boundaries on partial dislocation emission from void surfaces.

    Science.gov (United States)

    Zhang, Lifeng; Zhou, Haofei; Qu, Shaoxing

    2012-03-02

    Recent discovery that nanoscale twin boundaries can be introduced in ultrafine-grained metals to improve strength and ductility has renewed interest in the mechanical behavior and deformation mechanisms of these nanostructured materials. By controlling twin boundary spacing, the effect of twin boundaries on void growth is investigated by using atomistic simulation method. The strength is significantly enhanced due to the discontinuous slip system associated with these coherent interfaces. Atomic-scale mechanisms underlying void growth, as well as the interaction between twin boundaries and the void, are revealed in details.

  6. Martian Surface Boundary Layer Characterization: Enabling Environmental Data for Science, Engineering and Human Exploration

    Science.gov (United States)

    England, C.

    2000-01-01

    For human or large robotic exploration of Mars, engineering devices such as power sources will be utilized that interact closely with the Martian environment. Heat sources for power production, for example, will use the low ambient temperature for efficient heat rejection. The Martian ambient, however, is highly variable, and will have a first order influence on the efficiency and operation of all large-scale equipment. Diurnal changes in temperature, for example, can vary the theoretical efficiency of power production by 15% and affect the choice of equipment, working fluids, and operating parameters. As part of the Mars Exploration program, missions must acquire the environmental data needed for design, operation and maintenance of engineering equipment including the transportation devices. The information should focus on the variability of the environment, and on the differences among locations including latitudes, altitudes, and seasons. This paper outlines some of the WHY's, WHAT's and WHERE's of the needed data, as well as some examples of how this data will be used. Environmental data for engineering design should be considered a priority in Mars Exploration planning. The Mars Thermal Environment Radiator Characterization (MTERC), and Dust Accumulation and Removal Technology (DART) experiments planned for early Mars landers are examples of information needed for even small robotic missions. Large missions will require proportionately more accurate data that encompass larger samples of the Martian surface conditions. In achieving this goal, the Mars Exploration program will also acquire primary data needed for understanding Martian weather, surface evolution, and ground-atmosphere interrelationships.

  7. Martian Surface Boundary Layer Characterization: Enabling Environmental Data for Science, Engineering and Human Exploration

    Science.gov (United States)

    England, C.

    2000-01-01

    For human or large robotic exploration of Mars, engineering devices such as power sources will be utilized that interact closely with the Martian environment. Heat sources for power production, for example, will use the low ambient temperature for efficient heat rejection. The Martian ambient, however, is highly variable, and will have a first order influence on the efficiency and operation of all large-scale equipment. Diurnal changes in temperature, for example, can vary the theoretical efficiency of power production by 15% and affect the choice of equipment, working fluids, and operating parameters. As part of the Mars Exploration program, missions must acquire the environmental data needed for design, operation and maintenance of engineering equipment including the transportation devices. The information should focus on the variability of the environment, and on the differences among locations including latitudes, altitudes, and seasons. This paper outlines some of the WHY's, WHAT's and WHERE's of the needed data, as well as some examples of how this data will be used. Environmental data for engineering design should be considered a priority in Mars Exploration planning. The Mars Thermal Environment Radiator Characterization (MTERC), and Dust Accumulation and Removal Technology (DART) experiments planned for early Mars landers are examples of information needed for even small robotic missions. Large missions will require proportionately more accurate data that encompass larger samples of the Martian surface conditions. In achieving this goal, the Mars Exploration program will also acquire primary data needed for understanding Martian weather, surface evolution, and ground-atmosphere interrelationships.

  8. Fractional boundary layer flow and radiation heat transfer of MHD viscoelastic fluid over an unsteady stretching surface

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Bingyu; Zheng, Liancun, E-mail: liancunzheng@ustb.edu.cn; Chen, Shengting [School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-10-15

    This paper presents an investigation for magnetohydrodynamic (MHD) viscoelastic fluid boundary layer flow and radiation heat transfer over an unsteady stretching sheet in presence of heat source. Time dependent fractional derivative is first introduced in formulating the boundary layer equations. Numerical solutions are obtained by using the finite difference scheme and L1-algorithm approximation. Results indicate that the proposed model describes a basic delaying times framework for viscoelastic flow and radiation heat transfer. The effects of involved parameters on velocity and temperature fields are shown graphically and analyzed in detail.

  9. Fractional boundary layer flow and radiation heat transfer of MHD viscoelastic fluid over an unsteady stretching surface

    Directory of Open Access Journals (Sweden)

    Bingyu Shen

    2015-10-01

    Full Text Available This paper presents an investigation for magnetohydrodynamic (MHD viscoelastic fluid boundary layer flow and radiation heat transfer over an unsteady stretching sheet in presence of heat source. Time dependent fractional derivative is first introduced in formulating the boundary layer equations. Numerical solutions are obtained by using the finite difference scheme and L1-algorithm approximation. Results indicate that the proposed model describes a basic delaying times framework for viscoelastic flow and radiation heat transfer. The effects of involved parameters on velocity and temperature fields are shown graphically and analyzed in detail.

  10. SU(2) lattice gauge theory at non-zero temperature with fixed holonomy boundary condition

    CERN Document Server

    Ilgenfritz, E M; Müller-Preussker, M; Veselov, A I

    2001-01-01

    We study SU(2) lattice gauge theory at $T>0$ in a finite box with fixed holonomy value at the spatial boundary. We search for (approximate) classical solutions of the lattice field equations and find in particular the dissociated calorons recently discussed by van Baal and collaborators.

  11. Decadal trends in Red Sea maximum surface temperature

    KAUST Repository

    Chaidez, Veronica

    2017-08-09

    Ocean warming is a major consequence of climate change, with the surface of the ocean having warmed by 0.11 °C decade-1 over the last 50 years and is estimated to continue to warm by an additional 0.6 - 2.0 °C before the end of the century1. However, there is considerable variability in the rates experienced by different ocean regions, so understanding regional trends is important to inform on possible stresses for marine organisms, particularly in warm seas where organisms may be already operating in the high end of their thermal tolerance. Although the Red Sea is one of the warmest ecosystems on earth, its historical warming trends and thermal evolution remain largely understudied. We characterized the Red Sea\\'s thermal regimes at the basin scale, with a focus on the spatial distribution and changes over time of sea surface temperature maxima, using remotely sensed sea surface temperature data from 1982 - 2015. The overall rate of warming for the Red Sea is 0.17 ± 0.07 °C decade-1, while the northern Red Sea is warming between 0.40 and 0.45 °C decade-1, all exceeding the global rate. Our findings show that the Red Sea is fast warming, which may in the future challenge its organisms and communities.

  12. The Benefit of Surface Uniformity for Encoding Boundary Features in Visual Working Memory

    Science.gov (United States)

    Kim, Sung-Ho; Kim, Jung-Oh

    2011-01-01

    Using a change detection paradigm, the present study examined an object-based encoding benefit in visual working memory (VWM) for two boundary features (two orientations in Experiments 1-2 and two shapes in Experiments 3-4) assigned to a single object. Participants remembered more boundary features when they were conjoined into a single object of…

  13. Temperature-mediated transition from Dyakonov-Tamm surface waves to surface-plasmon-polariton waves

    Science.gov (United States)

    Chiadini, Francesco; Fiumara, Vincenzo; Mackay, Tom G.; Scaglione, Antonio; Lakhtakia, Akhlesh

    2017-08-01

    The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.

  14. Gaia FGK Benchmark Stars: Effective temperatures and surface gravities

    CERN Document Server

    Heiter, U; Gustafsson, B; Korn, A J; Soubiran, C; Thévenin, F

    2015-01-01

    Large Galactic stellar surveys and new generations of stellar atmosphere models and spectral line formation computations need to be subjected to careful calibration and validation and to benchmark tests. We focus on cool stars and aim at establishing a sample of 34 Gaia FGK Benchmark Stars with a range of different metallicities. The goal was to determine the effective temperature and the surface gravity independently from spectroscopy and atmospheric models as far as possible. Fundamental determinations of Teff and logg were obtained in a systematic way from a compilation of angular diameter measurements and bolometric fluxes, and from a homogeneous mass determination based on stellar evolution models. The derived parameters were compared to recent spectroscopic and photometric determinations and to gravity estimates based on seismic data. Most of the adopted diameter measurements have formal uncertainties around 1%, which translate into uncertainties in effective temperature of 0.5%. The measurements of bol...

  15. Global Surface Temperature Response Explained by Multibox Energy Balance Models

    Science.gov (United States)

    Fredriksen, H. B.; Rypdal, M.

    2016-12-01

    We formulate a multibox energy balance model, from which global temperature evolution can be described by convolving a linear response function and a forcing record. We estimate parameters in the response function from instrumental data and historic forcing, such that our model can produce a response to both deterministic forcing and stochastic weather forcing consistent with observations. Furthermore, if we make separate boxes for upper ocean layer and atmosphere over land, we can also make separate response functions for global land and sea surface temperature. By describing internal variability as a linear response to white noise, we demonstrate that the power-law form of the observed temperature spectra can be described by linear dynamics, contrary to a common belief that these power-law spectra must arise from nonlinear processes. In our multibox model, the power-law form can arise due to the multiple response times. While one of our main points is that the climate system responds over a wide range of time scales, we cannot find one set of time scales that can be preferred compared to other choices. Hence we think the temperature response can best be characterized as something that is scale-free, but still possible to approximate by a set of well separated time scales.

  16. Viscous Dissipation Effects on the Motion of Casson Fluid over an Upper Horizontal Thermally Stratified Melting Surface of a Paraboloid of Revolution: Boundary Layer Analysis

    Directory of Open Access Journals (Sweden)

    T. M. Ajayi

    2017-01-01

    Full Text Available The problem of a non-Newtonian fluid flow past an upper surface of an object that is neither a perfect horizontal/vertical nor inclined/cone in which dissipation of energy is associated with temperature-dependent plastic dynamic viscosity is considered. An attempt has been made to focus on the case of two-dimensional Casson fluid flow over a horizontal melting surface embedded in a thermally stratified medium. Since the viscosity of the non-Newtonian fluid tends to take energy from the motion (kinetic energy and transform it into internal energy, the viscous dissipation term is accommodated in the energy equation. Due to the existence of internal space-dependent heat source; plastic dynamic viscosity and thermal conductivity of the non-Newtonian fluid are assumed to vary linearly with temperature. Based on the boundary layer assumptions, suitable similarity variables are applied to nondimensionalized, parameterized and reduce the governing partial differential equations into a coupled ordinary differential equations. These equations along with the boundary conditions are solved numerically using the shooting method together with the Runge-Kutta technique. The effects of pertinent parameters are established. A significant increases in Rex1/2Cfx is guaranteed with St when magnitude of β is large. Rex1/2Cfx decreases with Ec and m.

  17. Geostatistical Solutions for Downscaling Remotely Sensed Land Surface Temperature

    Science.gov (United States)

    Wang, Q.; Rodriguez-Galiano, V.; Atkinson, P. M.

    2017-09-01

    Remotely sensed land surface temperature (LST) downscaling is an important issue in remote sensing. Geostatistical methods have shown their applicability in downscaling multi/hyperspectral images. In this paper, four geostatistical solutions, including regression kriging (RK), downscaling cokriging (DSCK), kriging with external drift (KED) and area-to-point regression kriging (ATPRK), are applied for downscaling remotely sensed LST. Their differences are analyzed theoretically and the performances are compared experimentally using a Landsat 7 ETM+ dataset. They are also compared to the classical TsHARP method.

  18. Long-term changes of South China Sea surface temperatures in winter and summer

    Science.gov (United States)

    Park, Young-Gyu; Choi, Ara

    2017-07-01

    Utilizing available atmospheric and oceanographic reanalysis data sets, the long-term trend in South China Sea (SCS) sea surface temperature (SST) between 1950 and 2008 and the governing processes are investigated. Both winter and summer SST increased by comparable amounts, but the warming patterns and the governing processes were different. Strong warming in winter occurred in a deep central area, and during summer in the southern region. In winter the net heat flux into the sea increased, contributing to the warming. The spatial pattern of the heat flux, however, was different from that of the warming. Heat flux increased over the coastal area where warming was weaker, but decreased over the deeper area where warming was stronger. The northeasterly monsoon wind weakened lowering the shoreward Ekman transport and the sea surface height gradient. The cyclonic gyre which transports cold northern water to the south weakened, thereby warming the ocean. The effect was manifested more strongly along the southward western boundary current inducing warming in the deep central part. In summer however, the net surface heat flux decreased and could not contribute to the warming. Over the southern part of the SCS, the weakening of the southwesterly summer monsoon reduced southeastward Ekman transport, which is parallel to the mean SST gradient. Southeastward cold advection due to Ekman transport was reduced, thereby warming the surface near the southeastern boundary of the SCS. Upwelling southeast of Vietnam was also weakened, raising the SST east of Vietnam contributing to the southern summer warming secondarily. The weakening of the winds in each season was the ultimate cause of the warming, but the responses of the ocean that lead to the warming were different in winter and summer.

  19. Effect of surface nanostructure on temperature programmed reaction spectroscopy

    Science.gov (United States)

    Rieger, Michael; Rogal, Jutta; Reuter, Karsten

    2008-03-01

    Using the catalytic CO oxidation at RuO2(110) as a showcase, we employ first-principles kinetic Monte Carlo simulations to illustrate the intricate effects on temperature programmed reaction (TPR) spectroscopy data brought about by the mere correlations between the locations of the active sites at a nanostructured surface. Even in the absence of lateral interactions, this nanostructure alone can cause inhomogeneities that cannot be grasped by prevalent mean-field data analysis procedures, which thus lead to wrong conclusions on the reactivity of the different surface species. The RuO2(110) surface studied here exhibits only two prominent active sites, arranged in simple alternating rows. Yet, the mere neglection of this still quite trivial nanostructure leads mean-field TPR data analysis [1] to extract kinetic parameters that are in error by several orders of magnitude and that do not even reflect the relative reactivity of the different surface species correctly [2].[1] S. Wendt, M. Knapp, and H. Over, JACS 126, 1537 (2004).[2] M. Rieger, J. Rogal, and K. Reuter, Phys. Rev. Lett (in press).

  20. Compatibility of lithium plasma-facing surfaces with high edge temperatures in the Lithium Tokamak Experiment (LTX)

    Science.gov (United States)

    Majeski, Dick

    2016-10-01

    High edge electron temperatures (200 eV or greater) have been measured at the wall-limited plasma boundary in the Lithium Tokamak eXperiment (LTX). High edge temperatures, with flat electron temperature profiles, are a long-predicted consequence of low recycling boundary conditions. The temperature profile in LTX, measured by Thomson scattering, varies by as little as 10% from the plasma axis to the boundary, determined by the lithium-coated high field-side wall. The hydrogen plasma density in the outer scrape-off layer is very low, 2-3 x 1017 m-3 , consistent with a low recycling metallic lithium boundary. The plasma surface interaction in LTX is characterized by a low flux of high energy protons to the lithium PFC, with an estimated Debye sheath potential approaching 1 kV. Plasma-material interactions in LTX are consequently in a novel regime, where the impacting proton energy exceeds the peak in the sputtering yield for the lithium wall. In this regime, further increases in the edge temperature will decrease, rather than increase, the sputtering yield. Despite the high edge temperature, the core impurity content is low. Zeff is 1.2 - 1.5, with a very modest contribution (Gas puffing is used to increase the plasma density. After gas injection stops, the discharge density is allowed to drop, and the edge is pumped by the low recycling lithium wall. An upgrade to LTX which includes a 35A, 20 kV neutral beam injector to provide core fueling to maintain constant density, as well as auxiliary heating, is underway. Two beam systems have been loaned to LTX by Tri Alpha Energy. Additional results from LTX, as well as progress on the upgrade - LTX- β - will be discussed. Work supported by US DOE contracts DE-AC02-09CH11466 and DE-AC05-00OR22725.