Gain curves and hydrodynamic modeling for shock ignition
International Nuclear Information System (INIS)
Lafon, M.; Ribeyre, X.; Schurtz, G.
2010-01-01
Ignition of a precompressed thermonuclear fuel by means of a converging shock is now considered as a credible scheme to obtain high gains for inertial fusion energy. This work aims at modeling the successive stages of the fuel time history, from compression to final thermonuclear combustion, in order to provide the gain curves of shock ignition (SI). The leading physical mechanism at work in SI is pressure amplification, at first by spherical convergence, and by collision with the shock reflected at center during the stagnation process. These two effects are analyzed, and ignition conditions are provided as functions of the shock pressure and implosion velocity. Ignition conditions are obtained from a non-isobaric fuel assembly, for which we present a gain model. The corresponding gain curves exhibit a significantly lower ignition threshold and higher target gains than conventional central ignition.
Hydrodynamic modelling of the shock ignition scheme for inertial confinement fusion
International Nuclear Information System (INIS)
Vallet, Alexandra
2014-01-01
The shock ignition concept in inertial confinement fusion uses an intense power spike at the end of an assembly laser pulse. The key features of shock ignition are the generation of a high ablation pressure, the shock pressure amplification by at least a factor of a hundred in the cold fuel shell and the shock coupling to the hot-spot. In this thesis, new semi-analytical hydrodynamic models are developed to describe the ignitor shock from its generation up to the moment of fuel ignition. A model is developed to describe a spherical converging shock wave in a pre-heated hot spot. The self-similar solution developed by Guderley is perturbed over the shock Mach number Ms ≥≥1. The first order correction accounts for the effects of the shock strength. An analytical ignition criterion is defined in terms of the shock strength and the hot-spot areal density. The ignition threshold is higher when the initial Mach number of the shock is lower. A minimal shock pressure of 20 Gbar is needed when it enters the hot-spot. The shock dynamics in the imploding shell is then analyzed. The shock is propagating into a non inertial medium with a high radial pressure gradient and an overall pressure increase with time. The collision with a returning shock coming from the assembly phase enhances further the ignitor shock pressure. The analytical theory allows to describe the shock pressure and strength evolution in a typical shock ignition implosion. It is demonstrated that, in the case of the HiPER target design, a generation shock pressure near the ablation zone on the order of 300-400 Mbar is needed. An analysis of experiments on the strong shock generation performed on the OMEGA laser facility is presented. It is shown that a shock pressure close to 300 Mbar near the ablation zone has been reached with an absorbed laser intensity up to 2 * 10 15 W:cm -2 and a laser wavelength of 351 nm. This value is two times higher than the one expected from collisional laser absorption only
Hydrodynamic modeling and simulations of shock ignition thresholds
Directory of Open Access Journals (Sweden)
Lafon M.
2013-11-01
Full Text Available The Shock Ignition (SI scheme [1] offers to reduce the laser requirements by relaxing the implosion phase to sub-ignition velocities and later adding an intense laser spike. Depending on laser energy, target characteristics and implosion velocity, high gains are expected [2,3]. Relevant intensities for scaled targets imploded in the velocity range from 150 to 400 km/s are defined at ignition thresholds. A range of moderate implosion velocities is specified to match safe implosions. These conditions for target design are then inferred for relevant NIF and LMJ shock-ignited targets.
Modeling of laser induced air plasma and shock wave dynamics using 2D-hydrodynamic simulations
Paturi, Prem Kiran; S, Sai Shiva; Chelikani, Leela; Ikkurthi, Venkata Ramana; C. D., Sijoy; Chaturvedi, Shashank; Acrhem, University Of Hyderabad Team; Computational Analysis Division, Bhabha Atomic Research Centre, Visakhapatnam Team
2017-06-01
The laser induced air plasma dynamics and the SW evolution modeled using the two dimensional hydrodynamic code by considering two different EOS: ideal gas EOS with charge state effects taken into consideration and Chemical Equilibrium applications (CEA) EOS considering the chemical kinetics of different species will be presented. The inverse bremsstrahlung absorption process due to electron-ion and electron-neutrals is considered for the laser-air interaction process for both the models. The numerical results obtained with the two models were compared with that of the experimental observations over the time scales of 200 - 4000 ns at an input laser intensity of 2.3 ×1010 W/cm2. The comparison shows that the plasma and shock dynamics differ significantly for two EOS considered. With the ideas gas EOS the asymmetric expansion and the subsequent plasma dynamics have been well reproduced as observed in the experiments, whereas with the CEA model these processes were not reproduced due to the laser energy absorption occurring mostly at the focal volume. ACRHEM team thank DRDO, India for funding.
Universal hydrodynamic flow in holographic planar shock collisions
Energy Technology Data Exchange (ETDEWEB)
Chesler, Paul M. [Department of Physics, Harvard University,Cambridge MA 02138 (United States); Kilbertus, Niki [Institut für Theoretische Physik, Universität Regensburg,D-93040 Regensburg (Germany); Schee, Wilke van der [Center for Theoretical Physics, MIT,Cambridge MA 02139 (United States)
2015-11-20
We study the collision of planar shock waves in AdS{sub 5} as a function of shock profile. In the dual field theory the shock waves describe planar sheets of energy whose collision results in the formation of a plasma which behaves hydrodynamically at late times. We find that the post-collision stress tensor near the light cone exhibits transient non-universal behavior which depends on both the shock width and the precise functional form of the shock profile. However, over a large range of shock widths, including those which yield qualitative different behavior near the future light cone, and for different shock profiles, we find universal behavior in the subsequent hydrodynamic evolution. Additionally, we compute the rapidity distribution of produced particles and find it to be well described by a Gaussian.
Modeling of laser-driven hydrodynamics experiments
di Stefano, Carlos; Doss, Forrest; Rasmus, Alex; Flippo, Kirk; Desjardins, Tiffany; Merritt, Elizabeth; Kline, John; Hager, Jon; Bradley, Paul
2017-10-01
Correct interpretation of hydrodynamics experiments driven by a laser-produced shock depends strongly on an understanding of the time-dependent effect of the irradiation conditions on the flow. In this talk, we discuss the modeling of such experiments using the RAGE radiation-hydrodynamics code. The focus is an instability experiment consisting of a period of relatively-steady shock conditions in which the Richtmyer-Meshkov process dominates, followed by a period of decaying flow conditions, in which the dominant growth process changes to Rayleigh-Taylor instability. The use of a laser model is essential for capturing the transition. also University of Michigan.
Modeling hydrodynamic cavitation
Energy Technology Data Exchange (ETDEWEB)
Kumar, P.S.; Pandit, A.B. [Mumbai Univ. (India). Chemical Engineering Div.
1999-12-01
Cavitation as a source and method of energy input for chemical processing is increasingly studied due to its ability to generate localized high temperatures and pressures under nearly ambient conditions. Compared to cavitation generated by ultrasound, hydrodynamic cavitation has been proved to be a very energy-efficient alternative. A simple and unified model has been developed to study the cavitation phenomena in hydraulic systems with emphasis on the venturi tube and high-speed homogenizer. The model has been found to be satisfactory in explaining the effect of operating variables and equipment geometry on two different modes of cavitation generation qualitatively and in some cases quantitatively. (orig.)
Hydrodynamic simulations of microjetting from shock-loaded grooves
Roland, C.; de Rességuier, T.; Sollier, A.; Lescoute, E.; Soulard, L.; Loison, D.
2017-01-01
The interaction of a shock wave with a free surface which has geometrical defects, such as cavities or grooves, may lead to the ejection of micrometric debris at velocities of km/s. This process can be involved in many applications, like pyrotechnics or industrial safety. Recent laser shock experiments reported elsewhere in this conference have provided some insight into jet formation as well as jet tip velocities for various groove angles and shock pressures. Here, we present hydrodynamic simulations of these experiments, in both 2D and 3D geometries, using both finite element method and smoothed particle hydrodynamics. Numerical results are compared to several theoretical predictions including the Richtmyer-Meshkov instabilities. The role of the elastic-plastic behavior on jet formation is illustrated. Finally, the possibility to simulate the late stage of jet expansion and fragmentation is explored, to evaluate the mass distribution of the ejecta and their ballistic properties, still essentially unknown in the experiments.
Rippled shock front solutions for testing hydrodynamic stability simulations
International Nuclear Information System (INIS)
Munro, D.H.
1989-01-01
The response of a shock front to arbitrary small perturbations can be calculated analytically. Such rippled shock front solutions are useful for determining the accuracy of hydrodynamic simulation codes such as LASNEX [Comments Plasma Phys. Controlled Fusion 2, 51 (1977)], which are used to compute perturbation growth in inertial fusion targets. The LASNEX fractional errors are of order κ 2 L 2 , where κ is the transverse wavenumber of the perturbation, and L is the largest zone dimension. Numerical errors are about 25% for a calculation using 26 zones per transverse wavelength
Shock-hydrodynamics experiments on the Nova laser
International Nuclear Information System (INIS)
Miller, P.; Peyser, T.; Stry, P.; Budil, K.; Wojtowicz, D.; Burke, E.
1995-08-01
We have conducted shock-induced hydrodynamics experiments using the Nova laser at Lawrence Livermore National Laboratory. The laser provides a high-enthalpy source by depositing its energy (about 22 kJ) in a small gold cavity called a Hohlraum. The Hohlraum serves as a driver section, launching very strong (M ∼ 20) shocks into millimeter-scale cylindrical ''shock tubes.'' The flow is imaged radiographically by an electronic framing camera, using a laser-generated x-ray source. Several topics have been addressed with this configuration, including shock-induced mixing at density interfaces (seeded with a variety of perturbations); the development of high-speed, shaped-charge-like jets; the effects of geometry on the planarity of the generated shocks; and shock-shock interactions which develop in the flows. This paper describes the general configuration of our experiments, presents an overview of the high-speed jet work, discusses some of our findings, and compares our results with computer simulations
Lotic Water Hydrodynamic Model
Energy Technology Data Exchange (ETDEWEB)
Judi, David Ryan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tasseff, Byron Alexander [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-01-23
Water-related natural disasters, for example, floods and droughts, are among the most frequent and costly natural hazards, both socially and economically. Many of these floods are a result of excess rainfall collecting in streams and rivers, and subsequently overtopping banks and flowing overland into urban environments. Floods can cause physical damage to critical infrastructure and present health risks through the spread of waterborne diseases. Los Alamos National Laboratory (LANL) has developed Lotic, a state-of-the-art surface water hydrodynamic model, to simulate propagation of flood waves originating from a variety of events. Lotic is a two-dimensional (2D) flood model that has been used primarily for simulations in which overland water flows are characterized by movement in two dimensions, such as flood waves expected from rainfall-runoff events, storm surge, and tsunamis. In 2013, LANL developers enhanced Lotic through several development efforts. These developments included enhancements to the 2D simulation engine, including numerical formulation, computational efficiency developments, and visualization. Stakeholders can use simulation results to estimate infrastructure damage and cascading consequences within other sets of infrastructure, as well as to inform the development of flood mitigation strategies.
Directory of Open Access Journals (Sweden)
Sezar Gülbaz
2015-01-01
Full Text Available The land development and increase in urbanization in a watershed affect water quantityand water quality. On one hand, urbanization provokes the adjustment of geomorphicstructure of the streams, ultimately raises peak flow rate which causes flood; on theother hand, it diminishes water quality which results in an increase in Total SuspendedSolid (TSS. Consequently, sediment accumulation in downstream of urban areas isobserved which is not preferred for longer life of dams. In order to overcome thesediment accumulation problem in dams, the amount of TSS in streams and inwatersheds should be taken under control. Low Impact Development (LID is a BestManagement Practice (BMP which may be used for this purpose. It is a land planningand engineering design method which is applied in managing storm water runoff inorder to reduce flooding as well as simultaneously improve water quality. LID includestechniques to predict suspended solid loads in surface runoff generated over imperviousurban surfaces. In this study, the impact of LID-BMPs on surface runoff and TSS isinvestigated by employing a calibrated hydrodynamic model for Sazlidere Watershedwhich is located in Istanbul, Turkey. For this purpose, a calibrated hydrodynamicmodel was developed by using Environmental Protection Agency Storm WaterManagement Model (EPA SWMM. For model calibration and validation, we set up arain gauge and a flow meter into the field and obtain rainfall and flow rate data. Andthen, we select several LID types such as retention basins, vegetative swales andpermeable pavement and we obtain their influence on peak flow rate and pollutantbuildup and washoff for TSS. Consequently, we observe the possible effects ofLID on surface runoff and TSS in Sazlidere Watershed.
On the Generation of Hydrodynamic Shocks by Mixed Beams and Occurrence of Sunquakes in Flares
Zharkova, Valentina; Zharkov, Sergei
2015-11-01
Observations of solar flares with sunquakes by space- and ground-based instruments reveal essentially different dynamics of seismic events in different flares. Some sunquakes are found to be closely associated with the locations of hard X-ray (HXR) and white-light (WL) emission, while others are located outside either of them. In this article we investigate possible sources causing a seismic response in a form of hydrodynamic shocks produced by the injection of mixed (electron plus proton) beams, discuss the velocities of these shocks, and the depths where they deposit the bulk of their energy and momentum. The simulation of hydrodynamic shocks in flaring atmospheres induced by electron-rich and proton-rich beams reveals that the linear depth of the shock termination is shifted beneath the level of the quiet solar photosphere on a distance from 200 to 5000 km. The parameters of these atmospheric hydrodynamic shocks are used as initial condition for another hydrodynamic model developed for acoustic-wave propagation in the solar interior (Zharkov, Mon. Not. Roy. Astron. Soc. 431, 3414, 2013). The model reveals that the depth of energy and momentum deposition by the atmospheric shocks strongly affects the propagation velocity of the acoustic-wave packet in the interior. The locations of the first bounces from the photosphere of acoustic waves generated in the vicinity of a flare are seen as ripples on the solar surface, or sunquakes. Mixed proton-dominated beams are found to produce a strong supersonic shock at depths 200 - 300 km under the level of the quiet-Sun photosphere and in this way produce well-observable acoustic waves, while electron-dominated beams create a slightly supersonic shock propagating down to 5000 km under the photosphere. This shock can only generate acoustic waves at the top layers beneath the photosphere since the shock velocity very quickly drops below the local sound speed. The distance Δ of the first bounce of the generated acoustic waves
Recent development of hydrodynamic modeling
Hirano, Tetsufumi
2014-09-01
In this talk, I give an overview of recent development in hydrodynamic modeling of high-energy nuclear collisions. First, I briefly discuss about current situation of hydrodynamic modeling by showing results from the integrated dynamical approach in which Monte-Carlo calculation of initial conditions, quark-gluon fluid dynamics and hadronic cascading are combined. In particular, I focus on rescattering effects of strange hadrons on final observables. Next I highlight three topics in recent development in hydrodynamic modeling. These include (1) medium response to jet propagation in di-jet asymmetric events, (2) causal hydrodynamic fluctuation and its application to Bjorken expansion and (3) chiral magnetic wave from anomalous hydrodynamic simulations. (1) Recent CMS data suggest the existence of QGP response to propagation of jets. To investigate this phenomenon, we solve hydrodynamic equations with source term which exhibits deposition of energy and momentum from jets. We find a large number of low momentum particles are emitted at large angle from jet axis. This gives a novel interpretation of the CMS data. (2) It has been claimed that a matter created even in p-p/p-A collisions may behave like a fluid. However, fluctuation effects would be important in such a small system. We formulate relativistic fluctuating hydrodynamics and apply it to Bjorken expansion. We found the final multiplicity fluctuates around the mean value even if initial condition is fixed. This effect is relatively important in peripheral A-A collisions and p-p/p-A collisions. (3) Anomalous transport of the quark-gluon fluid is predicted when extremely high magnetic field is applied. We investigate this possibility by solving anomalous hydrodynamic equations. We found the difference of the elliptic flow parameter between positive and negative particles appears due to the chiral magnetic wave. Finally, I provide some personal perspective of hydrodynamic modeling of high energy nuclear collisions
Hydrodynamic modeling and explosive compaction of ceramics
International Nuclear Information System (INIS)
Hoenig, C.; Holt, A.; Finger, M.; Kuhl, W.
1977-01-01
High-density ceramics with high-strength microstructure were achieved by explosive compaction. Well-characterized Al 2 O 3 , AlN, and boron powders were explosively compacted in both cylindrical and flat plate geometries. In cylindrical geometries compacted densities between 91 and 98 percent of theoretical were achieved. Microhardness measurements indicated that the strength and integrity of the microstructure were comparable to conventionally fabricated ceramics, even though all samples with densities greater than 90 percent theoretical contained macrocracks. Fractured surfaces evaluated by SEM showed evidence of boundary melting. Equation of state data for porous Al 2 O 3 were used to calculate the irreversible work done on the sample as a function of pressure. This was expressed as a percentage of the total sample which could be melted. Calculations show that very little melting can be expected in samples shocked to less than 3 GPa. Significant melting and grain boundary fusion can be expected in samples shocked to pressures greater than 8 GPa. Hydrodynamic modeling of right cylinder compaction with detonation at one end was attempted by using a two-dimensional computer code. The complications of this analysis led to experiments using plane shock waves. Flat-plate compaction assemblies were designed and analyzed by 2-D hydrodynamic codes. The use of porous shock attenuators was evaluated. Experiments were performed on aluminum oxide powders in plane wave geometry. Microstructure evaluations were made as a function of location in the flat plate samples. 11 figures, 1 table
Simple model for decay of laser generated shock waves
International Nuclear Information System (INIS)
Trainor, R.J.
1980-01-01
A simple model is derived to calculate the hydrodynamic decay of laser-generated shock waves. Comparison with detailed hydrocode simulations shows good agreement between calculated time evolution of shock pressure, position, and instantaneous pressure profile. Reliability of the model decreases in regions of the target where superthermal-electron preheat effects become comparable to shock effects
Mixing-model Sensitivity to Initial Conditions in Hydrodynamic Predictions
Bigelow, Josiah; Silva, Humberto; Truman, C. Randall; Vorobieff, Peter
2017-11-01
Amagat and Dalton mixing-models were studied to compare their thermodynamic prediction of shock states. Numerical simulations with the Sandia National Laboratories shock hydrodynamic code CTH modeled University of New Mexico (UNM) shock tube laboratory experiments shocking a 1:1 molar mixture of helium (He) and sulfur hexafluoride (SF6) . Five input parameters were varied for sensitivity analysis: driver section pressure, driver section density, test section pressure, test section density, and mixture ratio (mole fraction). We show via incremental Latin hypercube sampling (LHS) analysis that significant differences exist between Amagat and Dalton mixing-model predictions. The differences observed in predicted shock speeds, temperatures, and pressures grow more pronounced with higher shock speeds. Supported by NNSA Grant DE-0002913.
Energy Technology Data Exchange (ETDEWEB)
Suzuki, Akihiro; Maeda, Keiichi [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 (Japan); Shigeyama, Toshikazu [Research Center for the Early Universe, School of Science, University of Tokyo, Bunkyo-ku, Tokyo, 113-0033 (Japan)
2016-07-10
A two-dimensional special relativistic radiation-hydrodynamics code is developed and applied to numerical simulations of supernova shock breakout in bipolar explosions of a blue supergiant. Our calculations successfully simulate the dynamical evolution of a blast wave in the star and its emergence from the surface. Results of the model with spherical energy deposition show a good agreement with previous simulations. Furthermore, we calculate several models with bipolar energy deposition and compare their results with the spherically symmetric model. The bolometric light curves of the shock breakout emission are calculated by a ray-tracing method. Our radiation-hydrodynamic models indicate that the early part of the shock breakout emission can be used to probe the geometry of the blast wave produced as a result of the gravitational collapse of the iron core.
Hydrodynamical model with massless constituents
International Nuclear Information System (INIS)
Chiu, C.B.; Wang, K.H.
1974-01-01
Within the constituent hydrodynamical model, it is shown that the total number of constituents is conserved, if these constituents are massless and satisfy the Fermi-Dirac distribution. A simple scheme for the transition from the constituent-phase to the hadron-phase is suggested, and the hadron inclusive momentum spectra are presented for this case. This phase transition scheme predicts the average transverse momentum of meson resonances which is compatible with the data. (U.S.)
Two-temperature hydrodynamics of laser-generated ultrashort shock waves in elasto-plastic solids
International Nuclear Information System (INIS)
Ilnitsky, Denis K; Migdal, Kirill P; Khokhlov, Viktor A; Inogamov, Nail A; Petrov, Yurii V; Anisimov, Sergey I; Zhakhovsky, Vasily V; Khishchenko, Konstantin V
2014-01-01
Shock-wave generation by ultrashort laser pulses opens new doors for study of hidden processes in materials happened at an atomic-scale spatiotemporal scales. The poorly explored mechanism of shock generation is started from a short-living two-temperature (2T) state of solid in a thin surface layer where laser energy is deposited. Such 2T state represents a highly non-equilibrium warm dense matter having cold ions and hot electrons with temperatures of 1-2 orders of magnitude higher than the melting point. Here for the first time we present results obtained by our new hybrid hydrodynamics code combining detailed description of 2T states with a model of elasticity together with a wide-range equation of state of solid. New hydro-code has higher accuracy in the 2T stage than molecular dynamics method, because it includes electron related phenomena including thermal conduction, electron-ion collisions and energy transfer, and electron pressure. From the other hand the new code significantly improves our previous version of 2T hydrodynamics model, because now it is capable of reproducing the elastic compression waves, which may have an imprint of supersonic melting like as in MD simulations. With help of the new code we have solved a difficult problem of thermal and dynamic coupling of a molten layer with an uniaxially compressed elastic solid. This approach allows us to describe the recent femtosecond laser experiments.
New equation of state model for hydrodynamic applications
Energy Technology Data Exchange (ETDEWEB)
Young, D.A.; Barbee, T.W. III; Rogers, F.J.
1997-07-01
Two new theoretical methods for computing the equation of state of hot, dense matter are discussed.The ab initio phonon theory gives a first-principles calculation of lattice frequencies, which can be used to compare theory and experiment for isothermal and shock compression of solids. The ACTEX dense plasma theory has been improved to allow it to be compared directly with ultrahigh pressure shock data on low-Z materials. The comparisons with experiment are good, suggesting that these models will be useful in generating global EOS tables for hydrodynamic simulations.
New equation of state models for hydrodynamic applications
Young, David A.; Barbee, Troy W.; Rogers, Forrest J.
1998-07-01
Two new theoretical methods for computing the equation of state of hot, dense matter are discussed. The ab initio phonon theory gives a first-principles calculation of lattice frequencies, which can be used to compare theory and experiment for isothermal and shock compression of solids. The ACTEX dense plasma theory has been improved to allow it to be compared directly with ultrahigh pressure shock data on low-Z materials. The comparisons with experiment are good, suggesting that these models will be useful in generating global EOS tables for hydrodynamic simulations.
New equation of state models for hydrodynamic applications
Energy Technology Data Exchange (ETDEWEB)
Young, D.A.; Barbee, T.W. III; Rogers, F.J. [Physics Department, Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
1998-07-01
Two new theoretical methods for computing the equation of state of hot, dense matter are discussed. The ab initio phonon theory gives a first-principles calculation of lattice frequencies, which can be used to compare theory and experiment for isothermal and shock compression of solids. The ACTEX dense plasma theory has been improved to allow it to be compared directly with ultrahigh pressure shock data on low-Z materials. The comparisons with experiment are good, suggesting that these models will be useful in generating global EOS tables for hydrodynamic simulations. {copyright} {ital 1998 American Institute of Physics.}
Two-fluid hydrodynamic model for semiconductors
DEFF Research Database (Denmark)
Maack, Johan Rosenkrantz; Mortensen, N. Asger; Wubs, Martijn
2018-01-01
The hydrodynamic Drude model (HDM) has been successful in describing the optical properties of metallic nanostructures, but for semiconductors where several different kinds of charge carriers are present an extended theory is required. We present a two-fluid hydrodynamic model for semiconductors...
Dorofeenko, Victor; Lee, Gabriel; Salyer, Kevin; Strobel, Johannes
2016-01-01
Within the context of a financial accelerator model, we model time-varying uncertainty (i.e. risk shocks) through the use of a mixture Normal model with time variation in the weights applied to the underlying distributions characterizing entrepreneur productivity. Specifically, we model capital producers (i.e. the entrepreneurs) as either low-risk (relatively small second moment for productivity) and high-risk (relatively large second moment for productivity) and the fraction of both types is...
Soliton shock wave fronts and self-similar discontinuities in dispersion hydrodynamics
International Nuclear Information System (INIS)
Gurevich, A.V.; Meshcherkin, A.P.
1987-01-01
Nonlinear flows in nondissipative dispersion hydrodynamics are examined. It is demonstrated that in order to describe such flows it is necessary to incorporate a new concept: a special discontinuity called a ''self-similar'' discontinuity consisting of a nondissipative shock wave and a powerful slow wave discontinuity in regular hydrodynamics. The ''self similar discontinuity'' expands linearly over time. It is demonstrated that this concept may be introduced in a solution to Euler equations. The boundary conditions of the ''self similar discontinuity'' that allow closure of Euler equations for dispersion hydrodynamics are formulated, i.e., those that replace the shock adiabatic curve of standard dissipative hydrodynamics. The structure of the soliton front and of the trailing edge of the shock wave is investigated. A classification and complete solution are given to the problem of the decay of random initial discontinuities in the hydrodynamics of highly nonisothermic plasma. A solution is derived to the problem of the decay of initial discontinuities in the hydrodynamics of magnetized plasma. It is demonstrated that in this plasma, a feature of current density arises at the point of soliton inversion
Dileptons from transport and hydrodynamical models
International Nuclear Information System (INIS)
Huovinen, P.; Koch, V.
2000-01-01
Transport and hydrodynamical models used to describe the expansion stage of a heavy-ion collision at the CERN SPS give different dilepton spectrum even if they are tuned to reproduce the observed hadron spectra. To understand the origin of this difference we compare the dilepton emission from transport and hydrodynamical models using similar initial states in both models. We find that the requirement of pion number conservation in a hydrodynamical model does not change the dilepton emission. Also the mass distribution from the transport model indicates faster cooling and longer lifetime of the fireball
Ma, K. H.; Lefevre, H. J.; Belancourt, P. X.; MacDonald, M. J.; Doeppner, T.; Keiter, P. A.; Kuranz, C. C.; Johnsen, E.
2017-10-01
Recent experiments at the National Ignition Facility studied the effect of radiation on shock-driven hydrodynamic instability growth. X-ray radiography images from these experiments indicate that perturbation growth is lower in highly radiative shocks compared to shocks with negligible radiation flux. The reduction in instability growth is attributed to ablation from higher temperatures in the foam for highly radiative shocks. The proposed design implements the X-ray Thomson Scattering (XRTS) technique in the radiative shock tube platform to measure electron temperatures and densities in the shocked foam. We model these experiments with CRASH, an Eulerian radiation hydrodynamics code with block-adaptive mesh refinement, multi-group radiation transport and electron heat conduction. Simulations are presented with SiO2 and carbon foams for both the high temperature, radiative shock and the low-temperature, hydrodynamic shock cases. Calculations from CRASH give estimations for shock speed, electron temperature, effective ionization, and other quantities necessary for designing the XRTS diagnostic measurement. This work is funded by the LLNL under subcontract B614207, and was performed under the auspices of the U.S. DOE by LLNL under Contract No. DE-AC52-07NA27344.
Hydrodynamic Modeling and Its Application in AUC.
Rocco, Mattia; Byron, Olwyn
2015-01-01
The hydrodynamic parameters measured in an AUC experiment, s(20,w) and D(t)(20,w)(0), can be used to gain information on the solution structure of (bio)macromolecules and their assemblies. This entails comparing the measured parameters with those that can be computed from usually "dry" structures by "hydrodynamic modeling." In this chapter, we will first briefly put hydrodynamic modeling in perspective and present the basic physics behind it as implemented in the most commonly used methods. The important "hydration" issue is also touched upon, and the distinction between rigid bodies versus those for which flexibility must be considered in the modeling process is then made. The available hydrodynamic modeling/computation programs, HYDROPRO, BEST, SoMo, AtoB, and Zeno, the latter four all implemented within the US-SOMO suite, are described and their performance evaluated. Finally, some literature examples are presented to illustrate the potential applications of hydrodynamics in the expanding field of multiresolution modeling. © 2015 Elsevier Inc. All rights reserved.
Hydrodynamic modelling of hydrostatic magnesium extrusion
Moodij, Ellen; de Rooij, Matthias B.; Schipper, Dirk J.
2006-01-01
Wilson’s hydrodynamic model of the hydrostatic extrusion process is extended to meet the geometry found on residual billets. The transition from inlet to work zone of the process is not considered sharp as in the model of Wilson but as a rounded edge, modelled by a parabolic function. It is shown
Energy Technology Data Exchange (ETDEWEB)
Doss, F. W., E-mail: fdoss@lanl.gov; Kline, J. L.; Flippo, K. A.; Perry, T. S.; DeVolder, B. G.; Tregillis, I.; Loomis, E. N.; Merritt, E. C.; Murphy, T. J.; Welser-Sherrill, L.; Fincke, J. R. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2015-05-15
An indirectly-driven shock tube experiment fielded on the National Ignition Facility (NIF) was used to create a high-energy-density hydrodynamics platform at unprecedented scale. Scaling up a shear-induced mixing experiment previously fielded at OMEGA, the NIF shear platform drives 130 μm/ns shocks into a CH foam-filled shock tube (∼ 60 mg/cc) with interior dimensions of 1.5 mm diameter and 5 mm length. The pulse-shaping capabilities of the NIF are used to extend the drive for >10 ns, and the large interior tube volumes are used to isolate physics-altering edge effects from the region of interest. The scaling of the experiment to the NIF allows for considerable improvement in maximum driving time of hydrodynamics, in fidelity of physics under examination, and in diagnostic clarity. Details of the experimental platform and post-shot simulations used in the analysis of the platform-qualifying data are presented. Hydrodynamic scaling is used to compare shear data from OMEGA with that from NIF, suggesting a possible change in the dimensionality of the instability at late times from one platform to the other.
Magneto-hydrodynamical model for plasma
Liu, Ruikuan; Yang, Jiayan
2017-10-01
Based on the Newton's second law and the Maxwell equations for the electromagnetic field, we establish a new 3-D incompressible magneto-hydrodynamics model for the motion of plasma under the standard Coulomb gauge. By using the Galerkin method, we prove the existence of a global weak solution for this new 3-D model.
The quantum hydrodynamics of the Sutherland model
International Nuclear Information System (INIS)
Stone, Michael; Gutman, Dmitry
2008-01-01
We show that the form of the chiral condition found by Abanov et al in the quantum hydrodynamics of the Sutherland model arises because there are two distinct inner products with respect to which the chiral Hamiltonian is Hermitian, but only one with respect to which the full, non-chiral, Hamiltonian is Hermitian
Detailed simulation of morphodynamics : 1. Hydrodynamic model
Nabi, M.; De Vriend, H.J.; Mosselman, E.; Sloff, C.J.; Shimizu, Y.
2012-01-01
We present a three-dimensional high-resolution hydrodynamic model for unsteady incompressible flow over an evolving bed topography. This is achieved by using a multilevel Cartesian grid technique that allows the grid to be refined in high-gradient regions and in the vicinity of the river bed. The
Hydrodynamic model research in Waseda group
International Nuclear Information System (INIS)
Muroya, Shin
2010-01-01
Constructing 'High Energy Material Science' had been proposed by Namiki as the guiding principle for the scientists of the high energy physics group lead by himself in Waseda University when the author started to study multiple particle production in 1980s toward the semi-phenomenological model for the quark gluon plasma (QGP). Their strategy was based on three stages to build an intermediate one between the fundamental theory of QCD and the phenomenological model. The quantum theoretical Langevin equation was taken up as the semi-phenomenological model at the intermediate stage and the Landau hydrodynamic model was chosen as the phenomenological model to focus on the 'phase transition' of QGP. A review is given here over the quantum theoretical Langevin equation formalism developed there and followed by the further progress with the 1+1 dimensional viscous fluid model as well as the hydrodynamic model with cylindrical symmetry. The developments of the baryon fluid model and Hanbury-Brown Twiss effect are also reviewed. After 1995 younger generation physicists came to the group to develop those models further. Activities by Hirano, Nonaka and Morita beyond the past generation's hydrodynamic model are picked up briefly. (S. Funahashi)
Hydrodynamic Modeling of Santa Marta's Big Marsh
International Nuclear Information System (INIS)
Saldarriaga, Juan
1991-01-01
The ecological degradation of Santa Marta's Big Marsh and their next areas it has motivated the realization of diagnosis studies and design by several state and private entities. One of the recommended efforts for international advisory it was to develop an ecological model that allowed the handling of the water body and the economic test of alternative of solution to those ecological problems. The first part of a model of this type is in turn a model that simulates the movement of the water inside the marsh, that is to say, a hydrodynamic model. The realization of this was taken charge to the civil engineering department, on the part of Colciencias. This article contains a general explanation of the hydrodynamic pattern that this being developed by a professors group. The ecological causes are described and antecedent, the parts that conform the complex of the Santa Marta big Marsh The marsh modeling is made and it is explained in qualitative form the model type Hydrodynamic used
Simulating sympathetic detonation using the hydrodynamic models and constitutive equations
Energy Technology Data Exchange (ETDEWEB)
Kim, Bo Hoon; Kim, Min Sung; Yoh, Jack J. [Dept. of Mechanical and Aerospace Engineering, Seoul National University, Seoul (Korea, Republic of); Sun, Tae Boo [Hanwha Corporation Defense Rand D Center, Daejeon (Korea, Republic of)
2016-12-15
A Sympathetic detonation (SD) is a detonation of an explosive charge by a nearby explosion. Most of times it is unintended while the impact of blast fragments or strong shock waves from the initiating donor explosive is the cause of SD. We investigate the SD of a cylindrical explosive charge (64 % RDX, 20 % Al, 16 % HTPB) contained in a steel casing. The constitutive relations for high explosive are obtained from a thermo-chemical code that provides the size effect data without the rate stick data typically used for building the rate law and equation of state. A full size SD test of eight pallet-packaged artillery shells is performed that provides the pressure data while the hydrodynamic model with proper constitutive relations for reactive materials and the fragmentation model for steel casing is conducted to replicate the experimental findings. The work presents a novel effort to accurately model and reproduce the sympathetic detonation event with a reduced experimental effort.
Viscosity effect in Landau's hydrodynamical model
International Nuclear Information System (INIS)
Hoang, T.F.; Phua, K.K.; Nanyang Univ., Singapore
1979-01-01
The Bose-Einstein distribution is used to investigate Landau's hydrodynamical model with viscosity. In case the viscosity dependence on the temperature is T 3 , the correction to the multiplicity behaves like I/E and is found to be negligible for the pp data. A discussion is presented on a possibility of reconciling E 1 / 2 and logE dependence of the multiplicity law. (orig.)
Smooth particle hydrodynamic modeling and validation for impact bird substitution
Babu, Arun; Prasad, Ganesh
2018-04-01
Bird strike events incidentally occur and can at times be fatal for air frame structures. Federal Aviation Regulations (FAR) and such other ones mandates aircrafts to be modeled to withstand various levels of bird hit damages. The subject matter of this paper is numerical modeling of a soft body geometry for realistically substituting an actual bird for carrying out simulations of bird hit on target structures. Evolution of such a numerical code to effect an actual bird behavior through impact is much desired for making use of the state of the art computational facilities in simulating bird strike events. Validity, of simulations depicting bird hits, is largely dependent on the correctness of the bird model. In an impact, a set of complex and coupled dynamic interaction exists between the target and the impactor. To simplify this problem, impactor response needs to be decoupled from that of the target. This can be done by assuming and modeling the target as noncompliant. Bird is assumed as fluidic in a impact. Generated stresses in the bird body are significant than its yield stresses. Hydrodynamic theory is most ideal for describing this problem. Impactor literally flows steadily over the target for most part of this problem. The impact starts with an initial shock and falls into a radial release shock regime. Subsequently a steady flow is established in the bird body and this phase continues till the whole length of the bird body is turned around. Initial shock pressure and steady state pressure are ideal variables for comparing and validating the bird model. Spatial discretization of the bird is done using Smooth Particle Hydrodynamic (SPH) approach. This Discrete Element Model (DEM) offers significant advantages over other contemporary approaches. Thermodynamic state variable relations are established using Polynomial Equation of State (EOS). ANSYS AUTODYN is used to perform the explicit dynamic simulation of the impact event. Validation of the shock and steady
Modelling hydrodynamic parameters to predict flow assisted corrosion
International Nuclear Information System (INIS)
Poulson, B.; Greenwell, B.; Chexal, B.; Horowitz, J.
1992-01-01
During the past 15 years, flow assisted corrosion has been a worldwide problem in the power generating industry. The phenomena is complex and depends on environment, material composition, and hydrodynamic factors. Recently, modeling of flow assisted corrosion has become a subject of great importance. A key part of this effort is modeling the hydrodynamic aspects of this issue. This paper examines which hydrodynamic parameter should be used to correlate the occurrence and rate of flow assisted corrosion with physically meaningful parameters, discusses ways of measuring the relevant hydrodynamic parameter, and describes how the hydrodynamic data is incorporated into the predictive model
Hydrodynamic models for slurry bubble column reactors
Energy Technology Data Exchange (ETDEWEB)
Gidaspow, D. [IIT Center, Chicago, IL (United States)
1995-12-31
The objective of this investigation is to convert a {open_quotes}learning gas-solid-liquid{close_quotes} fluidization model into a predictive design model. This model is capable of predicting local gas, liquid and solids hold-ups and the basic flow regimes: the uniform bubbling, the industrially practical churn-turbulent (bubble coalescence) and the slugging regimes. Current reactor models incorrectly assume that the gas and the particle hold-ups (volume fractions) are uniform in the reactor. They must be given in terms of empirical correlations determined under conditions that radically differ from reactor operation. In the proposed hydrodynamic approach these hold-ups are computed from separate phase momentum balances. Furthermore, the kinetic theory approach computes the high slurry viscosities from collisions of the catalyst particles. Thus particle rheology is not an input into the model.
An analytical model of flagellate hydrodynamics
DEFF Research Database (Denmark)
Dölger, Julia; Bohr, Tomas; Andersen, Anders Peter
2017-01-01
solution by Oseen for the low Reynolds number flow due to a point force outside a no-slip sphere. The no-slip sphere represents the cell and the point force a single flagellum. By superposition we are able to model a freely swimming flagellate with several flagella. For biflagellates with left......–right symmetric flagellar arrangements we determine the swimming velocity, and we show that transversal forces due to the periodic movements of the flagella can promote swimming. For a model flagellate with both a longitudinal and a transversal flagellum we determine radius and pitch of the helical swimming......Flagellates are unicellular microswimmers that propel themselves using one or several beating flagella. We consider a hydrodynamic model of flagellates and explore the effect of flagellar arrangement and beat pattern on swimming kinematics and near-cell flow. The model is based on the analytical...
Hydrodynamics of Explosion Experiments and Models
Kedrinskii, Valery K
2005-01-01
Hydronamics of Explosion presents the research results for the problems of underwater explosions and contains a detailed analysis of the structure and the parameters of the wave fields generated by explosions of cord and spiral charges, a description of the formation mechanisms for a wide range of cumulative flows at underwater explosions near the free surface, and the relevant mathematical models. Shock-wave transformation in bubbly liquids, shock-wave amplification due to collision and focusing, and the formation of bubble detonation waves in reactive bubbly liquids are studied in detail. Particular emphasis is placed on the investigation of wave processes in cavitating liquids, which incorporates the concepts of the strength of real liquids containing natural microinhomogeneities, the relaxation of tensile stress, and the cavitation fracture of a liquid as the inversion of its two-phase state under impulsive (explosive) loading. The problems are classed among essentially nonlinear processes that occur unde...
Kasimov, Aslan R.; Faria, Luiz; Rosales, Rodolfo R.
2013-01-01
: steady traveling wave solutions, instability of such solutions, and the onset of chaos. Our model is the first (to our knowledge) to describe chaos in shock waves by a scalar first-order partial differential equation. The chaos arises in the equation
Kasimov, Aslan R.
2013-03-08
We propose the following model equation, ut+1/2(u2−uus)x=f(x,us) that predicts chaotic shock waves, similar to those in detonations in chemically reacting mixtures. The equation is given on the half line, x<0, and the shock is located at x=0 for any t≥0. Here, us(t) is the shock state and the source term f is taken to mimic the chemical energy release in detonations. This equation retains the essential physics needed to reproduce many properties of detonations in gaseous reactive mixtures: steady traveling wave solutions, instability of such solutions, and the onset of chaos. Our model is the first (to our knowledge) to describe chaos in shock waves by a scalar first-order partial differential equation. The chaos arises in the equation thanks to an interplay between the nonlinearity of the inviscid Burgers equation and a novel forcing term that is nonlocal in nature and has deep physical roots in reactive Euler equations.
Modeling the hydrodynamics of Phloem sieve plates
DEFF Research Database (Denmark)
Jensen, Kaare Hartvig; Mullendore, Daniel Leroy; Holbrook, Noel Michele
2012-01-01
Sieve plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play...... understood. We propose a theoretical model for quantifying the effect of sieve plates on the phloem in the plant, thus unifying and improving previous work in the field. Numerical simulations of the flow in real and idealized phloem channels verify our model, and anatomical data from 19 plant species...... a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged. The resistance to the flow of viscous sap in the phloem vascular system is strongly affected by the presence of the sieve plates, but the hydrodynamics of the flow through them remains poorly...
Studying shocks in model astrophysical flows
International Nuclear Information System (INIS)
Chakrabarti, S.K.
1989-01-01
We briefly discuss some properties of the shocks in the existing models for quasi two-dimensional astrophysical flows. All of these models which allow the study of shock analytically have some unphysical characteristics due to inherent assumptions made. We propose a hybrid model for a thin flow which has fewer unpleasant features and is suitable for the study of shocks. (author). 5 refs
An analytical model of flagellate hydrodynamics
International Nuclear Information System (INIS)
Dölger, Julia; Bohr, Tomas; Andersen, Anders
2017-01-01
Flagellates are unicellular microswimmers that propel themselves using one or several beating flagella. We consider a hydrodynamic model of flagellates and explore the effect of flagellar arrangement and beat pattern on swimming kinematics and near-cell flow. The model is based on the analytical solution by Oseen for the low Reynolds number flow due to a point force outside a no-slip sphere. The no-slip sphere represents the cell and the point force a single flagellum. By superposition we are able to model a freely swimming flagellate with several flagella. For biflagellates with left–right symmetric flagellar arrangements we determine the swimming velocity, and we show that transversal forces due to the periodic movements of the flagella can promote swimming. For a model flagellate with both a longitudinal and a transversal flagellum we determine radius and pitch of the helical swimming trajectory. We find that the longitudinal flagellum is responsible for the average translational motion whereas the transversal flagellum governs the rotational motion. Finally, we show that the transversal flagellum can lead to strong feeding currents to localized capture sites on the cell surface. (paper)
A hydrodynamic model for cooperating solidary countries
De Luca, Roberto; Di Mauro, Marco; Falzarano, Angelo; Naddeo, Adele
2017-07-01
The goal of international trade theories is to explain the exchange of goods and services between different countries, aiming to benefit from it. Albeit the idea is very simple and known since ancient history, smart policy and business strategies need to be implemented by each subject, resulting in a complex as well as not obvious interplay. In order to understand such a complexity, different theories have been developed since the sixteenth century and today new ideas still continue to enter the game. Among them, the so called classical theories are country-based and range from Absolute and Comparative Advantage theories by A. Smith and D. Ricardo to Factor Proportions theory by E. Heckscher and B. Ohlin. In this work we build a simple hydrodynamic model, able to reproduce the main conclusions of Comparative Advantage theory in its simplest setup, i.e. a two-country world with country A and country B exchanging two goods within a genuine exchange-based economy and a trade flow ruled only by market forces. The model is further generalized by introducing money in order to discuss its role in shaping trade patterns. Advantages and drawbacks of the model are also discussed together with perspectives for its improvement.
Modeling the hydrodynamics of phloem sieve plates
Directory of Open Access Journals (Sweden)
Kaare Hartvig Jensen
2012-07-01
Full Text Available Sieve plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged. The resistance to the flow of viscous sap in the phloem vascular system is strongly affected by the presence of the sieve plates, but the hydrodynamics of the flow through them remains poorly understood. We propose a theoretical model for quantifying the effect of sieve plates on the phloem in the plant, thus unifying and improving previous work in the field. Numerical simulations of the flow in real and idealized phloem channels verify our model, and anatomical data from 19 plant species are investigated. We find that the sieve plate resistance is correlated to the cell lumen resistance, and that the sieve plate and the lumen contribute almost equally to the total hydraulic resistance of the phloem translocation pathway.
Model of Collective Fish Behavior with Hydrodynamic Interactions
Filella, Audrey; Nadal, François; Sire, Clément; Kanso, Eva; Eloy, Christophe
2018-05-01
Fish schooling is often modeled with self-propelled particles subject to phenomenological behavioral rules. Although fish are known to sense and exploit flow features, these models usually neglect hydrodynamics. Here, we propose a novel model that couples behavioral rules with far-field hydrodynamic interactions. We show that (1) a new "collective turning" phase emerges, (2) on average, individuals swim faster thanks to the fluid, and (3) the flow enhances behavioral noise. The results of this model suggest that hydrodynamic effects should be considered to fully understand the collective dynamics of fish.
Modeling hydrodynamic effects on choanoflagellate feeding
Oakes, Christian; Hguyen, Hoa; Koehl, Mimi; Fauci, Lisa
2017-11-01
Choanoflagellates are unicellular organisms whose intriguing morphology includes a set of collars/microvilli emanating from the cell body, surrounding the beating flagellum. As the closest living relative to animals, they are important for both ecological and evolutionary studies. Choanoflagellates have three unicellular types: slow swimmers, fast swimmers, and thecate (attached to a surface by a stalk). Each has different morphology and feeding rate. We use the method of regularized Stokeslets to simulate cell-fluid interactions of each type and show the hydrodynamic effects on the amount and directions of fluid flow toward the collar. After validating the swimming speeds of our models with experimental data, we calculate the rate of flow across a capture zone around the collar (flux). This sheds light on how each morphological aspect of the cell aids in bacteria capture during feeding. Among the three types, the thecate cells have the largest average flux values, implying that they take advantage of the nearby surface by creating eddies that draw bacteria into their collar for ingestion. Funding Source: FASTER Grant SURF `` National Science Foundation DUE S-STEM Award 1153796, Mach Fellowship.
Code Differentiation for Hydrodynamic Model Optimization
Energy Technology Data Exchange (ETDEWEB)
Henninger, R.J.; Maudlin, P.J.
1999-06-27
Use of a hydrodynamics code for experimental data fitting purposes (an optimization problem) requires information about how a computed result changes when the model parameters change. These so-called sensitivities provide the gradient that determines the search direction for modifying the parameters to find an optimal result. Here, the authors apply code-based automatic differentiation (AD) techniques applied in the forward and adjoint modes to two problems with 12 parameters to obtain these gradients and compare the computational efficiency and accuracy of the various methods. They fit the pressure trace from a one-dimensional flyer-plate experiment and examine the accuracy for a two-dimensional jet-formation problem. For the flyer-plate experiment, the adjoint mode requires similar or less computer time than the forward methods. Additional parameters will not change the adjoint mode run time appreciably, which is a distinct advantage for this method. Obtaining ''accurate'' sensitivities for the j et problem parameters remains problematic.
Kasimov, Aslan R; Faria, Luiz M; Rosales, Rodolfo R
2013-03-08
We propose the following model equation, u(t) + 1/2(u(2)-uu(s))x = f(x,u(s)) that predicts chaotic shock waves, similar to those in detonations in chemically reacting mixtures. The equation is given on the half line, xorder partial differential equation. The chaos arises in the equation thanks to an interplay between the nonlinearity of the inviscid Burgers equation and a novel forcing term that is nonlocal in nature and has deep physical roots in reactive Euler equations.
Donmez, Orhan
We present a general procedure to solve the General Relativistic Hydrodynamical (GRH) equations with Adaptive-Mesh Refinement (AMR) and model of an accretion disk around a black hole. To do this, the GRH equations are written in a conservative form to exploit their hyperbolic character. The numerical solutions of the general relativistic hydrodynamic equations is done by High Resolution Shock Capturing schemes (HRSC), specifically designed to solve non-linear hyperbolic systems of conservation laws. These schemes depend on the characteristic information of the system. We use Marquina fluxes with MUSCL left and right states to solve GRH equations. First, we carry out different test problems with uniform and AMR grids on the special relativistic hydrodynamics equations to verify the second order convergence of the code in 1D, 2 D and 3D. Second, we solve the GRH equations and use the general relativistic test problems to compare the numerical solutions with analytic ones. In order to this, we couple the flux part of general relativistic hydrodynamic equation with a source part using Strang splitting. The coupling of the GRH equations is carried out in a treatment which gives second order accurate solutions in space and time. The test problems examined include shock tubes, geodesic flows, and circular motion of particle around the black hole. Finally, we apply this code to the accretion disk problems around the black hole using the Schwarzschild metric at the background of the computational domain. We find spiral shocks on the accretion disk. They are observationally expected results. We also examine the star-disk interaction near a massive black hole. We find that when stars are grounded down or a hole is punched on the accretion disk, they create shock waves which destroy the accretion disk.
Connection between hydrodynamic, water bag and Vlasov models
International Nuclear Information System (INIS)
Gros, M.; Bertrand, P.; Feix, M.R.
1978-01-01
The connection between hydrodynamic, water bag and Vlasov models is still under consideration with numerical experiments. For long wavelength, slightly non linear excitations and initial preparations such as the usual adiabatic invariant Pn -3 is space independent, the hydrodynamic model is equivalent to the water bag, and for long wavelengths a nice agreement is found with the full numerical solution of the Vlasov equation. For other initial conditions when the water bag cannot be defined, the hydrodynamic approach does not represent the correct behaviour. (author)
Hydrodynamical model based on a bag-like Lagrangian
International Nuclear Information System (INIS)
Chiu, C.B.; Lam, C.S.; Wang, K.H.
1976-06-01
Equations of motion of hydrodynamical model are derived from a bag-like Lagrangian by using the technique of information theory. Comments on the break-up of the system and on the properties of decay products are included
Liquid metal targets for high-power applications : pulsed heating and shock hydrodynamics
International Nuclear Information System (INIS)
Hassanein, A.
2000-01-01
Significant interest has recently focused on the use of liquid-metal targets flowing with high velocities for various high-power nuclear and high-energy physics applications such as fusion reactor first-walls, the Spallation Neutron Source, Isotope Separation On Line, and Muon Collider projects. This is because the heat generated in solid targets due to beam or plasma bombardment cannot be removed easily and the resulting thermal shock damage could be a serious lifetime problem for long-term operation. More recently, the use of free or open flying-liquid jets has been proposed for higher-power-density applications. The behavior of a free-moving liquid mercury or gallium jet subjected to proton beam deposition in a strong magnetic field has been modeled and analyzed for the Muon Collider project. Free-liquid-metal jets can offer significant advantages over conventional solid targets, particularly for the more demanding and challenging high-power applications. However, the use of free-moving liquid-metal targets raises a number of new and challenging problems such as instabilities of the jet in a strong magnetic field, induced eddy-current effects on jet shape, thermal-shock formation, and possible jet fragmentation. Problems associated with shock heating of liquid jets in a strong magnetic field are analyzed in this study
On an incompressible model in radiation hydrodynamics
Czech Academy of Sciences Publication Activity Database
Ducomet, B.; Nečasová, Šárka
2015-01-01
Roč. 38, č. 4 (2015), s. 765-774 ISSN 0170-4214 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : radiation hydrodynamics * incompressible Navier-Stokes-Fourier system * weak solution Subject RIV: BA - General Mathematics Impact factor: 1.002, year: 2015 http://onlinelibrary.wiley.com/doi/10.1002/mma.3107/abstract
Numerical modeling of slow shocks
International Nuclear Information System (INIS)
Winske, D.
1987-01-01
This paper reviews previous attempt and the present status of efforts to understand the structure of slow shocks by means of time dependent numerical calculations. Studies carried out using MHD or hybrid-kinetic codes have demonstrated qualitative agreement with theory. A number of unresolved issues related to hybrid simulations of the internal shock structure are discussed in some detail. 43 refs., 8 figs
Pattern formation in flocking models: A hydrodynamic description.
Solon, Alexandre P; Caussin, Jean-Baptiste; Bartolo, Denis; Chaté, Hugues; Tailleur, Julien
2015-12-01
We study in detail the hydrodynamic theories describing the transition to collective motion in polar active matter, exemplified by the Vicsek and active Ising models. Using a simple phenomenological theory, we show the existence of an infinity of propagative solutions, describing both phase and microphase separation, that we fully characterize. We also show that the same results hold specifically in the hydrodynamic equations derived in the literature for the active Ising model and for a simplified version of the Vicsek model. We then study numerically the linear stability of these solutions. We show that stable ones constitute only a small fraction of them, which, however, includes all existing types. We further argue that, in practice, a coarsening mechanism leads towards phase-separated solutions. Finally, we construct the phase diagrams of the hydrodynamic equations proposed to qualitatively describe the Vicsek and active Ising models and connect our results to the phenomenology of the corresponding microscopic models.
Comparisons of hydrodynamic beam models with kinetic treatments
International Nuclear Information System (INIS)
Boyd, J.K.; Mark, J.W.; Sharp, W.M.; Yu, S.S.
1983-01-01
Hydrodynamic models have been derived by Mark and Yu and by others to describe energetic self-pinched beams, such as those used in ion-beam fusion. The closure of the Mark-Yu model is obtained with adiabatic assumptions mathematically analogous to those of Chew, Goldberger, and Low for MHD. The other models treated here use an ideal gas closure and a closure by Newcomb based on an expansion in V/sub th//V/sub z/. Features of these hydrodynamic beam models are compared with a kinetic treatment
Modeling of hydrodynamic cavitation reactors: a unified approach
Moholkar, V.S.; Pandit, A.B.
2001-01-01
An attempt has been made to present a unified theoretical model for the cavitating flow in a hydrodynamic cavitation reactor using the nonlinear continuum mixture model for two-phase flow as the basis. This model has been used to describe the radial motion of bubble in the cavitating flow in two
Hydrodynamic modelling of tidal inlets in Hue, Vietnam
Lam, N.T.; Verhagen, H.J.; Van der Wegen, M.
2003-01-01
Application of an one-dimensional numerical model for hydrodynamic simulation of a complex lagooninlet system in Vietnam is presented. Model results help to get a better understanding on the behaviour of the system. Based on the numerical model results and analytic solutions, stability of tidal
Automatization of hydrodynamic modelling in a Floreon+ system
Ronovsky, Ales; Kuchar, Stepan; Podhoranyi, Michal; Vojtek, David
2017-07-01
The paper describes fully automatized hydrodynamic modelling as a part of the Floreon+ system. The main purpose of hydrodynamic modelling in the disaster management is to provide an accurate overview of the hydrological situation in a given river catchment. Automatization of the process as a web service could provide us with immediate data based on extreme weather conditions, such as heavy rainfall, without the intervention of an expert. Such a service can be used by non scientific users such as fire-fighter operators or representatives of a military service organizing evacuation during floods or river dam breaks. The paper describes the whole process beginning with a definition of a schematization necessary for hydrodynamic model, gathering of necessary data and its processing for a simulation, the model itself and post processing of a result and visualization on a web service. The process is demonstrated on a real data collected during floods in our Moravian-Silesian region in 2010.
Progress and challenges in coupled hydrodynamic-ecological estuarine modeling
Ganju, Neil K.; Brush, Mark J.; Rashleigh, Brenda; Aretxabaleta, Alfredo L.; del Barrio, Pilar; Grear, Jason S.; Harris, Lora A.; Lake, Samuel J.; McCardell, Grant; O'Donnell, James; Ralston, David K.; Signell, Richard P.; Testa, Jeremy; Vaudrey, Jamie M. P.
2016-01-01
Numerical modeling has emerged over the last several decades as a widely accepted tool for investigations in environmental sciences. In estuarine research, hydrodynamic and ecological models have moved along parallel tracks with regard to complexity, refinement, computational power, and incorporation of uncertainty. Coupled hydrodynamic-ecological models have been used to assess ecosystem processes and interactions, simulate future scenarios, and evaluate remedial actions in response to eutrophication, habitat loss, and freshwater diversion. The need to couple hydrodynamic and ecological models to address research and management questions is clear because dynamic feedbacks between biotic and physical processes are critical interactions within ecosystems. In this review, we present historical and modern perspectives on estuarine hydrodynamic and ecological modeling, consider model limitations, and address aspects of model linkage, skill assessment, and complexity. We discuss the balance between spatial and temporal resolution and present examples using different spatiotemporal scales. Finally, we recommend future lines of inquiry, approaches to balance complexity and uncertainty, and model transparency and utility. It is idealistic to think we can pursue a “theory of everything” for estuarine models, but recent advances suggest that models for both scientific investigations and management applications will continue to improve in terms of realism, precision, and accuracy.
Modeling of nanoscale liquid mixture transport by density functional hydrodynamics
Dinariev, Oleg Yu.; Evseev, Nikolay V.
2017-06-01
Modeling of multiphase compositional hydrodynamics at nanoscale is performed by means of density functional hydrodynamics (DFH). DFH is the method based on density functional theory and continuum mechanics. This method has been developed by the authors over 20 years and used for modeling in various multiphase hydrodynamic applications. In this paper, DFH was further extended to encompass phenomena inherent in liquids at nanoscale. The new DFH extension is based on the introduction of external potentials for chemical components. These potentials are localized in the vicinity of solid surfaces and take account of the van der Waals forces. A set of numerical examples, including disjoining pressure, film precursors, anomalous rheology, liquid in contact with heterogeneous surface, capillary condensation, and forward and reverse osmosis, is presented to demonstrate modeling capabilities.
Assessing the Hydrogeomorphic Effects of Environmental Flows using Hydrodynamic Modeling.
Gregory, Angela; Morrison, Ryan R; Stone, Mark
2018-04-13
Water managers are increasingly using environmental flows (e-flows) as a tool to improve ecological conditions downstream from impoundments. Recent studies have called for e-flow approaches that explicitly consider impacts on hydrogeomorphic processes when developing management alternatives. Process-based approaches are particularly relevant in river systems that have been highly modified and where water supplies are over allocated. One-dimensional (1D) and two-dimensional (2D) hydrodynamic models can be used to resolve hydrogeomorphic processes at different spatial and temporal scales to support the development, testing, and refinement of e-flow hypotheses. Thus, the objective of this paper is to demonstrate the use of hydrodynamic models as a tool for assisting stakeholders in targeting and assessing environmental flows within a decision-making framework. We present a case study of e-flows on the Rio Chama in northern New Mexico, USA, where 1D and 2D hydrodynamic modeling was used within a collaborative process to implement an e-flow experiment. A specific goal of the e-flow process was to improve spawning habitat for brown trout by flushing fine sediments from gravel features. The results revealed that the 2D hydrodynamic model provided much greater insight with respect to hydrodynamic and sediment transport processes, which led to a reduction in the recommended e-flow discharge. The results suggest that 2D hydrodynamic models can be useful tools for improving process understanding, developing e-flow recommendations, and supporting adaptive management even when limited or no data are available for model calibration and validation.
Hydrodynamic modelling for relativistic heavy-ion collisions at RHIC ...
Indian Academy of Sciences (India)
model, to describe the microscopic evolution and decoupling of the hadronic ... progress on hydrodynamic modelling, investigation on the flow data and the ... and to describe and predict the soft particle physics in relativistic heavy-ion collisions [4]. It is based on the conservation laws of energy, momentum and net charge ...
Hoch, Jannis M.; Neal, Jeffrey C.; Baart, Fedor; Van Beek, Rens; Winsemius, Hessel C.; Bates, Paul D.; Bierkens, Marc F.P.
2017-01-01
We here present GLOFRIM, a globally applicable computational framework for integrated hydrological-hydrodynamic modelling. GLOFRIM facilitates spatially explicit coupling of hydrodynamic and hydrologic models and caters for an ensemble of models to be coupled. It currently encompasses the global
Reshocks, rarefactions, and the generalized Layzer model for hydrodynamic instabilities
International Nuclear Information System (INIS)
Mikaelian, K.O.
2008-01-01
We report numerical simulations and analytic modeling of shock tube experiments on Rayleigh-Taylor and Richtmyer-Meshkov instabilities. We examine single interfaces of the type A/B where the incident shock is initiated in A and the transmitted shock proceeds into B. Examples are He/air and air/He. In addition, we study finite-thickness or double-interface A/B/A configurations like air/SF 6 /air gas-curtain experiments. We first consider conventional shock tubes that have a 'fixed' boundary: A solid endwall which reflects the transmitted shock and reshocks the interface(s). Then we focus on new experiments with a 'free' boundary--a membrane disrupted mechanically or by the transmitted shock, sending back a rarefaction towards the interface(s). Complex acceleration histories are achieved, relevant for Inertial Confinement Fusion implosions. We compare our simulation results with a generalized Layzer model for two fluids with time-dependent densities, and derive a new freeze-out condition whereby accelerating and compressive forces cancel each other out. Except for the recently reported failures of the Layzer model, the generalized Layzer model and hydrocode simulations for reshocks and rarefactions agree well with each other, and remain to be verified experimentally
Reshocks, rarefactions, and the generalized Layzer model for hydrodynamic instabilities
Energy Technology Data Exchange (ETDEWEB)
Mikaelian, K O
2008-06-10
We report numerical simulations and analytic modeling of shock tube experiments on Rayleigh-Taylor and Richtmyer-Meshkov instabilities. We examine single interfaces of the type A/B where the incident shock is initiated in A and the transmitted shock proceeds into B. Examples are He/air and air/He. In addition, we study finite-thickness or double-interface A/B/A configurations like air/SF{sub 6}/air gas-curtain experiments. We first consider conventional shock tubes that have a 'fixed' boundary: A solid endwall which reflects the transmitted shock and reshocks the interface(s). Then we focus on new experiments with a 'free' boundary--a membrane disrupted mechanically or by the transmitted shock, sending back a rarefaction towards the interface(s). Complex acceleration histories are achieved, relevant for Inertial Confinement Fusion implosions. We compare our simulation results with a generalized Layzer model for two fluids with time-dependent densities, and derive a new freeze-out condition whereby accelerating and compressive forces cancel each other out. Except for the recently reported failures of the Layzer model, the generalized Layzer model and hydrocode simulations for reshocks and rarefactions agree well with each other, and remain to be verified experimentally.
Thermal chemical-mechanical reactive flow model of shock initiation in solid explosives
International Nuclear Information System (INIS)
Nicholls, A.L. III; Tarver, C.M.
1998-01-01
The three dimensional Arbitrary Lagrange Eulerian hydrodynamic computer code ALE3D with fully coupled thermal-chemical-mechanical material models provides the framework for the development of a physically realistic model of shock initiation and detonation of solid explosives. The processes of hot spot formation during shock compression, subsequent ignition of reaction or failure to react, growth of reaction in individual hot spots, and coalescence of reacting hot spots during the transition to detonation can now be modeled using Arrhenius chemical kinetic rate laws and heat transfer to propagate the reactive flow. This paper discusses the growth rates of reacting hot spots in HMX and TATB and their coalescence during shock to detonation transition. Hot spot deflagration rates are found to be fast enough to consume explosive particles less than 10 mm in diameter during typical shock duration times, but larger particles must fragment and create more reactive surface area in order to be rapidly consumed
International Nuclear Information System (INIS)
Wilkins, M.L.
1979-01-01
Various aspects of hydrodynamics and elastic--plastic flow are introduced for the purpose of defining hydrodynamic terms and explaining what some of the important hydrodynamic concepts are. The first part covers hydrodynamic theory; and discussed fundamental hydrodynamic equations, discontinuities, and shock, detonation, and elastic--plastic waves. The second part deals with applications of hydrodynamic theory to material equations of state, spall, Taylor instabilities, and detonation pressure measurements
Hydrodynamic model of hydrogen-flame propagation in reactor vessels
International Nuclear Information System (INIS)
Baer, M.R.; Ratzel, A.C.
1982-01-01
A hydrodynamic model for hydrogen flame propagation in reactor geometries is presented. This model is consistent with the theory of slow combustion in which the gasdynamic field equations are treated in the limit of small Mach numbers. To the lowest order, pressure is spatially uniform. The flame is treated as a density and entropy discontinuity which propagates at prescribed burning velocities, corresponding to laminar or turbulent flames. Radiation cooling of the burned combustion gases and possible preheating of the unburned gases during propagation of the flame is included using a molecular gas-band thermal radiation model. Application of this model has been developed for 1-D variable area flame propagation. Multidimensional effects induced by hydrodynamics and buoyancy are introduced as a correction to the burn velocity (which reflects a modification of planar flame surface to a distorted surface) using experimentally measured pressure-rise time data for hydrogen/air deflagrations in cylindrical vessels
Reliability assessment of competing risks with generalized mixed shock models
International Nuclear Information System (INIS)
Rafiee, Koosha; Feng, Qianmei; Coit, David W.
2017-01-01
This paper investigates reliability modeling for systems subject to dependent competing risks considering the impact from a new generalized mixed shock model. Two dependent competing risks are soft failure due to a degradation process, and hard failure due to random shocks. The shock process contains fatal shocks that can cause hard failure instantaneously, and nonfatal shocks that impact the system in three different ways: 1) damaging the unit by immediately increasing the degradation level, 2) speeding up the deterioration by accelerating the degradation rate, and 3) weakening the unit strength by reducing the hard failure threshold. While the first impact from nonfatal shocks comes from each individual shock, the other two impacts are realized when the condition for a new generalized mixed shock model is satisfied. Unlike most existing mixed shock models that consider a combination of two shock patterns, our new generalized mixed shock model includes three classic shock patterns. According to the proposed generalized mixed shock model, the degradation rate and the hard failure threshold can simultaneously shift multiple times, whenever the condition for one of these three shock patterns is satisfied. An example using micro-electro-mechanical systems devices illustrates the effectiveness of the proposed approach with sensitivity analysis. - Highlights: • A rich reliability model for systems subject to dependent failures is proposed. • The degradation rate and the hard failure threshold can shift simultaneously. • The shift is triggered by a new generalized mixed shock model. • The shift can occur multiple times under the generalized mixed shock model.
Numerical simulations of radiation hydrodynamics and modeling of high temperature hohlraum cavities
International Nuclear Information System (INIS)
Gupta, N.K.; Godwal, B.K.
2003-10-01
A summary of our efforts towards the validation of radiation hydrodynamics and opacity models are presented. Effects of various parameters on the radiation temperature inside an inertial confinement fusion (ICF) hohlraum, the effects of non-local thermodynamic equilibrium conditions on emission and absorption, and the hydrodynamics of aluminium and gold foils driven by radiation are studied. LTE and non-LTE predictions for emitted radiation are compared with the experimental results and it is seen that non-LTE simulations show a marked improvement over LTE results. It is shown that the mixing of two high Z materials can lead to an enhancement in the Rosseland mean. An experimental study of soft x-ray emission from laser-irradiated Au-Cu mix-Z targets confirmed these predictions. It is seen that only multi group non-LTE radiation transport is able to explain experimentally observed features in the conversion efficiency of laser light to x-rays. One group radiation transport under predicts the radiation temperature. It is shown that erroneous results can be obtained if the space mesh in the hohlraum wall is not fine enough. Hydrodynamics of a wedge shaped aluminium foil driven by the hohlraum radiation is also presented and results are compared with NOVA laser experiments. Laser driven shock wave EOS and gold hohlraum experiments carried out at CAT are analyzed and they confirmed our theoretical estimates. (author)
Shock circle model for ejector performance evaluation
International Nuclear Information System (INIS)
Zhu, Yinhai; Cai, Wenjian; Wen, Changyun; Li, Yanzhong
2007-01-01
In this paper, a novel shock circle model for the prediction of ejector performance at the critical mode operation is proposed. By introducing the 'shock circle' at the entrance of the constant area chamber, a 2D exponential expression for velocity distribution is adopted to approximate the viscosity flow near the ejector inner wall. The advantage of the 'shock circle' analysis is that the calculation of ejector performance is independent of the flows in the constant area chamber and diffuser. Consequently, the calculation is even simpler than many 1D modeling methods and can predict the performance of critical mode operation ejectors much more accurately. The effectiveness of the method is validated by two experimental results reported earlier. The proposed modeling method using two coefficients is shown to produce entrainment ratio, efficiency and coefficient of performance (COP) accurately and much closer to experimental results than those of 1D analysis methods
Modeling of Hydrodynamic Chromatography for Colloid Migration in Fractured Rock
International Nuclear Information System (INIS)
Li Shihhai; Jen, C.-P.
2001-01-01
The role of colloids in the migration of radionuclides in the geosphere has been emphasized in the performance assessment of high-level radioactive waste disposal. The literature indicates that the colloid velocity may not be equal to the velocity of groundwater owing to hydrodynamic chromatography. A theoretical model for hydrodynamic chromatography of colloid migration in the fracture is proposed in the present work. In this model, the colloids are treated as nonreactive and the external forces acting on colloidal particles are considered including the inertial force, the van der Waals attractive force, and the electrical double-layer repulsive force, as well as the gravitational force. A fully developed concentration profile for colloids is obtained to elucidate migration behavior for colloids in the fracture. The effects of parameters governing these forces and the aperture of the fracture are determined using a theoretical model
Towards a smoothed particle hydrodynamics algorithm for shocks through layered materials
Zisis, I.A.; Linden, van der B.J.; Giannopapa, C.G.
2013-01-01
Hypervelocity impacts (HVIs) are collisions at velocities greater than the target object’s speed of sound. Such impacts produce pressure waves that generate sharp and sudden changes in the density of the materials. These are propagated as shock waves. Previous computational research has given
Droplet and multiphase effects in a shock-driven hydrodynamic instability with reshock
Middlebrooks, John B.; Avgoustopoulos, Constantine G.; Black, Wolfgang J.; Allen, Roy C.; McFarland, Jacob A.
2018-06-01
Shock-driven multiphase instabilities (SDMI) are unique physical phenomena that have far-reaching applications in engineering and science such as high energy explosions, scramjet combustors, and supernovae events. The SDMI arises when a multiphase field is impulsively accelerated by a shock wave and evolves as a result of gradients in particle-gas momentum transfer. A new shock tube facility has been constructed to study the SDMI. Experiments were conducted to investigate liquid particle and multiphase effects in the SDMI. A multiphase cylindrical interface was created with water droplet laden air in our horizontal shock tube facility. The interface was accelerated by a Mach 1.66 shock wave, and its reflection from the end wall. The interface development was captured using laser illumination and a high-resolution CCD camera. Laser interferometry was used to determine the droplet size distribution. A particle filtration technique was used to determine mass loading within an interface and verify particle size distribution. The effects of particle number density, particle size, and a secondary acceleration (reshock) of the interface were noted. Particle number density effects were found comparable to Atwood number effects in the Richtmyer-Meshkov instability for small (˜ 1.7 {μ }m) droplets. Evaporation was observed to alter droplet sizes and number density, markedly after reshock. For large diameter droplets (˜ 10.7 {μ }m), diminished development was observed with larger droplets lagging far behind the interface. These lagging droplets were also observed to breakup after reshock into structured clusters of smaller droplets. Mixing width values were reported to quantify mixing effects seen in images.
Hydrodynamics of Mangrove Root-Type Models
Kazemi, Amirkhosro
Mangrove trees play a prominent role in coastal tropic and subtropical regions, providing habitat for many organisms and protecting shorelines against storm surges, high winds, erosion, and tsunamis. The motivation of this proposal is to understand the complex interaction of mangrove roots during tidal flow conditions using simplified physical models. In this dissertation, the mangrove roots were modeled with a circular array of cylinders with different porosities and spacing ratios. In addition, we modeled the flexibility of the roots by attaching rigid cylinders to hinge connectors. The models were tested in a water tunnel for a range of Reynolds number from 2200 to 11000. Additionally, we performed 2D flow visualization for different root models in a flowing soap film setup. We measured drag force and the instantaneous streamwise velocity downstream of the models. Furthermore, we investigated the fluid dynamics downstream of the models using a 2-D time-resolved particle image velocimetry (PIV), and flow visualization. The result was analyzed to present time-averaged and time-resolved flow parameters including the velocity distribution, vorticity, streamline, Reynolds shear stress and turbulent kinetic vi energy. We found that the frequency of the vortex shedding increases as the diameter of the small cylinders decreases while the patch diameter is constant, therefore increasing the Strouhal number, St = fD/U. By comparing the change of Strouhal numbers with a single solid cylinder, we introduced a new length scale, the "effective diameter". In addition, the effective diameter of the patch decreases as the porosity increases. In addition, patch drag decreases linearly as the spacing ratio increases. For flexible cylinders, we found that a decrease in stiffness increases both patch drag and the wake deficit behind the patch in a similar fashion as increasing the blockage of the patch. The average drag coefficient decreased with increasing Reynolds number and with
Analytical model for fast-shock ignition
International Nuclear Information System (INIS)
Ghasemi, S. A.; Farahbod, A. H.; Sobhanian, S.
2014-01-01
A model and its improvements are introduced for a recently proposed approach to inertial confinement fusion, called fast-shock ignition (FSI). The analysis is based upon the gain models of fast ignition, shock ignition and considerations for the fast electrons penetration into the pre-compressed fuel to examine the formation of an effective central hot spot. Calculations of fast electrons penetration into the dense fuel show that if the initial electron kinetic energy is of the order ∼4.5 MeV, the electrons effectively reach the central part of the fuel. To evaluate more realistically the performance of FSI approach, we have used a quasi-two temperature electron energy distribution function of Strozzi (2012) and fast ignitor energy formula of Bellei (2013) that are consistent with 3D PIC simulations for different values of fast ignitor laser wavelength and coupling efficiency. The general advantages of fast-shock ignition in comparison with the shock ignition can be estimated to be better than 1.3 and it is seen that the best results can be obtained for the fuel mass around 1.5 mg, fast ignitor laser wavelength ∼0.3 micron and the shock ignitor energy weight factor about 0.25
Energy Technology Data Exchange (ETDEWEB)
Peralta, Pedro [Arizona State Univ., Tempe, AZ (United States); Fortin, Elizabeth [Arizona State Univ., Tempe, AZ (United States); Opie, Saul [Arizona State Univ., Tempe, AZ (United States); Gautam, Sudrishti [Arizona State Univ., Tempe, AZ (United States); Gopalakrishnan, Ashish [Arizona State Univ., Tempe, AZ (United States); Lynch, Jenna [Arizona State Univ., Tempe, AZ (United States); Chen, Yan [Arizona State Univ., Tempe, AZ (United States); Loomis, Eric [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-03-01
Activities for this grant included: 1) Development of dynamic impact experiments to probe strength and phase transition influence on dynamic deformation, 2) development of modern strength and phase aware simulation capabilities, 3) and post-processing of experimental data with simulation and closed form analytical techniques. Two different dynamic experiments were developed to probe material strengths in solid metals (largely copper and iron in this effort). In the first experiment a flyer plate impacts a flat target with an opposite rippled surface that is partially supported by a weaker window material. Post mortem analysis of the target sample showed a strong and repeatable residual plastic deformation dependence on grain orientation. Yield strengths for strain rates near 10^{5} s^{-1} and plastic strains near ~50% were estimated to be around 180 to 240 MPa, varying in this range with grain orientation. Unfortunately dynamic real-time measurements were difficult with this setup due to diagnostic laser scattering; hence, an additional experimental setup was developed to complement these results. In the second set of experiments a rippled surface was ablated by a controlled laser pulsed, which launched a rippled shock front to an opposite initially flat diagnostic surface that was monitored in real-time with spatially resolved velocimetry techniques, e.g., line VISAR in addition to Transient Imaging Displacement Interferometry (TIDI) displacement measurements. This setup limited the displacements at the diagnostic surface to a reasonable level for TIDI measurements (~ less than one micrometer). These experiments coupled with analytical and numerical solutions provided evidence that viscous and elastic deviatoric strength affect shock front perturbation evolution in clearly different ways. Particularly, normalized shock front perturbation amplitudes evolve with viscosity (η) and perturbation wavelength (λ) as η/λ, such that increasing viscosity
Elliptic flow based on a relativistic hydrodynamic model
Energy Technology Data Exchange (ETDEWEB)
Hirano, Tetsufumi [Department of Physics, Waseda Univ., Tokyo (Japan)
1999-08-01
Based on the (3+1)-dimensional hydrodynamic model, the space-time evolution of hot and dense nuclear matter produced in non-central relativistic heavy-ion collisions is discussed. The elliptic flow parameter v{sub 2} is obtained by Fourier analysis of the azimuthal distribution of pions and protons which are emitted from the freeze-out hypersurface. As a function of rapidity, the pion and proton elliptic flow parameters both have a peak at midrapidity. (author)
Numerical modeling of hydrodynamic in southwestern Johor, Malaysia
Jusoh, Wan Hasliza Wan; Tangang, Fredolin; Juneng, Liew; Hamid, Mohd. Radzi Abdul
2014-09-01
Tanjung Piai located at the southwest of Johor, Malaysia faces severe erosion since a few decades ago. Considering the condition in this particular area, understanding of its hydrodynamic behaviour should be clearly explained. Thus, a numerical modelling has been applied in this study in order to investigate the hydrodynamic of current flow along the study area. Hydrodynamic study was carried out by applying a numerical modelling of MIKE 21 software based on flexible mesh grids. The model generally described the current flow pattern in the study area corresponding to the several flows from surrounding water regime which are Malacca Strait, Singapore Strait and Java Sea. The interaction of various water flows in the area of Tanjung Piai which is located in the middle part of the meeting of the currents to have a very complicated hydrodynamic conditions. The study area generally experienced two tidal phase in a day as the water flows is greatly influenced by the adjacent water flow from Malacca and Singapore Straits. During first tidal cycle, the most dominant flow is influenced by a single water flow which is Malacca Strait for both ebbing and flooding event. The current velocity was generally higher during this first tidal phase particularly at the tips of Tanjung Piai where severe erosion is spotted. However, the second tidal phase gives different stress to the study area as the flow is relatively dominated by both Malacca and Singapore Straits. During this phase, the meeting of current from both straits can be discovered near to the Tanjung Piai as this occurrence makes relatively slower current velocity around the study area. Basically, the numerical modelling result in this study can be considered as basic information in describing the condition of study area as it would be very useful for extensive study especially the study of sediment transport and morphological processes in the coastal area.
Modeling shock waves in an ideal gas: Going beyond the Navier-Stokes level
International Nuclear Information System (INIS)
Holian, B.L.; Patterson, C.W.; Mareschal, M.; Salomons, E.
1993-01-01
We model a shock wave in an ideal gas by solving a modified version of the compressible Navier-Stokes equations of hydrodynamics, where, following an earlier conjecture by Holian [Phys. Rev. A 37, 2562 (1988)], we use the temperature in the direction of shock propagation T xx , rather than the average temperature T=(T xx +T yy +T zz )/3, in the evaluation of the linear transport coefficients. The results are found to agree much better with the molecular-dynamics simulations of Salomons and Mareschal [Phys. Rev. Lett. 69, 269 (1992)] than standard Navier-Stokes theory
Hydrodynamic Modeling on Suciu River (Maramures County
Directory of Open Access Journals (Sweden)
Năsui Daniel
2016-06-01
Full Text Available The GIS database containing the topographic and land use information was made in 2012, followed by field measurements surveys in 2013 and 2014. A number of 11 cross-sections were topographically apprised in the valley along the 11 km river reach. The geometric data requirements for the modeling software were prepared in ESRI’s ArcGIS™ 9.2 software using the HEC-GeoRAS extension. The steady flow data was edited in the HEC-RAS one-dimensional flow modeling software. Four scenarios were used for the river discharge, from normal to overflow. The results come in different forms, from tabular output, to stage hydrograph, to velocity distribution or 3D diagrams, all of which give a clear vision on the overflow high risk areas. The results were exported back to the GIS extension for additional spatial operations. Flow velocity maps were generated for each discharge scenario. Although the scenarios included very high discharge values, the flood impact on people assets is minimal. The reasons for this are the high slope of the riverbed and the proper placement in the floodplain, due mainly to the flood management works that took place after the 1970 flood.
Differential invariants in nonclassical models of hydrodynamics
Bublik, Vasily V.
2017-10-01
In this paper, differential invariants are used to construct solutions for equations of the dynamics of a viscous heat-conducting gas and the dynamics of a viscous incompressible fluid modified by nanopowder inoculators. To describe the dynamics of a viscous heat-conducting gas, we use the complete system of Navier—Stokes equations with allowance for heat fluxes. Mathematical description of the dynamics of liquid metals under high-energy external influences (laser radiation or plasma flow) includes, in addition to the Navier—Stokes system of an incompressible viscous fluid, also heat fluxes and processes of nonequilibrium crystallization of a deformable fluid. Differentially invariant solutions are a generalization of partially invariant solutions, and their active study for various models of continuous medium mechanics is just beginning. Differentially invariant solutions can also be considered as solutions with differential constraints; therefore, when developing them, the approaches and methods developed by the science schools of academicians N. N. Yanenko and A. F. Sidorov will be actively used. In the construction of partially invariant and differentially invariant solutions, there are overdetermined systems of differential equations that require a compatibility analysis. The algorithms for reducing such systems to involution in a finite number of steps are described by Cartan, Finikov, Kuranishi, and other authors. However, the difficultly foreseeable volume of intermediate calculations complicates their practical application. Therefore, the methods of computer algebra are actively used here, which largely helps in solving this difficult problem. It is proposed to use the constructed exact solutions as tests for formulas, algorithms and their software implementations when developing and creating numerical methods and computational program complexes. This combination of effective numerical methods, capable of solving a wide class of problems, with
CHF Enhancement by Surface Patterning based on Hydrodynamic Instability Model
Energy Technology Data Exchange (ETDEWEB)
Seo, Han; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of)
2015-05-15
If the power density of a device exceeds the CHF point, bubbles and vapor films will be covered on the whole heater surface. Because vapor films have much lower heat transfer capabilities compared to the liquid layer, the temperature of the heater surface will increase rapidly, and the device could be damaged due to the heater burnout. Therefore, the prediction and the enhancement of the CHF are essential to maximizing the efficient heat removal region. Numerous studies have been conducted to describe the CHF phenomenon, such as hydrodynamic instability theory, macrolayer dryout theory, hot/dry spot theory, and bubble interaction theory. The hydrodynamic instability model, proposed by Zuber, is the predominant CHF model that Helmholtz instability attributed to the CHF. Zuber assumed that the Rayleigh-Taylor (RT) instability wavelength is related to the Helmholtz wavelength. Lienhard and Dhir proposed a CHF model that Helmholtz instability wavelength is equal to the most dangerous RT wavelength. In addition, they showed the heater size effect using various heater surfaces. Lu et al. proposed a modified hydrodynamic theory that the Helmholtz instability was assumed to be the heater size and the area of the vapor column was used as a fitting factor. The modified hydrodynamic theories were based on the change of Helmholtz wavelength related to the RT instability wavelength. In the present study, the change of the RT instability wavelength, based on the heater surface modification, was conducted to show the CHF enhancement based on the heater surface patterning in a plate pool boiling. Sapphire glass was used as a base heater substrate, and the Pt film was used as a heating source. The patterning surface was based on the change of RT instability wavelength. In the present work the study of the CHF was conducted using bare Pt and patterned heating surfaces.
Constitutive modeling of shock response of PTFE
Energy Technology Data Exchange (ETDEWEB)
Brown, Eric N [Los Alamos National Laboratory; Reanyansky, Anatoly D [DSTO, AUSTRALIA; Bourne, Neil K [AWE, UK; Millett, Jeremy C F [AWE, UK
2009-01-01
The PTFE (polytetrafluoroethylene) material is complex and attracts attention of the shock physics researchers because it has amorphous and crystalline components. In turn, the crystalline component has four known phases with the high pressure transition to phase III. At the same time, as has been recently studied using spectrometry, the crystalline region is growing with load. Stress and velocity shock-wave profiles acquired recently with embedded gauges demonstrate feature that may be related to impedance mismatches between the regions subjected to some transitions resulting in density and modulus variations. We consider the above mentioned amorphous-to-crystalline transition and the high pressure Phase II-to-III transitions as possible candidates for the analysis. The present work utilizes a multi-phase rate sensitive model to describe shock response of the PTFE material. One-dimensional experimental shock wave profiles are compared with calculated profiles with the kinetics describing the transitions. The objective of this study is to understand the role of the various transitions in the shock response of PTFE.
Relativistic Coulomb excitation of giant resonances in the hydrodynamic model
International Nuclear Information System (INIS)
Vasconcellos Gomes, Ana Cristina de.
1990-05-01
We investigate the Coulomb excitation of giant dipole resonances in relativistic heavy ion collisions using a macroscopic hydrodynamical model for the harmonic vibrations of the nuclear fluid. The motion is treated as a combination of the Goldhaber-Teller displacement mode and the Steinwedel-Jensen acoustic mode, and the restoring forces are calculated using the droplet model. This model is used as input to study the characteristics of multiple excitation of giant dipole resonances in nuclei. Possible signatures for the existence of such states are also discussed quantitatively. (author). 52 refs., 14 figs., 3 tabs
Use of hydrologic and hydrodynamic modeling for ecosystem restoration
Obeysekera, J.; Kuebler, L.; Ahmed, S.; Chang, M.-L.; Engel, V.; Langevin, C.; Swain, E.; Wan, Y.
2011-01-01
Planning and implementation of unprecedented projects for restoring the greater Everglades ecosystem are underway and the hydrologic and hydrodynamic modeling of restoration alternatives has become essential for success of restoration efforts. In view of the complex nature of the South Florida water resources system, regional-scale (system-wide) hydrologic models have been developed and used extensively for the development of the Comprehensive Everglades Restoration Plan. In addition, numerous subregional-scale hydrologic and hydrodynamic models have been developed and are being used for evaluating project-scale water management plans associated with urban, agricultural, and inland costal ecosystems. The authors provide a comprehensive summary of models of all scales, as well as the next generation models under development to meet the future needs of ecosystem restoration efforts in South Florida. The multiagency efforts to develop and apply models have allowed the agencies to understand the complex hydrologic interactions, quantify appropriate performance measures, and use new technologies in simulation algorithms, software development, and GIS/database techniques to meet the future modeling needs of the ecosystem restoration programs. Copyright ?? 2011 Taylor & Francis Group, LLC.
Similarity flows in relativistic hydrodynamics
International Nuclear Information System (INIS)
Blaizot, J.P.; Ollitrault, J.Y.
1986-01-01
In ultra-relativistic heavy ion collisions, one expects in particular to observe a deconfinement transition leading to a formation of quark gluon plasma. In the framework of the hydrodynamic model, experimental signatures of such a plasma may be looked for as observable consequences of a first order transition on the evolution of the system. In most of the possible scenario, the phase transition is accompanied with discontinuities in the hydrodynamic flow, such as shock waves. The method presented in this paper has been developed to treat without too much numerical effort such discontinuous flow. It relies heavily on the use of similarity solutions of the hydrodynamic equations
Monetary Shocks in Models with Inattentive Producers.
Alvarez, Fernando E; Lippi, Francesco; Paciello, Luigi
2016-04-01
We study models where prices respond slowly to shocks because firms are rationally inattentive. Producers must pay a cost to observe the determinants of the current profit maximizing price, and hence observe them infrequently. To generate large real effects of monetary shocks in such a model the time between observations must be long and/or highly volatile. Previous work on rational inattentiveness has allowed for observation intervals that are either constant-but-long ( e.g . Caballero, 1989 or Reis, 2006) or volatile-but-short ( e.g . Reis's, 2006 example where observation costs are negligible), but not both. In these models, the real effects of monetary policy are small for realistic values of the duration between observations. We show that non-negligible observation costs produce both of these effects: intervals between observations are infrequent and volatile. This generates large real effects of monetary policy for realistic values of the average time between observations.
Validation of a Global Hydrodynamic Flood Inundation Model
Bates, P. D.; Smith, A.; Sampson, C. C.; Alfieri, L.; Neal, J. C.
2014-12-01
In this work we present first validation results for a hyper-resolution global flood inundation model. We use a true hydrodynamic model (LISFLOOD-FP) to simulate flood inundation at 1km resolution globally and then use downscaling algorithms to determine flood extent and depth at 90m spatial resolution. Terrain data are taken from a custom version of the SRTM data set that has been processed specifically for hydrodynamic modelling. Return periods of flood flows along the entire global river network are determined using: (1) empirical relationships between catchment characteristics and index flood magnitude in different hydroclimatic zones derived from global runoff data; and (2) an index flood growth curve, also empirically derived. Bankful return period flow is then used to set channel width and depth, and flood defence impacts are modelled using empirical relationships between GDP, urbanization and defence standard of protection. The results of these simulations are global flood hazard maps for a number of different return period events from 1 in 5 to 1 in 1000 years. We compare these predictions to flood hazard maps developed by national government agencies in the UK and Germany using similar methods but employing detailed local data, and to observed flood extent at a number of sites including St. Louis, USA and Bangkok in Thailand. Results show that global flood hazard models can have considerable skill given careful treatment to overcome errors in the publicly available data that are used as their input.
Hydrodynamic and Ecological Assessment of Nearshore Restoration: A Modeling Study
International Nuclear Information System (INIS)
Yang, Zhaoqing; Sobocinski, Kathryn L.; Heatwole, Danelle W.; Khangaonkar, Tarang; Thom, Ronald M.; Fuller, Roger
2010-01-01
Along the Pacific Northwest coast, much of the estuarine habitat has been diked over the last century for agricultural land use, residential and commercial development, and transportation corridors. As a result, many of the ecological processes and functions have been disrupted. To protect coastal habitats that are vital to aquatic species, many restoration projects are currently underway to restore the estuarine and coastal ecosystems through dike breaches, setbacks, and removals. Information on physical processes and hydrodynamic conditions are critical for the assessment of the success of restoration actions. Restoration of a 160- acre property at the mouth of the Stillaguamish River in Puget Sound has been proposed. The goal is to restore native tidal habitats and estuary-scale ecological processes by removing the dike. In this study, a three-dimensional hydrodynamic model was developed for the Stillaguamish River estuary to simulate estuarine processes. The model was calibrated to observed tide, current, and salinity data for existing conditions and applied to simulate the hydrodynamic responses to two restoration alternatives. Responses were evaluated at the scale of the restoration footprint. Model data was combined with biophysical data to predict habitat responses at the site. Results showed that the proposed dike removal would result in desired tidal flushing and conditions that would support four habitat types on the restoration footprint. At the estuary scale, restoration would substantially increase the proportion of area flushed with freshwater (< 5 ppt) at flood tide. Potential implications of predicted changes in salinity and flow dynamics are discussed relative to the distribution of tidal marsh habitat.
Hydrodynamic description of spin Calogero-Sutherland model
Abanov, Alexander; Kulkarni, Manas; Franchini, Fabio
2009-03-01
We study a non-linear collective field theory for an integrable spin-Calogero-Sutherland model. The hydrodynamic description of this SU(2) model in terms of charge density, charge velocity and spin currents is used to study non-perturbative solutions (solitons) and examine their correspondence with known quantum numbers of elementary excitations [1]. A conventional linear bosonization or harmonic approximation is not sufficient to describe, for example, the physics of spin-charge (non)separation. Therefore, we need this new collective bosonic field description that captures the effects of the band curvature. In the strong coupling limit [2] this model reduces to integrable SU(2) Haldane-Shastry model. We study a non-linear coupling of left and right spin currents which form a Kac-Moody algebra. Our quantum hydrodynamic description for the spin case is an extension for the one found in the spinless version in [3].[3pt] [1] Y. Kato,T. Yamamoto, and M. Arikawa, J. Phys. Soc. Jpn. 66, 1954-1961 (1997).[0pt] [2] A. Polychronakos, Phys Rev Lett. 70,2329-2331(1993).[0pt] [3] A.G.Abanov and P.B. Wiegmann, Phys Rev Lett 95, 076402(2005)
Flux-limited diffusion models in radiation hydrodynamics
International Nuclear Information System (INIS)
Pomraning, G.C.; Szilard, R.H.
1993-01-01
The authors discuss certain flux-limited diffusion theories which approximately describe radiative transfer in the presence of steep spatial gradients. A new formulation is presented which generalizes a flux-limited description currently in widespread use for large radiation hydrodynamic calculations. This new formation allows more than one Case discrete mode to be described by a flux-limited diffusion equation. Such behavior is not extant in existing formulations. Numerical results predicted by these flux-limited diffusion models are presented for radiation penetration into an initially cold halfspace. 37 refs., 5 figs
Pion inclusive momentum distribution at 900 in hydrodynamical model
International Nuclear Information System (INIS)
Chiu, C.B.; Wang, K.H.
1975-01-01
It is shown that pion inclusive momentum distributions in pp-collisions at 90 0 up to FNAL and ISR energies can be accounted for by a hydrodynamical model, which has frame independence symmetry and incorporates the evaporation phenomena. Within the solution during its space--time development, the matter system only possesses a local thermal equilibrium but not a global equilibrium. The proper time interval needed to achieve this equilibrium comes out to be comparable to (with c = 1) the longitudinal dimension estimated previously based on considerations of quantum statistical fluctuation. (U.S.)
Energy Technology Data Exchange (ETDEWEB)
Brannon, Sean; Longcope, Dana [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)
2014-09-01
Magnetic reconnection in the corona results in contracting flare loops, releasing energy into plasma heating and shocks. The hydrodynamic shocks produced in this manner drive thermal conduction fronts (TCFs) which transport energy into the chromosphere and drive upflows (evaporation) and downflows (condensation) in the cooler, denser footpoint plasma. Observations have revealed that certain properties of the transition point between evaporation and condensation (the 'flow reversal point' or FRP), such as temperature and velocity-temperature derivative at the FRP, vary between different flares. These properties may provide a diagnostic tool to determine parameters of the coronal energy release mechanism and the loop atmosphere. In this study, we develop a one-dimensional hydrodynamical flare loop model with a simplified three-region atmosphere (chromosphere/transition region/corona), with TCFs initiated by shocks introduced in the corona. We investigate the effect of two different flare loop parameters (post-shock temperature and transition region temperature ratio) on the FRP properties. We find that both of the evaporation characteristics have scaling-law relationships to the varied flare parameters, and we report the scaling exponents for our model. This provides a means of using spectroscopic observations of the chromosphere as quantitative diagnostics of flare energy release in the corona.
Directory of Open Access Journals (Sweden)
Phung Khanh Lam
Full Text Available To identify risk factors and develop a prediction model for the development of profound and recurrent shock amongst children presenting with dengue shock syndrome (DSS.We analyzed data from a prospective cohort of children with DSS recruited at the Paediatric Intensive Care Unit of the Hospital for Tropical Disease in Ho Chi Minh City, Vietnam. The primary endpoint was "profound DSS", defined as ≥2 recurrent shock episodes (for subjects presenting in compensated shock, or ≥1 recurrent shock episodes (for subjects presenting initially with decompensated/hypotensive shock, and/or requirement for inotropic support. Recurrent shock was evaluated as a secondary endpoint. Risk factors were pre-defined clinical and laboratory variables collected at the time of presentation with shock. Prognostic model development was based on logistic regression and compared to several alternative approaches.The analysis population included 1207 children of whom 222 (18% progressed to "profound DSS" and 433 (36% had recurrent shock. Independent risk factors for both endpoints included younger age, earlier presentation, higher pulse rate, higher temperature, higher haematocrit and, for females, worse hemodynamic status at presentation. The final prognostic model for "profound DSS" showed acceptable discrimination (AUC=0.69 for internal validation and calibration and is presented as a simple score-chart.Several risk factors for development of profound or recurrent shock among children presenting with DSS were identified. The score-chart derived from the prognostic models should improve triage and management of children presenting with DSS in dengue-endemic areas.
Hydrodynamics and water quality models applied to Sepetiba Bay
Cunha, Cynara de L. da N.; Rosman, Paulo C. C.; Ferreira, Aldo Pacheco; Carlos do Nascimento Monteiro, Teófilo
2006-10-01
A coupled hydrodynamic and water quality model is used to simulate the pollution in Sepetiba Bay due to sewage effluent. Sepetiba Bay has a complicated geometry and bottom topography, and is located on the Brazilian coast near Rio de Janeiro. In the simulation, the dissolved oxygen (DO) concentration and biochemical oxygen demand (BOD) are used as indicators for the presence of organic matter in the body of water, and as parameters for evaluating the environmental pollution of the eastern part of Sepetiba Bay. Effluent sources in the model are taken from DO and BOD field measurements. The simulation results are consistent with field observations and demonstrate that the model has been correctly calibrated. The model is suitable for evaluating the environmental impact of sewage effluent on Sepetiba Bay from river inflows, assessing the feasibility of different treatment schemes, and developing specific monitoring activities. This approach has general applicability for environmental assessment of complicated coastal bays.
Non-hydrodynamic model of plasma focus structure
International Nuclear Information System (INIS)
Imshennik, V.S.; Zueva, N.M.; Lokutsievskij, O.V.; Mikhajlova, M.S.
1985-01-01
Experimental and theoretical plasma focus study has resulted in the necessity of creating a non-hydrodynamic plasma focus structure model (MKHD model). This model describes the final stage of plasma focus, which starts immediately after maximum plasma compression. It is related to a very limited space near the neck of the sausage instability. The MKHD model is two-dimensional, axially symmetric and collisionless with respect to the ions and magnetohydrodynamic with respect to the electrons; it accounts for the pinch instability of the sausage type (m=0 mode). The MKHD model, first of all, explains the long time of the plasma focus existence and non-thermonuclear peculiarities in the neutron yield. The initial and boundary conditions are formulated in accordance with the experiments and the results of computations in the 2D MHD model. A non-stationary process of plasma focus dynamics is studied numerically for a relatively long time - about 20 ns; this time is, in principle, not restricted. The computations show that the external edge of the neck expands rather slowly (at a speed that is lower than the thermal ion velocity, by an order of magnitude), and the magnetic field energy is converted to the kinetic energy of the chaotic ion motion (which is doubled for the time of computation). A 'supra-thermal' tail (with the deuterium ion energy higher than 10 keV) forms slowly at the ion distribution function; this tail determines a substantial part of the total neutron yield. The formation of stable vortices, which actually determine the structure of the plasma flow during the developed non-hydrodynamic stage of the plasma focus, is also found in the computations. These properties of the development of the sausage instability, as found in the numerical experiment with the MKHD plasma focus model, are in qualitative agreement with the behaviour of an instability of the same type in the MHD models of the Z-pinch
Coupling Hydrologic and Hydrodynamic Models to Estimate PMF
Felder, G.; Weingartner, R.
2015-12-01
Most sophisticated probable maximum flood (PMF) estimations derive the PMF from the probable maximum precipitation (PMP) by applying deterministic hydrologic models calibrated with observed data. This method is based on the assumption that the hydrological system is stationary, meaning that the system behaviour during the calibration period or the calibration event is presumed to be the same as it is during the PMF. However, as soon as a catchment-specific threshold is reached, the system is no longer stationary. At or beyond this threshold, retention areas, new flow paths, and changing runoff processes can strongly affect downstream peak discharge. These effects can be accounted for by coupling hydrologic and hydrodynamic models, a technique that is particularly promising when the expected peak discharge may considerably exceed the observed maximum discharge. In such cases, the coupling of hydrologic and hydraulic models has the potential to significantly increase the physical plausibility of PMF estimations. This procedure ensures both that the estimated extreme peak discharge does not exceed the physical limit based on riverbed capacity and that the dampening effect of inundation processes on peak discharge is considered. Our study discusses the prospect of considering retention effects on PMF estimations by coupling hydrologic and hydrodynamic models. This method is tested by forcing PREVAH, a semi-distributed deterministic hydrological model, with randomly generated, physically plausible extreme precipitation patterns. The resulting hydrographs are then used to externally force the hydraulic model BASEMENT-ETH (riverbed in 1D, potential inundation areas in 2D). Finally, the PMF estimation results obtained using the coupled modelling approach are compared to the results obtained using ordinary hydrologic modelling.
Beyond Hydrodynamic Modeling of AGN Heating in Galaxy Clusters
Yang, Hsiang-Yi Karen
Clusters of galaxies hold a unique position in hierarchical structure formation - they are both powerful cosmological probes and excellent astrophysical laboratories. Accurate modeling of the cluster properties is crucial for reducing systematic uncertainties in cluster cosmology. However, theoretical modeling of the intracluster medium (ICM) has long suffered from the "cooling-flow problem" - clusters with short central times or cool cores (CCs) are predicted to host massive inflows of gas that are not observed. Feedback from active galactic nuclei (AGN) is by far the most promising heating mechanism to counteract radiative cooling. Recent hydrodynamic simulations have made remarkable progress reproducing properties of the CCs. However, there remain two major questions that cannot be probed using purely hydrodynamic models: (1) what are the roles of cosmic rays (CRs)? (2) how is the existing picture altered when the ICM is modeled as weakly collisional plasma? We propose to move beyond limitations of pure hydrodynamics and progress toward a complete understanding of how AGN jet-inflated bubbles interact with their surroundings and provide heat to the ICM. Our objectives include: (1) understand how CR-dominated bubbles heat the ICM; (2) understand bubble evolution and sound-wave dissipation in the ICM with different assumptions of plasma properties, e.g., collisionality of the ICM, with or without anisotropic transport processes; (3) Develop a subgrid model of AGN heating that can be adopted in cosmological simulations based on state-of-the-art isolated simulations. We will use a combination of analytical calculations and idealized simulations to advance our understanding of each individual physical process. We will then perform the first three-dimensional (3D) magnetohydrodynamic (MHD) simulations of self-regulated AGN feedback with relevant CR and anisotropic transport processes in order to quantify the amount and distribution of heating from the AGN. Our
Towards the simplest hydrodynamic lattice-gas model.
Boghosian, Bruce M; Love, Peter J; Meyer, David A
2002-03-15
It has been known since 1986 that it is possible to construct simple lattice-gas cellular automata whose hydrodynamics are governed by the Navier-Stokes equations in two dimensions. The simplest such model heretofore known has six bits of state per site on a triangular lattice. In this work, we demonstrate that it is possible to construct a model with only five bits of state per site on a Kagome lattice. Moreover, the model has a simple, deterministic set of collision rules and is easily implemented on a computer. In this work, we derive the equilibrium distribution function for this lattice-gas automaton and carry out the Chapman-Enskog analysis to determine the form of the Navier-Stokes equations.
Floodplain hydrodynamic modelling of the Lower Volta River in Ghana
Directory of Open Access Journals (Sweden)
Frederick Yaw Logah
2017-12-01
Full Text Available The impacts of dam releases from re-operation scenarios of the Akosombo and Kpong hydropower facilities on downstream communities along the Lower Volta River were examined through hydrodynamic modelling using the HEC-RAS hydraulic model. The model was used to simulate surface water elevation along the river reach for specified discharge hydrographs from proposed re-operation dam release scenarios. The morphology of the river and its flood plains together with cross-sectional profiles at selected river sections were mapped and used in the hydrodynamic modelling. In addition, both suspended and bed-load sediment were sampled and analysed to determine the current sediment load of the river and its potential to carry more sediment. The modelling results indicate that large areas downstream of the dam including its flood plains would be inundated if dam releases came close to or exceeded 2300 m3/s. It is therefore recommended to relocate communities along the banks and in the flood plains of the Lower Volta River when dam releases are to exceed 2300 m3/s. Suspended sediment transport was found to be very low in the Lower Volta River and the predominant soil type in the river banks and bed is sandy soil. Thus, the geomorphology of the river can be expected to change considerably with time, particularly for sustained high releases from the Akosombo and Kpong dams. The results obtained from this study form a basis for assessing future sedimentation problems in the Lower Volta River and for underpinning the development of sediment control and management strategies for river basins in Ghana. Keywords: Geomorphology, HEC-RAS model, Dam release, Floodplain, Lower Volta River, Ghana
Hydrodynamic Equations for Flocking Models without Velocity Alignment
Peruani, Fernando
2017-10-01
The spontaneous emergence of collective motion patterns is usually associated with the presence of a velocity alignment mechanism that mediates the interactions among the moving individuals. Despite of this widespread view, it has been shown recently that several flocking behaviors can emerge in the absence of velocity alignment and as a result of short-range, position-based, attractive forces that act inside a vision cone. Here, we derive the corresponding hydrodynamic equations of a microscopic position-based flocking model, reviewing and extending previous reported results. In particular, we show that three distinct macroscopic collective behaviors can be observed: i) the coarsening of aggregates with no orientational order, ii) the emergence of static, elongated nematic bands, and iii) the formation of moving, locally polar structures, which we call worms. The derived hydrodynamic equations indicate that active particles interacting via position-based interactions belong to a distinct class of active systems fundamentally different from other active systems, including velocity-alignment-based flocking systems.
Challenges of citizen science contributions to modelling hydrodynamics of floods
Assumpção, Thaine Herman; Popescu, Ioana; Jonoski, Andreja; Solomatine, Dimitri P.
2017-04-01
Citizen science is an established mechanism in many fields of science, including ecology, biology and astronomy. Citizen participation ranges from collecting and interpreting data towards designing experiments with scientists and cooperating with water management authorities. In the environmental sciences, its potential has begun to be explored in the past decades and many studies on the applicability to water resources have emerged. Citizen Observatories are at the core of several EU-funded projects such as WeSenseIt, GroundTruth, GroundTruth 2.0 and SCENT (Smart Toolbox for Engaging Citizens into a People-Centric Observation Web) that already resulted in valuable contributions to the field. Buytaert et al. (2014) has already reviewed the role of citizen science in hydrology. The work presented here aims to complement it, reporting and discussing the use of citizen science for modelling the hydrodynamics of floods in a variety of studies. Additionally, it highlights the challenges that lie ahead to utilize more fully the citizen science potential contribution. In this work, focus is given to each component of hydrodynamic models: water level, velocity, flood extent, roughness and topography. It is addressed how citizens have been contributing to each aspect, mainly considering citizens as sensors and citizens as data interpreters. We consider to which kind of model (1D or 2D) the discussed approaches contribute and what their limitations and potential uses are. We found that although certain mechanisms are well established (e.g. the use of Volunteer Geographic Information for soft validation of land-cover and land-use maps), the applications in a modelling context are rather modest. Also, most studies involving models are limited to replacing traditional data with citizen data. We recommend that citizen science continue to be explored in modelling frameworks, in different case studies, taking advantage of the discussed mechanisms and of new sensor technologies
Hydrodynamical models of supernova SN 1987 A in the LMC
International Nuclear Information System (INIS)
Grassberg, E.K.; Imshennik, V.S.; Nadezhin, D.K.; Utrobin, V.P.
1987-01-01
It is shown that the properties of SN 1987A in LMC can be described well by hydrodynamical models of explosions of compact massive stars. In accordance with these models, the mass of the expelled envelope the presupernova radius and the total energy of explosion are evaluated for SN 1987A to be ∼ 16M Sun , ∼ 30R Sun , and ∼ 3.10 51 erg, respectively. The progenitor of supernova remnant Cas A may be considered as the prototype to the SN 1987A in our own Galaxy. In other galaxies, this subtype of supernovae can be represented by SN 1948B in NGC6946. If energy of explosion transfers from collapsed core of the star to the envelope within timescale less than 1 hour, then delay Δt ∼ 3 hours between the neutrino pulse and the steep rise of optical luminosity of SN 1987A does not contradict with scenario of explosions of compact massive stars
MEP parabolic hydrodynamical model for holes in silicon semiconductors
International Nuclear Information System (INIS)
Mascali, G.; Romano, V.; Sellier, J. M.
2005-01-01
Consistent hydrodynamical models for electron transport in semi-conductors, free of any fitting parameter, have been formulated on the basis of the maximum entropy principle in Continuum Mech. Thermodyn., 11 (1999) 307, 12 (2000) 31 for silicon and in Continuum Mech. Thermodyn., 14 (2002) 405 for GaAs. In this paper we use the same approach for studying the hole transport in Si, by considering a parabolic approximation for the valence energy band. Scattering of holes with non-polar optical phonons, acoustic phonons and impurities have been taken into account. On the basis of these results, a limiting energy-transport model and an explicit expression for the low field hole mobility have been obtained. The high field mobility is also analyzed by taking into account the influence of impurities
Mathematical modeling and hydrodynamics of Electrochemical deburring process
Prabhu, Satisha; Abhishek Kumar, K., Dr
2018-04-01
The electrochemical deburring (ECD) is a variation of electrochemical machining is considered as one of the efficient methods for deburring of intersecting features and internal parts. Since manual deburring costs are comparatively high one can potentially use this method in both batch production and flow production. The other advantage of this process is that time of deburring as is on the order of seconds as compared to other methods. In this paper, the mathematical modeling of Electrochemical deburring is analysed from its deburring time and base metal removal point of view. Simultaneously material removal rate is affected by electrolyte temperature and bubble formation. The mathematical model and hydrodynamics of the process throw limelight upon optimum velocity calculations which can be theoretically determined. The analysis can be the powerful tool for prediction of the above-mentioned parameters by experimentation.
Proton nucleus collisions in the Landau hydrodynamical model
International Nuclear Information System (INIS)
Andersson, B.
1976-01-01
The dependence upon energy and the atomic number A for the multiplicities and the angular distributions of the relativistic secondaries is computed according to the hydrodynamic model for proton-nucleus collisions. Some different ways of converting the dependence upon tunnellength in nuclear matter into A dependence are discussed and a phenomenological model employed to exhibit the correlations to the fragmentation of the nucleus. The treatment is valid for arbitrary values of the velocity of sound c 0 in nuclear matter inside the range 0.2 0 0 around c 0 approximately 0.5 is preferred in a comparison to the presently available experimental data. This is the same range of values of the parameter for which the best agreement between theory and experiment occurs in the ISR range. (Auth.)
A shock absorber model for structure-borne noise analyses
Benaziz, Marouane; Nacivet, Samuel; Thouverez, Fabrice
2015-08-01
Shock absorbers are often responsible for undesirable structure-borne noise in cars. The early numerical prediction of this noise in the automobile development process can save time and money and yet remains a challenge for industry. In this paper, a new approach to predicting shock absorber structure-borne noise is proposed; it consists in modelling the shock absorber and including the main nonlinear phenomena responsible for discontinuities in the response. The model set forth herein features: compressible fluid behaviour, nonlinear flow rate-pressure relations, valve mechanical equations and rubber mounts. The piston, base valve and complete shock absorber model are compared with experimental results. Sensitivity of the shock absorber response is evaluated and the most important parameters are classified. The response envelope is also computed. This shock absorber model is able to accurately reproduce local nonlinear phenomena and improves our state of knowledge on potential noise sources within the shock absorber.
A hydrodynamic model for granular material flows including segregation effects
Gilberg, Dominik; Klar, Axel; Steiner, Konrad
2017-06-01
The simulation of granular flows including segregation effects in large industrial processes using particle methods is accurate, but very time-consuming. To overcome the long computation times a macroscopic model is a natural choice. Therefore, we couple a mixture theory based segregation model to a hydrodynamic model of Navier-Stokes-type, describing the flow behavior of the granular material. The granular flow model is a hybrid model derived from kinetic theory and a soil mechanical approach to cover the regime of fast dilute flow, as well as slow dense flow, where the density of the granular material is close to the maximum packing density. Originally, the segregation model has been formulated by Thornton and Gray for idealized avalanches. It is modified and adapted to be in the preferred form for the coupling. In the final coupled model the segregation process depends on the local state of the granular system. On the other hand, the granular system changes as differently mixed regions of the granular material differ i.e. in the packing density. For the modeling process the focus lies on dry granular material flows of two particle types differing only in size but can be easily extended to arbitrary granular mixtures of different particle size and density. To solve the coupled system a finite volume approach is used. To test the model the rotational mixing of small and large particles in a tumbler is simulated.
Numerical modelling of extreme waves by Smoothed Particle Hydrodynamics
Directory of Open Access Journals (Sweden)
M. H. Dao
2011-02-01
Full Text Available The impact of extreme/rogue waves can lead to serious damage of vessels as well as marine and coastal structures. Such extreme waves in deep water are characterized by steep wave fronts and an energetic wave crest. The process of wave breaking is highly complex and, apart from the general knowledge that impact loadings are highly impulsive, the dynamics of the breaking and impact are still poorly understood. Using an advanced numerical method, the Smoothed Particle Hydrodynamics enhanced with parallel computing is able to reproduce well the extreme waves and their breaking process. Once the waves and their breaking process are modelled successfully, the dynamics of the breaking and the characteristics of their impact on offshore structures could be studied. The computational methodology and numerical results are presented in this paper.
Data Assimilation in Hydrodynamic Models of Continental Shelf Seas
DEFF Research Database (Denmark)
Sørensen, Jacob Viborg Tornfeldt
2004-01-01
. Assimilation of sea surface temperature and parameter estimation in hydrodynamic models are also considered. The main focus has been on the development of robust and efficient techniques applicable in real operational settings. The applied assimilation techniques all use a Kalman filter approach. They consist....... The assimilation schemes used in this work are primarily based on two ensemble based schemes, the Ensemble Kalman Filter and the Reduced Rank Square Root Kalman Filter. In order to investigate the applicability of these and derived schemes, the sensitivity to filter parameters, nonlinearity and bias is examined...... in artificial tests. Approximate schemes, which are theoretically presented as using regularised Kalman gains, are introduced and successfully applied in artificial as well real case scenarios. Particularly, distant dependent and slowly time varying or constant Kalman gains are shown to possess good hindcast...
Collisionless Electrostatic Shock Modeling and Simulation
2016-10-21
equations with piston -like boundary conditions gives a solution for the shock behavior. • Assumes cold upstream ions, therefore neglecting shock...temperature ratio (>10) – Wave Train Wavelength – Shock-Front Mach Number – Reflected Ion Beam Velocity Gathering Experiment Data – Double Plasma Device...experimental shock data. • Inconsistencies in published 1969 double -plasma device data hampered validation. Future Work: Extension to Moderately
Hydrodynamics of Bubble Columns: Turbulence and Population Balance Model
Directory of Open Access Journals (Sweden)
Camila Braga Vieira
2018-03-01
Full Text Available This paper presents an in-depth numerical analysis on the hydrodynamics of a bubble column. As in previous works on the subject, the focus here is on three important parameters characterizing the flow: interfacial forces, turbulence and inlet superficial Gas Velocity (UG. The bubble size distribution is taken into account by the use of the Quadrature Method of Moments (QMOM model in a two-phase Euler-Euler approach using the open-source Computational Fluid Dynamics (CFD code OpenFOAM (Open Field Operation and Manipulation. The interfacial forces accounted for in all the simulations presented here are drag, lift and virtual mass. For the turbulence analysis in the water phase, three versions of the Reynolds Averaged Navier-Stokes (RANS k-ε turbulence model are examined: namely, the standard, modified and mixture variants. The lift force proves to be of major importance for a trustworthy prediction of the gas volume fraction profiles for all the (superficial gas velocities tested. Concerning the turbulence, the mixture k-ε model is seen to provide higher values of the turbulent kinetic energy dissipation rate in comparison to the other models, and this clearly affects the prediction of the gas volume fraction in the bulk region, and the bubble-size distribution. In general, the modified k-ε model proves to be a good compromise between modeling simplicity and accuracy in the study of bubble columns of the kind undertaken here.
Hoch, J.M.; Neal, Jeffrey; Baart, Fedor; van Beek, L.P.H.; Winsemius, Hessel; Bates, Paul; Bierkens, M.F.P.
2017-01-01
We here present GLOFRIM, a globally applicable computational framework for integrated hydrological–hydrodynamic modelling. GLOFRIM facilitates spatially explicit coupling of hydrodynamic and hydrologic models and caters for an ensemble of models to be coupled. It currently encompasses the global
International Nuclear Information System (INIS)
Cao, Duc; Moses, Gregory; Delettrez, Jacques
2015-01-01
An implicit, non-local thermal conduction algorithm based on the algorithm developed by Schurtz, Nicolai, and Busquet (SNB) [Schurtz et al., Phys. Plasmas 7, 4238 (2000)] for non-local electron transport is presented and has been implemented in the radiation-hydrodynamics code DRACO. To study the model's effect on DRACO's predictive capability, simulations of shot 60 303 from OMEGA are completed using the iSNB model, and the computed shock speed vs. time is compared to experiment. Temperature outputs from the iSNB model are compared with the non-local transport model of Goncharov et al. [Phys. Plasmas 13, 012702 (2006)]. Effects on adiabat are also examined in a polar drive surrogate simulation. Results show that the iSNB model is not only capable of flux-limitation but also preheat prediction while remaining numerically robust and sacrificing little computational speed. Additionally, the results provide strong incentive to further modify key parameters within the SNB theory, namely, the newly introduced non-local mean free path. This research was supported by the Laboratory for Laser Energetics of the University of Rochester
Energy Technology Data Exchange (ETDEWEB)
Cao, Duc; Moses, Gregory [University of Wisconsin—Madison, 1500 Engineering Drive, Madison, Wisconsin 53706 (United States); Delettrez, Jacques [Laboratory for Laser Energetics of the University of Rochester, 250 East River Road, Rochester, New York 14623 (United States)
2015-08-15
An implicit, non-local thermal conduction algorithm based on the algorithm developed by Schurtz, Nicolai, and Busquet (SNB) [Schurtz et al., Phys. Plasmas 7, 4238 (2000)] for non-local electron transport is presented and has been implemented in the radiation-hydrodynamics code DRACO. To study the model's effect on DRACO's predictive capability, simulations of shot 60 303 from OMEGA are completed using the iSNB model, and the computed shock speed vs. time is compared to experiment. Temperature outputs from the iSNB model are compared with the non-local transport model of Goncharov et al. [Phys. Plasmas 13, 012702 (2006)]. Effects on adiabat are also examined in a polar drive surrogate simulation. Results show that the iSNB model is not only capable of flux-limitation but also preheat prediction while remaining numerically robust and sacrificing little computational speed. Additionally, the results provide strong incentive to further modify key parameters within the SNB theory, namely, the newly introduced non-local mean free path. This research was supported by the Laboratory for Laser Energetics of the University of Rochester.
Cao, Duc; Moses, Gregory; Delettrez, Jacques
2015-08-01
An implicit, non-local thermal conduction algorithm based on the algorithm developed by Schurtz, Nicolai, and Busquet (SNB) [Schurtz et al., Phys. Plasmas 7, 4238 (2000)] for non-local electron transport is presented and has been implemented in the radiation-hydrodynamics code DRACO. To study the model's effect on DRACO's predictive capability, simulations of shot 60 303 from OMEGA are completed using the iSNB model, and the computed shock speed vs. time is compared to experiment. Temperature outputs from the iSNB model are compared with the non-local transport model of Goncharov et al. [Phys. Plasmas 13, 012702 (2006)]. Effects on adiabat are also examined in a polar drive surrogate simulation. Results show that the iSNB model is not only capable of flux-limitation but also preheat prediction while remaining numerically robust and sacrificing little computational speed. Additionally, the results provide strong incentive to further modify key parameters within the SNB theory, namely, the newly introduced non-local mean free path. This research was supported by the Laboratory for Laser Energetics of the University of Rochester.
Simulations of Model Microswimmers with Fully Resolved Hydrodynamics
Oyama, Norihiro; Molina, John J.; Yamamoto, Ryoichi
2017-10-01
Swimming microorganisms, which include bacteria, algae, and spermatozoa, play a fundamental role in most biological processes. These swimmers are a special type of active particle, that continuously convert local energy into propulsive forces, thereby allowing them to move through their surrounding fluid medium. While the size, shape, and propulsion mechanism vary from one organism to the next, they share certain general characteristics: they exhibit force-free motion and they swim at a small Reynolds number. To study the dynamics of such systems, we use the squirmer model, which provides an ideal representation of swimmers as spheroidal particles that propel owing to a modified boundary condition at their surface. We have considered the single-particle and many-particle dynamics of swimmers in bulk and confined systems using the smoothed profile method, which allows us to efficiently solve the coupled particle-fluid problem. For the single-particle dynamics, we studied the diffusive behavior caused by the swimming of the particles. At short-time scales, the diffusion is caused by the hydrodynamic interactions, whereas at long-time scales, it is determined by the particle-particle collisions. Thus, the short-time diffusion will be the same for both swimmers and inert tracer particles. We then investigated the dynamics of confined microswimmers using cylindrical and parallel-plate confining walls. For the cylindrical confinement, we find evidence of an order/disorder phase transition which depends on the specific type of swimmers and the size of the cylinder. Under parallel-plane walls, some swimmers exhibit wavelike modes, which lead to traveling density waves that bounce back and forth between the walls. From an analysis of the bulk systems, we can show that this wavelike motion can be understood as a pseudoacoustic mode and is a consequence of the intrinsic swimming properties of the particles. The results presented here, together with the simulation method that
Hydrodynamics beyond Navier-Stokes: the slip flow model.
Yudistiawan, Wahyu P; Ansumali, Santosh; Karlin, Iliya V
2008-07-01
Recently, analytical solutions for the nonlinear Couette flow demonstrated the relevance of the lattice Boltzmann (LB) models to hydrodynamics beyond the continuum limit [S. Ansumali, Phys. Rev. Lett. 98, 124502 (2007)]. In this paper, we present a systematic study of the simplest LB kinetic equation-the nine-bit model in two dimensions--in order to quantify it as a slip flow approximation. Details of the aforementioned analytical solution are presented, and results are extended to include a general shear- and force-driven unidirectional flow in confined geometry. Exact solutions for the velocity, as well as for pertinent higher-order moments of the distribution functions, are obtained in both Couette and Poiseuille steady-state flows for all values of rarefaction parameter (Knudsen number). Results are compared with the slip flow solution by Cercignani, and a good quantitative agreement is found for both flow situations. Thus, the standard nine-bit LB model is characterized as a valid and self-consistent slip flow model for simulations beyond the Navier-Stokes approximation.
Hydrodynamic modeling of petroleum reservoirs using simulator MUFITS
Afanasyev, Andrey
2015-04-01
MUFITS is new noncommercial software for numerical modeling of subsurface processes in various applications (www.mufits.imec.msu.ru). To this point, the simulator was used for modeling nonisothermal flows in geothermal reservoirs and for modeling underground carbon dioxide storage. In this work, we present recent extension of the code to petroleum reservoirs. The simulator can be applied in conventional black oil modeling, but it also utilizes a more complicated models for volatile oil and gas condensate reservoirs as well as for oil rim fields. We give a brief overview of the code by providing the description of internal representation of reservoir models, which are constructed of grid blocks, interfaces, stock tanks as well as of pipe segments and pipe junctions for modeling wells and surface networks. For conventional black oil approach, we present the simulation results for SPE comparative tests. We propose an accelerated compositional modeling method for sub- and supercritical flows subjected to various phase equilibria, particularly to three-phase equilibria of vapour-liquid-liquid type. The method is based on the calculation of the thermodynamic potential of reservoir fluid as a function of pressure, total enthalpy and total composition and storing its values as a spline table, which is used in hydrodynamic simulation for accelerated PVT properties prediction. We provide the description of both the spline calculation procedure and the flashing algorithm. We evaluate the thermodynamic potential for a mixture of two pseudo-components modeling the heavy and light hydrocarbon fractions. We develop a technique for converting black oil PVT tables to the potential, which can be used for in-situ hydrocarbons multiphase equilibria prediction under sub- and supercritical conditions, particularly, in gas condensate and volatile oil reservoirs. We simulate recovery from a reservoir subject to near-critical initial conditions for hydrocarbon mixture. We acknowledge
Modelling and validation of electromechanical shock absorbers
Tonoli, Andrea; Amati, Nicola; Girardello Detoni, Joaquim; Galluzzi, Renato; Gasparin, Enrico
2013-08-01
Electromechanical vehicle suspension systems represent a promising substitute to conventional hydraulic solutions. However, the design of electromechanical devices that are able to supply high damping forces without exceeding geometric dimension and mass constraints is a difficult task. All these challenges meet in off-road vehicle suspension systems, where the power density of the dampers is a crucial parameter. In this context, the present paper outlines a particular shock absorber configuration where a suitable electric machine and a transmission mechanism are utilised to meet off-road vehicle requirements. A dynamic model is used to represent the device. Subsequently, experimental tests are performed on an actual prototype to verify the functionality of the damper and validate the proposed model.
Hydrodynamic Modeling of Nokoué Lake in Benin
Directory of Open Access Journals (Sweden)
Josué Zandagba
2016-12-01
Full Text Available Nokoué Lake is a complex ecosystem, the understanding of which requires control of physical processes that have occurred. For this, the Surface Water Modeling System (SMS hydrodynamic model was calibrated and validated on the water depth data. The results of these simulations show a good match between the simulated and observed data for bottom roughness and turbulent exchange coefficients, of 0.02 m−1/3·s and 20 m2/s respectively. Once the ability of the model to simulate the hydrodynamics of the lake is testified, the model is used to simulate water surface elevation, exchanged flows and velocities. The simulation shows that the tidal amplitude is maximum at the inlet of the channel and decreases gradually from the inlet towards the lagoon’s main body. The propagation of the tidal wave is characterized by the dephasing and the flattening of the amplitude tide, which increases as we move away from the channel. This dephasing is characterized by a high and low tides delay of about 1 or 4 h and also depends on the tide amplitude and location. The velocities inside the lake are very low and do not exceed 0.03 m/s. The highest are obtained at the entrance of the channel. In a flood period, in contrast with the low-water period, incoming flows are higher than outflows, reinforced by the amplitude of the tide. An average renewal time of the lake has been estimated and corresponds during a flood period to 30 days for an average amplitude tide and 26.3 days on a high amplitude tide. In a low water period it is 40.2 days for an average amplitude tide and 30 days for a high amplitude tide. From the results obtained, several measures must be taken into account for the rational management of the lake water resources. These include a dam construction at the lake upstream, to control the river flows, and the dredging of the channel to facilitate exchanges with the sea.
Hydrodynamic modeling of tsunamis from the Currituck landslide
Geist, E.L.; Lynett, P.J.; Chaytor, J.D.
2009-01-01
Tsunami generation from the Currituck landslide offshore North Carolina and propagation of waves toward the U.S. coastline are modeled based on recent geotechnical analysis of slide movement. A long and intermediate wave modeling package (COULWAVE) based on the non-linear Boussinesq equations are used to simulate the tsunami. This model includes procedures to incorporate bottom friction, wave breaking, and overland flow during runup. Potential tsunamis generated from the Currituck landslide are analyzed using four approaches: (1) tsunami wave history is calculated from several different scenarios indicated by geotechnical stability and mobility analyses; (2) a sensitivity analysis is conducted to determine the effects of both landslide failure duration during generation and bottom friction along the continental shelf during propagation; (3) wave history is calculated over a regional area to determine the propagation of energy oblique to the slide axis; and (4) a high-resolution 1D model is developed to accurately model wave breaking and the combined influence of nonlinearity and dispersion during nearshore propagation and runup. The primary source parameter that affects tsunami severity for this case study is landslide volume, with failure duration having a secondary influence. Bottom friction during propagation across the continental shelf has a strong influence on the attenuation of the tsunami during propagation. The high-resolution 1D model also indicates that the tsunami undergoes nonlinear fission prior to wave breaking, generating independent, short-period waves. Wave breaking occurs approximately 40-50??km offshore where a tsunami bore is formed that persists during runup. These analyses illustrate the complex nature of landslide tsunamis, necessitating the use of detailed landslide stability/mobility models and higher-order hydrodynamic models to determine their hazard.
Hydrodynamics Modeling of Khung Krabaen Lagoon, Chanthaburi Province, Thailand
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Tanuspong Pokavanich
2018-01-01
Full Text Available Khung Krabaen Lagoon (KKBL is a small low-inflow water body. There are vast areas of tidal flat occupied nearly 60% of the lagoon that host some of the most productive seagrass habitats in the region. The lagoon is surrounded by mangrove forest and intensive shrimp farms behind it. The KKBL was used as an intake and recipient water for the farms. However due some shrimp disease epidemics and possibly deteriorated water quality, the farms are now taking the intake water from the outer sea through very expensive (to construct and to maintain irrigation system. Objective of this study is to investigate the KKBL’s hydrodynamics using a numerical simulation model validated with measured data. The simulation model was setup two-dimensionally based on the Delft3D model. Results suggested that water currents inside, at the mouth and at the outer sea of the lagoon are mainly governed by tide and wind. Offshore of the lagoon, there are strong tidal currents flowing along northwest and southeast direction. The tidal currents flow into the lagoon through its mouth before dispersion rapidly inside the lagoon. Mean circulation largely varied seasonally and had direct correlations outer sea seasonal mean currents and the monsoons.
Computational Modeling of Hydrodynamics and Scour around Underwater Munitions
Liu, X.; Xu, Y.
2017-12-01
Munitions deposited in water bodies are a big threat to human health, safety, and environment. It is thus imperative to predict the motion and the resting status of the underwater munitions. A multitude of physical processes are involved, which include turbulent flows, sediment transport, granular material mechanics, 6 degree-of-freedom motion of the munition, and potential liquefaction. A clear understanding of this unique physical setting is currently lacking. Consequently, it is extremely hard to make reliable predictions. In this work, we present the computational modeling of two importance processes, i.e., hydrodynamics and scour, around munition objects. Other physical processes are also considered in our comprehensive model. However, they are not shown in this talk. To properly model the dynamics of the deforming bed and the motion of the object, an immersed boundary method is implemented in the open source CFD package OpenFOAM. Fixed bed and scour cases are simulated and compared with laboratory experiments. The future work of this project will implement the coupling between all the physical processes.
Crossflow-induced vibrations of tube banks: hydrodynamic forces and mathematical models
International Nuclear Information System (INIS)
Chen, S.S.
1977-01-01
The objective of this paper is to present a method of analysis for the hydrodynamic forces acting on tube banks and a mathematical model for multiple tubes and multiple excitation mechanisms incorporating tube/fluid coupling. The hydrodynamic forces acting on tube banks are analyzed using the two dimensional potential flow theory
Hydromechanics of Wind-Assisted Ship Propulsion : Modeling of Hydrodynamic Sideforce
van der Kolk, N.J.
2016-01-01
This paper deals with the hydrodynamic sideforce production of a wind-assisted ship. The subject is introduced, both in physical terms, and with an overview of current and recent work. The importance of the hydrodynamic sideforce is established, before classical models are reviewed. Finally, the
Colloidal suspensions hydrodynamic retention mechanisms in model porous media
International Nuclear Information System (INIS)
Salehi, N.
1996-01-01
This study deals with the retention mechanisms of colloidal particles in porous media flows, and the subsequent reduction in permeability in the case of stable and non adsorbing colloids. It combines experimental results and modelling. This study has been realised with stable dispersion of monodispersed carboxylate polystyrene latexes negatively charged injected through negatively charged polycarbonate membranes having mono-sized cylindrical pores. The mean particle diameter is smaller than the mean pore diameter. Both batch and flow experiments in Nuclepore membranes have been done. The results of batch experiments have proved no adsorption of the colloidal latex particles on the surface of the Nuclepore membranes without flow at low salinity. In flow experiments at low particle concentration, only deposition on the upstream side of the membrane have been induced by hydrodynamic forces even for non adsorbing particles without creating any permeability reduction. The retention levels are zero at low and high Peclet numbers with a maximum at intermediate values. Partial plugging was observed at higher colloid concentration even at low salinity without any upstream surface deposition. The modelling of plugging processes is achieved by considering the particle concentration, fluid rate and ratio between the mean pore diameter and the mean particle diameter. This study can be particularly useful in the fields of water treatment and of restoration of lands following radioactive contamination. (author). 96 refs., 99 figs., 29 tabs
Computational models of the hydrodynamics of fractured-porous media
International Nuclear Information System (INIS)
Grandi, G.M.
1989-01-01
The prediction of the flow pattern in fractured-porous media has great importance in the assessment of the local thermohydrological effects of the siting of a nuclear waste repository, among many other technological applications. Computational models must be used due to the complexity of the different phenomena involved which restricts the use of analytical techniques. A new numerical method, based on the boundary-fitted finite-difference technique, is presented in this thesis. The boundaries are external (the boundary of the physical domain), and internal (which correspond to the fracture network). The inclusion of the discrete fracture representation in the volume that represents the porous medium is the difference between the usual approach and the present one. The numerical model has been used in the prediction of the flow pattern in several internationally recognized verification cases and to hypothetical problems of our interest. The results obtained proved that the numerical approach considered gives accurate and reliable predictions of the hydrodynamics of fractured-porous media, allowing its use for the above mentioned studies. (Author) [es
On a Stochastic Failure Model under Random Shocks
Cha, Ji Hwan
2013-02-01
In most conventional settings, the events caused by an external shock are initiated at the moments of its occurrence. In this paper, we study a new classes of shock model, where each shock from a nonhomogeneous Poisson processes can trigger a failure of a system not immediately, as in classical extreme shock models, but with delay of some random time. We derive the corresponding survival and failure rate functions. Furthermore, we study the limiting behaviour of the failure rate function where it is applicable.
RADIATION HYDRODYNAMICS MODELS OF THE INNER RIM IN PROTOPLANETARY DISKS
Energy Technology Data Exchange (ETDEWEB)
Flock, M.; Turner, N. J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Fromang, S. [Laboratoire AIM, CEA/DSM-CNRS-Université Paris 7, Irfu/Service d’Astrophysique, CEA-Saclay, F-91191 Gif-sur-Yvette (France); Benisty, M., E-mail: mflock@caltech.edu [Université Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble (France)
2016-08-20
Many stars host planets orbiting within a few astronomical units (AU). The occurrence rate and distributions of masses and orbits vary greatly with the host star’s mass. These close planets’ origins are a mystery that motivates investigating protoplanetary disks’ central regions. A key factor governing the conditions near the star is the silicate sublimation front, which largely determines where the starlight is absorbed, and which is often called the inner rim. We present the first radiation hydrodynamical modeling of the sublimation front in the disks around the young intermediate-mass stars called Herbig Ae stars. The models are axisymmetric and include starlight heating; silicate grains sublimating and condensing to equilibrium at the local, time-dependent temperature and density; and accretion stresses parameterizing the results of MHD magnetorotational turbulence models. The results compare well with radiation hydrostatic solutions and prove to be dynamically stable. Passing the model disks into Monte Carlo radiative transfer calculations, we show that the models satisfy observational constraints on the inner rim’s location. A small optically thin halo of hot dust naturally arises between the inner rim and the star. The inner rim has a substantial radial extent, corresponding to several disk scale heights. While the front’s overall position varies with the stellar luminosity, its radial extent depends on the mass accretion rate. A pressure maximum develops near the location of thermal ionization at temperatures of about 1000 K. The pressure maximum is capable of halting solid pebbles’ radial drift and concentrating them in a zone where temperatures are sufficiently high for annealing to form crystalline silicates.
out-of-n systems with shock model
African Journals Online (AJOL)
distributed. Sarhan, A.M. and Abouammoh (2000) used the shock model to derive the re- liability function of k-out-of-n systems with nonindependent and nonidentical components. They assumed that a system is subjected to n + m independent types of shocks. Liu et al. (2008) proposed a model to evaluate the reliability ...
Maximum entropy principle and hydrodynamic models in statistical mechanics
International Nuclear Information System (INIS)
Trovato, M.; Reggiani, L.
2012-01-01
This review presents the state of the art of the maximum entropy principle (MEP) in its classical and quantum (QMEP) formulation. Within the classical MEP we overview a general theory able to provide, in a dynamical context, the macroscopic relevant variables for carrier transport in the presence of electric fields of arbitrary strength. For the macroscopic variables the linearized maximum entropy approach is developed including full-band effects within a total energy scheme. Under spatially homogeneous conditions, we construct a closed set of hydrodynamic equations for the small-signal (dynamic) response of the macroscopic variables. The coupling between the driving field and the energy dissipation is analyzed quantitatively by using an arbitrary number of moments of the distribution function. Analogously, the theoretical approach is applied to many one-dimensional n + nn + submicron Si structures by using different band structure models, different doping profiles, different applied biases and is validated by comparing numerical calculations with ensemble Monte Carlo simulations and with available experimental data. Within the quantum MEP we introduce a quantum entropy functional of the reduced density matrix, the principle of quantum maximum entropy is then asserted as fundamental principle of quantum statistical mechanics. Accordingly, we have developed a comprehensive theoretical formalism to construct rigorously a closed quantum hydrodynamic transport within a Wigner function approach. The theory is formulated both in thermodynamic equilibrium and nonequilibrium conditions, and the quantum contributions are obtained by only assuming that the Lagrange multipliers can be expanded in powers of ħ 2 , being ħ the reduced Planck constant. In particular, by using an arbitrary number of moments, we prove that: i) on a macroscopic scale all nonlocal effects, compatible with the uncertainty principle, are imputable to high-order spatial derivatives both of the
Visualization and modeling of the hydrodynamics of an impinging microjet.
Bitziou, Eleni; Rudd, Nicola C; Edwards, Martin A; Unwin, Patrick R
2006-03-01
The use of fluorescence confocal laser scanning microscopy (CLSM) for flow visualization is described, with a focus on elucidating the pattern of flow in the microjet electrode (MJE). The MJE employs a nozzle, formed from a fine glass capillary, with an inner diameter of approximately 100 microm, to direct solution at an electrode surface, using high velocity but at moderate volume flow rates. For CLSM visualization, the jetted solution contains a fluorescent probe, fluorescein at high pH, which flows into a solution buffered at low pH, where the fluorescence is extinguished, thereby highlighting the flow field of the impinging microjet. The morphology of the microjet and the hydrodynamic boundary layer are shown to be highly sensitive to the volume flow rate, with a collimated jet and thin boundary layer formed at the faster flow rates (approximately 1 cm(3) min(-1)). In contrast, at lower flow rates and for relatively large substrates, an unusual recirculation zone is observed experimentally for the first time. This effect can be eliminated by employing small substrates. The experimental observations have been quantified through numerical solution of the Navier-Stokes equations of continuity and momentum balance. The new insights provided by CLSM imaging demonstrate that flow in the MJE, and impinging jets in general, are more complex than predicted by classical models but are well-defined and quantifiable.
On the Effects of Viscosity on the Shock Waves for a Hydrodynamical Case—Part I: Basic Mechanism
Directory of Open Access Journals (Sweden)
Huseyin Cavus
2013-01-01
Full Text Available The interaction of shock waves with viscosity is one of the central problems in the supersonic regime of compressible fluid flow. In this work, numerical solutions of unmagnetised fluid equations, with the viscous stress tensor, are investigated for a one-dimensional shock wave. In the algorithm developed the viscous stress terms are expressed in terms of the relevant Reynolds number. The algorithm concentrated on the compression rate, the entropy change, pressures, and Mach number ratios across the shock wave. The behaviour of solutions is obtained for the Reynolds and Mach numbers defining the medium and shock wave in the supersonic limits.
Hydrodynamic model of the open-pit mine “Buvač” (Republic of Srpska
Directory of Open Access Journals (Sweden)
Papić Petar
2013-09-01
Full Text Available Projecting of the dewatering system of the open-pit mine “Buvač” (Republic of Srpska, Bosnia and Herzegovina is based on the use of hydrodynamic model of groundwater regime. Creating the hydrodynamic model of the open-pit mine “Buvač“ was made in phases, which began by basic interpretation of collected data, along with schematization of the groundwater flow and flow conditions, and finally, forming and calibration of model. Hydrodynamic model was created as multilayer model with eight layers. Calibration of the hydrodynamic model is the starting point for making prognosis calculation in order to create the most optimal system of open-pit mine protection from groundwater. The results of model calibration indicated that the rivers Gomjenica and Bistrica, precipitation and inflow from karstified rocks are the primary sources of recharge of the limonite ore body “Buvač”.
Freytag, B.; Liljegren, S.; Höfner, S.
2017-04-01
Context. Observations of asymptotic giant branch (AGB) stars with increasing spatial resolution reveal new layers of complexity of atmospheric processes on a variety of scales. Aims: To analyze the physical mechanisms that cause asymmetries and surface structures in observed images, we use detailed 3D dynamical simulations of AGB stars; these simulations self-consistently describe convection and pulsations. Methods: We used the CO5BOLD radiation-hydrodynamics code to produce an exploratory grid of global "star-in-a-box" models of the outer convective envelope and the inner atmosphere of AGB stars to study convection, pulsations, and shock waves and their dependence on stellar and numerical parameters. Results: The model dynamics are governed by the interaction of long-lasting giant convection cells, short-lived surface granules, and strong, radial, fundamental-mode pulsations. Radial pulsations and shorter wavelength, traveling, acoustic waves induce shocks on various scales in the atmosphere. Convection, waves, and shocks all contribute to the dynamical pressure and, thus, to an increase of the stellar radius and to a levitation of material into layers where dust can form. Consequently, the resulting relation of pulsation period and stellar radius is shifted toward larger radii compared to that of non-linear 1D models. The dependence of pulsation period on luminosity agrees well with observed relations. The interaction of the pulsation mode with the non-stationary convective flow causes occasional amplitude changes and phase shifts. The regularity of the pulsations decreases with decreasing gravity as the relative size of convection cells increases. The model stars do not have a well-defined surface. Instead, the light is emitted from a very extended inhomogeneous atmosphere with a complex dynamic pattern of high-contrast features. Conclusions: Our models self-consistently describe convection, convectively generated acoustic noise, fundamental-mode radial
Monitoring Mediterranean marine pollution using remote sensing and hydrodynamic modelling
La Loggia, Goffredo; Capodici, Fulvio; Ciraolo, Giuseppe; Drago, Aldo; Maltese, Antonino
2011-11-01
Human activities contaminate both coastal areas and open seas, even though impacts are different in terms of pollutants, ecosystems and recovery time. In particular, Mediterranean offshore pollution is mainly related to maritime transport of oil, accounting for 25% of the global maritime traffic and, during the last 25 years, for nearly 7% of the world oil accidents, thus causing serious biological impacts on both open sea and coastal zone habitats. This paper provides a general review of maritime pollution monitoring using integrated approaches of remote sensing and hydrodynamic modeling; focusing on the main results of the MAPRES (Marine pollution monitoring and detection by aerial surveillance and satellite images) research project on the synergistic use of remote sensing, forecasting, cleanup measures and environmental consequences. The paper also investigates techniques of oil spill detection using SAR images, presenting the first results of "Monitoring of marine pollution due to oil slick", a COSMO-SkyMed funded research project where X-band SAR constellation images provided by the Italian Space Agency are used. Finally, the prospect of using real time observations of marine surface conditions is presented through CALYPSO project (CALYPSO-HF Radar Monitoring System and Response against Marine Oil Spills in the Malta Channel), partly financed by the EU under the Operational Programme Italia-Malta 2007-2013. The project concerns the setting up of a permanent and fully operational HF radar observing system, capable of recording surface currents (in real-time with hourly updates) in the stretch of sea between Malta and Sicily. A combined use of collected data and numerical models, aims to optimize intervention and response in the case of marine oil spills.
HELOKA facility: thermo-hydrodynamic model and control
International Nuclear Information System (INIS)
Ghidersa, B.E.; Ihli, T.; Marchese, V.; Ionescu-Bujor, M.
2007-01-01
This paper presents the thermo-hydrodynamic model used to simulate the behaviour of the HELOKA (Helium Loop Karlsruhe) facility and describes the mechanism used to control various loop parameters. This test facility, which is under construction at the Forschungszentrum Karlsruhe (FZK), is designed for testing of various components for nuclear fusion such as the Helium-Cooled Pebble Bed blanket (HCPB) and the heliumcooled- divertor for the DEMO power reactor. Besides the individual testing of the blanket and divertor modules, the understanding of the behaviour of their cooling systems in conditions relevant for ITER operation is mandatory. An important aspect in the operation of these cooling loops is the accurate control, via feedback, of the flow parameters at the inlet of the test module. Understanding heat transfer and fluid flow phenomena during normal and transient operation of HELOKA is essential to ensure the adequacy of safety features. Systems analysis codes, such as RELAP5-3D, are suited to this task. However, the application of these models to HELOKA design must be later validated by experimental measurements, while the basic physical models have been proven for light water reactors. The control of the test section inlet parameters is one of the most important issues. In particular, the start-up phase, when the test section temperature is increased from ambient temperature up to 300 C, requires special attention. As a first step, the HELOKA open loop thermal transient was computed using the RELAP model. The data obtained have been used for the identification of the power-temperature transfer function needed to compute the parameters of the feedback controller (PID) using MATLAB and SIMULINK. An accurate control of the temperature during the start-up and flat top phases is achieved solely by controlling the heater power. The adopted solution reduces the harmonic distortions when operating at reduced power while keeping the investment cost low. This
Modeling Business Cycle with Financial Shocks Basing on Kaldor-Kalecki Model
Directory of Open Access Journals (Sweden)
Zhenghui Li
2017-04-01
Full Text Available The effects of financial factors on real business cycle is rising to one of the most popular discussions in the field of macro business cycle theory. The objective of this paper is to discuss the features of business cycle under financial shocks by quantitative technology. More precisely, we introduce financial shocks into the classical Kaldor-Kalecki business cycle model and study dynamics of the model. The shocks include external shock and internal shock, both of which are expressed as noises. The dynamics of the model can help us understand the effects of financial shocks on business cycle and improve our knowledge about financial business cycle. In the case of external shock, if the intensity of shock is less than some threshold value, the economic system behaves randomly periodically. If the intensity of shock is beyond the threshold value, the economic system will converge to a normalcy. In the case of internal shock, if the intensity of shock is less than some threshold value, the economic system behaves periodically as the case without shock. If the intensity of shock exceeds the threshold value, the economic system either behaves periodically or converges to a normalcy. It is uncertain. The case with both two kinds of shocks is more complicated. We find conditions of the intensities of shocks under which the economic system behaves randomly periodically or disorderly, or converges to normalcy. Discussions about the effects of financial shocks on the business cycle are presented.
Validation Hydrodynamic Models of Three Topological Models of Secondary Facultative Ponds
Aponte-Reyes Alxander
2014-01-01
A methodology was developed to analyze boundary conditions, the size of the mesh and the turbulence of a mathematical model of CFD, which could explain hydrodynamic behavior on facultative stabilization ponds, FSP, built to pilot scale: conventional pond, CP, baffled pond, BP, and baffled-mesh pond, BMP. Models dispersion studies were performed in field for validation, taking samples into and out of the FSP, the information was used to carry out CFD model simulations of the three topologies. ...
Modeling Hydrodynamic State of Oil and Gas Condensate Mixture in a Pipeline
Directory of Open Access Journals (Sweden)
Dudin Sergey
2016-01-01
Based on the developed model a calculation method was obtained which is used to analyze hydrodynamic state and composition of hydrocarbon mixture in each ith section of the pipeline when temperature-pressure and hydraulic conditions change.
Two-dimensional hydrodynamic and transport models were used to simulate tidal and subtidal circulation, residence times, and the longitudinal distributions of conservative constituents in New Bedford Harbor, Massachusetts, before and after a hurricane barrier was constructed. The...
Modeling multiscale evolution of numerous voids in shocked brittle material.
Yu, Yin; Wang, Wenqiang; He, Hongliang; Lu, Tiecheng
2014-04-01
The influence of the evolution of numerous voids on macroscopic properties of materials is a multiscale problem that challenges computational research. A shock-wave compression model for brittle material, which can obtain both microscopic evolution and macroscopic shock properties, was developed using discrete element methods (lattice model). Using a model interaction-parameter-mapping procedure, qualitative features, as well as trends in the calculated shock-wave profiles, are shown to agree with experimental results. The shock wave splits into an elastic wave and a deformation wave in porous brittle materials, indicating significant shock plasticity. Void collapses in the deformation wave were the natural reason for volume shrinkage and deformation. However, media slippage and rotation deformations indicated by complex vortex patterns composed of relative velocity vectors were also confirmed as an important source of shock plasticity. With increasing pressure, the contribution from slippage deformation to the final plastic strain increased. Porosity was found to determine the amplitude of the elastic wave; porosity and shock stress together determine propagation speed of the deformation wave, as well as stress and strain on the final equilibrium state. Thus, shock behaviors of porous brittle material can be systematically designed for specific applications.
Hydrodynamics of burst swimming fish larvae; a conceptual model approach
Verhagen, J.H.G.
2004-01-01
Burst swimming of fish larvae is analysed from a hydrodynamic point of view. A picture of the expected flow pattern is presented based on information in literature on unsteady-flow patterns around obstacles in the intermediate Reynolds number region. It is shown that the acceleration stage of burst
A model for radio emission from solar coronal shocks
Energy Technology Data Exchange (ETDEWEB)
Zhao, G. Q.; Chen, L.; Wu, D. J., E-mail: djwu@pmo.ac.cn [Purple Mountain Observatory, CAS, Nanjing 210008 (China)
2014-05-01
Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.
A model for radio emission from solar coronal shocks
International Nuclear Information System (INIS)
Zhao, G. Q.; Chen, L.; Wu, D. J.
2014-01-01
Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.
Calibration of Linked Hydrodynamic and Water Quality Model for Santa Margarita Lagoon
2016-07-01
was used to drive the transport and water quality kinetics for the simulation of 2007–2009. The sand berm, which controlled the opening/closure of...TECHNICAL REPORT 3015 July 2016 Calibration of Linked Hydrodynamic and Water Quality Model for Santa Margarita Lagoon Final Report Pei...Linked Hydrodynamic and Water Quality Model for Santa Margarita Lagoon Final Report Pei-Fang Wang Chuck Katz Ripan Barua SSC Pacific James
Acceleration mechanisms flares, magnetic reconnection and shock waves
International Nuclear Information System (INIS)
Colgate, S.A.
1979-01-01
Several mechanisms are briefly discussed for the acceleration of particles in the astrophysical environment. Included are hydrodynamic acceleration, spherically convergent shocks, shock and a density gradient, coherent electromagnetic acceleration, the flux tube origin, symmetries and instabilities, reconnection, galactic flares, intergalactic acceleration, stochastic acceleration, and astrophysical shocks. It is noted that the supernova shock wave models still depend critically on the presupernova star structure and the assumption of highly compact presupernova models for type I supernovae. 37 references
Critical review of membrane bioreactor models--part 2: hydrodynamic and integrated models.
Naessens, W; Maere, T; Ratkovich, N; Vedantam, S; Nopens, I
2012-10-01
Membrane bioreactor technology exists for a couple of decades, but has not yet overwhelmed the market due to some serious drawbacks of which operational cost due to fouling is the major contributor. Knowledge buildup and optimisation for such complex systems can heavily benefit from mathematical modelling. In this paper, the vast literature on hydrodynamic and integrated MBR modelling is critically reviewed. Hydrodynamic models are used at different scales and focus mainly on fouling and only little on system design/optimisation. Integrated models also focus on fouling although the ones including costs are leaning towards optimisation. Trends are discussed, knowledge gaps identified and interesting routes for further research suggested. Copyright © 2012 Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Krafft, G.A.; Mark, J.W.K.; Wang, T.S.F.
1983-01-01
In an earlier paper, closed hydrodynamic equations were derived with possible application to the simulation of beam plasmas relevant to designs of heavy ion accelerators for inertial confinement fusion energy applications. The closure equations involved a novel feature of anisotropic stresses even transverse to the beam. A related hydrodynamic model is used in this paper to examine further the boundaries of validity of such hydrodynamic approximations. It is also proposed as a useful tool to provide an economic means for searching the large parameter space relevant to three-dimensional stability problems involving coupling of longitudinal and transverse motions in the presence of wall impedance
Parker, L. N.; Zank, G. P.
2013-12-01
Successful forecasting of energetic particle events in space weather models require algorithms for correctly predicting the spectrum of ions accelerated from a background population of charged particles. We present preliminary results from a model that diffusively accelerates particles at multiple shocks. Our basic approach is related to box models (Protheroe and Stanev, 1998; Moraal and Axford, 1983; Ball and Kirk, 1992; Drury et al., 1999) in which a distribution of particles is diffusively accelerated inside the box while simultaneously experiencing decompression through adiabatic expansion and losses from the convection and diffusion of particles outside the box (Melrose and Pope, 1993; Zank et al., 2000). We adiabatically decompress the accelerated particle distribution between each shock by either the method explored in Melrose and Pope (1993) and Pope and Melrose (1994) or by the approach set forth in Zank et al. (2000) where we solve the transport equation by a method analogous to operator splitting. The second method incorporates the additional loss terms of convection and diffusion and allows for the use of a variable time between shocks. We use a maximum injection energy (Emax) appropriate for quasi-parallel and quasi-perpendicular shocks (Zank et al., 2000, 2006; Dosch and Shalchi, 2010) and provide a preliminary application of the diffusive acceleration of particles by multiple shocks with frequencies appropriate for solar maximum (i.e., a non-Markovian process).
Simulation of Tailrace Hydrodynamics Using Computational Fluid Dynamics Models
Energy Technology Data Exchange (ETDEWEB)
Cook, Christopher B.; Richmond, Marshall C.
2001-05-01
This report investigates the feasibility of using computational fluid dynamics (CFD) tools to investigate hydrodynamic flow fields surrounding the tailrace zone below large hydraulic structures. Previous and ongoing studies using CFD tools to simulate gradually varied flow with multiple constituents and forebay/intake hydrodynamics have shown that CFD tools can provide valuable information for hydraulic and biological evaluation of fish passage near hydraulic structures. These studies however are incapable of simulating the rapidly varying flow fields that involving breakup of the free-surface, such as those through and below high flow outfalls and spillways. Although the use of CFD tools for these types of flow are still an active area of research, initial applications discussed in this report show that these tools are capable of simulating the primary features of these highly transient flow fields.
Modeling of dynamically loaded hydrodynamic bearings at low Sommerfeld numbers
DEFF Research Database (Denmark)
Thomsen, Kim
Current state of the art within the wind industry dictates the use of conventional rolling element bearings for main bearings. As wind turbine generators increase in size and output, so does the size of the main bearings and accordingly also the cost and potential risk of failure modes. The cost...... and failure risk of rolling element bearings do, however, grow exponentially with the size. Therefore hydrodynamic bearings can prove to be a competitive alternative to the current practice of rolling element bearings and ultimately help reducing the cost and carbon footprint of renewable energy generation....... The challenging main bearing operation conditions in a wind turbine pose a demanding development task for the design of a hydrodynamic bearing. In general these conditions include operation at low Reynolds numbers with frequent start and stop at high loads as well as difficult operating conditions dictated...
Relativistic Shock Acceleration
International Nuclear Information System (INIS)
Duffy, P.; Downes, T.P.; Gallant, Y.A.; Kirk, J.G.
1999-01-01
In this paper we briefly review the basic theory of shock waves in relativistic hydrodynamics and magneto-hydrodynamics, emphasising some astrophysically interesting cases. We then present an overview of the theory of particle acceleration at such shocks describing the methods used to calculate the spectral indices of energetic particles. Recent results on acceleration at ultra-relativistic shocks are discussed. (author)
Geisbert, Jesse Stuart
2007-01-01
Buoyancy driven underwater gliders, which locomote by modulating their buoyancy and their attitude with moving mass actuators and inflatable bladders, are proving their worth as efficient long-distance, long-duration ocean sampling platforms. Gliders have the capability to travel thousands of kilometers without a need to stop or recharge. There is a need for the development of methods for hydrodynamic modeling. This thesis aims to determine the hydrodynamic parameters for the governing equat...
Bayesian Nonparametric Statistical Inference for Shock Models and Wear Processes.
1979-12-01
also note that the results in Section 2 do not depend on the support of F .) This shock model have been studied by Esary, Marshall and Proschan (1973...Barlow and Proschan (1975), among others. The analogy of the shock model in risk and acturial analysis has been given by BUhlmann (1970, Chapter 2... Mathematical Statistics, Vol. 4, pp. 894-906. Billingsley, P. (1968), CONVERGENCE OF PROBABILITY MEASURES, John Wiley, New York. BUhlmann, H. (1970
Activity-induced clustering in model dumbbell swimmers: the role of hydrodynamic interactions.
Furukawa, Akira; Marenduzzo, Davide; Cates, Michael E
2014-08-01
Using a fluid-particle dynamics approach, we numerically study the effects of hydrodynamic interactions on the collective dynamics of active suspensions within a simple model for bacterial motility: each microorganism is modeled as a stroke-averaged dumbbell swimmer with prescribed dipolar force pairs. Using both simulations and qualitative arguments, we show that, when the separation between swimmers is comparable to their size, the swimmers' motions are strongly affected by activity-induced hydrodynamic forces. To further understand these effects, we investigate semidilute suspensions of swimmers in the presence of thermal fluctuations. A direct comparison between simulations with and without hydrodynamic interactions shows these to enhance the dynamic clustering at a relatively small volume fraction; with our chosen model the key ingredient for this clustering behavior is hydrodynamic trapping of one swimmer by another, induced by the active forces. Furthermore, the density dependence of the motility (of both the translational and rotational motions) exhibits distinctly different behaviors with and without hydrodynamic interactions; we argue that this is linked to the clustering tendency. Our study illustrates the fact that hydrodynamic interactions not only affect kinetic pathways in active suspensions, but also cause major changes in their steady state properties.
A critical analysis of shock models for chondrule formation
Stammler, Sebastian M.; Dullemond, Cornelis P.
2014-11-01
In recent years many models of chondrule formation have been proposed. One of those models is the processing of dust in shock waves in protoplanetary disks. In this model, the dust and the chondrule precursors are overrun by shock waves, which heat them up by frictional heating and thermal exchange with the gas. In this paper we reanalyze the nebular shock model of chondrule formation and focus on the downstream boundary condition. We show that for large-scale plane-parallel chondrule-melting shocks the postshock equilibrium temperature is too high to avoid volatile loss. Even if we include radiative cooling in lateral directions out of the disk plane into our model (thereby breaking strict plane-parallel geometry) we find that for a realistic vertical extent of the solar nebula disk the temperature decline is not fast enough. On the other hand, if we assume that the shock is entirely optically thin so that particles can radiate freely, the cooling rates are too high to produce the observed chondrules textures. Global nebular shocks are therefore problematic as the primary sources of chondrules.
Coupled 1D-2D hydrodynamic inundation model for sewer overflow: Influence of modeling parameters
Directory of Open Access Journals (Sweden)
Adeniyi Ganiyu Adeogun
2015-10-01
Full Text Available This paper presents outcome of our investigation on the influence of modeling parameters on 1D-2D hydrodynamic inundation model for sewer overflow, developed through coupling of an existing 1D sewer network model (SWMM and 2D inundation model (BREZO. The 1D-2D hydrodynamic model was developed for the purpose of examining flood incidence due to surcharged water on overland surface. The investigation was carried out by performing sensitivity analysis on the developed model. For the sensitivity analysis, modeling parameters, such as mesh resolution Digital Elevation Model (DEM resolution and roughness were considered. The outcome of the study shows the model is sensitive to changes in these parameters. The performance of the model is significantly influenced, by the Manning's friction value, the DEM resolution and the area of the triangular mesh. Also, changes in the aforementioned modeling parameters influence the Flood characteristics, such as the inundation extent, the flow depth and the velocity across the model domain. Keywords: Inundation, DEM, Sensitivity analysis, Model coupling, Flooding
ASYMPTOTIC STEADY-STATE SOLUTION TO A BOW SHOCK WITH AN INFINITE MACH NUMBER
Energy Technology Data Exchange (ETDEWEB)
Yalinewich, Almog; Sari, Re’em [Racah Institute of Physics, the Hebrew University, 91904, Jerusalem (Israel)
2016-08-01
The problem of a cold gas flowing past a stationary obstacle is considered. We study the bow shock that forms around the obstacle and show that at large distances from the obstacle the shock front forms a parabolic solid of revolution. The profiles of the hydrodynamic variables in the interior of the shock are obtained by solution of the hydrodynamic equations in parabolic coordinates. The results are verified with a hydrodynamic simulation. The drag force on the obstacle is also calculated. Finally, we use these results to model the bow shock around an isolated neutron star.
On numerical considerations for modeling reactive astrophysical shocks
International Nuclear Information System (INIS)
Papatheodore, Thomas L.; Messer, O. E. Bronson
2014-01-01
Simulating detonations in astrophysical environments is often complicated by numerical approximations to shock structure. A common prescription to ensure correct detonation speeds and associated quantities is to prohibit burning inside the numerically broadened shock. We have performed a series of simulations to verify the efficacy of this approximation and to understand how resolution and dimensionality might affect its use. Our results show that in one dimension, prohibiting burning in the shock is important wherever the carbon burning length is not resolved, in keeping with the results of Fryxell et al. In two dimensions, we find that the prohibition of shock burning effectively inhibits the development of cellular structure for all but the most highly resolved cases. We discuss the possible impacts this outcome may have on sub-grid models and detonation propagation in models of Type Ia supernovae, including potential impacts on observables.
International Nuclear Information System (INIS)
Cooper, F.
1996-01-01
We review the assumptions and domain of applicability of Landau's Hydrodynamical Model. By considering two models of particle production, pair production from strong electric fields and particle production in the linear σ model, we demonstrate that many of Landau's ideas are verified in explicit field theory calculations
Evaluation of hydrodynamic ocean models as a first step in larval dispersal modelling
Vasile, Roxana; Hartmann, Klaas; Hobday, Alistair J.; Oliver, Eric; Tracey, Sean
2018-01-01
Larval dispersal modelling, a powerful tool in studying population connectivity and species distribution, requires accurate estimates of the ocean state, on a high-resolution grid in both space (e.g. 0.5-1 km horizontal grid) and time (e.g. hourly outputs), particularly of current velocities and water temperature. These estimates are usually provided by hydrodynamic models based on which larval trajectories and survival are computed. In this study we assessed the accuracy of two hydrodynamic models around Australia - Bluelink ReANalysis (BRAN) and Hybrid Coordinate Ocean Model (HYCOM) - through comparison with empirical data from the Australian National Moorings Network (ANMN). We evaluated the models' predictions of seawater parameters most relevant to larval dispersal - temperature, u and v velocities and current speed and direction - on the continental shelf where spawning and nursery areas for major fishery species are located. The performance of each model in estimating ocean parameters was found to depend on the parameter investigated and to vary from one geographical region to another. Both BRAN and HYCOM models systematically overestimated the mean water temperature, particularly in the top 140 m of water column, with over 2 °C bias at some of the mooring stations. HYCOM model was more accurate than BRAN for water temperature predictions in the Great Australian Bight and along the east coast of Australia. Skill scores between each model and the in situ observations showed lower accuracy in the models' predictions of u and v ocean current velocities compared to water temperature predictions. For both models, the lowest accuracy in predicting ocean current velocities, speed and direction was observed at 200 m depth. Low accuracy of both model predictions was also observed in the top 10 m of the water column. BRAN had more accurate predictions of both u and v velocities in the upper 50 m of water column at all mooring station locations. While HYCOM
Computational Flow Modeling of Hydrodynamics in Multiphase Trickle-Bed Reactors
Lopes, Rodrigo J. G.; Quinta-Ferreira, Rosa M.
2008-05-01
This study aims to incorporate most recent multiphase models in order to investigate the hydrodynamic behavior of a TBR in terms of pressure drop and liquid holdup. Taking into account transport phenomena such as mass and heat transfer, an Eulerian k-fluid model was developed resulting from the volume averaging of the continuity and momentum equations and solved for a 3D representation of the catalytic bed. Computational fluid dynamics (CFD) model predicts hydrodynamic parameters quite well if good closures for fluid/fluid and fluid/particle interactions are incorporated in the multiphase model. Moreover, catalytic performance is investigated with the catalytic wet oxidation of a phenolic pollutant.
Morison, K R; Hutchinson, C A
2009-01-01
The Weissler reaction in which iodide is oxidised to a tri-iodide complex (I(3)(-)) has been widely used for measurement of the intensity of ultrasonic and hydrodynamic cavitation. It was used in this work to compare ultrasonic cavitation at 24 kHz with hydrodynamic cavitation using two different devices, one a venturi and the other a sudden expansion, operated up to 8.7 bar. Hydrodynamic cavitation had a maximum efficiency of about 5 x 10(-11) moles of I(3)(-) per joule of energy compared with the maximum of almost 8 x 10(-11) mol J(-1) for ultrasonic cavitation. Hydrodynamic cavitation was found to be most effective at 10 degrees C compared with 20 degrees C and 30 degrees C and at higher upstream pressures. However, it was found that in hydrodynamic conditions, even without cavitation, I(3)(-) was consumed at a rapid rate leading to an equilibrium concentration. It was concluded that the Weissler reaction was not a good model reaction for the assessment of the effectiveness of hydrodynamic cavitation.
Thermo-hydrodynamic lubrication in hydrodynamic bearings
Bonneau, Dominique; Souchet, Dominique
2014-01-01
This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the thermo-hydrodynamic and the thermo-elasto-hydrodynamic lubrication. The algorithms are methodically detailed and each section is thoroughly illustrated.
International Nuclear Information System (INIS)
Inogamov, Nail A; Khokhlov, Viktor A; Zhakhovsky, Vasily V; Khishchenko, Konstantin V; Demaske, Brian J; Oleynik, Ivan I
2014-01-01
Ultrafast processes, including nonmonotonic expansion of material into vacuum, supersonic melting and generation of super-elastic shock wave, in a surface layer of metal irradiated by an ultrashort laser pulse are discussed. In addition to the well-established two-temperature (2T) evolution of heated layer a new effect of electron pressure gradient on early stage of material expansion is studied. It is shown that the expanding material experiences an unexpected jump in flow velocity in a place where stress exceeds the effective tensile strength provided by used EoS of material. Another 2T effect is that supersonic propagation of homogeneous melting front results in distortion of spatial profile of ion temperature, which later imprints on ion pressure profile transforming in a super-elastic shock wave with time.
Jin, Chao; Ren, Carolyn L; Emelko, Monica B
2016-04-19
It is widely believed that media surface roughness enhances particle deposition-numerous, but inconsistent, examples of this effect have been reported. Here, a new mathematical framework describing the effects of hydrodynamics and interaction forces on particle deposition on rough spherical collectors in absence of an energy barrier was developed and validated. In addition to quantifying DLVO force, the model includes improved descriptions of flow field profiles and hydrodynamic retardation functions. This work demonstrates that hydrodynamic effects can significantly alter particle deposition relative to expectations when only the DLVO force is considered. Moreover, the combined effects of hydrodynamics and interaction forces on particle deposition on rough, spherical media are not additive, but synergistic. Notably, the developed model's particle deposition predictions are in closer agreement with experimental observations than those from current models, demonstrating the importance of inclusion of roughness impacts in particle deposition description/simulation. Consideration of hydrodynamic contributions to particle deposition may help to explain discrepancies between model-based expectations and experimental outcomes and improve descriptions of particle deposition during physicochemical filtration in systems with nonsmooth collector surfaces.
Thermo-hydrodynamical modelling of a flooded deep mine reservoir - Case of the Lorraine Coal Basin
International Nuclear Information System (INIS)
Reichart, Guillaume
2015-01-01
Since 2006, cessation of dewatering in Lorraine Coal Basin (France) led to the flooding of abandoned mines, resulting in a new hydrodynamic balance in the area. Recent researches concerning geothermal exploitation of flooded reservoirs raised new questions, which we propose to answer. Our work aimed to understand the thermos-hydrodynamic behaviour of mine water in a flooding or flooded system. Firstly, we synthesized the geographical, geological and hydrogeological contexts of the Lorraine Coal Basin, and we chose a specific area for our studies. Secondly, temperature and electric conductivity log profiles were measured in old pits of the Lorraine Coal Basin, giving a better understanding of the water behaviour at a deep mine shaft scale. We were able to build a thermos-hydrodynamic model and simulate water behaviour at this scale. Flow regime stability is also studied. Thirdly, a hydrodynamic spatialized meshed model was realized to study the hydrodynamic behaviour of a mine reservoir as a whole. Observed water-table rise was correctly reproduced: moreover, the model can be used in a predictive way after the flooding. Several tools were tested, improved or developed to ease the study of flooded reservoirs, as three-dimensional up-scaling of hydraulic conductivities and a coupled spatialized meshed model with a pipe network. (author) [fr
Shock ignition of thermonuclear fuel: principles and modelling
International Nuclear Information System (INIS)
Atzeni, S.; Ribeyre, X.; Schurtz, G.; Schmitt, A.J.; Canaud, B.; Betti, R.; Perkins, L.J.
2014-01-01
Shock ignition is an approach to direct-drive inertial confinement fusion (ICF) in which the stages of compression and hot spot formation are partly separated. The fuel is first imploded at a lower velocity than in conventional ICF. Close to stagnation, an intense laser spike drives a strong converging shock, which contributes to hot spot formation. Shock ignition shows potentials for high gain at laser energies below 1 MJ, and could be tested on the National Ignition Facility or Laser MegaJoule. Shock ignition principles and modelling are reviewed in this paper. Target designs and computer-generated gain curves are presented and discussed. Limitations of present studies and research needs are outlined. (special topic)
Advanced Computational Modeling Approaches for Shock Response Prediction
Derkevorkian, Armen; Kolaini, Ali R.; Peterson, Lee
2015-01-01
Motivation: (1) The activation of pyroshock devices such as explosives, separation nuts, pin-pullers, etc. produces high frequency transient structural response, typically from few tens of Hz to several hundreds of kHz. (2) Lack of reliable analytical tools makes the prediction of appropriate design and qualification test levels a challenge. (3) In the past few decades, several attempts have been made to develop methodologies that predict the structural responses to shock environments. (4) Currently, there is no validated approach that is viable to predict shock environments overt the full frequency range (i.e., 100 Hz to 10 kHz). Scope: (1) Model, analyze, and interpret space structural systems with complex interfaces and discontinuities, subjected to shock loads. (2) Assess the viability of a suite of numerical tools to simulate transient, non-linear solid mechanics and structural dynamics problems, such as shock wave propagation.
Density waves in a lattice hydrodynamic traffic flow model with the anticipation effect
International Nuclear Information System (INIS)
Zhao Min; Sun Di-Hua; Tian Chuan
2012-01-01
By introducing the traffic anticipation effect in the real world into the original lattice hydrodynamic model, we present a new anticipation effect lattice hydrodynamic (AELH) model, and obtain the linear stability condition of the model by applying the linear stability theory. Through nonlinear analysis, we derive the Burgers equation and Korteweg-de Vries (KdV) equation, to describe the propagating behaviour of traffic density waves in the stable and the metastable regions, respectively. The good agreement between simulation results and analytical results shows that the stability of traffic flow can be enhanced when the anticipation effect is considered. (interdisciplinary physics and related areas of science and technology)
International Nuclear Information System (INIS)
Skalozubov, V.I.; Gablaya, T.V.; Vashchenko, V.N.; Gerasimenko, T.V.; Kozlov, I.L.
2014-01-01
We propose a hydrodynamic model of possible flooding of the industrial site at Zaporozh'e NPP design basis earthquakes and hurricane. In contrast to the quasi-stationary approach of stress tests in the proposed model takes into account the dynamic nature of the processes of flooding, as well as a direct impact of external influences on extreme Kakhovske reservoir. As a result of hydrodynamic modeling, the possible conditions and criteria for the flooding of the industrial site at Zaporozhe extreme external influences
Modelling free surface flows with smoothed particle hydrodynamics
Directory of Open Access Journals (Sweden)
L.Di G.Sigalotti
2006-01-01
Full Text Available In this paper the method of Smoothed Particle Hydrodynamics (SPH is extended to include an adaptive density kernel estimation (ADKE procedure. It is shown that for a van der Waals (vdW fluid, this method can be used to deal with free-surface phenomena without difficulties. In particular, arbitrary moving boundaries can be easily handled because surface tension is effectively simulated by the cohesive pressure forces. Moreover, the ADKE method is seen to increase both the accuracy and stability of SPH since it allows the width of the kernel interpolant to vary locally in a way that only the minimum necessary smoothing is applied at and near free surfaces and sharp fluid-fluid interfaces. The method is robust and easy to implement. Examples of its resolving power are given for both the formation of a circular liquid drop under surface tension and the nonlinear oscillation of excited drops.
Hydrodynamic Models for Multicomponent Plasmas with Collisional-Radiative Kinetics
2014-12-01
Boltzmann groups. The first excited state - H(2) - is the top curve , followed by the next higher level, etc. . . . . . . . . . . . . . . . . 141 5.3...solution with 3 levels and 1 Boltzmann group. H(3) - is the bottom curve , followed by the next higher level, etc.; the non-conforming red curve is H...problem of a diffraction of a shock wave (M = 2.4) down a step [73]. The strong rarefaction at the corner of the step can cause a problem of negative
Euler-Lagrange modeling of the hydrodynamics of dense multiphase flows
Padding, J.T.; Deen, N.G.; Peters, E. A. J. F.; Kuipers, J. A. M.
2015-01-01
The large-scale hydrodynamic behavior of relatively dense dispersed multiphase flows, such as encountered in fluidized beds, bubbly flows, and liquid sprays, can be predicted efficiently by use of Euler-Lagrange models. In these models, grid-averaged equations for the continuous-phase flow field are
Data-driven urban drainage analysis : An alternative to hydrodynamic models?
ten Veldhuis, J.A.E.; Tait, S.J.
2011-01-01
In the past, there has been an emphasis on the use of hydrodynamic models as a tool for urban drainage analysis. Limited availability of monitoring data and the perceived more limited resource requirements of models led to a preference for this approach. The last decade has seen a gradual
A SWOT analysis of hydrodynamic models with respect to simulating breaching
van Damme, M.; Visser, P.J.
2015-01-01
Deriving the bed shear stresses from hydrodynamic models in breach models is challenging due to the continuous changing hydraulic head over the breach in combination with horizontal and vertical flow contractions, and the continuous rapidly changing breach geometry. Three stages can be distinguished
DEFF Research Database (Denmark)
Jacobsen, Niels Gjøl; Fredsøe, Jørgen; Hjelmager Jensen, Jacob
2014-01-01
In this work a detailed hydrodynamic model is presented, which is used for the study of cross-shore sediment transport and morphodynamics in two dimensions. The model is described in the framework of the generally unstructured, finite volume method. Considerable emphasis is put on those subtletie...
Smoothed particle hydrodynamics model for phase separating fluid mixtures. I. General equations
Thieulot, C; Janssen, LPBM; Espanol, P
We present a thermodynamically consistent discrete fluid particle model for the simulation of a recently proposed set of hydrodynamic equations for a phase separating van der Waals fluid mixture [P. Espanol and C.A.P. Thieulot, J. Chem. Phys. 118, 9109 (2003)]. The discrete model is formulated by
Modeling hydrodynamic instabilities of double ablation fronts in inertial confinement fusion
International Nuclear Information System (INIS)
Yanez, C.; Sanz, J.; Olazabal-Loume, M.; Ibanez, L. F.
2013-01-01
A linear Rayleigh-Taylor instability theory of double ablation (DA) fronts is developed for direct-drive inertial confinement fusion. Two approaches are discussed: an analytical discontinuity model for the radiation dominated regime of very steep DA front structure, and a numerical self-consistent model that covers more general hydrodynamic profiles behaviours. Dispersion relation results are compared to 2D simulations. (authors)
International Nuclear Information System (INIS)
Montano-Ley, Y.; Peraza-Vizcarra, R.; Paez-Osuna, F.
2007-01-01
The tidal hydrodynamics of the Topolobampo coastal lagoon system (Mexico) has been investigated through a modified two dimensional non-linear hydrodynamic finite difference model. The advective and diffusive process acting over a hypothetical pollutant released into the coastal lagoon have also been simulated. Maxima tidal currents (0.85 m/s) were predicted within the main channel, in agree with direct measurements. The direction of the observed fastest currents (SW), also agree quite well with the direction of the strongest tidal current predicted in this investigation, which occur during the ebb when the water of the coastal lagoon is discharged into the Gulf of California. Residual currents (0.01-0.05 m/s) were also predicted. The hypothetical pollutant released within the Topolobampo Harbor would spread to both Ohuira and Topolobampo sections, reaching the inlet after approximately 12 days. - A model has been developed to simulate the tidal hydrodynamics and the behavior of a pollutant in the Topolobampo lagoon
A new model for friction under shock conditions
Directory of Open Access Journals (Sweden)
Dambakizi F.
2011-01-01
Full Text Available This article is aimed at the developpement of a new model for friction under shock conditions. Thanks to a subgrid model and a specific Coulomb friction law, it takes into account the interface temperature and deformation but also the influence of asperities when the contact pressure is relatively low (≤ 3 GPa.
Bonneau, Dominique; Souchet, Dominique
2014-01-01
This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.
Larmat, C. S.; Delorey, A.; Rougier, E.; Knight, E. E.; Steedman, D. W.; Bradley, C. R.
2017-12-01
This presentation reports numerical modeling efforts to improve knowledge of the processes that affect seismic wave generation and propagation from underground explosions, with a focus on Rg waves. The numerical model is based on the coupling of hydrodynamic simulation codes (Abaqus, CASH and HOSS), with a 3D full waveform propagation code, SPECFEM3D. Validation datasets are provided by the Source Physics Experiment (SPE) which is a series of highly instrumented chemical explosions at the Nevada National Security Site with yields from 100kg to 5000kg. A first series of explosions in a granite emplacement has just been completed and a second series in alluvium emplacement is planned for 2018. The long-term goal of this research is to review and improve current existing seismic sources models (e.g. Mueller & Murphy, 1971; Denny & Johnson, 1991) by providing first principles calculations provided by the coupled codes capability. The hydrodynamic codes, Abaqus, CASH and HOSS, model the shocked, hydrodynamic region via equations of state for the explosive, borehole stemming and jointed/weathered granite. A new material model for unconsolidated alluvium materials has been developed and validated with past nuclear explosions, including the 10 kT 1965 Merlin event (Perret, 1971) ; Perret and Bass, 1975). We use the efficient Spectral Element Method code, SPECFEM3D (e.g. Komatitsch, 1998; 2002), and Geologic Framework Models to model the evolution of wavefield as it propagates across 3D complex structures. The coupling interface is a series of grid points of the SEM mesh situated at the edge of the hydrodynamic code domain. We will present validation tests and waveforms modeled for several SPE tests which provide evidence that the damage processes happening in the vicinity of the explosions create secondary seismic sources. These sources interfere with the original explosion moment and reduces the apparent seismic moment at the origin of Rg waves up to 20%.
Hydrodynamic interaction between two trapped swimming model micro-organisms.
Matas Navarro, R; Pagonabarraga, I
2010-09-01
We present a theoretical study of the behaviour of two active particles under the action of harmonic traps kept at a fixed distance away from each other. We classify the steady configurations the squirmers develop as a function of their self-propelling velocity and the active stresses the swimmers induce around them. We have further analyzed the stability of such configurations, and have found that the ratio between their self-propelling velocity and the apolar flow generated through active stresses determines whether collinear parallel squirmers or perpendicularly swimming particles moving away from each other are stable. Therefore, there is a close connection between the stable configurations and the active mechanisms leading to the particle self-propulsion. The trap potential does not affect the stability of the configurations; it only modifies some of their relevant time scales. We have also observed the development of characteristic frequencies which should be observable. Finally, we show that the development of the hydrodynamic flows induced by the active particles may be relevant even when its time scale orders of magnitude smaller than the other present characteristic time scales and may destabilize the stable configurations.
Godunov-type schemes for hydrodynamic and magnetohydrodynamic modeling
International Nuclear Information System (INIS)
Vides-Higueros, Jeaniffer
2014-01-01
The main objective of this thesis concerns the study, design and numerical implementation of finite volume schemes based on the so-Called Godunov-Type solvers for hyperbolic systems of nonlinear conservation laws, with special attention given to the Euler equations and ideal MHD equations. First, we derive a simple and genuinely two-Dimensional Riemann solver for general conservation laws that can be regarded as an actual 2D generalization of the HLL approach, relying heavily on the consistency with the integral formulation and on the proper use of Rankine-Hugoniot relations to yield expressions that are simple enough to be applied in the structured and unstructured contexts. Then, a comparison between two methods aiming to numerically maintain the divergence constraint of the magnetic field for the ideal MHD equations is performed and we show how the 2D Riemann solver can be employed to obtain robust divergence-Free simulations. Next, we derive a relaxation scheme that incorporates gravity source terms derived from a potential into the hydrodynamic equations, an important problem in astrophysics, and finally, we review the design of finite volume approximations in curvilinear coordinates, providing a fresher view on an alternative discretization approach. Throughout this thesis, numerous numerical results are shown. (author) [fr
International Nuclear Information System (INIS)
R Paul Drake
2004-01-01
OAK-B135 This is the final report from the project Hydrodynamics by High-Energy-Density Plasma Flow and Hydrodynamics and Radiation Hydrodynamics with Astrophysical Applications. This project supported a group at the University of Michigan in the invention, design, performance, and analysis of experiments using high-energy-density research facilities. The experiments explored compressible nonlinear hydrodynamics, in particular at decelerating interfaces, and the radiation hydrodynamics of strong shock waves. It has application to supernovae, astrophysical jets, shock-cloud interactions, and radiative shock waves
Cosmic-ray shock acceleration in oblique MHD shocks
Webb, G. M.; Drury, L. OC.; Volk, H. J.
1986-01-01
A one-dimensional, steady-state hydrodynamical model of cosmic-ray acceleration at oblique MHD shocks is presented. Upstream of the shock the incoming thermal plasma is subject to the adverse pressure gradient of the accelerated particles, the J x B force, as well as the thermal gas pressure gradient. The efficiency of the acceleration of cosmic-rays at the shock as a function of the upstream magnetic field obliquity and upstream plasma beta is investigated. Astrophysical applications of the results are briefly discussed.
Directory of Open Access Journals (Sweden)
Mazda Biglari
2016-06-01
Full Text Available Two modeling approaches, the scaling-law and CFD (Computational Fluid Dynamics approaches, are presented in this paper. To save on experimental cost of the pilot plant, the scaling-law approach as a low-computational-cost method was adopted and a small scale column operating under ambient temperature and pressure was built. A series of laboratory tests and computer simulations were carried out to evaluate the hydrodynamic characteristics of a pilot fluidized-bed biomass gasifier. In the small scale column solids were fluidized. The pressure and other hydrodynamic properties were monitored for the validation of the scaling-law application. In addition to the scaling-law modeling method, the CFD approach was presented to simulate the gas-particle system in the small column. 2D CFD models were developed to simulate the hydrodynamic regime. The simulation results were validated with the experimental data from the small column. It was proved that the CFD model was able to accurately predict the hydrodynamics of the small column. The outcomes of this research present both the scaling law with the lower computational cost and the CFD modeling as a more robust method to suit various needs for the design of fluidized-bed gasifiers.
Li, Dong Feng; Bai, Fu Qing; Nie, Hui
2018-06-01
In order to analyze the influence of bridge holes widening on hydrodynamic such as water level, a two-dimensional mathematical model was used to calculate the hydrodynamic factors, river network flow velocity vector distribution is given, water level and difference of bridge widening before and after is calculated and charted, water surface gradient in seven different river sections near the upper reaches of bridges is counted and revealed. The results of hydrodynamic calculation indicate that The Maximum and the minimum deducing numerical value of the water level after bridge widening is 0.028m, and 0.018m respective. the seven sections water surface gradient becomes smaller until it becomes negative, the influence of bridge widening on the upstream is basically over, the range of influence is about 450m from the bridge to the upstream. reach
Hydrodynamic modelling of a tidal delta wetland using an enhanced quasi-2D model
Wester, Sjoerd J.; Grimson, Rafael; Minotti, Priscilla G.; Booija, Martijn J.; Brugnach, Marcela
2018-04-01
Knowledge about the hydrological regime of wetlands is key to understand their physical and biological properties. Modelling hydrological and hydrodynamic processes within a wetland is therefore becoming increasingly important. 3D models have successfully modelled wetland dynamics but depend on very detailed bathymetry and land topography. Many 1D and 2D models of river deltas highly simplify the interaction between the river and wetland area or simply neglect the wetland area. This study proposes an enhanced quasi-2D modelling strategy that captures the interaction between river discharge and moon tides and the resulting hydrodynamics, while using the scarce data available. The water flow equations are discretised with an interconnected irregular cell scheme, in which a simplification of the 1D Saint-Venant equations is used to define the water flow between cells. The spatial structure of wetlands is based on the ecogeomorphology in complex estuarine deltas. The islands within the delta are modelled with levee cells, creek cells and an interior cell representing a shallow marsh wetland. The model is calibrated for an average year and the model performance is evaluated for another average year and additionally an extreme dry three-month period and an extreme wet three-month period. The calibration and evaluation are done based on two water level measurement stations and two discharge measurement stations, all located in the main rivers. Additional calibration is carried out with field water level measurements in a wetland area. Accurate simulations are obtained for both calibration and evaluation with high correlations between observed and simulated water levels and simulated discharges in the same order of magnitude as observed discharges. Calibration against field measurements showed that the model can successfully simulate the overflow mechanism in wetland areas. A sensitivity analysis for several wetland parameters showed that these parameters are all
Frequency-Domain Hydrodynamic Modelling of Dense and Sparse Arrays of Wave Energy Converters
Wei, Yanji; Barradas Berglind, Jose de Jesus; Yu, Zhiheng; van Rooij, Marijn; Prins, Wouter; Jayawardhana, Bayu; Vakis, Antonis I.
2018-01-01
In this work, we develop a frequency-domain model to study the hydrodynamic behaviour of a floater blanket (FB), i.e., an array of floater elements individually connected to power take-off (PTO) systems, which constitutes the core technology of the novel Ocean Grazer (OG) wave energy converter
Improving hydrodynamic modeling of an estuary in a mixed tidal regime by grid refining and aligning
Hasan, G.M.J.; van Maren, D.S.; Cheong, H.F.
2011-01-01
Water levels and flows in the Singapore coastal waters are driven by the complex interactions of the Indian and Pacific Ocean tides, seasonal monsoon-driven contributions and also forced by local winds. The Singapore Regional Model was developed to simulate hydrodynamics in the Strait of Singapore
Hydrodynamic and thermal modelling of gas-particle flow in fluidized beds
International Nuclear Information System (INIS)
Abdelkawi, O.S; Abdalla, A.M.; Atwan, E.F; Abdelmonem, S.A.; Elshazly, K.M.
2009-01-01
In this study a mathematical model has been developed to simulate two dimensional fluidized bed with uniform fluidization. The model consists of two sub models for hydrodynamic and thermal behavior of fluidized bed on which a FORTRAN program entitled (NEWFLUIDIZED) is devolved. The program is used to predict the volume fraction of gas and particle phases, the velocity of the two phases, the gas pressure and the temperature distribution for two phases. Also the program calculates the heat transfer coefficient. Besides the program predicts the fluidized bed stability and determines the optimum input gas velocity for fluidized bed to achieve the best thermal behavior. The hydrodynamic model is verified by comparing its results with the computational fluid dynamic code MFIX . While the thermal model was tested and compared by the available previous experimental correlations.The model results show good agreement with MFIX results and the thermal model of the present work confirms Zenz and Gunn equations
Pahar, Gourabananda; Dhar, Anirban
2017-04-01
A coupled solenoidal Incompressible Smoothed Particle Hydrodynamics (ISPH) model is presented for simulation of sediment displacement in erodible bed. The coupled framework consists of two separate incompressible modules: (a) granular module, (b) fluid module. The granular module considers a friction based rheology model to calculate deviatoric stress components from pressure. The module is validated for Bagnold flow profile and two standardized test cases of sediment avalanching. The fluid module resolves fluid flow inside and outside porous domain. An interaction force pair containing fluid pressure, viscous term and drag force acts as a bridge between two different flow modules. The coupled model is validated against three dambreak flow cases with different initial conditions of movable bed. The simulated results are in good agreement with experimental data. A demonstrative case considering effect of granular column failure under full/partial submergence highlights the capability of the coupled model for application in generalized scenario.
Initial conditions of radiative shock experiments
International Nuclear Information System (INIS)
Kuranz, C. C.; Drake, R. P.; Krauland, C. M.; Marion, D. C.; Grosskopf, M. J.; Rutter, E.; Torralva, B.; Holloway, J. P.; Bingham, D.; Goh, J.; Boehly, T. R.; Sorce, A. T.
2013-01-01
We performed experiments at the Omega Laser Facility to characterize the initial, laser-driven state of a radiative shock experiment. These experiments aimed to measure the shock breakout time from a thin, laser-irradiated Be disk. The data are then used to inform a range of valid model parameters, such as electron flux limiter and polytropic γ, used when simulating radiative shock experiments using radiation hydrodynamics codes. The characterization experiment and the radiative shock experiment use a laser irradiance of ∼7 × 10 14 W cm −2 to launch a shock in the Be disk. A velocity interferometer and a streaked optical pyrometer were used to infer the amount of time for the shock to move through the Be disk. The experimental results were compared with simulation results from the Hyades code, which can be used to model the initial conditions of a radiative shock system using the CRASH code
International Nuclear Information System (INIS)
Mohd Ekhwan Toriman; Mohd Ekhwan Toriman; Norbaya Hashim; Mohd Khairul Amri Kamarudin; Abdul Jalil Hassan; Ayaari Muhamad; Nor Azlina Abd Aziz
2015-01-01
Issues such as water pollution and extraction of water from Sungai Selangor system has been said to be the cause of fading fireflies. Salinity intrusion into estuary of the Sungai Selangor has been carried out on a hydrodynamic numerical modeling to access the parameter that governed the amount of salt in the river. The berembang trees on the river bank that become the fireflies habitat need some amount of salt for proper growth. Living at the lower reaches of Sungai Selangor, the fireflies are affected not only by the activities in their vicinity, but by activities in the entire river basin. Rapid economic development in the basin and the strong demand for the water resources puts pressure on the ecosystem. This research has been carried out to investigate the effect of water extraction along Sungai Selangor towards altering the amount of salt content in the river. The hydrodynamic modeling with regards to the salt content is expected to support long term assessment that may affect the berembang trees as a result of changes in the flow from upstream because of the water abstraction activity for domestic water supply. (author)
The effect of coupling hydrologic and hydrodynamic models on probable maximum flood estimation
Felder, Guido; Zischg, Andreas; Weingartner, Rolf
2017-07-01
Deterministic rainfall-runoff modelling usually assumes stationary hydrological system, as model parameters are calibrated with and therefore dependant on observed data. However, runoff processes are probably not stationary in the case of a probable maximum flood (PMF) where discharge greatly exceeds observed flood peaks. Developing hydrodynamic models and using them to build coupled hydrologic-hydrodynamic models can potentially improve the plausibility of PMF estimations. This study aims to assess the potential benefits and constraints of coupled modelling compared to standard deterministic hydrologic modelling when it comes to PMF estimation. The two modelling approaches are applied using a set of 100 spatio-temporal probable maximum precipitation (PMP) distribution scenarios. The resulting hydrographs, the resulting peak discharges as well as the reliability and the plausibility of the estimates are evaluated. The discussion of the results shows that coupling hydrologic and hydrodynamic models substantially improves the physical plausibility of PMF modelling, although both modelling approaches lead to PMF estimations for the catchment outlet that fall within a similar range. Using a coupled model is particularly suggested in cases where considerable flood-prone areas are situated within a catchment.
Evaluating meteo marine climatic model inputs for the investigation of coastal hydrodynamics
Bellafiore, D.; Bucchignani, E.; Umgiesser, G.
2010-09-01
One of the major aspects discussed in the recent works on climate change is how to provide information from the global scale to the local one. In fact the influence of sea level rise and changes in the meteorological conditions due to climate change in strategic areas like the coastal zone is at the base of the well known mitigation and risk assessment plans. The investigation of the coastal zone hydrodynamics, from a modeling point of view, has been the field for the connection between hydraulic models and ocean models and, in terms of process studies, finite element models have demonstrated their suitability in the reproduction of complex coastal morphology and in the capability to reproduce different spatial scale hydrodynamic processes. In this work the connection between two different model families, the climate models and the hydrodynamic models usually implemented for process studies, is tested. Together, they can be the most suitable tool for the investigation of climate change on coastal systems. A finite element model, SHYFEM (Shallow water Hydrodynamic Finite Element Model), is implemented on the Adriatic Sea, to investigate the effect of wind forcing datasets produced by different downscaling from global climate models in terms of surge and its coastal effects. The wind datasets are produced by the regional climate model COSMO-CLM (CIRA), and by EBU-POM model (Belgrade University), both downscaling from ECHAM4. As a first step the downscaled wind datasets, that have different spatial resolutions, has been analyzed for the period 1960-1990 to compare what is their capability to reproduce the measured wind statistics in the coastal zone in front of the Venice Lagoon. The particularity of the Adriatic Sea meteo climate is connected with the influence of the orography in the strengthening of winds like Bora, from North-East. The increase in spatial resolution permits the more resolved wind dataset to better reproduce meteorology and to provide a more
Doyon, Benjamin; Dubail, Jérôme; Konik, Robert; Yoshimura, Takato
2017-11-01
The theory of generalized hydrodynamics (GHD) was recently developed as a new tool for the study of inhomogeneous time evolution in many-body interacting systems with infinitely many conserved charges. In this Letter, we show that it supersedes the widely used conventional hydrodynamics (CHD) of one-dimensional Bose gases. We illustrate this by studying "nonlinear sound waves" emanating from initial density accumulations in the Lieb-Liniger model. We show that, at zero temperature and in the absence of shocks, GHD reduces to CHD, thus for the first time justifying its use from purely hydrodynamic principles. We show that sharp profiles, which appear in finite times in CHD, immediately dissolve into a higher hierarchy of reductions of GHD, with no sustained shock. CHD thereon fails to capture the correct hydrodynamics. We establish the correct hydrodynamic equations, which are finite-dimensional reductions of GHD characterized by multiple, disjoint Fermi seas. We further verify that at nonzero temperature, CHD fails at all nonzero times. Finally, we numerically confirm the emergence of hydrodynamics at zero temperature by comparing its predictions with a full quantum simulation performed using the NRG-TSA-abacus algorithm. The analysis is performed in the full interaction range, and is not restricted to either weak- or strong-repulsion regimes.
Polomčić, Dušan M.; Bajić, Dragoljub I.; Močević, Jelena M.
2015-01-01
The calibration process of hydrodynamic model is done usually manually by 'testing' with different values of hydrogeological parameters and hydraulic characteristics of the boundary conditions. By using the PEST program, automatic calibration of models has been introduced, and it has proved to significantly reduce the subjective influence of the model creator on results. With the relatively new approach of PEST, i.e. with the introduction of so-called 'pilot points', the concept of homogeneou...
A multiple shock model for common cause failures using discrete Markov chain
International Nuclear Information System (INIS)
Chung, Dae Wook; Kang, Chang Soon
1992-01-01
The most widely used models in common cause analysis are (single) shock models such as the BFR, and the MFR. But, single shock model can not treat the individual common cause separately and has some irrational assumptions. Multiple shock model for common cause failures is developed using Markov chain theory. This model treats each common cause shock as separately and sequently occuring event to implicate the change in failure probability distribution due to each common cause shock. The final failure probability distribution is evaluated and compared with that from the BFR model. The results show that multiple shock model which minimizes the assumptions in the BFR model is more realistic and conservative than the BFR model. The further work for application is the estimations of parameters such as common cause shock rate and component failure probability given a shock,p, through the data analysis
Improving Watershed-Scale Hydrodynamic Models by Incorporating Synthetic 3D River Bathymetry Network
Dey, S.; Saksena, S.; Merwade, V.
2017-12-01
Digital Elevation Models (DEMs) have an incomplete representation of river bathymetry, which is critical for simulating river hydrodynamics in flood modeling. Generally, DEMs are augmented with field collected bathymetry data, but such data are available only at individual reaches. Creating a hydrodynamic model covering an entire stream network in the basin requires bathymetry for all streams. This study extends a conceptual bathymetry model, River Channel Morphology Model (RCMM), to estimate the bathymetry for an entire stream network for application in hydrodynamic modeling using a DEM. It is implemented at two large watersheds with different relief and land use characterizations: coastal Guadalupe River basin in Texas with flat terrain and a relatively urban White River basin in Indiana with more relief. After bathymetry incorporation, both watersheds are modeled using HEC-RAS (1D hydraulic model) and Interconnected Pond and Channel Routing (ICPR), a 2-D integrated hydrologic and hydraulic model. A comparison of the streamflow estimated by ICPR at the outlet of the basins indicates that incorporating bathymetry influences streamflow estimates. The inundation maps show that bathymetry has a higher impact on flat terrains of Guadalupe River basin when compared to the White River basin.
A linked hydrodynamic and water quality model for the Salton Sea
Chung, E.G.; Schladow, S.G.; Perez-Losada, J.; Robertson, Dale M.
2008-01-01
A linked hydrodynamic and water quality model was developed and applied to the Salton Sea. The hydrodynamic component is based on the one-dimensional numerical model, DLM. The water quality model is based on a new conceptual model for nutrient cycling in the Sea, and simulates temperature, total suspended sediment concentration, nutrient concentrations, including PO4-3, NO3-1 and NH4+1, DO concentration and chlorophyll a concentration as functions of depth and time. Existing water temperature data from 1997 were used to verify that the model could accurately represent the onset and breakup of thermal stratification. 1999 is the only year with a near-complete dataset for water quality variables for the Salton Sea. The linked hydrodynamic and water quality model was run for 1999, and by adjustment of rate coefficients and other water quality parameters, a good match with the data was obtained. In this article, the model is fully described and the model results for reductions in external phosphorus load on chlorophyll a distribution are presented. ?? 2008 Springer Science+Business Media B.V.
Wang, Zhen-yu; Yu, Jian-cheng; Zhang, Ai-qun; Wang, Ya-xing; Zhao, Wen-tao
2017-12-01
Combining high precision numerical analysis methods with optimization algorithms to make a systematic exploration of a design space has become an important topic in the modern design methods. During the design process of an underwater glider's flying-wing structure, a surrogate model is introduced to decrease the computation time for a high precision analysis. By these means, the contradiction between precision and efficiency is solved effectively. Based on the parametric geometry modeling, mesh generation and computational fluid dynamics analysis, a surrogate model is constructed by adopting the design of experiment (DOE) theory to solve the multi-objects design optimization problem of the underwater glider. The procedure of a surrogate model construction is presented, and the Gaussian kernel function is specifically discussed. The Particle Swarm Optimization (PSO) algorithm is applied to hydrodynamic design optimization. The hydrodynamic performance of the optimized flying-wing structure underwater glider increases by 9.1%.
Surface Ship Shock Modeling and Simulation: Two-Dimensional Analysis
Directory of Open Access Journals (Sweden)
Young S. Shin
1998-01-01
Full Text Available The modeling and simulation of the response of a surface ship system to underwater explosion requires an understanding of many different subject areas. These include the process of underwater explosion events, shock wave propagation, explosion gas bubble behavior and bubble-pulse loading, bulk and local cavitation, free surface effect, fluid-structure interaction, and structural dynamics. This paper investigates the effects of fluid-structure interaction and cavitation on the response of a surface ship using USA-NASTRAN-CFA code. First, the one-dimensional Bleich-Sandler model is used to validate the approach, and second, the underwater shock response of a two-dimensional mid-section model of a surface ship is predicted with a surrounding fluid model using a constitutive equation of a bilinear fluid which does not allow transmission of negative pressures.
Directory of Open Access Journals (Sweden)
Ling Kang
2017-03-01
Full Text Available Compared to the hydrostatic hydrodynamic model, the non-hydrostatic hydrodynamic model can accurately simulate flows that feature vertical accelerations. The model’s low computational efficiency severely restricts its wider application. This paper proposes a non-hydrostatic hydrodynamic model based on a multithreading parallel computing method. The horizontal momentum equation is obtained by integrating the Navier–Stokes equations from the bottom to the free surface. The vertical momentum equation is approximated by the Keller-box scheme. A two-step method is used to solve the model equations. A parallel strategy based on block decomposition computation is utilized. The original computational domain is subdivided into two subdomains that are physically connected via a virtual boundary technique. Two sub-threads are created and tasked with the computation of the two subdomains. The producer–consumer model and the thread lock technique are used to achieve synchronous communication between sub-threads. The validity of the model was verified by solitary wave propagation experiments over a flat bottom and slope, followed by two sinusoidal wave propagation experiments over submerged breakwater. The parallel computing method proposed here was found to effectively enhance computational efficiency and save 20%–40% computation time compared to serial computing. The parallel acceleration rate and acceleration efficiency are approximately 1.45% and 72%, respectively. The parallel computing method makes a contribution to the popularization of non-hydrostatic models.
Oil shocks in New Keynesian models: Positive and normative implications
Chang, Jian
Chapter 1 investigates optimal monetary policy response towards oil shocks in a New Keynesian model. We find that optimal policy, in general, becomes contractionary in response to an adverse oil shock. However, the optimal policy rule and the inflation-output trade-off depend on the specific structure of the model. The benchmark economy consists of a flexible-price energy sector and a sticky-price manufacturing sector where energy is used as an intermediate input. We show that optimal policy is to stabilize the sticky (core) price level. We then show that after incorporating a less oil-dependent sticky-price service sector, the model exhibits a trade-off in stabilizing prices and output gaps in the different sticky-price sectors. It predicts that central bank should not try to stabilize the core price level, and the economy will experience higher inflation and rising output gaps, even if central banks respond optimally. Chapter 2 addresses the observed volatility and persistence of real exchange rates and the terms of trade. It contributes to the literature with a quantitative study on the U.S. and Canada. A two-country New Keynesian model consisting of traded, non-traded, and oil production sectors is proposed to examine the time series properties of the real exchange rate, the terms of trade and the real oil price. We find that after incorporating several realistic features (namely oil price shocks, sector specific labor, non-traded goods, asymmetric pricing decisions of exporters and asymmetric consumer preferences over tradables), the benchmark model broadly matches the volatilities of the relative prices and some business cycle correlations. The model matches the data more closely after adding real demand shocks, suggesting their importance in explaining the relative price movements between the US and Canada. Chapter 3 explores several sources and transmission channels of international relative price movements. In particular, we elaborate on the role of
Validation of Hydrodynamic Numerical Model of a Pitching Wave Energy Converter
DEFF Research Database (Denmark)
López, Maria del Pilar Heras; Thomas, Sarah; Kramer, Morten Mejlhede
2017-01-01
Validation of numerical model is essential in the development of new technologies. Commercial software and codes available simulating wave energy converters (WECs) have not been proved to work for all the available and upcoming technologies yet. The present paper presents the first stages...... of the validation process of a hydrodynamic numerical model for a pitching wave energy converter. The development of dry tests, wave flume and wave basin experiments are going to be explained, lessons learned shared and results presented....
Non-standard model for electron heat transport for multidimensional hydrodynamic codes
Energy Technology Data Exchange (ETDEWEB)
Nicolai, Ph.; Busquet, M.; Schurtz, G. [CEA/DAM-Ile de France, 91 - Bruyeres Le Chatel (France)
2000-07-01
In simulations of laser-produced plasma, modeling of heat transport requires an artificial limitation of standard Spitzer-Haerm fluxes. To improve heat conduction processing, we have developed a multidimensional model which accounts for non-local features of heat transport and effects of self-generated magnetic fields. This consistent treatment of both mechanisms has been implemented in a two-dimensional radiation-hydrodynamic code. First results indicate good agreements between simulations and experimental data. (authors)
Non-standard model for electron heat transport for multidimensional hydrodynamic codes
International Nuclear Information System (INIS)
Nicolai, Ph.; Busquet, M.; Schurtz, G.
2000-01-01
In simulations of laser-produced plasma, modeling of heat transport requires an artificial limitation of standard Spitzer-Haerm fluxes. To improve heat conduction processing, we have developed a multidimensional model which accounts for non-local features of heat transport and effects of self-generated magnetic fields. This consistent treatment of both mechanisms has been implemented in a two-dimensional radiation-hydrodynamic code. First results indicate good agreements between simulations and experimental data. (authors)
Stochastic-hydrodynamic model of halo formation in charged particle beams
Directory of Open Access Journals (Sweden)
Nicola Cufaro Petroni
2003-03-01
Full Text Available The formation of the beam halo in charged particle accelerators is studied in the framework of a stochastic-hydrodynamic model for the collective motion of the particle beam. In such a stochastic-hydrodynamic theory the density and the phase of the charged beam obey a set of coupled nonlinear hydrodynamic equations with explicit time-reversal invariance. This leads to a linearized theory that describes the collective dynamics of the beam in terms of a classical Schrödinger equation. Taking into account space-charge effects, we derive a set of coupled nonlinear hydrodynamic equations. These equations define a collective dynamics of self-interacting systems much in the same spirit as in the Gross-Pitaevskii and Landau-Ginzburg theories of the collective dynamics for interacting quantum many-body systems. Self-consistent solutions of the dynamical equations lead to quasistationary beam configurations with enhanced transverse dispersion and transverse emittance growth. In the limit of a frozen space-charge core it is then possible to determine and study the properties of stationary, stable core-plus-halo beam distributions. In this scheme the possible reproduction of the halo after its elimination is a consequence of the stationarity of the transverse distribution which plays the role of an attractor for every other distribution.
Modelling of hydrodynamic mechanisms of pollutant propagation in coastal zones
International Nuclear Information System (INIS)
Benque, J.P.
1982-11-01
The results of this document have to be distinguished in mathematical models applicable to small-area problems (horizontal scale comparable to depth) and models applicable to large-area phenomena (horizontal scales much greater than depth, quasi-hydrostatic approximation). In the case of the former, progress remains to be made in the simulation of turbulence and in the development of algorithms applicable under often very complex geometrical conditions. Excellent results are obtained by combining mathematical models with reduced-scale models, the former (on larger scales) providing the boundary conditions for the tank of the physical models. Large-area problems can be tackled only by means of mathematical models. These models are extremely efficient for the calculation of mesoscale circulation and transport of pollutants, but they all run into the same difficulty of simulating long-term problems and of determining drift currents. The principal difficulty faced by mesoscale or macroscale models is the determination of atmospheric conditions and of boundary conditions in the open sea. Mathematical models make it possible to determine the situation at every point of a given coastal zone and require only the conditions at the boundaries of the zone for this purpose. However, although these conditions at the boundary correspond to an experimental effort small in relation to total surveillance of the zone, they are essential to the predictions of the mathematical model, and efforts must be made to obtain the best possible boundary conditions. In addition to these experimental surveys at the boundaries, a certain number of observations within the zone are needed for the calibration of the model, i.e. for the determination of certain numerical coefficients appearing in the parametrization
Southeast Oahu Coastal Hydrodynamic Modeling with ADCIRC and STWAVE
2008-07-01
technique, nearshore conditions are extracted from the wave model results for each simulation. A transforma- tion correlation between the offshore and...21 Figure 19. Location of extracted STWAVE model results...Figure 4. Wave roses for ADCP #1 (left) and #2 (right). Figure 5. GPS current drogue (left) with traditional drifter (behind grapefruit ) and
Computer experiments with a coarse-grid hydrodynamic climate model
International Nuclear Information System (INIS)
Stenchikov, G.L.
1990-01-01
A climate model is developed on the basis of the two-level Mintz-Arakawa general circulation model of the atmosphere and a bulk model of the upper layer of the ocean. A detailed model of the spectral transport of shortwave and longwave radiation is used to investigate the radiative effects of greenhouse gases. The radiative fluxes are calculated at the boundaries of five layers, each with a pressure thickness of about 200 mb. The results of the climate sensitivity calculations for mean-annual and perpetual seasonal regimes are discussed. The CCAS (Computer Center of the Academy of Sciences) climate model is used to investigate the climatic effects of anthropogenic changes of the optical properties of the atmosphere due to increasing CO 2 content and aerosol pollution, and to calculate the sensitivity to changes of land surface albedo and humidity
Hoch, Jannis M.; Neal, Jeffrey C.; Baart, Fedor; van Beek, Rens; Winsemius, Hessel C.; Bates, Paul D.; Bierkens, Marc F. P.
2017-10-01
We here present GLOFRIM, a globally applicable computational framework for integrated hydrological-hydrodynamic modelling. GLOFRIM facilitates spatially explicit coupling of hydrodynamic and hydrologic models and caters for an ensemble of models to be coupled. It currently encompasses the global hydrological model PCR-GLOBWB as well as the hydrodynamic models Delft3D Flexible Mesh (DFM; solving the full shallow-water equations and allowing for spatially flexible meshing) and LISFLOOD-FP (LFP; solving the local inertia equations and running on regular grids). The main advantages of the framework are its open and free access, its global applicability, its versatility, and its extensibility with other hydrological or hydrodynamic models. Before applying GLOFRIM to an actual test case, we benchmarked both DFM and LFP for a synthetic test case. Results show that for sub-critical flow conditions, discharge response to the same input signal is near-identical for both models, which agrees with previous studies. We subsequently applied the framework to the Amazon River basin to not only test the framework thoroughly, but also to perform a first-ever benchmark of flexible and regular grids on a large-scale. Both DFM and LFP produce comparable results in terms of simulated discharge with LFP exhibiting slightly higher accuracy as expressed by a Kling-Gupta efficiency of 0.82 compared to 0.76 for DFM. However, benchmarking inundation extent between DFM and LFP over the entire study area, a critical success index of 0.46 was obtained, indicating that the models disagree as often as they agree. Differences between models in both simulated discharge and inundation extent are to a large extent attributable to the gridding techniques employed. In fact, the results show that both the numerical scheme of the inundation model and the gridding technique can contribute to deviations in simulated inundation extent as we control for model forcing and boundary conditions. This study shows
Hydrodynamic modeling of laser interaction with micro-structured targets
International Nuclear Information System (INIS)
Velechovsky, Jan; Limpouch, Jiri; Liska, Richard; Tikhonchuk, Vladimir
2016-01-01
A model is developed for numerical simulations of laser absorption in plasmas made of porous materials, with particular interest in low-density foams. Laser absorption is treated on two spatial scales simultaneously. At the microscale, the expansion of a thin solid pore wall is modeled in one dimension and the information obtained is used in the macroscale fluid simulations for the description of the plasma homogenization behind the ionization front. This two-scale laser absorption model is implemented in the arbitrary Lagrangian–Eulerian hydrocode PALE. In conclusion, the numerical simulations of laser penetration into low-density foams compare favorably with published experimental data.
Numerical Modelling and Prediction of Erosion Induced by Hydrodynamic Cavitation
Peters, A.; Lantermann, U.; el Moctar, O.
2015-12-01
The present work aims to predict cavitation erosion using a numerical flow solver together with a new developed erosion model. The erosion model is based on the hypothesis that collapses of single cavitation bubbles near solid boundaries form high velocity microjets, which cause sonic impacts with high pressure amplitudes damaging the surface. The erosion model uses information from a numerical Euler-Euler flow simulation to predict erosion sensitive areas and assess the erosion aggressiveness of the flow. The obtained numerical results were compared to experimental results from tests of an axisymmetric nozzle.
A Possible Universe in Pulsation by Using a Hydro-Dynamical Model for Gravity
Directory of Open Access Journals (Sweden)
Corneliu BERBENTE
2016-12-01
Full Text Available By using a hydro-dynamical model for gravity previously given by the author, a pulsating universe is possible to describe. This is possible because two hydro-dynamical sources are in attraction both when they are emitting and absorbing fluid. In our model, bodies (matter and energy are interacting via an incompressible fluid made of gravitons (photon-like particles having a wave length of the order of magnitude of the radius of universe. One considers the universe uniform at large scale, the effects of general relativity type being local and negligible at global scale. An “elastic sphere” model for the universe is suggested to describe the possible inversion. The expansion of the universe stops when the “elastic energy” overcomes the kinetic one; this takes place near the point of maximal emission speed of the fluid of gravitons. The differential equation for the universe in expansion is adapted to contraction. Analytical solutions are given.
Frontiers in Anisotropic Shock-Wave Modeling
2012-02-01
Epoxy IFPT simulated and experimental back surface velocities for 572, 788, and 1015 m/s. The experimental data Kevlar / Epoxy materials recovered after...model development for the Nextel and Kevlar / Epoxy materials subject to hypervelocity impact. They also performed the experimental inverse flyer test...IFPT) for Nextel and Kevlar / Epoxy . Their models were to be macro-mechanically based and suitable for implementation into a hydrocode coupled with EOS
Comparison of Hydrocode Simulations with Measured Shock Wave Velocities
International Nuclear Information System (INIS)
Hixson, R. S.; Veeser, L. R.
2014-01-01
We have conducted detailed 1- and 2-dimensional hydrodynamics calculations to assess the quality of simulations commonly made to understand various shock processes in a sample and to design shock experiments. We began with relatively simple shock experiments, where we examined the effects of the equation of state and the viscoplastic strength models. Eventually we included spallation in copper and iron and a solid-solid phase transformation in iron to assess the quality of the damage and phase transformation simulations.
Line profile studies of hydrodynamical models of cometary compact H II regions
International Nuclear Information System (INIS)
Zhu, Feng-Yao; Zhu, Qing-Feng
2015-01-01
We simulate the evolution of cometary H II regions based on several champagne flow models and bow shock models, and calculate the profiles of the [Ne II] fine-structure line at 12.81 μm, the H30α recombination line and the [Ne III] fine-structure line at 15.55 μm for these models at different inclinations of 0°, 30° and 60°. We find that the profiles in the bow shock models are generally different from those in the champagne flow models, but the profiles in the bow shock models with lower stellar velocity (≤ 5 km s −1 ) are similar to those in the champagne flow models. In champagne flow models, both the velocity of peak flux and the flux weighted central velocities of all three lines point outward from molecular clouds. In bow shock models, the directions of these velocities depend on the speed of stars. The central velocities of these lines are consistent with the stellar motion in the high stellar speed cases, but they are opposite directions from the stellar motion in the low speed cases. We notice that the line profiles from the slit along the symmetrical axis of the projected 2D image of these models are useful for distinguishing bow shock models from champagne flow models. It is also confirmed by the calculation that the flux weighted central velocity and the line luminosity of the [Ne III] line can be estimated from the [Ne II] line and the H30α line. (paper)
3D numerical modeling of YSO accretion shocks
Directory of Open Access Journals (Sweden)
Matsakos T.
2014-01-01
Full Text Available The dynamics of YSO accretion shocks is determined by radiative processes as well as the strength and structure of the magnetic field. A quasi-periodic emission signature is theoretically expected to be observed, but observations do not confirm any such pattern. In this work, we assume a uniform background field, in the regime of optically thin energy losses, and we study the multi-dimensional shock evolution in the presence of perturbations, i.e. clumps in the stream and an acoustic energy flux flowing at the base of the chromosphere. We perform 3D MHD simulations using the PLUTO code, modelling locally the impact of the infalling gas onto the chromosphere. We find that the structure and dynamics of the post-shock region is strongly dependent on the plasma-beta (thermal over magnetic pressure, different values of which may give distinguishable emission signatures, relevant for observations. In particular, a strong magnetic field effectively confines the plasma inside its flux tubes and leads to the formation of quasi-independent fibrils. The fibrils may oscillate out of phase and hence the sum of their contributions in the emission results in a smooth overall profile. On the contrary, a weak magnetic field is not found to have any significant effect on the shocked plasma and the turbulent hot slab that forms is found to retain its periodic signature.
Directory of Open Access Journals (Sweden)
Usama Umer
2016-05-01
Full Text Available This study aims to perform comparative analyses in modeling serrated chip morphologies using traditional finite element and smoothed particles hydrodynamics methods. Although finite element models are being employed in predicting machining performance variables for the last two decades, many drawbacks and limitations exist with the current finite element models. The problems like excessive mesh distortions, high numerical cost of adaptive meshing techniques, and need of geometric chip separation criteria hinder its practical implementation in metal cutting industries. In this study, a mesh free method, namely, smoothed particles hydrodynamics, is implemented for modeling serrated chip morphology while machining AISI H13 hardened tool steel. The smoothed particles hydrodynamics models are compared with the traditional finite element models, and it has been found that the smoothed particles hydrodynamics models have good capabilities in handling large distortions and do not need any geometric or mesh-based chip separation criterion.
An hydrodynamic model for the calculation of oil spills trajectories
Energy Technology Data Exchange (ETDEWEB)
Paladino, Emilio Ernesto; Maliska, Clovis Raimundo [Santa Catarina Univ., Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica. Lab. de Dinamica dos Fluidos Computacionais]. E-mails: emilio@sinmec.ufsc.br; maliska@sinmec.ufsc.br
2000-07-01
The aim of this paper is to present a mathematical model and its numerical treatment to forecast oil spills trajectories in the sea. The knowledge of the trajectory followed by an oil slick spilled on the sea is of fundamental importance in the estimation of potential risks for pipeline and tankers route selection, and in combating the pollution using floating barriers, detergents, etc. In order to estimate these slicks trajectories a new model, based on the mass and momentum conservation equations is presented. The model considers the spreading in the regimes when the inertial and viscous forces counterbalance gravity and takes into account the effects of winds and water currents. The inertial forces are considered for the spreading and the displacement of the oil slick, i.e., is considered its effects on the movement of the mass center of the slick. The mass loss caused by oil evaporation is also taken into account. The numerical model is developed in generalized coordinates, making the model easily applicable to complex coastal geographies. (author)
Energy Technology Data Exchange (ETDEWEB)
Lee, Shiu-Hang; Kamae, Tuneyoshi; Ellison, Donald C.
2008-07-02
We present a 3-dimensional model of supernova remnants (SNRs) where the hydrodynamical evolution of the remnant is modeled consistently with nonlinear diffusive shock acceleration occurring at the outer blast wave. The model includes particle escape and diffusion outside of the forward shock, and particle interactions with arbitrary distributions of external ambient material, such as molecular clouds. We include synchrotron emission and cooling, bremsstrahlung radiation, neutral pion production, inverse-Compton (IC), and Coulomb energy-loss. Boardband spectra have been calculated for typical parameters including dense regions of gas external to a 1000 year old SNR. In this paper, we describe the details of our model but do not attempt a detailed fit to any specific remnant. We also do not include magnetic field amplification (MFA), even though this effect may be important in some young remnants. In this first presentation of the model we don't attempt a detailed fit to any specific remnant. Our aim is to develop a flexible platform, which can be generalized to include effects such as MFA, and which can be easily adapted to various SNR environments, including Type Ia SNRs, which explode in a constant density medium, and Type II SNRs, which explode in a pre-supernova wind. When applied to a specific SNR, our model will predict cosmic-ray spectra and multi-wavelength morphology in projected images for instruments with varying spatial and spectral resolutions. We show examples of these spectra and images and emphasize the importance of measurements in the hard X-ray, GeV, and TeV gamma-ray bands for investigating key ingredients in the acceleration mechanism, and for deducing whether or not TeV emission is produced by IC from electrons or pion-decay from protons.
Darmana, D.; Deen, N.G.; Kuipers, J.A.M.
2005-01-01
A 3D discrete bubble model is adopted to investigate complex behavior involving hydrodynamics, mass transfer and chemical reactions in a gas¿liquid bubble column reactor. In this model a continuum description is adopted for the liquid phase and additionally each individual bubble is tracked in a
Darmana, D.; Deen, N.G.; Kuipers, J.A.M.
2005-01-01
A 3D discrete bubble model is adopted to investigate complex behavior involving hydrodynamics, mass transfer and chemical reactions in a gas–liquid bubble column reactor. In this model a continuum description is adopted for the liquid phase and additionally each individual bubble is tracked in a
International Nuclear Information System (INIS)
Yang, Zhaoqing; Khangaonkar, Tarang; Wang, Taiping
2010-01-01
In this report we describe the (1) the expansion of the PNNL hydrodynamic model domain to include the continental shelf along the coasts of Washington, Oregon, and Vancouver Island; and (2) the approach and progress in developing the online/Internet disseminations of model results and outreach efforts in support of the Puget Sound Operational Forecast System (PS-OPF). Submittal of this report completes the work on Task 2.1.2, Effects of Physical Systems, Subtask 2.1.2.1, Hydrodynamics, for fiscal year 2010 of the Environmental Effects of Marine and Hydrokinetic Energy project.
A hydrodynamic model for superfluid helium with vortices
International Nuclear Information System (INIS)
Lhuillier, D.; Francois, M.
1975-01-01
Although their existence is experimentally well verified, the so-called mutual friction force Fsub(sn) and superfluid friction force Fsub(s) cannot emerge from the Landau irrotational model of superfluidity. Up to now these forces have merely been added to the Landau equations but this is untenable since, as a consequence, one destroys the irrotationality condition with which the equations have expressly been built. It is shown that these friction forces appear in a natural way in a model where superfluid helium with vortices is compared to a fluid with a conserved intrinsic momentum. (Auth.)
A Full Hydrodynamic Modelling of 2D Breaker Bar Development
DEFF Research Database (Denmark)
Jacobsen, Niels Gjøl; Fredsøe, Jørgen
2011-01-01
The free surface simulation of breaking waves is studied using a combination of VOF and RANS closures. Further, a numerical model for the detailed study of sediment transport and morphological development is presented. In the present study it is applied to the case of sediment transport in the su...
Integrated hydrologic and hydrodynamic modeling to assess water exchange in a data-scarce reservoir
Wu, Binbin; Wang, Guoqiang; Wang, Zhonggen; Liu, Changming; Ma, Jianming
2017-12-01
Integrated hydrologic and hydrodynamic modeling is useful in evaluating hydrodynamic characteristics (e.g. water exchange processes) in data-scarce water bodies, however, most studies lack verification of the hydrologic model. Here, water exchange (represented by water age) was investigated through integrated hydrologic and hydrodynamic modeling of the Hongfeng Reservoir, a poorly gauged reservoir in southwest China. The performance of the hydrologic model and parameter replacement among sub-basins with hydrological similarity was verified by historical data. Results showed that hydrological similarity based on the hierarchical cluster analysis and topographic index probability density distribution was reliable with satisfactory performance of parameter replacement. The hydrodynamic model was verified using daily water levels and water temperatures from 2009 and 2010. The water exchange processes in the Hongfeng Reservoir are very complex with temporal, vertical, and spatial variations. The temporal water age was primarily controlled by the variable inflow and outflow, and the maximum and minimum ages for the site near the dam were 406.10 d (15th June) and 90.74 d (3rd August), respectively, in 2010. Distinct vertical differences in water age showed that surface flow, interflow, and underflow appeared alternately, depending on the season and water depth. The worst water exchange situation was found in the central areas of the North Lake with the highest water ages in the bottom on both 15th June and 3rd August, in 2010. Comparison of the spatial water ages revealed that the more favorable hydraulic conditions on 3rd August mainly improved the water exchange in the dam areas and most areas of the South Lake, but had little effect on the bottom layers of the other deepest areas in the South and North Lakes. The presented framework can be applied in other data-scarce waterbodies worldwide to provide better understanding of water exchange processes.
Development of hydrodynamic analysis model for IRWST/Sparger
Energy Technology Data Exchange (ETDEWEB)
Kim, Sang Nyung; Lee, Kyung Won; Yum, Sang Hoo; Yoon, Sung Sik [Kyung Hee University, Seoul (Korea)
2001-04-01
One of the design improvements of the KNGR(Korean Next Generation Reactor) which is advanced to safety and economy is the adoption of IRWST(In-Containment Refueling Water Storage Tank). The IRWST, installed inside of the containment building, has more designed purpose than merely the location change of the tank. Since the design functions of the IRWST is similar to these of the BWR's suppression pool, theoretical models applicable to BWR's suppression pool can be mostly applied to the IRWST. But for the PWR, the geometry of the sparger, the operation mode and the steam quantity and temperature and pressure of discharged fluid from primary system to IRWST through PSV or SDV may be different from those of BWR. Also there is some defects in detailed parts of condensation model. Therefore we, as the first nation to construct PWR with IRWST, must carry out profound research for there problems such that the results can be utilized and localized as an exclusive technology. To analyze steam condensation in IRWST, BWR operating experience, experimental data, design parameter of IRWST and wide range of literature review were consulted. Through the review, the point at issue in operating experience, every condensation and thermal-hydrolic phenomena in IRWST are throughly analyzed and the dominant parameters are found to be subcooled temperature and mass flow rate. This research has been understood the various theoretical and experimental models related to the phenomena and investigated the references about the concept and the design of KNGR's IRWST. The research has covered details of pipe clearing and boundary conditions, numerical method, bubble behavior and analytical method, distribution of velocity and pressure in sparger, load effect on structures, model of chugging and thermal stratification. These models were qualified for design and safety evaluation of Nuclear Power Plant. 15 refs., 22 figs., 4 tabs. (Author)
Particle force model effects in a shock-driven multiphase instability
Black, W. J.; Denissen, N.; McFarland, J. A.
2018-05-01
This work presents simulations on a shock-driven multiphase instability (SDMI) at an initial particle volume fraction of 1% with the addition of a suite of particle force models applicable in dense flows. These models include pressure-gradient, added-mass, and interparticle force terms in an effort to capture the effects neighboring particles have in non-dilute flow regimes. Two studies are presented here: the first seeks to investigate the individual contributions of the force models, while the second study focuses on examining the effect of these force models on the hydrodynamic evolution of a SDMI with various particle relaxation times (particle sizes). In the force study, it was found that the pressure gradient and interparticle forces have little effect on the instability under the conditions examined, while the added-mass force decreases the vorticity deposition and alters the morphology of the instability. The relaxation-time study likewise showed a decrease in metrics associated with the evolution of the SDMI for all sizes when the particle force models were included. The inclusion of these models showed significant morphological differences in both the particle and carrier species fields, which increased as particle relaxation times increased.
A general method for generating bathymetric data for hydrodynamic computer models
Burau, J.R.; Cheng, R.T.
1989-01-01
To generate water depth data from randomly distributed bathymetric data for numerical hydrodymamic models, raw input data from field surveys, water depth data digitized from nautical charts, or a combination of the two are sorted to given an ordered data set on which a search algorithm is used to isolate data for interpolation. Water depths at locations required by hydrodynamic models are interpolated from the bathymetric data base using linear or cubic shape functions used in the finite-element method. The bathymetric database organization and preprocessing, the search algorithm used in finding the bounding points for interpolation, the mathematics of the interpolation formulae, and the features of the automatic generation of water depths at hydrodynamic model grid points are included in the analysis. This report includes documentation of two computer programs which are used to: (1) organize the input bathymetric data; and (2) to interpolate depths for hydrodynamic models. An example of computer program operation is drawn from a realistic application to the San Francisco Bay estuarine system. (Author 's abstract)
Assessment of core thermo-hydrodynamic models of REFLA-1D with CCTF data
International Nuclear Information System (INIS)
Okubo, Tsutomu; Murao, Yoshio
1983-07-01
In order to assess the core thermo-hydrodynamic models of REFLA-1D/MODE3, which is the latest version of REFLA-1D, several calculations of the core thermo-hydrodynamics have been performed for the CCTF Core-I series tests. The measured initial and boundary conditions were used for these calculations. The calculational results showed that the water accumulation model of Case 2 could predict the CCTF results fairly well as it could for the JAERI small scale facility. The calculated results for the base case and the EM tests were in good agreement with the CCTF data. The parameter effects, such as system pressure, initial clad temperature, Acc injection rate, LPCI injection rate and initial down-comer wall temperature, were predicted correctly, except for the high system pressure and the high LPCI injection rate tests. (author)
Tang, Xian-Zhu; McDevitt, C. J.; Guo, Zehua; Berk, H. L.
2014-03-01
Inertial confinement fusion requires an imploded target in which a central hot spot is surrounded by a cold and dense pusher. The hot spot/pusher interface can take complicated shape in three dimensions due to hydrodynamic mix. It is also a transition region where the Knudsen and inverse Knudsen layer effect can significantly modify the fusion reactivity in comparison with the commonly used value evaluated with background Maxwellians. Here, we describe a hybrid model that couples the kinetic correction of fusion reactivity to global hydrodynamic implosion simulations. The key ingredient is a non-perturbative treatment of the tail ions in the interface region where the Gamow ion Knudsen number approaches or surpasses order unity. The accuracy of the coupling scheme is controlled by the precise criteria for matching the non-perturbative kinetic model to perturbative solutions in both configuration space and velocity space.
Hydrodynamic and thermal modeling of solid particles in a multi-phase, multi-component flow
International Nuclear Information System (INIS)
Tentner, A.M.; Wider, H.U.
1984-01-01
This paper presents the new thermal hydraulic models describing the hydrodynamics of the solid fuel/steel chunks during an LMFBR hypothetical core disruptive accident. These models, which account for two-way coupling between the solid and fluid phases, describe the mass, momentum and energy exchanges which occur when the chunks are present at any axial location. They have been incorporated in LEVITATE, a code for the analysis of fuel and cladding dynamics under Loss-of-Flow (LOF) conditions. Their influence on fuel motion is presented in the context of the L6 TREAT experiment analysis. It is shown that the overall hydrodynamic behavior of the molten fuel and solid fuel chunks is dependent on both the size of the chunks and the power level. At low and intermediate power levels the fuel motion is more dispersive when small chunks, rather than large ones, are present. At high power levels the situation is reversed
Combining Envisat and CryoSat-2 altimetry to inform hydrodynamic models
DEFF Research Database (Denmark)
Schneider, Raphael; Nygaard Godiksen, Peter; Ridler, Marc-Etienne
2016-01-01
fitted to the CryoSat-2 data: In a first step, the average simulated water levels along the river were calibrated to the CryoSat-2 data by adapting the hydrodynamic cross section datums. Subsequently the simulated water level amplitudes were fitted to those obtained from Envisat virtual station time......Remote sensing provides valuable data for parameterization and updating of hydrological models, for example water level measurements of inland water bodies from satellite radar altimeters. Many studies have used satellite altimetry data from repeat-orbit missions such as Envisat, ERS or Jason...... on Sentinel-3. CryoSat-2 SARIn level 2 data is used to improve a 1D hydrodynamic model of the Brahmaputra river basin in South Asia set up in the DHI MIKE 11 software. CryoSat-2 water levels were extracted over river masks derived from Landsat imagery. After discharge calibration, simulated water levels were...
Umgiesser, Georg; Razinkovas-Baziukas, Arturas; Barisevičiūtė, Ruta; Baziukė, Dalia; Ertürk, Ali; Gasiūnaitė, Jovita; Gulbinskas, Saulius; Lubienė, Irma; Maračkinaite, Jurgita; Petkuvienė, Jolita; Pilkaitytė, Renata; Ruginis, Tomas; Zemlys, Petras; Žilius, Mindaugas
2013-04-01
The spatial pattern of the hydrodynamic circulation of the Curonian lagoon, the largest European coastal lagoon, is still little understood. In absence of automatic current registration data all the existing models relied mostly on such data as water levels leaving high level of uncertainty. Here we present CISOCUR, a new project financed by the European Social Fund under the Global Grant measure. The project applies a new methodology that uses the carbon stable isotope (SI) ratio of C12 and C13 that characterize different water sources entering the lagoon and may be altered by internal kinetic processes. Through the tracing of these isotope ratios different water masses can be identified. This gives the possibility to validate several hypotheses of water circulation and validate hydrodynamic models. In particular it will be possible to 1) trace water masses entering the lagoon through the Nemunas and the Klaipeda strait; 2) test the hypothesis of sediment transport mechanisms inside the lagoon; 3) evaluate the importance of physical forcing on the lagoon circulation. The use of a hydrodynamic finite element model, coupled with the SI method, will allow for a realistic description of the transport processes inside the Curonian lagoon. So the main research goal is to apply the stable isotope tracers and a finite element model to determine the circulation patterns in the Curonian lagoon. Overall, the project will develop according to 4 main phases: 1) A pilot study to measure the isotope composition of different carbon compounds (dissolved and suspended) in different water bodies that feed water into the central lagoon. Through this pilot study the optimal study sites for the seasonal campaign will be identified as well. 2) Seasonal field campaigns in the monitoring stations identified in phase 1 to measure the carbon isotope ratio. 3) Development of a model that describes the kinetics of carbon isotopes and its transformation. 4) Application of a hydrodynamic model
A 3D Hydrodynamic Model for Heterogeneous Biofilms with Antimicrobial Persistence
2014-01-01
David A. Weitz, and Michael P. Brenner. Osmotic spreading of bacillus subtilis biofilms driven by an extracellular matrix. PNAS, 2012. [38] Zhiya...Currently, the environmental impact of biocide or side-effect of antibiotics have become common concerns, which makes the derivation of an optimal...biofilms to penetration of antibiotics . To our best knowledge, there has yet been a mathematical model which takes into account both the hydrodynamic
A Tightly Coupled Non-Equilibrium Magneto-Hydrodynamic Model for Inductively Coupled RF Plasmas
2016-02-29
development a tightly coupled magneto-hydrodynamic model for Inductively Coupled Radio- Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE...for Inductively Coupled Radio-Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE) effects are described based on a hybrid State-to-State...Inductively Coupled Plasma (ICP) torches have wide range of possible applications which include deposition of metal coatings, synthesis of ultra-fine powders
The use of hydro-dynamic models in the practice-oriented education of engineering students
Sziebert, J.; Zellei, L.; Tamás, E. A.
2009-04-01
Management tasks related to open channel flows became rather comprehensive and multi-disciplinary, particularly with the predominancy of nature management aspects. The water regime of our rivers has proven to reach extremities more and more frequently in the past decades. In order to develop and analyse alternative solutions and to handle and resolve conflicts of interests, we apply 1D hydro-dynamic models in education for the explanation of processes and to improve practical skills of our students.
Energy Technology Data Exchange (ETDEWEB)
Christillin, P [Scuola Normale Superiore, Pisa (Italy); Lipparini, E; Stringari, S [Dipartimento Matematica e Fisica, Trento, Italy
1978-09-25
A sum-rule approach is used to study the influence of surface thickness upon the splitting of dipole and isoscalar quadrupole energies in deformed nuclei. It is shown that hydrodynamic model results are recovered in the case of a deformed skin thickness. A constant skin thickness leads in the dipole case to slightly different predictions which seem in better agreement with experiments. The splitting of the isoscalar quadrupole mode is not sensitive to the surface thickness shape.
International Nuclear Information System (INIS)
Klotz, D.; Moser, H.
1980-01-01
The object of the research project is to assess the hydrodynamic dispersion of labelling material solutions in special ground water lines based on measurements of the ground water flow rate and on the sedimentological properties of the natural ground water line present. The investigations were carried out in the laboratory in a three-dimensional ground water flow model and in column systems with HTO as tracer. (orig./HP) [de
Determination of Volumetric Losses in Hydrodynamic Pump Using Numerical Modelling
Directory of Open Access Journals (Sweden)
Lukáš ZAVADIL
2012-06-01
Full Text Available This paper deals with the numerical modelling of the flow in the single-stage centrifugal pump. The main objective is to determine leakage losses through annular seals at the suction side of the pump. Leakage through a shaft seal is not included in the simulation. The amount of liquid that circulates from the impeller discharge back to suction of the pump is determined in dependence on the flow rate. Losses in the pump are further discussed as well as the possibility of their prediction.
Deschutes estuary feasibility study: hydrodynamics and sediment transport modeling
George, Douglas A.; Gelfenbaum, Guy; Lesser, Giles; Stevens, Andrew W.
2006-01-01
Continual sediment accumulation in Capitol Lake since the damming of the Deschutes River in 1951 has altered the initial morphology of the basin. As part of the Deschutes River Estuary Feasibility Study (DEFS), the United States Geological Survey (USGS) was tasked to model how tidal and storm processes will influence the river, lake and lower Budd Inlet should estuary restoration occur. Understanding these mechanisms will assist in developing a scientifically sound assessment on the feasibility of restoring the estuary. The goals of the DEFS are as follows. - Increase understanding of the estuary alternative to the same level as managing the lake environment.
Electrochemo-hydrodynamics modeling approach for a uranium electrowinning cell
Energy Technology Data Exchange (ETDEWEB)
Kim, K.R.; Paek, S.; Ahn, D.H., E-mail: krkim1@kaeri.re.kr, E-mail: swpaek@kaeri.re.kr, E-mail: dhahn2@kaeri.re.kr [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, J.Y.; Hwang, I.S., E-mail: d486916@snu.ac.kr, E-mail: hisline@snu.ac.kr [Department of Nuclear Engineering, Seoul National University (Korea, Republic of)
2011-07-01
This study demonstrated a simulation based on fully coupling of electrochemical kinetics with 3- dimensional transport of ionic species in a flowing molten-salt electrolyte through a simplified channel cell of uranium electro winner. Dependences of ionic electro-transport on the velocity of stationary electrolyte flow were studied using a coupling approach of electrochemical reaction model. The present model was implemented in a commercially available computational fluid dynamics (CFD) platform, Ansys-CFX, using its customization ability via user defined functions. The main parameters characterizing the effect of the turbulent flow of an electrolyte between two planar electrodes were demonstrated by means of CFD-based multiphysics simulation approach. Simulation was carried out for the case of uranium electrowinning characteristics in a stream of molten salt electrolyte. This approach was taken into account the concentration profile at the electrode surface, to represent the variation of the diffusion limited current density as a function of the flow characteristics and of applied current density. It was able to predict conventional current voltage relation in addition to details of electrolyte fluid dynamics and electrochemical variable, such as flow field, species concentrations, potential, and current distributions throughout the current driven cell. (author)
Electrochemo-hydrodynamics modeling approach for a uranium electrowinning cell
International Nuclear Information System (INIS)
Kim, K.R.; Paek, S.; Ahn, D.H.; Park, J.Y.; Hwang, I.S.
2011-01-01
This study demonstrated a simulation based on fully coupling of electrochemical kinetics with 3- dimensional transport of ionic species in a flowing molten-salt electrolyte through a simplified channel cell of uranium electro winner. Dependences of ionic electro-transport on the velocity of stationary electrolyte flow were studied using a coupling approach of electrochemical reaction model. The present model was implemented in a commercially available computational fluid dynamics (CFD) platform, Ansys-CFX, using its customization ability via user defined functions. The main parameters characterizing the effect of the turbulent flow of an electrolyte between two planar electrodes were demonstrated by means of CFD-based multiphysics simulation approach. Simulation was carried out for the case of uranium electrowinning characteristics in a stream of molten salt electrolyte. This approach was taken into account the concentration profile at the electrode surface, to represent the variation of the diffusion limited current density as a function of the flow characteristics and of applied current density. It was able to predict conventional current voltage relation in addition to details of electrolyte fluid dynamics and electrochemical variable, such as flow field, species concentrations, potential, and current distributions throughout the current driven cell. (author)
Comparisons of Air Radiation Model with Shock Tube Measurements
Bose, Deepak; McCorkle, Evan; Bogdanoff, David W.; Allen, Gary A., Jr.
2009-01-01
This paper presents an assessment of the predictive capability of shock layer radiation model appropriate for NASA s Orion Crew Exploration Vehicle lunar return entry. A detailed set of spectrally resolved radiation intensity comparisons are made with recently conducted tests in the Electric Arc Shock Tube (EAST) facility at NASA Ames Research Center. The spectral range spanned from vacuum ultraviolet wavelength of 115 nm to infrared wavelength of 1400 nm. The analysis is done for 9.5-10.5 km/s shock passing through room temperature synthetic air at 0.2, 0.3 and 0.7 Torr. The comparisons between model and measurements show discrepancies in the level of background continuum radiation and intensities of atomic lines. Impurities in the EAST facility in the form of carbon bearing species are also modeled to estimate the level of contaminants and their impact on the comparisons. The discrepancies, although large is some cases, exhibit order and consistency. A set of tests and analyses improvements are proposed as forward work plan in order to confirm or reject various proposed reasons for the observed discrepancies.
Hydrodynamic Modeling Analysis to Support Nearshore Restoration Projects in a Changing Climate
Directory of Open Access Journals (Sweden)
Zhaoqing Yang
2014-01-01
Full Text Available To re-establish the intertidal wetlands with full tidal exchange and improve salmonid rearing habitat in the Skagit River estuary, State of Washington, USA, a diked agriculture farm land along the Skagit Bay front is proposed to be restored to a fully functional tidal wetland. The complex and dynamic Skagit River estuarine system calls for the need of a multi-facet and multi-dimensional analysis using observed data, numerical and analytical methods. To assist the feasibility study of the restoration project, a hydrodynamic modeling analysis was conducted using a high-resolution unstructured-grid coastal ocean model to evaluate the hydrodynamic response to restoration alternatives and to provide guidance to the engineering design of a new levee in the restoration site. A set of parameters were defined to quantify the hydrodynamic response of the nearshore restoration project, such as inundation area, duration of inundation, water depth and salinity of the inundated area. To assist the design of the new levee in the restoration site, the maximum water level near the project site was estimated with consideration of extreme high tide, wind-induced storm surge, significant wave height and future sea-level rise based on numerical model results and coastal engineering calculation.
International Nuclear Information System (INIS)
Merdeev, A. V.; Satarov, L. M.; Mishustin, I. N.
2011-01-01
We use (3 + 1) dimensional ideal hydrodynamics to describe the space-time evolution of strongly interacting matter created in Au + Au and Pb + Pb collisions. The model is applied for the domain of bombarding energies 1-160 GeV/nucleon which includes future NICA (Dubna) and FAIR (Darmstadt) experiments. Two equations of state are used, the first one corresponding to resonance hadron gas and the second one including the deconfinement phase transition. The initial state is represented by two Lorentz-boosted nuclei. Dynamic trajectories of matter in the central box of the system are analyzed. They can be well represented by a fast shock-wave compression followed by a relatively slow isentropic expansion. The parameters of collective flows and hadronic spectra are calculated under assumption of the isochronous freeze-out. It is shown that the deconfinement phase transition leads to broadening of proton rapidity distributions, increase of elliptic flows, and formation of the directed antiflow in the central rapidity region. These effects are most pronounced at bombarding energies around 10 GeV/nucleon, when the system spends the longest time in the mixed phase. From the comparison with three-fluid calculations we conclude that the transparency effects are not so important in central collisions at NICA-FAIR energies (below 30 GeV/nucleon).
Wang, Yunong; Ge, Hongxia; Cheng, Rongjun
2017-11-01
In this paper, a lattice hydrodynamic model is derived considering the delayed-feedback control influence of optimal flux for forward looking sites on a single-lane road which includes more comprehensive information. The control method is used to analyze the stability of the model. The critical condition for the linear steady traffic flow is deduced and the numerical simulation is carried out to investigate the advantage of the proposed model with and without the effect of optimal flux for forward looking sites. Moreover it indicates that the characteristic of the model can lead to a lower energy consumption in traffic system. The results are consistent with the theoretical analysis correspondingly.
Djordjević, Tijana; Radović, Ivan; Despoja, Vito; Lyon, Keenan; Borka, Duško; Mišković, Zoran L
2018-01-01
We present an analytical modeling of the electron energy loss (EEL) spectroscopy data for free-standing graphene obtained by scanning transmission electron microscope. The probability density for energy loss of fast electrons traversing graphene under normal incidence is evaluated using an optical approximation based on the conductivity of graphene given in the local, i.e., frequency-dependent form derived by both a two-dimensional, two-fluid extended hydrodynamic (eHD) model and an ab initio method. We compare the results for the real and imaginary parts of the optical conductivity in graphene obtained by these two methods. The calculated probability density is directly compared with the EEL spectra from three independent experiments and we find very good agreement, especially in the case of the eHD model. Furthermore, we point out that the subtraction of the zero-loss peak from the experimental EEL spectra has a strong influence on the analytical model for the EEL spectroscopy data. Copyright © 2017 Elsevier B.V. All rights reserved.
Two-phase electro-hydrodynamic flow modeling by a conservative level set model.
Lin, Yuan
2013-03-01
The principles of electro-hydrodynamic (EHD) flow have been known for more than a century and have been adopted for various industrial applications, for example, fluid mixing and demixing. Analytical solutions of such EHD flow only exist in a limited number of scenarios, for example, predicting a small deformation of a single droplet in a uniform electric field. Numerical modeling of such phenomena can provide significant insights about EHDs multiphase flows. During the last decade, many numerical results have been reported to provide novel and useful tools of studying the multiphase EHD flow. Based on a conservative level set method, the proposed model is able to simulate large deformations of a droplet by a steady electric field, which is beyond the region of theoretic prediction. The model is validated for both leaky dielectrics and perfect dielectrics, and is found to be in excellent agreement with existing analytical solutions and numerical studies in the literature. Furthermore, simulations of the deformation of a water droplet in decyl alcohol in a steady electric field match better with published experimental data than the theoretical prediction for large deformations. Therefore the proposed model can serve as a practical and accurate tool for simulating two-phase EHD flow. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
A combined N-body and hydrodynamic code for modeling disk galaxies
International Nuclear Information System (INIS)
Schroeder, M.C.
1989-01-01
A combined N-body and hydrodynamic computer code for the modeling of two dimensional galaxies is described. The N-body portion of the code is used to calculate the motion of the particle component of a galaxy, while the hydrodynamics portion of the code is used to follow the motion and evolution of the fluid component. A complete description of the numerical methods used for each portion of the code is given. Additionally, the proof tests of the separate and combined portions of the code are presented and discussed. Finally, a discussion of the topics researched with the code and results obtained is presented. These include: the measurement of stellar relaxation times in disk galaxy simulations; the effects of two-armed spiral perturbations on stable axisymmetric disks; the effects of the inclusion of an instellar medium (ISM) on the stability of disk galaxies; and the effect of the inclusion of stellar evolution on disk galaxy simulations
Event-plane dependent di-hadron correlations with harmonic vn subtraction in a hydrodynamic model
Castilho, Wagner M.; Qian, Wei-Liang; Hama, Yogiro; Kodama, Takeshi
2018-02-01
In this work, a hydrodynamic study of the di-hadron azimuthal correlations for the Au+Au collisions at 200 GeV is carried out. The correlations are evaluated using the ZYAM method for the centrality windows as well as the transverse momentum range in accordance with the existing data. Event-plane dependence of the correlation is obtained after the subtraction of contributions from the most dominant harmonic coefficients. In particular, the contribution from the triangular flow, v3, is removed from the proper correlations following the procedure implemented by the STAR collaboration. The resultant structure observed in the correlations was sometimes attributed to the mini-jet dynamics, but the present calculations show that a pure hydrodynamic model gives a reasonable agreement with the main feature of the published data. A brief discussion on the physical content of the present findings is presented.
Integrable hydrodynamics of Calogero-Sutherland model: bidirectional Benjamin-Ono equation
International Nuclear Information System (INIS)
Abanov, Alexander G; Bettelheim, Eldad; Wiegmann, Paul
2009-01-01
We develop a hydrodynamic description of the classical Calogero-Sutherland liquid: a Calogero-Sutherland model with an infinite number of particles and a non-vanishing density of particles. The hydrodynamic equations, being written for the density and velocity fields of the liquid, are shown to be a bidirectional analog of the Benjamin-Ono equation. The latter is known to describe internal waves of deep stratified fluids. We show that the bidirectional Benjamin-Ono equation appears as a real reduction of the modified KP hierarchy. We derive the chiral nonlinear equation which appears as a chiral reduction of the bidirectional equation. The conventional Benjamin-Ono equation is a degeneration of the chiral nonlinear equation at large density. We construct multi-phase solutions of the bidirectional Benjamin-Ono equations and of the chiral nonlinear equations
Li, Longqiu; Wang, Jiyuan; Li, Tianlong; Song, Wenping; Zhang, Guangyu
2014-10-14
The hydrodynamic behavior and propulsion mechanism of self-propelled micromotors are studied theoretically and experimentally. A hydrodynamic model to describe bubble growth and detachment is proposed to investigate the mechanism of a self-propelled conical tubular catalytic micromotor considering bubble geometric asymmetry and buoyancy force. The growth force caused by the growth of the bubble surface against the fluid is the driving force for micromotor motion. Also, the buoyancy force plays a primary role in bubble detachment. The effect of geometrical parameters on the micromotor velocity and drag force is presented. The bubble radius ratio is investigated for different micromotor radii to determine its hydrodynamic behavior during bubble ejection. The average micromotor velocity is found to be strongly dependent on the semi-cone angle, expelling frequency and bubble radius ratio. The semi-cone angle has a significant effect on the expelling frequency for conical tubular micromotors. The predicted results are compared to already existing experimental data for cylindrical micromotors (semi-cone angle δ = 0°) and conical micromotors. A good agreement is found between the theoretical calculation and experimental results. This model provides a profound explanation for the propulsion mechanism of a catalytic micromotor and can be used to optimize the micromotor design for its biomedical and environmental applications.
Conceptual Site Model for Newark Bay—Hydrodynamics and Sediment Transport
Directory of Open Access Journals (Sweden)
Parmeshwar L. Shrestha
2014-02-01
Full Text Available A conceptual site model (CSM has been developed for the Newark Bay Study Area (NBSA as part of the Remedial Investigation/Feasibility Study (RI/FS for this New Jersey site. The CSM is an evolving document that describes the influence of physical, chemical and biological processes on contaminant fate and transport. The CSM is initiated at the start of a project, updated during site activities, and used to inform sampling and remediation planning. This paper describes the hydrodynamic and sediment transport components of the CSM for the NBSA. Hydrodynamic processes are influenced by freshwater inflows, astronomical forcing through two tidal straits, meteorological conditions, and anthropogenic activities such as navigational dredging. Sediment dynamics are driven by hydrodynamics, waves, sediment loading from freshwater sources and the tidal straits, sediment size gradation, sediment bed properties, and particle-to-particle interactions. Cohesive sediment transport is governed by advection, dispersion, aggregation, settling, consolidation, and erosion. Noncohesive sediment transport is governed by advection, dispersion, settling, armoring, and transport in suspension and along the bed. The CSM will inform the development and application of a numerical model that accounts for all key variables to adequately describe the NBSA’s historical, current, and future physical conditions.
Digital Repository Service at National Institute of Oceanography (India)
Balachandran, K.K.; Reddy, G.S.; Revichandran, C.; Srinivas, K.; Vijayan, P.R.; Thottam, T.J.
Tidal circulation in the Cochin Estuary, a moderately polluted estuary along the southwest coast of India, was studied using a 2D hydrodynamic model. The predicted tides and currents showed very good agreement with measured tides. Particle...
Calibration of HEC-Ras hydrodynamic model using gauged discharge data and flood inundation maps
Tong, Rui; Komma, Jürgen
2017-04-01
The estimation of flood is essential for disaster alleviation. Hydrodynamic models are implemented to predict the occurrence and variance of flood in different scales. In practice, the calibration of hydrodynamic models aims to search the best possible parameters for the representation the natural flow resistance. Recent years have seen the calibration of hydrodynamic models being more actual and faster following the advance of earth observation products and computer based optimization techniques. In this study, the Hydrologic Engineering River Analysis System (HEC-Ras) model was set up with high-resolution digital elevation model from Laser scanner for the river Inn in Tyrol, Austria. 10 largest flood events from 19 hourly discharge gauges and flood inundation maps were selected to calibrate the HEC-Ras model. Manning roughness values and lateral inflow factors as parameters were automatically optimized with the Shuffled complex with Principal component analysis (SP-UCI) algorithm developed from the Shuffled Complex Evolution (SCE-UA). Different objective functions (Nash-Sutcliffe model efficiency coefficient, the timing of peak, peak value and Root-mean-square deviation) were used in single or multiple way. It was found that the lateral inflow factor was the most sensitive parameter. SP-UCI algorithm could avoid the local optimal and achieve efficient and effective parameters in the calibration of HEC-Ras model using flood extension images. As results showed, calibration by means of gauged discharge data and flood inundation maps, together with objective function of Nash-Sutcliffe model efficiency coefficient, was very robust to obtain more reliable flood simulation, and also to catch up with the peak value and the timing of peak.
Stark, J.; Smolders, S.; Meire, P.; Temmerman, S.
2017-11-01
Marsh restoration projects are nowadays being implemented as ecosystem-based strategies to reduce flood risks and to restore intertidal habitat along estuaries. Changes in estuarine tidal hydrodynamics are expected along with such intertidal area changes. A validated hydrodynamic model of the Scheldt Estuary is used to gain fundamental insights in the role of intertidal area characteristics on tidal hydrodynamics and tidal asymmetry in particular through several geomorphological scenarios in which intertidal area elevation and location along the estuary is varied. Model results indicate that the location of intertidal areas and their storage volume relative to the local tidal prism determine the intensity and reach along the estuary over which tidal hydrodynamics are affected. Our model results also suggest that intertidal storage areas that are located within the main estuarine channel system, and hence are part of the flow-carrying part of the estuary, may affect tidal hydrodynamics differently than intertidal areas that are side-basins of the main estuarine channel, and hence only contribute little to the flow-carrying cross-section of the estuary. If tidal flats contribute to the channel cross-section and exert frictional effects on the tidal propagation, the elevation of intertidal flats influences the magnitude and direction of tidal asymmetry along estuarine channels. Ebb-dominance is most strongly enhanced if tidal flats are around mean sea level or slightly above. Conversely, flood-dominance is enhanced if the tidal flats are situated low in the tidal frame. For intertidal storage areas at specific locations besides the main channel, flood-dominance in the estuary channel peaks in the vicinity of those areas and generally reduces upstream and downstream compared to a reference scenario. Finally, the model results indicate an along-estuary varying impact on the tidal prism as a result of adding intertidal storage at a specific location. In addition to known
Nucleosynthesis and hydrodynamic instabilities in core collapse supernovae
International Nuclear Information System (INIS)
Kifonidis, K.
2001-01-01
Hydrodynamic instabilities are of crucial importance for the explosion of massive stars as core collapse supernovae, for the synthesis of the heavy elements, and for their injection into the interstellar medium. The processes hereby involved are studied by means of two-dimensional hydrodynamic simulations which follow all phases from shock revival to shock breakout through the photosphere of a massive star. The computed distributions of radioactive elements are compared to observational data of SN 1987 A and other supernovae. While we find good agreement of our models with observations of Type Ib supernovae, the high velocities of iron group elements observed in SN 1987 A cannot be reproduced. Possible reasons for this discrepancy are discussed. Hydrodynamic instabilities are of crucial importance for the explosion of massive stars as core collapse supernovae, for the synthesis of the heavy elements, and for their injection into the interstellar medium. The processes hereby involved are studied by means of two-dimensional hydrodynamic simulations which follow all phases from shock revival to shock breakout through the photosphere of a massive star. The computed distributions of radioactive elements are compared to observational data of SN 1987 A and other supernovae. While we find good agreement of our models with observations of Type Ib supernovae, the high velocities of iron group elements observed in SN 1987 A cannot be reproduced. Possible reasons for this discrepancy are discussed
Wang, Yunong; Cheng, Rongjun; Ge, Hongxia
2017-08-01
In this paper, a lattice hydrodynamic model is derived considering not only the effect of flow rate difference but also the delayed feedback control signal which including more comprehensive information. The control method is used to analyze the stability of the model. Furthermore, the critical condition for the linear steady traffic flow is deduced and the numerical simulation is carried out to investigate the advantage of the proposed model with and without the effect of flow rate difference and the control signal. The results are consistent with the theoretical analysis correspondingly.
Modelling hydrologic and hydrodynamic processes in basins with large semi-arid wetlands
Fleischmann, Ayan; Siqueira, Vinícius; Paris, Adrien; Collischonn, Walter; Paiva, Rodrigo; Pontes, Paulo; Crétaux, Jean-François; Bergé-Nguyen, Muriel; Biancamaria, Sylvain; Gosset, Marielle; Calmant, Stephane; Tanimoun, Bachir
2018-06-01
Hydrological and hydrodynamic models are core tools for simulation of large basins and complex river systems associated to wetlands. Recent studies have pointed towards the importance of online coupling strategies, representing feedbacks between floodplain inundation and vertical hydrology. Especially across semi-arid regions, soil-floodplain interactions can be strong. In this study, we included a two-way coupling scheme in a large scale hydrological-hydrodynamic model (MGB) and tested different model structures, in order to assess which processes are important to be simulated in large semi-arid wetlands and how these processes interact with water budget components. To demonstrate benefits from this coupling over a validation case, the model was applied to the Upper Niger River basin encompassing the Niger Inner Delta, a vast semi-arid wetland in the Sahel Desert. Simulation was carried out from 1999 to 2014 with daily TMPA 3B42 precipitation as forcing, using both in-situ and remotely sensed data for calibration and validation. Model outputs were in good agreement with discharge and water levels at stations both upstream and downstream of the Inner Delta (Nash-Sutcliffe Efficiency (NSE) >0.6 for most gauges), as well as for flooded areas within the Delta region (NSE = 0.6; r = 0.85). Model estimates of annual water losses across the Delta varied between 20.1 and 30.6 km3/yr, while annual evapotranspiration ranged between 760 mm/yr and 1130 mm/yr. Evaluation of model structure indicated that representation of both floodplain channels hydrodynamics (storage, bifurcations, lateral connections) and vertical hydrological processes (floodplain water infiltration into soil column; evapotranspiration from soil and vegetation and evaporation of open water) are necessary to correctly simulate flood wave attenuation and evapotranspiration along the basin. Two-way coupled models are necessary to better understand processes in large semi-arid wetlands. Finally, such coupled
Shock Absorbers Multi-Modeling and Suspension Optimization
Directory of Open Access Journals (Sweden)
LUPU Ciprian
2013-05-01
Full Text Available The standard dampers used by more 90% of vehicles have damping coefficients constant along stroke, so they can’t solve simultaneous all of them, situation solving practically using a relative dampingcoefficient able to made compromise between them. This paper design and simulation testing multi-models of two types of Damp (DSA and VZN. To compare the two types of suspension they are simulated in various road and load conditions. Analysis of simulation results is presente a new VZN shock absorber. This is an invention of the Institute of Mechanics of the Romanian Academy, and patented at European and U.S. [1], [2]. This is Called VZN shock absorber, iscoming from Variable Zeta Necessary acronym, for well moving in all road and load Conditions, Where zeta Represents the relative damping, Which is Adjusted automatically, stepwise, According to the piston positions [3,4,5]. Suspension systems are used in all air and ground transportation to protect that building transportation and cargo transported around against shocks and vibrations induced in the systemfrom the road Modifying damping coefficients (Zeta function piston position, being correlated with vehicle load and road unevenness.
Dascalescu, A. E.; Lazaroiu, G.; Scupi, A. A.; Oanta, E.
2016-08-01
The rotating half-bridge of a settling tank is employed to sweep the sludge from the wastewater and to vacuum and sent it to the central collector. It has a complex geometry but the main beam may be considered a slender bar loaded by the following category of forces: concentrated forces produced by the weight of the scrapping system of blades, suction pipes, local sludge collecting chamber, plus the sludge in the horizontal sludge transporting pipes; forces produced by the access bridge; buoyant forces produced by the floating barrels according to Archimedes’ principle; distributed forces produced by the weight of the main bridge; hydrodynamic forces. In order to evaluate the hydrodynamic loads we have conceived a numerical model based on the finite volume method, using the ANSYS-Fluent software. To model the flow we used the equations of Reynolds Averaged Navier-Stokes (RANS) for liquids together with Volume of Fluid model (VOF) for multiphase flows. For turbulent model k-epsilon we used the equation for turbulent kinetic energy k and dissipation epsilon. These results will be used to increase the accuracy of the loads’ sub-model in the theoretical models, e. the finite element model and the analytical model.
Modeling shock waves in an ideal gas: combining the Burnett approximation and Holian's conjecture.
He, Yi-Guang; Tang, Xiu-Zhang; Pu, Yi-Kang
2008-07-01
We model a shock wave in an ideal gas by combining the Burnett approximation and Holian's conjecture. We use the temperature in the direction of shock propagation rather than the average temperature in the Burnett transport coefficients. The shock wave profiles and shock thickness are compared with other theories. The results are found to agree better with the nonequilibrium molecular dynamics (NEMD) and direct simulation Monte Carlo (DSMC) data than the Burnett equations and the modified Navier-Stokes theory.
Modeling of hydrodynamics in hollow fiber membrane bioreactor for mammalian cells cultivation
Directory of Open Access Journals (Sweden)
N. V. Menshutina
2016-01-01
Full Text Available The mathematical modelling in CFD-packages are powerfull instrument for design and calculation of any engineering tasks. CFD-package contains the set of programs that allow to model the different objects behavior based on the mathematical lows. ANSYS Fluent are widely used for modelling of biotechnological and chemical-technological processes. This package is convenient to describe their hydrodynamics. As cell cultivation is one of the actual scientific direction in modern biotechnology ANSYS Fluent was used to create the model of hollow fiber membrane bioreactor. The fibers are hollow cylindrical membrane to be used for cell cultivation. The criterion of process effectiveness for cell growth is full filling of the membrane surface by cells in the bioreactor. While the cell growth the fiber permeability is decreased which effects to feed flow through membrane pores. The specific feature of this process is to ensure such feed flow to deliver the optimal nutrition for the cells on the external membrane surface. The velocity distribution inside the fiber and in all bioreactor as a whole has been calculated based on mass an impulse conservation equations taking into account the mathematical model assumptions. The hydrodynamics analysis in hollow fiber membrane bioreactor is described by the three-dimensional model created in ANSYS Fluent. The specific features of one membrane model are considered and for whole bioreactor too.
Optimization of a Two-Fluid Hydrodynamic Model of Churn-Turbulent Flow
Energy Technology Data Exchange (ETDEWEB)
Donna Post Guillen
2009-07-01
A hydrodynamic model of two-phase, churn-turbulent flows is being developed using the computational multiphase fluid dynamics (CMFD) code, NPHASE-CMFD. The numerical solutions obtained by this model are compared with experimental data obtained at the TOPFLOW facility of the Institute of Safety Research at the Forschungszentrum Dresden-Rossendorf. The TOPFLOW data is a high quality experimental database of upward, co-current air-water flows in a vertical pipe suitable for validation of computational fluid dynamics (CFD) codes. A five-field CMFD model was developed for the continuous liquid phase and four bubble size groups using mechanistic closure models for the ensemble-averaged Navier-Stokes equations. Mechanistic models for the drag and non-drag interfacial forces are implemented to include the governing physics to describe the hydrodynamic forces controlling the gas distribution. The closure models provide the functional form of the interfacial forces, with user defined coefficients to adjust the force magnitude. An optimization strategy was devised for these coefficients using commercial design optimization software. This paper demonstrates an approach to optimizing CMFD model parameters using a design optimization approach. Computed radial void fraction profiles predicted by the NPHASE-CMFD code are compared to experimental data for four bubble size groups.
International Nuclear Information System (INIS)
Swift, D.C.; Paisley, Dennis L.; Kyrala, George A.; Hauer, Allan
2002-01-01
Ab initio quantum mechanics was used to construct a thermodynamically complete and rigorous equation of state for beryllium in the hexagonal and body-centred cubic structures, and to predict elastic constants as a function of compression. The equation of state agreed well with Hugoniot data and previously-published equations of state, but the temperatures were significantly different. The hexagonal/bcc phase boundary agreed reasonably well with published data, suggesting that the temperatures in our new equation of state were accurate. Shock waves were induced in single crystals and polycrystalline foils of beryllium, by direct illumination using the TRIDENT laser at Los Alamos. The velocity history at the surface of the sample was measured using a line-imaging VISAR, and transient X-ray diffraction (TXD) records were obtained with a plasma backlighter and X-ray streak cameras. The VISAR records exhibited elastic precursors, plastic waves, phase changes and spall. Dual TXD records were taken, in Bragg and Laue orientations. The Bragg lines moved in response to compression in the uniaxial direction. Because direct laser drive was used, the results had to be interpreted with the aid of radiation hydrodynamics simulations to predict the loading history for each laser pulse. In the experiments where there was evidence of polymorphism in the VISAR record, additional lines appeared in the Bragg and Laue records. The corresponding pressures were consistent with the phase boundary predicted by the quantum mechanical equation of state for beryllium. A model of the response of a single crystal of beryllium to shock loading is being developed using these new theoretical and experimental results. This model will be used in meso-scale studies of the response of the microstructure, allowing us to develop a more accurate representation of the behaviour of polycrystalline beryllium.
A new lattice hydrodynamic traffic flow model with a consideration of multi-anticipation effect
International Nuclear Information System (INIS)
Tian Chuan; Sun Di-Hua; Yang Shu-Hong
2011-01-01
We present a new multi-anticipation lattice hydrodynamic model based on the traffic anticipation effect in the real world. Applying the linear stability theory, we obtain the linear stability condition of the model. Through nonlinear analysis, we derive the modified Korteweg-de Vries equation to describe the propagating behaviour of a traffic density wave near the critical point. The good agreement between the simulation results and the analytical results shows that the stability of traffic flow can be enhanced when the multi-anticipation effect is considered. (interdisciplinary physics and related areas of science and technology)
Hydrodynamic model for 2D degenerate free-electron gas for arbitrary frequencies
Castillo, M D; Cocoletzi, G H
2003-01-01
Following Halevi's procedure for 3D degenerate free-electron gas (3D-DEG), we investigate the response function in the hydrodynamic model (HM) for 2D-DEG confined in low dimensional systems when collisions are included. For small wave vectors we found from the two- dimensional Boltzmann-Mermin model a useful expression for the HM complex stiffness parameter of the nonlocal dielectric function beta, which is beta = [((3 omega/ 4) + i(v/ 2)) / (w + iv)]v sub F , where omega and v are the circular and collisional frequencies and v sub F is the Fermi velocity. (Author)
Hydrodynamic modelling and global datasets: Flow connectivity and SRTM data, a Bangkok case study.
Trigg, M. A.; Bates, P. B.; Michaelides, K.
2012-04-01
The rise in the global interconnected manufacturing supply chains requires an understanding and consistent quantification of flood risk at a global scale. Flood risk is often better quantified (or at least more precisely defined) in regions where there has been an investment in comprehensive topographical data collection such as LiDAR coupled with detailed hydrodynamic modelling. Yet in regions where these data and modelling are unavailable, the implications of flooding and the knock on effects for global industries can be dramatic, as evidenced by the recent floods in Bangkok, Thailand. There is a growing momentum in terms of global modelling initiatives to address this lack of a consistent understanding of flood risk and they will rely heavily on the application of available global datasets relevant to hydrodynamic modelling, such as Shuttle Radar Topography Mission (SRTM) data and its derivatives. These global datasets bring opportunities to apply consistent methodologies on an automated basis in all regions, while the use of coarser scale datasets also brings many challenges such as sub-grid process representation and downscaled hydrology data from global climate models. There are significant opportunities for hydrological science in helping define new, realistic and physically based methodologies that can be applied globally as well as the possibility of gaining new insights into flood risk through analysis of the many large datasets that will be derived from this work. We use Bangkok as a case study to explore some of the issues related to using these available global datasets for hydrodynamic modelling, with particular focus on using SRTM data to represent topography. Research has shown that flow connectivity on the floodplain is an important component in the dynamics of flood flows on to and off the floodplain, and indeed within different areas of the floodplain. A lack of representation of flow connectivity, often due to data resolution limitations, means
Hydrodynamic Cucker-Smale model with normalized communication weights and time delay
Choi, Young-Pil
2017-07-17
We study a hydrodynamic Cucker-Smale-type model with time delay in communication and information processing, in which agents interact with each other through normalized communication weights. The model consists of a pressureless Euler system with time delayed non-local alignment forces. We resort to its Lagrangian formulation and prove the existence of its global in time classical solutions. Moreover, we derive a sufficient condition for the asymptotic flocking behavior of the solutions. Finally, we show the presence of a critical phenomenon for the Eulerian system posed in the spatially one-dimensional setting.
A Comparison Between Measured and Predicted Hydrodynamic Damping for a Jack-Up Rig Model
DEFF Research Database (Denmark)
Laursen, Thomas; Rohbock, Lars; Jensen, Jørgen Juncher
1996-01-01
An extensive set of measurements funded by the EU project Large Scale Facilities Program has been carried out on a model of a jack-up rig at the Danish Hydraulic Institute. The test serieswere conducted by MSC and include determination of base shears and overturning moments in both regular...... methods.In the comparison between the model test results and the theoretical predictions, thehydro-dynamic damping proves to be the most important uncertain parameter. It is shown thata relative large hydrodynamic damping must be assumed in the theoretical calculations in orderto predict the measured...
Algebraic Traveling Wave Solutions of a Non-local Hydrodynamic-type Model
International Nuclear Information System (INIS)
Chen, Aiyong; Zhu, Wenjing; Qiao, Zhijun; Huang, Wentao
2014-01-01
In this paper we consider the algebraic traveling wave solutions of a non-local hydrodynamic-type model. It is shown that algebraic traveling wave solutions exist if and only if an associated first order ordinary differential system has invariant algebraic curve. The dynamical behavior of the associated ordinary differential system is analyzed. Phase portraits of the associated ordinary differential system is provided under various parameter conditions. Moreover, we classify algebraic traveling wave solutions of the model. Some explicit formulas of smooth solitary wave and cuspon solutions are obtained
International Nuclear Information System (INIS)
Müller, Bernhard; Janka, Hans-Thomas; Marek, Andreas
2013-01-01
We present a detailed theoretical analysis of the gravitational wave (GW) signal of the post-bounce evolution of core-collapse supernovae (SNe), employing for the first time relativistic, two-dimensional explosion models with multi-group, three-flavor neutrino transport based on the ray-by-ray-plus approximation. The waveforms reflect the accelerated mass motions associated with the characteristic evolutionary stages that were also identified in previous works: a quasi-periodic modulation by prompt post-shock convection is followed by a phase of relative quiescence before growing amplitudes signal violent hydrodynamical activity due to convection and the standing accretion shock instability during the accretion period of the stalled shock. Finally, a high-frequency, low-amplitude variation from proto-neutron star (PNS) convection below the neutrinosphere appears superimposed on the low-frequency trend associated with the aspherical expansion of the SN shock after the onset of the explosion. Relativistic effects in combination with detailed neutrino transport are shown to be essential for quantitative predictions of the GW frequency evolution and energy spectrum, because they determine the structure of the PNS surface layer and its characteristic g-mode frequency. Burst-like high-frequency activity phases, correlated with sudden luminosity increase and spectral hardening of electron (anti-)neutrino emission for some 10 ms, are discovered as new features after the onset of the explosion. They correspond to intermittent episodes of anisotropic accretion by the PNS in the case of fallback SNe. We find stronger signals for more massive progenitors with large accretion rates. The typical frequencies are higher for massive PNSs, though the time-integrated spectrum also strongly depends on the model dynamics.
Modeling and evaluation of HE driven shock effects in copper with the MTS model
International Nuclear Information System (INIS)
Murphy, M.J.; Lassila, D.F.
1997-01-01
Many experimental studies have investigated the effect of shock pressure on the post-shock mechanical properties of OFHC copper. These studies have shown that significant hardening occurs during shock loading due to dislocation processes and twinning. It has been demonstrated that when an appropriate initial value of the Mechanical Threshold Stress (MTS) is specified, the post-shock flow stress of OFE copper is well described by relationships derived independently for unshocked materials. In this study we consider the evolution of the MTS during HE driven shock loading processes and the effect on the subsequent flow stress of the copper. An increased post shock flow stress results in a higher material temperature due to an increase in the plastic work. An increase in temperature leads to thermal softening which reduces the flow stress. These coupled effects will determine if there is melting in a shaped charge jet or a necking instability in an EFP Ww. 'Me critical factor is the evolution path followed combined with the 'current' temperature, plastic strain, and strain rate. Preliminary studies indicate that in simulations of HE driven shock with very high resolution zoning, the MTS saturates because of the rate dependence in the evolution law. On going studies are addressing this and other issues with the goal of developing a version of the MT'S model that treats HE driven, shock loading, temperature, strain, and rate effects apriori
Hydrodynamic modeling of hydrologic surface connectivity within a coastal river-floodplain system
Castillo, C. R.; Guneralp, I.
2017-12-01
Hydrologic surface connectivity (HSC) within river-floodplain environments is a useful indicator of the overall health of riparian habitats because it allows connections amongst components/landforms of the riverine landscape system to be quantified. Overbank flows have traditionally been the focus for analyses concerned with river-floodplain connectivity, but recent works have identified the large significance from sub-bankfull streamflows. Through the use of morphometric analysis and a digital elevation model that is relative to the river water surface, we previously determined that >50% of the floodplain for Mission River on the Coastal Bend of Texas becomes connected to the river at streamflows well-below bankfull conditions. Guided by streamflow records, field-based inundation data, and morphometric analysis; we develop a two-dimensional hydrodynamic model for lower portions of Mission River Floodplain system. This model not only allows us to analyze connections induced by surface water inundation, but also other aspects of the hydrologic connectivity concept such as exchanges of sediment and energy between the river and its floodplain. We also aggregate hydrodynamic model outputs to an object/landform level in order to analyze HSC and associated attributes using measures from graph/network theory. Combining physically-based hydrodynamic models with object-based and graph theoretical analyses allow river-floodplain connectivity to be quantified in a consistent manner with measures/indicators commonly used in landscape analysis. Analyzes similar to ours build towards the establishment of a formal framework for analyzing river-floodplain interaction that will ultimately serve to inform the management of riverine/floodplain environments.
Hydrodynamic modelling as a need for protection of the surface flows
International Nuclear Information System (INIS)
Popovska, Tsvetanka
1997-01-01
The problems of flow in the open flows, rivers and lakes especially today require serious access and its global solving. The choice of basic equations and the method of their solving is from the exceptional importance. Regardless of the fact whether two or three dimensional model is selected, as a global mathematical model it should have three phases: (i) hydrodynamic model with which the current picture is determined, (ii) transport-dispersive model with which the distribution of various physical-chemical parameters is determined and (iii) ecological model which uses the results from the first two phases, determines the situation of degradation and concentration of the various parameters and further provides measures for surpassing the negative situations. The flow in the open flows generally is a turbulent phenomena especially in the zones of emptying-releasing on the surface water currents and contaminants. Characteristic for turbulent flows is their stochastic nature, i.e. they lack and kind of regularity of the physic-hydraulic parameters. So, certain measuring are needed and within todays degree of pollution of our surface waters, we should say urgent. This kind of measuring from hydrodynamic aspect are concerned to the boundary and start conditions, or the conditions which rule on the surface, in the bottom and the coast. From the quality aspect, they need systematic measuring of the biological and chemical parameters. This points out to the need of multidisciplinary and not partial access in developing and application of the mathematical model
Investigation of Two-Phase Flow in AxialCentrifugal Impeller by Hydrodynamic Modeling Methods
Directory of Open Access Journals (Sweden)
V. O. Lomakin
2014-01-01
Full Text Available The article provides a methodology to study the flow in the wet part of the pump with fundamentally new axial-centrifugal impeller by methods of hydrodynamic modeling in the software package STAR CCM +. The objective of the study was to determine the normal and cavitation characteristics of the pump with a new type of wet part, as well as optimization of the geometrical parameters of the pump. Authors solved this problem using an example of the hot coolant pump, which should meet high requirements for cavitation quality and efficiency (hydraulic efficiency up to 87%, critical value of NPSH to 2.2 m.Also, the article focuses on the methods of numerical solution of two-phase flow simulation in a pump that are needed for a more accurate simulation of cavitation in the pump and research work in liquids with high gas content.Hydrodynamic modeling was performed on a computing cluster at the department E-10 of BMSTU for pump flow simulation in unsteady statement of problem using the computational grid size to 1.5 million cells. Simultaneously, the experimental model of the pump was made by 3D printing and tested at the stand in the BMSTU. Test results, which were compared with the calculated data are also given in the article. Inaccuracy of the calculation of pump head does not exceed 5%.The simulation results may be of interest to specialists in the field of hydrodynamic modeling, and for designers of such pumps. The authors also report production of a full-length prototype of the pump in order to conduct further testing for the verification of the data in the article, primarily in terms of cavitation characteristics.
MODEL OF HYDRODYNAMIC MIXING OF CARBONIC POWDERS IN VACUUMATOR, USED IN STEEL-MAKING OF RUP “BMZ”
Directory of Open Access Journals (Sweden)
A. N. Chichko
2005-01-01
Full Text Available The mathematical model of the mixing and dissolving process of carbonic powder in a system '"vacuumator-bowl” under influence of circulating argon is offered. The spatial distribution of hydrodynamic currents at mixing of carbonic powder, received on the basis of computer calculations is presented. The character of distribution of hydrodynamic speeds of melt (circulating currents in industrial bowl and vacuumator for different time slots of mixing is determined.
Formation and decay of laser-generated shock waves
Energy Technology Data Exchange (ETDEWEB)
Cottet, F.; Romain, J.P.
1982-01-01
The process of formation and decay of laser-generated shock waves is described by a hydrodynamic model. Measurements of shock velocities are performed on copper foils for incident intensities between 3 x 10/sup 11/ and 3 x 10/sup 12/ W/cm/sup 2/, with the use of piezoelectric detectors. Maximum induced pressures are found between 0.5 and 1.2 Mbar in the intensity range considered. Analysis of the results with the shock-evolution model outlines the importance of the decay process of laser-generated shocks.
International Nuclear Information System (INIS)
Battaglia, N.; Trac, H.; Cen, R.; Loeb, A.
2013-01-01
We present a new method for modeling inhomogeneous cosmic reionization on large scales. Utilizing high-resolution radiation-hydrodynamic simulations with 2048 3 dark matter particles, 2048 3 gas cells, and 17 billion adaptive rays in a L = 100 Mpc h –1 box, we show that the density and reionization redshift fields are highly correlated on large scales (∼> 1 Mpc h –1 ). This correlation can be statistically represented by a scale-dependent linear bias. We construct a parametric function for the bias, which is then used to filter any large-scale density field to derive the corresponding spatially varying reionization redshift field. The parametric model has three free parameters that can be reduced to one free parameter when we fit the two bias parameters to simulation results. We can differentiate degenerate combinations of the bias parameters by combining results for the global ionization histories and correlation length between ionized regions. Unlike previous semi-analytic models, the evolution of the reionization redshift field in our model is directly compared cell by cell against simulations and performs well in all tests. Our model maps the high-resolution, intermediate-volume radiation-hydrodynamic simulations onto lower-resolution, larger-volume N-body simulations (∼> 2 Gpc h –1 ) in order to make mock observations and theoretical predictions
Hydrodynamic modeling along the southern tip of India: A special emphasis on Kanyakumari coast
Directory of Open Access Journals (Sweden)
K. Gurumoorthi
2017-12-01
Full Text Available Hydrodynamic models are important to many coastal engineering designs and application, especially addressing sediment and water quality. In this study, MIKE 21 two-dimensional (2D hydrodynamic model based on the flexible mesh (FM technique was used to simulate the surface currents forced by tides and winds in Kanyakumari coast. The model results of the tidal level along shore and cross shore currents are agreed well with measured data in Kanyakumari coast. The major components of tides and currents are analyzed by harmonic analysis methods. Root mean square error (RMSE values for the measured and model tides (0.017 m and 0.079 m and currents (0.025 m/s and 0.009 m/s during the northeast (NE and southwest (SW monsoon period are calculated. A series of scenario runs for NE and SW monsoon season are used to understand the regional circulation. The model result shows that the Kanyakumari coast is dominated by tides and surface currents flow, which are influenced by the seasonal reversal wind pattern. Flows around this coastal water have been evidenced small scale cyclonic and anti-cyclonic eddies ranged from ∼55 to 120 km in diameter. The cyclonic and anti-cyclonic eddies are mostly appeared in near Kanyakumari and SE coast of Kerala due to local/ remotely generated forces.
A simplified hydrodynamic model of hydrogen flame propagation in reactor vessels
International Nuclear Information System (INIS)
Baer, M.; Ratzel, A.
1983-01-01
A hydrodynamic model for hydrogen flame propagation in reactor geometries is presented. This model is consistent with the theory of slow combustion in which the gasdynamic field equations are treated in the limit of small Mach numbers. To the lowest order, pressure is spatially uniform. The flame is treated as a density and entropy discontinuity which propagates at prescribed burning velocities, corresponding to laminar or turbulent flames. Radiation cooling of the burned combustion gases and possible preheating of the unburned gases during propagation of the flame is included using a molecular gas-band thermal radiation model. Application of this model has been developed for 1-D variable area flame propagation. Multidimensional effects induced by hydrodynamics and buoyancy are introduced as a correction to the burn velocity (which reflects a modification of planar flame surface to a distorted surface) using experimentally measured pressure-rise time data for hydrogen/air deflagrations in cylindrical vessels. This semianalytical model of flame propagation reduces to a set of ordinary differential equations which describes the temporal variations of vessel pressure, burned volume and gas entropy. The thermodynamic state of the burned gas immediately following the flame is determined using an isobaric Hugoniot relationship. At other locations the burned gas thermodynamic states are determined using a Lagrangian particle tracking method. Results of a computer code using the method are presented
Conaway, Jeffrey S.; Moran, Edward H.
2004-01-01
Bathymetric and hydraulic data were collected by the U.S. Geological Survey on the Tanana River in proximity to Alaska Department of Transportation and Public Facilities' bridge number 505 at mile 80.5 of the Alaska Highway. Data were collected from August 7-9, 2002, over an approximate 5,000- foot reach of the river. These data were combined with topographic data provided by Alaska Department of Transportation and Public Facilities to generate a two-dimensional hydrodynamic model. The hydrodynamic model was calibrated with water-surface elevations, flow velocities, and flow directions collected at a discharge of 25,600 cubic feet per second. The calibrated model was then used for a simulation of the 100-year recurrence interval discharge of 51,900 cubic feet per second. The existing bridge piers were removed from the model geometry in a second simulation to model the hydraulic conditions in the channel without the piers' influence. The water-surface elevations, flow velocities, and flow directions from these simulations can be used to evaluate the influence of the piers on flow hydraulics and will assist the Alaska Department of Transportation and Public Facilities in the design of a replacement bridge.
Climate Shocks and Migration: An Agent-Based Modeling Approach
Entwisle, Barbara; Williams, Nathalie E.; Verdery, Ashton M.; Rindfuss, Ronald R.; Walsh, Stephen J.; Malanson, George P.; Mucha, Peter J.; Frizzelle, Brian G.; McDaniel, Philip M.; Yao, Xiaozheng; Heumann, Benjamin W.; Prasartkul, Pramote; Sawangdee, Yothin; Jampaklay, Aree
2016-01-01
This is a study of migration responses to climate shocks. We construct an agent-based model that incorporates dynamic linkages between demographic behaviors, such as migration, marriage, and births, and agriculture and land use, which depend on rainfall patterns. The rules and parameterization of our model are empirically derived from qualitative and quantitative analyses of a well-studied demographic field site, Nang Rong district, Northeast Thailand. With this model, we simulate patterns of migration under four weather regimes in a rice economy: 1) a reference, ‘normal’ scenario; 2) seven years of unusually wet weather; 3) seven years of unusually dry weather; and 4) seven years of extremely variable weather. Results show relatively small impacts on migration. Experiments with the model show that existing high migration rates and strong selection factors, which are unaffected by climate change, are likely responsible for the weak migration response. PMID:27594725
Modeling secondary accidents identified by traffic shock waves.
Junhua, Wang; Boya, Liu; Lanfang, Zhang; Ragland, David R
2016-02-01
The high potential for occurrence and the negative consequences of secondary accidents make them an issue of great concern affecting freeway safety. Using accident records from a three-year period together with California interstate freeway loop data, a dynamic method for more accurate classification based on the traffic shock wave detecting method was used to identify secondary accidents. Spatio-temporal gaps between the primary and secondary accident were proven be fit via a mixture of Weibull and normal distribution. A logistic regression model was developed to investigate major factors contributing to secondary accident occurrence. Traffic shock wave speed and volume at the occurrence of a primary accident were explicitly considered in the model, as a secondary accident is defined as an accident that occurs within the spatio-temporal impact scope of the primary accident. Results show that the shock waves originating in the wake of a primary accident have a more significant impact on the likelihood of a secondary accident occurrence than the effects of traffic volume. Primary accidents with long durations can significantly increase the possibility of secondary accidents. Unsafe speed and weather are other factors contributing to secondary crash occurrence. It is strongly suggested that when police or rescue personnel arrive at the scene of an accident, they should not suddenly block, decrease, or unblock the traffic flow, but instead endeavor to control traffic in a smooth and controlled manner. Also it is important to reduce accident processing time to reduce the risk of secondary accident. Copyright © 2015 Elsevier Ltd. All rights reserved.
A SIMPLE EXPERIMENTAL MODEL OF HEAT SHOCK RESPONSE IN RATS
Directory of Open Access Journals (Sweden)
Tufi Neder Meyer
1998-10-01
Full Text Available Objective: To obtain a simple model for the elicitation of the heat shock response in rats. Design: Laboratory study. Setting: University research laboratories. Sample: Seventy-nine adult male albino rats (weight range 200 g to 570 g. Procedures: Exposure to heat stress by heating animals in a warm bath for 5 min after their rectal temperatures reached 107.60 F (420 C. Liver and lung samples were collected for heat-shock protein 70 (HSP70 detection (Western analysis. Results: Western analysis was positive for HSP70 in the liver and in the lungs of heated animals. There was a temporal correlation between heating and HSP70 detection: it was strongest 1 day after heating and reduced afterwards. No heated animals died. Conclusion: These data show that heating rats in a warm (45o C bath, according to parameters set in this model, elicits efficiently the heat shock response.OBJETIVO: Obter um modelo simples para tentar esclarecer a resposta ao choque térmico em ratos. LOCAL: Laboratório de pesquisa da Universidade. MÉTODO: Amostra: 79 ratos albinos, adultos, entre 200g a 570g. Procedimentos: Exposição ao calor, em banho quente, por 5 minutos, após a temperatura retal chegar a 42 graus centigrados. Biópsias de fígado e pulmão foram obtidas para detectar a proteina 70 (HSP 70, pelo "Western blot". RESULTADOS: As análises foram positivas nos animais aquecidos, com uma correlação entre aquecimento e constatação da HSP 70. Foi mais elevada no primeiro dia e não houve óbitos nos animais aquecidos. CONCLUSÃO: Os ratos aquecidos a 45 graus centígrados respondem eficientemente ao choque térmico.
Directory of Open Access Journals (Sweden)
Azad Wan Hazdy
2017-01-01
Full Text Available Flood disaster occurs quite frequently in Malaysia and has been categorized as the most threatening natural disaster compared to landslides, hurricanes, tsunami, haze and others. A study by Department of Irrigation and Drainage (DID show that 9% of land areas in Malaysia are prone to flood which may affect approximately 4.9 million of the population. 2 Dimensional floods routing modelling demonstrate is turning out to be broadly utilized for flood plain display and is an extremely viable device for evaluating flood. Flood propagations can be better understood by simulating the flow and water level by using hydrodynamic modelling. The hydrodynamic flood routing can be recognized by the spatial complexity of the schematization such as 1D model and 2D model. It was found that most of available hydrological models for flood forecasting are more focus on short duration as compared to long duration hydrological model using the Probabilistic Distribution Moisture Model (PDM. The aim of this paper is to discuss preliminary findings on development of flood forecasting model using Probabilistic Distribution Moisture Model (PDM for Kelantan river basin. Among the findings discuss in this paper includes preliminary calibrated PDM model, which performed reasonably for the Dec 2014, but underestimated the peak flows. Apart from that, this paper also discusses findings on Soil Moisture Deficit (SMD and flood plain analysis. Flood forecasting is the complex process that begins with an understanding of the geographical makeup of the catchment and knowledge of the preferential regions of heavy rainfall and flood behaviour for the area of responsibility. Therefore, to decreases the uncertainty in the model output, so it is important to increase the complexity of the model.
Note on the hydrodynamic description of thin nematic films: Strong anchoring model
Lin, Te-Sheng; Cummings, Linda J.; Archer, Andrew J.; Kondic, Lou; Thiele, Uwe
2013-01-01
We discuss the long-wave hydrodynamic model for a thin film of nematic liquid crystal in the limit of strong anchoring at the free surface and at the substrate. We rigorously clarify how the elastic energy enters the evolution equation for the film thickness in order to provide a solid basis for further investigation: several conflicting models exist in the literature that predict qualitatively different behaviour. We consolidate the various approaches and show that the long-wave model derived through an asymptotic expansion of the full nemato-hydrodynamic equations with consistent boundary conditions agrees with the model one obtains by employing a thermodynamically motivated gradient dynamics formulation based on an underlying free energy functional. As a result, we find that in the case of strong anchoring the elastic distortion energy is always stabilising. To support the discussion in the main part of the paper, an appendix gives the full derivation of the evolution equation for the film thickness via asymptotic expansion. © 2013 AIP Publishing LLC.
Hydrodynamic and Inundation Modeling of China’s Largest Freshwater Lake Aided by Remote Sensing Data
Directory of Open Access Journals (Sweden)
Peng Zhang
2015-04-01
Full Text Available China’s largest freshwater lake, Poyang Lake, is characterized by rapid changes in its inundation area and hydrodynamics, so in this study, a hydrodynamic model of Poyang Lake was established to simulate these long-term changes. Inundation information was extracted from Moderate Resolution Imaging Spectroradiometer (MODIS remote sensing data and used to calibrate the wetting and drying parameter by assessing the accuracy of the simulated inundation area and its boundary. The bottom friction parameter was calibrated using current velocity measurements from Acoustic Doppler Current Profilers (ADCP. The results show the model is capable of predicting the inundation area dynamic through cross-validation with remotely sensed inundation data, and can reproduce the seasonal dynamics of the water level, and water discharge through a comparison with hydrological data. Based on the model results, the characteristics of the current velocities of the lake in the wet season and the dry season of the lake were explored, and the potential effect of the current dynamic on water quality patterns was discussed. The model is a promising basic tool for prediction and management of the water resource and water quality of Poyang Lake.
A quantum hydrodynamic model for multicomponent quantum magnetoplasma with Jeans term
International Nuclear Information System (INIS)
Masood, W.; Salimullah, M.; Shah, H.A.
2008-01-01
The effect of Jeans term in a multicomponent self-gravitating quantum magnetoplasma is investigated employing the quantum hydrodynamic (QHD) model. The effects of quantum Bohm potential and statistical terms as well as the ambient magnetic field are also investigated on both dust and ion dynamics driven waves in this Letter. We state the conditions that can drive the system unstable in the presence of Jeans term. The limiting cases are also presented. The present work may have relevance in the dense astrophysical environments where the self-gravitating effects are expected to play a pivotal role
Transverse-momentum distribution of particles according to the hydrodynamical model
International Nuclear Information System (INIS)
Yogiro, H.
1977-12-01
A fit to the transverse-momentum distribution is performed, in the context of the hydrodynamical model. By fixing a (total-energy-independent) dissociation temperature T and a transverse fluid-rapidity distribution whose width increases logarithmically with s, the existing data can be reproduced in all the P1 interval (where ω dsigma divided by d vector P varies by a factor of 10 -10 ) including their energy dependence. The final inclusive cross section appears to be approximately factorized in the longitudinal and the transverse rapidities, as verified experimentally
Smoothed particle hydrodynamics modelling in continuum mechanics: fluid-structure interaction
Directory of Open Access Journals (Sweden)
Groenenboom P. H. L.
2009-06-01
Full Text Available Within this study, the implementation of the smoothed particle hydrodynamics (SPH method solving the complex problem of interaction between a quasi-incompressible fluid involving a free surface and an elastic structure is outlined. A brief description of the SPH model for both the quasi-incompressible fluid and the isotropic elastic solid is presented. The interaction between the fluid and the elastic structure is realised through the contact algorithm. The results of numerical computations are confronted with the experimental as well as computational data published in the literature.
Larmat, C. S.; Rougier, E.; Delorey, A.; Steedman, D. W.; Bradley, C. R.
2016-12-01
The goal of the Source Physics Experiment (SPE) is to bring empirical and theoretical advances to the problem of detection and identification of underground nuclear explosions. For this, the SPE program includes a strong modeling effort based on first principles calculations with the challenge to capture both the source and near-source processes and those taking place later in time as seismic waves propagate within complex 3D geologic environments. In this paper, we report on results of modeling that uses hydrodynamic simulation codes (Abaqus and CASH) coupled with a 3D full waveform propagation code, SPECFEM3D. For modeling the near source region, we employ a fully-coupled Euler-Lagrange (CEL) modeling capability with a new continuum-based visco-plastic fracture model for simulation of damage processes, called AZ_Frac. These capabilities produce high-fidelity models of various factors believed to be key in the generation of seismic waves: the explosion dynamics, a weak grout-filled borehole, the surrounding jointed rock, and damage creation and deformations happening around the source and the free surface. SPECFEM3D, based on the Spectral Element Method (SEM) is a direct numerical method for full wave modeling with mathematical accuracy. The coupling interface consists of a series of grid points of the SEM mesh situated inside of the hydrodynamic code's domain. Displacement time series at these points are computed using output data from CASH or Abaqus (by interpolation if needed) and fed into the time marching scheme of SPECFEM3D. We will present validation tests with the Sharpe's model and comparisons of waveforms modeled with Rg waves (2-8Hz) that were recorded up to 2 km for SPE. We especially show effects of the local topography, velocity structure and spallation. Our models predict smaller amplitudes of Rg waves for the first five SPE shots compared to pure elastic models such as Denny &Johnson (1991).
Combining Envisat type and CryoSat-2 altimetry to inform hydrodynamic models
Schneider, Raphael; Nygaard Godiksen, Peter; Villadsen, Heidi; Madsen, Henrik; Bauer-Gottwein, Peter
2015-04-01
Hydrological models are developed and used for flood forecasting and water resources management. Such models rely on a variety of input and calibration data. In general, and especially in data scarce areas, remote sensing provides valuable data for the parameterization and updating of such models. Satellite radar altimeters provide water level measurements of inland water bodies. So far, many studies making use of satellite altimeters have been based on data from repeat-orbit missions such as Envisat, ERS or Jason or on synthetic wide-swath altimetry data as expected from the SWOT mission. This work represents one of the first hydrologic applications of altimetry data from a drifting orbit satellite mission, using data from CryoSat-2. We present an application where CryoSat-2 data is used to improve a hydrodynamic model of the Ganges and Brahmaputra river basins in South Asia set up in the DHI MIKE 11 software. The model's parameterization and forcing is mainly based on remote sensing data, for example the TRMM 3B42 precipitation product and the SRTM DEM for river and subcatchment delineation. CryoSat-2 water levels were extracted over a river mask derived from Landsat 7 and 8 imagery. After calibrating the hydrological-hydrodynamic model against observed discharge, simulated water levels were fitted to the CryoSat-2 data, with a focus on the Brahmaputra river in the Assam valley: The average simulated water level in the hydrodynamic model was fitted to the average water level along the river's course as observed by CryoSat-2 over the years 2011-2013 by adjusting the river bed elevation. In a second step, the cross section shapes were adjusted so that the simulated water level dynamics matched those obtained from Envisat virtual station time series. The discharge calibration resulted in Nash-Sutcliffe coefficients of 0.86 and 0.94 for the Ganges and Brahmaputra. Using the Landsat river mask, the CryoSat-2 water levels show consistency along the river and are in
Energy Technology Data Exchange (ETDEWEB)
Wang, Taiping; Yang, Zhaoqing; Khangaonkar, Tarang
2010-04-22
In this study, a hydrodynamic model based on the unstructured-grid finite volume coastal ocean model (FVCOM) was developed for Bellingham Bay, Washington. The model simulates water surface elevation, velocity, temperature, and salinity in a three-dimensional domain that covers the entire Bellingham Bay and adjacent water bodies, including Lummi Bay, Samish Bay, Padilla Bay, and Rosario Strait. The model was developed using Pacific Northwest National Laboratory’s high-resolution Puget Sound and Northwest Straits circulation and transport model. A sub-model grid for Bellingham Bay and adjacent coastal waters was extracted from the Puget Sound model and refined in Bellingham Bay using bathymetric light detection and ranging (LIDAR) and river channel cross-section data. The model uses tides, river inflows, and meteorological inputs to predict water surface elevations, currents, salinity, and temperature. A tidal open boundary condition was specified using standard National Oceanic and Atmospheric Administration (NOAA) predictions. Temperature and salinity open boundary conditions were specified based on observed data. Meteorological forcing (wind, solar radiation, and net surface heat flux) was obtained from NOAA real observations and National Center for Environmental Prediction North American Regional Analysis outputs. The model was run in parallel with 48 cores using a time step of 2.5 seconds. It took 18 hours of cpu time to complete 26 days of simulation. The model was calibrated with oceanographic field data for the period of 6/1/2009 to 6/26/2009. These data were collected specifically for the purpose of model development and calibration. They include time series of water-surface elevation, currents, temperature, and salinity as well as temperature and salinity profiles during instrument deployment and retrieval. Comparisons between model predictions and field observations show an overall reasonable agreement in both temporal and spatial scales. Comparisons of
Combining Envisat type and CryoSat-2 altimetry to inform hydrodynamic models
DEFF Research Database (Denmark)
Schneider, Raphael; Nygaard Godiksen, Peter; Villadsen, Heidi
2015-01-01
by CryoSat-2 over the years 2011-2013 by adjusting the river bed elevation. In a second step, the cross section shapes were adjusted so that the simulated water level dynamics matched those obtained from Envisat virtual station time series. The discharge calibration resulted in Nash-Sutcliffe coefficients...... channel with a higher accuracy than a model based on the SRTM DEM. Furthermore, the amplitudes as observed in Envisat virtual station time series could be reproduced fitting simple triangular cross section shapes. A hydrodynamic model prepared in such a way provides water levels at any point along......Hydrological models are developed and used for flood forecasting and water resources management. Such models rely on a variety of input and calibration data. In general, and especially in data scarce areas, remote sensing provides valuable data for the parameterization and updating of such models...
Formation of intermediate shocks in both two-fluid and hybrid models
International Nuclear Information System (INIS)
Wu, C.C.; Hada, T.
1991-01-01
Intermediate shocks are shocks with shock frame fluid velocities greater than the Alfven speed ahead and less than the Alfven speed behind, or equivalently, across intermediate shocks the sign of the transverse component of the magnetic field changes. These shocks had been considered extraneous, or nonevolutionary, or unstable, and they had been thought not to correspond to physical reality [Germain, 1960; Jeffrey and Taniuti, 1964; Kantrowitz and Petschek, 1966]. However, it has been shown that intermediate shocks can be formed from continuous waves according to dissipative magnetohydrodynamics (MHD) [Wu, 1987, 1988a, b, 1990]. Thus according to the formation argument which requires that physical shocks be formed by the wave steepening process, the intermediate shocks should be considered physical. Here, intermediate shocks are studied in a two-fluid model that includes finite ion inertia dispersion and in a hybrid model in which the full ion dynamics is retained while the electrons are treated as a massless fluid. The authors show that in both models intermediate shocks can be formed through wave steepening, meaning that they are stable and possess shock structures
Comparison of new generation low-complexity flood inundation mapping tools with a hydrodynamic model
Afshari, Shahab; Tavakoly, Ahmad A.; Rajib, Mohammad Adnan; Zheng, Xing; Follum, Michael L.; Omranian, Ehsan; Fekete, Balázs M.
2018-01-01
The objective of this study is to compare two new generation low-complexity tools, AutoRoute and Height Above the Nearest Drainage (HAND), with a two-dimensional hydrodynamic model (Hydrologic Engineering Center-River Analysis System, HEC-RAS 2D). The assessment was conducted on two hydrologically different and geographically distant test-cases in the United States, including the 16,900 km2 Cedar River (CR) watershed in Iowa and a 62 km2 domain along the Black Warrior River (BWR) in Alabama. For BWR, twelve different configurations were set up for each of the models, including four different terrain setups (e.g. with and without channel bathymetry and a levee), and three flooding conditions representing moderate to extreme hazards at 10-, 100-, and 500-year return periods. For the CR watershed, models were compared with a simplistic terrain setup (without bathymetry and any form of hydraulic controls) and one flooding condition (100-year return period). Input streamflow forcing data representing these hypothetical events were constructed by applying a new fusion approach on National Water Model outputs. Simulated inundation extent and depth from AutoRoute, HAND, and HEC-RAS 2D were compared with one another and with the corresponding FEMA reference estimates. Irrespective of the configurations, the low-complexity models were able to produce inundation extents similar to HEC-RAS 2D, with AutoRoute showing slightly higher accuracy than the HAND model. Among four terrain setups, the one including both levee and channel bathymetry showed lowest fitness score on the spatial agreement of inundation extent, due to the weak physical representation of low-complexity models compared to a hydrodynamic model. For inundation depth, the low-complexity models showed an overestimating tendency, especially in the deeper segments of the channel. Based on such reasonably good prediction skills, low-complexity flood models can be considered as a suitable alternative for fast
The optimization of high resolution topographic data for 1D hydrodynamic models
International Nuclear Information System (INIS)
Ales, Ronovsky; Michal, Podhoranyi
2016-01-01
The main focus of our research presented in this paper is to optimize and use high resolution topographical data (HRTD) for hydrological modelling. Optimization of HRTD is done by generating adaptive mesh by measuring distance of coarse mesh and the surface of the dataset and adapting the mesh from the perspective of keeping the geometry as close to initial resolution as possible. Technique described in this paper enables computation of very accurate 1-D hydrodynamic models. In the paper, we use HEC-RAS software as a solver. For comparison, we have chosen the amount of generated cells/grid elements (in whole discretization domain and selected cross sections) with respect to preservation of the accuracy of the computational domain. Generation of the mesh for hydrodynamic modelling is strongly reliant on domain size and domain resolution. Topographical dataset used in this paper was created using LiDAR method and it captures 5.9km long section of a catchment of the river Olše. We studied crucial changes in topography for generated mesh. Assessment was done by commonly used statistical and visualization methods.
The optimization of high resolution topographic data for 1D hydrodynamic models
Ales, Ronovsky; Michal, Podhoranyi
2016-06-01
The main focus of our research presented in this paper is to optimize and use high resolution topographical data (HRTD) for hydrological modelling. Optimization of HRTD is done by generating adaptive mesh by measuring distance of coarse mesh and the surface of the dataset and adapting the mesh from the perspective of keeping the geometry as close to initial resolution as possible. Technique described in this paper enables computation of very accurate 1-D hydrodynamic models. In the paper, we use HEC-RAS software as a solver. For comparison, we have chosen the amount of generated cells/grid elements (in whole discretization domain and selected cross sections) with respect to preservation of the accuracy of the computational domain. Generation of the mesh for hydrodynamic modelling is strongly reliant on domain size and domain resolution. Topographical dataset used in this paper was created using LiDAR method and it captures 5.9km long section of a catchment of the river Olše. We studied crucial changes in topography for generated mesh. Assessment was done by commonly used statistical and visualization methods.
The optimization of high resolution topographic data for 1D hydrodynamic models
Energy Technology Data Exchange (ETDEWEB)
Ales, Ronovsky, E-mail: ales.ronovsky@vsb.cz; Michal, Podhoranyi [IT4Innovations National Supercomputing Center, VŠB-Technical University of Ostrava, Studentská 6231/1B, 708 33 Ostrava (Czech Republic)
2016-06-08
The main focus of our research presented in this paper is to optimize and use high resolution topographical data (HRTD) for hydrological modelling. Optimization of HRTD is done by generating adaptive mesh by measuring distance of coarse mesh and the surface of the dataset and adapting the mesh from the perspective of keeping the geometry as close to initial resolution as possible. Technique described in this paper enables computation of very accurate 1-D hydrodynamic models. In the paper, we use HEC-RAS software as a solver. For comparison, we have chosen the amount of generated cells/grid elements (in whole discretization domain and selected cross sections) with respect to preservation of the accuracy of the computational domain. Generation of the mesh for hydrodynamic modelling is strongly reliant on domain size and domain resolution. Topographical dataset used in this paper was created using LiDAR method and it captures 5.9km long section of a catchment of the river Olše. We studied crucial changes in topography for generated mesh. Assessment was done by commonly used statistical and visualization methods.
Wang, Y.; Ramaswamy, V.; Saleh, F.
2017-12-01
Barnegat Bay located on the east coast of New Jersey, United States and is separated from the Atlantic Ocean by the narrow Barnegat Peninsula which acts as a barrier island. The bay is fed by several rivers which empty through small estuaries along the inner shore. In terms of vulnerability from flooding, the Barnegat Peninsula is under the influence of both coastal storm surge and riverine flooding. Barnegat Bay was hit by Hurricane Sandy causing flood damages with extensive cross-island flow at many streets perpendicular to the shoreline. The objective of this work is to identify and quantify the sources of flooding using a two dimensional inland hydrodynamic model. The hydrodynamic model was forced by three observed coastal boundary conditions, and one hydrologic boundary condition from United States Geological Survey (USGS). The model reliability was evaluated with both FEMA spatial flooding extend and USGS High water marks. Simulated flooding extent showed good agreement with the reanalysis spatial inundation extents. Results offered important perspectives on the flow of the water into the bay, the velocity and the depth of the inundated areas. Using such information can enable emergency managers and decision makers identify evacuation and deploy flood defenses.
A 3D unstructured grid nearshore hydrodynamic model based on the vortex force formalism
Zheng, Peng; Li, Ming; van der A, Dominic A.; van der Zanden, Joep; Wolf, Judith; Chen, Xueen; Wang, Caixia
2017-08-01
A new three-dimensional nearshore hydrodynamic model system is developed based on the unstructured-grid version of the third generation spectral wave model SWAN (Un-SWAN) coupled with the three-dimensional ocean circulation model FVCOM to enable the full representation of the wave-current interaction in the nearshore region. A new wave-current coupling scheme is developed by adopting the vortex-force (VF) scheme to represent the wave-current interaction. The GLS turbulence model is also modified to better reproduce wave-breaking enhanced turbulence, together with a roller transport model to account for the effect of surface wave roller. This new model system is validated first against a theoretical case of obliquely incident waves on a planar beach, and then applied to three test cases: a laboratory scale experiment of normal waves on a beach with a fixed breaker bar, a field experiment of oblique incident waves on a natural, sandy barred beach (Duck'94 experiment), and a laboratory study of normal-incident waves propagating around a shore-parallel breakwater. Overall, the model predictions agree well with the available measurements in these tests, illustrating the robustness and efficiency of the present model for very different spatial scales and hydrodynamic conditions. Sensitivity tests indicate the importance of roller effects and wave energy dissipation on the mean flow (undertow) profile over the depth. These tests further suggest to adopt a spatially varying value for roller effects across the beach. In addition, the parameter values in the GLS turbulence model should be spatially inhomogeneous, which leads to better prediction of the turbulent kinetic energy and an improved prediction of the undertow velocity profile.
Kranz, M
1954-01-01
Drop hammer tests with different shock strut models and shock strut oils were performed at temperatures ranging to -40 C. The various shock strut models do not differ essentially regarding their springing and damping properties at low temperatures; however, the influence of the different shock strut oils on the springing properties at low temperatures varies greatly.
Surface and bulk plasmon excitations in carbon nanotubes. Comparison with the hydrodynamic model
Energy Technology Data Exchange (ETDEWEB)
Zapata Herrera, Mario [Instituto Balseiro and Centro Atomico Bariloche, Comision Nacional de Energia Atomica, 8400 S.C. Bariloche (Argentina)], E-mail: mzapatah@gmail.com; Gervasoni, Juana L. [Instituto Balseiro and Centro Atomico Bariloche, Comision Nacional de Energia Atomica, 8400 S.C. Bariloche (Argentina); Carrera de Investigador Cientificoy Tecnologico del CONICET (Argentina)], E-mail: gervason@cab.cnea.gov.ar
2009-01-15
In this work, we compare two models describing the interaction of external charged particles with carbon nanotubes. One is the semiclassical dielectric response model (DRM) in the Drude approximation, which approximate the valence electrons of the system by a gas of non interacting classical particles. The other is the hydrodynamic model (HDM) which uses Fluid Dynamics to describe their collective excitations. We found that both models agree for those cases where it is possible to define a dispersion relation which depends on a single frequency {omega}{sub p}. We found that in the description of the electronic response of a single-walled carbon nanotube (SWCNT) with the DRM, the connection between a three- and a two-dimensional system is non trivial and the equivalence is not direct. In spite of this, the DRM can be an important basic tool for the calculation and physical interpretation of the plasmon excitations in a nanodimensions system.
Hydrodynamic model for ultra-short pulse ablation of hard dental tissue
Energy Technology Data Exchange (ETDEWEB)
London, R.A.; Bailey, D.S.; Young, D.A.; Alley, W.E.; Feit, M.D.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Neev, J. [Beckman Laser Inst., Irvine, CA (United States)
1996-02-29
A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.
Chen, W.-B.; Liu, W.-C.; Hsu, M.-H.
2012-12-01
Precise predictions of storm surges during typhoon events have the necessity for disaster prevention in coastal seas. This paper explores an artificial neural network (ANN) model, including the back propagation neural network (BPNN) and adaptive neuro-fuzzy inference system (ANFIS) algorithms used to correct poor calculations with a two-dimensional hydrodynamic model in predicting storm surge height during typhoon events. The two-dimensional model has a fine horizontal resolution and considers the interaction between storm surges and astronomical tides, which can be applied for describing the complicated physical properties of storm surges along the east coast of Taiwan. The model is driven by the tidal elevation at the open boundaries using a global ocean tidal model and is forced by the meteorological conditions using a cyclone model. The simulated results of the hydrodynamic model indicate that this model fails to predict storm surge height during the model calibration and verification phases as typhoons approached the east coast of Taiwan. The BPNN model can reproduce the astronomical tide level but fails to modify the prediction of the storm surge tide level. The ANFIS model satisfactorily predicts both the astronomical tide level and the storm surge height during the training and verification phases and exhibits the lowest values of mean absolute error and root-mean-square error compared to the simulated results at the different stations using the hydrodynamic model and the BPNN model. Comparison results showed that the ANFIS techniques could be successfully applied in predicting water levels along the east coastal of Taiwan during typhoon events.
International Nuclear Information System (INIS)
Parisot, M.
2011-01-01
This work is dedicated study of a problem resulting from plasma physics: the thermal transfer of electrons in a plasma close to equilibrium Maxwellian. Firstly, a dimensional study of the Vlasov-Fokker-Planck-Maxwell system is performed, allowing one hand to identify a physically relevant parameter of scale and also to define mathematically the contours of validity domain. The asymptotic regime called Spitzer-Harm is studied for a relatively general class of collision operator. The following part of this work is devoted to the derivation and study of the hydrodynamic limit of the system of Vlasov-Maxwell-Landau outside the strictly asymptotic. A model proposed by Schurtz and Nicolais located in this context and analyzed. The particularity of this model lies in the application of a delocalization operation in the heat flux. The link with non-local models of Luciani and Mora is established as well as mathematics properties as the principle of maximum and entropy dissipation. Then a formal derivation from the Vlasov equations with a simplified collision operator, is proposed. The derivation, inspired by the recent work of D. Levermore, involves decomposition methods according to the spherical harmonics and methods of closing called diffusion methods. A hierarchy of intermediate models between the kinetic equations and the hydrodynamic limit is described. In particular a new hydrodynamic system integro-differential by nature, is proposed. The Schurtz and Nicolai model appears as a simplification of the system resulting from the derivation, assuming a steady flow of heat. The above results are then generalized to account for the internal energy dependence which appears naturally in the equation establishment. The existence and uniqueness of the solution of the nonstationary system are established in a simplified framework. The last part is devoted was the implementation of a specific numerical scheme to solve these models. We propose a finite volume approach can be
Modeling NIF experimental designs with adaptive mesh refinement and Lagrangian hydrodynamics
Koniges, A. E.; Anderson, R. W.; Wang, P.; Gunney, B. T. N.; Becker, R.; Eder, D. C.; MacGowan, B. J.; Schneider, M. B.
2006-06-01
Incorporation of adaptive mesh refinement (AMR) into Lagrangian hydrodynamics algorithms allows for the creation of a highly powerful simulation tool effective for complex target designs with three-dimensional structure. We are developing an advanced modeling tool that includes AMR and traditional arbitrary Lagrangian-Eulerian (ALE) techniques. Our goal is the accurate prediction of vaporization, disintegration and fragmentation in National Ignition Facility (NIF) experimental target elements. Although our focus is on minimizing the generation of shrapnel in target designs and protecting the optics, the general techniques are applicable to modern advanced targets that include three-dimensional effects such as those associated with capsule fill tubes. Several essential computations in ordinary radiation hydrodynamics need to be redesigned in order to allow for AMR to work well with ALE, including algorithms associated with radiation transport. Additionally, for our goal of predicting fragmentation, we include elastic/plastic flow into our computations. We discuss the integration of these effects into a new ALE-AMR simulation code. Applications of this newly developed modeling tool as well as traditional ALE simulations in two and three dimensions are applied to NIF early-light target designs.
Modeling NIF Experimental Designs with Adaptive Mesh Refinement and Lagrangian Hydrodynamics
International Nuclear Information System (INIS)
Koniges, A E; Anderson, R W; Wang, P; Gunney, B N; Becker, R; Eder, D C; MacGowan, B J
2005-01-01
Incorporation of adaptive mesh refinement (AMR) into Lagrangian hydrodynamics algorithms allows for the creation of a highly powerful simulation tool effective for complex target designs with three-dimensional structure. We are developing an advanced modeling tool that includes AMR and traditional arbitrary Lagrangian-Eulerian (ALE) techniques. Our goal is the accurate prediction of vaporization, disintegration and fragmentation in National Ignition Facility (NIF) experimental target elements. Although our focus is on minimizing the generation of shrapnel in target designs and protecting the optics, the general techniques are applicable to modern advanced targets that include three-dimensional effects such as those associated with capsule fill tubes. Several essential computations in ordinary radiation hydrodynamics need to be redesigned in order to allow for AMR to work well with ALE, including algorithms associated with radiation transport. Additionally, for our goal of predicting fragmentation, we include elastic/plastic flow into our computations. We discuss the integration of these effects into a new ALE-AMR simulation code. Applications of this newly developed modeling tool as well as traditional ALE simulations in two and three dimensions are applied to NIF early-light target designs
Modeling Nif experimental designs with adaptive mesh refinement and Lagrangian hydrodynamics
International Nuclear Information System (INIS)
Koniges, A.E.; Anderson, R.W.; Wang, P.; Gunney, B.T.N.; Becker, R.; Eder, D.C.; MacGowan, B.J.; Schneider, M.B.
2006-01-01
Incorporation of adaptive mesh refinement (AMR) into Lagrangian hydrodynamics algorithms allows for the creation of a highly powerful simulation tool effective for complex target designs with three-dimensional structure. We are developing an advanced modeling tool that includes AMR and traditional arbitrary Lagrangian-Eulerian (ALE) techniques. Our goal is the accurate prediction of vaporization, disintegration and fragmentation in National Ignition Facility (NIF) experimental target elements. Although our focus is on minimizing the generation of shrapnel in target designs and protecting the optics, the general techniques are applicable to modern advanced targets that include three-dimensional effects such as those associated with capsule fill tubes. Several essential computations in ordinary radiation hydrodynamics need to be redesigned in order to allow for AMR to work well with ALE, including algorithms associated with radiation transport. Additionally, for our goal of predicting fragmentation, we include elastic/plastic flow into our computations. We discuss the integration of these effects into a new ALE-AMR simulation code. Applications of this newly developed modeling tool as well as traditional ALE simulations in two and three dimensions are applied to NIF early-light target designs. (authors)
Numerical Modelling of the 1995 Dinar Earthquake Effects on Hydrodynamic Regime of Egirdir Lake
Directory of Open Access Journals (Sweden)
Murat Aksel
2017-11-01
Full Text Available The effect of earthquakes on closed and semi-closed water systems is a research topic that has been studied for many years. The lack of continuous measurement systems in closed and semi-closed water systems is insufficient to examine and investigate what has happened during the earthquake. The morphological structures of the lakes indicate the characteristics of the events that occurred during an earthquake. Due to the developing technology and research request, some monitoring, measurement stations are installed in some lakes, gulfs, estuaries, etc. systems. Today, both higher quality measurement and field data can be obtained, and more complicated processes are being explored with the help of faster computers. Computational fluid dynamics is currently used because of the difficulty in calculating hydrodynamic responses of lakes due to earthquake. Investigations on the effects of the earthquake condition on the desired closed / semi-closed water system studies by using numerical modelling have been continuing increasingly in recent years. Both the quality of the bathymetric data gathered from the field, the continuous acquisition of both dynamic water level measurement systems, and the use of new technologies and systems in the search for base materials contribute to the fact that we have more knowledge of the formation, behavior and effects of the sorts. In this study, 1995 Dinar Earthquake effects on Egirdir Lake hydrodynamic regime was investigated by numerical modelling approach.
Rapaglia, John; Ferrarin, Christian; Zaggia, Luca; Moore, Willard S; Umgiesser, Georg; Garcia-Solsona, Ester; Garcia-Orellana, Jordi; Masqué, Pere
2010-07-01
The four naturally-occurring isotopes of radium were coupled with a previously evaluated hydrodynamic model to determine the apparent age of surface waters and to quantify submarine groundwater discharge (SGD) into the Venice Lagoon, Italy. Mean apparent age of water in the Venice Lagoon was calculated using the ratio of 224Ra to 228Ra determined from 30 monitoring stations and a mean pore water end member. Average apparent age was calculated to be 6.0 d using Ra ratios. This calculated age was very similar to average residence time calculated for the same period using a hydrodynamic model (5.8 d). A mass balance of Ra was accomplished by quantifying each of the sources and sinks of Ra in the lagoon, with the unknown variable being attributed to SGD. Total SGD were calculated to be 4.1 +/- 1.5, 3.8 +/- 0.7, 3.0 +/- 1.3, and 3.5 +/- 1.0 x 10(10) L d(-1) for (223,224,226, 228)Ra, respectively, which are an order of magnitude larger than total mean fluvial discharge into the Venice Lagoon (3.1 x 10(9) L d(-1)). The SGD as a source of nutrients in the Venice Lagoon is also discussed and, though significant to the nutrient budget, is likely to be less important as the dominant control on SGD is recirculated seawater rather than freshwater. 2009 Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Rapaglia, John; Ferrarin, Christian; Zaggia, Luca; Moore, Willard S.; Umgiesser, Georg; Garcia-Solsona, Ester; Garcia-Orellana, Jordi; Masque, Pere
2010-01-01
The four naturally-occurring isotopes of radium were coupled with a previously evaluated hydrodynamic model to determine the apparent age of surface waters and to quantify submarine groundwater discharge (SGD) into the Venice Lagoon, Italy. Mean apparent age of water in the Venice Lagoon was calculated using the ratio of 224 Ra to 228 Ra determined from 30 monitoring stations and a mean pore water endmember. Average apparent age was calculated to be 6.0 d using Ra ratios. This calculated age was very similar to average residence time calculated for the same period using a hydrodynamic model (5.8 d). A mass balance of Ra was accomplished by quantifying each of the sources and sinks of Ra in the lagoon, with the unknown variable being attributed to SGD. Total SGD were calculated to be 4.1 ± 1.5, 3.8 ± 0.7, 3.0 ± 1.3, and 3.5 ± 1.0 x 10 10 L d -1 for 223,224,226,228 Ra, respectively, which are an order of magnitude larger than total mean fluvial discharge into the Venice Lagoon (3.1 x 10 9 L d -1 ). The SGD as a source of nutrients in the Venice Lagoon is also discussed and, though significant to the nutrient budget, is likely to be less important as the dominant control on SGD is recirculated seawater rather than freshwater.
Hydrodynamic Modelling of Municipal Solid Waste Residues in a Pilot Scale Fluidized Bed Reactor
Directory of Open Access Journals (Sweden)
João Cardoso
2017-11-01
Full Text Available The present study investigates the hydrodynamics and heat transfer behavior of municipal solid waste (MSW gasification in a pilot scale bubbling fluidized bed reactor. A multiphase 2-D numerical model following an Eulerian-Eulerian approach within the FLUENT framework was implemented. User defined functions (UDFs were coupled to improve hydrodynamics and heat transfer phenomena, and to minimize deviations between the experimental and numerical results. A grid independence study was accomplished through comparison of the bed volume fraction profiles and by reasoning the grid accuracy and computational cost. The standard deviation concept was used to determine the mixing quality indexes. Simulated results showed that UDFs improvements increased the accuracy of the mathematical model. Smaller size ratio of the MSW-dolomite mixture revealed a more uniform mixing, and larger ratios enhanced segregation. Also, increased superficial gas velocity promoted the solid particles mixing. Heat transfer within the fluidized bed showed strong dependence on the MSW solid particles sizes, with smaller particles revealing a more effective process.
Flock, Mario; Nelson, Richard P.; Turner, Neal J.; Bertrang, Gesa H.-M.; Carrasco-González, Carlos; Henning, Thomas; Lyra, Wladimir; Teague, Richard
2017-12-01
Planets are born in protostellar disks, which are now observed with enough resolution to address questions about internal gas flows. Magnetic forces are possibly drivers of the flows, but ionization state estimates suggest that much of the gas mass decouples from magnetic fields. Thus, hydrodynamical instabilities could play a major role. We investigate disk dynamics under conditions typical for a T Tauri system, using global 3D radiation-hydrodynamics simulations with embedded particles and a resolution of 70 cells per scale height. Stellar irradiation heating is included with realistic dust opacities. The disk starts in joint radiative balance and hydrostatic equilibrium. The vertical shear instability (VSI) develops into turbulence that persists up to at least 1600 inner orbits (143 outer orbits). Turbulent speeds are a few percent of the local sound speed at the midplane, increasing to 20%, or 100 m s-1, in the corona. These are consistent with recent upper limits on turbulent speeds from optically thin and thick molecular line observations of TW Hya and HD 163296. The predominantly vertical motions induced by the VSI efficiently lift particles upward. Grains 0.1 and 1 mm in size achieve scale heights greater than expected in isotropic turbulence. We conclude that while kinematic constraints from molecular line emission do not directly discriminate between magnetic and nonmagnetic disk models, the small dust scale heights measured in HL Tau and HD 163296 favor turbulent magnetic models, which reach lower ratios of the vertical kinetic energy density to the accretion stress.
A hydrodynamic formalism for Brownian systems
International Nuclear Information System (INIS)
Pina, E.; Rosales, M.A.
1981-01-01
A formal hydrodynamic approach to Brownian motion is presented and the corresponding equations are derived. Hydrodynamic quantities are expressed in terms of the physical variables characterizing the Brownian systems. Contact is made with the hydrodynamic model of Quantum Mechanics. (author)
Zegers Risopatron, G., Sr.; Navarro, L.; Montserrat, S., Sr.; McPhee, J. P.; Niño, Y.
2017-12-01
The geochemistry of water and sediments, coupled with hydrodynamic transport in mountainous channels, is of particular interest in central Chilean Andes due to natural occurrence of acid waters. In this paper, we present a coupled transport and geochemical model to estimate and understand transport processes and fate of minerals at the Yerba Loca Basin, located near Santiago, Chile. In the upper zone, water presentes low pH ( 3) and high concentrations of iron, aluminum, copper, manganese and zinc. Acidity and minerals are the consequence of water-rock interactions in hydrothermal alteration zones, rich in sulphides and sulphates, covered by seasonal snow and glaciers. Downstream, as a consequence of neutral to alkaline lateral water contributions (pH >7) along the river, pH increases and concentration of solutes decreases. The mineral transport model has three components: (i) a hydrodynamic model, where we use HEC-RAS to solve 1D Saint-Venant equations, (ii) a sediment transport model to estimate erosion and sedimentation rates, which quantify minerals transference between water and riverbed and (iii) a solute transport model, based on the 1D OTIS model which takes into account the temporal delay in solutes transport that typically is observed in natural channels (transient storage). Hydrochemistry is solved using PHREEQC, a software for speciation and batch reaction. Our results show that correlation between mineral precipitation and dissolution according to pH values changes along the river. Based on pH measurements (and according to literature) we inferred that main minerals in the water system are brochantite, ferrihydrite, hydrobasaluminite and schwertmannite. Results show that our model can predict the transport and fate of minerals and metals in the Yerba Loca Basin. Mineral dissolution and precipitation process occur for limited ranges of pH values. When pH values are increased, iron minerals (schwertmannite) are the first to precipitate ( 2.5
Use of hydrodynamic and benthic models for managing environmental impacts of marine aquaculture
DEFF Research Database (Denmark)
Henderson, A.; Gamito, S.; Karakassis, I.
2001-01-01
technical descriptions use of good and appropriate data; calibration; validation; sensitivity analysis; quality assurance; auditability and consideration of the operational needs of the user, the grower and/or the regulator. Models should have simplicity and clarity; be fit for purpose, be open to scrutiny......; be accessible, user-friendly and be used with caution. Current models are considered to be limited in scope but do cover the main hydrodynamic and particulate processes. The regulation and monitoring of finfish aquaculture involving the direct use of models is apparently restricted to relatively few countries...... on the transport of in-feed medicines is required. Keys to future developments across Europe include accessibility, setting of Environmental Quality Standards or targets, training and support for users, resources and structured research....
One-dimensional hydrodynamical kinetics model of a cylindrical DBD reactor with N2
International Nuclear Information System (INIS)
Flores-Moreno, M; De la Piedad-Beneitez, A; Barocio-Delgado, S; Mercado-Cabrera, A; López-Callejas, R; Peña-Eguiluz, R; Rodríguez-Méndez, B; Muñoz-Castro, A
2012-01-01
A numerical 1-D model of the chemical kinetics related hydrodynamics of room pressure N 2 plasma at 25 degrees C is reported. This generic discharge is assumed to take place between two cylindrical concentric electrodes, coated in a dielectric material, biased between 1 kV and 10 kV at 60Hz - 3kHz. The model includes the integration of particles conservation and the momentum equations as well as the local field approximation and the Poisson equations for the sake of completeness. The outcome shows that an accumulation of electrons takes place in the close vicinity of the higher voltage electrode, due to the electric field convergence to the internal electrode. Thus, this is a region of intense ionization whereas the generation of free radicals would occur away from the internal electrode. The model predicts no significant influence of the electric field on the heavier particles whose density remains practically constant.
Hydrodynamical description of collective flow
Huovinen, Pasi
2003-01-01
I review how hydrodynamical flow is related to the observed flow in ultrarelativistic heavy ion collisions and how initial conditions, equation of state and freeze-out temperature affect flow in hydrodynamical models.
Quantification model of the consequences of monetary policy shocks
Directory of Open Access Journals (Sweden)
Coralia Emilia POPA
2017-11-01
Full Text Available The monetary analysis based on the BVAR (Bayesian Vector Autoregression model is extremely important in the monetary policy implementation strategy, the information provided is important not only for the Central Bank, but also for the economic agents and the population. Therefore, conducting this analysis at the level of Romania helps to understand better the mechanism by which monetary policy is transmitted in order to achieve the set target, namely inflation targeting, but it also provides us with important information regarding the accession to the euro area. The model we are trying to test helps us understand through the correlations between the interest rate, GDP and the inflation rate how monetary policy responds to shocks. The model follows the methodology presented by Sims and Zha (1998 in the paper "Bayesian Methods for Dynamic Multivariate Models and Using the Bayesian Autoregressive Vector". In the analysis of this model, quarterly data for a minimum of three years, three variables are used to make the results relevant. The data needed to model the model are used in logarithmic form, except for the interest rate, and the outcome is applied to a differentiated premium operator. Of the variables used, the interest rate is the only one that does not allow seasonal adjustment.
Treatment of compounds and alloys in radiation hydrodynamics simulations of ablative laser loading
International Nuclear Information System (INIS)
Swift, Damian C.; Gammel, J. Tinka; Clegg, Samuel M.
2004-01-01
Different methods were compared for constructing models of the behavior of a prototype intermetallic compound, nickel aluminide, for use in radiation hydrodynamics simulations of shock wave generation by ablation induced by laser energy. The models included the equation of state, ionization, and radiation opacity. The methods of construction were evaluated by comparing the results of simulations of an ablatively generated shock wave in a sample of the alloy. The most accurate simulations were obtained using the 'constant number density' mixture model to calculate the equation of state and opacity, and Thomas-Fermi ionization. This model is consistent with that found to be most accurate for simulations of ablatively shocked elements
Feliciano, Julio Lebron; Kazemi, Amirkhosro; Carbajal, Gerardo; Tutkun, Murat; Bocanegra Evans, Humberto; Curet, Oscar; Castillo, Luciano
2017-11-01
Mangroves are tropical and subtropical trees that aid in protecting coastlines by dissipating the energy carried by tidal flows. These trees attenuate the devastating effects of powerful natural disasters such as hurricanes. Their roots form complex networks extending out of the water's surface and interacting with the tidal flow in estuaries, deltas, and other inter-tidal areas. This study focuses on the parametrization of the hydrodynamics of mangrove root-like geometries and the effect of the mangrove patch porosity and flexural stiffness. A multivariable non-dimensional empirical correlation is proposed to obtain a self-similar solution that describes the hydrodynamics. We introduced an effective-diameter length scale based on the wake signature of the mangrove root models. It was found that in this new dimensionless parameter, based on the Reynolds number and porosity, was able to characterize the drag coefficient. This analysis is complemented with high-resolution PIV experiments performed in a water tank under various flow and porosity conditions. Furthermore, we analyzed the Vortex-Induced Vibrations (VIVs) of the flexible mangrove patch that produce oscillating energy as a potential source for energy harvesting.
Hydrodynamic evolution of neutron star merger remnants
Liu, Men-Quan; Zhang, Jie
2017-11-01
Based on the special relativistic hydrodynamic equations and updated cooling function, we investigate the long-term evolution of neutron stars merger (NSM) remnants by a one-dimensional hydrodynamic code. Three NSM models from one soft equation of state, SFHo, and two stiff equations of state, DD2 and TM1, are used to compare their influences on the hydrodynamic evolution of remnants. We present the luminosity, mass and radius of remnants, as well as the velocity, temperature and density of shocks. For a typical interstellar medium (ISM) density with solar metallicity, we find that the NSM remnant from the SFHo model makes much more changes to ISM in terms of velocity, density and temperature distributions, compared with the case of DD2 and TM1 models. The maximal luminosity of the NSM remnant from the SFHo model is 3.4 × 1038 erg s-1, which is several times larger than that from DD2 and TM1 models. The NSM remnant from the SFHo model can maintain high luminosity (>1038 erg s-1) for 2.29 × 104 yr. Furthermore, the density and temperature of remnants at the maximal luminosity are not sensitive to the power of the original remnant. For the ISM with the solar metallicity and nH = 1 cm- 3, the density of the first shock ∼10-23 g cm-3 and the temperature ∼3 × 105 K in the maximal luminosity phase; The temperature of the first shock decreases and there is a thin 'dense' shell with density ∼10-21 g cm-3 after the maximal luminosity. These characteristics may be helpful for future observations of NSM remnants.
A data assimilation system combining CryoSat-2 data and hydrodynamic river models
Schneider, Raphael; Ridler, Marc-Etienne; Godiksen, Peter Nygaard; Madsen, Henrik; Bauer-Gottwein, Peter
2018-02-01
There are numerous hydrologic studies using satellite altimetry data from repeat-orbit missions such as Envisat or Jason over rivers. This study is one of the first examples for the combination of altimetry from drifting-ground track satellite missions, namely CryoSat-2, with a river model. CryoSat-2 SARIn Level 2 data is used to improve a 1D hydrodynamic model of the Brahmaputra River in South Asia, which is based on the Saint-Venant equations for unsteady flow and set up in the MIKE HYDRO River software. After calibration of discharge and water level the hydrodynamic model can accurately and bias-free represent the spatio-temporal variations of water levels. A data assimilation framework has been developed and linked with the model. It is a flexible framework that can assimilate water level data which are arbitrarily distributed in time and space. The setup has been used to assimilate CryoSat-2 water level observations over the Assam valley for the years 2010-2015, using an Ensemble Transform Kalman Filter (ETKF). Performance improvement in terms of discharge forecasting skill was then evaluated. For experiments with synthetic CryoSat-2 data the continuous ranked probability score (CRPS) was improved by up to 32%, whilst for experiments assimilating real data it could be improved by up to 10%. The developed methods are expected to be transferable to other rivers and altimeter missions. The model setup and calibration is based almost entirely on globally available remote sensing data.
Material model validation for laser shock peening process simulation
International Nuclear Information System (INIS)
Amarchinta, H K; Grandhi, R V; Langer, K; Stargel, D S
2009-01-01
Advanced mechanical surface enhancement techniques have been used successfully to increase the fatigue life of metallic components. These techniques impart deep compressive residual stresses into the component to counter potentially damage-inducing tensile stresses generated under service loading. Laser shock peening (LSP) is an advanced mechanical surface enhancement technique used predominantly in the aircraft industry. To reduce costs and make the technique available on a large-scale basis for industrial applications, simulation of the LSP process is required. Accurate simulation of the LSP process is a challenging task, because the process has many parameters such as laser spot size, pressure profile and material model that must be precisely determined. This work focuses on investigating the appropriate material model that could be used in simulation and design. In the LSP process material is subjected to strain rates of 10 6 s −1 , which is very high compared with conventional strain rates. The importance of an accurate material model increases because the material behaves significantly different at such high strain rates. This work investigates the effect of multiple nonlinear material models for representing the elastic–plastic behavior of materials. Elastic perfectly plastic, Johnson–Cook and Zerilli–Armstrong models are used, and the performance of each model is compared with available experimental results
Experimental models of sepsis and septic shock: an overview
Directory of Open Access Journals (Sweden)
Garrido Alejandra G.
2004-01-01
Full Text Available Sepsis remains a major cause of morbidity and mortality in surgical patients and trauma victims, mainly due to sepsis-induced multiple organ dysfunction. In contrast to preclinical studies, most clinical trials of promising new treatment strategies for sepsis have fails to demonstrate efficacy. Although many reasons could account for this discrepancy, the misinterpretation of preclinical data obtained from experimental studies, and especially the use of animal models that do not adequately mimic human sepsis may have been contributing factors. In this review, the benefits and limitations of various animal models of sepsis are discussed to clarify the extend to which findings are relevant to human sepsis, particularly with respect to the subsequent design and execution of clinical trials. Such models include intravascular infusion of endotoxin or live bacteria, bacterial peritonitis, cecal ligation and perforation, soft tissue infection, pneumonia or meningitis models, using different animal species including rats, mice, rabbits, dogs, pigs, sheep and nonhuman primates. Despite several limitations, animal models remain essential in the development of all new therapies for sepsis and septic shock, because they provide fundamental information about the pharmacokinetics, toxicity, and mechanism of drug action that cannot be duplicated by other methods. New therapeutic agents should be studies in infection models, even after the initiation of the septic process. Furthermore, debility conditions need to be reproduced to avoid the exclusive use of healthy animals, which often do not represent the human septic patient.
Parametric sensitivity of a CFD model concerning the hydrodynamics of trickle-bed reactor (TBR
Directory of Open Access Journals (Sweden)
Janecki Daniel
2016-03-01
Full Text Available The aim of the present study was to investigate the sensitivity of a multiphase Eulerian CFD model with respect to relations defining drag forces between phases. The mean relative error as well as standard deviation of experimental and computed values of pressure gradient and average liquid holdup were used as validation criteria of the model. Comparative basis for simulations was our own data-base obtained in experiments carried out in a TBR operating at a co-current downward gas and liquid flow. Estimated errors showed that the classical equations of Attou et al. (1999 defining the friction factors Fjk approximate experimental values of hydrodynamic parameters with the best agreement. Taking this into account one can recommend to apply chosen equations in the momentum balances of TBR.
Hydrodynamic modelling of flow patterns in a vortex reactor - Application to the mixing study
International Nuclear Information System (INIS)
Zoppe, B.; Lebaigue, O.; Ducros, F.; Bertrand, M.
2008-01-01
In the fuel reprocessing industry, an un-baffled magnetic rod-stirred multiphase reactor was developed for a precipitation operation. The flow generated in such a reactor is complex and the rotating agitator at the bottom of tank creates a vortex on the liquid surface. A Computational Fluid Dynamics (CFD) modelling is developed based on a Large Eddy Scale (LES) approach for turbulence effect simulation. The numerical simulations are performed in 3-dimensions using the Trio-U code developed at the Commissariat a l'Energie Atomique (Cea). The vortex study is based on an interface tracking method and the rotating magnetic rod is taken into account through a free IBC immersed boundary. The hydrodynamic modelling is in good agreement with Nagata's theory and will be validated from experimental data obtained by laser doppler velocimetry (LDV) measurements. (authors)
A hydrodynamical model of Kepler's supernova remnant constrained by x-ray spectra
International Nuclear Information System (INIS)
Ballet, J.; Arnaud, M.; Rothinfluo, R.; Chieze, J.P.; Magne, B.
1988-01-01
The remnant of the historical supernova observed by Kepler in 1604 was recently observed in x-rays by the EXOSAT satellite up to 10 keV. A strong Fe K emission line around 6.5 keV is readily apparent in the spectrum. From an analysis of the light curve of the SN, reconstructed from historical descriptions, a previous study proposed to classify it as type I. Standard models of SN I based on carbon deflagration of white dwarf predict the synthesis of about 0.5 M circle of iron in the ejecta. Observing the iron line is a crucial check for such models. It has been argued that the light curve of Sn II-L is very similar to that of SN I and that the original observations are compatible with either type. In view of this uncertainty the authors have run a hydrodynamics-ionization code for both SN II and SN I remnants
Understanding the Hydrodynamics of a Coastal Wetland with an Integrated Distributed Model
Zhang, Y.; Li, W.; Sun, G.
2017-12-01
Coastal wetlands linking ocean and terrestrial landscape provide important ecosystem services including flood mitigation, fresh water supply, erosion control, carbon sequestration, and wildlife habitats. Wetland hydrology is the major driving force for wetland formation, structure, function, and ecosystem services. The dynamics of wetland hydrology and energy budget are strongly affected by frequent inundation and drying of wetland soil and vegetation due to tide, sea level rise (SLR) and climatic variability (change). However, the quantitative representation of how the energy budget and groundwater variation of coastal wetlands respond to frequent water level fluctuation is limited, especially at regional scales. This study developed a physically based distributed wetland hydrological model by integrating coastal processes and considering the inundation influence on energy budget and ET. Analysis using in situ measurements and satellite data for a coastal wetland in North Carolina confirm that the model sufficiently captures the wetland hydrologic behaviors. The validated model was then applied to examine the wetland hydrodynamics under a 30-year historical climate forcing (1985-2014) for the wetland region. The simulation reveals that 43% of the study area has inundation events, 63% of which has a frequency higher than 50% each year. The canopy evaporation and transpiration decline dramatically when the inundation level exceeds the canopy height. Additionally, inundation causes about 10% increase of the net shortwave radiation. This study also demonstrates that the critical wetland zones highly influenced by the coastal processes spans 300-800 m from the coastline. The model developed in the study offers a new tool for understanding the complex wetland hydrodynamics in response to natural and human-induced disturbances at landscape to regional scales.
Lenartz, F.; Raick, C.; Soetaert, K.E.R.; Grégoire, M.
2007-01-01
The Ensemble Kalman filter (EnKF) has been applied to a 1-D complex ecosystem model coupled with a hydrodynamic model of the Ligurian Sea. In order to improve the performance of the EnKF, an ensemble subsampling strategy has been used to better represent the covariance matrices and a pre-analysis
DEFF Research Database (Denmark)
Hinrichsen, Hans-Harald; Kraus, Gerd; Böttcher, Uwe
2009-01-01
Knowledge of the spatial and temporal distribution of juvenile cod is essential to closing the life cycle in population dynamic models, and it is a prerequisite for the design of Marine Protected Areas (MPAs) aiming at the protection of juveniles. In this study, we use a hydrodynamic model to exa...
International Nuclear Information System (INIS)
Mastrangelo, Victor.
1977-01-01
A thermo-hydrodynamic neutron interaction model for permanent working conditions is developed in the case of closed circuits (boiling water reactors) and open circuits (pressurized water reactors). Two numerical convergence acceleration methods are then worked out for the resolution of linear problems by successive iterations. A physical study is devoted to the convergence of the thermo-hydrodynamic neutron interaction process. The model developed is applied to the calculation of the power distribution for the core of a 980 MWe BWR-6 type boiling water power station and to the study of normal and accidental working configurations of the pressurized water core of a 900 MWe PWR-CP1 unit [fr
Extended charge banking model of dual path shocks for implantable cardioverter defibrillators.
Dosdall, Derek J; Sweeney, James D
2008-08-01
Single path defibrillation shock methods have been improved through the use of the Charge Banking Model of defibrillation, which predicts the response of the heart to shocks as a simple resistor-capacitor (RC) circuit. While dual path defibrillation configurations have significantly reduced defibrillation thresholds, improvements to dual path defibrillation techniques have been limited to experimental observations without a practical model to aid in improving dual path defibrillation techniques. The Charge Banking Model has been extended into a new Extended Charge Banking Model of defibrillation that represents small sections of the heart as separate RC circuits, uses a weighting factor based on published defibrillation shock field gradient measures, and implements a critical mass criteria to predict the relative efficacy of single and dual path defibrillation shocks. The new model reproduced the results from several published experimental protocols that demonstrated the relative efficacy of dual path defibrillation shocks. The model predicts that time between phases or pulses of dual path defibrillation shock configurations should be minimized to maximize shock efficacy. Through this approach the Extended Charge Banking Model predictions may be used to improve dual path and multi-pulse defibrillation techniques, which have been shown experimentally to lower defibrillation thresholds substantially. The new model may be a useful tool to help in further improving dual path and multiple pulse defibrillation techniques by predicting optimal pulse durations and shock timing parameters.
International Nuclear Information System (INIS)
Fauvel, E.
2002-01-01
This report deals with a transpiring wall reactor for supercritical water oxidation of organic effluents. The singularity of the reactor lies on the inner porous tube made of alumina to minimise both limiting problems, corrosion and salt precipitation. The presence of the inner tube implies a rather complex hydrodynamics. Thus, an hydrodynamic study was performed, in an original way, in a supercritical fluid using the method of the residence time distribution. It enabled to determine the hydrodynamic model of the reactor. Moreover, an inspecting device of the resistance of the inner tube to thermal gradients was developed. Lastly, the performances of the transpiring wall reactor were tested on model compounds such as sodium sulphate and the mixture of dodecane/tributylphosphate. (author) [fr
Almukhametova, E. M.; Gizetdinov, I. A.
2018-05-01
Development of most deposits in Russia is accompanied with a high level of crude water cut. More than 70% of the operating well count of Barsukovskoye deposit operates with water; about 12% of the wells are characterized by a saturated water cut; many wells with high water cut are idling. To optimize the current FPM system of the Barsukovskoye deposit, a calculation method over a hydrodynamic model was applied with further analysis of hydrodynamic connectivity between the wells. A plot was selected, containing several wells with water cut going ahead of reserve recovery rate; injection wells, exerting the most influence onto the selected producer wells, were determined. Then, several variants were considered for transformation of the FPM system of this plot. The possible cases were analyzed with the hydrodynamic model with further determination of economic effect of each of them.
Bódi, Erika; Buday, Tamás; McIntosh, Richard William
2013-04-01
Defining extraction-modified flow patterns with hydrodynamic models is a pivotal question in preserving groundwater resources regarding both quality and quantity. Modeling is the first step in groundwater protection the main result of which is the determination of the protective area depending on the amount of extracted water. Solid models have significant effects on hydrodynamic models as they are based on the solid models. Due to the legislative regulations, on protection areas certain restrictions must be applied which has firm consequences on economic activities. In Hungarian regulations there are no clear instructions for the establishment of either geological or hydrodynamic modeling, however, modeling itself is an obligation. Choosing the modeling method is a key consideration for further numerical calculations and it is decisive regarding the shape and size of the groundwater protection area. The geometry of hydrodynamic model layers is derived from the solid model. There are different geological approaches including lithological and sequence stratigraphic classifications furthermore in the case of regional models, formation-based hydrostratigraphic units are also applicable. Lithological classification is based on assigning and mapping of lithotypes. When the geometry (e.g. tectonic characteristics) of the research area is not known, horizontal bedding is assumed the probability of which can not be assessed based on only lithology. If the geological correlation is based on sequence stratigraphic studies, the cyclicity of sediment deposition is also considered. This method is more integrated thus numerous parameters (e.g. electrofacies) are taken into consideration studying the geological conditions ensuring more reliable modeling. Layers of sequence stratigraphic models can be either lithologically homogeneous or they may include greater cycles of sediments containing therefore several lithological units. The advantage of this is that the modeling can
A hydrodynamic model of nearshore waves and wave-induced currents
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Ahmed Khaled Seif
2011-09-01
Full Text Available In This study develops a quasi-three dimensional numerical model of wave driven coastal currents with accounting the effects of the wave-current interaction and the surface rollers. In the wave model, the current effects on wave breaking and energy dissipation are taken into account as well as the wave diffraction effect. The surface roller associated with wave breaking was modeled based on a modification of the equations by Dally and Brown (1995 and Larson and Kraus (2002. Furthermore, the quasi-three dimensional model, which based on Navier-Stokes equations, was modified in association with the surface roller effect, and solved using frictional step method. The model was validated by data sets obtained during experiments on the Large Scale Sediment Transport Facility (LSTF basin and the Hazaki Oceanographical Research Station (HORS. Then, a model test against detached breakwater was carried out to investigate the performance of the model around coastal structures. Finally, the model was applied to Akasaki port to verify the hydrodynamics around coastal structures. Good agreements between computations and measurements were obtained with regard to the cross-shore variation in waves and currents in nearshore and surf zone.
Smoothed-particle-hydrodynamics modeling of dissipation mechanisms in gravity waves.
Colagrossi, Andrea; Souto-Iglesias, Antonio; Antuono, Matteo; Marrone, Salvatore
2013-02-01
The smoothed-particle-hydrodynamics (SPH) method has been used to study the evolution of free-surface Newtonian viscous flows specifically focusing on dissipation mechanisms in gravity waves. The numerical results have been compared with an analytical solution of the linearized Navier-Stokes equations for Reynolds numbers in the range 50-5000. We found that a correct choice of the number of neighboring particles is of fundamental importance in order to obtain convergence towards the analytical solution. This number has to increase with higher Reynolds numbers in order to prevent the onset of spurious vorticity inside the bulk of the fluid, leading to an unphysical overdamping of the wave amplitude. This generation of spurious vorticity strongly depends on the specific kernel function used in the SPH model.
Huang, Feimin; Li, Tianhong; Yu, Huimin; Yuan, Difan
2018-06-01
We are concerned with the global existence and large time behavior of entropy solutions to the one-dimensional unipolar hydrodynamic model for semiconductors in the form of Euler-Poisson equations in a bounded interval. In this paper, we first prove the global existence of entropy solution by vanishing viscosity and compensated compactness framework. In particular, the solutions are uniformly bounded with respect to space and time variables by introducing modified Riemann invariants and the theory of invariant region. Based on the uniform estimates of density, we further show that the entropy solution converges to the corresponding unique stationary solution exponentially in time. No any smallness condition is assumed on the initial data and doping profile. Moreover, the novelty in this paper is about the unform bound with respect to time for the weak solutions of the isentropic Euler-Poisson system.
Dorodnitsyn, Anton; Kallman, Tim; Bisno\\vatyiI-Kogan, Gennadyi
2011-01-01
We explore a detailed model in which the active galactic nucleus (AGN) obscuration results from the extinction of AGN radiation in a global ow driven by the pressure of infrared radiation on dust grains. We assume that external illumination by UV and soft X-rays of the dusty gas located at approximately 1pc away from the supermassive black hole is followed by a conversion of such radiation into IR. Using 2.5D, time-dependent radiation hydrodynamics simulations in a ux-limited di usion approximation we nd that the external illumination can support a geometrically thick obscuration via out ows driven by infrared radiation pressure in AGN with luminosities greater than 0:05 L(sub edd) and Compton optical depth, Tau(sub T) approx > & 1.
Rasyif, Teuku M.; Kato, Shigeru; Syamsidik, Okabe, Takumi
2017-10-01
Numerical simulation is one of the useful tools to analyze natural phenomena in the earth such as the tsunami disaster. Several numerical models can simulate the tsunami wave from its generation, propagation, and inundation. However, most tsunami models do not include the sediment transport module. The tsunami wave actually induces a lot of sediment during the propagation in the coastal area. In the case of Indian Ocean Tsunami in 2004, massive morphological changes were caused by the tsunami waves around Sumatra coast. In Aceh, some areas eroded by the tsunami wave were living place for a local community. It is indispensable for the resident in the coastal area to estimate the risk of morphological changes due to a tsunami wave. Therefore, a model that can investigate the morphological changes due tsunami wave is necessary. The result of this model can be used to consider a countermeasure for tsunami wave impact in the coastal area, such as land-use management and planning. The COMCOT-SED model had been developed by several researchers. This model combines the hydrodynamic module and the sediment module. The aim of this study is to get general information about performance of the COMCOT-SED model and to modify the model for more accurate results. Firstly, the model was demonstrated in the ideal condition to confirm the model validity. Then, we evaluated the model performance comparing the model results and the laboratory experiment data which was conducted by other researcher. The authors found that the results of water level and bottom profile by the original model in the ideal condition are not suitable. The model modification will give us more suitable results. The modified model will be applied to simulate the tsunami wave and sediment transport in the small area.
Hydrodynamic optical soliton tunneling
Sprenger, P.; Hoefer, M. A.; El, G. A.
2018-03-01
A notion of hydrodynamic optical soliton tunneling is introduced in which a dark soliton is incident upon an evolving, broad potential barrier that arises from an appropriate variation of the input signal. The barriers considered include smooth rarefaction waves and highly oscillatory dispersive shock waves. Both the soliton and the barrier satisfy the same one-dimensional defocusing nonlinear Schrödinger (NLS) equation, which admits a convenient dispersive hydrodynamic interpretation. Under the scale separation assumption of nonlinear wave (Whitham) modulation theory, the highly nontrivial nonlinear interaction between the soliton and the evolving hydrodynamic barrier is described in terms of self-similar, simple wave solutions to an asymptotic reduction of the Whitham-NLS partial differential equations. One of the Riemann invariants of the reduced modulation system determines the characteristics of a soliton interacting with a mean flow that results in soliton tunneling or trapping. Another Riemann invariant yields the tunneled soliton's phase shift due to hydrodynamic interaction. Soliton interaction with hydrodynamic barriers gives rise to effects that include reversal of the soliton propagation direction and spontaneous soliton cavitation, which further suggest possible methods of dark soliton control in optical fibers.
Three-dimensional Modeling of Tidal Hydrodynamics in the San Francisco Estuary
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Edward S. Gross
2010-01-01
Full Text Available Simulations of circulation in the San Francisco Estuary were performed with the three-dimensional TRIM3D hydrodynamic model using a generic length scale turbulence closure. The model was calibrated to reproduce observed tidal elevations, tidal currents, and salinity observations in the San Francisco Estuary using data collected during 1996-1998, a period of high and variable freshwater flow. It was then validated for 1994-1995, with emphasis on spring of 1994, a period of intensive data collection in the northern estuary. The model predicts tidal elevations and tidal currents accurately, and realistically predicts salinity at both the seasonal and tidal time scales. The model represents salt intrusion into the estuary accurately, and therefore accurately represents the salt balance. The model’s accuracy is adequate for its intended purposes of predicting salinity, analyzing gravitational circulation, and driving a particle-tracking model. Two applications were used to demonstrate the utility of the model. We estimated the components of the longitudinal salt flux and examined their dependence on flow conditions, and compared predicted salt intrusion with estimates from two empirical models.
Directory of Open Access Journals (Sweden)
2016-01-01
Full Text Available This article presents the results of the hydrodynamic parameters of radio-controlled models (RCM of the aircraft with the landing gear on an air cushion (REFERENCED obtained during tests in the water tank of TSAGI NIMC on land- ing modes with varying alignment and pressure in air cushion chassis on calm and disturbed water surfaces.ACLG’s RCM is based on the Froude criterion. The experimental data of the real aircraft Dingo, LMS, An-26, C-130 Hercules (size, weight, thrust parameters were processed. Tests were carried out, using the standard testbed, utiliz- ing the dynamically-corresponding models in the water tank. Drag best value rate while travelling along the smooth water was reached at the rear centering, with balloon pressure on the water of 700 Pa. In this case, the hump drag, at velocity of 2 mps, does not exceed 29 Newtons (hydrodynamic fineness on the ‘drag hump’ is, Кг=13,5, while at velocity of 10 mps, the drag is 30 Newtons, at Кг =13.The most unfavourable mode of motion is the one with configuration of lowered pressure in the balloons (400 Pa.In these cases, the Кг = 6,5. At motion with yaw angle of 10º, the drag rate meaning practically stands stable (Кг = 13,1, while at 20º it grows (Кг = 10,6.At motion along the waved surface, the critical wave length equals to two thirds of the ACU, while drag raises by the quarter, compared to other wave types. Such vehicles can be used in the hard-to-reach regions of the Russian Federation.
International Nuclear Information System (INIS)
Wu, Chao; Kanthi Kiran Dasika; Chen, Yitung; Moujaes, Samir
2002-01-01
Using liquid Lead-Bismuth Eutectic (LBE) as coolant in nuclear systems has been studied for more than 50 years. And LBE has many unique nuclear, thermo physical and chemical attributes which are attractive for practical application. But, corrosion is one of the greatest concerns in using liquid Lead-Bismuth Eutectic (LBE) as spallation target in the Accelerator-driven Transmutation of Waste (ATW) program. Los Alamos National Laboratory has designed and built the Liquid Lead-Bismuth Materials Test Loop (MTL) to study the materials behavior in a flow of molten LBE. A difference of 100 deg. C was designed between the coldest and the hottest parts at a nominal flow rate of 8.84 GPM. Liquid LBE flow was activated by a mechanical sump pump or by natural convection. In order to maintain a self-healing protective film on the surface of the stainless steel pipe, a certain concentration of oxygen has to be maintained in the liquid metal. Therefore, it is of importance to understand what the oxygen concentrations are in the LBE loop related to the corrosion effects on the metal surface, the temperature profiles, the flow rates, and diffusion rates through the metal surface. The chemical kinetics also needs to be fully understood in the corrosion processes coupled with the hydrodynamics. The numerical simulation will be developed and used to analyze the system corrosion effects with different kind of oxygen concentrations, flow rates, chemical kinetics, and geometries. The hydrodynamics modeling of using computational fluid dynamics will provide the necessary the levels of oxygen and corrosion products close to the boundary or surface. This paper presents an approach towards the above explained tasks by analyzing the reactions between the Lead and oxygen at a couple of sections in the MTL. Attempt is also made to understand the surface chemistry by choosing an example model and estimating the near wall surface concentration values for propane and oxygen. (authors)
Boosting flood warning schemes with fast emulator of detailed hydrodynamic models
Bellos, V.; Carbajal, J. P.; Leitao, J. P.
2017-12-01
Floods are among the most destructive catastrophic events and their frequency has incremented over the last decades. To reduce flood impact and risks, flood warning schemes are installed in flood prone areas. Frequently, these schemes are based on numerical models which quickly provide predictions of water levels and other relevant observables. However, the high complexity of flood wave propagation in the real world and the need of accurate predictions in urban environments or in floodplains hinders the use of detailed simulators. This sets the difficulty, we need fast predictions that meet the accuracy requirements. Most physics based detailed simulators although accurate, will not fulfill the speed demand. Even if High Performance Computing techniques are used (the magnitude of required simulation time is minutes/hours). As a consequence, most flood warning schemes are based in coarse ad-hoc approximations that cannot take advantage a detailed hydrodynamic simulation. In this work, we present a methodology for developing a flood warning scheme using an Gaussian Processes based emulator of a detailed hydrodynamic model. The methodology consists of two main stages: 1) offline stage to build the emulator; 2) online stage using the emulator to predict and generate warnings. The offline stage consists of the following steps: a) definition of the critical sites of the area under study, and the specification of the observables to predict at those sites, e.g. water depth, flow velocity, etc.; b) generation of a detailed simulation dataset to train the emulator; c) calibration of the required parameters (if measurements are available). The online stage is carried on using the emulator to predict the relevant observables quickly, and the detailed simulator is used in parallel to verify key predictions of the emulator. The speed gain given by the emulator allows also to quantify uncertainty in predictions using ensemble methods. The above methodology is applied in real
Laser-Generated Shocks and Bubbles as Laboratory-Scale Models of Underwater Explosions
Directory of Open Access Journals (Sweden)
Theodore G. Jones
2003-01-01
Full Text Available Underwater shocks and bubbles were generated using a high energy pulsed laser system. The advantages of this experimental approach are: (1 precisely controlled and measured experimental conditions; (2 improved diagnostics, including extensive imaging capabilities; (3 unique experiments, including a simultaneously detonated line charge; and (4 the ability to provide validation quality data for hydrodynamic simulation codes. Bubble sensitivity to variation of several experimental parameters was examined. Numerical simulations were performed corresponding to the experimental shots, showing that empirical bubble theory, experimental bubble data, and simulations were all in good agreement.
Experimental investigation of shock wave diffraction over a single- or double-sphere model
Zhang, L. T.; Wang, T. H.; Hao, L. N.; Huang, B. Q.; Chen, W. J.; Shi, H. H.
2017-01-01
In this study, the unsteady drag produced by the interaction of a shock wave with a single- and a double-sphere model is measured using imbedded accelerometers. The shock wave is generated in a horizontal circular shock tube with an inner diameter of 200 mm. The effect of the shock Mach number and the dimensionless distance between spheres is investigated. The time-history of the drag coefficient is obtained based on Fast Fourier Transformation (FFT) band-block filtering and polynomial fitting of the measured acceleration. The measured peak values of the drag coefficient, with the associated uncertainty, are reported.
Development and application of an eco-hydrodynamic model for radionuclides in a brackish lake
International Nuclear Information System (INIS)
Ueda, Shinji; Kondo, Kunio; Inaba, Jiro; Hisamatsu, Shun'ichi
2007-01-01
This study was intended to develop a computer code of an eco-hydrodynamic model for radionuclides in Lake Obuchi, which is a brackish lake in Rokkasho, Aomori Prefecture and adjacent to nuclear fuel cycle facilities including the first commercial spent-nuclear-fuel reprocessing plant in Japan. Radionuclides introduced into the lake are transferred not only by physical advection an diffusion, but also by bio-chemical activities. The model was planned to include the effects of the low trophic level ecosystem on the transfer of radionuclides as well as the hydraulic movements in the lake. Various parameters necessary for the model description were collected from the lake during 2001 to 2005. Water flow in the lake, including input from the Futamata River and tidal flow from the Pacific Ocean, was simulated by a 3D-hydrodynamic model, and an ecosystem model including phytoplankton and zooplankton was incorporated into the water flow model. Calculations of water movement were carried out using climatic, physicochemical and ecological data collected during January 2001 to December 2002. The numerical simulation results of water current and salinity agreed well with field measurement data. The ecosystem model simulated well the mass fluxes of P, N and observed in the field. The estimated 3 He and 137 Cs concentrations in lake water were in good agreement with the measured data, because the concentrations of both radionuclides were controlled by the mixture of seawater as the higher side member and fresh water as the lower side member. Material balance calculations of both radionuclides in the lake ecosystem showed that they were mainly in the form of dissolved inorganic matter (DIM). However, the fallout 137 Cs deposition pattern in the lake sediment predicted by a long-term simulation did not agree with the measured one. Although input of 137 Cs from the watershed was included in the simulation, its residence time in the watershed was not considered. This meant that
A non-local shell model of hydrodynamic and magnetohydrodynamic turbulence
Energy Technology Data Exchange (ETDEWEB)
Plunian, F [Laboratoire de Geophysique Interne et Tectonophysique, CNRS, Universite Joseph Fourier, Maison des Geosciences, BP 53, 38041 Grenoble Cedex 9 (France); Stepanov, R [Institute of Continuous Media Mechanics, Korolyov 1, 614013 Perm (Russian Federation)
2007-08-15
We derive a new shell model of magnetohydrodynamic (MHD) turbulence in which the energy transfers are not necessarily local. Like the original MHD equations, the model conserves the total energy, magnetic helicity, cross-helicity and volume in phase space (Liouville's theorem) apart from the effects of external forcing, viscous dissipation and magnetic diffusion. The model of hydrodynamic (HD) turbulence is derived from the MHD model setting the magnetic field to zero. In that case the conserved quantities are the kinetic energy and the kinetic helicity. In addition to a statistically stationary state with a Kolmogorov spectrum, the HD model exhibits multiscaling. The anomalous scaling exponents are found to depend on a free parameter {alpha} that measures the non-locality degree of the model. In freely decaying turbulence, the infra-red spectrum also depends on {alpha}. Comparison with theory suggests using {alpha} = -5/2. In MHD turbulence, we investigate the fully developed turbulent dynamo for a wide range of magnetic Prandtl numbers in both kinematic and dynamic cases. Both local and non-local energy transfers are clearly identified.
Investigation of the hydrodynamic model test of forced rolling for a barge using PIV
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WANG Xiaoqiang
2017-03-01
Full Text Available In order to study the physical details of viscous flow in ship roll motions and improve the accuracy of ship roll damping numerical simulation, the application of the Particle Image Velocimetry (PIV technique is investigated in model tests of forced ship rolling in calm water. The hydrodynamic force and flow field at the bilge region are simultaneously measured for barges at different amplitudes and frequencies in which the self-made forced rolling facility was used. In the model test, the viscous flow variation with the time around the bilge region was studied during ship rolling motion. The changes in ship roll damping coefficients with the rolling amplitude and period were also investigated. A comparison of the model test results with the Computational Fluid Dynamics(CFDresults shows that the numerical ship roll damping coefficients agree well with the model test results, while the differences in the local flow details exist between the CFD results and model test results. Further research into the model test technique and CFD application is required.
Shock-induced electrical activity in polymeric solids. A mechanically induced bond scission model
International Nuclear Information System (INIS)
Graham, R.A.
1979-01-01
When polymeric solids are subjected to high-pressure shock loading, two anomalous electrical phenomena, shock-induced conduction and shock-induced polarization, are observed. The present paper proposes a model of mechanically induced bond scission within the shock front to account for the effects. An experimental study of shock-induced polarization in poly(pyromellitimide) (Vespel SP-1) is reported for shock compressions from 17 to 23% (pressures from 2.5 to 5.4 GPa). Poly(pyromellitimide) is found to be a strong generator of such polarization and the polarization is found to reflect an irreversible or highly hysteretic process. The present measurements are combined with prior measurements to establish a correlation between monomer structure and strength of shock-induced polarization; feeble signals are observed in the simpler monomer repeat units of poly(tetrafluoroethylene) and polyethylene while the strongest signals are observed in more complex monomers of poly(methyl methacrylate) and poly(pyromellitimide). It is also noted that there is an apparent correlation between shock-induced conduction and shock-induced polarization. Such shock-induced electrical activity is also found to be well correlated with the propensity for mechanical bond scission observed in experiments carried out in conventional mechanochemical studies. The bond scission model can account for characteristics observed for electrical activity in shock-loaded polymers and their correlation to monomer structure. Localization of elastic energy within the monomer repeat unit or along the main chain leads to the different propensities for bond scission and resulting shock-induced electrical activity
International Nuclear Information System (INIS)
Colgate, S.A.
1981-01-01
The explosion of a star supernova occurs at the end of its evolution when the nuclear fuel in its core is almost, or completely, consumed. The star may explode due to a small residual thermonuclear detonation, type I SN or it may collapse, type I and type II SN leaving a neutron star remnant. The type I progenitor should be thought to be an old accreting white dwarf, 1.4 M/sub theta/, with a close companion star. A type II SN is thought to be a massive young star 6 to 10 M/sub theta/. The mechanism of explosion is still a challenge to our ability to model the most extreme conditions of matter and hydrodynamics that occur presently and excessively in the universe. 39 references
Renilson, Martin
2015-01-01
This book adopts a practical approach and presents recent research together with applications in real submarine design and operation. Topics covered include hydrostatics, manoeuvring, resistance and propulsion of submarines. The author briefly reviews basic concepts in ship hydrodynamics and goes on to show how they are applied to submarines, including a look at the use of physical model experiments. The issues associated with manoeuvring in both the horizontal and vertical planes are explained, and readers will discover suggested criteria for stability, along with rudder and hydroplane effectiveness. The book includes a section on appendage design which includes information on sail design, different arrangements of bow planes and alternative stern configurations. Other themes explored in this book include hydro-acoustic performance, the components of resistance and the effect of hull shape. Readers will value the author’s applied experience as well as the empirical expressions that are presented for use a...
Nova experiments to investigate hydrodynamic instabilities in the solid state
International Nuclear Information System (INIS)
Kalantar, D.H.; Remington, B.A.; Chandler, E.A.; Colvin, J.D.; Griswold, D.L.; Turner, R.E.; Weber, S.V.; Wiley, L.G.
1997-01-01
Experiments were done to shock compress and accelerate copper foils at peak presssures of ∼3 Mbar above and below the melt temperature to study the effects of material strength on hydrodynamic instabilities. An x-ray drive generated in a hohlraum target was used to generate the shock wave profiles. The growth of a preimposed perturbation at an embedded interface is diagnosed by x-ray radiography. Results obtained using a high contrastshaped laser pulse show that the growth of the modulation is delayed compared to fluid simulations,which could be due to material strength stabilization. In contrast, when a copper foil is placed above the melt temperature at >3 Mbar with a single shock, it melts upon compression and the modulation growth is consistent with fluid modeling. Experimental results from copper shocked to 3 Mbar both below and above the melt temperature are presented and compared with simulation
Solitonic Dispersive Hydrodynamics: Theory and Observation
Maiden, Michelle D.; Anderson, Dalton V.; Franco, Nevil A.; El, Gennady A.; Hoefer, Mark A.
2018-04-01
Ubiquitous nonlinear waves in dispersive media include localized solitons and extended hydrodynamic states such as dispersive shock waves. Despite their physical prominence and the development of thorough theoretical and experimental investigations of each separately, experiments and a unified theory of solitons and dispersive hydrodynamics are lacking. Here, a general soliton-mean field theory is introduced and used to describe the propagation of solitons in macroscopic hydrodynamic flows. Two universal adiabatic invariants of motion are identified that predict trapping or transmission of solitons by hydrodynamic states. The result of solitons incident upon smooth expansion waves or compressive, rapidly oscillating dispersive shock waves is the same, an effect termed hydrodynamic reciprocity. Experiments on viscous fluid conduits quantitatively confirm the soliton-mean field theory with broader implications for nonlinear optics, superfluids, geophysical fluids, and other dispersive hydrodynamic media.
Integrating hydrodynamic models and COSMO-SkyMed derived products for flood damage assessment
Giuffra, Flavio; Boni, Giorgio; Pulvirenti, Luca; Pierdicca, Nazzareno; Rudari, Roberto; Fiorini, Mattia
2015-04-01
observe the temporal evolution of the event (e.g. the water receding). In this paper, the first outcomes of a study aiming at combining COSMO-SkyMed derived flood maps with hydrodynamic models are presented. The study is carried out within the framework of the EO-based CHange detection for Operational Flood Management (ECHO-FM) project, funded by the Italian Space Agency (ASI) as part of the research activities agreed in the cooperation between ASI and the Japan Aerospace Exploration Agency (JAXA). The flood that hit the region of Shkodër, in Albania, on January 2010, is considered as test case. The work focuses on the utility of a dense temporal series of SAR data, such as that available through CSK for this case study, used in combination with a hydrodynamic model to monitor over a long time (in the order of 3 weeks) the natural drainage of the Shkodër floodplain. It is shown that by matching the outputs of the model to SAR observations, the hydrodynamic inconsistencies in CSK estimates can be corrected.
International Nuclear Information System (INIS)
Khangaonkar, Tarang; Yang, Zhaoqing
2011-01-01
Estuarine and coastal hydrodynamic processes are sometimes neglected in the design and planning of nearshore restoration actions. Despite best intentions, efforts to restore nearshore habitats can result in poor outcomes if circulation and transport which also affect freshwater-saltwater interactions are not properly addressed. Limitations due to current land use can lead to selection of sub-optimal restoration alternatives that may result in undesirable consequences, such as flooding, deterioration of water quality, and erosion, requiring immediate remedies and costly repairs. Uncertainty with achieving restoration goals, such as recovery of tidal exchange, supply of sediment and nutrients, and establishment of fish migration pathways, may be minimized by using numerical models designed for application to the nearshore environment. A high resolution circulation and transport model of the Puget Sound, in the state of Washington, was developed to assist with nearshore habitat restoration design and analysis, and to answer the question 'can we achieve beneficial restoration outcomes at small local scale, as well as at a large estuary-wide scale?' The Puget Sound model is based on an unstructured grid framework to define the complex Puget Sound shoreline using a finite volume coastal ocean model (FVCOM). The capability of the model for simulating the important nearshore processes, such as circulation in complex multiple tidal channels, wetting and drying of tide flats, and water quality and sediment transport as part of restoration feasibility, are illustrated through examples of restoration projects in Puget Sound.
Carlesi, Edoardo; Knebe, Alexander; Lewis, Geraint F.; Wales, Scott; Yepes, Gustavo
2014-04-01
We present the results of a series of adiabatic hydrodynamical simulations of several quintessence models (both with a free and an interacting scalar field) in comparison to a standard Λ cold dark matter cosmology. For each we use 2 × 10243 particles in a 250 h-1 Mpc periodic box assuming 7-year Wilkinson Microwave Anisotropy Probe cosmology. In this work we focus on the properties of haloes in the cosmic web at z = 0. The web is classified into voids, sheets, filaments and knots depending on the eigenvalues of the velocity shear tensor, which are an excellent proxy for the underlying overdensity distribution. We find that the properties of objects classified according to their surrounding environment show a substantial dependence on the underlying cosmology; for example, while Vmax shows average deviations of ≈5 per cent across the different models when considering the full halo sample, comparing objects classified according to their environment, the size of the deviation can be as large as 20 per cent. We also find that halo spin parameters are positively correlated to the coupling, whereas halo concentrations show the opposite behaviour. Furthermore, when studying the concentration-mass relation in different environments, we find that in all cosmologies underdense regions have a larger normalization and a shallower slope. While this behaviour is found to characterize all the models, differences in the best-fitting relations are enhanced in (coupled) dark energy models, thus providing a clearer prediction for this class of models.
A modified hydrodynamic model for routing unsteady flow in a river having piedmont zone
Directory of Open Access Journals (Sweden)
Patowary Sudarshan
2017-03-01
Full Text Available Existence of piedmont zone in a river bed is a critical parameter from among numerous variations of topographical, geological and geographical conditions that can significantly influence the river flow scenario. Downstream flow situation assessed by routing of upstream hydrograph may yield higher flow depth if existence of such high infiltration zone is ignored and therefore it is a matter of concern for water resources planning and flood management. This work proposes a novel modified hydrodynamic model that has the potential to accurately determine the flow scenario in presence of piedmont zone. The model has been developed using unsteady free surface flow equations, coupled with Green-Ampt infiltration equation as governing equation. For solution of the governing equations Beam and Warming implicit finite difference scheme has been used. The proposed model was first validated from the field data of Trout Creek River showing excellent agreement. The validated model was then applied to a hypothetical river reach commensurate with the size of major tributaries of Brahmaputra Basin of India. Results indicated a 10% and 14% difference in the maximum value of discharge and depth hydrograph in presence and absence of piedmont zone respectively. Overall this model was successfully used to accurately predict the effect of piedmont zone on the unsteady flow in a river.
Numerical modeling of hydrodynamics and sediment transport—an integrated approach
Gic-Grusza, Gabriela; Dudkowska, Aleksandra
2017-10-01
Point measurement-based estimation of bedload transport in the coastal zone is very difficult. The only way to assess the magnitude and direction of bedload transport in larger areas, particularly those characterized by complex bottom topography and hydrodynamics, is to use a holistic approach. This requires modeling of waves, currents, and the critical bed shear stress and bedload transport magnitude, with a due consideration to the realistic bathymetry and distribution of surface sediment types. Such a holistic approach is presented in this paper which describes modeling of bedload transport in the Gulf of Gdańsk. Extreme storm conditions defined based on 138-year NOAA data were assumed. The SWAN model (Booij et al. 1999) was used to define wind-wave fields, whereas wave-induced currents were calculated using the Kołodko and Gic-Grusza (2015) model, and the magnitude of bedload transport was estimated using the modified Meyer-Peter and Müller (1948) formula. The calculations were performed using a GIS model. The results obtained are innovative. The approach presented appears to be a valuable source of information on bedload transport in the coastal zone.
Fractal and prefractal geometric models have substantial potential of contributing to the analysis of flow and transport in porous media such as soils and reservoir rocks. In this study, geometric and hydrodynamic parameters of saturated 3D mass and pore-solid prefractal porous media were characteri...
International Nuclear Information System (INIS)
Koronovskij, A.A.; Rempen, I.S.; Khramov, A.E.
2003-01-01
The possibility of controlling the chaos in the electron beam with the supercritical current in the hydrodynamic model of the Pierce diode through the continuous feedback; the methodology of controlling the chaotic dynamics through stabilization of the unstable equilibrium state in the distributed active medium is proposed [ru
Hydrodynamical model and experimental results of a calcium looping cycle for CO2 capture
International Nuclear Information System (INIS)
Lisbona, Pilar; Martínez, Ana; Romeo, Luis M.
2013-01-01
Highlights: ► A scaled experimental cold flow model of a dual fluidized bed facility is presented. ► Two MATLAB models are developed for the single CFB and the dual CFB facility. ► Set of experiments are carried out and used to validate the mathematical model. ► Good agreement between model and experimental tests for sCFB. ► Further work required for validating dual CFB operation. -- Abstract: High temperature looping cycles involving solid circulation, such as carbonation–calcination, play an essential role among the CO 2 capture technologies under development. The low cost and high availability of Ca-based sorbents together with the feasibility of integration between these capture systems and existing power plants lead to very competitive potential costs of avoided CO 2 , below 20 €/tonne. Optimal configurations make use of several interconnected fluidized beds. One promising configuration for Ca-based sorbents looping systems relies on the use of two circulating beds (carbonator and calciner) and two bubbling beds acting as non-mechanical valves. Fluidized beds are well characterized when operating independently since they are extensively used in industrial applications, power and chemical plants. However, the operation when two or more fluidized beds exchange solid material through non-mechanical valves is still uncertain because of the more complex pressure balance of the system. Theoretical studies based on thermo-chemical simulations and experimental studies show that minimum CO 2 capture cost is attained with large solid circulation flow between reactors. The challenge is to reach the required particle circulation in a system with a complex configuration and be able to control it. Solid internal recirculation in any of these fluidized beds would provide flexibility in its control but it will also make harder the characterization of the whole system. The aim of this work is to analyse the hydrodynamics of the system and to generate a
International Nuclear Information System (INIS)
Kao, Jim; Flicker, Dawn; Ide, Kayo; Ghil, Michael
2006-01-01
This paper builds upon our recent data assimilation work with the extended Kalman filter (EKF) method [J. Kao, D. Flicker, R. Henninger, S. Frey, M. Ghil, K. Ide, Data assimilation with an extended Kalman filter for an impact-produced shock-wave study, J. Comp. Phys. 196 (2004) 705-723.]. The purpose is to test the capability of EKF in optimizing a model's physical parameters. The problem is to simulate the evolution of a shock produced through a high-speed flyer plate. In the earlier work, we have showed that the EKF allows one to estimate the evolving state of the shock wave from a single pressure measurement, assuming that all model parameters are known. In the present paper, we show that imperfectly known model parameters can also be estimated accordingly, along with the evolving model state, from the same single measurement. The model parameter optimization using the EKF can be achieved through a simple modification of the original EKF formalism by including the model parameters into an augmented state variable vector. While the regular state variables are governed by both deterministic and stochastic forcing mechanisms, the parameters are only subject to the latter. The optimally estimated model parameters are thus obtained through a unified assimilation operation. We show that improving the accuracy of the model parameters also improves the state estimate. The time variation of the optimized model parameters results from blending the data and the corresponding values generated from the model and lies within a small range, of less than 2%, from the parameter values of the original model. The solution computed with the optimized parameters performs considerably better and has a smaller total variance than its counterpart using the original time-constant parameters. These results indicate that the model parameters play a dominant role in the performance of the shock-wave hydrodynamic code at hand
International Nuclear Information System (INIS)
Paisant, Jean-Francois
2014-01-01
Industrial reprocessing of spent fuel is based on chemical separation processes by liquid-liquid extraction into pulsed column. The current context of sustainable development and acceptance of nuclear energy drive the industry to improve the efficiency of this process. Pulsed column efficiency is bound to the amount of available exchange surface, which depends on the geometrical parameters of the column and the operating conditions. A better design would improve the efficiency. In this context, the work presented in this manuscript revolves around physical and numerical modelling of the hydrodynamics of the emulsion coupled with the evolution of the interfacial area, as well as an experimental characterization of the quantities which describe the emulsion. The emulsion is modelled based on the work of D. LHUILLIER. It is an Eulerian approach which describes each phase as a continuous medium as well as the interface which is thought as a third phase moving continuously in the flow field. This thesis contributes to describe of the hydrodynamics of dispersed and continuous phases, in order to determine the slip velocity needed for the design. The written transport equation for interfacial area is based on the thesis of T. RANDRIAMANANTENA. The simulation of this physical model was performed using the method of finite elements (FEM) and implementation was carried out under the software CAST3M. The numerical simulation have shown their abilities to correctly reproduce the expected physical behaviour, in particular, they allow to obtain the slip velocity which is essential to the scale up. In a first experimental approach, the single phase flow has been studied in a pulsed column using particle image velocimetry (PIV), for different amplitude and frequency parameters. A method of synchronization between the recording and the pulsation cycle was used in order to achieve this study. The average behavior, for different regimes of pulsation, has been studied by this way. In
Examining the utility of satellite-based wind sheltering estimates for lake hydrodynamic modeling
Van Den Hoek, Jamon; Read, Jordan S.; Winslow, Luke A.; Montesano, Paul; Markfort, Corey D.
2015-01-01
Satellite-based measurements of vegetation canopy structure have been in common use for the last decade but have never been used to estimate canopy's impact on wind sheltering of individual lakes. Wind sheltering is caused by slower winds in the wake of topography and shoreline obstacles (e.g. forest canopy) and influences heat loss and the flux of wind-driven mixing energy into lakes, which control lake temperatures and indirectly structure lake ecosystem processes, including carbon cycling and thermal habitat partitioning. Lakeshore wind sheltering has often been parameterized by lake surface area but such empirical relationships are only based on forested lakeshores and overlook the contributions of local land cover and terrain to wind sheltering. This study is the first to examine the utility of satellite imagery-derived broad-scale estimates of wind sheltering across a diversity of land covers. Using 30 m spatial resolution ASTER GDEM2 elevation data, the mean sheltering height, hs, being the combination of local topographic rise and canopy height above the lake surface, is calculated within 100 m-wide buffers surrounding 76,000 lakes in the U.S. state of Wisconsin. Uncertainty of GDEM2-derived hs was compared to SRTM-, high-resolution G-LiHT lidar-, and ICESat-derived estimates of hs, respective influences of land cover type and buffer width on hsare examined; and the effect of including satellite-based hs on the accuracy of a statewide lake hydrodynamic model was discussed. Though GDEM2 hs uncertainty was comparable to or better than other satellite-based measures of hs, its higher spatial resolution and broader spatial coverage allowed more lakes to be included in modeling efforts. GDEM2 was shown to offer superior utility for estimating hs compared to other satellite-derived data, but was limited by its consistent underestimation of hs, inability to detect within-buffer hs variability, and differing accuracy across land cover types. Nonetheless
Directory of Open Access Journals (Sweden)
Polomčić Dušan M.
2015-01-01
Full Text Available The calibration process of hydrodynamic model is done usually manually by 'testing' with different values of hydrogeological parameters and hydraulic characteristics of the boundary conditions. By using the PEST program, automatic calibration of models has been introduced, and it has proved to significantly reduce the subjective influence of the model creator on results. With the relatively new approach of PEST, i.e. with the introduction of so-called 'pilot points', the concept of homogeneous zones with parameter values of porous media or zones with the given boundary conditions has been outdated. However, the consequence of this kind of automatic calibration is that a significant amount of time is required to perform the calculation. The duration of calibration is measured in hours, sometimes even days. PEST contains two modules for the shortening of that process - Parallel PEST and BeoPEST. The paper presents performed experiments and analysis of different cases of PEST module usage, based on which the reduction in the time required to calibrate the model is done.
Simplified hydrodynamic model of hydrogen-flame propagation in reactor vessels
International Nuclear Information System (INIS)
Baer, M.R.; Ratzel, A.C.
1983-01-01
The model is consistent with the theory of slow combustion in which the gasdynamic field equations are treated in the limit of small Mach numbers. To the lowest order, pressure is spatially uniform. The flame is treated as a density and entropy discontinuity which propagates at prescribed burning velocities, corresponding to laminar or turbulent flames. Radiation cooling of the burned combustion gases and possible preheating of the unburned gases during propagation of the flame is included using a molecular gas-band thermal radiation model. Application of this model has been developed for 1-D variable-area flame propagation. Multidimensional effects induced by hydrodynamics and buoyancy are corrected for. This model of flame propagation reduces to differential equations which describes the temporal variations of vessel pressure, burned volume and gas entropy. The thermodynamic state of the burned gas immediately following the flame is determined using an isobaric Hugoniot relation. At other locations the burned-gas thermodynamic states are determined using a Lagrangian particle tracking method. Results of a computer code using the method are presented. 11 figures
The collision of a strong shock with a gas cloud: a model for Cassiopeia A
International Nuclear Information System (INIS)
Sgro, A.G.
1975-01-01
The result of the collision of the shock with the cloud is a shock traveling around the cloud, a shock transmitted into the cloud, and a shock reflected from the cloud. By equating the cooling time of the posttransmitted shock gas to the time required for the transmitted shock to travel the length of the cloud, a critical cloud density n/subc/ /sup prime/ is defined. For clouds with density greater than n/subc/ /sup prime/, the posttransmitted shock gas cools rapidly and then emits the lines of the lower ionization stages of its constituent elements. The structure of such and its expected appearance to an observer are discussed and compared with the quasi-stationary condensations of Cas A. Conversely, clouds with density less than n/subc//sup prime/ remain hot for several thousand years, and are sources of X-radiation whose temperatures are much less than that of the intercloud gas. After the transmitted shock passes, the cloud pressure is greater than the pressure in the surrounding gas, causing the cloud to expand and the emission to decrease from its value just after the collision. A model in which the soft X-radiation of Cas A is due to a collection of such clouds is discussed. The faint emission patches to the north of Cas A are interpreted as preshocked clouds which will probably become quasi-stationary condensations after being hit by the shock
Topics in Computational Modeling of Shock and Wave Propagation
National Research Council Canada - National Science Library
Gazonas, George A; Main, Joseph A; Laverty, Rich; Su, Dan; Santare, Michael H; Raghupathy, R; Molinari, J. F; Zhou, F
2006-01-01
This report contains reprints of four papers that focus on various aspects of shock and wave propagation in cellular, viscoelastic, microcracked, and fragmented media that appear in the Proceedings...
On terminating Poisson processes in some shock models
Energy Technology Data Exchange (ETDEWEB)
Finkelstein, Maxim, E-mail: FinkelMI@ufs.ac.z [Department of Mathematical Statistics, University of the Free State, Bloemfontein (South Africa); Max Planck Institute for Demographic Research, Rostock (Germany); Marais, Francois, E-mail: fmarais@csc.co [CSC, Cape Town (South Africa)
2010-08-15
A system subject to a point process of shocks is considered. Shocks occur in accordance with the homogeneous Poisson process. Different criteria of system failure (termination) are discussed and the corresponding probabilities of failure (accident)-free performance are derived. The described analytical approach is based on deriving integral equations for each setting and solving these equations through the Laplace transform. Some approximations are analyzed and further generalizations and applications are discussed.
On terminating Poisson processes in some shock models
International Nuclear Information System (INIS)
Finkelstein, Maxim; Marais, Francois
2010-01-01
A system subject to a point process of shocks is considered. Shocks occur in accordance with the homogeneous Poisson process. Different criteria of system failure (termination) are discussed and the corresponding probabilities of failure (accident)-free performance are derived. The described analytical approach is based on deriving integral equations for each setting and solving these equations through the Laplace transform. Some approximations are analyzed and further generalizations and applications are discussed.
Directory of Open Access Journals (Sweden)
Bondarenko V.I.
2015-03-01
Full Text Available The generic mathematical model and computational algorithm considering hydrodynamics, heat and mass transfer processes during casting and forming steel ingots and castings are offered. Usage domains for turbulent, convective and non-convective models are determined depending on ingot geometry and thermal overheating of the poured melt. The expert system is developed, enabling to choose a mathematical model depending on the physical statement of a problem.
Audebert, M; Oxarango, L; Duquennoi, C; Touze-Foltz, N; Forquet, N; Clément, R
2016-09-01
Leachate recirculation is a key process in the operation of municipal solid waste landfills as bioreactors. To ensure optimal water content distribution, bioreactor operators need tools to design leachate injection systems. Prediction of leachate flow by subsurface flow modelling could provide useful information for the design of such systems. However, hydrodynamic models require additional data to constrain them and to assess hydrodynamic parameters. Electrical resistivity tomography (ERT) is a suitable method to study leachate infiltration at the landfill scale. It can provide spatially distributed information which is useful for constraining hydrodynamic models. However, this geophysical method does not allow ERT users to directly measure water content in waste. The MICS (multiple inversions and clustering strategy) methodology was proposed to delineate the infiltration area precisely during time-lapse ERT survey in order to avoid the use of empirical petrophysical relationships, which are not adapted to a heterogeneous medium such as waste. The infiltration shapes and hydrodynamic information extracted with MICS were used to constrain hydrodynamic models in assessing parameters. The constraint methodology developed in this paper was tested on two hydrodynamic models: an equilibrium model where, flow within the waste medium is estimated using a single continuum approach and a non-equilibrium model where flow is estimated using a dual continuum approach. The latter represents leachate flows into fractures. Finally, this methodology provides insight to identify the advantages and limitations of hydrodynamic models. Furthermore, we suggest an explanation for the large volume detected by MICS when a small volume of leachate is injected. Copyright © 2016 Elsevier Ltd. All rights reserved.
Modeling of ion acceleration through drift and diffusion at interplanetary shocks
Decker, R. B.; Vlahos, L.
1986-01-01
A test particle simulation designed to model ion acceleration through drift and diffusion at interplanetary shocks is described. The technique consists of integrating along exact particle orbits in a system where the angle between the shock normal and mean upstream magnetic field, the level of magnetic fluctuations, and the energy of injected particles can assume a range of values. The technique makes it possible to study time-dependent shock acceleration under conditions not amenable to analytical techniques. To illustrate the capability of the numerical model, proton acceleration was considered under conditions appropriate for interplanetary shocks at 1 AU, including large-amplitude transverse magnetic fluctuations derived from power spectra of both ambient and shock-associated MHD waves.
A 30m resolution hydrodynamic model of the entire conterminous United States.
Bates, P. D.; Neal, J. C.; Smith, A.; Sampson, C.; Johnson, K.; Wing, O.
2016-12-01
In this paper we describe the development and validation of a 30m resolution hydrodynamic model covering the entire conterminous United States. The model can be used to simulate inundation and water depths resulting from either return period flows (so equivalent to FEMA Flood Insurance Rate Maps), hindcasts of historic events or forecasts of future river flow from a rainfall-runoff or land surface model. As topographic data the model uses the U.S. Geological Survey National Elevation Dataset or NED, and return period flows are generated using a regional flood frequency analysis methodology (Smith et al., 2015. Worldwide flood frequency estimation. Water Resources Research, 51, 539-553). Flood defences nationwide are represented using data from the US Army Corps of Engineers. Using these data flows are simulated using an explicit and highly efficient finite difference solution of the local inertial form of the Shallow Water equations identical to that implemented in the LISFLOOD-FP model. Even with this efficient numerical solution a simulation at this resolution over a whole continent is a huge undertaking, and a variety of High Performance Computing technologies therefore need to be employed to make these simulations possible. The size of the output datasets is also challenging, and to solve this we use the GIS and graphical display functions of Google Earth Engine to facilitate easy visualisation and interrogation of the results. The model is validated against the return period flood extents contained in FEMA Flood Insurance Rate Maps and real flood event data from the Texas 2015 flood event which was hindcast using the model. Finally, we present an application of the model to the Upper Mississippi river basin where simulations both with and without flood defences are used to determine floodplain areas benefitting from protection in order to quantify the benefits of flood defence spending.
Thermo-hydrodynamic and inductive modelling of a glass melt elaborated in cold inductive crucible
International Nuclear Information System (INIS)
Sauvage, E.
2009-11-01
Within the context of a search for a new vitrification process for nuclear wastes with a replacement of the presently used metallic pot by an inductive cold crucible, this research thesis deals with the numerical modelling of this technology. After having recalled the interest of nuclear waste vitrification, this report presents the new process based on the use of a cold crucible, describing principles and objectives of this method, and the characteristic physical phenomena associated with the flow and the thermodynamics of the glassy melt in such a crucible. It also recalls and comments the existing works on modelling. The main objective of this research is then to demonstrate the feasibility of 3D thermo-hydraulic and inductive simulations. He describes and analyses the glass physical properties (electrical properties, viscosity, thermal properties), the electromagnetic, hydrodynamic and thermal phenomena. He presents in detail the bubbling mixing modelling, reports 3D induction and fluid mechanical coupling calculations, and specific thermal investigations (radiating transfers, thermal limit conditions)
Floodplain simulation for Musi River using integrated 1D/2D hydrodynamic model
Directory of Open Access Journals (Sweden)
Al Amin Muhammad B.
2017-01-01
Full Text Available This paper presents the simulation of floodplain at Musi River using integrated 1D and 2D hydrodynamic model. The 1D flow simulation was applied for the river channel with flow hydrograph as upstream boundary condition. The result of 1D flow simulation was integrated into 2D flow simulation in order to know the area and characteristics of flood inundation. The input data of digital terrain model which was used in this research had grid resolution of 10m×10m, but for 2D simulation the resolution was with grid resolution 50 m × 50 m so as to limit simulation time since the model size was big enough. The result of the simulation showed that the inundated area surrounding Musi River is about 107.44 km2 with maximum flood depth is 3.24 m, water surface velocity ranges from 0.00 to 0.83 m/s. Most of floodplain areas varied from middle to high flood hazard level, and only few areas had very high level of flood hazard especially on river side. The structural flood control measurement to be recommended to Palembang is to construct flood dike and flood gate. The non structural measurement one is to improve watershed management and socialization of flood awareness.
Flood Risk Zoning by Using 2D Hydrodynamic Modeling: A Case Study in Jinan City
Directory of Open Access Journals (Sweden)
Tao Cheng
2017-01-01
Full Text Available Climate change and rapid urbanization have aggravated the rainstorm flood in Jinan City during the past decades. Jinan City is higher in the south and lower in the north with a steep slope inclined from the south to the north. This results in high-velocity overland flow and deep waterlogging, which poses a tremendous threat to pedestrians and vehicles. Therefore, it is vital to investigate the rainstorm flood and further perform flood risk zoning. This study is carried out in the “Sponge City Construction” pilot area of Jinan City, where the InfoWorks ICM 2D hydrodynamic model is utilized for simulating historical and designed rainfall events. The model is validated with observations, and the causes for errors are analyzed. The simulated water depth and flow velocity are recorded for flood risk zoning. The result shows that the InfoWorks ICM 2D model performed well. The flood risk zoning result shows that rainfalls with larger recurrence intervals generate larger areas of moderate to extreme risk. Meanwhile, the zoning results for the two historical rainfalls show that flood with a higher maximum hourly rainfall intensity is more serious. This study will provide scientific support for the flood control and disaster reduction in Jinan City.
Global SWOT Data Assimilation of River Hydrodynamic Model; the Twin Simulation Test of CaMa-Flood
Ikeshima, D.; Yamazaki, D.; Kanae, S.
2016-12-01
CaMa-Flood is a global scale model for simulating hydrodynamics in large scale rivers. It can simulate river hydrodynamics such as river discharge, flooded area, water depth and so on by inputting water runoff derived from land surface model. Recently many improvements at parameters or terrestrial data are under process to enhance the reproducibility of true natural phenomena. However, there are still some errors between nature and simulated result due to uncertainties in each model. SWOT (Surface water and Ocean Topography) is a satellite, which is going to be launched in 2021, can measure open water surface elevation. SWOT observed data can be used to calibrate hydrodynamics model at river flow forecasting and is expected to improve model's accuracy. Combining observation data into model to calibrate is called data assimilation. In this research, we developed data-assimilated river flow simulation system in global scale, using CaMa-Flood as river hydrodynamics model and simulated SWOT as observation data. Generally at data assimilation, calibrating "model value" with "observation value" makes "assimilated value". However, the observed data of SWOT satellite will not be available until its launch in 2021. Instead, we simulated the SWOT observed data using CaMa-Flood. Putting "pure input" into CaMa-Flood produce "true water storage". Extracting actual daily swath of SWOT from "true water storage" made simulated observation. For "model value", we made "disturbed water storage" by putting "noise disturbed input" to CaMa-Flood. Since both "model value" and "observation value" are made by same model, we named this twin simulation. At twin simulation, simulated observation of "true water storage" is combined with "disturbed water storage" to make "assimilated value". As the data assimilation method, we used ensemble Kalman filter. If "assimilated value" is closer to "true water storage" than "disturbed water storage", the data assimilation can be marked effective. Also
Counterpropagating Radiative Shock Experiments on the Orion Laser.
Suzuki-Vidal, F; Clayson, T; Stehlé, C; Swadling, G F; Foster, J M; Skidmore, J; Graham, P; Burdiak, G C; Lebedev, S V; Chaulagain, U; Singh, R L; Gumbrell, E T; Patankar, S; Spindloe, C; Larour, J; Kozlova, M; Rodriguez, R; Gil, J M; Espinosa, G; Velarde, P; Danson, C
2017-08-04
We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.
Study of proton-nucleus collisions at high energies based on the hydrodynamical model
International Nuclear Information System (INIS)
Masuda, N.; Weiner, R.M.
1978-01-01
We study proton-nucleus collisions at high energies using the one-dimensional hydrodynamical model of Landau with special emphasis on the effect of the size of the target nucleus and of the magnitude of velocity of sound of excited hadronic matter. We convert a collision problem of a proton and a nucleus with a spherical shape into that of a proton and a one-dimensional nuclear tunnel whose length is determined from the average impact parameter. By extending the methods developed by Milekhin and Emelyanov, we obtain the solutions of the hydrodynamical equations of proton-nucleus collisions for arbitrary target tunnel length and arbitrary velocity of sound. The connection between these solutions and observable physical quantities is established as in the work of Cooper, Frye, and Schonberg. Extensive numerical analyses are made at E/sub lab/ = 200 GeV and for the velocity of sound u = 1/√3 of a relativistic ideal Bose gas and u = 1/(7.5)/sup 1/2/ of an interacting Bose gas. In order to compare proton-nucleus collisions with proton-proton collisions, all the analyses are made in the equal-velocity frame. We find the following results. (1) In comparing the number of secondary particles produced in p-A collisions N/sub p/A with those in p-p collisions N/sub p/p, while most of the excess of N/sub p/A over N/sub p/p is concentrated in the backward rapidity region, there exists also an increase of N/sub p/A with A in the forward rapidity region. This result is at variance with the predictions of the energy-flux-cascade model and of the coherent-production model. (2) The excess energies are contained exclusively in the backward region. We also find evidence for new phenomena in proton-nucleus collisions. (3) The existence of an asymmetry of average energies of secondary particles between forward and backward regions, in particular, >> for larger nuclear targets. Thus, energetic particles are predominantly produced in the backward region
Shock loading and reactive flow modeling studies of void induced AP/AL/HTPB propellant
Miller, P. J.; Lindfors, A. J.
1998-07-01
The unreactive Hugoniot of a class 1.3 propellant has been investigated by shock compression experiments. The results are analyzed in terms of an ignition and growth reactive flow model using the DYNA2D hydrocode. The calculated shock ignition parameters of the model show a linear dependence on measured void volume which appears to reproduce the observed gauge records well. Shock waves were generated by impact in a 75 mm single stage powder gun. Manganin and PVDF pressure gauges provided pressure-time histories to 140 kbar. The propellants were of similar formulation differing only in AP particle size and the addition of a burn rate modifer (Fe2O3) from that of previous investigations. Results show neglible effect of AP particle size on shock response in contrast to the addition of Fe2O3 which appears to `stiffen' the unreactive Hugoniot and enhances significantly the reactive rates under shock. The unreactive Hugoniot, within experimental error, compares favorably to the solid AP Hugoniot. Shock experiments were performed on propellant samples strained to induce insitu voids. The material state was quantified by uniaxial tension dialatometry. The experimental records show a direct correlation between void volume (0 to 1.7%) and chemical reactivity behind the shock front. These results are discussed in terms of `hot spot' ignition resulting from the shock collapse of the voids.
Thermal hydrodynamic modeling and simulation of hot-gas duct for next-generation nuclear reactor
Energy Technology Data Exchange (ETDEWEB)
Lee, Injun [School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Hong, Sungdeok; Kim, Chansoo [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Bai, Cheolho; Hong, Sungyull [School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Shim, Jaesool, E-mail: jshim@ynu.ac.kr [School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of)
2016-12-15
Highlights: • Thermal hydrodynamic nonlinear model is presented to examine a hot gas duct (HGD) used in a fourth-generation nuclear power reactor. • Experiments and simulation were compared to validate the nonlinear porous model. • Natural convection and radiation are considered to study the effect on the surface temperature of the HGD. • Local Nusselt number is obtained for the optimum design of a possible next-generation HGD. - Abstract: A very high-temperature gas-cooled reactor (VHTR) is a fourth-generation nuclear power reactor that requires an intermediate loop that consists of a hot-gas duct (HGD), an intermediate heat exchanger (IHX), and a process heat exchanger for massive hydrogen production. In this study, a mathematical model and simulation were developed for the HGD in a small-scale nitrogen gas loop that was designed and manufactured by the Korea Atomic Energy Research Institute. These were used to investigate the effect of various important factors on the surface of the HGD. In the modeling, a porous model was considered for a Kaowool insulator inside the HGD. The natural convection and radiation are included in the model. For validation, the modeled external surface temperatures are compared with experimental results obtained while changing the inlet temperatures of the nitrogen working fluid. The simulation results show very good agreement with the experiments. The external surface temperatures of the HGD are obtained with respect to the porosity of insulator, emissivity of radiation, and pressure of the working fluid. The local Nusselt number is also obtained for the optimum design of a possible next-generation HGD.
Fe-Modeling Of Starved Hydrodynamic Lubrication With Free Surface Effects
DEFF Research Database (Denmark)
Poulios, Konstantinos; Vølund, Anders; Klit, Peder
2017-01-01
This work concerns a new finite-element formulation for solving hydrody-namic lubrication problems that include partially flooded regions, where the lubricant film behavior is governed by free surface flow....
Efficient Calculation of Dewatered and Entrapped Areas Using Hydrodynamic Modeling and GIS
International Nuclear Information System (INIS)
Richmond, Marshall C.; Perkins, William A.
2009-01-01
River waters downstream of a hydroelectric project are often subject to rapidly changing discharge. Abrupt decreases in discharge can quickly dewater and expose some areas and isolate other areas from the main river channel, potentially stranding or entrapping fish, which often results in mortality. A methodology is described to estimate the areas dewatered or entrapped by a specific reduction in upstream discharge. A one-dimensional hydrodynamic model was used to simulate steady flows. Using flow simulation results from the model and a geographic information system (GIS), estimates of dewatered and entrapped areas were made for a wide discharge range. The methodology was applied to the Hanford Reach of the Columbia River in central Washington State. Results showed that a 280 m 3 /s discharge reduction affected the most area at discharges less than 3400 m 3 /s. At flows above 3400 m 3 /s, the affected area by a 280 m 3 /s discharge reduction (about 25 ha) was relatively constant. A 280 m 3 /s discharge reduction at lower flows affected about twice as much area. The methodology and resulting area estimates were, at the time of writing, being used to identify discharge regimes, and associated water surface elevations, that might be expected to minimize adverse impacts on juvenile fall chinook salmon (Oncorhynchus tshawytscha) that rear in the shallow near-shore areas in the Hanford Reach
Hydrodynamic and Sediment Transport Modelling of Suralaya Coastal Area, Cilegon, Indonesia
Fattah, A. H.; Suntoyo; Damerianne, H. A.; Wahyudi
2018-03-01
The coastal zone of Suralaya is located in the district Pulomerak, Cilegon City, Province Banten. This region is a part of the Sunda Strait region that is very important area to support the ongoing activities such as, industries, power plant, ports, and tourism. However, those various activities will certainly give effect to the surrounding environment. To determine the environmental conditions of Suralaya Coast, it is necessary to study the hydrodynamics analysis and sediment transport modelling including the analysis of currents patterns. Tidal elevation observation was conducted for 15 days used to validate the water elevation simulation results, in which a good agreement between the observed data and the model result was obtained with the error value of 1.6%. The dominant current direction is from northeast in west season, while in the east season predominant current direction is from northwest with a speed average current 12,44 cm/s. The dominant wave direction is from the west. The average temperature is at 27°C and the bottom sediment dominant form is fine sand.
Hydrodynamic Modeling Analysis for Leque Island and zis a ba Restoration Feasibility Study
Energy Technology Data Exchange (ETDEWEB)
Whiting, Jonathan M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Khangaonkar, Tarang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2015-01-31
Ducks Unlimited, Inc. in collaboration with Washington State Department of Fish and Wildlife (WDFW), and Stillaguamish Tribe of Indians have proposed the restoration of Leque Island and zis a ba (formerly Matterand) sites near the mouth of Old Stillaguamish River Channel in Port Susan Bay, Washington. The Leque Island site, which is owned by WDFW, consists of nearly 253 acres of land south of Highway 532 that is currently behind a perimeter dike. The 90-acres zis a ba site, also shielded by dikes along the shoreline, is located just upstream of Leque Island and is owned by Stillaguamish Tribes. The proposed actions consider the removal or modification of perimeter dikes at both locations to allow estuarine functions to be restored. The overall objective of the proposed projects is to remove the dike barriers to 1) provide connectivity and access between the tidal river channel and the restoration site for use by juvenile migrating salmon and 2) create a self-sustaining tidal marsh habitat. Ducks Unlimited engaged Pacific Northwest National Laboratory (PNNL) to develop a three-dimensional hydrodynamic model of the Port Susan Bay, Skagit Bay, and the interconnecting Leque Island region for use in support of the feasibility assessment for the Leque Island and zis a ba restoration projects. The objective of this modeling-based feasibility assessment is to evaluate the performance of proposed restoration actions in terms of achieving habitat goals while assessing the potential hydraulic and sediment transport impacts to the site and surrounding parcels of land.
Directory of Open Access Journals (Sweden)
Wen-Tao Su
2014-03-01
Full Text Available This paper presents an experimental investigation of flow phenomena related to the characteristic frequencies of pressure fluctuation in Francis hydroturbine models. The experiments were carried out on two test rigs with two model runners having hydraulic similarities. Flow field around the guide vanes was measured with a particle image velocimetry (PIV on the first PIV test rig. Flow structures at the inlet region of runner and in draft tube at different operating conditions were visualized on another hydrodynamic test rig. Analyses of dominant frequency of unsteady hydraulic behaviors in the tested hydroturbines were performed. It was observed that the main frequency of flow over the guide vanes and the dominant frequency of channel vortex equal the blade passing frequency; the dominant frequency of flow separation at the suction side of blade inlet equals the vane passing frequency; the vortex rope in the draft tube displays a low-frequency nature. The flow instabilities and fluctuations directly influence the running of hydroturbine, thus these experimental results could provide important evidence for the stability study of a real hydroturbine.
3D Realistic Radiative Hydrodynamic Modeling of a Moderate-Mass Star: Effects of Rotation
Kitiashvili, Irina; Kosovichev, Alexander G.; Mansour, Nagi N.; Wray, Alan A.
2018-01-01
Recent progress in stellar observations opens new perspectives in understanding stellar evolution and structure. However, complex interactions in the turbulent radiating plasma together with effects of magnetic fields and rotation make inferences of stellar properties uncertain. The standard 1D mixing-length-based evolutionary models are not able to capture many physical processes of stellar interior dynamics, but they provide an initial approximation of the stellar structure that can be used to initialize 3D time-dependent radiative hydrodynamics simulations, based on first physical principles, that take into account the effects of turbulence, radiation, and others. In this presentation we will show simulation results from a 3D realistic modeling of an F-type main-sequence star with mass 1.47 Msun, in which the computational domain includes the upper layers of the radiation zone, the entire convection zone, and the photosphere. The simulation results provide new insight into the formation and properties of the convective overshoot region, the dynamics of the near-surface, highly turbulent layer, the structure and dynamics of granulation, and the excitation of acoustic and gravity oscillations. We will discuss the thermodynamic structure, oscillations, and effects of rotation on the dynamics of the star across these layers.
Chaotic behavior in a hydrodynamic model of a fluidized bed reactor
International Nuclear Information System (INIS)
Schouten, J.C.; van den Bleek, C.M.
1991-01-01
Recent preliminary experimental studies using time-series analysis have demonstrated that the multi-phase flow in fluidized bed reactors can be characterized as chaotic. In the present paper, it is therefore argued that the chaotic time-dependence of fluidization is a characteristic feature which should be included in scaling rules for fluidized bed reactors. For example, the similarity groups applied in dimensionless fluidized bed scaling should be improved by extending them with functions of the relevant numbers from chaos theory, such as the correlation and embedding dimension or the maximum Lyapunov exponent. This requires that the dependence of these numbers on fluidization parameters must be theoretically and experimentally investigated. The concept of chaos in fluidization also requires that the classical, empirically developed, hydrodynamic models that are applied in fluidized bed scaling are amended to include time-dependence, non-linearity as well as a sufficient level of complexity before they can predict any chaotic behavior. An example is given of chaotic behavior generated in the classical counter-current flow model according to Van Deemter by writing the upwards solids velocity as a harmonic oscillating function of time. A low-dimensional strange attractor is found, embedded in two-dimensional phase space, of which the correlation dimension depends on the solids exchange coefficient
Hill, Craig; Kozarek, Jessica; Sotiropoulos, Fotis; Guala, Michele
2016-02-01
An investigation into the interactions between a model axial-flow hydrokinetic turbine (rotor diameter, dT = 0.15 m) and the complex hydrodynamics and sediment transport processes within a meandering channel was carried out in the Outdoor StreamLab research facility at the University of Minnesota St. Anthony Falls Laboratory. This field-scale meandering stream with bulk flow and sediment discharge control provided a location for high spatiotemporally resolved measurements of bed and water surface elevations around the model turbine. The device was installed within an asymmetric, erodible channel cross section under migrating bed form and fixed outer bank conditions. A comparative analysis between velocity and topographic measurements, with and without the turbine installed, highlights the local and nonlocal features of the turbine-induced scour and deposition patterns. In particular, it shows how the cross-section geometry changes, how the bed form characteristics are altered, and how the mean flow field is distorted both upstream and downstream of the turbine. We further compare and discuss how current energy conversion deployments in meander regions would result in different interactions between the turbine operation and the local and nonlocal bathymetry compared to straight channels.
International Nuclear Information System (INIS)
Colli, A.N.; Bisang, J.M.
2011-01-01
Highlights: · The type of turbulence promoters has a strong influence on the hydrodynamics. · The dispersion model is appropriate for expanded plastic turbulence promoters. · The dispersion model is appropriate for glass beads turbulence promoters. - Abstract: The hydrodynamic behaviour of electrochemical reactors with parallel plate electrodes is experimentally studied using the stimulus-response method either with an empty reactor or with different turbulence promoters. Theoretical results which are in accordance with the analytical and numerical resolution of the dispersion model for a closed system are compared with the classical relationships of the normalized outlet concentration for open systems and the validity range of the equations is discussed. The experimental results were well correlated with the dispersion model using glass beads or expanded plastic meshes as turbulence promoters, which have shown the most advantageous performance. The Peclet number was higher than 63. The dispersion coefficient was found to increase linearly with flow velocity in these cases.
High-order hydrodynamic algorithms for exascale computing
Energy Technology Data Exchange (ETDEWEB)
Morgan, Nathaniel Ray [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-02-05
Hydrodynamic algorithms are at the core of many laboratory missions ranging from simulating ICF implosions to climate modeling. The hydrodynamic algorithms commonly employed at the laboratory and in industry (1) typically lack requisite accuracy for complex multi- material vortical flows and (2) are not well suited for exascale computing due to poor data locality and poor FLOP/memory ratios. Exascale computing requires advances in both computer science and numerical algorithms. We propose to research the second requirement and create a new high-order hydrodynamic algorithm that has superior accuracy, excellent data locality, and excellent FLOP/memory ratios. This proposal will impact a broad range of research areas including numerical theory, discrete mathematics, vorticity evolution, gas dynamics, interface instability evolution, turbulent flows, fluid dynamics and shock driven flows. If successful, the proposed research has the potential to radically transform simulation capabilities and help position the laboratory for computing at the exascale.
A high resolution hydrodynamic 3-D model simulation of the malta shelf area
Directory of Open Access Journals (Sweden)
A. F. Drago
2003-01-01
detail. This modelling effort has initiated the treatment of the open boundary conditions problem in view of the future implementation of shelf-scale real-time ocean forecasting through the sequential nesting of a hierarchy of successively embedded model domains for the downscaling of the hydrodynamics from the coarse grid Ocean General Circulation Model of the whole Mediterranean Sea to finer grids in coastal areas. Key words. Oceanography: general (continental shelf processes; numerical modelling Oceanography: physical (general circulation
A high resolution hydrodynamic 3-D model simulation of the malta shelf area
Directory of Open Access Journals (Sweden)
A. F. Drago
internal dynamics, to be followed in detail. This modelling effort has initiated the treatment of the open boundary conditions problem in view of the future implementation of shelf-scale real-time ocean forecasting through the sequential nesting of a hierarchy of successively embedded model domains for the downscaling of the hydrodynamics from the coarse grid Ocean General Circulation Model of the whole Mediterranean Sea to finer grids in coastal areas.
Key words. Oceanography: general (continental shelf processes; numerical modelling Oceanography: physical (general circulation
The hydrodynamics of Type II supernove
International Nuclear Information System (INIS)
Chevalier, R.A.
1976-01-01
Observations of Type II supernovae indicate the presence of a moderately cool expanding photosphere. This situation can result from an explosion in a star with an extended envelope. The evolutionary phases of an explosion are described. Information on the propagation of the shock wave through the star can be obtained from γ=4/3 blast wave solutions. If the photon mean free path becomes large compared to the length scales of the flow, a thermal wave moves out from the shock wave and a dense shell is formed behind the shock. The arrival of the shock wave at the photosphere is accompanied by ultraviolet and X-ray burst. As the star expands, a rarefaction wave converts internal energy into kinetic energy. Detailed hydrodynamic models have been calculated, assuming an initial radius compatible with stellar evolution and an energy compatible with the observed velocities. The observed values of photospheric radius and temperature near maximum light are reproduced. Features of the models which are consistent with observation are: the ejection of a detached shell; the cooling of the photosphere from 10,000 K to 6000 K in tens of days after maximum visual light; the shape of the light curve around maximum; the decrease in the velocity of the gas at the photosphere in tens of days after maximum; and a photospheric radius of about 10/sup 14/ cm after several hundred days
A New Two-fluid Radiation-hydrodynamical Model for X-Ray Pulsar Accretion Columns
Energy Technology Data Exchange (ETDEWEB)
West, Brent F. [Department of Electrical and Computer Engineering, United States Naval Academy, Annapolis, MD (United States); Wolfram, Kenneth D. [Naval Research Laboratory (retired), Washington, DC (United States); Becker, Peter A., E-mail: bwest@usna.edu, E-mail: kswolfram@gmail.com, E-mail: pbecker@gmu.edu [Department of Physics and Astronomy, George Mason University, Fairfax, VA USA (United States)
2017-02-01
Previous research centered on the hydrodynamics in X-ray pulsar accretion columns has largely focused on the single-fluid model, in which the super-Eddington luminosity inside the column decelerates the flow to rest at the stellar surface. This type of model has been relatively successful in describing the overall properties of the accretion flows, but it does not account for the possible dynamical effect of the gas pressure. On the other hand, the most successful radiative transport models for pulsars generally do not include a rigorous treatment of the dynamical structure of the column, instead assuming an ad hoc velocity profile. In this paper, we explore the structure of X-ray pulsar accretion columns using a new, self-consistent, “two-fluid” model, which incorporates the dynamical effect of the gas and radiation pressures, the dipole variation of the magnetic field, the thermodynamic effect of all of the relevant coupling and cooling processes, and a rigorous set of physical boundary conditions. The model has six free parameters, which we vary in order to approximately fit the phase-averaged spectra in Her X-1, Cen X-3, and LMC X-4. In this paper, we focus on the dynamical results, which shed new light on the surface magnetic field strength, the inclination of the magnetic field axis relative to the rotation axis, the relative importance of gas and radiation pressures, and the radial variation of the ion, electron, and inverse-Compton temperatures. The results obtained for the X-ray spectra are presented in a separate paper.
Ganju, Neil K.; Sherwood, Christopher R.
2010-01-01
A variety of algorithms are available for parameterizing the hydrodynamic bottom roughness associated with grain size, saltation, bedforms, and wave–current interaction in coastal ocean models. These parameterizations give rise to spatially and temporally variable bottom-drag coefficients that ostensibly provide better representations of physical processes than uniform and constant coefficients. However, few studies have been performed to determine whether improved representation of these variable bottom roughness components translates into measurable improvements in model skill. We test the hypothesis that improved representation of variable bottom roughness improves performance with respect to near-bed circulation, bottom stresses, or turbulence dissipation. The inner shelf south of Martha’s Vineyard, Massachusetts, is the site of sorted grain-size features which exhibit sharp alongshore variations in grain size and ripple geometry over gentle bathymetric relief; this area provides a suitable testing ground for roughness parameterizations. We first establish the skill of a nested regional model for currents, waves, stresses, and turbulent quantities using a uniform and constant roughness; we then gauge model skill with various parameterization of roughness, which account for the influence of the wave-boundary layer, grain size, saltation, and rippled bedforms. We find that commonly used representations of ripple-induced roughness, when combined with a wave–current interaction routine, do not significantly improve skill for circulation, and significantly decrease skill with respect to stresses and turbulence dissipation. Ripple orientation with respect to dominant currents and ripple shape may be responsible for complicating a straightforward estimate of the roughness contribution from ripples. In addition, sediment-induced stratification may be responsible for lower stresses than predicted by the wave–current interaction model.
An empirical model of the Earth's bow shock based on an artificial neural network
Pallocchia, Giuseppe; Ambrosino, Danila; Trenchi, Lorenzo
2014-05-01
All of the past empirical models of the Earth's bow shock shape were obtained by best-fitting some given surfaces to sets of observed crossings. However, the issue of bow shock modeling can be addressed by means of artificial neural networks (ANN) as well. In this regard, here it is presented a perceptron, a simple feedforward network, which computes the bow shock distance along a given direction using the two angular coordinates of that direction, the bow shock predicted distance RF79 (provided by Formisano's model (F79)) and the upstream alfvénic Mach number Ma. After a brief description of the ANN architecture and training method, we discuss the results of the statistical comparison, performed over a test set of 1140 IMP8 crossings, between the prediction accuracies of ANN and F79 models.
Improved bow shock models for Herbig-Haro objects - application to HH 2A-prime
International Nuclear Information System (INIS)
Raymond, J.C.; Hartmann, L.; Hartigan, P.
1988-01-01
An improved version of the bow shock theory previously applied to Herbig-Haro objects is presented. The modifications provide a more accurate calculation of the ionization state of material entering the bow shock. The revised preionization does not drastically affect the emission-line predictions for a 200 km/s bow shock model, though the effects will be more severe for slower shock velocities. The line profiles of the new models resemble the observed profiles somewhat more closely, and the relative emission-line intensities typically differ by 30 percent from those predicted by the older models. The models agree well with new IUE spectra and existing optical data for HH 2A-prime. 32 references
Directory of Open Access Journals (Sweden)
J. M. Hoch
2017-10-01
Full Text Available We here present GLOFRIM, a globally applicable computational framework for integrated hydrological–hydrodynamic modelling. GLOFRIM facilitates spatially explicit coupling of hydrodynamic and hydrologic models and caters for an ensemble of models to be coupled. It currently encompasses the global hydrological model PCR-GLOBWB as well as the hydrodynamic models Delft3D Flexible Mesh (DFM; solving the full shallow-water equations and allowing for spatially flexible meshing and LISFLOOD-FP (LFP; solving the local inertia equations and running on regular grids. The main advantages of the framework are its open and free access, its global applicability, its versatility, and its extensibility with other hydrological or hydrodynamic models. Before applying GLOFRIM to an actual test case, we benchmarked both DFM and LFP for a synthetic test case. Results show that for sub-critical flow conditions, discharge response to the same input signal is near-identical for both models, which agrees with previous studies. We subsequently applied the framework to the Amazon River basin to not only test the framework thoroughly, but also to perform a first-ever benchmark of flexible and regular grids on a large-scale. Both DFM and LFP produce comparable results in terms of simulated discharge with LFP exhibiting slightly higher accuracy as expressed by a Kling–Gupta efficiency of 0.82 compared to 0.76 for DFM. However, benchmarking inundation extent between DFM and LFP over the entire study area, a critical success index of 0.46 was obtained, indicating that the models disagree as often as they agree. Differences between models in both simulated discharge and inundation extent are to a large extent attributable to the gridding techniques employed. In fact, the results show that both the numerical scheme of the inundation model and the gridding technique can contribute to deviations in simulated inundation extent as we control for model forcing and boundary
Qian, Tiezheng
2009-10-29
This paper starts with an introduction to the Onsager principle of minimum energy dissipation which governs the optimal paths of deviation and restoration to equilibrium. Then there is a review of the variational approach to moving contact line hydrodynamics. To demonstrate the validity of our continuum hydrodynamic model, numerical results from model calculations and molecular dynamics simulations are presented for immiscible Couette and Poiseuille flows past homogeneous solid surfaces, with remarkable overall agreement. Our continuum model is also used to study the contact line motion on surfaces patterned with stripes of different contact angles (i.e. surfaces of varying wettability). Continuum calculations predict the stick-slip motion for contact lines moving along these patterned surfaces, in quantitative agreement with molecular dynamics simulation results. This periodic motion is tunable through pattern period (geometry) and contrast in wetting property (chemistry). The consequence of stick-slip contact line motion on energy dissipation is discussed. © 2009 IOP Publishing Ltd.
Directory of Open Access Journals (Sweden)
A. Hartmann
2013-08-01
Full Text Available More than 30% of Europe's land surface is made up of karst exposures. In some countries, water from karst aquifers constitutes almost half of the drinking water supply. Hydrological simulation models can predict the large-scale impact of future environmental change on hydrological variables. However, the information needed to obtain model parameters is not available everywhere and regionalisation methods have to be applied. The responsive behaviour of hydrological systems can be quantified by individual metrics, so-called system signatures. This study explores their value for distinguishing the dominant processes and properties of five different karst systems in Europe and the Middle East. By defining ten system signatures derived from hydrodynamic and hydrochemical observations, a process-based karst model is applied to the five karst systems. In a stepwise model evaluation strategy, optimum parameters and their sensitivity are identified using automatic calibration and global variance-based sensitivity analysis. System signatures and sensitive parameters serve as proxies for dominant processes, and optimised parameters are used to determine system properties. By sensitivity analysis, the set of system signatures was able to distinguish the karst systems from one another by providing separate information about dominant soil, epikarst, and fast and slow groundwater flow processes. Comparing sensitive parameters to the system signatures revealed that annual discharge can serve as a proxy for the recharge area, that the slopes of the high flow parts of the flow duration curves correlate with the fast flow storage constant, and that the dampening of the isotopic signal of the rain as well as the medium flow parts of the flow duration curves have a non-linear relation to the distribution of groundwater storage constants that represent the variability of groundwater flow dynamics. Our approach enabled us to identify dominant processes of the
Eregno, Fasil Ejigu; Tryland, Ingun; Tjomsland, Torulv; Kempa, Magdalena; Heistad, Arve
2018-06-01
Microbial contamination of recreational beaches is often at its worst after heavy rainfall events due to storm floods that carry fecal matter and other pollutants from the watershed. Similarly, overflows of untreated sewage from combined sewerage systems may discharge directly into coastal water or via rivers and streams. In order to understand the effect of rainfall events, wind-directions and tides on the recreational water quality, GEMSS, an integrated 3D hydrodynamic model was applied to assess the spreading of Escherichia coli (E. coli) at the Sandvika beaches, located in the Oslo fjord. The model was also used to theoretically investigate the effect of discharges from septic tanks from boats on the water quality at local beaches. The model make use of microbial decay rate as the main input representing the survival of microbial pathogens in the ocean, which vary widely depending on the type of pathogen and environmental stress. The predicted beach water quality was validated against observed data after a heavy rainfall event using Nash-Sutcliffe coefficient (E) and the overall result indicated that the model performed quite well and the simulation was in - good agreement with the observed E. coli concentrations for all beaches. The result of this study indicated that: 1) the bathing water quality was poor according to the EU bathing water directive up to two days after the heavy rainfall event depending on the location of the beach site. 2) The discharge from a boat at 300-meter distance to the beaches slightly increased the E. coli levels at the beaches. 3) The spreading of microbial pathogens from its source to the different beaches depended on the wind speed and the wind direction.
Modelling of the impact of biofouling on hydrodynamics downstream of a tidal turbine
Bennis, A. C.; Rivier, A.; Dauvin, J. C.
2016-02-01
Biological organisms, like barnacles, mussels or bryozoans, colonize rapidly an immersed surface and could form a thickness until several centimeters on it. This biofouling could modify hydrodynamics around tidal turbine by increasing drag and hence resistance and could be detrimental to the performance of turbine (e.g. Orme et al., 2001; Khor and Xiao, 2011). Our work focuses on modifications of vortices downstream of a tidal turbine due to biofouling using CFD. Fixed biological organisms are solved explicitly by the model and are considered by modifying the blade profile. Firstly an airfoil colonized by barnacles is modelled for various fouling height and spacing and results are compared to experimental and simulated data (Orme et al., 2001; Khor and Xiao, 2011) in order to assess the capacity of the model to reproduce the flow around a blade with biofouling. Then a Darrieus vertical axis tidal turbine is modelled using a dynamic mesh. Configuration with smooth clean blades is assessed by comparison with experiments and simulations made by Roa (2011) and Bossard (2012). Biological organisms with various heights, spacing and shapes are fixed on blades and wakes downstream of clean and colonized tidal turbine are compared. Vorticity fields around the tidal turbine are clearly modified when blades are colonized. Samples will be taken from location where farms are planned to be built (Alderney Race/Raz Blanchard) to characterize more precisely the characteristics of species which are liable to fix on tidal turbine.Reference:Bossard (2012). Doctoral dissertation, Université de Grenoble.Khor & Xiao. (2011). Ocean Eng, 38(10), 1065-1079. Orme et al. (2001). Marine Renewable Energy Conference, Newcastle.Roa (2011).Doctoral dissertation, Université de Grenoble.
This technical report describes the new one-dimensional (1D) hydrodynamic and sediment transport model EFDC1D. This model that can be applied to stream networks. The model code and two sample data sets are included on the distribution CD. EFDC1D can simulate bi-directional unstea...
Bioeffects on an In Vitro Model by Small-Scale Explosives and Shock Wave Overpressure Impacts
2017-11-01
Many TBIs are associated with blast from improvised explosive devices.2–4 Explosions are physical, chemical , or nuclear reactions involving a rapid...ARL-TR-8210 ● NOV 2017 US Army Research Laboratory Bioeffects on an In Vitro Model by Small-Scale Explosives and Shock Wave...Research Laboratory Bioeffects on an In Vitro Model by Small-Scale Explosives and Shock Wave Overpressure Impacts by Nicole E Zander, Thuvan
A new, accurate, global hydrography data for remote sensing and modelling of river hydrodynamics
Yamazaki, D.
2017-12-01
A high-resolution hydrography data is an important baseline data for remote sensing and modelling of river hydrodynamics, given the spatial scale of river network is much smaller than that of land hydrology or atmosphere/ocean circulations. For about 10 years, HydroSHEDS, developed based on the SRTM3 DEM, has been the only available global-scale hydrography data. However, the data availability at the time of HydroSHEDS development limited the quality of the represented river networks. Here, we developed a new global hydrography data using latest geodata such as the multi-error-removed elevation data (MERIT DEM), Landsat-based global water body data (GSWO & G3WBM), cloud-sourced open geography database (OpenStreetMap). The new hydrography data covers the entire globe (including boreal regions above 60N), and it represents more detailed structure of the world river network and contains consistent supplementary data layers such as hydrologically adjusted elevations and river channel width. In the AGU meeting, the developing methodology, assessed quality, and potential applications of the new global hydrography data will be introduced.
Centrality and transverse momentum dependence of dihadron correlations in a hydrodynamic model
Castilho, Wagner M.; Qian, Wei-Liang
2018-06-01
In this work, we study the centrality as well as transverse momentum dependence of the dihadron correlation for Au+Au collisions at 200A GeV. The numerical simulations are carried out by using a hydrodynamical code NeXSPheRIO, where the initial conditions are obtained from a Regge-Gribov based microscopic model, NeXuS. In our calculations, the centrality windows are evaluated regarding multiplicity. The final correlations are obtained by the background subtraction via ZYAM methods, where higher harmonics are considered explicitly. The correlations are evaluated for the 0-20%, 20%-40% and 60%-92% centrality windows. Also, the transverse momentum dependence of the dihadron correlations is investigated. The obtained results are compared with experimental data. It is observed that the centrality dependence of the "ridge" and "double shoulder" structures is in consistency with the data. Based on specific set of parameters employed in the present study, it is found that different ZYAM subtraction schemes might lead to different features in the resultant correlations.
Hydrodynamical simulations of coupled and uncoupled quintessence models - II. Galaxy clusters
Carlesi, Edoardo; Knebe, Alexander; Lewis, Geraint F.; Yepes, Gustavo
2014-04-01
We study the z = 0 properties of clusters (and large groups) of galaxies within the context of interacting and non-interacting quintessence cosmological models, using a series of adiabatic SPH simulations. Initially, we examine the average properties of groups and clusters, quantifying their differences in ΛCold Dark Matter (ΛCDM), uncoupled Dark Energy (uDE) and coupled Dark Energy (cDE) cosmologies. In particular, we focus upon radial profiles of the gas density, temperature and pressure, and we also investigate how the standard hydrodynamic equilibrium hypothesis holds in quintessence cosmologies. While we are able to confirm previous results about the distribution of baryons, we also find that the main discrepancy (with differences up to 20 per cent) can be seen in cluster pressure profiles. We then switch attention to individual structures, mapping each halo in quintessence cosmology to its ΛCDM counterpart. We are able to identify a series of small correlations between the coupling in the dark sector and halo spin, triaxiality and virialization ratio. When looking at spin and virialization of dark matter haloes, we find a weak (5 per cent) but systematic deviation in fifth force scenarios from ΛCDM.
Gas Removal in the Ursa Minor Galaxy: Linking Hydrodynamics and Chemical Evolution Models
Energy Technology Data Exchange (ETDEWEB)
Caproni, Anderson; Lanfranchi, Gustavo Amaral; Baio, Gabriel Henrique Campos; Kowal, Grzegorz [Núcleo de Astrofísica Teórica, Universidade Cruzeiro do Sul, R. Galvão Bueno 868, Liberdade, 01506-000, São Paulo, SP (Brazil); Falceta-Gonçalves, Diego, E-mail: anderson.caproni@cruzeirodosul.edu.br [Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Rua Arlindo Bettio 1000, CEP 03828-000 São Paulo (Brazil)
2017-04-01
We present results from a non-cosmological, three-dimensional hydrodynamical simulation of the gas in the dwarf spheroidal galaxy Ursa Minor. Assuming an initial baryonic-to-dark-matter ratio derived from the cosmic microwave background radiation, we evolved the galactic gas distribution over 3 Gyr, taking into account the effects of the types Ia and II supernovae. For the first time, we used in our simulation the instantaneous supernovae rates derived from a chemical evolution model applied to spectroscopic observational data of Ursa Minor. We show that the amount of gas that is lost in this process is variable with time and radius, being the highest rates observed during the initial 600 Myr in our simulation. Our results indicate that types Ia and II supernovae must be essential drivers of the gas loss in Ursa Minor galaxy (and probably in other similar dwarf galaxies), but it is ultimately the combination of galactic winds powered by these supernovae and environmental effects (e.g., ram-pressure stripping) that results in the complete removal of the gas content.
Modelling Pulsar Glitches: The Hydrodynamics of Superfluid Vortex Avalanches in Neutron Stars
Khomenko, V.; Haskell, B.
2018-05-01
The dynamics of quantised vorticity in neutron star interiors is at the heart of most pulsar glitch models. However, the large number of vortices (up to ≈1013) involved in a glitch and the huge disparity in scales between the femtometre scale of vortex cores and the kilometre scale of the star makes quantum dynamical simulations of the problem computationally intractable. In this paper, we take a first step towards developing a mean field prescription to include the dynamics of vortices in large-scale hydrodynamical simulations of superfluid neutron stars. We consider a one-dimensional setup and show that vortex accumulation and differential rotation in the neutron superfluid lead to propagating waves, or `avalanches', as solutions for the equations of motion for the superfluid velocities. We introduce an additional variable, the fraction of free vortices, and test different prescriptions for its advection with the superfluid flow. We find that the new terms lead to solutions with a linear component in the rise of a glitch, and that, in specific setups, they can give rise to glitch precursors and even to decreases in frequency, or `anti-glitches'.
Improved Reactive Flow Modeling of the LX-17 Double Shock Experiments
Rehagen, Thomas J.; Vitello, Peter
2017-06-01
Over driven double shock experiments provide a measurement of the properties of the reaction product states of the insensitive high explosive LX-17 (92.5% TATB and 7.5% Kel-F by weight). These experiments used two flyer materials mounted on the end of a projectile to send an initial shock through the LX-17, followed by a second shock of a higher magnitude into the detonation products. In the experiments, the explosive was initially driven by the flyer plate to pressures above the Chapman-Jouguet state. The particle velocity history was recorded by Photonic Doppler Velocimetry (PDV) probes pointing at an aluminum foil coated LiF window. The PDV data shows a sharp initial shock and decay, followed by a rounded second shock. Here, the experimental results are compared to 2D and 3D Cheetah reactive flow modeling. Our default Cheetah reactive flow model fails to accurately reproduce the decay of the first shock or the curvature or strength of the second shock. A new model is proposed in which the carbon condensate produced in the reaction zone is controlled by a kinetic rate. This allows the carbon condensate to be initially out of chemical equilibrium with the product gas. This new model reproduces the initial detonation peak and decay, and matches the curvature of the second shock, however, it still over-predicts the strength of the second shock. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.
Shock Isolation Elements Testing for High Input Loadings. Volume II. Foam Shock Isolation Elements.
SHOCK ABSORBERS ), (*GUIDED MISSILE SILOS, SHOCK ABSORBERS ), (*EXPANDED PLASTICS, (*SHOCK(MECHANICS), REDUCTION), TEST METHODS, SHOCK WAVES, STRAIN(MECHANICS), LOADS(FORCES), MATHEMATICAL MODELS, NUCLEAR EXPLOSIONS, HARDENING.
Goodson, Matthew D.; Heitsch, Fabian; Eklund, Karl; Williams, Virginia A.
2017-07-01
Turbulence models attempt to account for unresolved dynamics and diffusion in hydrodynamical simulations. We develop a common framework for two-equation Reynolds-averaged Navier-Stokes turbulence models, and we implement six models in the athena code. We verify each implementation with the standard subsonic mixing layer, although the level of agreement depends on the definition of the mixing layer width. We then test the validity of each model into the supersonic regime, showing that compressibility corrections can improve agreement with experiment. For models with buoyancy effects, we also verify our implementation via the growth of the Rayleigh-Taylor instability in a stratified medium. The models are then applied to the ubiquitous astrophysical shock-cloud interaction in three dimensions. We focus on the mixing of shock and cloud material, comparing results from turbulence models to high-resolution simulations (up to 200 cells per cloud radius) and ensemble-averaged simulations. We find that the turbulence models lead to increased spreading and mixing of the cloud, although no two models predict the same result. Increased mixing is also observed in inviscid simulations at resolutions greater than 100 cells per radius, which suggests that the turbulent mixing begins to be resolved.
Energy Technology Data Exchange (ETDEWEB)
Temim, Tea [Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Slane, Patrick [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kolb, Christopher; Blondin, John [North Carolina State University, 421 Riddick Hall, Raleigh, NC 27695 (United States); Hughes, John P. [Rutgers University, 57 US Highway 1, New Brunswick, NJ 08901 (United States); Bucciantini, Niccoló [INAF Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi, 5, 50125, Firenze Italy (Italy)
2015-07-20
In an effort to better understand the evolution of composite supernova remnants (SNRs) and the eventual fate of relativistic particles injected by their pulsars, we present a multifaceted investigation of the interaction between a pulsar wind nebula (PWN) and its host SNR G327.1-1.1. Our 350 Chandra X-ray observations of SNR G327.1-1.1 reveal a highly complex morphology: a cometary structure resembling a bow shock, prong-like features extending into large arcs in the SNR interior, and thermal emission from the SNR shell. Spectral analysis of the non-thermal emission offers clues about the origin of the PWN structures, while enhanced abundances in the PWN region provide evidence for a mixing of supernova ejecta with PWN material. The overall morphology and spectral properties of the SNR suggest that the PWN has undergone an asymmetric interaction with the SNR reverse shock (RS), whichcan occur as a result of a density gradient in the ambient medium and/or a moving pulsar that displaces the PWN from the center of the remnant. We present hydrodynamical simulations of G327.1-1.1 that show that its morphology and evolution can be described by a ∼17,000-year-old composite SNR that expanded into a density gradient with an orientation perpendicular to the pulsar’s motion. We also show that the RS/PWN interaction scenario can reproduce the broadband spectrum of the PWN from radio to γ-ray wavelengths. The analysis and modeling presented in this work have important implications for our general understanding of the structure and evolution of composite SNRs.
Temim, Tea; Slane, Patrick; Kolb, Christopher; Blondin, John; Hughes, John P.; Bucciantini, Niccolo
2015-01-01
In an effort to better understand the evolution of composite supernova remnants (SNRs) and the eventual fate of relativistic particles injected by their pulsars, we present a multifaceted investigation of the interaction between a pulsar wind nebula (PWN) and its host SNR G327.1-1.1. Our 350 ks Chandra X-ray observations of SNR G327.1-1.1 reveal a highly complex morphology; a cometary structure resembling a bow shock, prong-like features extending into large arcs in the SNR interior, and thermal emission from the SNR shell. Spectral analysis of the non-thermal emission offers clues about the origin of the PWN structures, while enhanced abundances in the PWN region provide evidence for mixing of supernova ejecta with PWN material. The overall morphology and spectral properties of the SNR suggest that the PWN has undergone an asymmetric interaction with the SNR reverse shock(RS) that can occur as a result of a density gradient in the ambient medium and or a moving pulsar that displaces the PWN from the center of the remnant. We present hydrodynamical simulations of G327.1-1.1 that show that its morphology and evolution can be described by a approx. 17,000 yr old composite SNR that expanded into a density gradient with an orientation perpendicular to the pulsar's motion. We also show that the RSPWN interaction scenario can reproduce the broadband spectrum of the PWN from radio to gamma-ray wavelengths. The analysis and modeling presented in this work have important implications for our general understanding of the structure and evolution of composite SNRs.
Shock propagation in a heterogeneous medium
International Nuclear Information System (INIS)
Elbaz, D.
2011-01-01
In the frame of the inertial confinement fusion in direct drive, the use of foams as ablator allows the reduction of hydrodynamic instabilities created on the target by the direct laser irradiation. The foam is made up of carbon (CH) fibers impregnated of cryogenic deuterium-tritium (DT). In the past, studies have been carried out considering this foam to be a homogeneous medium. Yet, the foam presents heterogeneous features. We study the effects of this heterogeneity on the shock velocity when the laser irradiates the target. Thanks to experimental and numerical studies, we show that the shock propagates faster in the heterogeneous medium than in the homogeneous one with the same averaged density. This velocity gap depends on the presence rate of the CH fibers in the foam, the density ratio, the adiabatic coefficient and the foam geometry. We model the foam by different ways, more and more complex. The shock velocity modification is due to the baroclinicity which, during the interaction between the shock front and the interface, creates a vorticity deposition, responsible for the shock acceleration. Accordingly, an interface, which is plane and perpendicular to the front shock, maximizes the vorticity deposition and increases the velocity gaps between heterogeneous and homogeneous media. We found a correlation between the kinetic energy behind the shock front and the velocities relative difference. We compared our results with two analytical models. However, the system is not closed, so we can't for the moment develop a predictive model. (author) [fr
Nonlinear Monte Carlo model of superdiffusive shock acceleration with magnetic field amplification
Bykov, Andrei M.; Ellison, Donald C.; Osipov, Sergei M.
2017-03-01
Fast collisionless shocks in cosmic plasmas convert their kinetic energy flow into the hot downstream thermal plasma with a substantial fraction of energy going into a broad spectrum of superthermal charged particles and magnetic fluctuations. The superthermal particles can penetrate into the shock upstream region producing an extended shock precursor. The cold upstream plasma flow is decelerated by the force provided by the superthermal particle pressure gradient. In high Mach number collisionless shocks, efficient particle acceleration is likely coupled with turbulent magnetic field amplification (MFA) generated by the anisotropic distribution of accelerated particles. This anisotropy is determined by fast particle transport, making the problem strongly nonlinear and multiscale. Here, we present a nonlinear Monte Carlo model of collisionless shock structure with superdiffusive propagation of high-energy Fermi accelerated particles coupled to particle acceleration and MFA, which affords a consistent description of strong shocks. A distinctive feature of the Monte Carlo technique is that it includes the full angular anisotropy of the particle distribution at all precursor positions. The model reveals that the superdiffusive transport of energetic particles (i.e., Lévy-walk propagation) generates a strong quadruple anisotropy in the precursor particle distribution. The resultant pressure anisotropy of the high-energy particles produces a nonresonant mirror-type instability that amplifies compressible wave modes with wavelengths longer than the gyroradii of the highest-energy protons produced by the shock.
Modeling Hydrodynamics on the Wave Group Scale in Topographically Complex Reef Environments
Reyns, J.; Becker, J. M.; Merrifield, M. A.; Roelvink, J. A.
2016-02-01
The knowledge of the characteristics of waves and the associated wave-driven currents is important for sediment transport and morphodynamics, nutrient dynamics and larval dispersion within coral reef ecosystems. Reef-lined coasts differ from sandy beaches in that they have a steep offshore slope, that the non-sandy bottom topography is very rough, and that the distance between the point of maximum short wave dissipation and the actual coastline is usually large. At this short wave breakpoint, long waves are released, and these infragravity (IG) scale motions account for the bulk of the water level variance on the reef flat, the lagoon and eventually, the sandy beaches fronting the coast through run-up. These IG energy dominated water level motions are reinforced during extreme events such as cyclones or swells through larger incident band wave heights and low frequency wave resonance on the reef. Recently, a number of hydro(-morpho)dynamic models that have the capability to model these IG waves have successfully been applied to morphologically differing reef environments. One of these models is the XBeach model, which is curvilinear in nature. This poses serious problems when trying to model an entire atoll for example, as it is extremely difficult to build curvilinear grids that are optimal for the simulation of hydrodynamic processes, while maintaining the topology in the grid. One solution to remediate this problem of grid connectivity is the use of unstructured grids. We present an implementation of the wave action balance on the wave group scale with feedback to the flow momentum balance, which is the foundation of XBeach, within the framework of the unstructured Delft3D Flexible Mesh model. The model can be run in stationary as well as in instationary mode, and it can be forced by regular waves, time series or wave spectra. We show how the code is capable of modeling the wave generated flow at a number of topographically complex reef sites and for a number of
Detonability of turbulent white dwarf plasma: Hydrodynamical models at low densities
Fenn, Daniel
The origins of Type Ia supernovae (SNe Ia) remain an unsolved problem of contemporary astrophysics. Decades of research indicate that these supernovae arise from thermonuclear runaway in the degenerate material of white dwarf stars; however, the mechanism of these explosions is unknown. Also, it is unclear what are the progenitors of these objects. These missing elements are vital components of the initial conditions of supernova explosions, and are essential to understanding these events. A requirement of any successful SN Ia model is that a sufficient portion of the white dwarf plasma must be brought under conditions conducive to explosive burning. Our aim is to identify the conditions required to trigger detonations in turbulent, carbon-rich degenerate plasma at low densities. We study this problem by modeling the hydrodynamic evolution of a turbulent region filled with a carbon/oxygen mixture at a density, temperature, and Mach number characteristic of conditions found in the 0.8+1.2 solar mass (CO0812) model discussed by Fenn et al. (2016). We probe the ignition conditions for different degrees of compressibility in turbulent driving. We assess the probability of successful detonations based on characteristics of the identified ignition kernels, using Eulerian and Lagrangian statistics of turbulent flow. We found that material with very short ignition times is abundant in the case that turbulence is driven compressively. This material forms contiguous structures that persist over many ignition time scales, and that we identify as prospective detonation kernels. Detailed analysis of the kernels revealed that their central regions are densely filled with material characterized by short ignition times and contain the minimum mass required for self-sustained detonations to form. It is conceivable that ignition kernels will be formed for lower compressibility in the turbulent driving. However, we found no detonation kernels in models driven 87.5 percent
Assessment of RANS CFD modelling for pressurised thermal shock analysis
International Nuclear Information System (INIS)
Sander M Willemsen; Ed MJ Komen; Sander Willemsen
2005-01-01
Full text of publication follows: The most severe Pressurised Thermal Shock (PTS) scenario is a cold water Emergency Core Coolant (ECC) injection into the cold leg during a LOCA. The injected ECC water mixes with the hot fluid present in the cold leg and flows towards the downcomer where further mixing takes place. When the cold mixture comes into contact with the Reactor Pressure Vessel (RPV) wall, it may lead to large temperature gradients and consequently to high stresses in the RPV wall. Knowledge of these thermal loads is important for RPV remnant life assessments. The existing thermal-hydraulic system codes currently applied for this purpose are based on one-dimensional approximations and can, therefore, not predict the complex three-dimensional flows occurring during ECC injection. Computational Fluid Dynamics (CFD) can be applied to predict these phenomena, with the ultimate benefit of improved remnant RPV life assessment. The present paper presents an assessment of various Reynolds Averaged Navier Stokes (RANS) CFD approaches for modeling the complex mixing phenomena occurring during ECC injection. This assessment has been performed by comparing the numerical results obtained using advanced turbulence models available in the CFX 5.6 CFD code in combination with a hybrid meshing strategy with experimental results of the Upper Plenum Test Facility (UPTF). The UPTF was a full-scale 'simulation' of the primary system of the four loop 1300 MWe Siemens/KWU Pressurised Water Reactor at Grafenrheinfeld. The test vessel upper plenum internals, downcomer and primary coolant piping were replicas of the reference plant, while other components, such as core, coolant pump and steam generators were replaced by simulators. From the extensive test programme, a single-phase fluid-fluid mixing experiment in the cold leg and downcomer was selected. Prediction of the mixing and stratification is assessed by comparison with the measured temperature profiles at several locations
International Nuclear Information System (INIS)
Abraham-shrauner, B.
1975-01-01
The development of solar wind shock models with tensor plasma pressure and the comparison of some of the shock models with the satellite data from Pioneer 6 through Pioneer 9 are reported. Theoretically, difficulties were found in non-turbulent fluid shock models for tensor pressure plasmas. For microscopic shock theories nonlinear growth caused by plasma instabilities was frequently not clearly demonstrated to lead to the formation of a shock. As a result no clear choice for a shock model for the bow shock or interplanetary tensor pressure shocks emerged
Zeng, Ming; Soric, Audrey; Roche, Nicolas
2013-09-01
In this study, total organic carbon (TOC) biodegradation was simulated by GPS-X software in biofilm reactors with carriers of plastic rings and glass beads under different hydraulic conditions. Hydrodynamic model by retention time distribution and biokinetic measurement by in-situ batch test served as two significant parts of model calibration. Experimental results showed that TOC removal efficiency was stable in both media due to the enough height of column, although the actual hydraulic volume changed during the variation of hydraulic condition. Simulated TOC removal efficiencies were close to experimental ones with low theil inequality coefficient values (below 0.15). Compared with glass beads, more TOC was removed in the filter with plastic rings due to the larger actual hydraulic volume and lower half saturation coefficient in spite of its lower maximum specific growth rate of biofilm, which highlighted the importance of calibrating hydrodynamic behavior and biokinetics. Copyright © 2013 Elsevier Ltd. All rights reserved.
Zhuravlev, V. M.
2017-09-01
Models for the dynamics of a dust-like medium in the self-gravity field are investigated. Solutions of the corresponding problems are constructed by the method of hydrodynamic substitutions generalizing the Cole-Hopf substitutions. The method is extended to multidimensional ideal and viscous fluid flows with cylindrical and spherical symmetries for which exact solutions are constructed. Solutions for the dynamics of self-gravitating dust with arbitrary initial distributions of both fluid density and velocity are constructed using special coordinate transformations. In particular, the problem of cosmological expansion is considered in terms of Newton's gravity theory. Models of a one-dimensional viscous dust fluid flow and some problems of gas hydrodynamics are considered. Examples of exact solutions and their brief analysis are provided.
A model for precursor structure in supercritical perpendicular, collisionless shock waves
International Nuclear Information System (INIS)
Sherwell, D.; Cairns, R.A.
1978-01-01
Magnetosonic solitons may be given smooth increasing profiles by assuming the presence within the wave of a current distribution Jsub(y)(x) of trapped ions perpendicular to Bsub(z)(x) and the wave velocity Vsub(x). Suitable ions are found immediately upstream of perpendicular collisionless shock waves and these are coincident with the often observed 'foot' in magnetic field profiles of moderately supercritical shocks. The theory is applied to previous experiments by modelling Jsub(y)(x), where Jsub(y)(x) is observed, the profiles in the foot are reproduced and explained. Insight into a number of features of fast shocks is obtained. (author)
Hydrodynamic modelling of extreme flood events in the Kashmir valley in India
Jain, Manoj; Parvaze, Sabah
2017-04-01
extreme flood events showed good agreement (within ±15%) with corresponding observed peak discharge. The model could simulated the most severe flood event of 2014 reasonably well with simulated peak discharge of 2055 m3/s which is just 3% more than the observed discharge. The developed hydrodynamic model may be useful in simulating extreme flood events in the Kashmir Valley with reasonably good reproduction of extreme flood events.
Yujun Yi; Caihong Tang; Zhifeng Yang; Shanghong Zhang; Cheng Zhang
2017-01-01
The long Middle Route of the South to North Water Transfer Project is composed of complex hydraulic structures (aqueduct, tunnel, control gate, diversion, culvert, and diverted siphon), which generate complex flow patterns. It is vital to simulate the flow patterns through hydraulic structures, but it is a challenging work to protect water quality and maintain continuous water transfer. A one-dimensional hydrodynamic and water quality model was built to understand the flow and pollutant movem...
Comparison and Validation of Hydrological E-Flow Methods through Hydrodynamic Modelling
Kuriqi, Alban; Rivaes, Rui; Sordo-Ward, Alvaro; Pinheiro, António N.; Garrote, Luis
2017-04-01
Flow regime determines physical habitat conditions and local biotic configuration. The development of environmental flow guidelines to support the river integrity is becoming a major concern in water resources management. In this study, we analysed two sites located in southern part of Portugal, respectively at Odelouca and Ocreza Rivers, characterised by the Mediterranean climate. Both rivers are almost in pristine condition, not regulated by dams or other diversion construction. This study presents an analysis of the effect on fish habitat suitability by the implementation of different hydrological e-flow methods. To conduct this study we employed certain hydrological e-flow methods recommended by the European Small Hydropower Association (ESHA). River hydrology assessment was based on approximately 30 years of mean daily flow data, provided by the Portuguese Water Information System (SNIRH). The biological data, bathymetry, physical and hydraulic features, and the Habitat Suitability Index for fish species were collected from extensive field works. We followed the Instream Flow Incremental Methodology (IFIM) to assess the flow-habitat relationship taking into account the habitat suitability of different instream flow releases. Initially, we analysed fish habitat suitability based on natural conditions, and we used it as reference condition for other scenarios considering the chosen hydrological e-flow methods. We accomplished the habitat modelling through hydrodynamic analysis by using River-2D model. The same methodology was applied to each scenario by considering as input the e-flows obtained from each of the hydrological method employed in this study. This contribution shows the significance of ecohydrological studies in establishing a foundation for water resources management actions. Keywords: ecohydrology, e-flow, Mediterranean rivers, river conservation, fish habitat, River-2D, Hydropower.
Directory of Open Access Journals (Sweden)
Boronina Lyudmila Vladimirovna
2012-12-01
Full Text Available Improvement of water intake technologies are of great importance. These technologies are required to provide high quality water intake and treatment; they must be sufficiently simple and reliable, and they must be easily adjustable to particular local conditions. A mathematical model of a water supply area near the filtering water intake is proposed. On its basis, a software package designated for the calculation of parameters of the supply area along with its graphical representation is developed. To improve the efficiency of water treatment plants, the authors propose a new method of their integration into the landscape by taking account of velocity distributions in the water supply area within the water reservoir where the plant installation is planned. In the proposed relationship, the filtration rate and the scattering rate at the outlet of the supply area are taken into account, and they assure more precise projections of the inlet velocity. In the present study, assessment of accuracy of the mathematical model involving the scattering of a turbulent flow has been done. The assessment procedure is based on verification of the mean values equality hypothesis and on comparison with the experimental data. The results and conclusions obtained by means of the method developed by the authors have been verified through comparison of deviations of specific values calculated through the employment of similar algorithms in MathCAD, Maple and PLUMBING. The method of the water supply area analysis, with the turbulent scattering area having been taken into account, and the software package enable to numerically estimate the efficiency of the pre-purification process by tailoring a number of parameters of the filtering component of the water intake to the river hydrodynamic properties. Therefore, the method and the software package provide a new tool for better design, installation and operation of water treatment plants with respect to filtration and
Kordilla, Jannes; Pan, Wenxiao; Tartakovsky, Alexandre
2014-12-14
We propose a novel smoothed particle hydrodynamics (SPH) discretization of the fully coupled Landau-Lifshitz-Navier-Stokes (LLNS) and stochastic advection-diffusion equations. The accuracy of the SPH solution of the LLNS equations is demonstrated by comparing the scaling of velocity variance and the self-diffusion coefficient with kinetic temperature and particle mass obtained from the SPH simulations and analytical solutions. The spatial covariance of pressure and velocity fluctuations is found to be in a good agreement with theoretical models. To validate the accuracy of the SPH method for coupled LLNS and advection-diffusion equations, we simulate the interface between two miscible fluids. We study formation of the so-called "giant fluctuations" of the front between light and heavy fluids with and without gravity, where the light fluid lies on the top of the heavy fluid. We find that the power spectra of the simulated concentration field are in good agreement with the experiments and analytical solutions. In the absence of gravity, the power spectra decay as the power -4 of the wavenumber-except for small wavenumbers that diverge from this power law behavior due to the effect of finite domain size. Gravity suppresses the fluctuations, resulting in much weaker dependence of the power spectra on the wavenumber. Finally, the model is used to study the effect of thermal fluctuation on the Rayleigh-Taylor instability, an unstable dynamics of the front between a heavy fluid overlaying a light fluid. The front dynamics is shown to agree well with the analytical solutions.
Parkin, E. R.; Pittard, J. M.; Corcoran, M. F.; Hamaguchi, K.
2011-01-01
Three-dimensional adaptive mesh refinement hydrodynamical simulations of the wind-wind collision between the enigmatic supermassive star η Car and its mysterious companion star are presented which include radiative driving of the stellar winds, gravity, optically thin radiative cooling, and orbital motion. Simulations with static stars with a periastron passage separation reveal that the preshock companion star's wind speed is sufficiently reduced so that radiative cooling in the postshock gas becomes important, permitting the runaway growth of nonlinear thin-shell instabilities (NTSIs) which massively distort the wind-wind collision region (WCR). However, large-scale simulations, which include the orbital motion of the stars, show that orbital motion reduces the impact of radiative inhibition and thus increases the acquired preshock velocities. As such, the postshock gas temperature and cooling time see a commensurate increase, and sufficient gas pressure is preserved to stabilize the WCR against catastrophic instability growth. We then compute synthetic X-ray spectra and light curves and find that, compared to previous models, the X-ray spectra agree much better with XMM-Newton observations just prior to periastron. The narrow width of the 2009 X-ray minimum can also be reproduced. However, the models fail to reproduce the extended X-ray minimum from previous cycles. We conclude that the key to explaining the extended X-ray minimum is the rate of cooling of the companion star's postshock wind. If cooling is rapid then powerful NTSIs will heavily disrupt the WCR. Radiative inhibition of the companion star's preshock wind, albeit with a stronger radiation-wind coupling than explored in this work, could be an effective trigger.
International Nuclear Information System (INIS)
Parkin, E. R.; Pittard, J. M.; Corcoran, M. F.; Hamaguchi, K.
2011-01-01
Three-dimensional adaptive mesh refinement hydrodynamical simulations of the wind-wind collision between the enigmatic supermassive star η Car and its mysterious companion star are presented which include radiative driving of the stellar winds, gravity, optically thin radiative cooling, and orbital motion. Simulations with static stars with a periastron passage separation reveal that the preshock companion star's wind speed is sufficiently reduced so that radiative cooling in the postshock gas becomes important, permitting the runaway growth of nonlinear thin-shell instabilities (NTSIs) which massively distort the wind-wind collision region (WCR). However, large-scale simulations, which include the orbital motion of the stars, show that orbital motion reduces the impact of radiative inhibition and thus increases the acquired preshock velocities. As such, the postshock gas temperature and cooling time see a commensurate increase, and sufficient gas pressure is preserved to stabilize the WCR against catastrophic instability growth. We then compute synthetic X-ray spectra and light curves and find that, compared to previous models, the X-ray spectra agree much better with XMM-Newton observations just prior to periastron. The narrow width of the 2009 X-ray minimum can also be reproduced. However, the models fail to reproduce the extended X-ray minimum from previous cycles. We conclude that the key to explaining the extended X-ray minimum is the rate of cooling of the companion star's postshock wind. If cooling is rapid then powerful NTSIs will heavily disrupt the WCR. Radiative inhibition of the companion star's preshock wind, albeit with a stronger radiation-wind coupling than explored in this work, could be an effective trigger.
Classifying and modelling spiral structures in hydrodynamic simulations of astrophysical discs
Forgan, D. H.; Ramón-Fox, F. G.; Bonnell, I. A.
2018-05-01
We demonstrate numerical techniques for automatic identification of individual spiral arms in hydrodynamic simulations of astrophysical discs. Building on our earlier work, which used tensor classification to identify regions that were `spiral-like', we can now obtain fits to spirals for individual arm elements. We show this process can even detect spirals in relatively flocculent spiral patterns, but the resulting fits to logarithmic `grand-design' spirals are less robust. Our methods not only permit the estimation of pitch angles, but also direct measurements of the spiral arm width and pattern speed. In principle, our techniques will allow the tracking of material as it passes through an arm. Our demonstration uses smoothed particle hydrodynamics simulations, but we stress that the method is suitable for any finite-element hydrodynamics system. We anticipate our techniques will be essential to studies of star formation in disc galaxies, and attempts to find the origin of recently observed spiral structure in protostellar discs.
Directory of Open Access Journals (Sweden)
Monica Pinardi
2015-04-01
Full Text Available Shallow fluvial lakes are dynamic ecosystems shaped by physical and biological factors and characterized by the coexistence of phytoplankton and macrophytes. Due to multiple interplaying factors, understanding the distribution of phytoplankton in fluvial lakes is a complex but fundamental issue, in the context of increasing eutrophication, climate change, and multiple water uses. We analyze the distribution of phytoplankton by combining remotely sensed maps of chlorophyll-a with a hydrodynamic model in a dammed fluvial lake (Mantua Superior Lake, Northern Italy. The numerical simulation of different conditions shows that the main hydrodynamic effects which influence algal distribution are related to the combined effect of advection due to wind forces and local currents, as well as to the presence of large gyres which induce recirculation and stagnation regions, favoring phytoplankton accumulation. Therefore, the general characters of the phytoplankton horizontal patchiness can be inferred from the results of the hydrodynamic model. Conversely, hyperspectral remote-sensing products can be used to validate this model, as they provide chlorophyll-a distribution maps. The integration of ecological, hydraulic, and remote-sensing techniques may therefore help the monitoring and protection of inland water quality, with important improvements in management actions by policy makers.
A 2D hydrodynamic-sedimentological model for gravel-bed rivers. Part I: theory and validation
Gabriel Kaless; Mario A. Lenzi; Luca Mao
2013-01-01
This paper presents a novel 2D-depth average model especially developed for gravel-bed rivers, named Lican-Leufú (Lican=pebble and Leufu=river, in Mapuche’s language, the native inhabitants of Central Patagonia, Argentina). The model consists of three components: a hydrodynamic, a sedimentological, and a morphological model. The flow of water is described by the depth-averaged Reynolds equations for unsteady, free-surface, shallow water flows. It includes the standard k-e model for turbulence...
Qin, Shunda; Ge, Hongxia; Cheng, Rongjun
2018-02-01
In this paper, a new lattice hydrodynamic model is proposed by taking delay feedback and flux change rate effect into account in a single lane. The linear stability condition of the new model is derived by control theory. By using the nonlinear analysis method, the mKDV equation near the critical point is deduced to describe the traffic congestion. Numerical simulations are carried out to demonstrate the advantage of the new model in suppressing traffic jam with the consideration of flux change rate effect in delay feedback model.
Synchronisation under shocks: The Lévy Kuramoto model
Roberts, Dale; Kalloniatis, Alexander C.
2018-04-01
We study the Kuramoto model of identical oscillators on Erdős-Rényi (ER) and Barabasi-Alberts (BA) scale free networks examining the dynamics when perturbed by a Lévy noise. Lévy noise exhibits heavier tails than Gaussian while allowing for their tempering in a controlled manner. This allows us to understand how 'shocks' influence individual oscillator and collective system behaviour of a paradigmatic complex system. Skewed α-stable Lévy noise, equivalent to fractional diffusion perturbations, are considered, but overlaid by exponential tempering of rate λ. In an earlier paper we found that synchrony takes a variety of forms for identical Kuramoto oscillators subject to stable Lévy noise, not seen for the Gaussian case, and changing with α: a noise-induced drift, a smooth α dependence of the point of cross-over of synchronisation point of ER and BA networks, and a severe loss of synchronisation at low values of α. In the presence of tempering we observe both analytically and numerically a dramatic change to the α synchronisation is sustained over a larger range of values of the 'noise strength' σ, improved compared to the α > 1 tempered cases. Analytically we study the system close to the phase synchronised fixed point and solve the tempered fractional Fokker-Planck equation. There we observe that densities show stronger support in the basin of attraction at low α for fixed coupling, σ and tempering λ. We then perform numerical simulations for networks of size N = 1000 and average degree d ¯ = 10. There, we compute the order parameter r as a function of σ for fixed α and λ and observe values of r ≈ 1 over larger ranges of σ for α synchronisation down to low values of α. We propose a mechanism for this in terms of the basic shape of the tempered stable Lévy densities for various α and how it feeds into Kuramoto oscillator dynamics and illustrate this with examples of specific paths.
Model atmospheres with periodic shocks. [pulsations and mass loss in variable stars
Bowen, G. H.
1989-01-01
The pulsation of a long-period variable star generates shock waves which dramatically affect the structure of the star's atmosphere and produce conditions that lead to rapid mass loss. Numerical modeling of atmospheres with periodic shocks is being pursued to study the processes involved and the evolutionary consequences for the stars. It is characteristic of these complex dynamical systems that most effects result from the interaction of various time-dependent processes.
Electrical Resistivity Imaging and Hydrodynamic Modeling of Convective Fingering in a Sabkha Aquifer
Van Dam, Remke; Eustice, Brian; Hyndman, David; Wood, Warren; Simmons, Craig
2014-05-01
Free convection, or fluid motion driven by density differences, is an important groundwater flow mechanism that can enhance transport and mixing of heat and solutes in the subsurface. Various issues of environmental and societal relevance are exacerbated convective mixing; it has been studied in the context of dense contaminant plumes, nuclear waste disposal, greenhouse gas sequestration, the impacts of sea level rise and saline intrusion on drinking water resources. The basic theory behind convective flow in porous media is well understood, but important questions regarding this process in natural systems remain unanswered. Most previous research on this topic has focused on theory and modeling, with only limited attention to experimental studies and field measurements. The few published studies present single snapshots, making it difficult to quantify transient changes in these systems. Non-invasive electrical methods have the potential to exploit the relation between solute concentrations and electrical conductance of a fluid, and thereby estimate fluid salinity differences in time and space. We present the results of a two-year experimental study at a shallow sabkha aquifer in the United Arab Emirates, about 50 km southwest of the city of Abu Dhabi along the coast of the Arabian Gulf, that was designed to explore the transient nature of free convection. Electrical resistivity tomography (ERT) data documented the presence of convective fingers following a significant rainfall event. One year later, the complex fingering pattern had completely disappeared. This observation is supported by analysis of the aquifer solute budget as well as hydrodynamic modeling of the system. The transient dynamics of the gravitational instabilities in the modeling results are in agreement with the timing observed in the time-lapse ERT data. Our experimental observations and modeling are consistent with the hypothesis that the instabilities arose from a dense brine that infiltrated
Performance of a process-based hydrodynamic model in predicting shoreline change
Safak, I.; Warner, J. C.; List, J. H.
2012-12-01
Shoreline change is controlled by a complex combination of processes that include waves, currents, sediment characteristics and availability, geologic framework, human interventions, and sea level rise. A comprehensive data set of shoreline position (14 shorelines between 1978-2002) along the continuous and relatively non-interrupted North Carolina Coast from Oregon Inlet to Cape Hatteras (65 km) reveals a spatial pattern of alternating erosion and accretion, with an erosional average shoreline change rate of -1.6 m/yr and up to -8 m/yr in some locations. This data set gives a unique opportunity to study long-term shoreline change in an area hit by frequent storm events while relatively uninfluenced by human interventions and the effects of tidal inlets. Accurate predictions of long-term shoreline change may require a model that accurately resolves surf zone processes and sediment transport patterns. Conventional methods for predicting shoreline change such as one-line models and regression of shoreline positions have been designed for computational efficiency. These methods, however, not only have several underlying restrictions (validity for small angle of wave approach, assuming bottom contours and shoreline to be parallel, depth of closure, etc.) but also their empirical estimates of sediment transport rates in the surf zone have been shown to vary greatly from the calculations of process-based hydrodynamic models. We focus on hind-casting long-term shoreline change using components of the process-based, three-dimensional coupled-ocean-atmosphere-wave-sediment transport modeling system (COAWST). COAWST is forced with historical predictions of atmospheric and oceanographic data from public-domain global models. Through a method of coupled concurrent grid-refinement approach in COAWST, the finest grid with resolution of O(10 m) that covers the surf zone along the section of interest is forced at its spatial boundaries with waves and currents computed on the grids
Shock-darkening in ordinary chondrites: impact modelling
Czech Academy of Sciences Publication Activity Database
Moreau, J.; Kohout, Tomáš; Wünnemann, K.
2016-01-01
Roč. 88, Special volume (2016), s. 285-285 ISSN 0367-5211. [ Nordic Geological Winter Meeting /32./. 13.01.2016-15.01.2016, Helsinki] Institutional support: RVO:67985831 Keywords : impact, shock * reflectance spectra * chondrite * meteorite * Chelyabinsk Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics http://www.geologinenseura.fi/bulletin/Special_Volume_1_2016/BGSF-NGWM2016_Abstract_Volume.pdf
Astrophysical radiative shocks: From modeling to laboratory experiments
Czech Academy of Sciences Publication Activity Database
Gonzales, N.; Stehlé, C.; Audit, E.; Busquet, M.; Rus, Bedřich; Thais, F.; Acef, O.; Barroso, P.; Bar-Shalom, A.; Bauduin, D.; Kozlová, Michaela; Lery, T.; Madouri, A.; Mocek, Tomáš; Polan, Jiří
2006-01-01
Roč. 24, - (2006), s. 535-540 ISSN 0263-0346 EU Projects: European Commission(XE) 506350 - LASERLAB-EUROPE; European Commission(XE) 5592 - JETSET Grant - others:CNRS(FR) PNPS Institutional research plan: CEZ:AV0Z10100523 Keywords : laboratory astrophysics * laser plasmas * radiative shock waves * radiative transfer Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.958, year: 2006
Energy Technology Data Exchange (ETDEWEB)
Reisch, F; Vayssier, G
1969-05-15
This non-linear model serves as one of the blocks in a series of codes to study the transient behaviour of BWR or PWR type reactors. This program is intended to be the hydrodynamic part of the BWR core representation or the hydrodynamic part of the PWR heat exchanger secondary side representation. The equations have been prepared for the CSMP digital simulation language. By using the most suitable integration routine available, the ratio of simulation time to real time is about one on an IBM 360/75 digital computer. Use of the slightly different language DSL/40 on an IBM 7044 computer takes about four times longer. The code has been tested against the Eindhoven loop with satisfactory agreement.
Luciano, Rezzolla
2013-01-01
Relativistic hydrodynamics is a very successful theoretical framework to describe the dynamics of matter from scales as small as those of colliding elementary particles, up to the largest scales in the universe. This book provides an up-to-date, lively, and approachable introduction to the mathematical formalism, numerical techniques, and applications of relativistic hydrodynamics. The topic is typically covered either by very formal or by very phenomenological books, but is instead presented here in a form that will be appreciated both by students and researchers in the field. The topics covered in the book are the results of work carried out over the last 40 years, which can be found in rather technical research articles with dissimilar notations and styles. The book is not just a collection of scattered information, but a well-organized description of relativistic hydrodynamics, from the basic principles of statistical kinetic theory, down to the technical aspects of numerical methods devised for the solut...
Directory of Open Access Journals (Sweden)
Jakub Langhammer
2017-11-01
Full Text Available This paper explores the potential of the joint application of unmanned aerial vehicle (UAV-based photogrammetry and an automated sensor network for building a hydrodynamic flood model of a montane stream. UAV-based imagery was used for three-dimensional (3D photogrammetric reconstruction of the stream channel, achieving a resolution of 1.5 cm/pixel. Automated ultrasonic water level gauges, operating with a 10 min interval, were used as a source of hydrological data for the model calibration, and the MIKE 21 hydrodynamic model was used for building the flood model. Three different horizontal schematizations of the channel—an orthogonal grid, curvilinear grid, and flexible mesh—were used to evaluate the effect of spatial discretization on the results. The research was performed on Javori Brook, a montane stream in the Sumava (Bohemian Forest Mountains, Czech Republic, Central Europe, featuring a fast runoff response to precipitation events and that is located in a core zone of frequent flooding. The studied catchments have been, since 2007, equipped with automated water level gauges and, since 2013, under repeated UAV monitoring. The study revealed the high potential of these data sources for applications in hydrodynamic modeling. In addition to the ultra-high levels of spatial and temporal resolution, the major contribution is in the method’s high operability, enabling the building of highly detailed flood models even in remote areas lacking conventional monitoring. The testing of the data sources and model setup indicated the limitations of the UAV reconstruction of the stream bathymetry, which was completed by the geodetic-grade global navigation satellite system (GNSS measurements. The testing of the different model domain schematizations did not indicate the substantial differences that are typical for conventional low-resolution data, proving the high reliability of the tested modeling workflow.
Holfeld, Johannes; Zimpfer, Daniel; Albrecht-Schgoer, Karin; Stojadinovic, Alexander; Paulus, Patrick; Dumfarth, Julia; Thomas, Anita; Lobenwein, Daniela; Tepeköylü, Can; Rosenhek, Raphael; Schaden, Wolfgang; Kirchmair, Rudolf; Aharinejad, Seyedhossein; Grimm, Michael
2016-12-01
Previously we have shown that epicardial shock-wave therapy improves left ventricular ejection fraction (LVEF) in a rat model of myocardial infarction. In the present experiments we aimed to address the safety and efficacy of epicardial shock-wave therapy in a preclinical large animal model and to further evaluate mechanisms of action of this novel therapy. Four weeks after left anterior descending (LAD) artery ligation in pigs, the animals underwent re-thoracotomy with (shock-wave group, n = 6) or without (control group, n = 5) epicardial shock waves (300 impulses at 0.38 mJ/mm 2 ) applied to the infarcted anterior wall. Efficacy endpoints were improvement of LVEF and induction of angiogenesis 6 weeks after shock-wave therapy. Safety endpoints were haemodynamic stability during treatment and myocardial damage. Four weeks after LAD ligation, LVEF decreased in both the shock-wave (43 ± 3%, p wave animals 6 weeks after treatment (62 ± 9%, p = 0.006); no improvement was observed in controls (41 ± 4%, p = 0.36), yielding a significant difference. Quantitative histology revealed significant angiogenesis 6 weeks after treatment (controls 2 ± 0.4 arterioles/high-power field vs treatment group 9 ± 3; p = 0.004). No acute or chronic adverse effects were observed. As a potential mechanism of action in vitro experiments showed stimulation of VEGF receptors after shock-wave treatment in human coronary artery endothelial cells. Epicardial shock-wave treatment in a large animal model of ischaemic heart failure exerted a positive effect on LVEF improvement and did not show any adverse effects. Angiogenesis was induced by stimulation of VEGF receptors. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.
Energy Technology Data Exchange (ETDEWEB)
Jaschke, P.
2000-02-01
Mathematical models of the dynamic performance of hydrodynamic couplings are developed using hybrid modelling, i.e. a combination of analytical physical modelling and black box identification. The models developed were verified by measurements on a model powertrain. [German] In dieser Arbeit werden mit Hilfe der hybriden Modellierung mathematische Modelle zur Beschreibung des dynamischen Betriebsverhaltens hydrodynamischer Kupplungen ermittelt. Die Hybride Modellierung stellt eine Kombination der analytisch physikalischen Modellierung und der Black-Box-Identifikation dar. Diese Modellierungsart ist ausgewaehlt worden, um die Vorteile der analytisch physikalischen Modellierung und der Black-Box-Identifikation hydrodynamischer Kupplungen zu verbinden und deren Nachteile gering zu halten. Auf dieser Basis ist eine Vorgehensweise vorgestellt worden, die die Ermittlung der Modelle mit wenig Aufwand ermoeglicht. Mit Hilfe der Modelltheorie wird gezeigt, wie die ermittelten mathematischen Modelle zur Simulation des dynamischen Betriebsverhaltens geometrisch aehnlicher Kupplungen unterschiedlicher Baugroessen verwendet werden koennen. Darueber hinaus wird dargelegt, wie die ermittelten Modelle mit Modellen anderer Antriebsstrangelemente gekoppelt werden koennen, um Antriebsstrangsimulationen zu ermoeglichen. Verifikationsmessungen an einem Modellantriebsstrang verdeutlichen die Guete und Verwendbarkeit der mathematischen Modelle. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Milovich, J. L., E-mail: milovich1@llnl.gov; Robey, H. F.; Clark, D. S.; Baker, K. L.; Casey, D. T.; Cerjan, C.; Field, J.; MacPhee, A. G.; Pak, A.; Patel, P. K.; Peterson, J. L.; Smalyuk, V. A.; Weber, C. R. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2015-12-15
Experimental results from indirectly driven ignition implosions during the National Ignition Campaign (NIC) [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] achieved a record compression of the central deuterium-tritium fuel layer with measured areal densities up to 1.2 g/cm{sup 2}, but with significantly lower total neutron yields (between 1.5 × 10{sup 14} and 5.5 × 10{sup 14}) than predicted, approximately 10% of the 2D simulated yield. An order of magnitude improvement in the neutron yield was subsequently obtained in the “high-foot” experiments [O. A. Hurricane et al., Nature 506, 343 (2014)]. However, this yield was obtained at the expense of fuel compression due to deliberately higher fuel adiabat. In this paper, the design of an adiabat-shaped implosion is presented, in which the laser pulse is tailored to achieve similar resistance to ablation-front instability growth, but with a low fuel adiabat to achieve high compression. Comparison with measured performance shows a factor of 3–10× improvement in the neutron yield (>40% of predicted simulated yield) over similar NIC implosions, while maintaining a reasonable fuel compression of >1 g/cm{sup 2}. Extension of these designs to higher laser power and energy is discussed to further explore the trade-off between increased implosion velocity and the deleterious effects of hydrodynamic instabilities.
Rapidity distributions in unequal nuclei collision at high energies and hydrodynamical model
International Nuclear Information System (INIS)
Zhuang Pengfei; Wang Zhengqing
1987-01-01
The mechanism of high-energy A'-A collision (A > A', A' 1/3 >> 1) and the space-time evolution of the fluid formed in the collision are analysed. The corresponding 1 + 1 dimensional hydrodynamical equations are established. The average rapidity distributions are estimated and compared with some cosmic ray events. The origin of the nonsymmetry of rapidity distribution is explained
Shang, Barry Z; Voulgarakis, Nikolaos K; Chu, Jhih-Wei
2012-07-28
This work illustrates that fluctuating hydrodynamics (FHD) simulations can be used to capture the thermodynamic and hydrodynamic responses of molecular fluids at the nanoscale, including those associated with energy and heat transfer. Using all-atom molecular dynamics (MD) trajectories as the reference data, the atomistic coordinates of each snapshot are mapped onto mass, momentum, and energy density fields on Eulerian grids to generate a corresponding field trajectory. The molecular length-scale associated with finite molecule size is explicitly imposed during this coarse-graining by requiring that the variances of density fields scale inversely with the grid volume. From the fluctuations of field variables, the response functions and transport coefficients encoded in the all-atom MD trajectory are computed. By using the extracted fluid properties in FHD simulations, we show that the fluctuations and relaxation of hydrodynamic fields quantitatively match with those observed in the reference all-atom MD trajectory, hence establishing compatibility between the atomistic and field representations. We also show that inclusion of energy transfer in the FHD equations can more accurately capture the thermodynamic and hydrodynamic responses of molecular fluids. The results indicate that the proposed MD-to-FHD mapping with explicit consideration of finite molecule size provides a robust framework for coarse-graining the solution phase of complex molecular systems.
Fish Pectoral Fin Hydrodynamics; Part III: Low Dimensional Models via POD Analysis
Bozkurttas, M.; Madden, P.
2005-11-01
The highly complex kinematics of the pectoral fin and the resulting hydrodynamics does not lend itself easily to analysis based on simple notions of pitching/heaving/paddling kinematics or lift/drag based propulsive mechanisms. A more inventive approach is needed to dissect the fin gait and gain insight into the hydrodynamic performance of the pectoral fin. The focus of the current work is on the hydrodynamics of the pectoral fin of a bluegill sunfish in steady forward motion. The 3D, time-dependent fin kinematics is obtained via a stereo-videographic technique. We employ proper orthogonal decomposition to extract the essential features of the fin gait and then use CFD to examine the hydrodynamics of simplified gaits synthesized from the POD modes. The POD spectrum shows that the first two, three and five POD modes capture 55%, 67%, and 80% of the motion respectively. The first three modes are in particular highly distinct: Mode-1 is a ``cupping'' motion where the fin cups forward as it is abducted; Mode-2 is an ``expansion'' motion where the fin expands to present a larger area during adduction and finally Mode-3 involves a ``spanwise flick'' of the dorsal edge of the fin. Numerical simulation of flow past fin gaits synthesized from these modes lead to insights into the mechanisms of thrust production; these are discussed in detail.
Kinetic modeling of methyl butanoate in shock tube.
Huynh, Lam K; Lin, Kuang C; Violi, Angela
2008-12-25
An increased necessity for energy independence and heightened concern about the effects of rising carbon dioxide levels have intensified the search for renewable fuels that could reduce our current consumption of petrol and diesel. One such fuel is biodiesel, which consists of the methyl esters of fatty acids. Methyl butanoate (MB) contains the essential chemical structure of the long-chain fatty acids and a shorter, but similar, alkyl chain. This paper reports on a detailed kinetic mechanism for MB that is assembled using theoretical approaches. Thirteen pathways that include fuel decomposition, isomerization, and propagation steps were computed using ab initio calculations [J. Org. Chem. 2008, 73, 94]. Rate constants from first principles for important reactions in CO(2) formation, namely CH(3)OCO=CH(3) + CO(2) (R1) and CH(3)OCO=CH(3)O + CO (R2) reactions, are computed at high levels of theory and implemented in the mechanism. Using the G3B3 potential energy surface together with the B3LYP/6-31G(d) gradient, Hessian and geometries, the rate constants for reactions R1 and R2 are calculated using the Rice-Ramsperger-Kassel-Marcus theory with corrections from treatments for tunneling, hindered rotation, and variational effects. The calculated rate constants of reaction R1 differ from the data present in the literature by at most 20%, while those of reaction R2 are about a factor of 4 lower than the available values. The new kinetic model derived from ab initio simulations is combined with the kinetic mechanism presented by Fisher et al. [Proc. Combust. Inst. 2000, 28, 1579] together with the addition of the newly found six-centered unimolecular elimination reaction that yields ethylene and methyl acetate, MB = C(2)H(4) + CH(3)COOCH(3). This latter pathway requires the inclusion of the CH(3)COOCH(3) decomposition model suggested by Westbrook et al. [Proc. Combust. Inst. 2008, accepted]. The newly composed kinetic mechanism for MB is used to study the CO(2) formation
Well-posed Euler model of shock-induced two-phase flow in bubbly liquid
Tukhvatullina, R. R.; Frolov, S. M.
2018-03-01
A well-posed mathematical model of non-isothermal two-phase two-velocity flow of bubbly liquid is proposed. The model is based on the two-phase Euler equations with the introduction of an additional pressure at the gas bubble surface, which ensures the well-posedness of the Cauchy problem for a system of governing equations with homogeneous initial conditions, and the Rayleigh-Plesset equation for radial pulsations of gas bubbles. The applicability conditions of the model are formulated. The model is validated by comparing one-dimensional calculations of shock wave propagation in liquids with gas bubbles with a gas volume fraction of 0.005-0.3 with experimental data. The model is shown to provide satisfactory results for the shock propagation velocity, pressure profiles, and the shock-induced motion of the bubbly liquid column.
A composite model for a class of electric-discharge shock tubes
Elkins, R. T.; Baganoff, D.
1973-01-01
A gasdynamic model is presented and analyzed for a class of shock tubes that utilize both Joule heating and electromagnetic forces to produce high-speed shock waves. The model consists of several stages of acceleration in which acceleration to sonic conditions is achieved principally through heating, and further acceleration of the supersonic flow is obtained principally through use of electromagnetic forces. The utility of the model results from the fact that it predicts a quasi-steady flow process, mathematical analysis is straightforward, and it is even possible to remove one or more component stages and still have the model related to a possible shock-tube flow. Initial experiments have been performed where the electrical discharge configuration and current level were such that Joule heating was the dominant form of energy addition present. These experiments indicate that the predictions of the model dealing with heat addition correspond quite closely to reality. The experimental data together with the theory show that heat addition to the flowing driver gas after diaphragm rupture (approach used in the model) is much more effective in producing high-speed shock waves than heating the gas in the driver before diaphragm rupture, as in the case of the arc-driven shock tube.
International Nuclear Information System (INIS)
Zhou, Xiaojun; Wu, Changjie; Li, Yanting; Xi, Lifeng
2016-01-01
A periodic preventive maintenance modeling method is proposed for leased equipment with continuous internal degradation and stochastic external shock damage considered simultaneously, which can facilitate the equipment lessor to optimize the maintenance schedule for the same kind of equipment rented by different lessees. A novel interactive mechanism between the continuous internal degradation and the stochastic external shock damage is established on the hazard rate of the equipment with integrating the imperfect effect of maintenance. Two improvement factors are defined for the modeling of imperfect maintenance. The number of failures resulting from internal degradation and from external shocks are both mathematically deduced based on this interactive mechanism. The optimal preventive maintenance scheme is obtained by minimizing the cumulative maintenance cost throughout the lease period. Numerical example shows that the proposed preventive maintenance model not only can reflect the reliability status of the equipment but also can clearly distinguish between the impact from internal degradation and that from external shocks. - Highlights: • We propose an imperfect periodic preventive maintenance model for leased equipment. • It can distinguish between the impact from internal degradation and that from external shocks. • An internal–external interactive mechanism is proposed. • Two improvement factors are introduced into the modeling of imperfect maintenance. • The model is helpful for the PM scheduling of the same equipment rented by different lessees.
Shock structure in continuum models of gas dynamics: stability and bifurcation analysis
International Nuclear Information System (INIS)
Simić, Srboljub S
2009-01-01
The problem of shock structure in gas dynamics is analysed through a comparative study of two continuum models: the parabolic Navier–Stokes–Fourier model and the hyperbolic system of 13 moments equations modeling viscous, heat-conducting monatomic gases within the context of extended thermodynamics. When dissipative phenomena are neglected these models both reduce to classical Euler's equations of gas dynamics. The shock profile solution, assumed in the form of a planar travelling wave, reduces the problem to a system of ordinary differential equations, and equilibrium states appear to be stationary points of the system. It is shown that in both models an upstream equilibrium state suffers an exchange of stability when the shock speed crosses the critical value which coincides with the highest characteristic speed of the Euler's system. At the same time a downstream equilibrium state could be seen as a steady bifurcating solution, while the shock profile represents a heteroclinic orbit connecting the two stationary points. Using centre manifold reduction it is demonstrated that both models, although mathematically different, obey the same transcritical bifurcation pattern in the neighbourhood of the bifurcation point corresponding to the critical value of shock speed, the speed of sound
Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks
Mai, Chuhong; Desch, Steven J.; Boley, Aaron C.; Weiss, Benjamin P.
2018-04-01
Recent laboratory efforts have constrained the remanent magnetizations of chondrules and the magnetic field strengths to which the chondrules were exposed as they cooled below their Curie points. An outstanding question is whether the inferred paleofields represent the background magnetic field of the solar nebula or were unique to the chondrule-forming environment. We investigate the amplification of the magnetic field above background values for two proposed chondrule formation mechanisms, large-scale nebular shocks and planetary bow shocks. Behind large-scale shocks, the magnetic field parallel to the shock front is amplified by factors of ∼10–30, regardless of the magnetic diffusivity. Therefore, chondrules melted in these shocks probably recorded an amplified magnetic field. Behind planetary bow shocks, the field amplification is sensitive to the magnetic diffusivity. We compute the gas properties behind a bow shock around a 3000 km radius planetary embryo, with and without atmospheres, using hydrodynamics models. We calculate the ionization state of the hot, shocked gas, including thermionic emission from dust, thermal ionization of gas-phase potassium atoms, and the magnetic diffusivity due to Ohmic dissipation and ambipolar diffusion. We find that the diffusivity is sufficiently large that magnetic fields have already relaxed to background values in the shock downstream where chondrules acquire magnetizations, and that these locations are sufficiently far from the planetary embryos that chondrules should not have recorded a significant putative dynamo field generated on these bodies. We conclude that, if melted in planetary bow shocks, chondrules probably recorded the background nebular field.
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 1; Issue 9. Hydrodynamic Lubrication Experiment with 'Floating' Drops. Jaywant H Arakeri K R Sreenivas. General Article Volume 1 Issue 9 September 1996 pp 51-58. Fulltext. Click here to view fulltext PDF. Permanent link:
Milne-Thomson, L M
2011-01-01
This classic exposition of the mathematical theory of fluid motion is applicable to both hydrodynamics and aerodynamics. Based on vector methods and notation with their natural consequence in two dimensions - the complex variable - it offers more than 600 exercises and nearly 400 diagrams. Prerequisites include a knowledge of elementary calculus. 1968 edition.
Energy Technology Data Exchange (ETDEWEB)
Bulatov, A.I.; Chernov, V.S.; Prokopov, L.I.; Proselkov, Yu.M.; Tikhonov, Yu.P.
1980-01-15
A hydrodynamic disperser is suggested which contains a housing, slit nozzles installed on a circular base arranged opposite from each other, resonators secured opposite the nozzle and outlet sleeve. In order to improve the effectiveness of dispersion by throttling the flow, each resonator is made in the form of a crimped plate with crimpings that decrease in height in a direction towards the nozzle.
Mathematical Model of a Shim Valve of a Monotube Shock Absorber
Directory of Open Access Journals (Sweden)
Paulius Skačkauskas
2016-12-01
Full Text Available In the work, a mathematical model of a shim valve, used in monotube shock absorbers, designed to determine the deformations of the shims which form during the exploitation of the shock absorbers, is presented. The characteristic of the damping force formed by the shock absorber depends on the deformations. In the designed model, the amount, geometric dimensions, arrangement and the material properties of the shims are evaluated, and the contact forces, which form between the shims, are determined. The described model of the shim valve is presented in the environment of the software package MATLAB/Simulink, the analysis of the designed model is done using the software package ANSYS 15.0.
Xu, Cong; Zhang, Jingjie; Bi, Xiaowei; Xu, Zheng; He, Yiliang; Gin, Karina Yew-Hoong
2017-12-01
An integrated 3D-hydrodynamic and emerging contaminant model was developed for better understanding of the fate and transport of emerging contaminants in Qingcaosha Reservoir. The reservoir, which supplies drinking water for nearly half of Shanghai's population, is located in Yangtze Delta. The integrated model was built by Delft3D suite, a fully integrated multidimensional modeling software. Atrazine and Bisphenol A (BPA) were selected as two representative emerging contaminants for the study in this reservoir. The hydrodynamic model was calibrated and validated against observations from 2011 to 2015 while the integrated model was calibrated against observations from 2014 to 2015 and then applied to explore the potential risk of high atrazine concentrations in the reservoir driven by agriculture activities. Our results show that the model is capable of describing the spatial and temporal patterns of water temperature, salinity and the dynamic distributions of two representative emerging contaminants (i.e. atrazine and BPA) in the reservoir. The physical and biodegradation processes in this study were found to play a crucial role in determining the fate and transport of atrazine and BPA in the reservoir. The model also provides an insight into the potential risk of emerging contaminants and possible mitigation thresholds. The integrated approach can be a very useful tool to support policy-makers in the future management of Qingcaosha Reservoir. Copyright © 2017 Elsevier Ltd. All rights reserved.
Busca, Claudia; Coluccelli, Alessandro; Valentini, Andrea; Benetazzo, Alvise; Bonaldo, Davide; Bortoluzzi, Giovanni; Carniel, Sandro; Falcieri, Francesco; Paccagnella, Tiziana; Ravaioli, Mariangela; Riminucci, Francesco; Sclavo, Mauro; Russo, Aniello
2014-05-01
The complex dynamics of the Adriatic Sea are the result of geographical position, orography and bathymetry, as well as rivers discharge and meteorological conditions that influence, more strongly, the shallow northern part. Such complexity requires a constant monitoring of marine conditions in order to support several activities (marine resources management, naval operations, emergency management, shipping, tourism, as well as scientific ones). Platforms, buoys and mooring located in Adriatic Sea supply almost continuously real time punctual information, which can be spatially extended, with some limitations, by drifters and remote sensing. Operational forecasting systems represent valid tools to provide a complete tridimensional coverage of the area, with a high spatial and temporal resolution. The Hydro-Meteo-Clima Service of the Emilia-Romagna Environmental Agency (ARPA-SIMC, Bologna, Italy) and the Dept. of Life and Environmental Sciences of Università Politecnica delle Marche (DISVA-UNIVPM, Ancona, Italy), in collaboration with the Institute of Marine Science of the National Research Council (ISMAR-CNR, Italy) operationally run several wave and hydrodynamic models on the Adriatic Sea. The main implementations are based on the Regional Ocean Modeling System (ROMS), the wave model Simulating WAves Nearshore (SWAN), and the coupling of the former two models in the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) system. Horizontal resolutions of the different systems range from the 2 km of AdriaROMS to the 0.5 km of the recently implemented northern Adriatic COAWST. Forecasts are produced every day for the subsequent 72 hour with hourly resolution. All the systems compute the fluxes exchanged through the interface with the atmosphere from the numerical weather prediction system named COSMO-I7, an implementation for Italy of the Consortium for Small-scale Modeling (COSMO) model, at 7 km horizontal resolution. Considering the several operational
Energy Technology Data Exchange (ETDEWEB)
Bożek, Piotr, E-mail: piotr.bozek@fis.agh.edu.pl
2016-12-15
The scenario assuming a collective expansion stage in collisions of small systems, p-A, d-Au, and {sup 3}He-Au is discussed. A review of the observables predicted in relativistic hydrodynamic models in comparison with experimental data is presented, with arguments indicating the presence of collective expansion. The limits of applicability of the hydrodynamic model are addressed. We briefly indicate possible applications of the collective flow in small systems to study the space-time dynamics at very small scales in relativistic collisions.
SSS: A code for computing one dimensional shock and detonation wave propagation
International Nuclear Information System (INIS)
Sun Chengwei
1986-01-01
The one-dimensional hydrodynamic code SSS for shock and detonation wave propagation in inert and reactive media is described. The elastic-plastic-hydrodynamic model and four burn techniques (the Arrhenius law, C-J volume, sharp shock and Forest Fire) are used. There are HOM and JWL options for the state equation of detonation products. Comparing with the SIN code published by LANL, the SSS code has several new options: laser effects, blast waves, diverging and instantaneous detonation waves with arbitrary initiation positions. Two examples are given to compare the SSS and SIN calculations with the experimental data
Development and Realization of a Shock Wave Test on Expert Flap Qualification Model
De Fruytier, C.; Dell'Orco, F.; Ullio, R.; Gomiero, F.
2012-07-01
This paper presents the methodology and the results of the shock test campaign conducted by TAS-I and TAS ETCA to qualify the EXPERT Flap in regards of shock wave and acoustic load generated by pyrocord detonation at stages 2/3 separation phase of the EXPERT vehicle. The design concept of the open flap (manufactured by MT AEROSPACE) is a fully integral manufactured, four sided control surface, with an additional stiffening rib and flanges to meet the first eigenfrequency and the allowable deformation requirement with a minimum necessary mass. The objectives were to reproduce equivalent loading at test article level in terms of pulse duration, front pressure, front velocity and acoustic emission. The Thales Alenia Space ETCA pyrotechnic shock test device is usually used to produce high level shocks by performing a shock on a test fixture supporting the unit under test. In this case, the facility has been used to produce a shock wave, with different requested physical characteristics, directed to the unit under test. Different configurations have been tried on a dummy of the unit to test, following an empirical process. This unusual work has lead to the definition of a nominal set- up meeting the requested physical parameters. Two blast sensors have been placed to acquire the pressure around the flap. The distance between the two sensors has allowed estimating the front pressure velocity. Then, several locations have been selected to acquire the acceleration responses on the unit when it was submitted to this environment. Additionally, a “standard” shock test has been performed on this model. The qualification of the flap, in regards of shock environment, has been successfully conducted.
Modeling of shock wave propagation in large amplitude ultrasound.
Pinton, Gianmarco F; Trahey, Gregg E
2008-01-01
The Rankine-Hugoniot relation for shock wave propagation describes the shock speed of a nonlinear wave. This paper investigates time-domain numerical methods that solve the nonlinear parabolic wave equation, or the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation, and the conditions they require to satisfy the Rankine-Hugoniot relation. Two numerical methods commonly used in hyperbolic conservation laws are adapted to solve the KZK equation: Godunov's method and the monotonic upwind scheme for conservation laws (MUSCL). It is shown that they satisfy the Rankine-Hugoniot relation regardless of attenuation. These two methods are compared with the current implicit solution based method. When the attenuation is small, such as in water, the current method requires a degree of grid refinement that is computationally impractical. All three numerical methods are compared in simulations for lithotripters and high intensity focused ultrasound (HIFU) where the attenuation is small compared to the nonlinearity because much of the propagation occurs in water. The simulations are performed on grid sizes that are consistent with present-day computational resources but are not sufficiently refined for the current method to satisfy the Rankine-Hugoniot condition. It is shown that satisfying the Rankine-Hugoniot conditions has a significant impact on metrics relevant to lithotripsy (such as peak pressures) and HIFU (intensity). Because the Godunov and MUSCL schemes satisfy the Rankine-Hugoniot conditions on coarse grids, they are particularly advantageous for three-dimensional simulations.
Hydrodynamic modeling of 3He–Au collisions at sNN=200 GeV
Directory of Open Access Journals (Sweden)
Piotr Bożek
2015-07-01
Full Text Available Collective flow and femtoscopy in ultrarelativistic 3He–Au collisions are investigated within the 3+1-dimensional (3+1D viscous event-by-event hydrodynamics. We evaluate elliptic and triangular flow coefficients as functions of the transverse momentum. We find the typical long-range ridge structures in the two-particle correlations in the relative azimuth and pseudorapidity, in the pseudorapidity directions of both Au and 3He. We also make predictions for the pionic interferometric radii, which decrease with the transverse momentum of the pion pair. All features found hint on collectivity of the dynamics of the system formed in 3He–Au collisions, with hydrodynamics leading to quantitative agreement with the up-to-now released data.
Butler, T.; Graham, L.; Estep, D.; Dawson, C.; Westerink, J. J.
2015-04-01
The uncertainty in spatially heterogeneous Manning's n fields is quantified using a novel formulation and numerical solution of stochastic inverse problems for physics-based models. The uncertainty is quantified in terms of a probability measure and the physics-based model considered here is the state-of-the-art ADCIRC model although the presented methodology applies to other hydrodynamic models. An accessible overview of the formulation and solution of the stochastic inverse problem in a mathematically rigorous framework based on measure theory is presented. Technical details that arise in practice by applying the framework to determine the Manning's n parameter field in a shallow water equation model used for coastal hydrodynamics are presented and an efficient computational algorithm and open source software package are developed. A new notion of "condition" for the stochastic inverse problem is defined and analyzed as it relates to the computation of probabilities. This notion of condition is investigated to determine effective output quantities of interest of maximum water elevations to use for the inverse problem for the Manning's n parameter and the effect on model predictions is analyzed.
Electromagnetically driven radiative shocks and their measurements
International Nuclear Information System (INIS)
Kondo, K.; Watanabe, M.; Nakajima, M.; Kawamura, T.; Horioka, K.
2005-01-01
Experimental results on a generation of strong shocks in a compact pulse power device are reported. The characteristics of strong shocks are different from hydrodynamical shocks' because they depend on not only collisions but radiation processes. Radiative shocks are relevant to high energy density phenomena such as the explosions of supernovae. When initial pressure is lower than about 50 mtorr, an interesting structure is confirmed at the shock front, which might indicate a phenomenon proceeded by the radiative process. (author)
Hydrodynamical simulations and semi-analytic models of galaxy formation: two sides of the same coin
Neistein, Eyal; Khochfar, Sadegh; Dalla Vecchia, Claudio; Schaye, Joop
2012-04-01
In this work we develop a new method to turn a state-of-the-art hydrodynamical cosmological simulation of galaxy formation (HYD) into a simple semi-analytic model (SAM). This is achieved by summarizing the efficiencies of accretion, cooling, star formation and feedback given by the HYD, as functions of the halo mass and redshift. The SAM then uses these functions to evolve galaxies within merger trees that are extracted from the same HYD. Surprisingly, by turning the HYD into a SAM, we conserve the mass of individual galaxies, with deviations at the level of 0.1 dex, on an object-by-object basis, with no significant systematics. This is true for all redshifts, and for the mass of stars and gas components, although the agreement reaches 0.2 dex for satellite galaxies at low redshift. We show that the same level of accuracy is obtained even in case the SAM uses only one phase of gas within each galaxy. Moreover, we demonstrate that the formation history of one massive galaxy provides sufficient information for the SAM to reproduce the population of galaxies within the entire cosmological box. The reasons for the small scatter between the HYD and SAM galaxies are as follows. (i) The efficiencies are matched as functions of the halo mass and redshift, meaning that the evolution within merger trees agrees on average. (ii) For a given galaxy, efficiencies fluctuate around the mean value on time-scales of 0.2-2 Gyr. (iii) The various mass components of galaxies are obtained by integrating the efficiencies over time, averaging out these fluctuations. We compare the efficiencies found here to standard SAM recipes and find that they often deviate significantly. For example, here the HYD shows smooth accretion that is less effective for low-mass haloes, and is always composed of hot or dilute gas; cooling is less effective at high redshift, and star formation changes only mildly with cosmic time. The method developed here can be applied in general to any HYD, and can thus
UAV based hydromorphological mapping of a river reach to improve hydrodynamic numerical models
Lükő, Gabriella; Baranya, Sándor; Rüther, Nils
2017-04-01
Unmanned Aerial Vehicles (UAVs) are increasingly used in the field of engineering surveys. In river engineering, or in general, water resources engineering, UAV based measurements have a huge potential. For instance, indirect measurements of the flow discharge using e.g. large-scale particle image velocimetry (LSPIV), particle tracking velocimetry (PTV), space-time image velocimetry (STIV) or radars became a real alternative for direct flow measurements. Besides flow detection, topographic surveys are also essential for river flow studies as the channel and floodplain geometry is the primary steering feature of the flow. UAVs can play an important role in this field, too. The widely used laser based topographic survey method (LIDAR) can be deployed on UAVs, moreover, the application of the Structure from Motion (SfM) method, which is based on images taken by UAVs, might be an even more cost-efficient alternative to reveal the geometry of distinct objects in the river or on the floodplain. The goal of this study is to demonstrate the utilization of photogrammetry and videogrammetry from airborne footage to provide geometry and flow data for a hydrodynamic numerical simulation of a 2 km long river reach in Albania. First, the geometry of the river is revealed from photogrammetry using the SfM method. Second, a more detailed view of the channel bed at low water level is taken. Using the fine resolution images, a Matlab based code, BASEGrain, developed by the ETH in Zürich, will be applied to determine the grain size characteristics of the river bed. This information will be essential to define the hydraulic roughness in the numerical model. Third, flow mapping is performed using UAV measurements and LSPIV method to quantitatively asses the flow field at the free surface and to estimate the discharge in the river. All data collection and analysis will be carried out using a simple, low-cost UAV, moreover, for all the data processing, open source, freely available
Comparison of the 1D flux theory with a 2D hydrodynamic secondary settling tank model.
Ekama, G A; Marais, P
2004-01-01
The applicability of the 1D idealized flux theory (1DFT) for design of secondary settling tanks (SSTs) is evaluated by comparing its predicted maximum surface overflow (SOR) and solids loading (SLR) rates with that calculated from the 2D hydrodynamic model SettlerCAD using as a basis 35 full scale SST stress tests conducted on different SSTs with diameters from 30 to 45m and 2.25 to 4.1 m side water depth, with and without Stamford baffles. From the simulations, a relatively consistent pattern appeared, i.e. that the 1DFT can be used for design but its predicted maximum SLR needs to be reduced by an appropriate flux rating, the magnitude of which depends mainly on SST depth and hydraulic loading rate (HLR). Simulations of the sloping bottom shallow (1.5-2.5 m SWD) Dutch SSTs tested by STOWa and the Watts et al. SST, all with doubled SWDs, and the Darvill new (4.1 m) and old (2.5 m) SSTs with interchanged depths, were run to confirm the sensitivity of the flux rating to depth and HLR. Simulations with and without a Stamford baffle were also done. While the design of the internal features of the SST, such as baffling, have a marked influence on the effluent SS concentration for underloaded SSTs, these features appeared to have only a small influence on the flux rating, i.e. capacity, of the SST, In the meantime until more information is obtained, it would appear that from the simulations so far that the flux rating of 0.80 of the 1DFT maximum SLR recommended by Ekama and Marais remains a reasonable value to apply in the design of full scale SSTs--for deep SSTs (4 m SWD) the flux rating could be increased to 0.85 and for shallow SSTs (2.5 m SWD) decreased to 0.75. It is recommended that (i) while the apparent interrelationship between SST flux rating and depth suggests some optimization of the volume of the SST, that this be avoided and that (ii) the depth of the SST be designed independently of the surface area as is usually the practice and once selected, the
Rapidity distributions in unequal nuclei collision at high energies and hydrodynamic model
International Nuclear Information System (INIS)
Zhuang Pengfei; Wang Zhengqing; Liu Liansou
1986-01-01
The mechanism of high-energy A'-A collisions (A>A', A'sup(1/3)>>1) and the space-time evolution of the fluid formed in the collision are analysed. The corresponding 1+1 dimensional hydrodynamic equations are set up. The average rapidity distributions are estimated and compared with cosmic ray data. The origin of the unsymmetry of rapidity distributions is explained. (orig.)
International Nuclear Information System (INIS)
Beznosov, A.; Davidov, D.; Khokhlov, D.
2001-01-01
This paper is about experimental study of hydrodynamics of target system construction with a spherical beam window (membrane). The visualization of current and current velocity fields in energy release area was considered. The findings are used to optimize the geometrical characteristics of target system. Also report contains the information about functioning accelerator-driven system, description it principle circuit and description of basic requirements what the target design should satisfy. (authors)
International Nuclear Information System (INIS)
Maevskii, K. K.; Kinelovskii, S. A.
2015-01-01
The numerical results of modeling of shock wave loading of mixtures with the SiO 2 component are presented. The TEC (thermodynamic equilibrium component) model is employed to describe the behavior of solid and porous multicomponent mixtures and alloys under shock wave loading. State equations of a Mie–Grüneisen type are used to describe the behavior of condensed phases, taking into account the temperature dependence of the Grüneisen coefficient, gas in pores is one of the components of the environment. The model is based on the assumption that all components of the mixture under shock-wave loading are in thermodynamic equilibrium. The calculation results are compared with the experimental data derived by various authors. The behavior of the mixture containing components with a phase transition under high dynamic loads is described
Have shock waves been observed in nuclear collisions
International Nuclear Information System (INIS)
Gudima, K.K.; Toneev, V.D.
Experimental data on shock wave phenomena in nuclear reactions are analyzed within the kinetic theory rather than that of the hydrodynamic approach. Beginning with a presentation of the model, which is a generalization of the cascade--evaporation model to the case of the interaction of two nuclei, it is then ascertained to what degree the developed approach is valid. Next on the basis of this model the results of experiments performed are examined to find the effects of a shock wave. The results of this analysis and the related set-up of new experiments are discussed also. 34 references
Energy Technology Data Exchange (ETDEWEB)
Salehi, N
1996-04-19
This study deals with the retention mechanisms of colloidal particles in porous media flows, and the subsequent reduction in permeability in the case of stable and non adsorbing colloids. It combines experimental results and modelling. This study has been realised with stable dispersion of monodispersed carboxylate polystyrene latexes negatively charged injected through negatively charged polycarbonate membranes having mono-sized cylindrical pores. The mean particle diameter is smaller than the mean pore diameter. Both batch and flow experiments in Nuclepore membranes have been done. The results of batch experiments have proved no adsorption of the colloidal latex particles on the surface of the Nuclepore membranes without flow at low salinity. In flow experiments at low particle concentration, only deposition on the upstream side of the membrane have been induced by hydrodynamic forces even for non adsorbing particles without creating any permeability reduction. The retention levels are zero at low and high Peclet numbers with a maximum at intermediate values. Partial plugging was observed at higher colloid concentration even at low salinity without any upstream surface deposition. The modelling of plugging processes is achieved by considering the particle concentration, fluid rate and ratio between the mean pore diameter and the mean particle diameter. This study can be particularly useful in the fields of water treatment and of restoration of lands following radioactive contamination. (author). 96 refs., 99 figs., 29 tabs.
Time-history of shock waves overrunning three-dimensional, cylindrical models
International Nuclear Information System (INIS)
Langheim, H.; Loeffler, E.
To investigate the time-history of the Mach-stem of a shock wave overrunning a nuclear power plant shadowgraphs of threedimensional, cylindrical models with a globe cap were analysed. These models simulating the containment building differ only in the height of the cylinder. They were exposed with shock waves of shock strengths of 1.2 and 1.4, being equal to a peak reflexion overpressure of 0.45 resp. 1.0 bar. The time-histories of the Mach-stem differ only slightly. For this reason it can be stated that these time-histories are independent of the shock strength and the height of the cylinder in the prescribed range of the research program. In comparison with values given in the literature great differences were found at the rear side near the stagnation point of the globe cap resp. the stagnation line of the cylinder. The measured time for overrunning of the shock wave is the same as the time of arrival of the pressure-pulse at the interesting point of the model. This knowledge is a necessary premise for pressure-measurings from which the total load of structure can be determined. (orig.) [de