Inertial forces affect fluid front displacement dynamics in a pore-throat network model.
Moebius, Franziska; Or, Dani
2014-08-01
The seemingly regular and continuous motion of fluid displacement fronts in porous media at the macroscopic scale is propelled by numerous (largely invisible) pore-scale abrupt interfacial jumps and pressure bursts. Fluid fronts in porous media are characterized by sharp phase discontinuities and by rapid pore-scale dynamics that underlie their motion; both attributes challenge standard continuum theories of these flow processes. Moreover, details of pore-scale dynamics affect front morphology and subsequent phase entrapment behind a front and thereby shape key macroscopic transport properties of the unsaturated zone. The study presents a pore-throat network model that focuses on quantifying interfacial dynamics and interactions along fluid displacement fronts. The porous medium is represented by a lattice of connected pore throats capable of detaining menisci and giving rise to fluid-fluid interfacial jumps (the study focuses on flow rate controlled drainage). For each meniscus along the displacement front we formulate a local inertial, capillary, viscous, and hydrostatic force balance that is then solved simultaneously for the entire front. The model enables systematic evaluation of the role of inertia and boundary conditions. Results show that while displacement patterns are affected by inertial forces mainly by invasion of throats with higher capillary resistance, phase entrapment (residual saturation) is largely unaffected by inertia, limiting inertial effects on hydrological properties behind a front. Interfacial jump velocities are often an order of magnitude larger than mean front velocity, are strongly dependent on geometrical throat dimensions, and become less predictable (more scattered) when inertia is considered. Model simulations of the distributions of capillary pressure fluctuations and waiting times between invasion events follow an exponential distribution and are in good agreement with experimental results. The modeling approach provides insights
A meshless front tracking method for the Euler equations of fluid dynamics
Witteveen, J.A.S.
2009-01-01
A second order front tracking method is developed for solving the Euler equations of inviscid fluid dynamics numerically. Front tracking methods are usually limited to first order accuracy, since they are based on a piecewise constant approximation of the solution. Here the second order convergence
Fibre laser cutting stainless steel: Fluid dynamics and cut front morphology
Pocorni, Jetro; Powell, John; Deichsel, Eckard; Frostevarg, Jan; Kaplan, Alexander F. H.
2017-01-01
In this paper the morphology of the laser cut front generated by fibre lasers was investigated by observation of the 'frozen' cut front, additionally high speed imaging (HSI) was employed to study the fluid dynamics on the cut front while cutting. During laser cutting the morphology and flow properties of the melt film on the cut front affect cut quality parameters such as cut edge roughness and dross (residual melt attached to the bottom of the cut edge). HSI observation of melt flow down a laser cutting front using standard cutting parameters is experimentally problematic because the cut front is narrow and surrounded by the kerf walls. To compensate for this, artificial parameters are usually chosen to obtain wide cut fronts which are unrepresentative of the actual industrial process. This paper presents a new experimental cutting geometry which permits HSI of the laser cut front using standard, commercial parameters. These results suggest that the cut front produced when cutting medium section (10 mm thick) stainless steel with a fibre laser and a nitrogen assist gas is covered in humps which themselves are covered by a thin layer of liquid. HSI observation and theoretical analysis reveal that under these conditions the humps move down the cut front at an average speed of approximately 0.4 m/s while the covering liquid flows at an average speed of approximately 1.1 m/s, with an average melt depth at the bottom of the cut zone of approximately 0.17 mm.
Steady dynamics of exothermic chemical wave fronts in van der Waals fluids
Dumazer, G.; Antoine, C.; Lemarchand, A.; Nowakowski, B.
2009-12-01
We study the steady dynamics of an exothermic Fisher-Kolmogorov-Petrovsky-Piskunov chemical wave front traveling in a one-dimensional van der Waals fluid. The propagating wave is initiated by a nonuniformity in reactant concentration contrary to usual combustion ignition processes. The heat release and activation energy of the reaction play the role of control parameters. We recently proved that the propagation of an exothermic chemical wave front in a perfect gas displays a forbidden interval of stationary wave front speeds [G. Dumazer, M. Leda, B. Nowakowski, and A. Lemarchand, Phys. Rev. E 78, 016309 (2008)]. We examine how this result is modified for nonideal fluids and determine the effect of the van der Waals parameters and fluid density on the bifurcation between diffusion flames and Chapman-Jouguet detonation waves as heat release increases. Analytical predictions are confirmed by the numerical solution of the hydrodynamic equations including reaction kinetics.
Porphyry-copper ore shells form at stable pressure-temperature fronts within dynamic fluid plumes.
Weis, P; Driesner, T; Heinrich, C A
2012-12-21
Porphyry-type ore deposits are major resources of copper and gold, precipitated from fluids expelled by crustal magma chambers. The metals are typically concentrated in confined ore shells within vertically extensive vein networks, formed through hydraulic fracturing of rock by ascending fluids. Numerical modeling shows that dynamic permeability responses to magmatic fluid expulsion can stabilize a front of metal precipitation at the boundary between lithostatically pressured up-flow of hot magmatic fluids and hydrostatically pressured convection of cooler meteoric fluids. The balance between focused heat advection and lateral cooling controls the most important economic characteristics, including size, shape, and ore grade. This self-sustaining process may extend to epithermal gold deposits, venting at active volcanoes, and regions with the potential for geothermal energy production.
Optimization of Fluid Front Dynamics in Porous Media Using Rate Control: I. Equal Mobility Fluids
Energy Technology Data Exchange (ETDEWEB)
Sundaryanto, Bagus; Yortsos, Yanis C.
1999-10-18
In applications involving this injection of a fluid in a porous medium to displace another fluid, a main objective is the maximization of the displacement efficiency. For a fixed arrangement of injection and production points (sources and sinks), such optimization is possible by controlling the injection rate policy. Despite its practical relevance, however, this aspect has received scant attention in the literature. In this paper, a fundamental approach based on optimal control theory, for the case when the fluids are miscible, of equal viscosity and in the absence of dispersion and gravity effects. Both homogeneous and heterogeneous porous media are considered. From a fluid dynamics viewpoint, this is a problem in the deformation of material lines in porous media, as a function of time-varying injection rates.
Optimization of fluid front dynamics in porous media using rate control. I. Equal mobility fluids
Energy Technology Data Exchange (ETDEWEB)
Sudaryanto, Bagus [Petroleum Engineering Program, Department of Chemical Engineering, University of Southern California, Los Angeles, California 90089-1211 (United States); Yortsos, Yannis C. [Petroleum Engineering Program, Department of Chemical Engineering, University of Southern California, Los Angeles, California 90089-1211 (United States)
2000-07-01
In applications involving the injection of a fluid in a porous medium to displace another fluid, a main objective is the maximization of the displacement efficiency. For a fixed arrangement of injection and production points (sources and sinks), such optimization is possible by controling the injection rate policy. Despite its practical relevance, however, this aspect has received scant attention in the literature. In this paper, we provide a fundamental approach based on optimal control theory, for the simplified case when the fluids are miscible, of equal viscosity, and in the absence of dispersion and gravity effects. Both homogeneous and heterogeneous porous media are considered. From a fluid dynamics viewpoint, this is a problem in the deformation of material lines in porous media, as a function of time-varying injection rates. It is shown that the optimal injection policy that maximizes the displacement efficiency, at the time of arrival of the injected fluid, is of the ''bang-bang'' type, in which the rates take their extreme values in the range allowed. This result applies to both homogeneous and heterogeneous media. Examples in simple geometries and for various constraints are shown, illustrating the efficiency improvement over the conventional approach of constant rate injection. In the heterogeneous case, the effect of the permeability heterogeneity, particularly its spatial correlation structure, on diverting the flow paths, is analyzed. It is shown that bang-bang injection remains the optimal approach, compared to constant rate, particularly if they were both designed under the assumption that the medium was homogeneous. Experiments in a homogeneous Hele-Shaw cell are found to be in good agreement with the theory. (c) 2000 American Institute of Physics.
Moebius, F.; Or, D.
2012-04-01
Many natural and engineering processes involve motion of fluid fronts in porous media, from infiltration and drainage in hydrology to reservoir management in petroleum engineering. Macroscopically smooth and continuous motion of displacement fronts involves numerous rapid interfacial jumps and local reconfigurations. Detailed observations of displacement processes in micromodels illustrate the wide array of fluid interfacial dynamics ranging from irregular jumping-pinning motions to gradual pore scale invasions. The pressure fluctuations associated with interfacial motions reflect not only pore geometry (as traditionally hypothesized) but there is a strong influence of boundary conditions (e.g., mean drainage rate). The time scales associated with waiting time distribution of individual invasion events and decay time of inertial oscillations (following a rapid interfacial jump) provide a means for distinguishing between displacement regimes. Direct observations using high-speed camera combined with concurrent pressure signal measurements were instrumental in clarifying influences of flow rates, pore size, and gravity on burst size distribution and waiting times. We compared our results with the early experimental and theoretical study on burst size and waiting time distribution during slow drainage processes of Måløy et al. [Måløy et al., 1992]. Results provide insights on critical invasion events that exert strong influence on macroscopic phenomena such as front morphology and residual phase entrapment behind leading to hysteresis. Måløy, K. J., L. Furuberg, J. Feder, and T. Jossang (1992), Dynamics of Slow Drainage in Porous-Media, Phys Rev Lett, 68(14), 2161-2164.
Computational Fluid Dynamics Modelling of a Midlatitude Small Scale upper Ocean Front
Directory of Open Access Journals (Sweden)
Pablo Cornejo
2016-01-01
Full Text Available A numerical model is implemented to describe fluid dynamic processes associated with mid-latitude small- scale (10 km upper ocean fronts by using modified state of the art computational fluid dynamics tools. A periodic system was simulated using three different turbulent closures: 1 URANS-Reynolds Stress Model (RSM, seven equation turbulence model, 2 LES-Standard Smagorinsky (SS, algebraic model, and 3 LES-Modified Smagorinsky, introducing a correction for non-isotropic grids (MS. The results show the front developing instabilities and generating submesoscale structures after four days of simulation. A strongly unstable shear flow is found to be confined within the mixed layer with a high Rossby number (Ro > 1 and high vertical velocity zones. The positive (negative vertical velocity magnitude is found to be approximately O(10−3 m/s(O(10−2 m/s, one (two order(s of magnitude larger than the vertical velocity outside the sub-mesoscale structures, where the magnitude is stable at O(10−4 m/s. The latter value is consistent with previous numerical and experimental studies that use coarser grid sizes and therefore do not explicitly calculate the small scale structures. The nonlinear flow introduced by the sub-mesoscale dynamics within the mixed layer and the non-isotropic grid used in the calculations generates a disparity between the predicted horizontal wave-number spectra computed using the RSM model with respect to the linear eddy viscosity model SS. The MS approach improves SS predictions. This improvement is more significant below the mixed layer in the absence of flow nonlinearities. The horizontal spectra predicted with the RSM model fits a slope of −3 for large scale structures and a slope between −2 and −5/3 for turbulent structures smaller than 300 m. This work contributes to the investigation of the physical and methodological aspects for the detailed modelling and understanding of small scale structures in ocean turbulence.
Moebius, F.; Or, D.
2012-12-01
Dynamics of fluid fronts in porous media shape transport properties of the unsaturated zone and affect management of petroleum reservoirs and their storage properties. What appears macroscopically as smooth and continuous motion of a displacement fluid front may involve numerous rapid interfacial jumps often resembling avalanches of invasion events. Direct observations using high-speed camera and pressure sensors in sintered glass micro-models provide new insights on the influence of flow rates, pore size, and gravity on invasion events and on burst size distribution. Fundamental differences emerge between geometrically-defined pores and "functional" pores invaded during a single burst (invasion event). The waiting times distribution of individual invasion events and decay times of inertial oscillations (following a rapid interfacial jump) are characteristics of different displacement regimes. An invasion percolation model with gradients and including the role of inertia provide a framework for linking flow regimes with invasion sequences and phase entrapment. Model results were compared with measurements and with early studies on invasion burst sizes and waiting times distribution during slow drainage processes by Måløy et al. [1992]. The study provides new insights into the discrete invasion events and their weak links with geometrically-deduced pore geometry. Results highlight factors controlling pore invasion events that exert strong influence on macroscopic phenomena such as front morphology and residual phase entrapment shaping hydraulic properties after the passage of a fluid front.
Pelce, Pierre
1989-01-01
In recent years, much progress has been made in the understanding of interface dynamics of various systems: hydrodynamics, crystal growth, chemical reactions, and combustion. Dynamics of Curved Fronts is an important contribution to this field and will be an indispensable reference work for researchers and graduate students in physics, applied mathematics, and chemical engineering. The book consist of a 100 page introduction by the editor and 33 seminal articles from various disciplines.
DEFF Research Database (Denmark)
Brorsen, Michael
These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University.......These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University....
Bernard, Peter S
2015-01-01
This book presents a focused, readable account of the principal physical and mathematical ideas at the heart of fluid dynamics. Graduate students in engineering, applied math, and physics who are taking their first graduate course in fluids will find this book invaluable in providing the background in physics and mathematics necessary to pursue advanced study. The book includes a detailed derivation of the Navier-Stokes and energy equations, followed by many examples of their use in studying the dynamics of fluid flows. Modern tensor analysis is used to simplify the mathematical derivations, thus allowing a clearer view of the physics. Peter Bernard also covers the motivation behind many fundamental concepts such as Bernoulli's equation and the stream function. Many exercises are designed with a view toward using MATLAB or its equivalent to simplify and extend the analysis of fluid motion including developing flow simulations based on techniques described in the book.
Ruban, Anatoly I
This is the first book in a four-part series designed to give a comprehensive and coherent description of Fluid Dynamics, starting with chapters on classical theory suitable for an introductory undergraduate lecture course, and then progressing through more advanced material up to the level of modern research in the field. The present Part 1 consists of four chapters. Chapter 1 begins with a discussion of Continuum Hypothesis, which is followed by an introduction to macroscopic functions, the velocity vector, pressure, density, and enthalpy. We then analyse the forces acting inside a fluid, and deduce the Navier-Stokes equations for incompressible and compressible fluids in Cartesian and curvilinear coordinates. In Chapter 2 we study the properties of a number of flows that are presented by the so-called exact solutions of the Navier-Stokes equations, including the Couette flow between two parallel plates, Hagen-Poiseuille flow through a pipe, and Karman flow above an infinite rotating disk. Chapter 3 is d...
FLUID EXCHANGE ACROSS THE EQUATORIAL FRONT
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
In this paper, the cusp-shaped wave pattern (Legeckis wave) along the Equatorial Front (EF) is modeled by a meandering jet, and the motion of fluid parcels in a two-dimensional kinematic model of the meandering jet along EF is studied using Melnikov's method. Results indicated that the velocity field of the cusp-shaped wave pattern can indeed be modeled by a meandering jet; that the EF will act as a barrier to fluid exchange if there is no variability, but that it is just the variability that moves the buoy across the EF.
FLUID EXCHANGE ACROSS THE EQUATORIAL FRONT
Institute of Scientific and Technical Information of China (English)
姜传丽; 吕建; 吴德星
2001-01-01
In this paper, the cusp-shaped wave pattern (Legeckis wave) along the Equatorial Front (EF) is modeled by a meandering jet, and the motion of fluid parcels in a two-dimensional kine-matic model of the meandering jet along EF is studied using Melnikov's method. Results indicated that the velocity field of the cusp-shaped wave pattern can indeed be modeled by a meandering jet; that the EF will act as a barrier to fluid exchange if there is no variability, but that it is just the variability that moves the buoy across the EF.
Directory of Open Access Journals (Sweden)
Kangji Li
2017-02-01
Full Text Available This paper is concerned with the development of a high-resolution and control-friendly optimization framework in enclosed environments that helps improve thermal comfort, indoor air quality (IAQ, and energy costs of heating, ventilation and air conditioning (HVAC system simultaneously. A computational fluid dynamics (CFD-based optimization method which couples algorithms implemented in Matlab with CFD simulation is proposed. The key part of this method is a data interactive mechanism which efficiently passes parameters between CFD simulations and optimization functions. A two-person office room is modeled for the numerical optimization. The multi-objective evolutionary algorithm—non-dominated-and-crowding Sorting Genetic Algorithm II (NSGA-II—is realized to explore the environment/energy Pareto front of the enclosed space. Performance analysis will demonstrate the effectiveness of the presented optimization method.
1983-11-01
pSUMMER- 1983 STAFF SeFlieri, Glenn Massachusetts Institute of Technology Howard , Louis Florida State University Malkus, Willem Massachusetts Institute of...Stern, Killworth, Malkus Front Row: Spiegel, Aref, Samelson, Veronis, Mellor, Howard , Jones, Tryggvason, Mory, Nilno, Flament, Corfield Inset: Voropaev...combining the formulae of Ruddick and Turner (1979) and Toole and Georgi (1981) on the thickness and growth rate of the double diffusive intrusions that
Fluid dynamics of dilatant fluid
DEFF Research Database (Denmark)
Nakanishi, Hiizu; Nagahiro, Shin-ichiro; Mitarai, Namiko
2012-01-01
A dense mixture of granules and liquid often shows a severe shear thickening and is called a dilatant fluid. We construct a fluid dynamics model for the dilatant fluid by introducing a phenomenological state variable for a local state of dispersed particles. With simple assumptions for an equation...... of the state variable, we demonstrate that the model can describe basic features of the dilatant fluid such as the stress-shear rate curve that represents discontinuous severe shear thickening, hysteresis upon changing shear rate, and instantaneous hardening upon external impact. An analysis of the model...... reveals that the shear thickening fluid shows an instability in a shear flow for some regime and exhibits the shear thickening oscillation (i.e., the oscillatory shear flow alternating between the thickened and the relaxed states). The results of numerical simulations are presented for one- and two...
Collisionless ion dynamics in the shock front
Gedalin, Michael
2016-07-01
In the vicinity of the shock front the dynamics of ions is governed by the macroscopic regular electric and magnetic field of the shock. Upon crossing the shock the thermal ions form a non-gyrotropic distribution. The pressure of these non-gyrotropic ions shapes the downstream magnetic field. High-energy ions behave in the shock front as test particles under the influence on the macroscopic fields. The reflection and transmission coefficients of high-energy ions at an oblique shock front is not sensitive to the shock structure and depends only on the global magnetic field change at the shock.
Miscible displacement fronts of shear thinning fluids inside rough fractures
Boschan, A; Ippolito, I; Chertcoff, R; Hulin, J P; Boschan, Alexandro; Auradou, Harold; Ippolito, Irene; Chertcoff, Ricardo; Hulin, Jean-Pierre
2006-01-01
The miscible displacement of a shear-thinning fluid by another of same rheological properties is studied experimentally in a transparent fracture by an optical technique imaging relative concentration distributions. The fracture walls have complementary self-affine geometries and are shifted laterally in the direction perpendicular to the mean flow velocity {\\bf U} : the flow field is strongly channelized and macro dispersion controls the front structure for P\\'{e}clet numbers above a few units. The global front width increases then linearly with time and reflects the velocity distribution between the different channels. In contrast, at the local scale, front spreading is similar to Taylor dispersion between plane parallel surfaces. Both dispersion mechanisms depend strongly on the fluid rheology which shifts from Newtonian to shear-thinning when the flow rate increases. In the latter domain, increasing the concentration enhances the global front width but reduces both Taylor dispersion (due to the flattening...
Shivamoggi, Bhimsen K
1998-01-01
"Although there are many texts and monographs on fluid dynamics, I do not know of any which is as comprehensive as the present book. It surveys nearly the entire field of classical fluid dynamics in an advanced, compact, and clear manner, and discusses the various conceptual and analytical models of fluid flow." - Foundations of Physics on the first edition. Theoretical Fluid Dynamics functions equally well as a graduate-level text and a professional reference. Steering a middle course between the empiricism of engineering and the abstractions of pure mathematics, the author focuses
Fiszdon, W
1965-01-01
Fluid Dynamics Transactions, Volume 2 compiles 46 papers on fluid dynamics, a subdiscipline of fluid mechanics that deals with fluid flow. The topics discussed in this book include developments in interference theory for aeronautical applications; diffusion from sources in a turbulent boundary layer; unsteady motion of a finite wing span in a compressible medium; and wall pressure covariance and comparison with experiment. The certain classes of non-stationary axially symmetric flows in magneto-gas-dynamics; description of the phenomenon of secondary flows in curved channels by means of co
Applications of fluid dynamics
Energy Technology Data Exchange (ETDEWEB)
Round, G.R.; Garg, V.K.
1986-01-01
This book describes flexible and practical approach to learning the basics of fluid dynamics. Each chapter is a self-contained work session and includes a fluid dynamics concept, an explanation of the principles involved, an illustration of their application and references on where more detailed discussions can be found.
Wave front distortion based fluid flow imaging
Iffa, Emishaw; Heidrich, Wolfgang
2013-03-01
In this paper, a transparent flow surface reconstruction based on wave front distortion is investigated. A camera lens is used to focus the image formed by the micro-lens array to the camera imaging plane. The irradiance of the captured image is transformed to frequency spectrum and then the x and y spatial components are separated. A rigid spatial translation followed by low pass filtering yields a single frequency component of the image intensity. Index of refraction is estimated from the inverse Fourier transform of the spatial frequency spectrum of the irradiance. The proposed method is evaluated with synthetic data of a randomly generated index of refraction value and used to visualize a fuel injection volumetric data.
Bird, R. Byron
1980-01-01
Problems in polymer fluid dynamics are described, including development of constitutive equations, rheometry, kinetic theory, flow visualization, heat transfer studies, flows with phase change, two-phase flow, polymer unit operations, and drag reduction. (JN)
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.
2011-01-10
AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.
Blazek, Jiri
2015-01-01
Computational Fluid Dynamics: Principles and Applications, Third Edition presents students, engineers, and scientists with all they need to gain a solid understanding of the numerical methods and principles underlying modern computation techniques in fluid dynamics. By providing complete coverage of the essential knowledge required in order to write codes or understand commercial codes, the book gives the reader an overview of fundamentals and solution strategies in the early chapters before moving on to cover the details of different solution techniques. This updated edition includes new
Videotapes and Movies on Fluid Dynamics and Fluid Machines
Carr, Bobbie; Young, Virginia E.
1996-01-01
Chapter 17 of Handbook of Fluid Dynamics and Fluid Machinery: Experimental and Computational Fluid Dynamics, Volume 11. A list of videorecordings and 16mm motion pictures about Fluid Dynamics and Fluid Machines.
Ogilvie, Gordon I.
2016-06-01
> These lecture notes and example problems are based on a course given at the University of Cambridge in Part III of the Mathematical Tripos. Fluid dynamics is involved in a very wide range of astrophysical phenomena, such as the formation and internal dynamics of stars and giant planets, the workings of jets and accretion discs around stars and black holes and the dynamics of the expanding Universe. Effects that can be important in astrophysical fluids include compressibility, self-gravitation and the dynamical influence of the magnetic field that is `frozen in' to a highly conducting plasma. The basic models introduced and applied in this course are Newtonian gas dynamics and magnetohydrodynamics (MHD) for an ideal compressible fluid. The mathematical structure of the governing equations and the associated conservation laws are explored in some detail because of their importance for both analytical and numerical methods of solution, as well as for physical interpretation. Linear and nonlinear waves, including shocks and other discontinuities, are discussed. The spherical blast wave resulting from a supernova, and involving a strong shock, is a classic problem that can be solved analytically. Steady solutions with spherical or axial symmetry reveal the physics of winds and jets from stars and discs. The linearized equations determine the oscillation modes of astrophysical bodies, as well as their stability and their response to tidal forcing.
Magoules, Frederic
2011-01-01
Exploring new variations of classical methods as well as recent approaches appearing in the field, Computational Fluid Dynamics demonstrates the extensive use of numerical techniques and mathematical models in fluid mechanics. It presents various numerical methods, including finite volume, finite difference, finite element, spectral, smoothed particle hydrodynamics (SPH), mixed-element-volume, and free surface flow.Taking a unified point of view, the book first introduces the basis of finite volume, weighted residual, and spectral approaches. The contributors present the SPH method, a novel ap
Pedlosky, Joseph
1979-01-01
The content of this book is based, largely, on the core curriculum in geophys ical fluid dynamics which I and my colleagues in the Department of Geophysical Sciences at The University of Chicago have taught for the past decade. Our purpose in developing a core curriculum was to provide to advanced undergraduates and entering graduate students a coherent and systematic introduction to the theory of geophysical fluid dynamics. The curriculum and the outline of this book were devised to form a sequence of courses of roughly one and a half academic years (five academic quarters) in length. The goal of the sequence is to help the student rapidly advance to the point where independent study and research are practical expectations. It quickly became apparent that several topics (e. g. , some aspects of potential theory) usually thought of as forming the foundations of a fluid-dynamics curriculum were merely classical rather than essential and could be, however sadly, dispensed with for our purposes. At the same ti...
Pedlosky, Joseph
1982-01-01
The content of this book is based, largely, on the core curriculum in geophys ical fluid dynamics which land my colleagues in the Department of Geophysical Sciences at The University of Chicago have taught for the past decade. Our purpose in developing a core curriculum was to provide to advanced undergraduates and entering graduate students a coherent and systematic introduction to the theory of geophysical fluid dynamics. The curriculum and the outline of this book were devised to form a sequence of courses of roughly one and a half academic years (five academic quarters) in length. The goal of the sequence is to help the student rapidly advance to the point where independent study and research are practical expectations. It quickly became apparent that several topics (e. g. , some aspects of potential theory) usually thought of as forming the foundations of a fluid-dynamics curriculum were merely classical rather than essential and could be, however sadly, dispensed with for our purposes. At the same tim...
Finite-time barriers to front propagation in two-dimensional fluid flows
Mahoney, John R
2015-01-01
Recent theoretical and experimental investigations have demonstrated the role of certain invariant manifolds, termed burning invariant manifolds (BIMs), as one-way dynamical barriers to reaction fronts propagating within a flowing fluid. These barriers form one-dimensional curves in a two-dimensional fluid flow. In prior studies, the fluid velocity field was required to be either time-independent or time-periodic. In the present study, we develop an approach to identify prominent one-way barriers based only on fluid velocity data over a finite time interval, which may have arbitrary time-dependence. We call such a barrier a burning Lagrangian coherent structure (bLCS) in analogy to Lagrangian coherent structures (LCSs) commonly used in passive advection. Our approach is based on the variational formulation of LCSs using curves of stationary "Lagrangian shear", introduced by Farazmand, Blazevski, and Haller [Physica D 278-279, 44 (2014)] in the context of passive advection. We numerically validate our techniqu...
High order fluid model for ionization fronts in streamer discharges
Markosyan, A.; Dujko, S.; Ebert, U.; Almeida, P.G.C.; Alves, L.L.; Guerra, V.
2012-01-01
A high order fluid model for streamer dynamics is developed by closing the system after the 4th mo- ment of the Boltzmann equation in local mean energy approximation. This is done by approximating the high order pressure tensor in the heat flux equation through the previous moments. The electric fi
The dynamics of oceanic fronts. I - The Gulf Stream
Kao, T. W.
1980-01-01
The establishment and maintenance of the mean hydrographic properties of large-scale density fronts in the upper ocean is considered. The dynamics is studied by posing an initial value problem starting with a near-surface discharge of buoyant water with a prescribed density deficit into an ambient stationary fluid of uniform density; full time dependent diffusion and Navier-Stokes equations are then used with constant eddy diffusion and viscosity coefficients, together with a constant Coriolis parameter. Scaling analysis reveals three independent scales of the problem including the radius of deformation of the inertial length, buoyancy length, and diffusive length scales. The governing equations are then suitably scaled and the resulting normalized equations are shown to depend on the Ekman number alone for problems of oceanic interest. It is concluded that the mean Gulf Stream dynamics can be interpreted in terms of a solution of the Navier-Stokes and diffusion equations, with the cross-stream circulation responsible for the maintenance of the front; this mechanism is suggested for the maintenance of the Gulf Stream dynamics.
Essential Computational Fluid Dynamics
Zikanov, Oleg
2011-01-01
This book serves as a complete and self-contained introduction to the principles of Computational Fluid Dynamic (CFD) analysis. It is deliberately short (at approximately 300 pages) and can be used as a text for the first part of the course of applied CFD followed by a software tutorial. The main objectives of this non-traditional format are: 1) To introduce and explain, using simple examples where possible, the principles and methods of CFD analysis and to demystify the `black box’ of a CFD software tool, and 2) To provide a basic understanding of how CFD problems are set and
Fluid dynamics of heart development.
Santhanakrishnan, Arvind; Miller, Laura A
2011-09-01
The morphology, muscle mechanics, fluid dynamics, conduction properties, and molecular biology of the developing embryonic heart have received much attention in recent years due to the importance of both fluid and elastic forces in shaping the heart as well as the striking relationship between the heart's evolution and development. Although few studies have directly addressed the connection between fluid dynamics and heart development, a number of studies suggest that fluids may play a key role in morphogenic signaling. For example, fluid shear stress may trigger biochemical cascades within the endothelial cells of the developing heart that regulate chamber and valve morphogenesis. Myocardial activity generates forces on the intracardiac blood, creating pressure gradients across the cardiac wall. These pressures may also serve as epigenetic signals. In this article, the fluid dynamics of the early stages of heart development is reviewed. The relevant work in cardiac morphology, muscle mechanics, regulatory networks, and electrophysiology is also reviewed in the context of intracardial fluid dynamics.
Stability of Kuramoto-Sivashinsky fronts in moving fluid
Vilela, P. M.; Vasquez, Desiderio A.
2014-12-01
We analyze the effects of an external Couette flow on reactions fronts described by the Kuramoto-Sivashinsky equation. The fronts propagate in a two-dimensional slab confined by two parallel plates moving in opposite directions. The fronts can propagate in the same direction or against the external flow. We obtain steady front solutions by solving numerically the nonlinear time-independent equations. A linear stability analysis determines the stability of the fronts. The fronts and their stability depend on the slab width and on the relative velocity between the plates. These parameters have the potential to modify unstable fronts into stable fronts. We compare our results with fronts developed under a Poiseuille flow.
Computational fluid dynamic applications
Energy Technology Data Exchange (ETDEWEB)
Chang, S.-L.; Lottes, S. A.; Zhou, C. Q.
2000-04-03
The rapid advancement of computational capability including speed and memory size has prompted the wide use of computational fluid dynamics (CFD) codes to simulate complex flow systems. CFD simulations are used to study the operating problems encountered in system, to evaluate the impacts of operation/design parameters on the performance of a system, and to investigate novel design concepts. CFD codes are generally developed based on the conservation laws of mass, momentum, and energy that govern the characteristics of a flow. The governing equations are simplified and discretized for a selected computational grid system. Numerical methods are selected to simplify and calculate approximate flow properties. For turbulent, reacting, and multiphase flow systems the complex processes relating to these aspects of the flow, i.e., turbulent diffusion, combustion kinetics, interfacial drag and heat and mass transfer, etc., are described in mathematical models, based on a combination of fundamental physics and empirical data, that are incorporated into the code. CFD simulation has been applied to a large variety of practical and industrial scale flow systems.
Palazzi, Elisa; Fraedrich, Klaus
2016-01-01
This volume provides an overview of the fluid aspects of the climate system, focusing on basic aspects as well as recent research developments. It will bring together contributions from diverse fields of the physical, mathematical and engineering sciences. The volume will be useful to doctorate students, postdocs and researchers working on different aspects of atmospheric, oceanic and environmental fluid dynamics. It will also be of interest to researchers interested in quantitatively understanding how fluid dynamics can be applied to the climate system, and to climate scientists willing to gain a deeper insight into the fluid mechanics underlying climate processes.
OBJECTIVITY REQUIREMENT FOR FLUID DYNAMICS
Institute of Scientific and Technical Information of China (English)
邹文楠
2003-01-01
A new flow theory is established through the objectivity requirement on the fluid dynamics. It was known that inhomogeneous fluid motion gave rise to viscous force while the selection of observers on different space-time points would change such an inhomogeneous character. Therefore, when the viscous force was considered as an objective existence foreign to the selection of observers, the form invariances of viscous force and momentum equation under local rotation transformation required a new dynamic field,namely the vortex field to be introduced. Then the dynamical equations of all flow fields were obtained through constructing the Lagrangian density of fluid system and using the variational approach of energy.
Amniotic fluid water dynamics.
Beall, M H; van den Wijngaard, J P H M; van Gemert, M J C; Ross, M G
2007-01-01
Water arrives in the mammalian gestation from the maternal circulation across the placenta. It then circulates between the fetal water compartments, including the fetal body compartments, the placenta and the amniotic fluid. Amniotic fluid is created by the flow of fluid from the fetal lung and bladder. A major pathway for amniotic fluid resorption is fetal swallowing; however in many cases the amounts of fluid produced and absorbed do not balance. A second resorption pathway, the intramembranous pathway (across the amnion to the fetal circulation), has been proposed to explain the maintenance of normal amniotic fluid volume. Amniotic fluid volume is thus a function both of the amount of water transferred to the gestation across the placental membrane, and the flux of water across the amnion. Membrane water flux is a function of the water permeability of the membrane; available data suggests that the amnion is the structure limiting intramembranous water flow. In the placenta, the syncytiotrophoblast is likely to be responsible for limiting water flow across the placenta. In human tissues, placental trophoblast membrane permeability increases with gestational age, suggesting a mechanism for the increased water flow necessary in late gestation. Membrane water flow can be driven by both hydrostatic and osmotic forces. Changes in both osmotic/oncotic and hydrostatic forces in the placenta my alter maternal-fetal water flow. A normal amniotic fluid volume is critical for normal fetal growth and development. The study of amniotic fluid volume regulation may yield important insights into the mechanisms used by the fetus to maintain water homeostasis. Knowledge of these mechanisms may allow novel treatments for amniotic fluid volume abnormalities with resultant improvement in clinical outcome.
Interaction Dynamics of Singular Wave Fronts
Holm, Darryl D
2013-01-01
Some of the most impressive singular wave fronts seen in Nature are the transbasin oceanic internal waves, which may be observed from the Space Shuttle as they propagate and interact with each other, for example, in the South China Sea. The characteristic feature of these strongly nonlinear wavefronts is that they reconnect when two of them collide transversely. We derive the EPDiff equation, and use it to model this phenomenon as elastic collisions between singular wave fronts (solitons) whose momentum is distributed along curves moving in the plane. Numerical methods for EPDiff based on compatible differencing algorithms (CDAs) are used for simulating these collisions among curves. The numerical results show the same nonlinear behavior of wavefront reconnections as that observed for internal waves in the South China Sea. We generalize the singular solutions of EPDiff for other applications, in computational anatomy and in imaging science, where the singular wavefronts are evolving image outlines, whose mome...
Fetal fluid and protein dynamics
Pasman, Suzanne
2010-01-01
In this thesis fetal fluid and protein dynamics are investigated to gain insight in fetal (patho-)physiology. Studies were performed in fetuses with severe anemia and/or hydrops fetalis. Measurements were performed in fetal blood or amniotic fluid, obtained before or during intrauterine transfusion.
An Introduction to Fluid Dynamics
Batchelor, G. K.
2000-02-01
First published in 1967, Professor Batchelor's classic work is still one of the foremost texts on fluid dynamics. His careful presentation of the underlying theories of fluids is still timely and applicable, even in these days of almost limitless computer power. This reissue ensures that a new generation of graduate students experiences the elegance of Professor Batchelor's writing.
Lecture notes: Astrophysical fluid dynamics
Ogilvie, Gordon I
2016-01-01
These lecture notes and example problems are based on a course given at the University of Cambridge in Part III of the Mathematical Tripos. Fluid dynamics is involved in a very wide range of astrophysical phenomena, such as the formation and internal dynamics of stars and giant planets, the workings of jets and accretion discs around stars and black holes, and the dynamics of the expanding Universe. Effects that can be important in astrophysical fluids include compressibility, self-gravitation and the dynamical influence of the magnetic field that is 'frozen in' to a highly conducting plasma. The basic models introduced and applied in this course are Newtonian gas dynamics and magnetohydrodynamics (MHD) for an ideal compressible fluid. The mathematical structure of the governing equations and the associated conservation laws are explored in some detail because of their importance for both analytical and numerical methods of solution, as well as for physical interpretation. Linear and nonlinear waves, includin...
Basic developments in fluid dynamics
Holt, Maurice
2012-01-01
Basic Developments in Fluid Dynamics, Volume 2 focuses on the developments, approaches, methodologies, reactions, and processes involved in fluid dynamics, including sea motion, wave interactions, and motion of spheres in a viscous fluid.The selection first offers information on inviscid cavity and wake flows and weak-interaction theory of ocean waves. Discussions focus on steady and unsteady cavity flows, radiation balance, theory of weak interactions in random fields, interactions between gravity waves and the atmosphere, and interactions within the ocean. The text then examines low Reynolds
Noncommutative geometry and fluid dynamics
Energy Technology Data Exchange (ETDEWEB)
Das, Praloy; Ghosh, Subir [Indian Statistical Institute, Physics and Applied Mathematics Unit, Kolkata (India)
2016-11-15
In the present paper we have developed a Non-Commutative (NC) generalization of perfect fluid model from first principles, in a Hamiltonian framework. The noncommutativity is introduced at the Lagrangian (particle) coordinate space brackets and the induced NC fluid bracket algebra for the Eulerian (fluid) field variables is derived. Together with a Hamiltonian this NC algebra generates the generalized fluid dynamics that satisfies exact local conservation laws for mass and energy, thereby maintaining mass and energy conservation. However, nontrivial NC correction terms appear in the charge and energy fluxes. Other non-relativistic spacetime symmetries of the NC fluid are also discussed in detail. This constitutes the study of kinematics and dynamics of NC fluid. In the second part we construct an extension of the Friedmann-Robertson-Walker (FRW) cosmological model based on the NC fluid dynamics presented here. We outline the way in which NC effects generate cosmological perturbations bringing about anisotropy and inhomogeneity in the model. We also derive a NC extended Friedmann equation. (orig.)
Light-Front Dynamics and the 3He Spectral Function
Pace, Emanuele; Kaptari, Leonid; Rinaldi, Matteo; Salme', Giovanni; Scopetta, Sergio
2016-01-01
Two topics are presented. The first one is a novel approach for a Poincare' covariant description of nuclear dynamics based on light-front Hamiltonian dynamics. The key quantity is the light-front spectral function, where both normalization and momentum sum rule can be satisfied at the same time. Preliminary results are discussed for an initial analysis of the role of relativity in the EMC effect in 3He. A second issue, very challenging, is considered in a non-relativistic framework, namely a distorted spin-dependent spectral function for 3He in order to take care of the final state interaction between the observed pion and the remnant in semi-inclusive deep inelastic electron scattering off polarized 3He. The generalization of the analysis within the light-front dynamics is outlined.
Jarvis, P D
2006-01-01
We present a conformal theory of a dissipationless relativistic fluid in 2 space-time dimensions. The theory carries with it a representation of the algebra of 2-$D$ area-preserving diffeomorphisms in the target space of the complex scalar potentials. A complete canonical description is given, and the central charge of the current algebra is calculated. The passage to the quantum theory is discussed in some detail; as a result of operator ordering problems, full quantization at the level of the fields is as yet an open problem.
Antarctic Ice-Shelf Front Dynamics from ICESat
Robbins, John W.; Zwally, H. Jay; Saba, Jack L.; Yi, Donghui
2012-01-01
Time variable elevation profiles from ICESat Laser Altimetry over the period 2003-2009 provide a means to quantitatively detect and track topographic features on polar ice surfaces. The results of this study provide a measure of the horizontal motion of ice-shelf fronts. We examine the time histories of elevation profiles crossing the ice fronts of the Ross, Ronne, Filchner, Riiser-Larson and Fimbul shelves. This provides a basis for estimating dynamics in two dimensions, i.e. in elevation and horizontally in the along-track direction. Ice front velocities, corrected for ground-track intersection angle, range from nearly static to 1.1 km/yr. In many examples, a decrease in elevation up to 1 m/yr near the shelf frontis also detectable. Examples of tabular calving along shelf fronts are seen in some elevation profiles and are confirmed by corresponding MODIS imagery.
DEFF Research Database (Denmark)
Rasmussen, Anders Rønne; Sørensen, Mads Peter; Gaididei, Yuri Borisovich
2011-01-01
A wave equation including nonlinear terms up to the second order for a thermoviscous Newtonian fluid is proposed. In the lossless case this equation results from an expansion to third order of the Lagrangian for the fundamental non-dissipative fluid dynamical equations. Thus it preserves...
Fluid dynamics [and gas compressors
Energy Technology Data Exchange (ETDEWEB)
Kurz, Rainer [Solar Turbines Inc. (United States)
2002-02-01
The author examines the use of computational fluid dynamics in the development of gas compressors. The background to CFD is explained including modelling the geometry and the effects of turbulence. A typical design process is briefly explained and its limitations discussed. (UK)
Fluid Dynamics and Entropic Gravity
Nagle, Ian
2016-01-01
A new entropic gravity inspired derivation of general relativity from thermodynamics is presented. This generalizes, within Einstein gravity, the "Thermodynamics of Spacetime" approach by T. Jacobson, which relies on the Raychaudhuri evolution equation. Here the rest of the first law of thermodynamics is incorporated by using the Damour-Navier-Stokes equation, known from the membrane paradigm for describing fluid dynamics on the horizon.
Computational Fluid Dynamics in Ventilation
DEFF Research Database (Denmark)
Nielsen, Peter V.; Allard, Francis; Awbi, Hazim B.;
2008-01-01
Computational Fluid Dynamics in Ventilation Design is a new title in the is a new title in the REHVA guidebook series. The guidebook is written for people who need to use and discuss results based on CFD predictions, and it gives insight into the subject for those who are not used to work with CFD...
Artificial Heart Fluid Dynamics.
Mussivand, Tofigh Varcaneh
Flow characteristics within pneumatic, pulsatile, and pusher plate prosthetic hearts were studied. The blood pumps evaluated were duplicates of pumps used for in vivo calf and for clinical implantation at the Cleveland Clinic Foundation. Human dura mater bioprosthetic, caged disk, and Bjork-Shiley tilting disk valves were employed in the pumps. Dual camera video tape and synchronized still photography were used to study flow patterns. Diffused light and a planar laser source provided illumination. The laser light was fanned into a plane with a thickness of 0.2 mm to 10 mm. Magnesium oxide and Amberlite particles were used as tracers. Aqueous-glycerol, aqueous-sucrose solutions and mineral oil were used as blood analog fluids. Inflow, outflow, drive, and afterload pressures, diaphragm motion, cardiac output, and heart rate were measured and recorded. An electrical circuit was developed to synchronize pump diaphragm motion with captured images of flow trajectories. After digitizing the trajectories, velocities, global and local turbulence, and shear stresses were obtained. Disturbed and recirculating zones were identified. Qualitative and quantitative analyses were performed using data obtained from the digitization of flow trajectories. Simultaneous turbulence and stasis were observed during most phases of the cardiac cycles in all the pumps tested. A maximum Reynold's shear stress of 2889 dynes/cm ^2 occurred at 120 beats per minute (bpm). The peak velocity was 146 cm/sec during systole. The identified regions of recirculation, low velocity and disturbed flow were shown to correlate with thrombosed areas of explanted blood pumps. The maximum calculated turbulence intensity was 106 cm/sec which occurred at 120 bpm during systole.
Electromagnetics and Fluid Dynamics
Gaitonde, Datta
1998-01-01
Previous efforts focused on developing tools for design of low observables were sustained. The final product was the maturation of a high-order accurate finite-volume based code to solve Maxwell's equations. One of the primary achievements was the development and implementation of efficient filtering techniques which enhance the robustness of high-order and optimized schemes without significant adverse impact on accuracy. This has eliminated the stability barrier which restrains the common use of high-order schemes for conservative wave propagation phenomena on curvilinear meshes. A study was performed of crossing shock interactions under conditions of increasing interaction strength and asymmetry. In the first category, the observed computed topological bifurcations were correlated with the formation of various lines of coalescence and divergence evident in experimental and computed surf-ace oil maps. ne flow structure arising from asymmetric interactions was investigated with particular emphasis on: 1) vorticity dynamics, 2) shock-structure and 3) sidewall vortex loading. Several efforts of the prior year were successfully published in archival journals. The high-order algorithms developed for CEM have been implemented into the FDL3DI CFD code are presently undergoing extensive testing. Preliminary results are highly encouraging.
Role of weighting in the dynamics of front propagation
Energy Technology Data Exchange (ETDEWEB)
Zekri, Nouredine, E-mail: zekri@univ-usto.dz [Université des Sciences et de la Technologie d' Oran Mohamed Boudiaf, Département de Physique, LEPM, BP 1505 El Mnaouer, Oran (Algeria); Khelloufi, Khadidja; Zekri, Lotfi [Université des Sciences et de la Technologie d' Oran Mohamed Boudiaf, Département de Physique, LEPM, BP 1505 El Mnaouer, Oran (Algeria); Porterie, Bernard; Kaiss, Ahmed; Clerc, Jean-Pierre [Aix-Marseille Université, CNRS, IUSTI UMR 7343, 13453, Marseille (France)
2012-07-30
Non-equilibrium front propagation in a two-dimensional network modelling wildfire propagation was studied. The model includes deterministic long-range interactions due to radiation and a time weighting procedure. Three weight-dependent propagation regimes were found: dynamical, static, and non-propagative. The dynamical regime shows saturation for small weight values and a percolation transition area depending on the weight and size of the interaction domain. From the scaling interface exponents, the model seems to belong to the dynamical percolation universality class. In the limit of static regime it belongs to the random deposition class. -- Highlights: ► Percolation model used includes the weighting procedure and long-range interactions (an interaction domain). The interaction strength is chosen to decrease inversely with the square distance. ► There is a weight threshold R{sub c} above which the front cannot propagate. ► At R{sub c} the percolation is static (usual percolation), and below this threshold it becomes dynamic. ► A generalized dependence of the percolation threshold on both the interaction size n{sub y} and the weight parameter R is proposed. ► A further study of the front dynamic scaling is added to this version and dynamic exponents determined.
Beaudoin, Nicolas; Koehn, Daniel; Toussaint, Renaud; Gomez-Rivas, Enrique; Bons, Paul; Chung, Peter; Martín-Martín, Juan Diego
2014-05-01
Fluid migrations are the principal agent for mineral replacement in the upper crust, leading to dramatic changes in the porosity and permeability of rocks over several kilometers. Consequently, a better understanding of the physical parameters leading to mineral replacement is required to better understand and model fluid flow and rock reservoir properties. Large-scale dolostone bodies are one of the best and most debated examples of such fluid-related mineral replacement. These formations received a lot of attention lately, and although genetic mechanics and implications for fluid volume are understood, the mechanisms controlling the formation and propagation of the dolomitization reaction front remain unclear. This contribution aims at an improvement of the knowledge about how this replacement front propagates over space and time. We study the front sharpness on hand specimen and thin section scale and what the influence of advection versus diffusion of material is on the front development. In addition, we demonstrate how preexisting heterogeneities in the host rock affect the propagation of the reaction front. The rock is normally not homogeneous but contains grain boundaries, fractures and stylolites, and such structures are important on the scale of the front width. Using Scanning Electron Microscopy and Raman Spectroscopy we characterized the reaction front chemistry and morphology in different context. Specimens of dolomitization fronts, collected from carbonate sequences of the southern Maestrat Basin, Spain and the Southwestern Scottish Highlands suggest that the front thickness is about several mm being relatively sharp. Fluid infiltrated grain boundaries and fractures forming mm-scale transition zone. We study the structure of the reaction zone in detail and discuss implications for fluid diffusion-advection models and mineral replacement. In addition we formulate a numerical model taking into account fluid flow, diffusion and advection of the mobile
Fundamentals of Geophysical Fluid Dynamics
McWilliams, James C.
2006-07-01
Earth's atmosphere and oceans exhibit complex patterns of fluid motion over a vast range of space and time scales. These patterns combine to establish the climate in response to solar radiation that is inhomogeneously absorbed by the materials comprising air, water, and land. Spontaneous, energetic variability arises from instabilities in the planetary-scale circulations, appearing in many different forms such as waves, jets, vortices, boundary layers, and turbulence. Geophysical fluid dynamics (GFD) is the science of all these types of fluid motion. This textbook is a concise and accessible introduction to GFD for intermediate to advanced students of the physics, chemistry, and/or biology of Earth's fluid environment. The book was developed from the author's many years of teaching a first-year graduate course at the University of California, Los Angeles. Readers are expected to be familiar with physics and mathematics at the level of general dynamics (mechanics) and partial differential equations. Covers the essential GFD required for atmospheric science and oceanography courses Mathematically rigorous, concise coverage of basic theory and applications to both oceans and atmospheres Author is a world expert; this book is based on the course he has taught for many years Exercises are included, with solutions available to instructors from solutions@cambridge.org
Modeling ice front Dynamics of Greenland outlet glaciers using ISSM
Morlighem, M.; Bondzio, J. H.; Seroussi, H. L.; Rignot, E. J.
2015-12-01
The recent increase in the rate of mass loss from the Greenland Ice Sheet is primarily due to the acceleration and thinning of outlet glaciers along the coast. This acceleration is a dynamic response to the retreat of calving fronts, which leads to a loss in resistive stresses. These processes need to be included in ice sheet models in order to be able to accurately reproduce current trends in mass loss, and in the long term reduce the uncertainty in the contribution of ice sheets to sea level rise. Today, the vast majority of ice sheet models that include moving boundaries are one dimensional flow line and vertical flow band models, that are not adapted to the complex geometries of Greenland outlet glaciers, as they do not accurately capture changes in lateral stresses. Here, we use the level set method to track moving boundaries within a 2D plane view model of the Ice Sheet System Model (ISSM), and investigate the sensitivity of Store Glacier, in western Greenland, to the amount of melting occurring at its calving front. We explore different calving laws and obtain the best results with a new simple calving law adapted from von Mises yield criterion. We show that the ocean circulation near the front and the amount of runoff are able to trigger ice front advance and retreat depending on the amount of melting that they produce at the calving face, but the bed topography controls the stable positions of the ice front. The modeled calving front of Store Glacier, for which we have quality bed topography and sea floor bathymetry data, is particularly stable because of the presence of a large sill at the glacier terminus. If the ice front detaches from this stabilizing sill due to larger amounts of melting at the front or due to large calving events, the glacier front starts to retreat as the bed deepens inland, until it finds another stabilizing feature in the bed topography. The new bed topography maps based on mass conservation make it possible to model more
The 3He spectral function in light-front dynamics
Directory of Open Access Journals (Sweden)
Rinaldi Matteo
2016-01-01
Full Text Available A distorted spin-dependent spectral function for 3He is considered for the extraction of the transverse-momentum dependent parton distributions in the neutron from semi-inclusive deep inelastic electron scattering off polarized 3He at finite momentum transfers, where final state interactions are taken into account. The generalization of the analysis to a Poincaré covariant framework within the light-front dynamics is outlined.
The 3He spectral function in light-front dynamics
Rinaldi, Matteo; Kaptari, Leonid; Pace, Emanuele; Salmè, Giovanni; Scopetta, Sergio
2016-01-01
A distorted spin-dependent spectral function for 3He is considered for the extraction of the transverse-momentum dependent parton distributions in the neutron from semi-inclusive deep inelastic electron scattering off polarized 3He at finite momentum transfers, where final state interactions are taken into account. The generalization of the analysis to a Poincar\\'e covariant framework within the light-front dynamics is outlined.
Lectures on Geophysical Fluid Dynamics
Samelson, Roger M.
The fluid kaleidoscope of the Earth's ocean and atmosphere churns and sparkles with jets, gyres, eddies, waves, streams, and cyclones. These vast circulations, essential elements of the physical environment that support human life, are given a special character by the Earth's rotation and by their confinement to a shallow surficial layer, thin relative to the solid Earth in roughly the same proportion as an apple skin is to an apple. Geophysical fluid dynamics exploits this special character to develop a unified theoretical approach to the physics of the ocean and atmosphere.With Lectures on Geophysical Fluid Dynamics, Rick Salmon has added an insightful and provocative volume to the handful of authoritative texts currently available on the subject. The book is intended for first-year graduate students, but advanced students and researchers also will find it useful. It is divided into seven chapters, the first four of these adapted from course lectures. The book is well written and presents a fresh and stimulating perspective that complements existing texts. It would serve equally well either as the main text for a core graduate curriculum or as a supplementary resource for students and teachers seeking new approaches to both classical and contemporary problems. A lively set of footnotes contains many references to very recent work. The printing is attractive, the binding is of high quality, and typographical errors are few.
Fluid evolution at the Variscan front in the vicinity of the Aachen thrust
Sindern, S.; Meyer, F. M.; Lögering, M. J.; Kolb, J.; Vennemann, T.; Schwarzbauer, J.
2012-01-01
Quartz-carbonate-chlorite veins were studied in borehole samples of the RWTH-1 well in Aachen. Veins formed in Devonian rocks in the footwall of the Aachen thrust during Variscan deformation and associated fluid flow. Primary fluid inclusions indicate subsolvus unmixing of a homogenous H2O-CO2-CH4-(N2)-Na-(K)-Cl fluid into a H2O-Na-(K)-Cl solution and a vapour-rich CO2-(H2O, CH4, N2) fluid. The aqueous end-member composition resembles that of metamorphic fluids of the Variscan front zone with salinities ranging from 4 to 7% NaCl equiv. and maximum homogenisation temperatures of close to 400°C. Pressure estimates indicate a burial depth between 4,500 and 8,000 m at geothermal gradients between 50 and 75°C/26 MPa, but pressure decrease to sublithostatic conditions is also indicated, probably as a consequence of fracture opening during episodic seismic activity. A second fluid system, mainly preserved in pseudo-secondary and secondary fluid inclusions, is characterised by fluid temperatures between 200 and 250°C and salinities of Aachen thrust. A second fluid influx was introduced from formation waters in the footwall of the Aachen thrust as a consequence of progressive deformation. Mixing of the cooler and lower salinity formation water with the hot metamorphic fluid during episodic fluid trapping resulted in an evolving range of physicochemical fluid inclusion characteristics.
Computational Fluid Dynamics in Combustion
Directory of Open Access Journals (Sweden)
P. J. Paul
2010-10-01
Full Text Available Computational fluid dynamics has reached a stage where flow field in practical situation can be predicted to aid the design and to probe into the fundamental flow physics to understand and resolve the issues in fundamental fluid mechanics. The study examines the computation of reacting flows. After exploring the conservation equations for species and energy, the methods of closing the reaction rate terms in turbulent flow have been examined briefly. Two cases of computation, where combustion-flow interaction plays important role, have been discussed to illustrate the computational aspects and the physical insight that can be gained by the reacting flow computation.Defence Science Journal, 2010, 60(6, pp.577-582, DOI:http://dx.doi.org/10.14429/dsj.60.600
Fluid and Solute Fluxes from the Deformation Front to the Upper Slope at the Cascadia Margin
Berg, R. D.; Solomon, E. A.; Johnson, H. P.; Culling, D. P.; Harris, R. N.
2014-12-01
Fluid expulsion from accretionary convergent margins may be an important factor in global geochemical cycling and biogeochemical processes. However, the rates and distribution of fluid flow at these margins are not well known. To better understand these processes at the Cascadia margin, we collected 35 short (Mosquito fluid flow meter measurements along a transect from the deformation front to the upper slope offshore of the Washington coast as part of a coupled heat and fluid flow survey. We identified two active seep areas, one emergent at 1990 mbsl, and one long-lived at 1050 mbsl. At both sites we observed carbonate deposits several meters thick and hundreds of meters in horizontal dimension. Thermogenic hydrocarbons measured in pore waters at the long-lived seep site indicate deeply-sourced fluids originating at >80oC, likely migrating along faults. In addition, pore water solute profiles from the emergent seep site suggest active shallow circulation in the upper sediment column, with implications for the seep biological community and fluid budget of the margin. Pore fluid advection rates along the transect are used to characterize the geographic distribution and geologic controls on active fluid pathways. Pore water solute profiles from the sediment cores are integrated with the measured fluid advection rates to calculate solute fluxes out of the margin. Our transect of fluid flow and pore water chemistry measurements from the Cascadia margin will help to better understand fluid and geochemical cycling at accretionary convergent margins.
Dynamics of Complex Fluid-Fluid Interfaces
Sagis, L.M.C.
2016-01-01
This chapter presents an overview of recent progress in modelling the behaviour of complex fluid–fluid interfaces with non-equilibrium thermodynamics. We will limit ourselves to frameworks employing the Gibbs dividing surface model, and start with a general discussion of the surface excess variables
Molecular dynamics simulation of the burning front propagation in PETN
Yanilkin, A. V.; Sergeev, O. V.
2014-05-01
One of the models of detonation development in condensed explosives under shock loading is the concept of "hot spots." According to this model, the reaction initially starts at various defects and inhomogeneities, where energy is localized during shock wave propagation. In such a region the reaction may start and the heat flux sufficient for the ignition of the adjacent layers of matter may be formed. If the reaction propagates fast enough, the merging of the burning fronts from several hot spots may lead to detonation. So there is an interest in determining the burning propagation rate from the hot spot in various conditions. In this work we investigate the propagation of plane burning front from initially heated layer in PETN single crystal using molecular dynamics method with the reactive force field (ReaxFF). The burning rate depends on the direction in crystal. The kinetics of chemical transformations is considered. The dependence of the burning front propagation rate along [100] direction on the external pressure in the pressure range from normal to 30 GPa is calculated, it is shown that it grows linearly in the considered range from 50 m/s to 320 m/s. The results are compared with the data from experiments and quantum chemical calculations.
Dynamic stabilization of Rayleigh-Taylor instability in ablation fronts
Directory of Open Access Journals (Sweden)
Piriz A.R.
2013-11-01
Full Text Available Dynamic stabilization of Rayleigh-Taylor instability in an ablation front is studied by considering the simplest possible modulations in the acceleration. Explicit analytical expressions for the instability growth rate and for the boundaries of the stability region are obtained by considering a sequence of Dirac deltas. Besides, general square waves allow for studying the effect of the driving asymmetries on the stability region as well as the optimization process. The essential role of compressibility is phenomenologically addressed in order to find the constraints it imposes on the stability region.
Fluid Dynamics and Viscosity in Strongly Correlated Fluids
Schaefer, Thomas
2014-01-01
We review the modern view of fluid dynamics as an effective low energy, long wavelength theory of many body systems at finite temperature. We introduce the notion of a nearly perfect fluid, defined by a ratio $\\eta/s$ of shear viscosity to entropy density of order $\\hbar/k_B$ or less. Nearly perfect fluids exhibit hydrodynamic behavior at all distances down to the microscopic length scale of the fluid. We summarize arguments that suggest that there is fundamental limit to fluidity, and review the current experimental situation with regard to measurements of $\\eta/s$ in strongly coupled quantum fluids.
Computational methods for fluid dynamics
Ferziger, Joel H
2002-01-01
In its 3rd revised and extended edition the book offers an overview of the techniques used to solve problems in fluid mechanics on computers and describes in detail those most often used in practice. Included are advanced methods in computational fluid dynamics, like direct and large-eddy simulation of turbulence, multigrid methods, parallel computing, moving grids, structured, block-structured and unstructured boundary-fitted grids, free surface flows. The 3rd edition contains a new section dealing with grid quality and an extended description of discretization methods. The book shows common roots and basic principles for many different methods. The book also contains a great deal of practical advice for code developers and users, it is designed to be equally useful to beginners and experts. The issues of numerical accuracy, estimation and reduction of numerical errors are dealt with in detail, with many examples. A full-feature user-friendly demo-version of a commercial CFD software has been added, which ca...
Principles of computational fluid dynamics
Wesseling, Pieter
2001-01-01
The book is aimed at graduate students, researchers, engineers and physicists involved in flow computations. An up-to-date account is given of the present state-of-the-art of numerical methods employed in computational fluid dynamics. The underlying numerical principles are treated with a fair amount of detail, using elementary mathematical analysis. Attention is given to difficulties arising from geometric complexity of the flow domain and of nonuniform structured boundary-fitted grids. Uniform accuracy and efficiency for singular perturbation problems is studied, pointing the way to accurate computation of flows at high Reynolds number. Much attention is given to stability analysis, and useful stability conditions are provided, some of them new, for many numerical schemes used in practice. Unified methods for compressible and incompressible flows are discussed. Numerical analysis of the shallow-water equations is included. The theory of hyperbolic conservation laws is treated. Godunov's order barrier and ho...
Markosyan, A H; Ebert, U
2013-01-01
The high order fluid model developed in the preceding paper is employed here to study the propagation of negative planar streamer fronts in pure nitrogen. The model consists of the balance equations for electron density, average electron velocity, average electron energy and average electron energy flux. These balance equations have been obtained as velocity moments of Boltzmann's equation and are here coupled to the Poisson equation for the space charge electric field. Here the results of simulations with the high order model, with a PIC/MC (Particle in cell/Monte Carlo) model and with the first order fluid model based on the hydrodynamic drift-diffusion approximation are presented and compared. The comparison with the MC model clearly validates our high order fluid model, thus supporting its correct theoretical derivation and numerical implementation. The results of the first order fluid model with local field approximation, as usually used for streamer discharges, show considerable deviations. Furthermore,...
Introducing fluid dynamics using dimensional analysis
DEFF Research Database (Denmark)
Jensen, Jens Højgaard
2013-01-01
Many aspects of fluid dynamics can be introduced using dimensional analysis, combined with some basic physical principles. This approach is concise and allows exploration of both the laminar and turbulent limits—including important phenomena that are not normally dealt with when fluid dynamics...
Fluid dynamics theory, computation, and numerical simulation
Pozrikidis, C
2001-01-01
Fluid Dynamics Theory, Computation, and Numerical Simulation is the only available book that extends the classical field of fluid dynamics into the realm of scientific computing in a way that is both comprehensive and accessible to the beginner The theory of fluid dynamics, and the implementation of solution procedures into numerical algorithms, are discussed hand-in-hand and with reference to computer programming This book is an accessible introduction to theoretical and computational fluid dynamics (CFD), written from a modern perspective that unifies theory and numerical practice There are several additions and subject expansions in the Second Edition of Fluid Dynamics, including new Matlab and FORTRAN codes Two distinguishing features of the discourse are solution procedures and algorithms are developed immediately after problem formulations are presented, and numerical methods are introduced on a need-to-know basis and in increasing order of difficulty Matlab codes are presented and discussed for a broad...
Fluid Dynamics Theory, Computation, and Numerical Simulation
Pozrikidis, Constantine
2009-01-01
Fluid Dynamics: Theory, Computation, and Numerical Simulation is the only available book that extends the classical field of fluid dynamics into the realm of scientific computing in a way that is both comprehensive and accessible to the beginner. The theory of fluid dynamics, and the implementation of solution procedures into numerical algorithms, are discussed hand-in-hand and with reference to computer programming. This book is an accessible introduction to theoretical and computational fluid dynamics (CFD), written from a modern perspective that unifies theory and numerical practice. There are several additions and subject expansions in the Second Edition of Fluid Dynamics, including new Matlab and FORTRAN codes. Two distinguishing features of the discourse are: solution procedures and algorithms are developed immediately after problem formulations are presented, and numerical methods are introduced on a need-to-know basis and in increasing order of difficulty. Matlab codes are presented and discussed for ...
Nonlinear Dynamics of Ionization Fronts in HII Regions
Energy Technology Data Exchange (ETDEWEB)
Mizuta, A; Kane, J O; Pound, M W; Remington, B A; Ryutov, D D; Takabe, H
2006-04-20
Hydrodynamic instability of an accelerating ionization front (IF) is investigated with 2D hydrodynamic simulations, including absorption of incident photoionizing photons, recombination in the HII region, and radiative molecular cooling. When the amplitude of the perturbation is large enough, nonlinear dynamics of the IF triggered by the separation of the IF from the cloud surface is observed. This causes the second harmonic of the imposed perturbation to appear on the cloud surfaces, whereas the perturbation in density of ablated gas in the HII region remains largely single mode. This mismatch of modes between the IF and the density perturbation in the HII region prevents the strong stabilization effect seen in the linear regime. Large growth of the perturbation caused by Rayleigh-Taylor-like instability is observed late in time.
Dynamics of wave fronts and filaments in anisotropic cardiac tissue
Dierckx, Hans J F M
2015-01-01
The heartbeat is mediated between cardiac cells by waves of electrical depolarisation. During cardiac arrhythmias, electrical activity was found to be organised in scroll waves which rotate around a dynamical filament curve. In this thesis, a curved-space approach is used to mathematically capture anisotropy of wave propagation. We derive for the first time the covariant laws of motion for traveling wave fronts and scroll wave filaments in anisotropic excitable media such as cardiac tissue. We show that locally varying anisotropy yields non-zero Riemann tensor components, which may alter the stability of scroll wave filaments. The instability of scroll wave filaments has been linked to transition from ventricular tachycardia to fibrillation.
Fluid dynamics of planetary ices
Greve, Ralf
2009-01-01
The role of water ice in the solar system is reviewed from a fluid-dynamical point of view. On Earth and Mars, water ice forms ice sheets, ice caps and glaciers at the surface, which show glacial flow under their own weight. By contrast, water ice is a major constituent of the bulk volume of the icy satellites in the outer solar system, and ice flow can occur as thermal convection. The rheology of polycrystalline aggregates of ordinary, hexagonal ice Ih is described by a power law, different forms of which are discussed. The temperature dependence of the ice viscosity follows an Arrhenius law. Therefore, the flow of ice in a planetary environment constitutes a thermo-mechanically coupled problem; its model equations are obtained by inserting the flow law and the thermodynamic material equations in the balance laws of mass, momentum and energy. As an example of gravity-driven flow, the polar caps of Mars are discussed. For the north-polar cap, large-scale flow velocities of the order of 0.1...1 mm/a are likely...
An introduction to Computational Fluid Dynamics
DEFF Research Database (Denmark)
Sørensen, Lars Schiøtt
1999-01-01
CFD is the shortname for Computational Fluid Dynamics and is a numerical method by means of which we can analyze systems containing fluids. For instance systems dealing with heat flow or smoke control systems acting when a fire occur in a building.......CFD is the shortname for Computational Fluid Dynamics and is a numerical method by means of which we can analyze systems containing fluids. For instance systems dealing with heat flow or smoke control systems acting when a fire occur in a building....
Experimental and theoretical advances in fluid dynamics
Klapp, Jaime; Fuentes, Oscar Velasco
2011-01-01
The book is comprised of lectures and selected contributions presented at the Enzo Levi and XVI Annual Meeting of the Fluid Dynamic Division of the Mexican Physical Society in 2010. It is aimed at fourth year undergraduate and graduate students, as well as scientists in the fields of physics, engineering and chemistry with an interest in fluid dynamics from the experimental and theoretical point of view. The lectures are introductory and avoid the use of complicated mathematics. The other selected contributions are also geared to fourth year undergraduate and graduate students. The fluid dynam
Introduction to mathematical fluid dynamics
Meyer, Richard E
2010-01-01
An introduction to the behavior of liquids and gases, this volume provides excellent coverage of kinematics, momentum principle, Newtonian fluid, rotating fluids, compressibility, and more. It is geared toward advanced undergraduate and graduate students of mathematics and general science, and it requires a background in calculus and vector analysis. 1971 edition.
Fluid Dynamics in an Ecological Context
Denny, Mark
2007-11-01
Fluid dynamics has long been an invaluable tool in the study of biological mechanics, helping to explain how animals swim and fly, how blood is pumped, gases are exchanged, and propagules are dispersed. The goal of understanding how the physics of fluids has affected the evolution of individual organisms provides strong impetus for teaching and learning fluid mechanics; a viable alternative to the more traditional goals of engineering. In recent years, a third alternative has arisen. The principles of fluid dynamics can be used to specify when and where individual organisms will exceed their physical capabilities, information that can in turn be used to predict species-specific survivorship in a given environment. In other words, biological fluid dynamics can be extended beyond the study of individual organisms to play an important role in our understanding of ecological dynamics. In a world where environmental change is of increasing concern, fluid dynamic aspect of ``ecomechanics'' may be of considerable practical importance. Teaching fluid mechanics in ecology will be discussed in the context of wave-swept rocky shores. Various wave theories can be used to predict the maximum water velocities and accelerations impinging on specific surf-zone plants and animals. Theories of lift, drag, and accelerational forces can then be used to predict the maximum loads imposed on these organisms, loads that can be compared to the organisms' structural limits to predict the fraction of the species that will be dislodged or damaged. Taken across relevant species, this information goes far towards explaining shoreline community dynamics. .
Hidden Symmetry of a Fluid Dynamical Model
Neves, C
2001-01-01
A connection between solutions of the relativistic d-brane system in (d+1) dimensions with the solutions of a Galileo invariant fluid in d-dimensions is by now well established. However, the physical nature of the light-cone gauge description of a relativistic membrane changes after the reduction to the fluid dynamical model since the gauge symmetry is lost. In this work we argue that the original gauge symmetry present in a relativistic d-brane system can be recovered after the reduction process to a d-dimensional fluid model. To this end we propose, without introducing Wess-Zumino fields, a gauge invariant theory of isentropic fluid dynamics and show that this symmetry corresponds to the invariance under local translation of the velocity potential in the fluid dynamics picture. We show that different but equivalent choices of the sympletic sector lead to distinct representations of the embedded gauge algebra.
Jonas, Laura; John, Timm; King, Helen E.; Geisler, Thorsten; Putnis, Andrew
2014-01-01
The pseudomorphic replacement of Carrara marble by calcium phosphates was used as a model system in order to study the influence of different fluid pathways for reaction front propagation induced by fluid-rock interaction. In this model, grain boundaries present in the rock as well as the transient
Computational fluid dynamics modeling in yarn engineering
CSIR Research Space (South Africa)
Patanaik, A
2011-07-01
Full Text Available This chapter deals with the application of computational fluid dynamics (CFD) modeling in reducing yarn hairiness during the ring spinning process and thereby “engineering” yarn with desired properties. Hairiness significantly affects the appearance...
Gay-Balmaz, François
2010-01-01
This paper is a rigorous study of the dual pair structure of the ideal fluid and the dual pair structure for the $n$-dimensional Camassa-Holm (EPDiff) equation, including the proofs of the necessary transitivity results. In the case of the ideal fluid, we show that a careful definition of the momentum maps leads naturally to central extensions of diffeomorphism groups such as the group of quantomorphisms and the Ismagilov central extension.
Viscous-elastic dynamics of power-law fluids within an elastic cylinder
Boyko, Evgeniy; Bercovici, Moran; Gat, Amir D.
2017-07-01
In a wide range of applications, microfluidic channels are implemented in soft substrates. In such configurations, where fluidic inertia and compressibility are negligible, the propagation of fluids in channels is governed by a balance between fluid viscosity and elasticity of the surrounding solid. The viscous-elastic interactions between elastic substrates and non-Newtonian fluids are particularly of interest due to the dependence of viscosity on the state of the system. In this work, we study the fluid-structure interaction dynamics between an incompressible non-Newtonian fluid and a slender linearly elastic cylinder under the creeping flow regime. Considering power-law fluids and applying the thin shell approximation for the elastic cylinder, we obtain a nonhomogeneous p-Laplacian equation governing the viscous-elastic dynamics. We present exact solutions for the pressure and deformation fields for various initial and boundary conditions for both shear-thinning and shear-thickening fluids. We show that in contrast to Stokes' problem where a compactly supported front is obtained for shear-thickening fluids, here the role of viscosity is inversed and such fronts are obtained for shear-thinning fluids. Furthermore, we demonstrate that for the case of a step in inlet pressure, the propagation rate of the front has a tn/n +1 dependence on time (t ), suggesting the ability to indirectly measure the power-law index (n ) of shear-thinning liquids through measurements of elastic deformation.
International Conference on Mathematical Fluid Dynamics
Suzuki, Yukihito
2016-01-01
This volume presents original papers ranging from an experimental study on cavitation jets to an up-to-date mathematical analysis of the Navier-Stokes equations for free boundary problems, reflecting topics featured at the International Conference on Mathematical Fluid Dynamics, Present and Future, held 11–14 November 2014 at Waseda University in Tokyo. The contributions address subjects in one- and two-phase fluid flows, including cavitation, liquid crystal flows, plasma flows, and blood flows. Written by internationally respected experts, these papers highlight the connections between mathematical, experimental, and computational fluid dynamics. The book is aimed at a wide readership in mathematics and engineering, including researchers and graduate students interested in mathematical fluid dynamics.
Body fluid dynamics: back to the future.
Bhave, Gautam; Neilson, Eric G
2011-12-01
Pioneering investigations conducted over a half century ago on tonicity, transcapillary fluid exchange, and the distribution of water and solute serve as a foundation for understanding the physiology of body fluid spaces. With passage of time, however, some of these concepts have lost their connectivity to more contemporary information. Here we examine the physical forces determining the compartmentalization of body fluid and its movement across capillary and cell membrane barriers, drawing particular attention to the interstitium operating as a dynamic interface for water and solute distribution rather than as a static reservoir. Newer work now supports an evolving model of body fluid dynamics that integrates exchangeable Na(+) stores and transcapillary dynamics with advances in interstitial matrix biology.
Modern fluid dynamics for physics and astrophysics
Regev, Oded; Yecko, Philip A
2016-01-01
This book grew out of the need to provide students with a solid introduction to modern fluid dynamics. It offers a broad grounding in the underlying principles and techniques used, with some emphasis on applications in astrophysics and planetary science. The book comprehensively covers recent developments, methods and techniques, including, for example, new ideas on transitions to turbulence (via transiently growing stable linear modes), new approaches to turbulence (which remains the enigma of fluid dynamics), and the use of asymptotic approximation methods, which can give analytical or semi-analytical results and complement fully numerical treatments. The authors also briefly discuss some important considerations to be taken into account when developing a numerical code for computer simulation of fluid flows. Although the text is populated throughout with examples and problems from the field of astrophysics and planetary science, the text is eminently suitable as a general introduction to fluid dynamics. It...
Chen, Jui-Sheng; Liu, Chen-Wuing; Lai, Geng-Xin; Ni, Chuen-Fa
2009-06-01
SummaryThe dissolution-induced finger or wormhole patterns in porous medium or fracture rock play a crucial role in a variety of scientific, industrial, and engineering practices. Although previous studies have extensively presented a number of numerical models which couples a system of nonlinear governing equations of porosity change due to mineral dissolution, the conservations of groundwater flow and transport of chemical species to investigate the morphological pattern of a chemical dissolution front within a fluid-saturated porous medium, whereas the mechanical dispersion effect has generally been neglected in the model development. This study addresses the effects of mechanical dispersion on the morphological evolution of a chemical dissolution front for a variety of cases. Mechanical dispersion processes is incorporated with the coupled nonlinear governing equation system so as to rebuild a newly numerical model. The results of numerical simulations demonstrate that mechanical dispersion has pronounced impacts on the morphological pattern of the chemical dissolution front. For single local non-uniformity case, mechanical dispersion reduces the finger length of an unstable single-fingering front or retains the shape of a stable planar front while speeding up the front advancement. In the case of two local non-uniformities, adding mechanical dispersion with different flow conditions can yield one of the following results: (1) the shape of the stable planar front is maintained but its advancement is accelerated; (2) the shape of the unstable single-fingering front is maintained but its length is reduced; (3) the unstable double-fingering front is merged into an unstable single-fingering front; and (4) the shape of the unstable double-fingering front is preserved but its fingering length is reduced. A comparison between the behavior diagrams of dissolution front morphology (with and without considering mechanical dispersion) shows that the double-fingering front
Vortex dynamics in plasmas and fluids
DEFF Research Database (Denmark)
Juul Rasmussen, J.; Lynov, Jens-Peter; Hesthaven, J.S.;
1994-01-01
The existence and dynamics of vortical structures in both homogeneous and inhomogeneous systems will be discussed. In particular the dynamics of monopolar and dipolar vortices in a plasma with nonuniform density and in a rotating fluid with varying Coriolis force is described. The role of vortical...
Emergent geometries and nonlinear-wave dynamics in photon fluids.
Marino, F; Maitland, C; Vocke, D; Ortolan, A; Faccio, D
2016-03-22
Nonlinear waves in defocusing media are investigated in the framework of the hydrodynamic description of light as a photon fluid. The observations are interpreted in terms of an emergent curved spacetime generated by the waves themselves, which fully determines their dynamics. The spacetime geometry emerges naturally as a result of the nonlinear interaction between the waves and the self-induced background flow. In particular, as observed in real fluids, different points of the wave profile propagate at different velocities leading to the self-steepening of the wave front and to the formation of a shock. This phenomenon can be associated to a curvature singularity of the emergent metric. Our analysis offers an alternative insight into the problem of shock formation and provides a demonstration of an analogue gravity model that goes beyond the kinematic level.
Seismic history matching of fluid fronts using the ensemble kalman filter
Trani, M.; Arts, R.; Leeuwenburgh, O.
2013-01-01
Time-lapse seismic data provide information on the dynamics of multiphase reservoir fluid flow in places where no production data from wells are available. This information, in principle, could be used to estimate unknown reservoir properties. However, the amount, resolution, and character of the da
Interfacial gauge methods for incompressible fluid dynamics.
Saye, Robert
2016-06-01
Designing numerical methods for incompressible fluid flow involving moving interfaces, for example, in the computational modeling of bubble dynamics, swimming organisms, or surface waves, presents challenges due to the coupling of interfacial forces with incompressibility constraints. A class of methods, denoted interfacial gauge methods, is introduced for computing solutions to the corresponding incompressible Navier-Stokes equations. These methods use a type of "gauge freedom" to reduce the numerical coupling between fluid velocity, pressure, and interface position, allowing high-order accurate numerical methods to be developed more easily. Making use of an implicit mesh discontinuous Galerkin framework, developed in tandem with this work, high-order results are demonstrated, including surface tension dynamics in which fluid velocity, pressure, and interface geometry are computed with fourth-order spatial accuracy in the maximum norm. Applications are demonstrated with two-phase fluid flow displaying fine-scaled capillary wave dynamics, rigid body fluid-structure interaction, and a fluid-jet free surface flow problem exhibiting vortex shedding induced by a type of Plateau-Rayleigh instability. The developed methods can be generalized to other types of interfacial flow and facilitate precise computation of complex fluid interface phenomena.
Viscous-elastic dynamics of power-law fluids within an elastic cylinder
Gat, Amir; Boyko, Evgeniy; Bercovici, Moran
2016-11-01
We study the fluid-structure interaction dynamics of non-Newtonian flow through a slender linearly elastic cylinder at the creeping flow regime. Specifically, considering power-law fluids and applying the thin shell approximation for the elastic cylinder, we obtain a non-homogeneous p-Laplacian equation governing the viscous-elastic dynamics. We obtain exact solutions for the pressure and deformation fields for various initial and boundary conditions, for both shear thinning and shear thickening fluids. In particular, impulse or a step in inlet pressure yield self-similar solutions, which exhibit a compactly supported propagation front solely for shear thinning fluids. Applying asymptotic expansions, we provide approximations for weakly non-Newtonian behavior showing good agreement with the exact solutions sufficiently far from the front.
Computational Fluid Dynamics in Cardiovascular Disease
Lee, Byoung-kwon
2011-01-01
Computational fluid dynamics (CFD) is a mechanical engineering field for analyzing fluid flow, heat transfer, and associated phenomena, using computer-based simulation. CFD is a widely adopted methodology for solving complex problems in many modern engineering fields. The merit of CFD is developing new and improved devices and system designs, and optimization is conducted on existing equipment through computational simulations, resulting in enhanced efficiency and lower operating costs. Howev...
Colour in visualisation for computational fluid dynamics
2006-01-01
Colour is used in computational fluid dynamic (CFD) simulations in two key ways. First it is used to visualise the geometry and allow the engineers to be confident that the model constructed is a good representation of the engineering situation. Once an analysis has been completed, colour is used in post-processing the data from the simulations to illustrate the complex fluid mechanic phenomena under investigation. This paper describes these two uses of colour and provides some examples to il...
Fluid dynamics theory, computation, and numerical simulation
Pozrikidis, C
2017-01-01
This book provides an accessible introduction to the basic theory of fluid mechanics and computational fluid dynamics (CFD) from a modern perspective that unifies theory and numerical computation. Methods of scientific computing are introduced alongside with theoretical analysis and MATLAB® codes are presented and discussed for a broad range of topics: from interfacial shapes in hydrostatics, to vortex dynamics, to viscous flow, to turbulent flow, to panel methods for flow past airfoils. The third edition includes new topics, additional examples, solved and unsolved problems, and revised images. It adds more computational algorithms and MATLAB programs. It also incorporates discussion of the latest version of the fluid dynamics software library FDLIB, which is freely available online. FDLIB offers an extensive range of computer codes that demonstrate the implementation of elementary and advanced algorithms and provide an invaluable resource for research, teaching, classroom instruction, and self-study. This ...
Variational principles for stochastic fluid dynamics.
Holm, Darryl D
2015-04-08
This paper derives stochastic partial differential equations (SPDEs) for fluid dynamics from a stochastic variational principle (SVP). The paper proceeds by taking variations in the SVP to derive stochastic Stratonovich fluid equations; writing their Itô representation; and then investigating the properties of these stochastic fluid models in comparison with each other, and with the corresponding deterministic fluid models. The circulation properties of the stochastic Stratonovich fluid equations are found to closely mimic those of the deterministic ideal fluid models. As with deterministic ideal flows, motion along the stochastic Stratonovich paths also preserves the helicity of the vortex field lines in incompressible stochastic flows. However, these Stratonovich properties are not apparent in the equivalent Itô representation, because they are disguised by the quadratic covariation drift term arising in the Stratonovich to Itô transformation. This term is a geometric generalization of the quadratic covariation drift term already found for scalar densities in Stratonovich's famous 1966 paper. The paper also derives motion equations for two examples of stochastic geophysical fluid dynamics; namely, the Euler-Boussinesq and quasi-geostropic approximations.
Relativistic fluid dynamics in heavy ion collisions
Pu, Shi
2011-01-01
This dissertation is about the study of three important issues in the theory of relativistic fluid dynamics: the stability of dissipative fluid dynamics, the shear viscosity, and fluid dynamics with triangle anomaly.(1)The second order theory of fluid dynamics is necessary for causality. However the causality cannot be guaranteed for all parameters. The constraints for parameters are then given. We also point out that the causality and the stability are inter-correlated. It is found that a causal system must be stable, but an acausal system in the boost frame at high speed must be unstable. (2)The transport coefficients can be determined in kinetic theory. We will firstly discuss about derivation of the shear viscosity via variational method in the Boltzmann equation. Secondly, we will compute the shear viscosity via AdS/CFT duality in a Bjorken boost invariant fluid with radial flow. It is found that the ratio of the shear viscosity to entropy density is consistent with the work of Policastro, Son and Starin...
Reduced MHD and Astrophysical Fluid Dynamics
Arter, Wayne
2011-08-01
Recent work has shown a relationship between between the equations of Reduced Magnetohydrodynamics (RMHD), used to model magnetic fusion laboratory experiments, and incompressible magnetoconvection (IMC), employed in the simulation of astrophysical fluid dynamics (AFD), which means that the two systems are mathematically equivalent in certain geometries. Limitations on the modelling of RMHD, which were found over twenty years ago, are reviewed for an AFD audience, together with hitherto unpublished material on the role of finite-time singularities in the discrete equations used to model fluid dynamical systems. Possible implications for turbulence modelling are mentioned.
Introduction to Computational Fluid Dynamics
Date, Anil W.
2005-08-01
This is a textbook for advanced undergraduate and first-year graduate students in mechanical, aerospace, and chemical engineering. The book emphasizes understanding CFD through physical principles and examples. The author follows a consistent philosophy of control volume formulation of the fundamental laws of fluid motion and energy transfer, and introduces a novel notion of 'smoothing pressure correction' for solution of flow equations on collocated grids within the framework of the well-known SIMPLE algorithm. The subject matter is developed by considering pure conduction/diffusion, convective transport in 2-dimensional boundary layers and in fully elliptic flow situations and phase-change problems in succession. The book includes chapters on discretization of equations for transport of mass, momentum and energy on Cartesian, structured curvilinear and unstructured meshes, solution of discretised equations, numerical grid generation and convergence enhancement. Practicing engineers will find this particularly useful for reference and for continuing education.
Three-Dimensional Dynamical Instabilities in Galactic Ionization Fronts
Whalen, D J; Whalen, Daniel J.; Norman, Michael L.
2007-01-01
Ionization front instabilities have long been of interest for their suspected role in a variety of phenomena in the galaxy, from the formation of bright rims and 'elephant trunks' in nebulae to triggered star formation in molecular clouds. Numerical treatments of these instabilities have historically been limited in both dimensionality and input physics, leaving important questions about their true evolution unanswered. We present the first three-dimensional radiation hydrodynamical calculations of both R-type and D-type ionization front instabilities in galactic environments (i.e., solar metallicity gas). Consistent with linear stability analyses of planar D-type fronts, our models exhibit many short-wavelength perturbations growing at early times that later evolve into fewer large-wavelength structures. The simulations demonstrate that both self-consistent radiative transfer and three-dimensional flow introduce significant morphological differences to unstable modes when compared to earlier two-dimensional ...
Fluid Dynamic Verification Experiments on STS-70
Kleis, Stanley J.
1996-01-01
Fluid dynamic experiments were flown on STS-70 as phase two of the engineering evaluation of the first bioreactor Engineering Development Unit (EDU#1). The phase one experiments were comparative cell cultures in identical units on earth and onboard STS-70. In phase two, two types of fluid dynamic experiments were performed. Qualitative comparisons of the basic flow patterns were evaluated with the use of 'dye' streaklines formed from alternate injections of either a mild acid or base solution into the external flow loop that was then perfused into the vessel. The presence of Bromothymol Blue in the fluid then caused color changes from yellow to blue or vice versa, indicating the basic fluid motions. This reversible change could be repeated as desired. In the absence of significant density differences in the fluid, the flow patterns in space should be the same as on earth. Video tape records of the flow patterns for a wide range of operating conditions were obtained. The second type of fluid dynamic experiment was the quantitative evaluation of the trajectories of solid beads of various densities and sizes. The beads were introduced into the vessel and the paths recorded on video tape, with the vessel operated at various rotation rates and flow perfusion rates. Because of space limitations, the video camera was placed as close as possible to the vessel, resulting in significant optical distortion. This report describes the analysis methods to obtain comparisons between the in-flight fluid dynamics and numerical models of the flow field. The methods include optical corrections to the video images and calculation of the bead trajectories for given operating conditions and initial bead locations.
Tundisi, J G; Matsumura-Tundisi, T; Pereira, K C; Luzia, A P; Passerini, M D; Chiba, W A C; Morais, M A; Sebastien, N Y
2010-10-01
In this paper the authors discuss the effects of cold fronts on the dynamics of freshwater ecosystems of southeast South America. Cold fronts originating from the Antarctic show a monthly frequency that promotes turbulence and vertical mixing in reservoirs with a consequence to homogenize nutrient distribution, dissolved oxygen and temperature. Weak thermoclines and the athelomixis process immediately before, during and after the passage of cold fronts interfere with phytoplankton succession in reservoirs. Cyanobacteria blooms in eutrophic reservoirs are frequently connected with periods of stratification and stability of the water column. Cold fronts in the Amazon and Pantanal lakes may produce fish killings during the process of "friagem" associated mixing events. Further studies will try to implement a model to predict the impact of cold fronts and prepare management procedures in order to cope with cyanobacteria blooms during warm and stable water column periods. Changes in water quality of reservoirs are expected during circulation periods caused by cold fronts.
The Fluid Dynamics of Competitive Swimming
Wei, Timothy; Mark, Russell; Hutchison, Sean
2014-01-01
Nowhere in sport is performance so dependent on the interaction of the athlete with the surrounding medium than in competitive swimming. As a result, understanding (at least implicitly) and controlling (explicitly) the fluid dynamics of swimming are essential to earning a spot on the medal stand. This is an extremely complex, highly multidisciplinary problem with a broad spectrum of research approaches. This review attempts to provide a historical framework for the fluid dynamics-related aspects of human swimming research, principally conducted roughly over the past five decades, with an emphasis on the past 25 years. The literature is organized below to show a continuous integration of computational and experimental technologies into the sport. Illustrations from the authors' collaborations over a 10-year period, coupling the knowledge and experience of an elite-level coach, a lead biomechanician at USA Swimming, and an experimental fluid dynamicist, are intended to bring relevance and immediacy to the review.
Fluid dynamics in porous media with Sailfish
Coelho, Rodrigo C. V.; Neumann, Rodrigo F.
2016-09-01
In this work we show the application of Sailfish to the study of fluid dynamics in porous media. Sailfish is an open-source software based on the lattice-Boltzmann method. This application of computational fluid dynamics is of particular interest to the oil and gas industry and the subject could be a starting point for an undergraduate or graduate student in physics or engineering. We built artificial samples of porous media with different porosities and used Sailfish to simulate the fluid flow through them in order to calculate their permeability and tortuosity. We also present a simple way to obtain the specific superficial area of porous media using Python libraries. To contextualise these concepts, we analyse the applicability of the Kozeny-Carman equation, which is a well-known permeability-porosity relation, to our artificial samples.
Fluid dynamics in porous media with Sailfish
Coelho, Rodrigo C V
2016-01-01
In this work we show the application of Sailfish to the study of fluid dynamics in porous media. Sailfish is an open-source software based on the lattice-Boltzmann method. This application of computational fluid dynamics is of particular interest to the oil and gas industry and the subject could be a starting point for an undergraduate or graduate student in physics or engineering. We built artificial samples of porous media with different porosities and used Sailfish to simulate the fluid flow through in order to calculate permeability and tortuosity. We also present a simple way to obtain the specific superficial area of porous media using Python libraries. To contextualize these concepts, we test the Kozeny--Carman equation, discuss its validity and calculate the Kozeny's constant for our artificial samples.
Influence of Marangoni flows on the dynamics of isothermal A + B → C reaction fronts
Tiani, R.; Rongy, L.
2016-09-01
The nonlinear dynamics of A + B → C fronts is analyzed both numerically and theoretically in the presence of Marangoni flows, i.e., convective motions driven by surface tension gradients. We consider horizontal aqueous solutions where the three species A, B, and C can affect the surface tension of the solution, thereby driving Marangoni flows. The resulting dynamics is studied by numerically integrating the incompressible Navier-Stokes equations coupled to reaction-diffusion-convection (RDC) equations for the three chemical species. We show that the dynamics of the front cannot be predicted solely on the basis of the one-dimensional reaction-diffusion profiles as is the case for buoyancy-driven convection around such fronts. We relate this observation to the structure of Marangoni flows which lead to more complex and exotic dynamics. We find in particular the surprising possibility of a reversal of the front propagation direction in time for some sets of Marangoni numbers, quantifying the influence of each chemical species concentration on the solution surface tension. We explain this reversal analytically and propose a new classification of the convective effects on A + B → C reaction fronts as a function of the Marangoni numbers. The influence of the layer thickness on the RDC dynamics is also presented. Those results emphasize the importance of flow symmetry properties when studying convective front dynamics in a given geometry.
Computational fluid dynamics in oil burner design
Energy Technology Data Exchange (ETDEWEB)
Butcher, T.A. [Brookhaven National Labs., Upton, NY (United States)
1997-09-01
In Computational Fluid Dynamics, the differential equations which describe flow, heat transfer, and mass transfer are approximately solved using a very laborious numerical procedure. Flows of practical interest to burner designs are always turbulent, adding to the complexity of requiring a turbulence model. This paper presents a model for burner design.
Syringe irrigation: blending endodontics and fluid dynamics
C. Boutsioukis; L.W.M. van der Sluis
2015-01-01
Syringe irrigation remains a widely used irrigant delivery method during root canal treatment. An interdisciplinary approach involving well-established methods from the field of fluid dynamics can provide new insights into the mechanisms involved in cleaning and disinfection of the root canal system
Engineering applications of computational fluid dynamics
Awang, Mokhtar
2015-01-01
This volume presents the results of Computational Fluid Dynamics (CFD) analysis that can be used for conceptual studies of product design, detail product development, process troubleshooting. It demonstrates the benefit of CFD modeling as a cost saving, timely, safe and easy to scale-up methodology.
Syringe irrigation: blending endodontics and fluid dynamics
Boutsioukis, C.; van der Sluis, L.W.M.; Basrani, B.
2015-01-01
Syringe irrigation remains a widely used irrigant delivery method during root canal treatment. An interdisciplinary approach involving well-established methods from the field of fluid dynamics can provide new insights into the mechanisms involved in cleaning and disinfection of the root canal system
Modern Fluid Dynamics Intermediate Theory and Applications
Kleinstreuer, Clement
2010-01-01
Features pedagogical elements that include consistent 50/50 physics-mathematics approach when introducing material, illustrating concepts, showing flow visualizations, and solving problems. This title intends to help serious undergraduate student solve basic fluid dynamics problems independently, and suggest system design improvements
Computational Fluid Dynamics in Ventilation Design
DEFF Research Database (Denmark)
Nielsen, Peter V.
2008-01-01
This paper is based on the new REHVA Guidebook Computational Fluid Dynamics in Ventilation Design (Nielsen et al. 2007) written by Peter V. Nielsen, Francis(Nielsen 2007) written by Peter V. Nielsen, Francis Allard, Hazim B. Awbi, Lars Davidson and Alois Schälin. The guidebook is made for people...
Computational Fluid Dynamics and Ventilation Airflow
DEFF Research Database (Denmark)
Nielsen, Peter Vilhelm
2014-01-01
Computational fluid dynamics (CFD) was first introduced in the ventilation industry in the 1970s. CFD has been increasingly used since then, as testified by the number of peer-reviewed articles, which was less than 10 per year in the 1990s, and which is now 60 to 70 per year. This article discusses...
Droplet breakup dynamics of weakly viscoelastic fluids
Marshall, Kristin; Walker, Travis
2016-11-01
The addition of macromolecules to solvent, even in dilute quantities, can alter a fluid's response in an extensional flow. For low-viscosity fluids, the presence of elasticity may not be apparent when measured using a standard rotational rheometer, yet it may still alter the response of a fluid when undergoing an extensional deformation, especially at small length scales where elastic effects are enhanced. Applications such as microfluidics necessitate investigating the dynamics of fluids with elastic properties that are not pronounced at large length scales. In the present work, a microfluidic cross-slot configuration is used to study the effects of elasticity on droplet breakup. Droplet breakup and the subsequent iterated-stretching - where beads form along a filament connecting two primary droplets - were observed for a variety of material and flow conditions. We present a relationship on the modes of bead formation and how and when these modes will form based on key parameters such as the properties of the outer continuous-phase fluid. The results are vital not only for simulating the droplet breakup of weakly viscoelastic fluids but also for understanding how the droplet breakup event can be used for characterizing the extensional properties of weakly-viscoelastic fluids.
High Dynamic Range Cognitive Radio Front Ends: Architecture to Evaluation
Ashok, Arun; Subbiah, Iyappan; Varga, Gabor; Schrey, Moritz; Heinen, Stefan
2016-07-01
Advent of TV white space digitization has released frequencies from 470 MHz to 790 MHz to be utilized opportunistically. The secondary user can utilize these so called TV spaces in the absence of primary users. The most important challenge for this coexistence is mutual interference. While the strong TV stations can completely saturate the receiver of the cognitive radio (CR), the cognitive radio spurious tones can disturb other primary users and white space devices. The aim of this paper is to address the challenges for enabling cognitive radio applications in WLAN and LTE. In this process, architectural considerations for the design of cognitive radio front ends are discussed. With high-IF converters, faster and flexible implementation of CR enabled WLAN and LTE are shown. The effectiveness of the architecture is shown by evaluating the CR front ends for compliance of standards namely 802.11b/g (WLAN) and 3GPP TS 36.101 (LTE).
Three-Dimensional Dynamical Instabilities in Galactic Ionization Fronts
Whalen, Daniel J.; Norman, Michael L.
2008-01-01
Ionization front instabilities have long been of interest for their suspected role in a variety of phenomena in the Galaxy, from the formation of bright rims and "elephant trunks" in nebulae to triggered star formation in molecular clouds. Numerical treatments of these instabilities have historically been limited in both dimensionality and input physics, leaving important questions about their true evolution unanswered. We present the first three-dimensional radiation hydrodynamical calculations of both R-type (rarefied) and D-type (dense) ionization front instabilities in Galactic environments (i.e., solar-metallicity gas). Consistent with linear stability analyses of planar D-type fronts, our models exhibit many short-wavelength perturbations that grow at early times and later evolve into fewer large-wavelength structures. The simulations demonstrate that both self-consistent radiative transfer and three-dimensional flow introduce significant morphological differences to unstable modes when compared to earlier two-dimensional approximate models. We find that the amplitude of the instabilities in the nonlinear regime is primarily determined by the efficiency of cooling within the shocked neutral shell. Strong radiative cooling leads to long, extended structures with pronounced clumping, while weaker cooling leads to saturated modes that devolve into turbulent flows. These results suggest that expanding H II regions may either promote or provide turbulent support against the formation of later generations of stars, with potential consequences for star formation rates in the Galaxy today.
Interpolation Between the Instant Form and the Front Form of Relativistic Dynamics
Ji, Chueng-Ryong
2017-03-01
The instant form and the front form of relativistic dynamics proposed by Dirac (Rev Mod Phys 21:392-399, 1949) can be linked by introducing an interpolating angle. The instant form dynamics (IFD) provides a traditional approach evolved from non-relativistic dynamics and makes a close contact with Euclidean space developing temperature-dependent quantum field theory, lattice QCD, etc. The front form dynamics, now known as the light-front dynamics (LFD), however, works strictly in Minkowski space and provides useful frameworks to study deep inelastic scattering, parton distribution functions, deeply virtual Compton scattering, generalized parton distributions, etc. We present the recent development of the interpolation between IFD and LFD and discuss ramifications from this development.
Colour in visualisation for computational fluid dynamics
Kinnear, David; Atherton, Mark; Collins, Michael; Dokhan, Jason; Karayiannis, Tassos
2006-06-01
Colour is used in computational fluid dynamic (CFD) simulations in two key ways. First it is used to visualise the geometry and allow the engineer to be confident that the model constructed is a good representation of the engineering situation. Once an analysis has been completed, colour is used in post-processing the data from the simulations to illustrate the complex fluid mechanic phenomena under investigation. This paper describes these two uses of colour and provides some examples to illustrate the key visualisation approaches used in CFD.
Modeling Tools Predict Flow in Fluid Dynamics
2010-01-01
"Because rocket engines operate under extreme temperature and pressure, they present a unique challenge to designers who must test and simulate the technology. To this end, CRAFT Tech Inc., of Pipersville, Pennsylvania, won Small Business Innovation Research (SBIR) contracts from Marshall Space Flight Center to develop software to simulate cryogenic fluid flows and related phenomena. CRAFT Tech enhanced its CRUNCH CFD (computational fluid dynamics) software to simulate phenomena in various liquid propulsion components and systems. Today, both government and industry clients in the aerospace, utilities, and petrochemical industries use the software for analyzing existing systems as well as designing new ones."
Fronts under arrest: Nonlocal boundary dynamics in biology.
McCalla, Scott G; von Brecht, James H
2016-12-01
We introduce a minimal geometric partial differential equation framework to understand pattern formation from interacting, counterpropagating fronts. Our approach concentrates on the interfaces between different states in a system, and relies on both nonlocal interactions and mean-curvature flow to track their evolution. As an illustration, we use this approach to describe a phenomenon in bacterial colony formation wherein sibling colonies can arrest each other's growth. This arrested motion leads to static separations between healthy, growing colonies. As our minimal model faithfully recovers the geometry of these competing colonies, it captures and elucidates the key leading-order mechanisms responsible for such patterned growth.
Collective dynamics of sperm in viscoelastic fluid
Tung, Chih-Kuan; Harvey, Benedict B.; Fiore, Alyssa G.; Ardon, Florencia; Suarez, Susan S.; Wu, Mingming
Collective dynamics in biology is an interesting subject for physicists, in part because of its close relations to emergent behaviors in condensed matter, such as phase separation and criticality. However, the emergence of order is often less drastic in systems composed of the living cells, sometimes due to the natural variability among individual organisms. Here, using bull sperm as a model system, we demonstrate that the cells migrate collectively in viscoelastic fluids, exhibiting behavior similar to ``flocking''. This collectiveness is greatly reduced in similarly viscous Newtonian fluids, suggesting that the cell-cell interaction is primarily a result of the elastic property or the memory effect of the fluids, instead of pure hydrodynamic interactions. Unlike bacterial swarming, this collectiveness does not require a change in phenotype of the cells; therefore, it is a better model system for physicists. Supported by NIH grant 1R01HD070038.
Structure of dynamical condensation fronts in the interstellar medium
Iwasaki, Kazunari
2012-01-01
In this paper, we investigate the structure of condensation fronts from warm diffuse gas to cold neutral medium (CNM) under the plane parallel geometry. The solutions have two parameters, the pressure of the cold neutral medium (CNM) and the mass flux across the transition front and their ranges are much wider than previous thought. First, we consider the pressure range where the three phases, the CNM, the unstable phase, and the warm neutral medium, can coexist in the pressure equilibrium. In a wide range of the mass flux, we find solutions connecting the CNM and unstable phase. Moreover, we find solutions in larger pressure range where there is only one thermal equilibrium state, or the CNM. These solutions can be realized in shock-compressed regions that is promising sites of the molecular cloud formation. We also find remarkable properties in our solutions. The heat conduction becomes less important with increasing mass flux, and the thickness of the transition layer is characterized by the cooling length...
Meshfree methods for computational fluid dynamics
Jícha M.; Čermák L.; Niedoba P.
2013-01-01
The paper deals with the convergence problem of the SPH (Smoothed Particle Hydrodynamics) meshfree method for the solution of fluid dynamics tasks. In the introductory part, fundamental aspects of mesh- free methods, their definition, computational approaches and classification are discussed. In the following part, the methods of local integral representation, where SPH belongs are analyzed and specifically the method RKPM (Reproducing Kernel Particle Method) is described. In the contribution...
Delaunay triangulation and computational fluid dynamics meshes
Posenau, Mary-Anne K.; Mount, David M.
1992-01-01
In aerospace computational fluid dynamics (CFD) calculations, the Delaunay triangulation of suitable quadrilateral meshes can lead to unsuitable triangulated meshes. Here, we present case studies which illustrate the limitations of using structured grid generation methods which produce points in a curvilinear coordinate system for subsequent triangulations for CFD applications. We discuss conditions under which meshes of quadrilateral elements may not produce a Delaunay triangulation suitable for CFD calculations, particularly with regard to high aspect ratio, skewed quadrilateral elements.
Computational fluid dynamics in ventilation design
Allard, Francis; Awbi, Hazim B; Davidson, Lars; Schälin, Alois
2007-01-01
CFD-calculations have been rapidly developed to a powerful tool for the analysis of air pollution distribution in various spaces. However, the user of CFD-calculation should be aware of the basic principles of calculations and specifically the boundary conditions. Computational Fluid Dynamics (CFD) – in Ventilation Design models is written by a working group of highly qualified international experts representing research, consulting and design.
Interfacial gauge methods for incompressible fluid dynamics
Saye, Robert
2016-01-01
Designing numerical methods for incompressible fluid flow involving moving interfaces, for example, in the computational modeling of bubble dynamics, swimming organisms, or surface waves, presents challenges due to the coupling of interfacial forces with incompressibility constraints. A class of methods, denoted interfacial gauge methods, is introduced for computing solutions to the corresponding incompressible Navier-Stokes equations. These methods use a type of “gauge freedom” to reduce the...
Statics and dynamics of fluids in nanotubes
Gouin, Henri
2013-01-01
The purpose of this article is to study the statics and dynamics of nanotubes by using the methods of continuum mechanics. The nanotube can be filled with only a liquid or a vapour phase according to the physicochemical characteristics of the wall and to the disjoining pressure associated with the liquid and vapour mother bulks of the fluid, regardless of the nature of the external mother bulk. In dynamics, flows through nanotubes can be much more important than classical Poiseuille flows. When the external mother bulk is of vapour, the flow can be a million times larger than the classical flows when slippage on wall does not exist.
Isovector meson-exchange currents in the light-front dynamics
Energy Technology Data Exchange (ETDEWEB)
Desplanques, B. [Grenoble-1 Univ., 38 (France). Inst. des Sciences Nucleaires; Karmanov, V.A. [Grenoble-1 Univ., 38 (France). Inst. des Sciences Nucleaires; Mathiot, J.F. [Division de Physique Theorique, Institut de Physique Nucleaire, F-91406 Orsay Cedex (France)
1995-07-17
In the light-front dynamics, there is no pair term that plays the role of the dominant isovector pion exchange current. This current gives rise to the large and experimentally observed contribution to the deuteron electrodisintegration cross-section near threshold for pseudo-scalar {pi}NN coupling. We show analytically that in leading 1/m order the amplitude in the light-front dynamics coincides, however, with the one given by the pair term. At high Q{sup 2}, it consists of two equal parts. One comes from extra components of the deuteron and final state relativistic wave functions. The other results from the contact NN{pi}{gamma} interaction which appears in the light-front dynamics. This provides a transparent link between relativistic and non-relativistic approaches. ((orig.)).
Wetting dynamics of a collapsing fluid hole
Bostwick, J. B.; Dijksman, J. A.; Shearer, M.
2017-01-01
The collapse dynamics of an axisymmetric fluid cavity that wets the bottom of a rotating bucket bound by vertical sidewalls are studied. Lubrication theory is applied to the governing field equations for the thin film to yield an evolution equation that captures the effect of capillary, gravitational, and centrifugal forces on this converging flow. The focus is on the quasistatic spreading regime, whereby contact-line motion is governed by a constitutive law relating the contact-angle to the contact-line speed. Surface tension forces dominate the collapse dynamics for small holes with the collapse time appearing as a power law whose exponent compares favorably to experiments in the literature. Gravity accelerates the collapse process. Volume dependence is predicted and compared with experiment. Centrifugal forces slow the collapse process and lead to complex dynamics characterized by stalled spreading behavior that separates the large and small hole asymptotic regimes.
Computational Fluid Dynamics - Applications in Manufacturing Processes
Beninati, Maria Laura; Kathol, Austin; Ziemian, Constance
2012-11-01
A new Computational Fluid Dynamics (CFD) exercise has been developed for the undergraduate introductory fluid mechanics course at Bucknell University. The goal is to develop a computational exercise that students complete which links the manufacturing processes course and the concurrent fluid mechanics course in a way that reinforces the concepts in both. In general, CFD is used as a tool to increase student understanding of the fundamentals in a virtual world. A ``learning factory,'' which is currently in development at Bucknell seeks to use the laboratory as a means to link courses that previously seemed to have little correlation at first glance. A large part of the manufacturing processes course is a project using an injection molding machine. The flow of pressurized molten polyurethane into the mold cavity can also be an example of fluid motion (a jet of liquid hitting a plate) that is applied in manufacturing. The students will run a CFD process that captures this flow using their virtual mold created with a graphics package, such as SolidWorks. The laboratory structure is currently being implemented and analyzed as a part of the ``learning factory''. Lastly, a survey taken before and after the CFD exercise demonstrate a better understanding of both the CFD and manufacturing process.
High Dynamic Range RF Front End with Noise Cancellation and Linearization for WiMAX Receivers
Directory of Open Access Journals (Sweden)
J.-M. Wu
2012-06-01
Full Text Available This research deals with verification of the high dynamic range for a heterodyne radio frequency (RF front end. A 2.6 GHz RF front end is designed and implemented in a hybrid microwave integrated circuit (HMIC for worldwide interoperability for microwave access (WiMAX receivers. The heterodyne RF front end consists of a low-noise amplifier (LNA with noise cancellation, an RF bandpass filter (BPF, a downconverter with linearization, and an intermediate frequency (IF BPF. A noise canceling technique used in the low-noise amplifier eliminates a thermal noise and then reduces the noise figure (NF of the RF front end by 0.9 dB. Use of a downconverter with diode linearizer also compensates for gain compression, which increases the input-referred third-order intercept point (IIP3 of the RF front end by 4.3 dB. The proposed method substantially increases the spurious-free dynamic range (DRf of the RF front end by 3.5 dB.
Manufacturing in space: Fluid dynamics numerical analysis
Robertson, S. J.; Nicholson, L. A.; Spradley, L. W.
1981-01-01
Natural convection in a spherical container with cooling at the center was numerically simulated using the Lockheed-developed General Interpolants Method (GIM) numerical fluid dynamic computer program. The numerical analysis was simplified by assuming axisymmetric flow in the spherical container, with the symmetry axis being a sphere diagonal parallel to the gravity vector. This axisymmetric spherical geometry was intended as an idealization of the proposed Lal/Kroes growing experiments to be performed on board Spacelab. Results were obtained for a range of Rayleigh numbers from 25 to 10,000. For a temperature difference of 10 C from the cooling sting at the center to the container surface, and a gravitional loading of 0.000001 g a computed maximum fluid velocity of about 2.4 x 0.00001 cm/sec was reached after about 250 sec. The computed velocities were found to be approximately proportional to the Rayleigh number over the range of Rayleigh numbers investigated.
Wetting dynamics of a collapsing fluid hole
Bostwick, Joshua; Dijksman, Joshua; Shearer, Michael
2016-11-01
An axisymmetric fluid cavity at the bottom of a rotating bucket bound by vertical sidewalls is studied, as it is filled in by the wetting fluid. Lubrication theory is applied to reduce the governing equations to a single evolution equation for the film thickness. In the quasi-static regime the contact-line motion is governed by a constitutive law relating the effective contact angle to the contact-line speed. The dependence of the collapse time on the initial hole size is calculated. For small holes, surface tension dominates the dynamics, leading to a universal power law that compares favorably to experiments in the literature. Further verification of the model is obtained through comparison of volume dependence with experimental results.
Topological fluid dynamics of interfacial flows
DEFF Research Database (Denmark)
Brøns, Morten
1994-01-01
The topological description of flows in the vicinity of a solid boundary, that is familiar from the aerodynamics literature, has recently been extended to the case of flow at a liquid–gas interface or a free surface by Lugt [Phys. Fluids 30, 3647 (1987)]. Lugt's work is revisited in a more general...... setting, including nonconstant curvature of the interface and gradients of surface tension, using tools of modern nonlinear dynamics. Bifurcations of the flow pattern occur at degenerate configurations. Using the theory of unfolding, this paper gives a complete description of the bifurcations that depend...... on terms up to the second order. The general theory of this paper is applied to the topology of streamlines during the breaking of a wave and to the flow below a stagnant surface film. Physics of Fluids is copyrighted by The American Institute of Physics....
Geophysical fluid dynamics: whence, whither and why?
Vallis, Geoffrey K.
2016-08-01
This article discusses the role of geophysical fluid dynamics (GFD) in understanding the natural environment, and in particular the dynamics of atmospheres and oceans on Earth and elsewhere. GFD, as usually understood, is a branch of the geosciences that deals with fluid dynamics and that, by tradition, seeks to extract the bare essence of a phenomenon, omitting detail where possible. The geosciences in general deal with complex interacting systems and in some ways resemble condensed matter physics or aspects of biology, where we seek explanations of phenomena at a higher level than simply directly calculating the interactions of all the constituent parts. That is, we try to develop theories or make simple models of the behaviour of the system as a whole. However, these days in many geophysical systems of interest, we can also obtain information for how the system behaves by almost direct numerical simulation from the governing equations. The numerical model itself then explicitly predicts the emergent phenomena-the Gulf Stream, for example-something that is still usually impossible in biology or condensed matter physics. Such simulations, as manifested, for example, in complicated general circulation models, have in some ways been extremely successful and one may reasonably now ask whether understanding a complex geophysical system is necessary for predicting it. In what follows we discuss such issues and the roles that GFD has played in the past and will play in the future.
Direct modeling for computational fluid dynamics
Xu, Kun
2015-06-01
All fluid dynamic equations are valid under their modeling scales, such as the particle mean free path and mean collision time scale of the Boltzmann equation and the hydrodynamic scale of the Navier-Stokes (NS) equations. The current computational fluid dynamics (CFD) focuses on the numerical solution of partial differential equations (PDEs), and its aim is to get the accurate solution of these governing equations. Under such a CFD practice, it is hard to develop a unified scheme that covers flow physics from kinetic to hydrodynamic scales continuously because there is no such governing equation which could make a smooth transition from the Boltzmann to the NS modeling. The study of fluid dynamics needs to go beyond the traditional numerical partial differential equations. The emerging engineering applications, such as air-vehicle design for near-space flight and flow and heat transfer in micro-devices, do require further expansion of the concept of gas dynamics to a larger domain of physical reality, rather than the traditional distinguishable governing equations. At the current stage, the non-equilibrium flow physics has not yet been well explored or clearly understood due to the lack of appropriate tools. Unfortunately, under the current numerical PDE approach, it is hard to develop such a meaningful tool due to the absence of valid PDEs. In order to construct multiscale and multiphysics simulation methods similar to the modeling process of constructing the Boltzmann or the NS governing equations, the development of a numerical algorithm should be based on the first principle of physical modeling. In this paper, instead of following the traditional numerical PDE path, we introduce direct modeling as a principle for CFD algorithm development. Since all computations are conducted in a discretized space with limited cell resolution, the flow physics to be modeled has to be done in the mesh size and time step scales. Here, the CFD is more or less a direct
Three-Dimensional Computational Fluid Dynamics
Energy Technology Data Exchange (ETDEWEB)
Haworth, D.C.; O' Rourke, P.J.; Ranganathan, R.
1998-09-01
Computational fluid dynamics (CFD) is one discipline falling under the broad heading of computer-aided engineering (CAE). CAE, together with computer-aided design (CAD) and computer-aided manufacturing (CAM), comprise a mathematical-based approach to engineering product and process design, analysis and fabrication. In this overview of CFD for the design engineer, our purposes are three-fold: (1) to define the scope of CFD and motivate its utility for engineering, (2) to provide a basic technical foundation for CFD, and (3) to convey how CFD is incorporated into engineering product and process design.
Computational fluid dynamics using CATIA created geometry
Gengler, Jeanne E.
1989-07-01
A method has been developed to link the geometry definition residing on a CAD/CAM system with a computational fluid dynamics (CFD) tool needed to evaluate aerodynamic designs and requiring the memory capacity of a supercomputer. Requirements for surfaces suitable for CFD analysis are discussed. Techniques for developing surfaces and verifying their smoothness are compared, showing the capability of the CAD/CAM system. The utilization of a CAD/CAM system to create a computational mesh is explained, and the mesh interaction with the geometry and input file preparation for the CFD analysis is discussed.
Kinematics and Fluid Dynamics of Jellyfish Maneuvering
Miller, Laura; Hoover, Alex
2014-11-01
Jellyfish propel themselves through the water through periodic contractions of their elastic bells. Some jellyfish, such as the moon jellyfish Aurelia aurita and the upside down jellyfish Cassiopea xamachana, can perform turns via asymmetric contractions of the bell. The fluid dynamics of jellyfish forward propulsion and turning is explored here by analyzing the contraction kinematics of several species and using flow visualization to quantify the resulting flow fields. The asymmetric contraction and structure of the jellyfish generates asymmetries in the starting and stopping vortices. This creates a diagonal jet and a net torque acting on the jellyfish. Results are compared to immersed boundary simulations
DYNAMICS OF RELATIVISTIC FLUID FOR COMPRESSIBLE GAS
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
In this paper the relativistic fluid dynamics for compressible gas is studied.We show that the strict convexity of the negative thermodynamical entropy preserves invariant under the Lorentz transformation if and only if the local speed of sound in this gas is strictly less than that of light in the vacuum.A symmetric form for the equations of relativistic hydrodynamics is presented,and thus the local classical solutions to these equations can be deduced.At last,the non-relativistic limits of these local cla...
Domain decomposition algorithms and computational fluid dynamics
Chan, Tony F.
1988-01-01
Some of the new domain decomposition algorithms are applied to two model problems in computational fluid dynamics: the two-dimensional convection-diffusion problem and the incompressible driven cavity flow problem. First, a brief introduction to the various approaches of domain decomposition is given, and a survey of domain decomposition preconditioners for the operator on the interface separating the subdomains is then presented. For the convection-diffusion problem, the effect of the convection term and its discretization on the performance of some of the preconditioners is discussed. For the driven cavity problem, the effectiveness of a class of boundary probe preconditioners is examined.
Light-front representation of chiral dynamics in peripheral transverse densities
Granados, C
2015-01-01
The nucleon's electromagnetic form factors are expressed in terms of the transverse densities of charge and magnetization at fixed light-front time. At peripheral transverse distances $b = O(M_\\pi^{-1})$ the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). We represent the leading-order chiral EFT results for the peripheral transverse densities as overlap integrals of chiral light-front wave functions, describing the transition of the initial nucleon to soft pion-nucleon intermediate states and back. The new representation (a) explains the parametric order of the peripheral transverse densities; (b) establishes an inequality between the spin-independent and -dependent densities; (c) exposes the role of pion orbital angular momentum in chiral dynamics; (d) reveals a large left-right asymmetry of the current in a transversely polarized nucleon and suggests a simple interpretation. The light-front representation enables a first-quantiz...
Optics and Fluid Dynamics Department annual progress report for 1995
Energy Technology Data Exchange (ETDEWEB)
Hanson, S.G.; Lading, L.; Lynov, J.P.; Skaarup, B. [eds.
1996-01-01
Research in the Optics and Fluid Dynamics Department has been performed within the following two programme areas: (1) optical diagnostics and information processing and (2) plasma and fluid dynamics. The optical activities are concentrated on optical materials, diagnostics and sensors. The plasma and fluid dynamics activities are concentrated on nonlinear dynamics in fluids, plasmas and optics as well as on plasma and fluid diagnostics. Scientific computing is an integral part of the work. The activities are supported by several EU programmes, including EURATOM, by research councils and by industry. A summary of the activities in 1995 is presented. (au) 36 ills., 166 refs.
NMR imaging of fluid dynamics in reservoir core.
Baldwin, B A; Yamanashi, W S
1988-01-01
A medical NMR imaging instrument has been modified to image water and oil in reservoir rocks by the construction of a new receiving coil. Both oil and water inside the core produced readily detectable proton NMR signals, while the rock matrix produced no signal. Because of similar T2 NMR relaxation times, the water was doped with a paramagnetic ion, Mn+2, to reduce its T2 relaxation time. This procedure enhanced the separation between the oil and water phases in the resulting images. Sequential measurements, as water imbibed into one end and oil was expelled from the other end of a core plug, produced a series of images which showed the dynamics of the fluids. For water-wet Berea Sandstone a flood front was readily observed, but some of the oil was apparently left behind in small, isolated pockets which were larger than individual pores. After several additional pore volumes of water flowed through the plug the NMR image indicated a homogeneous distribution of oil. The amount of residual oil, as determined from the ratio of NMR intensities, closely approximated the residual oil saturation of fully flooded Berea samples measured by Dean-Stark extraction. A Berea sandstone core treated to make it partially oil-wet, did not show a definitive flood front, but appeared to channel the water around the perimeter of the core plug. The relative ease with which these images were made indicates that NMR imaging can be a useful technique to follow the dynamics of oil and water through a core plug for a variety of production processes.
Dynamics of the Gay-Berne fluid
Energy Technology Data Exchange (ETDEWEB)
de Miguel, E.; Rull, L.F. (Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Sevilla, Apartado 1065, Sevilla 41080 (Spain)); Gubbins, K.E. (School of Chemical Engineering, Cornell University, Ithaca, New York 14853 (United States))
1992-03-15
Using molecular-dynamics computer simulation, we study the dynamical behavior of the isotropic and nematic phases of highly anisotropic molecular fluids. The interactions are modeled by means of the Gay-Berne potential with anisotropy parameters {kappa}=3 and {kappa}{prime}=5. The linear-velocity autocorrelation function shows no evidence of a negative region in the isotropic phase, even at the higher densities considered. The self-diffusion coefficient parallel to the molecular axis shows an anomalous increase with density as the system enters the nematic region. This enhancement in parallel diffusion is also observed in the isotropic side of the transition as a precursor effect. The molecular reorientation is discussed in the light of different theoretical models. The Debye diffusion model appears to explain the reorientational mechanism in the nematic phase. None of the models gives a satisfactory account of the reorientation process in the isotropic phase.
Computational fluid dynamics: Transition to design applications
Bradley, R. G.; Bhateley, I. C.; Howell, G. A.
1987-01-01
The development of aerospace vehicles, over the years, was an evolutionary process in which engineering progress in the aerospace community was based, generally, on prior experience and data bases obtained through wind tunnel and flight testing. Advances in the fundamental understanding of flow physics, wind tunnel and flight test capability, and mathematical insights into the governing flow equations were translated into improved air vehicle design. The modern day field of Computational Fluid Dynamics (CFD) is a continuation of the growth in analytical capability and the digital mathematics needed to solve the more rigorous form of the flow equations. Some of the technical and managerial challenges that result from rapidly developing CFD capabilites, some of the steps being taken by the Fort Worth Division of General Dynamics to meet these challenges, and some of the specific areas of application for high performance air vehicles are presented.
Bioreactor Studies and Computational Fluid Dynamics
Singh, H.; Hutmacher, D. W.
The hydrodynamic environment “created” by bioreactors for the culture of a tissue engineered construct (TEC) is known to influence cell migration, proliferation and extra cellular matrix production. However, tissue engineers have looked at bioreactors as black boxes within which TECs are cultured mainly by trial and error, as the complex relationship between the hydrodynamic environment and tissue properties remains elusive, yet is critical to the production of clinically useful tissues. It is well known in the chemical and biotechnology field that a more detailed description of fluid mechanics and nutrient transport within process equipment can be achieved via the use of computational fluid dynamics (CFD) technology. Hence, the coupling of experimental methods and computational simulations forms a synergistic relationship that can potentially yield greater and yet, more cohesive data sets for bioreactor studies. This review aims at discussing the rationale of using CFD in bioreactor studies related to tissue engineering, as fluid flow processes and phenomena have direct implications on cellular response such as migration and/or proliferation. We conclude that CFD should be seen by tissue engineers as an invaluable tool allowing us to analyze and visualize the impact of fluidic forces and stresses on cells and TECs.
How Reflected Wave Fronts Dynamically Establish Hooke's Law in a Spring
Fahy, Stephen; O'Riordan, John; O'Sullivan, Colm; Twomey, Patrick
2012-01-01
A simple benchtop experiment in which a moving cart collides with a fixed spring is described. Force-time and force-distance data recorded during the collision display the transit of compression wave fronts through the spring following impact. These data can be used by students to develop a computational model of the dynamics of this simple…
Modeling quantum fluid dynamics at nonzero temperatures
Berloff, Natalia G.; Brachet, Marc; Proukakis, Nick P.
2014-03-01
The detailed understanding of the intricate dynamics of quantum fluids, in particular in the rapidly growing subfield of quantum turbulence which elucidates the evolution of a vortex tangle in a superfluid, requires an in-depth understanding of the role of finite temperature in such systems. The Landau two-fluid model is the most successful hydrodynamical theory of superfluid helium, but by the nature of the scale separations it cannot give an adequate description of the processes involving vortex dynamics and interactions. In our contribution we introduce a framework based on a nonlinear classical-field equation that is mathematically identical to the Landau model and provides a mechanism for severing and coalescence of vortex lines, so that the questions related to the behavior of quantized vortices can be addressed self-consistently. The correct equation of state as well as nonlocality of interactions that leads to the existence of the roton minimum can also be introduced in such description. We review and apply the ideas developed for finite-temperature description of weakly interacting Bose gases as possible extensions and numerical refinements of the proposed method. We apply this method to elucidate the behavior of the vortices during expansion and contraction following the change in applied pressure. We show that at low temperatures, during the contraction of the vortex core as the negative pressure grows back to positive values, the vortex line density grows through a mechanism of vortex multiplication. This mechanism is suppressed at high temperatures.
Fundamental algorithms in computational fluid dynamics
Pulliam, Thomas H
2014-01-01
Intended as a textbook for courses in computational fluid dynamics at the senior undergraduate or graduate level, this book is a follow-up to the book Fundamentals of Computational Fluid Dynamics by the same authors, which was published in the series Scientific Computation in 2001. Whereas the earlier book concentrated on the analysis of numerical methods applied to model equations, this new book concentrates on algorithms for the numerical solution of the Euler and Navier-Stokes equations. It focuses on some classical algorithms as well as the underlying ideas based on the latest methods. A key feature of the book is the inclusion of programming exercises at the end of each chapter based on the numerical solution of the quasi-one-dimensional Euler equations and the shock-tube problem. These exercises can be included in the context of a typical course, and sample solutions are provided in each chapter, so readers can confirm that they have coded the algorithms correctly.
Pallã S-Sanz, E.; Johnston, T. M. S.; Rudnick, D. L.
2010-12-01
The three-dimensional dynamics in a shallow front are examined using density and current data from two surveys 100 km offshore of Monterey Bay, California. Survey 1 is forced by down-front winds, and both surveys have considerable cross-front density gradients and flow curvature. The maximum Rossby numbers on the dense side reached maxima of +0.60 in survey 1 and +0.45 in survey 2. Downwelling occurs in regions of confluence (frontogenesis) associated with potential vorticity (PV) change and thermal wind imbalance. Streamers of particulate matter and PV are advected southeastward by the frontal jet and downward. Nonlinear Ekman currents advect dense water over light water in the presence of down-front winds, which leads to upwelling along the front and downwelling on the light side of the front. At sites of active ageostrophic secondary circulation (ASC), induced by frontogenesis or Ekman effects, the observed cross-front ageostrophic velocity is consistent with the diagnosed vertical velocity. Furthermore, in survey 2, ageostrophic divergence may play an important role at the curved front, presumably counteracting quasi-geostrophic frontogenesis due to isopycnal confluence. Downward frictional vertical PV flux below the surface extracts PV from the pycnocline and reinforces the frontogenetic vertical PV flux. PV destruction at the surface is inferred from a low PV anomaly below the mixed layer in survey 2. Since the magnitude of the frontogenetic ASC is only twice the magnitude of Ekman suction, external forcing may have a considerable impact on the vertical heat and PV fluxes.
Automated Computational Fluid Dynamics Design With Shape Optimization Project
National Aeronautics and Space Administration — Computational fluid dynamics (CFD) is used as an analysis tool to help the designer gain greater understanding of the fluid flow phenomena involved in the...
Automated Computational Fluid Dynamics Design With Shape Optimization Project
National Aeronautics and Space Administration — Computational fluid dynamics (CFD) is used as an analysis tool to help the designer gain greater understanding of the fluid flow phenomena involved in the components...
Active Polar Two-Fluid Macroscopic Dynamics
Pleiner, Harald; Svensek, Daniel; Brand, Helmut R.
2014-03-01
We study the dynamics of systems with a polar dynamic preferred direction. Examples include the pattern-forming growth of bacteria (in a solvent, shoals of fish (moving in water currents), flocks of birds and migrating insects (flying in windy air). Because the preferred direction only exists dynamically, but not statically, the macroscopic variable of choice is the macroscopic velocity associated with the motion of the active units. We derive the macroscopic equations for such a system and discuss novel static, reversible and irreversible cross-couplings connected to this second velocity. We find a normal mode structure quite different compared to the static descriptions, as well as linear couplings between (active) flow and e.g. densities and concentrations due to the genuine two-fluid transport derivatives. On the other hand, we get, quite similar to the static case, a direct linear relation between the stress tensor and the structure tensor. This prominent ``active'' term is responsible for many active effects, meaning that our approach can describe those effects as well. In addition, we also deal with explicitly chiral systems, which are important for many active systems. In particular, we find an active flow-induced heat current specific for the dynamic chiral polar order.
Hadron spectroscopy and dynamics from light-front holography and conformal symmetry
Directory of Open Access Journals (Sweden)
de Téramond Guy F.
2014-06-01
Full Text Available To a first semiclassical approximation one can reduce the multi-parton light-front problem in QCD to an effective one-dimensional quantum field theory, which encodes the fundamental conformal symmetry of the classical QCD Lagrangian. This procedure leads to a relativistic light-front wave equation for arbitrary spin which incorporates essential spectroscopic and non-perturbative dynamical features of hadron physics. The mass scale for confinement and higher dimensional holographic mapping to AdS space are also emergent properties of this framework.
Cardiac fluid dynamics anticipates heart adaptation.
Pedrizzetti, Gianni; Martiniello, Alfonso R; Bianchi, Valter; D'Onofrio, Antonio; Caso, Pio; Tonti, Giovanni
2015-01-21
Hemodynamic forces represent an epigenetic factor during heart development and are supposed to influence the pathology of the grown heart. Cardiac blood motion is characterized by a vortical dynamics, and it is common belief that the cardiac vortex has a role in disease progressions or regression. Here we provide a preliminary demonstration about the relevance of maladaptive intra-cardiac vortex dynamics in the geometrical adaptation of the dysfunctional heart. We employed an in vivo model of patients who present a stable normal heart function in virtue of the cardiac resynchronization therapy (CRT, bi-ventricular pace-maker) and who are expected to develop left ventricle remodeling if pace-maker was switched off. Intra-ventricular fluid dynamics is analyzed by echocardiography (Echo-PIV). Under normal conditions, the flow presents a longitudinal alignment of the intraventricular hemodynamic forces. When pacing is temporarily switched off, flow forces develop a misalignment hammering onto lateral walls, despite no other electro-mechanical change is noticed. Hemodynamic forces result to be the first event that evokes a physiological activity anticipating cardiac changes and could help in the prediction of longer term heart adaptations.
Computational fluid dynamics in cardiovascular disease.
Lee, Byoung-Kwon
2011-08-01
Computational fluid dynamics (CFD) is a mechanical engineering field for analyzing fluid flow, heat transfer, and associated phenomena, using computer-based simulation. CFD is a widely adopted methodology for solving complex problems in many modern engineering fields. The merit of CFD is developing new and improved devices and system designs, and optimization is conducted on existing equipment through computational simulations, resulting in enhanced efficiency and lower operating costs. However, in the biomedical field, CFD is still emerging. The main reason why CFD in the biomedical field has lagged behind is the tremendous complexity of human body fluid behavior. Recently, CFD biomedical research is more accessible, because high performance hardware and software are easily available with advances in computer science. All CFD processes contain three main components to provide useful information, such as pre-processing, solving mathematical equations, and post-processing. Initial accurate geometric modeling and boundary conditions are essential to achieve adequate results. Medical imaging, such as ultrasound imaging, computed tomography, and magnetic resonance imaging can be used for modeling, and Doppler ultrasound, pressure wire, and non-invasive pressure measurements are used for flow velocity and pressure as a boundary condition. Many simulations and clinical results have been used to study congenital heart disease, heart failure, ventricle function, aortic disease, and carotid and intra-cranial cerebrovascular diseases. With decreasing hardware costs and rapid computing times, researchers and medical scientists may increasingly use this reliable CFD tool to deliver accurate results. A realistic, multidisciplinary approach is essential to accomplish these tasks. Indefinite collaborations between mechanical engineers and clinical and medical scientists are essential. CFD may be an important methodology to understand the pathophysiology of the development and
Fluid flow dynamics in MAS systems.
Wilhelm, Dirk; Purea, Armin; Engelke, Frank
2015-08-01
The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3mm-rotor diameter has been analyzed for spinning rates up to 67kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor.
Fluid Dynamics of Carbon Dioxide Disposal into Saline Aquifers
Energy Technology Data Exchange (ETDEWEB)
Garcia, Julio Enrique
2003-12-18
Injection of carbon dioxide (CO{sub 2}) into saline aquifers has been proposed as a means to reduce greenhouse gas emissions (geological carbon sequestration). Large-scale injection of CO{sub 2} will induce a variety of coupled physical and chemical processes, including multiphase fluid flow, fluid pressurization and changes in effective stress, solute transport, and chemical reactions between fluids and formation minerals. This work addresses some of these issues with special emphasis given to the physics of fluid flow in brine formations. An investigation of the thermophysical properties of pure carbon dioxide, water and aqueous solutions of CO{sub 2} and NaCl has been conducted. As a result, accurate representations and models for predicting the overall thermophysical behavior of the system CO{sub 2}-H{sub 2}O-NaCl are proposed and incorporated into the numerical simulator TOUGH2/ECO{sub 2}. The basic problem of CO{sub 2} injection into a radially symmetric brine aquifer is used to validate the results of TOUGH2/ECO2. The numerical simulator has been applied to more complex flow problem including the CO{sub 2} injection project at the Sleipner Vest Field in the Norwegian sector of the North Sea and the evaluation of fluid flow dynamics effects of CO{sub 2} injection into aquifers. Numerical simulation results show that the transport at Sleipner is dominated by buoyancy effects and that shale layers control vertical migration of CO{sub 2}. These results are in good qualitative agreement with time lapse surveys performed at the site. High-resolution numerical simulation experiments have been conducted to study the onset of instabilities (viscous fingering) during injection of CO{sub 2} into saline aquifers. The injection process can be classified as immiscible displacement of an aqueous phase by a less dense and less viscous gas phase. Under disposal conditions (supercritical CO{sub 2}) the viscosity of carbon dioxide can be less than the viscosity of the aqueous
Domain decomposition algorithms and computation fluid dynamics
Chan, Tony F.
1988-01-01
In the past several years, domain decomposition was a very popular topic, partly motivated by the potential of parallelization. While a large body of theory and algorithms were developed for model elliptic problems, they are only recently starting to be tested on realistic applications. The application of some of these methods to two model problems in computational fluid dynamics are investigated. Some examples are two dimensional convection-diffusion problems and the incompressible driven cavity flow problem. The construction and analysis of efficient preconditioners for the interface operator to be used in the iterative solution of the interface solution is described. For the convection-diffusion problems, the effect of the convection term and its discretization on the performance of some of the preconditioners is discussed. For the driven cavity problem, the effectiveness of a class of boundary probe preconditioners is discussed.
Artificial Intelligence In Computational Fluid Dynamics
Vogel, Alison Andrews
1991-01-01
Paper compares four first-generation artificial-intelligence (Al) software systems for computational fluid dynamics. Includes: Expert Cooling Fan Design System (EXFAN), PAN AIR Knowledge System (PAKS), grid-adaptation program MITOSIS, and Expert Zonal Grid Generation (EZGrid). Focuses on knowledge-based ("expert") software systems. Analyzes intended tasks, kinds of knowledge possessed, magnitude of effort required to codify knowledge, how quickly constructed, performances, and return on investment. On basis of comparison, concludes Al most successful when applied to well-formulated problems solved by classifying or selecting preenumerated solutions. In contrast, application of Al to poorly understood or poorly formulated problems generally results in long development time and large investment of effort, with no guarantee of success.
A modular system for computational fluid dynamics
McCarthy, D. R.; Foutch, D. W.; Shurtleff, G. E.
This paper describes the Modular System for Compuational Fluid Dynamics (MOSYS), a software facility for the construction and execution of arbitrary solution procedures on multizone, structured body-fitted grids. It focuses on the structure and capabilities of MOSYS and the philosophy underlying its design. The system offers different levels of capability depending on the objectives of the user. It enables the applications engineer to quickly apply a variety of methods to geometrically complex problems. The methods developer can implement new algorithms in a simple form, and immediately apply them to problems of both theoretical and practical interest. And for the code builder it consitutes a toolkit for fast construction of CFD codes tailored to various purposes. These capabilities are illustrated through applications to a particularly complex problem encountered in aircraft propulsion systems, namely, the analysis of a landing aircraft in reverse thrust.
Astrophysical Fluid Dynamics via Direct Statistical Simulation
Tobias, S M; Marston, J B
2010-01-01
In this paper we introduce the concept of Direct Statistical Simulation (DSS) for astrophysical flows. This technique may be appropriate for problems in astrophysical fluids where the instantaneous dynamics of the flows are of secondary importance to their statistical properties. We give examples of such problems including mixing and transport in planets, stars and disks. The method is described for a general set of evolution equations, before we consider the specific case of a spectral method optimised for problems on a spherical surface. The method is illustrated for the simplest non-trivial example of hydrodynamics and MHD on a rotating spherical surface. We then discuss possible extensions of the method both in terms of computational methods and the range of astrophysical problems that are of interest.
Lectures series in computational fluid dynamics
Thompson, Kevin W.
1987-01-01
The lecture notes cover the basic principles of computational fluid dynamics (CFD). They are oriented more toward practical applications than theory, and are intended to serve as a unified source for basic material in the CFD field as well as an introduction to more specialized topics in artificial viscosity and boundary conditions. Each chapter in the test is associated with a videotaped lecture. The basic properties of conservation laws, wave equations, and shock waves are described. The duality of the conservation law and wave representations is investigated, and shock waves are examined in some detail. Finite difference techniques are introduced for the solution of wave equations and conservation laws. Stability analysis for finite difference approximations are presented. A consistent description of artificial viscosity methods are provided. Finally, the problem of nonreflecting boundary conditions are treated.
Computational Fluid Dynamics In GARUDA Grid Environment
Roy, Chandra Bhushan
2011-01-01
GARUDA Grid developed on NKN (National Knowledge Network) network by Centre for Development of Advanced Computing (C-DAC) hubs High Performance Computing (HPC) Clusters which are geographically separated all over India. C-DAC has been associated with development of HPC infrastructure since its establishment in year 1988. The Grid infrastructure provides a secure and efficient way of accessing heterogeneous resource . Enabling scientific applications on Grid has been researched for some time now. In this regard we have successfully enabled Computational Fluid Dynamics (CFD) application which can help CFD community as a whole in effective manner to carry out computational research which requires huge compuational resource beyond once in house capability. This work is part of current on-going project Grid GARUDA funded by Department of Information Technology.
Artificial Intelligence In Computational Fluid Dynamics
Vogel, Alison Andrews
1991-01-01
Paper compares four first-generation artificial-intelligence (Al) software systems for computational fluid dynamics. Includes: Expert Cooling Fan Design System (EXFAN), PAN AIR Knowledge System (PAKS), grid-adaptation program MITOSIS, and Expert Zonal Grid Generation (EZGrid). Focuses on knowledge-based ("expert") software systems. Analyzes intended tasks, kinds of knowledge possessed, magnitude of effort required to codify knowledge, how quickly constructed, performances, and return on investment. On basis of comparison, concludes Al most successful when applied to well-formulated problems solved by classifying or selecting preenumerated solutions. In contrast, application of Al to poorly understood or poorly formulated problems generally results in long development time and large investment of effort, with no guarantee of success.
Bandopadhyay, Aditya; Méheust, Yves; Dentz, Marco
2016-01-01
Mixing fronts, where fluids of different chemical compositions mix with each other, are typically subjected to velocity gradients, ranging from the pore scale to the catchment scale due to permeability variations and flow line geometries. A common trait of these processes is that the mixing interface is strained by shear. Depending on the P\\'eclet number $Pe$, which represents the ratio of the characteristic diffusion time to the characteristic advection time, and the Damk\\"ohler number $Da$, which represents the ratio of the characteristic diffusion time to the characteristic reaction time, the local reaction rates can be strongly impacted by the dynamics of the mixing interface. This impact has been characterized mostly either in kinetics-limited or in mixing-limited conditions, that is, for either very low or very high $Da$. Here the coupling of shear flow and chemical reactivity is investigated for arbitrary Damk\\"ohler numbers, for a bimolecular reaction and an initial interface with separated reactants....
Extended Symbolic Dynamics in Bistable CML Existence and Stability of Fronts
Coutinho, R
1996-01-01
We consider a diffusive Coupled Map Lattice (CML) for which the local map is piece-wise affine and has two stable fixed points. By introducing a spatio-temporal coding, we prove the one-to-one correspondence between the set of global orbits and the set of admissible codes. This relationship is applied to the study of the (uniform) fronts' dynamics. It is shown that, for any given velocity in $[-1,1]$, there is a parameter set for which the fronts with that velocity exist and their shape is unique. The dependence of the velocity of the fronts on the local map's discontinuity is proved to be a Devil's staircase. Moreover, the linear stability of the global orbits which do not reach the discontinuity follows directly from our simple map. For the fronts, this statement is improved and as a consequence, the velocity of all the propagating interfaces is computed for any parameter. The fronts are shown to be also nonlinearly stable under some restrictions on the parameters. Actually, these restrictions follow from t...
Fluid Dynamics with Cryogenic Fluid Transfer in Space Project
National Aeronautics and Space Administration — During chilldown of cryogenic fluid tanks and lines, the interface between the liquid and vapor rapidly changes. Understanding these rapid changes is key...
Fluid Dynamics of Human Phonation and Speech
Mittal, Rajat; Erath, Byron D.; Plesniak, Michael W.
2013-01-01
This article presents a review of the fluid dynamics, flow-structure interactions, and acoustics associated with human phonation and speech. Our voice is produced through the process of phonation in the larynx, and an improved understanding of the underlying physics of this process is essential to advancing the treatment of voice disorders. Insights into the physics of phonation and speech can also contribute to improved vocal training and the development of new speech compression and synthesis schemes. This article introduces the key biomechanical features of the laryngeal physiology, reviews the basic principles of voice production, and summarizes the progress made over the past half-century in understanding the flow physics of phonation and speech. Laryngeal pathologies, which significantly enhance the complexity of phonatory dynamics, are discussed. After a thorough examination of the state of the art in computational modeling and experimental investigations of phonatory biomechanics, we present a synopsis of the pacing issues in this arena and an outlook for research in this fascinating subject.
Computational fluid dynamics applications to improve crop production systems
Computational fluid dynamics (CFD), numerical analysis and simulation tools of fluid flow processes have emerged from the development stage and become nowadays a robust design tool. It is widely used to study various transport phenomena which involve fluid flow, heat and mass transfer, providing det...
Self-Consistent Dynamic Models of Steady Ionization Fronts I. Weak-D and Weak-R Fronts
Henney, W J; Williams, R J R; Ferland, G J; Henney, William J.; Williams, Robin J. R.; Ferland, Gary J.
2005-01-01
We present a method for including steady-state gas flows in the plasma physics code Cloudy, which was previously restricted to modeling static configurations. The numerical algorithms are described in detail, together with an example application to plane-parallel ionization-bounded HII regions. As well as providing the foundation for future applications to more complex flows, we find the following specific results regarding the effect of advection upon ionization fronts in HII regions: 1. Significant direct effects of advection on the global emission properties occur only when the ionization parameter is lower than is typical for HII regions. 2. The overheating of partially ionized gas in the front is not large, even for supersonic (R-type) fronts. 3. The most significant morphological signature of advective fronts is an electron density spike that occurs at the ionization front. Observational evidence for such a spike is found in images of the Orion bar. 4. Plane-parallel, weak-D fronts are found to show at ...
Computational Fluid Dynamics of rising droplets
Energy Technology Data Exchange (ETDEWEB)
Wagner, Matthew [Lake Superior State University; Francois, Marianne M. [Los Alamos National Laboratory
2012-09-05
The main goal of this study is to perform simulations of droplet dynamics using Truchas, a LANL-developed computational fluid dynamics (CFD) software, and compare them to a computational study of Hysing et al.[IJNMF, 2009, 60:1259]. Understanding droplet dynamics is of fundamental importance in liquid-liquid extraction, a process used in the nuclear fuel cycle to separate various components. Simulations of a single droplet rising by buoyancy are conducted in two-dimensions. Multiple parametric studies are carried out to ensure the problem set-up is optimized. An Interface Smoothing Length (ISL) study and mesh resolution study are performed to verify convergence of the calculations. ISL is a parameter for the interface curvature calculation. Further, wall effects are investigated and checked against existing correlations. The ISL study found that the optimal ISL value is 2.5{Delta}x, with {Delta}x being the mesh cell spacing. The mesh resolution study found that the optimal mesh resolution is d/h=40, for d=drop diameter and h={Delta}x. In order for wall effects on terminal velocity to be insignificant, a conservative wall width of 9d or a nonconservative wall width of 7d can be used. The percentage difference between Hysing et al.[IJNMF, 2009, 60:1259] and Truchas for the velocity profiles vary from 7.9% to 9.9%. The computed droplet velocity and interface profiles are found in agreement with the study. The CFD calculations are performed on multiple cores, using LANL's Institutional High Performance Computing.
Viscous fluid dynamics in Au+Au collisions at RHIC
Chaudhuri, A K
2008-01-01
We have studied the space-time evolution of minimally viscous ($\\frac{\\eta}{s}$=0.08) QGP fluid, undergoing boost-invariant longitudinal motion and arbitrary transverse expansion. Relaxation equations for the shear stress tensor components, derived from the phenomenological Israel-Stewart's theory of dissipative relativistic fluid, are solved simultaneously with the energy-momentum conservation equations. Comparison of evolution of ideal and viscous fluid, both initialized under the similar conditions, e.g. same equilibration time, energy density and velocity profile, indicate that in viscous fluid, energy density or temperature of the fluid evolve slowly than in an ideal fluid. Transverse expansion is also more in viscous evolution. We have also studied particle production in viscous dynamics. Compared to ideal dynamics, in viscous dynamics, particle yield at high $p_T$ is increased. Elliptic flow on the other hand decreases. Minimally viscous QGP fluid, initialized at entropy density $s_{ini}$=110 $fm^{-3}$...
Strong nonlocal coupling stabilizes localized structures: an analysis based on front dynamics.
Fernandez-Oto, C; Clerc, M G; Escaff, D; Tlidi, M
2013-04-26
We investigate the effect of strong nonlocal coupling in bistable spatially extended systems by using a Lorentzian-like kernel. This effect through front interaction drastically alters the space-time dynamics of bistable systems by stabilizing localized structures in one and two dimensions, and by affecting the kinetics law governing their behavior with respect to weak nonlocal and local coupling. We derive an analytical formula for the front interaction law and show that the kinetics governing the formation of localized structures obeys a law inversely proportional to their size to some power. To illustrate this mechanism, we consider two systems, the Nagumo model describing population dynamics and nonlinear optics model describing a ring cavity filled with a left-handed material. Numerical solutions of the governing equations are in close agreement with analytical predictions.
Modeling of fluid dynamics interacting with ductile fraction propagation in high pressure pipeline
Institute of Scientific and Technical Information of China (English)
Mihaela Popescu
2009-01-01
This paper presents a computational model for the fluid dynamics in a fractured ductile pipe under high pressure. The pressure profile in front of the crack tip, which is the driving source of crack propagation, is computed using a nonlinear wave equation. The solution is coupled with a one dimensional choked flow analysis behind the crack. The simulation utilizes a high order optimized prefactored com-pact-finite volume method in space, and low dispersion and dissipation Runge-Kutta in time. As the pipe fractures the rapid depressurization take place inside the pipe and the prop-agation of the crack-induced waves strongly influences the outflow dynamics. Consistent with the experimental observa-tion, the model predicts the expansion wave inside the pipe, and the reflection and outflow of the wave. The model also helps characterize the propagation of the crack dynamics and fluid flows around the tip of the crack.
Computational fluid dynamics modelling in cardiovascular medicine.
Morris, Paul D; Narracott, Andrew; von Tengg-Kobligk, Hendrik; Silva Soto, Daniel Alejandro; Hsiao, Sarah; Lungu, Angela; Evans, Paul; Bressloff, Neil W; Lawford, Patricia V; Hose, D Rodney; Gunn, Julian P
2016-01-01
This paper reviews the methods, benefits and challenges associated with the adoption and translation of computational fluid dynamics (CFD) modelling within cardiovascular medicine. CFD, a specialist area of mathematics and a branch of fluid mechanics, is used routinely in a diverse range of safety-critical engineering systems, which increasingly is being applied to the cardiovascular system. By facilitating rapid, economical, low-risk prototyping, CFD modelling has already revolutionised research and development of devices such as stents, valve prostheses, and ventricular assist devices. Combined with cardiovascular imaging, CFD simulation enables detailed characterisation of complex physiological pressure and flow fields and the computation of metrics which cannot be directly measured, for example, wall shear stress. CFD models are now being translated into clinical tools for physicians to use across the spectrum of coronary, valvular, congenital, myocardial and peripheral vascular diseases. CFD modelling is apposite for minimally-invasive patient assessment. Patient-specific (incorporating data unique to the individual) and multi-scale (combining models of different length- and time-scales) modelling enables individualised risk prediction and virtual treatment planning. This represents a significant departure from traditional dependence upon registry-based, population-averaged data. Model integration is progressively moving towards 'digital patient' or 'virtual physiological human' representations. When combined with population-scale numerical models, these models have the potential to reduce the cost, time and risk associated with clinical trials. The adoption of CFD modelling signals a new era in cardiovascular medicine. While potentially highly beneficial, a number of academic and commercial groups are addressing the associated methodological, regulatory, education- and service-related challenges.
2D fluid simulations of interchange turbulence with ion dynamics
DEFF Research Database (Denmark)
Nielsen, Anders Henry; Madsen, Jens; Xu, G. S.
2013-01-01
In this paper we present a first principle global two-dimensional fluid model. The HESEL (Hot Edge SOL Electrostatic) model is a 2D numerical fluid code, based on interchange dynamics and includes besides electron also the ion pressure dynamic. In the limit of cold ions the model almost reduces...
Computational Fluid Dynamics Methods and Their Applications in Medical Science
Kowalewski Wojciech; Roszak Magdalena; Kołodziejczak Barbara; Ren-Kurc Anna; Bręborowicz Andrzej
2016-01-01
As defined by the National Institutes of Health: “Biomedical engineering integrates physical, chemical, mathematical, and computational sciences and engineering principles to study biology, medicine, behavior, and health”. Many issues in this area are closely related to fluid dynamics. This paper provides an overview of the basic concepts concerning Computational Fluid Dynamics and its applications in medicine.
Spinodal decomposition in multicomponent fluid mixtures: A molecular dynamics study
DEFF Research Database (Denmark)
Laradji, Mohamed; Mouritsen, Ole G.; Toxvaerd, Søren
1996-01-01
We have investigated the effect of the number p of components on the dynamics of phase separation in two-dimensional symmetric multicomponent fluids. In contrast to concentrated two-dimensional binary fluids, where the growth dynamics is controlled by the coupling of the velocity held to the orde...
Lu, Gui; Wang, Xiao-Dong; Duan, Yuan-Yuan
2016-10-01
Dynamic wetting is an important interfacial phenomenon in many industrial applications. There have been many excellent reviews of dynamic wetting, especially on super-hydrophobic surfaces with physical or chemical coatings, porous layers, hybrid micro/nano structures and biomimetic structures. This review summarizes recent research on dynamic wetting from the viewpoint of the fluids rather than the solid surfaces. The reviewed fluids range from simple Newtonian fluids to non-Newtonian fluids and complex nanofluids. The fundamental physical concepts and principles involved in dynamic wetting phenomena are also reviewed. This review focus on recent investigations of dynamic wetting by non-Newtonian fluids, including the latest experimental studies with a thorough review of the best dynamic wetting models for non-Newtonian fluids, to illustrate their successes and limitations. This paper also reports on new results on the still fledgling field of nanofluid wetting kinetics. The challenges of research on nanofluid dynamic wetting is not only due to the lack of nanoscale experimental techniques to probe the complex nanoparticle random motion, but also the lack of multiscale experimental techniques or theories to describe the effects of nanoparticle motion at the nanometer scale (10(-9) m) on the dynamic wetting taking place at the macroscopic scale (10(-3) m). This paper describes the various types of nanofluid dynamic wetting behaviors. Two nanoparticle dissipation modes, the bulk dissipation mode and the local dissipation mode, are proposed to resolve the uncertainties related to the various types of dynamic wetting mechanisms reported in the literature.
Non-metric fluid dynamics and cosmology on Finsler spacetimes
Hohmann, Manuel
2016-01-01
We generalize the kinetic theory of fluids, in which the description of fluids is based on the geodesic motion of particles, to spacetimes modeled by Finsler geometry. Our results show that Finsler spacetimes are a suitable background for fluid dynamics and that the equation of motion for a collisionless fluid is given by the Liouville equation, as it is also the case for a metric background geometry. We finally apply this model to collisionless dust and a general fluid with cosmological symmetry and derive the corresponding equations of motion. It turns out that the equation of motion for a dust fluid is a simple generalization of the well-known Euler equations.
Changes in nutrient dynamics of midcontinent greater white-fronted geese during spring migration
Pearse, Aaron T.; Alisauskas, Ray T.; Krapu, Gary L.; Cox, Robert R.
2011-01-01
Waterfowl and other migratory birds commonly store nutrients at traditional staging areas during spring for later use during migration and reproduction. We investigated nutrient-storage dynamics in the midcontinent population of greater white-fronted geese (Anser albifrons; hereafter white-fronted geese) at spring staging sites in the Rainwater Basin of Nebraska during February-April and in southern Saskatchewan during April-May, 1998 and 1999. In Nebraska, lipid content of white-fronted geese did not increase, and protein content changed little over time for most age and sex categories. In Saskatchewan, lipids increased 11.4 g/day (SE = 1.7) and protein content increased 1.6 g/day (SE = 0.6) in the sample of adult geese collected over a 3-week period. A study conducted during 1979-1980 in the Rainwater Basin reported that white-fronted geese gained 8.8-17.7 g of lipids per day during spring, differing greatly from our results 2 decades later. In addition, lipid levels were less in the 1990s compared to spring 1980 for adult geese nearing departure from staging sites in Saskatchewan. This shift in where geese acquired nutrient stores from Nebraska to more northern staging sites coincided with a decrease in availability of waste corn in Nebraska, their primary food source while staging at that stopover site, and an increase in cultivation of high-energy pulse crops in Saskatchewan. White-fronted geese exhibited flexibility in nutrient dynamics during spring migration, likely in response to landscape-level variation in food availability caused by changes in agricultural trends and practices. Maintaining a wide distribution of wetlands in the Great Plains may allow springstaging waterfowl to disperse across the region and facilitate access to high-energy foods over a larger cropland base.
Dynamics of fluid-conveying pipes: effects of velocity profiles
DEFF Research Database (Denmark)
Enz, Stephanie; Thomsen, Jon Juel
Varying velocity profiles and internal fluid loads on fluid-conveying pipes are investigated. Different geometric layouts of the fluid domain and inflow velocity profiles are considered. It is found that the variation of the velocity profiles along the bended pipe is considerable. A determination...... of the resulting fluid loads on the pipe walls is of interest e.g, for evaluating the dynamical behaviour of lightly damped structures like Coriolis flow meters....
Dynamic wetting with viscous Newtonian and non-Newtonian fluids.
Wei, Y; Rame, E; Walker, L M; Garoff, S
2009-11-18
We examine various aspects of dynamic wetting with viscous Newtonian and non-Newtonian fluids. Rather than concentrating on the mechanisms that relieve the classic contact line stress singularity, we focus on the behavior in the wedge flow near the contact line which has the dominant influence on wetting with these fluids. Our experiments show that a Newtonian polymer melt composed of highly flexible molecules exhibits dynamic wetting behavior described very well by hydrodynamic models that capture the critical properties of the Newtonian wedge flow near the contact line. We find that shear thinning has a strong impact on dynamic wetting, by reducing the drag of the solid on the fluid near the contact line, while the elasticity of a Boger fluid has a weaker impact on dynamic wetting. Finally, we find that other polymeric fluids, nominally Newtonian in rheometric measurements, exhibit deviations from Newtonian dynamic wetting behavior.
A wide dynamics neutron monitor with BF3 and logarithmic amplifier based front-end electronics
2010-01-01
In this paper a wide dynamics neutron monitor based on BF3 neutron detector is described. The detector is used in current mode, and a front-end electronics based on a logarithmic amplifier is used in order to have a measurement capability ranging over many decades. The system has been calibrated at Polytechnic of Milan, CESNEF, with an AmBe neutron source, and has been tested in a pulsed field at the PUNITA facility at JRC, Ispra. The detector has achieved a dynamics ranging ov...
Local dynamics of a randomly pinned crack front: A numerical study
Directory of Open Access Journals (Sweden)
Knut Skogstrand Gjerden
2014-11-01
Full Text Available We investigate numerically the dynamics of crack propagation along a weak plane using a model consisting of fibers connecting a soft and a hard clamp. This bottom-up model has previously been shown to contain the competition of two crack propagation mechanisms: coalescence of damage with the front on small scales and pinned elastic line motion on large scales. We investigate the dynamical scaling properties of the model, both on small and large scale. The model results compare favorable with experimental results on stable crack propagation between sintered PMMA plates.
Water Channel Facility for Fluid Dynamics Experiments
Eslam-Panah, Azar; Sabatino, Daniel
2016-11-01
This study presents the design, assembly, and verification process of the circulating water channel constructed by undergraduate students at the Penn State University at Berks. This work was significantly inspired from the closed-loop free-surface water channel at Lafayette College (Sabatino and Maharjan, 2015) and employed for experiments in fluid dynamics. The channel has a 11 ft length, 2.5 ft width, and 2 ft height glass test section with a maximum velocity of 3.3 ft/s. First, the investigation justifies the needs of a water channel in an undergraduate institute and its potential applications in the whole field of engineering. Then, the design procedures applied to find the geometry and material of some elements of the channel, especially the contraction, the test section, the inlet and end tanks, and the pump system are described. The optimization of the contraction design, including the maintenance of uniform exit flow and avoidance of flow separation, is also included. Finally, the discussion concludes by identifying the problems with the undergraduate education through this capstone project and suggesting some new investigations to improve flow quality.
Meshfree methods for computational fluid dynamics
Directory of Open Access Journals (Sweden)
Jícha M.
2013-04-01
Full Text Available The paper deals with the convergence problem of the SPH (Smoothed Particle Hydrodynamics meshfree method for the solution of fluid dynamics tasks. In the introductory part, fundamental aspects of mesh- free methods, their definition, computational approaches and classification are discussed. In the following part, the methods of local integral representation, where SPH belongs are analyzed and specifically the method RKPM (Reproducing Kernel Particle Method is described. In the contribution, also the influence of boundary conditions on the SPH approximation consistence is analyzed, which has a direct impact on the convergence of the method. A classical boundary condition in the form of virtual particles does not ensure a sufficient order of consistence near the boundary of the definition domain of the task. This problem is solved by using ghost particles as a boundary condition, which was implemented into the SPH code as part of this work. Further, several numerical aspects linked with the SPH method are described. In the concluding part, results are presented of the application of the SPH method with ghost particles to the 2D shock tube example. Also results of tests of several parameters and modifications of the SPH code are shown.
Transcapillary fluid dynamics during the menstrual cycle.
Oian, P; Tollan, A; Fadnes, H O; Noddeland, H; Maltau, J M
1987-04-01
Transcapillary fluid dynamics in the follicular and luteal phase in women without symptoms of premenstrual syndrome were studied. Interstitial colloid osmotic pressure was measured by the "wick" method and interstitial hydrostatic pressure by the "wick-in-needle" method in subcutaneous tissue on the thorax and ankle. From follicular to luteal phase, the following changes were observed: Colloid osmotic pressures were significantly reduced, both in plasma (mean 2.5 mm Hg) and in the interstitium (thorax mean 1.9 mm Hg and ankle mean 2.0 mm Hg). The interstitial hydrostatic pressures did not change. There were no significant changes in serum albumin, hemoglobin, or hematocrit. A slight, but significant, weight gain was observed (mean 0.7 kg). The reduced plasma and interstitial colloid osmotic pressures in the luteal phase may be due to water retention, but the observed reductions in colloid osmotic pressures are probably not fully explained by simple dilution. A reduction in total protein mass in the luteal phase is suggested.
Fluid dynamic effects on staphylococci bacteria biofilms
Sherman, Erica; Bayles, Kenneth; Endres, Jennifer; Wei, Timothy
2016-11-01
Staphylococcus aureus bacteria are able to form biofilms and distinctive tower structures that facilitate their ability to tolerate treatment and to spread within the human body. The formation of towers, which break off, get carried downstream and serve to initiate biofilms in other parts of the body are of particular interest here. It is known that flow conditions play a role in the development, dispersion and propagation of biofilms in general. The influence of flow on tower formation, however, is not at all understood. This work is focused on the effect of applied shear on tower development. The hypothesis being examined is that tower structures form within a specific range of shear stresses and that there is an as yet ill defined fluid dynamic phenomenon that occurs hours before a tower forms. In this study, a range of shear stresses is examined that brackets 0.6 dynes/cm2, the nominal shear stress where towers seem most likely to form. This talk will include µPTV measurements and cell density data indicating variations in flow and biofilm evolution as a function of the applied shear. Causal relations between flow and biofilm development will be discussed.
Particle Dynamics of Polydisperse Magnetorheological Fluids
Directory of Open Access Journals (Sweden)
Chiranjit Sarkar
2015-12-01
Full Text Available In the present research work, three dimensional simulations of magnetorheological fluids, containing soft magnetic polydisperse particles in silicone oil, has been presented. The computer simulation helps to visualize and analyze the formed transient microstructures. The initial positions of particle-centres were decided based on random distribution. The particle positions were updated considering magnetic, hydrodynamic and repulsions forces on each particle along with explicit time marching scheme. Finally the particle’s positions at 10 ms have been plotted. The yield behaviors of MRFXXS (small sized: 2 to 33 µm and MRFXXL (large sized: 45 to 212 µm have been estimated using particle dynamic simulations and the predicted results have been compared with the results obtained from experiments. Due to large number of particles and limitations of computer hardware, the yield behavior of MRFXXM1 i.e. mixed (2 to 212 µm sized magnetic particles could not be simulated. However, experiments were performed to investigate the yield behavior of MRFXXM1. The results show that MRFXXM1 is better than MRFXXS and MRFXXL.
Computational Fluid Dynamics in Hypersonic Aerothermodynamics
Directory of Open Access Journals (Sweden)
Krishnendu Sinha
2010-10-01
Full Text Available Hypersonic flows are characterised by high Mach number and high total enthalpy. An elevated temperature often results in thermo-chemical reactions in the gas, which p lay a major role in aerothermodynamic characterisation of high-speed aerospace vehicles. Hypersonic flows in propulsion components are usually turbulent, resulting in additional effects. Computational simulation of such flows, therefore, need to account for a range of physical phenomena. Further, the numerical challenges involved in resolving strong gradients and discontinuities add to the complexity of computational fluid dynamics (CFD simulation. In this article, physical modelling and numerical methodology-related issues involved in hypersonic flow simulation are highlighted. State-of-the-art CFD challenges are discussed in the context of two prominent applications-the flow in a scramjet inlet and the flow field around a re-entry capsule.Defence Science Journal, 2010, 60(6, pp.663-671, DOI:http://dx.doi.org/10.14429/dsj.60.604
The Thermodynamic and Dynamical Features of Double Front Structures During 21-31 July 1998 in China
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The daily 1°× 1° data of the Aviation (AVN) model, the black body temperature (TBB) data of cloud top, and cloud images by geostationary meteorological satellite (GMS) are used to identify a dew-point front near the periphery of the western Pacific subtropical high (WPSH). The results clearly demonstrate the existence of the dew-point front, and its thermodynamic and dynamic structural characteristics are analyzed in detail. The dew-point front is a transitional belt between the moist southwest monsoon flow and the dry adiabatic sinking flow near the WPSH, manifested by a large horizontal moisture gradient in the mid-lower troposphere and conjugated with the mei-yu front to form a predominant double-front structure associated with intense rainfall in the mei-yu period. The mei-yu front is located between 30°and 35°N, vertically extends from the ground level to the upper level and shifts northward. The dew-point front is to the south of the mei-yn front and lies up against the periphery of the WPSH. Generally, it is located between 850 hPa and 500 hPa. On the dew-point front side, the southwesterly prevails at the lower level and the northeasterly at the upper level; this wind distribution is different from that on the mei-yu front side. Vertical ascending motion exists between the two fronts, and there are descending motions on the north side of the mei-yu front and on the south side of the dew-point front, which form a secondary circulation. The dynamics of the double fronts also have some interesting features. At the lower level,positive vertical vorticity and obvious convergence between the two fronts are clearly identified. At the mid-lower level, negative local change of the divergence (corresponding to increasing convergence) is often embedded in the two fronts or against the mei-yu front. Most cloud clusters occur between the two fronts and propagate down stream in a wave-like manner.
Optics and Fluid Dynamics Department annual progress report for 2000
DEFF Research Database (Denmark)
Hanson, Steen Grüner; Johansen, Per Michael; Lynov, Jens-Peter;
2001-01-01
The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The department has corecompetences in: optical sensors, optical materials......, optical storage, biooptics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danishresearch councils and by industry. A summary of the activities in 2000 is presented....
Optics and Fluid Dynamics Department annual progress report for 2002
DEFF Research Database (Denmark)
Bindslev, H.; Hanson, Steen Grüner; Lynov, Jens-Peter;
2003-01-01
The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) laser systems and optical materials (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The departmenthas core competences in: optical sensors......, optical materials, optical storage, biophotonics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, includingEURATOM, by Danish research councils and by industry. A summary of the activities in 2002...
Optics and Fluid Dynamics Department annual progress report for 1999
DEFF Research Database (Denmark)
Hanson, Steen Grüner; Johansen, Per Michael; Lynov, Jens-Peter;
2000-01-01
The Optics and Fluid Dynamics Department performs basic and applied research within the three programmes: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The department has core competences in:optical sensors, optical materials, biooptics......, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by research councils and by industry. Asummary of the activities in 1999 is presented....
Body Fluid Dynamics: Back to the Future
Bhave, Gautam; Neilson, Eric G.
2011-01-01
Pioneering investigations conducted over a half century ago on tonicity, transcapillary fluid exchange, and the distribution of water and solute serve as a foundation for understanding the physiology of body fluid spaces. With passage of time, however, some of these concepts have lost their connectivity to more contemporary information. Here we examine the physical forces determining the compartmentalization of body fluid and its movement across capillary and cell membrane barriers, drawing p...
Light-front representation of chiral dynamics with Delta isobar and large-N_c relations
Granados, C
2016-01-01
Transverse densities describe the spatial distribution of electromagnetic current in the nucleon at fixed light-front time. At peripheral distances b = O(M_pi^{-1}) the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). Recent work has shown that the EFT results can be represented in first-quantized form, as overlap integrals of chiral light-front wave functions describing the transition of the nucleon to soft-pion-nucleon intermediate states, resulting in a quantum-mechanical picture of the peripheral transverse densities. We now extend this representation to include intermediate states with Delta isobars and implement relations based on the large-N_c limit of QCD. We derive the wave function overlap formulas for the Delta contributions to the peripheral transverse densities by way of a three-dimensional reduction of relativistic chiral EFT expressions. Our procedure effectively maintains rotational invariance and avoids the ambiguit...
Fajardo-Ortiz, David; Duran, Luis; Dumontier, Michel; Lara, Miguel; Ochoa, Hector; Castano, Victor M
2016-01-01
In this paper, we have identified and analyzed the emergence, structure and dynamics of the paradigmatic research fronts that established the fundamentals of the biomedical knowledge on HIV/AIDS. A search of papers with the identifiers "HIV/AIDS", "Human Immunodeficiency Virus" and "Acquired Immunodeficiency Syndrome" in the Web of Science (Thomson Reuters), was carried out. A citation network of those papers was constructed. Then, a sub-network of the papers with the highest number of inter-citations (with a minimal in-degree of 30) was selected to perform a combination of network clustering and text mining to identify the paradigmatic research fronts and analyze their dynamics. Seven research fronts were identified in this sub-network. Each one of the fronts are related to one of the following topics: "preliminary pathology research", "virus entry", "virus tropism", "drug resistance", "genetic expression", "assembly", and "virus replication". The emergence of these fronts occurred in successive "waves" over...
Effect of intrinsic angular momentum in the capillary filling dynamics of viscous fluids.
Gheshlaghi, Behnam; Nazaripoor, Hadi; Kumar, Aloke; Sadrzadeh, Mohtada
2016-10-01
In this study, an analytical model is provided to describe the filling dynamics of a capillary filled with a viscous fluid containing spinning particles. The aim is to demonstrate the effect of angular momentum on the capillary filling dynamics of molecular fluids which has not been explored before. The presence of spinning particles generates additional coefficients of viscosity, namely, spin viscosity and vortex viscosity, which couples rotational and translational movements. Three different time stages have been noticed during the capillary filling phenomenon: inertia force dominated, visco-inertial, and viscous-dominated regions. The last two regions are found to be mainly affected by the spinning particles. An increase in the spin and vortex viscosities is found to increase the viscous force and thus reduce the front position of the moving liquid. The results of this study are validated using the literature no-angular-momentum (NAM) base-case results and an excellent agreement is observed.
Longcope, D W
2010-01-01
In models of fast magnetic reconnection, flux transfer occurs within a small portion of a current sheet triggering stored magnetic energy to be thermalized by shocks. When the initial current sheet separates magnetic fields which are not perfectly anti-parallel, i.e. they are skewed, magnetic energy is first converted to bulk kinetic energy and then thermalized in slow magnetosonic shocks. We show that the latter resemble parallel shocks or hydrodynamic shocks for all skew angles except those very near the anti-parallel limit. As for parallel shocks, the structures of reconnection-driven slow shocks are best studied using two-fluid equations in which ions and electrons have independent temperature. Time-dependent solutions of these equations can be used to predict and understand the shocks from reconnection of skewed magnetic fields. The results differ from those found using a single-fluid model such as magnetohydrodynamics. In the two-fluid model electrons are heated indirectly and thus carry a heat flux alw...
Computational Fluid Dynamics Modeling of a Lithium/Thionyl Chloride Battery with Electrolyte Flow
Energy Technology Data Exchange (ETDEWEB)
Gu, W.B.; Jungst, Rudolph G.; Nagasubramanian, Ganesan; Wang, C.Y.; Weidner, John.
1999-06-11
A two-dimensional model is developed to simulate discharge of a lithium/thionyl chloride primary battery. The model accounts for not only transport of species and charge, but also the electrode porosity variations and the electrolyte flow induced by the volume reduction caused by electrochemical reactions. Numerical simulations are performed using a finite volume method of computational fluid dynamics. The predicted discharge curves for various temperatures are compared to the experimental data with excellent agreement. Moreover, the simulation results. in conjunction with computer visualization and animation techniques, confirm that cell utilization in the temperature and current range of interest is limited by pore plugging or clogging of the front side of the cathode as a result of LiCl precipitation. The detailed two-dimensional flow simulation also shows that the electrolyte is replenished from the cell header predominantly through the separator into the front of the cathode during most parts of the discharge, especially for higher cell temperatures.
Provata, A; Tsekouras, G A
2003-05-01
Dynamical patterns, in the form of consecutive moving stripes or rings, are shown to develop spontaneously in the cyclic lattice Lotka-Volterra model, when realized on square lattice, at the reaction limited regime. Each stripe consists of different particles (species) and the borderlines between consecutive stripes are fractal. The interface width w between the different species scales as w(L,t) approximately L(alpha)f(t/L(z)), where L is the linear size of the interface, t is the time, and alpha and z are the static and dynamical critical exponents, respectively. The critical exponents were computed as alpha=0.49+/-0.03 and z=1.53+/-0.13 and the propagating fronts show dynamical characteristics similar to those of the Eden growth models.
Dynamic Characteristics of Magneto-Fluid Supports
Directory of Open Access Journals (Sweden)
V. A. Chernobai
2008-01-01
Full Text Available The paper considers a vibro-protective magneto-fluid support that uses elastic properties of magnetic fluid with a free surface in magnetic field.The paper has experimentally revealed that the analyzed structure is characterized by better noise absorbing characteristics.The conducted experiments have made it possible to conclude that there is a possibility to use vibro-protective magneto-fluid supports within the frequency range from 0 to 300 Hz, amplitudes up to 2 mm and unit load up to 2,5 · 10 4 Н/м².
Imaging dynamical chiral-symmetry breaking: pion wave function on the light front.
Chang, Lei; Cloët, I C; Cobos-Martinez, J J; Roberts, C D; Schmidt, S M; Tandy, P C
2013-03-29
We project onto the light front the pion's Poincaré-covariant Bethe-Salpeter wave function obtained using two different approximations to the kernels of quantum chromodynamics' Dyson-Schwinger equations. At an hadronic scale, both computed results are concave and significantly broader than the asymptotic distribution amplitude, φ(π)(asy)(x)=6x(1-x); e.g., the integral of φ(π)(x)/φ(π)(asy)(x) is 1.8 using the simplest kernel and 1.5 with the more sophisticated kernel. Independent of the kernels, the emergent phenomenon of dynamical chiral-symmetry breaking is responsible for hardening the amplitude.
Introduction to Magneto-Fluid-Dynamics for Aerospace Applications
2004-07-08
incisive understanding is strongly dependent on how knowledge is accumulated and transferred in times. The growth of magneto- fluid-dynamics is not...S. Goldstein, Lectures on Fluid Mechanics (Interscience Publishers Ltd, London, 1960). [15] B. Finzi, Principio d’Azione Stazionaria
Effect of Fluid Dynamic Viscosity on the Strength of Chalk
DEFF Research Database (Denmark)
Hedegaard, K.; Fabricius, Ida Lykke
The mechanical strength of high porosity and weakly cemented chalk is affected by the fluid in the pores. In this study, the effect of the dynamic viscosity of non-polar fluids has been measured on outcrop chalk from Sigerslev Quarry, Stevns, Denmark. The outcome is that the measured strength...
The stability and dynamic behaviour of fluid-loaded structures
CSIR Research Space (South Africa)
Suliman, Ridhwaan
2015-07-01
Full Text Available ECCOMAS Young Investigators Conference 6th GACM Colloquium, July 20–23, 2015, Aachen, Germany The stability and dynamic behaviour of fluid-loaded structures R. Suliman, N. Peake Abstract. The deformation of slender elastic structures due...
Modeling of Dynamic Fluid Forces in Fast Switching Valves
DEFF Research Database (Denmark)
Roemer, Daniel Beck; Johansen, Per; Pedersen, Henrik Clemmensen;
2015-01-01
Switching valves experience opposing fluid forces due to movement of the moving member itself, as the surrounding fluid volume must move to accommodate the movement. This movement-induced fluid force may be divided into three main components; the added mass term, the viscous term and the socalled...... history term. For general valve geometries there are no simple solution to either of these terms. During development and design of such switching valves, it is therefore, common practice to use simple models to describe the opposing fluid forces, neglecting all but the viscous term which is determined...... based on shearing areas and venting channels. For fast acting valves the opposing fluid force may retard the valve performance significantly, if appropriate measures are not taken during the valve design. Unsteady Computational Fluid Dynamics (CFD) simulations are available to simulate the total fluid...
Computational fluid dynamics incompressible turbulent flows
Kajishima, Takeo
2017-01-01
This textbook presents numerical solution techniques for incompressible turbulent flows that occur in a variety of scientific and engineering settings including aerodynamics of ground-based vehicles and low-speed aircraft, fluid flows in energy systems, atmospheric flows, and biological flows. This book encompasses fluid mechanics, partial differential equations, numerical methods, and turbulence models, and emphasizes the foundation on how the governing partial differential equations for incompressible fluid flow can be solved numerically in an accurate and efficient manner. Extensive discussions on incompressible flow solvers and turbulence modeling are also offered. This text is an ideal instructional resource and reference for students, research scientists, and professional engineers interested in analyzing fluid flows using numerical simulations for fundamental research and industrial applications. • Introduces CFD techniques for incompressible flow and turbulence with a comprehensive approach; • Enr...
Development of a theoretical framework for analyzing cerebrospinal fluid dynamics
DEFF Research Database (Denmark)
Cohen, Benjamin; Voorhees, Abram; Vedel, Søren
2009-01-01
Background: To date hydrocephalus researchers acknowledge the need for rigorous but utilitarian fluid mechanics understanding and methodologies in studying normal and hydrocephalic intracranial dynamics. Pressure volume models and electric circuit analogs introduced pressure into volume conservat......Background: To date hydrocephalus researchers acknowledge the need for rigorous but utilitarian fluid mechanics understanding and methodologies in studying normal and hydrocephalic intracranial dynamics. Pressure volume models and electric circuit analogs introduced pressure into volume...
Meteorological fluid dynamics asymptotic modelling, stability and chaotic atmospheric motion
Zeytounian, Radyadour K
1991-01-01
The author considers meteorology as a part of fluid dynamics. He tries to derive the properties of atmospheric flows from a rational analysis of the Navier-Stokes equations, at the same time analyzing various types of initial and boundary problems. This approach to simulate nature by models from fluid dynamics will be of interest to both scientists and students of physics and theoretical meteorology.
Mathematical Fluid Dynamics of Store and Stage Separation
2005-05-01
34Theoretical Aerodynamics in Today’s Real World," Opportunities and Challenges," Julian D. Cole Lecture , 4 th AIAA Theoretical Fluid Dynamics Meeting, June...Reports A 4th AIAA Theoretical Fluid Dynamics Meeting Julian D. Cole Lecture June 6-9, 2005 Toronto, Canada AIAA 2005-5059 Theoretical Aerodynamics in...technique was developed to treat the problem of shock manipulation by MHD Lorentz forces in Ref. 68 that has been validated by large scale CFD and
2D fluid simulations of interchange turbulence with ion dynamics
DEFF Research Database (Denmark)
Nielsen, Anders Henry; Madsen, Jens; Xu, G. S.
2013-01-01
In this paper we present a first principle global two-dimensional fluid model. The HESEL (Hot Edge SOL Electrostatic) model is a 2D numerical fluid code, based on interchange dynamics and includes besides electron also the ion pressure dynamic. In the limit of cold ions the model almost reduces......B vorticity as well as the ion diamagnetic vorticity. The 2D domain includes both open and closed field lines and is located on the out-board midplane of a tokamak. On open field field lines the parallel dynamics are parametrized as sink terms depending on the dynamic quantities; density, electron and ion...
Molecular dynamics of a dense fluid of polydisperse hard spheres
Sear, Richard P.
2000-01-01
Slow dynamics in a fluid are studied in one of the most basic systems possible: polydisperse hard spheres. Monodisperse hard spheres cannot be studied as the slow down in dynamics as the density is increased is preempted by crystallisation. As the dynamics slow they become more heterogeneous, the spread in the distances traveled by different particles in the same time increases. However, the dynamics appears to be less heterogeneous than in hard-sphere-like colloids at the same volume fractio...
Fluid-Solid Interaction and Multiscale Dynamic Processes: Experimental Approach
Arciniega-Ceballos, Alejandra; Spina, Laura; Mendo-Pérez, Gerardo M.; Guzmán-Vázquez, Enrique; Scheu, Bettina; Sánchez-Sesma, Francisco J.; Dingwell, Donald B.
2017-04-01
The speed and the style of a pressure drop in fluid-filled conduits determines the dynamics of multiscale processes and the elastic interaction between the fluid and the confining solid. To observe this dynamics we performed experiments using fluid-filled transparent tubes (15-50 cm long, 2-4 cm diameter and 0.3-1 cm thickness) instrumented with high-dynamic piezoelectric sensors and filmed the evolution of these processes with a high speed camera. We analyzed the response of Newtonian fluids to slow and sudden pressure drops from 3 bar-10 MPa to ambient pressure. We used fluids with viscosities of mafic to intermediate silicate melts of 1 to 1000 Pa s and water. The processes observed are fluid mass expansion, fluid flow, jets, bubbles nucleation, growth, coalescence and collapse, degassing, foam building at the surface and vertical wagging. All these processes (in fine and coarse scales) are triggered by the pressure drop and are sequentially coupled in time while interacting with the solid. During slow decompression, the multiscale processes are recognized occurring within specific pressure intervals, and exhibit a localized distribution along the conduit. In this, degassing predominates near the surface and may present piston-like oscillations. In contrast, during sudden decompression the fluid-flow reaches higher velocities, the dynamics is dominated by a sequence of gas-packet pulses driving jets of the gas-fluid mixture. The evolution of this multiscale phenomenon generates complex non-stationary microseismic signals recorded along the conduit. We discuss distinctive characteristics of these signals depending on the decompression style and compare them with synthetics. These synthetics are obtained numerically under an averaging modeling scheme, that accounted for the stress-strain of the cyclic dynamic interaction between the fluid and the solid wall, assuming an incompressible and viscous fluid that flows while the elastic solid responds oscillating
The Tibetan singing bowl : an acoustics and fluid dynamics investigation
Terwagne, Denis
2011-01-01
We present the results of an experimental investigation of the acoustics and fluid dynamics of Tibetan singing bowls. Their acoustic behavior is rationalized in terms of the related dynamics of standing bells and wine glasses. Striking or rubbing a fluid-filled bowl excites wall vibrations, and concomitant waves at the fluid surface. Acoustic excitation of the bowl's natural vibrational modes allows for a controlled study in which the evolution of the surface waves with increasing forcing amplitude is detailed. Particular attention is given to rationalizing the observed criteria for the onset of edge-induced Faraday waves and droplet generation via surface fracture. Our study indicates that drops may be levitated on the fluid surface, induced to bounce on or skip across the vibrating fluid surface.
Fluid dynamical niches of phytoplankton types.
d'Ovidio, Francesco; De Monte, Silvia; Alvain, Séverine; Dandonneau, Yves; Lévy, Marina
2010-10-26
The biogeochemical role of phytoplanktonic organisms strongly varies from one plankton type to another, and their relative abundance and distribution have fundamental consequences at the global and climatological scales. In situ observations find dominant types often associated to specific physical and chemical water properties. However, the mechanisms and spatiotemporal scales by which marine ecosystems are organized are largely not known. Here we investigate the spatiotemporal organization of phytoplankton communities by combining multisatellite data, notably high-resolution ocean-color maps of dominant types and altimetry-derived Lagrangian diagnostics of the surface transport. We find that the phytoplanktonic landscape is organized in (sub-)mesoscale patches (10-100 km) of dominant types separated by physical fronts induced by horizontal stirring. These physical fronts delimit niches supported by water masses of similar history and whose lifetimes are comparable with the timescale of the bloom onset (few weeks). The resonance between biological activity and physical processes suggest that the spatiotemporal (sub-)mesoscales associated to stirring are determinant in the observation and modeling of marine ecosystems.
Hard sphere dynamics for normal and granular fluids.
Dufty, James W; Baskaran, Aparna
2005-06-01
A fluid of N smooth, hard spheres is considered as a model for normal (elastic collision) and granular (inelastic collision) fluids. The potential energy is discontinuous for hard spheres so that the pairwise forces are singular and the usual forms of Newtonian and Hamiltonian mechanics do not apply. Nevertheless, particle trajectories in the N particle phase space are well defined and the generators for these trajectories can be identified. The first part of this presentation is a review of the generators for the dynamics of observables and probability densities. The new results presented in the second part refer to applications of these generators to the Liouville dynamics for granular fluids. A set of eigenvalues and eigenfunctions of the generator for this Liouville dynamics system is identified in a special stationary representation. This provides a class of exact solutions to the Liouville equation that are closely related to hydrodynamics for granular fluids.
Martinez-Pedrero, Fernando; Tierno, Pietro; Johansen, Tom H; Straube, Arthur V
2016-02-03
The emergence of wave fronts in dissipative driven systems is a fascinating phenomenon which can be found in a broad range of physical and biological disciplines. Here we report the direct experimental observation of discrete fronts propagating along chains of paramagnetic colloidal particles, the latter propelled above a traveling wave potential generated by a structured magnetic substrate. We develop a rigorously reduced theoretical framework and describe the dynamics of the system in terms of a generalized one-dimensional dissipative Frenkel-Kontorova model. The front dynamics is explored in a wide range of field parameters close to and far from depinning, where the discrete and continuum limits apply. We show how symmetry breaking and finite size of chains are used to control the direction of front propagation, a universal feature relevant to different systems and important for real applications.
Cerebral venous outflow and cerebrospinal fluid dynamics
Directory of Open Access Journals (Sweden)
Clive B. Beggs
2014-12-01
Full Text Available In this review, the impact of restricted cerebral venous outflow on the biomechanics of the intracranial fluid system is investigated. The cerebral venous drainage system is often viewed simply as a series of collecting vessels channeling blood back to the heart. However there is growing evidence that it plays an important role in regulating the intracranial fluid system. In particular, there appears to be a link between increased cerebrospinal fluid (CSF pulsatility in the Aqueduct of Sylvius and constricted venous outflow. Constricted venous outflow also appears to inhibit absorption of CSF into the superior sagittal sinus. The compliance of the cortical bridging veins appears to be critical to the behaviour of the intracranial fluid system, with abnormalities at this location implicated in normal pressure hydrocephalus. The compliance associated with these vessels appears to be functional in nature and dependent on the free egress of blood out of the cranium via the extracranial venous drainage pathways. Because constricted venous outflow appears to be linked with increased aqueductal CSF pulsatility, it suggests that inhibited venous blood outflow may be altering the compliance of the cortical bridging veins.
Optics and Fluid Dynamics Department. Annual progress report for 2001
Energy Technology Data Exchange (ETDEWEB)
Bindslev, H.; Hanson, S.G.; Lynov, J.P.; Petersen, P.M.; Skaarup, B. (eds.)
2002-03-01
The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: 1) laser systems and optical materials, 2) optical diagnostics and information processing and 3) plasma and fluid dynamics. The department has core competence in: optical sensors, optical materials, optical storage, bio-optics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2001 is presented. (au)
Optics and Fluid Dynamics Department annual progress report for 2000
Energy Technology Data Exchange (ETDEWEB)
Hanson, S.G.; Johansen, P.M.; Lynov, J.P.; Skaarup, B. (eds.)
2001-05-01
The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The department has core competence in: optical sensors, optical materials, optical storage, bio-optics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2000 is presented. (au)
Optics and Fluid Dynamics Department annual progress report for 2001
DEFF Research Database (Denmark)
Bindslev, H.; Hanson, Steen Grüner; Lynov, Jens-Peter;
2002-01-01
The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) laser systems and optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The departmenthas core competences in: optical sensors......, optical materials, optical storage, biooptics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM,by Danish research councils and by industry. A summary of the activities in 2001 is presented....
Optics and Fluid Dynamics Department. Annual Progress Report for 2002
Energy Technology Data Exchange (ETDEWEB)
Bindslev, H.; Hanson, S.G.; Lynov, J.P.; Petersen, P.M.; Skaarup, B
2003-05-01
The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) Laser systems and optical materials (2) Optical diagnostics and information processing and (3) Plasma and fluid dynamics. The department has core competences in: optical sensors, optical materials, optical storage, biophotonics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2002 is presented. (au)
Optics and Fluid Dynamics Department. Annual progress report for 2003
Energy Technology Data Exchange (ETDEWEB)
Bindslev, H.; Hanson, S.G.; Lynov, J.P.; Petersen, P.M.; Skaarup, B. (eds.)
2004-05-01
The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1 laser systems and optical materials, (2 optical diagnostics and information processing and (3 plasma and fluid dynamics. The department has core competences in: optical sensors, optical materials, optical storage, biophotonics, numerical modelling and information processing, non-linear dynamics, fusion plasma physics and plasma technology. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2003 is presented. (au)
The problem of fluid-dynamics in semicircular canal
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
An analytical solution with high accuracy which holds for any values of ε for fluid-dynamics model equation in a single semicircular canal presented by Buskirk and his co-workers has been obtained.It not only includes all of the results of Buskirk et al.but also covers three possible kinds of dynamical response modes in practice.The theoretical results are in better agreement with those of experimental observations.This investigation has laid a reliable theoretical foundation for quantitatively understanding fluid-dynamics in semicircular canal,especially fluid dynamical response.The distribution of the velocity of the endolymph in semicircular canal is given.A nonstandard method of the inverse Laplace transform is presented.
The problem of fluid-dynamics in semicircular canal
Institute of Scientific and Technical Information of China (English)
徐明瑜; 谭文长
2000-01-01
An analytical solution with high accuracy which holds for any values of E for fluid-dynamics model eguation in a single semicircular canal presented by Buskirk and his co-workers has been ob-tained. it not only includes ali of the results of Buskirk et al. but also covers three possible kinds of dy-namical response modes in practice. The theoretical results are in betler agreement with those of ex-perimental observations. This investigation has laid a reliable theoretical foundation for quantitatively understanding fluid-dynamics in semicircular canal, especially fluid dynamical response. The distribu-tion of the velocity of the endolymph in semicircular canal is given. A nonstandard method of the in-verse Laplace transform is presented.
Prandtl, Ludwig
1953-01-01
Equilibrium of liquids and gases ; kinematics : dynamics of frictionless fluids ; motion of viscous fluids : turbulence : fluid resistance : practical applications ; flow with appreciable volume changes (dynamics of gases) ; miscellaneous topics.
Light-front representation of chiral dynamics with Δ isobar and large- N c relations
Granados, C.; Weiss, C.
2016-06-01
Transverse densities describe the spatial distribution of electromagnetic current in the nucleon at fixed light-front time. At peripheral distances b = O( M π - 1 ) the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). Recent work has shown that the EFT results can be represented in first-quantized form, as overlap integrals of chiral light-front wave functions describing the transition of the nucleon to soft-pion-nucleon intermediate states, resulting in a quantum-mechanical picture of the peripheral transverse densities. We now extend this representation to include intermediate states with Δ isobars and implement relations based on the large- N c limit of QCD. We derive the wave function overlap formulas for the Δ contributions to the peripheral transverse densities by way of a three-dimensional reduction of relativistic chiral EFT expressions. Our procedure effectively maintains rotational invariance and avoids the ambiguities with higher-spin particles in the light-front time-ordered approach. We study the interplay of π N and πΔ intermediate states in the quantum-mechanical picture of the densities in a transversely polarized nucleon. We show that the correct N c -scaling of the charge and magnetization densities emerges as the result of the particular combination of currents generated by intermediate states with degenerate N and Δ. The off-shell behavior of the chiral EFT is summarized in contact terms and can be studied easily. The methods developed here can be applied to other peripheral densities and to moments of the nucleon's generalized parton distributions.
Adaptive finite difference methods in fluid dynamics
Berger, Marsha J.
1987-01-01
An adaptive method to solve partial differential equations in fluid mechanics is presented. The approach requires internal boundary conditions that must be conservative, data structures for keeping track of several layers of fine grid patches, error estimation, and heuristics for automatic grid generation. In practical calculations gains in computer efficiency up to 10 over nonadaptive methods are observed. The whole procedure takes 3000 lines of FORTRAN code.
Cerebrospinal Fluid Dynamics and the Pathophysiology of Hydrocephalus: New Concepts.
Yamada, Shinya; Kelly, Erin
2016-04-01
Many controversies remain regarding basic cerebrospinal fluid (CSF) physiology and the mechanism behind the development of hydrocephalus. Recent information obtained from CSF time spatial spin labeling inversion pulse method discovers different aspect of CSF dynamics. In this article, we would discuss how recent CSF imaging advances are leading to new concepts of CSF flow dynamics and the pathophysiology of hydrocephalus, with an emphasis on time spatial spin labeling inversion pulse imaging of CSF dynamics.
A low-power high dynamic range front-end ASIC for imaging calorimeters
Bagliesi, M G; Marrocchesi, P S; Meucci, M; Millucci, V; Morsani, F; Paoletti, R; Pilo, F; Scribano, A; Turini, N; Valle, G D
2002-01-01
High granularity calorimeters with shower imaging capabilities require dedicated front-end electronics. The ICON 4CH and VA4 PMT chip-set is suitable for very high dynamic range systems with strict noise requirements. The ICON 4CH is a 4 channel input, 12 channel output ASIC designed for use in a multi-anode photomultiplier system with very large dynamic range and low-noise requirements. Each of the four input signals to the ASIC is split equally into three branches by a current conveyor. Each of the three branches is scaled differently: 1:1, 1:8 and 1:80. The signal is read out by a 12 channel low noise/low power high dynamic range charge sensitive preamplifier-shaper circuit (VA4-PMT chip), with simultaneous sample- and-hold, multiplexed analog read-out, calibration facilities. Tests performed in our lab with a PMT are reported in terms of linearity, dynamic range and cross-talk of the system. (5 refs).
Engineering Applications of Computational Fluid Dynamics: Volume 2
Directory of Open Access Journals (Sweden)
Maher A.R. Sadiq Al-Baghdadi
2013-01-01
Full Text Available Chapter 1: CFD Modeling of Methane Reforming in Compact Reformers. Meng Ni Chapter 2: FEM Based Solution of Thermo Fluid Dynamic Phenomena in Solid Oxide Fuel Cells (SOFCS. F. Arpino, A. Carotenuto, N. Massarotti, A. Mauro Chapter 3: Computational Fluid Dynamics in the Development of a 3D Simulator for Testing Pollution Monitoring Robotic Fishes. John Oyekan, Bowen Lu, Huosheng Hu Chapter 4: CFD Applications in Electronic Packaging. C.Y. Khor, Chun-Sean Lau, M.Z. Abdullah Chapter 5: CFD Simulation of Savonius Wind Turbine Operation. Jo?o Vicente Akwa, Adriane Prisco Petry Chapter 6: Intermittency Modelling of Transitional Boundary Layer Flows on Steam and Gas Turbine Blades. Erik Dick, Slawomir Kubacki, Koen Lodefier, Witold Elsner Chapter 7: Numerical Analysis of the Flow through Fitting in Air Conditioning Systems. N.C. Uz?rraga-Rodriguez, A. Gallegos-Mu?oz, J.M. Belman-Flores, J.C. Rubio-Arana Chapter 8: Design and Optimization of Food Processing Equipments using Computational Fluid Dynamics Modeling. N. Chhanwal and C. Anandharamakrishnan Chapter 9: Fuel and Intake Systems Optimization of a Converted LPG Engine: Steady and Unsteady in-Cylinder Flow CFD Investigations and Experiments Validation. M. A. Jemni, G. Kantchev, Z. Driss, M. S. Abid Chapter 10: Computational Fluid Dynamics Application for Thermal Management in Underground Mines. Agus P. Sasmito, Jundika C. Kurnia, Guan Mengzhao, Erik Birgersson, Arun S. Mujumdar Chapter 11: Computational Fluid Dynamics and its Applications. R.Parthiban, C.Muthuraj, A.Rajakumar
Roughness and intermittent dynamics of imbibition fronts due to capillary and permeability disorder.
Planet, Ramon; Santucci, Stéphane; Ortín, Jordi
2011-03-01
We follow the propagation of an air-liquid interface during forced-flow imbibition of a viscous wetting liquid by a random medium, using a high resolution fast camera. Our model disordered medium mimics an open fracture by a Hele-Shaw cell with a two-valued gap spacing randomly distributed in the fracture (or Hele-Shaw) plane. By systematically varying the imposed flow rate we achieve average imbibition front velocities in the range 0.057x=1.3±0.1 for the joint distribution of sizes vs. durations. These values are in excellent agreement with the ones measured previously in the capillary regime (Planet et al., 2009). The dynamics therefore appear to be equivalent in both regimes, a result that we relate to the fact that the correlation length of the local velocities along the front is observed to follow the same dependence l(c)~1/v in both regimes. Copyright © 2010 Elsevier B.V. All rights reserved.
a Study of the Dynamics of Maritime Fronts Using Remotely Sensed Wind and Stress Measurements.
Levy, Gad
The satellite scatterometer data open unprecedented opportunities to look at maritime storms and fronts. They are combined with observations, modeling efforts, and theory to study five cases. These provide the data to investigate frontal behavior in terms of its vorticity and divergence. The appropriate momentum, divergence and vorticity equations are derived and investigated including the inertial and the frictional terms. The analysis is used to study frontal dynamics. The results indicate that the large scale horizontal and vertical thermodynamic structure of the boundary layer significantly influence baroclinic waves and frontal structure. These effects promote more efficient mixing and transport of heat, moisture, and westerly momentum in midlatitude storms. The conclusions are: (1) The analyzed satellite scatterometer winds are suited for input to a planetary boundary layer model which yields synoptic scale surface pressure analyses commensurate with current analyses based on buoy and ship observations. (2) Surface analysis may be improved when model pressure fields, scatterometer convergence patterns, and microwave radiometer vapor fields are used together. (3) The convergence usually coincides with cyclonic vorticity at frontal zones. However, the maxima in vorticity and convergence normally do not completely coincide. A significant out-of-phase relationship which was observed for one storm in its explosive stage is suggested to be a result of gravity wave activity. (4) Surface friction is important in frontal processes. This is shown in the divergence and the vorticity equations through the role of friction in determining the dissipation and the ageostrophic terms. (5) In frontal situations the dissipation term normally acts to weaken the front and thus could be regarded as a mechanism that can help in bringing a front towards a steady state. (6) The ageostrophic term normally acts to strengthen a front, and except for some special conditions, could be
Relaxation Dynamics of Non-Power-Law Fluids
Min, Qi; Duan, Yuan-Yuan; Wang, Xiao-Dong; Liang, Zhan-Peng; Lee, Duu-Jong
2013-12-01
The relaxation of non-Newtonian liquids with non-power-law rheology on partially wetted surfaces is rarely investigated. This study assesses the relaxation behavior of 14 partial wetting systems with non-power-law fluids by sessile drop method. These systems are two carboxymethylcellulose sodium solutions on two kinds of slides, cover glass, and silicon wafer surfaces; three polyethylene glycol (PEG400) + silica nanoparticle suspensions on polymethyl methacrylate and polystyrene surfaces. The dynamic contact angle and moving velocity of contact line relationship data for relaxation drops of the 14 tested systems demonstrate a power-law fluid-like behavior, and the equivalent power exponent for a certain fluid on different solid substrates are uniform. By analyzing the relationship between the equivalent power exponent and shear rate, it is proposed that a fluid regime with shear rates of a few tens of s controls relaxation dynamics.
Resolving Neighbourhood Relations in a Parallel Fluid Dynamic Solver
Frisch, Jerome
2012-06-01
Computational Fluid Dynamics simulations require an enormous computational effort if a physically reasonable accuracy should be reached. Therefore, a parallel implementation is inevitable. This paper describes the basics of our implemented fluid solver with a special aspect on the hierarchical data structure, unique cell and grid identification, and the neighbourhood relations in-between grids on different processes. A special server concept keeps track of every grid over all processes while minimising data transfer between the nodes. © 2012 IEEE.
Improved Pyrolysis Micro reactor Design via Computational Fluid Dynamics Simulations
2017-05-23
NUMBER (Include area code) 23 May 2017 Briefing Charts 25 April 2017 - 23 May 2017 Improved Pyrolysis Micro-reactor Design via Computational Fluid... PYROLYSIS MICRO-REACTOR DESIGN VIA COMPUTATIONAL FLUID DYNAMICS SIMULATIONS Ghanshyam L. Vaghjiani* DISTRIBUTION A: Approved for public release...Approved for public release, distribution unlimited. PA Clearance 17247 Chen-Source (>240 references from SciFinder as of 5/1/17): Flash pyrolysis
Statistic fluid dynamic of multiphase flow
Lim, Hyunkyung; Glimm, James; Zhou, Yijie; Jiao, Xiangmin
2012-11-01
We study a turbulent two-phase fluid mixing problem from a statistical point of view. The test problem is high speed turbulent two-phase Taylor-Couette flow. We find extensive mixing in a transient state between an initial unstable and a final stable configuration. With chemical processing as a motivation, we estimate statistically surface area, droplet size distribution and transient droplet duration. This work is supported in part by the Nuclear Energy University Program of the Department of Energy, Battelle Energy Alliance LLC 00088495.
Dynamic motion stabilization for front-wheel drive in-wheel motor electric vehicles
Directory of Open Access Journals (Sweden)
Jia-Sheng Hu
2015-12-01
Full Text Available This article presents a new dynamic motion stabilization approach to front-wheel drive in-wheel motor electric vehicles. The approach includes functions such as traction control system, electronic differential system, and electronic stability control. The presented electric vehicle was endowed with anti-skid performance in longitudinal accelerated start; smooth turning with less tire scrubbing; and safe driving experience in two-dimensional steering. The analysis of the presented system is given in numerical derivations. For practical verifications, this article employed a hands-on electric vehicle named Corsa-electric vehicle to carry out the tests. The presented approach contains an integrated scheme which can achieve the mentioned functions in a single microprocessor. The experimental results demonstrated the effectiveness and feasibility of the presented methodology.
Fluid Dynamical Consequences of Current and Stress-Energy Conservation
Scofield, Dillon; Huq, Pablo
The dynamical consequences of fluid current conservation combined with the conservation of fluid stress-energy are used to develop the geometrodynamical theory of fluid flow (GTF). In the derivation of the GTF, we highlight the fact the continuity equation, equivalently the conservation of current density, implies the existence of the fluid dynamical vortex field. The vortex field transports part of the stress-energy; the other part of the stress-energy is transported by the fluid inertia field. Two channels of energy dissipation are determined by the GTF. One is an analog of the Joule heating found in electrodynamics. This follows from the conservation of stress-energy. The other dissipation channel arises from mechanisms leading to complex-valued constitutive parameters described in the electrodynamical analogy as due to a lossy medium. The dynamical consequences of the continuity equation, combined with the conservation of total stress-energy, then lead to a causal, covariant, theory of fluid flow, consistent with thermodynamics for all physically possible flow rates.
Nonlocal dynamics of dissipative phononic fluids
Nemati, Navid; Lee, Yoonkyung E.; Lafarge, Denis; Duclos, Aroune; Fang, Nicholas
2017-06-01
We describe the nonlocal effective properties of a two-dimensional dissipative phononic crystal made by periodic arrays of rigid and motionless cylinders embedded in a viscothermal fluid such as air. The description is based on a nonlocal theory of sound propagation in stationary random fluid/rigid media that was proposed by Lafarge and Nemati [Wave Motion 50, 1016 (2013), 10.1016/j.wavemoti.2013.04.007]. This scheme arises from a deep analogy with electromagnetism and a set of physics-based postulates including, particularly, the action-response procedures, whereby the effective density and bulk modulus are determined. Here, we revisit this approach, and clarify further its founding physical principles through presenting it in a unified formulation together with the two-scale asymptotic homogenization theory that is interpreted as the local limit. Strong evidence is provided to show that the validity of the principles and postulates within the nonlocal theory extends to high-frequency bands, well beyond the long-wavelength regime. In particular, we demonstrate that up to the third Brillouin zone including the Bragg scattering, the complex and dispersive phase velocity of the least-attenuated wave in the phononic crystal which is generated by our nonlocal scheme agrees exactly with that reproduced by a direct approach based on the Bloch theorem and multiple scattering method. In high frequencies, the effective wave and its associated parameters are analyzed by treating the phononic crystal as a random medium.
A dynamic neutral fluid model for the PIC scheme
Wu, Alan; Lieberman, Michael; Verboncoeur, John
2010-11-01
Fluid diffusion is an important aspect of plasma simulation. A new dynamic model is implemented using the continuity and boundary equations in OOPD1, an object oriented one-dimensional particle-in-cell code developed at UC Berkeley. The model is described and compared with analytical methods given in [1]. A boundary absorption parameter can be adjusted from ideal absorption to ideal reflection. Simulations exhibit good agreement with analytic time dependent solutions for the two ideal cases, as well as steady state solutions for mixed cases. For the next step, fluid sources and sinks due to particle-particle or particle-fluid collisions within the simulation volume and to surface reactions resulting in emission or absorption of fluid species will be implemented. The resulting dynamic interaction between particle and fluid species will be an improvement to the static fluid in the existing code. As the final step in the development, diffusion for multiple fluid species will be implemented. [4pt] [1] M.A. Lieberman and A.J. Lichtenberg, Principles of Plasma Discharges and Materials Processing, 2nd Ed, Wiley, 2005.
A Textbook for a First Course in Computational Fluid Dynamics
Zingg, D. W.; Pulliam, T. H.; Nixon, David (Technical Monitor)
1999-01-01
This paper describes and discusses the textbook, Fundamentals of Computational Fluid Dynamics by Lomax, Pulliam, and Zingg, which is intended for a graduate level first course in computational fluid dynamics. This textbook emphasizes fundamental concepts in developing, analyzing, and understanding numerical methods for the partial differential equations governing the physics of fluid flow. Its underlying philosophy is that the theory of linear algebra and the attendant eigenanalysis of linear systems provides a mathematical framework to describe and unify most numerical methods in common use in the field of fluid dynamics. Two linear model equations, the linear convection and diffusion equations, are used to illustrate concepts throughout. Emphasis is on the semi-discrete approach, in which the governing partial differential equations (PDE's) are reduced to systems of ordinary differential equations (ODE's) through a discretization of the spatial derivatives. The ordinary differential equations are then reduced to ordinary difference equations (O(Delta)E's) using a time-marching method. This methodology, using the progression from PDE through ODE's to O(Delta)E's, together with the use of the eigensystems of tridiagonal matrices and the theory of O(Delta)E's, gives the book its distinctiveness and provides a sound basis for a deep understanding of fundamental concepts in computational fluid dynamics.
Compatible finite element spaces for geophysical fluid dynamics
Natale, Andrea
2016-01-01
Compatible finite elements provide a framework for preserving important structures in equations of geophysical fluid dynamics, and are becoming important in their use for building atmosphere and ocean models. We survey the application of compatible finite element spaces to geophysical fluid dynamics, including the application to the nonlinear rotating shallow water equations, and the three-dimensional compressible Euler equations. We summarise analytic results about dispersion relations and conservation properties, and present new results on approximation properties in three dimensions on the sphere, and on hydrostatic balance properties.
Thermo-Fluid Dynamics of Two-Phase Flow
Ishii, Mamrou
2011-01-01
"Thermo-fluid Dynamics of Two-Phase Flow, Second Edition" is focused on the fundamental physics of two-phase flow. The authors present the detailed theoretical foundation of multi-phase flow thermo-fluid dynamics as they apply to: Nuclear reactor transient and accident analysis; Energy systems; Power generation systems; Chemical reactors and process systems; Space propulsion; Transport processes. This edition features updates on two-phase flow formulation and constitutive equations and CFD simulation codes such as FLUENT and CFX, new coverage of the lift force model, which is of part
Stochastic hard-sphere dynamics for hydrodynamics of nonideal fluids.
Donev, Aleksandar; Alder, Berni J; Garcia, Alejandro L
2008-08-15
A novel stochastic fluid model is proposed with a nonideal structure factor consistent with compressibility, and adjustable transport coefficients. This stochastic hard-sphere dynamics (SHSD) algorithm is a modification of the direct simulation Monte Carlo algorithm and has several computational advantages over event-driven hard-sphere molecular dynamics. Surprisingly, SHSD results in an equation of state and a pair correlation function identical to that of a deterministic Hamiltonian system of penetrable spheres interacting with linear core pair potentials. The fluctuating hydrodynamic behavior of the SHSD fluid is verified for the Brownian motion of a nanoparticle suspended in a compressible solvent.
Baroclinic Channel Model in Fluid Dynamics
Directory of Open Access Journals (Sweden)
Kharatti Lal
2016-02-01
Full Text Available A complex flow structure is studied using a 2-dimentional baroclinic channel model Unsteady Navier - stokes equation coupled with equation of thermal energy ,salinity and the equation of state are implemented .System closure is achieved through a modified Prandtl, s mixing length formulation of turbulence dissipation The model is applied in a region where the fluid flow is effected by various forcing equation .In this case ,flow is estuarine region affected by diurnal tide and the fresh water inflow in to the estuary and a submerged structure is considered giving possible insight in to stress effects on submerged structure .the result show that in the time evolution of the vertical velocity along downstream edge changes sign from negative to positive .as the dike length increases the primary cell splits and flow becomes turbulent du e to the non-linear effect caused by the dike .these are found to agree favourably with result published in the open literature.
Archer, A J
2009-01-07
In recent years, a number of dynamical density functional theories (DDFTs) have been developed for describing the dynamics of the one-body density of both colloidal and atomic fluids. In the colloidal case, the particles are assumed to have stochastic equations of motion and theories exist for both the case when the particle motion is overdamped and also in the regime where inertial effects are relevant. In this paper, we extend the theory and explore the connections between the microscopic DDFT and the equations of motion from continuum fluid mechanics. In particular, starting from the Kramers equation, which governs the dynamics of the phase space probability distribution function for the system, we show that one may obtain an approximate DDFT that is a generalization of the Euler equation. This DDFT is capable of describing the dynamics of the fluid density profile down to the scale of the individual particles. As with previous DDFTs, the dynamical equations require as input the Helmholtz free energy functional from equilibrium density functional theory (DFT). For an equilibrium system, the theory predicts the same fluid one-body density profile as one would obtain from DFT. Making further approximations, we show that the theory may be used to obtain the mode coupling theory that is widely used for describing the transition from a liquid to a glassy state.
Computational modeling of glow discharge-induced fluid dynamics
Jayaraman, Balaji
Glow discharge at atmospheric pressure using a dielectric barrier discharge can induce fluid flow and operate as an actuator for flow control. The largely isothermal surface plasma generation realized above can modify the near-wall flow structure by means of Lorentzian collisions between the ionized fluid and the neutral fluid. Such an actuator has advantages of no moving parts, performance at atmospheric conditions and devising complex control strategies through the applied voltage. However, the mechanism of the momentum coupling between the plasma and the fluid flow is not yet adequately understood. In the present work, a modeling framework is presented to simulate athermal, non-equilibrium plasma discharges in conjunction with low Mach number fluid dynamics at atmospheric pressure. The plasma and fluid species are treated as a two-fluid system exhibiting a few decades of length and time scales. The effect of the plasma dynamics on the fluid dynamics is devised via a body force treatment in the Navier-Stokes equations. Two different approaches of different degrees of fidelity are presented for modeling the plasma dynamics. The first approach, a phenomenological model, is based on a linearized force distribution approximating the discharge structure, and utilizing experimental guidance to deduce the empirical constants. A high fidelity approach is to model the plasma dynamics in a self-consistent manner using a first principle-based hydrodynamic plasma model. The atmospheric pressure regime of interest here enables us to employ local equilibrium assumptions, signifying efficient collisional energy exchange as against thermal heating from inelastic collision processes. The time scale ratios between convection, diffusion, and reaction/ionization mechanisms are O(107), making the system computationally stiff. To handle the stiffness, a sequential finite-volume operator-splitting algorithm capable of conserving space charge is developed; the approach can handle time
Eisner, M. (Editor)
1974-01-01
The possible utilization of the zero gravity resource for studies in a variety of fluid dynamics and fluid-dynamic related problems was investigated. A group of experiments are discussed and described in detail; these include experiments in the areas of geophysical fluid models, fluid dynamics, mass transfer processes, electrokinetic separation of large particles, and biophysical and physiological areas.
Prediction of Dynamic Wellbore Pressure in Gasified Fluid Drilling
Institute of Scientific and Technical Information of China (English)
Wang Zhiming; Ping Liqiu; Zou Ke
2007-01-01
The basis of designing gasified drilling is to understand the behavior of gas/liquid two-phase flow in the wellbore. The equations of mass and momentum conservation and equation of fluid flow in porous media were used to establish a dynamic model to predict weIlbore pressure according to the study results of Ansari and Beggs-Brill on gas-liquid two-phase flow. The dynamic model was solved by the finite difference approach combined with the mechanistic steady state model. The mechanistic dynamic model was numerically implemented into a FORTRAN 90 computer program and could simulate the coupled flow of fluid in wellbore and reservoir. The dynamic model revealed the effects of wellhead back pressure and injection rate of gas/liquid on bottomhole pressure. The model was validated against full-scale experimental data, and its 5.0% of average relative error could satisfy the accuracy requirements in engineering design.
Cerebrospinal Fluid Mechanics and Its Coupling to Cerebrovascular Dynamics
Linninger, Andreas A.; Tangen, Kevin; Hsu, Chih-Yang; Frim, David
2016-01-01
Cerebrospinal fluid (CSF) is not stagnant but displays fascinating oscillatory flow patterns inside the ventricular system and reversing fluid exchange between the cranial vault and spinal compartment. This review provides an overview of the current knowledge of pulsatile CSF motion. Observations contradicting classical views about its bulk production and clearance are highlighted. A clinical account of diseases of abnormal CSF flow dynamics, including hydrocephalus, syringomyelia, Chiari malformation type 1, and pseudotumor cerebri, is also given. We survey medical imaging modalities used to observe intracranial dynamics in vivo. Additionally, we assess the state of the art in predictive models of CSF dynamics. The discussion addresses open questions regarding CSF dynamics as they relate to the understanding and management of diseases.
Green Algae as Model Organisms for Biological Fluid Dynamics.
Goldstein, Raymond E
2015-01-01
In the past decade the volvocine green algae, spanning from the unicellular Chlamydomonas to multicellular Volvox, have emerged as model organisms for a number of problems in biological fluid dynamics. These include flagellar propulsion, nutrient uptake by swimming organisms, hydrodynamic interactions mediated by walls, collective dynamics and transport within suspensions of microswimmers, the mechanism of phototaxis, and the stochastic dynamics of flagellar synchronization. Green algae are well suited to the study of such problems because of their range of sizes (from 10 μm to several millimetres), their geometric regularity, the ease with which they can be cultured and the availability of many mutants that allow for connections between molecular details and organism-level behavior. This review summarizes these recent developments and highlights promising future directions in the study of biological fluid dynamics, especially in the context of evolutionary biology, that can take advantage of these remarkable organisms.
Dissipative particle dynamics simulation for the density currents of polymer fluids
Li, Yanggui; Geng, Xingguo; Liu, Zhijun; Liu, Qingsheng; Ouyang, Jie
2016-11-01
In this work, the two-dimensional lock-exchange density currents of polymer fluids are numerically investigated using dissipative particle dynamics (DPD) at the mesoscale particle level. A modified finitely extensible nonlinear elastic (FENE) chain model is chosen to describe the polymer system, which perfectly depicts not only the elastic tension but also the elastic repulsion between the adjacent beads with bond length as the equilibrium length of one segment. Through the model and numerical simulation, we analyze the dynamics behavior of the density currents of polymer fluids. A comparison with its Newtonian counterpart suggests that the interface between two polymer fluids is more smoothed, and the front structure is different from the Newtonian case because the Kelvin-Helmholtz instability and cleft instability are suppressed by the polymer. Besides, we also probe the influences of polymer volume concentration, chain length and extensibility on the density currents. These simulation results show that increasing any of the parameters, concentration, chain length, and extensibility, the inhibiting effect of polymer on the density currents becomes more significant.
Fluid Dynamics in Rotary Piston Blood Pumps.
Wappenschmidt, Johannes; Sonntag, Simon J; Buesen, Martin; Gross-Hardt, Sascha; Kaufmann, Tim; Schmitz-Rode, Thomas; Autschbach, Ruediger; Goetzenich, Andreas
2017-03-01
Mechanical circulatory support can maintain a sufficient blood circulation if the native heart is failing. The first implantable devices were displacement pumps with membranes. They were able to provide a sufficient blood flow, yet, were limited because of size and low durability. Rotary pumps have resolved these technical drawbacks, enabled a growing number of mechanical circulatory support therapy and a safer application. However, clinical complications like gastrointestinal bleeding, aortic insufficiency, thromboembolic complications, and impaired renal function are observed with their application. This is traced back to their working principle with attenuated or non-pulsatile flow and high shear stress. Rotary piston pumps potentially merge the benefits of available pump types and seem to avoid their complications. However, a profound assessment and their development requires the knowledge of the flow characteristics. This study aimed at their investigation. A functional model was manufactured and investigated with particle image velocimetry. Furthermore, a fluid-structure interaction computational simulation was established to extend the laboratory capabilities. The numerical results precisely converged with the laboratory measurements. Thus, the in silico model enabled the investigation of relevant areas like gap flows that were hardly feasible with laboratory means. Moreover, an economic method for the investigation of design variations was established.
Recent Developments in the Fluid Dynamics of Tropical Cyclones
Montgomery, Michael T.; Smith, Roger K.
2017-01-01
This article reviews progress in understanding the fluid dynamics and moist thermodynamics of tropical cyclone vortices. The focus is on the dynamics and moist thermodynamics of vortex intensification and structure. We discuss previous ideas on many facets of the subject and articulate also some open questions. The advances reviewed herein provide new insight and tools for interpreting complex vortex-convective phenomenology in simulated and observed tropical cyclones.
Dynamic Behavior of Axially Functionally Graded Pipes Conveying Fluid
Directory of Open Access Journals (Sweden)
Chen An
2017-01-01
Full Text Available Dynamic behavior of axially functionally graded (FG pipes conveying fluid was investigated numerically by using the generalized integral transform technique (GITT. The transverse vibration equation was integral transformed into a coupled system of second-order differential equations in the temporal variable. The Mathematica’s built-in function, NDSolve, was employed to numerically solve the resulting transformed ODE system. Excellent convergence of the proposed eigenfunction expansions was demonstrated for calculating the transverse displacement at various points of axially FG pipes conveying fluid. The proposed approach was verified by comparing the obtained results with the available solutions reported in the literature. Moreover, parametric studies were performed to analyze the effects of Young’s modulus variation, material distribution, and flow velocity on the dynamic behavior of axially FG pipes conveying fluid.
A Computational Fluid Dynamics Algorithm on a Massively Parallel Computer
Jespersen, Dennis C.; Levit, Creon
1989-01-01
The discipline of computational fluid dynamics is demanding ever-increasing computational power to deal with complex fluid flow problems. We investigate the performance of a finite-difference computational fluid dynamics algorithm on a massively parallel computer, the Connection Machine. Of special interest is an implicit time-stepping algorithm; to obtain maximum performance from the Connection Machine, it is necessary to use a nonstandard algorithm to solve the linear systems that arise in the implicit algorithm. We find that the Connection Machine ran achieve very high computation rates on both explicit and implicit algorithms. The performance of the Connection Machine puts it in the same class as today's most powerful conventional supercomputers.
Surface accumulation of spermatozoa: a fluid dynamic phenomenon
Smith, David J
2010-01-01
Recent mathematical fluid dynamics models have shed light into an outstanding problem in reproductive biology: why do spermatozoa cells show a 'preference' for swimming near to surfaces? In this paper we review quantitative approaches to the problem, originating with the classic paper of Lord Rothschild in 1963. A recent 'boundary integral/slender body theory' mathematical model for the fluid dynamics is described, and we discuss how it gives insight into the mechanisms that may be responsible for the surface accumulation behaviour. We use the simulation model to explore these mechanisms in more detail, and discuss whether simplified models can capture the behaviour of sperm cells. The far-field decay of the fluid flow around the cell is calculated, and compared with a stresslet model. Finally we present some new findings showing how, despite having a relatively small hydrodynamic drag, the sperm cell 'head' has very significant effects on surface accumulation and trajectory.
Multiscale Behavior of Viscous Fluids Dynamics: Experimental Observations
Arciniega-Ceballos, Alejandra; Spina, Laura; Scheu, Bettina; Dingwell, Donald B.
2016-04-01
The dynamics of Newtonian fluids with viscosities of mafic to intermediate silicate melts (10-1000 Pa s) during slow decompression present multi-time scale processes. To observe these processes we have performed several experiments on silicon oil saturated with Argon gas for 72 hours, in a Plexiglas autoclave. The slow decompression, dropping from 10 MPa to ambient pressure, acting as the excitation mechanism, triggered several processes with their own distinct timescales. These processes generate complex non-stationary microseismic signals, which have been recorded with 7 high-dynamic piezoelectric sensors located along the conduit flanked by high-speed video recordings. The analysis in time and frequency of these time series and their correlation with the associated high-speed imaging enables the characterization of distinct phases and the extraction of the individual processes during the evolution of decompression of these viscous fluids. We have observed fluid-solid elastic interaction, degassing, fluid mass expansion and flow, bubble nucleation, growth, coalescence and collapse, foam building and vertical wagging. All these processes (in fine and coarse scales) are sequentially coupled in time, occur within specific pressure intervals, and exhibit a localized distribution along the conduit. Their coexistence and interactions constitute the stress field and driving forces that determine the dynamics of the conduit system. Our observations point to the great potential of this experimental approach in the understanding of volcanic conduit dynamics and volcanic seismicity.
A new scenario of the universe dynamics with interacting fluids
Aydiner, Ekrem
2016-01-01
In this study, I discuss universe dynamics by considering mutual and self-interactions between fluid components such as dark energy, dark, matter etc, in the the spatially flat Friedmann-Robertson-Walker space-time. I show that dynamics of the interacting two-fluid with linear EoS can be given by Lotka-Volterra equations. On the other hand, I show that interacting two-fluid model with quadratic EoS can be transformed to the self-interacting Lotka-Volterra equations. Finally I show that these equations can be generalized to $N$ interacting Lotka-Volterra equations for more interacting fluids. Also I find fixed points of these equations and discuss the dynamics of universe. Even though present model needs to be confirmed experimentally, obtained results clearly show that dynamics of universe at large scale and within the time may have stable, unstable or chaotic behaviour in the presence of the interaction and self-interaction in between dark energy, dark matter, matter and others components of the universe unl...
Fluids as Dynamic Templates for Cytoskeletal Proteins in Plant Cells
Lofthouse, J T
2008-01-01
The Dynamic Template model of biological cell membranes and the cytoplasm as spatially organised fluid layers is extended to plant cells, and is shown to offer a feasible shear driven mechanism for the co-alignment of internal and external fibres observed during growth and tropic responses
Microchannel Emulsification: From Computational Fluid Dynamics to Predictive Analytical Model
Dijke, van K.C.; Schroën, C.G.P.H.; Boom, R.M.
2008-01-01
Emulsion droplet formation was investigated in terrace-based microchannel systems that generate droplets through spontaneous Laplace pressure driven snap-off. The droplet formation mechanism was investigated through high-speed imaging and computational fluid dynamics (CFD) simulation, and we found g
An Assessment of Productive Computational Fluid Dynamics for Aerodynamic Design
2008-01-01
PANAIR [7]) to marching techniques (like ZEUS [8] and parabolized Navier-S tokes codes) and full-field, elliptical, Computational Fluid Dynamics (CFD...undeflected case), but individual representations were required to create each deflection angle for the bent nose configuration. Figure 1. Three
Critical velocity and dynamic respondency of pipe conveying fluid
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Presents the calculation of critical velocity, natural frequencyand dynamic respondency of fluid-conveying pipe are calculated under different boundary conditions using finite element method, and the use of calculation results to design and research rocket pipes feeding fuel and watery turbine pipes conveying water etc.
Direct visualization of fluid dynamics in sub-10 nm nanochannels.
Li, Huawei; Zhong, Junjie; Pang, Yuanjie; Zandavi, Seyed Hadi; Persad, Aaron Harrinarine; Xu, Yi; Mostowfi, Farshid; Sinton, David
2017-07-13
Optical microscopy is the most direct method to probe fluid dynamics at small scales. However, contrast between fluid phases vanishes at ∼10 nm lengthscales, limiting direct optical interrogation to larger systems. Here, we present a method for direct, high-contrast and label-free visualization of fluid dynamics in sub-10 nm channels, and apply this method to study capillary filling dynamics at this scale. The direct visualization of confined fluid dynamics in 8-nm high channels is achieved with a conventional bright-field optical microscope by inserting a layer of a high-refractive-index material, silicon nitride (Si3N4), between the substrate and the nanochannel, and the height of which is accurately controlled down to a few nanometers by a SiO2 spacer layer. The Si3N4 layer exhibits a strong Fabry-Perot resonance in reflection, providing a sharp contrast between ultrathin liquid and gas phases. In addition, the Si3N4 layer enables robust anodic bonding without nanochannel collapse. With this method, we demonstrate the validity of the classical Lucas-Washburn equation for capillary filling in the sub-10 nm regime, in contrast to the previous studies, for both polar and nonpolar liquids, and for aqueous salt solutions.
Modelling Emission from Building Materials with Computational Fluid Dynamics
DEFF Research Database (Denmark)
Topp, Claus; Nielsen, Peter V.; Heiselberg, Per
This paper presents a numerical model that by means of computational fluid dynamics (CFD) is capable of dealing with both pollutant transport across the boundary layer and internal diffusion in the source without prior knowledge of which is the limiting process. The model provides the concentration...
Prospects for Computational Fluid Dynamics in Room Air Contaminant Control
DEFF Research Database (Denmark)
Nielsen, Peter V.
The fluid dynamics research is strongly influenced by the increasing computer power which has been available for the last decades. This development is obvious from the curve in figure 1 which shows the computation cost as a function of years. It is obvious that the cost for a given job...
Computational Fluid Dynamics and Building Energy Performance Simulation
DEFF Research Database (Denmark)
Nielsen, Peter Vilhelm; Tryggvason, T.
1998-01-01
An interconnection between a building energy performance simulation program and a Computational Fluid Dynamics program (CFD) for room air distribution will be introduced for improvement of the predictions of both the energy consumption and the indoor environment. The building energy performance...
Dynamics of complex fluids in rotary atomization
Keshavarz, Bavand; McKinley, Gareth; MIT, Mechanical Engineering Department Team
2016-11-01
We study the dynamics of fragmentation for different Newtonian and viscoelastic liquids in rotary atomization. In this process, at the rim of a spinning cup, the centripetal acceleration destabilizes the formed liquid torus due to the Rayleigh-Taylor instability. The resulting ligaments leave the liquid torus with a remarkably repeatable spacing that scales linearly with the inverse of the rotation rate. Filaments then follow a well-defined geometrical path-line that is described by the involute of the circle. Knowing the geometry of this phenomenon we derive the detailed kinematics of this process and compare it with the experimental observations. We show that the ligaments elongate tangentially to the involute of the circle and thin radially as they separate from the cup. A theoretical form is derived for the spatial variation of the filament deformation rate. Once the ligaments are far from the cup they breakup into droplets since they are not stretched fast enough (compared to the critical rate of capillary thinning). We couple these derivations with the known properties of Newtonian and viscoelastic liquids to provide a physical analysis for this fragmentation process that is compared in detail with our experiments.
DEFF Research Database (Denmark)
Rasmussen, Anders Rønne; Sørensen, Mads Peter; Gaididei, Yuri Borisovich
2008-01-01
A wave equation, that governs nite amplitude acoustic disturbances in a thermoviscous Newtonian fluid, and includes nonlinear terms up to second order, is proposed. In contrast to the model known as the Kuznetsov equation, the proposed nonlinear wave equation preserves the Hamiltonian structure...... of the fundamental fluid dynamical equations in the non-dissipative limit. An exact traveling front solution is obtained from a generalized traveling wave assumption. This solution is, in an overall sense, equivalent to the Taylor shock solution of the Burgers equation. However, in contrast to the Burgers equation...... with respect to the fluid ahead of it, and subsonic speed with respect to the fluid behind it, similarly to the fluid dynamical shock. Linear stability analysis reveals that the front is stable when the acoustic pressure belongs to a critical interval, and is otherwise unstable. These results are veried...
Front structure and dynamics in dense colonies of motile bacteria: Role of active turbulence
Chatterjee, Rayan; Perlekar, Prasad
2016-01-01
We study the spreading of a bacterial colony undergoing turbulent like collective motion. We present two minimalistic models to investigate the interplay between population growth and coherent structures arising from turbulence. Using Direct Numerical Simulation (DNS) of the proposed models we find that turbulence has two prominent effects on the spatial growth of the colony: (a) the front speed is enhanced, and (b) the front gets crumpled. Both these effects, which we highlight by using statistical tools, are markedly different in our two models. We also show that the crumpled front structure and the passive scalar fronts in random flows are related in certain regimes.
Numerical simulation of particle dynamics at a fluid interface
Yue, Pengtao
2016-11-01
Particles straddling a fluid interface exhibit rich dynamics due to the coexistence of moving boundaries, fluid interfaces, and moving contact lines. For instance, as a particle falls onto a liquid surface, it may sink, float, or even bounce off depending on a wide range of parameters. To better understand the dynamics of such a multiphase system, we develop a finite-element based arbitrary Lagrangian-Eulerian-phase-field method. The governing equations for particles and fluids are solved in a unified variational framework that satisfies an energy law. We first validate our code by computing three problems found in literature: sinking of a horizontal cylinder through an air-water interface, sinking of a sphere through an air-oil interface at small Reynolds numbers, and bouncing of a sphere after its normal impact onto an air-water interface. Our numerical results show good agreements with experimental data. We then investigate the effect of wetting properties, including static contact angle, slip length, and wall energy relaxation, on particle dynamics at the fluid interface. This work is supported by NSF DMS-1522604.
Unsteady bio-fluid dynamics in flying and swimming
Liu, Hao; Kolomenskiy, Dmitry; Nakata, Toshiyuki; Li, Gen
2017-08-01
Flying and swimming in nature present sophisticated and exciting ventures in biomimetics, which seeks sustainable solutions and solves practical problems by emulating nature's time-tested patterns, functions, and strategies. Bio-fluids in insect and bird flight, as well as in fish swimming are highly dynamic and unsteady; however, they have been studied mostly with a focus on the phenomena associated with a body or wings moving in a steady flow. Characterized by unsteady wing flapping and body undulation, fluid-structure interactions, flexible wings and bodies, turbulent environments, and complex maneuver, bio-fluid dynamics normally have challenges associated with low Reynolds number regime and high unsteadiness in modeling and analysis of flow physics. In this article, we review and highlight recent advances in unsteady bio-fluid dynamics in terms of leading-edge vortices, passive mechanisms in flexible wings and hinges, flapping flight in unsteady environments, and micro-structured aerodynamics in flapping flight, as well as undulatory swimming, flapping-fin hydrodynamics, body-fin interaction, C-start and maneuvering, swimming in turbulence, collective swimming, and micro-structured hydrodynamics in swimming. We further give a perspective outlook on future challenges and tasks of several key issues of the field.
Fluid dynamics of the shock wave reactor
Masse, Robert Kenneth
2000-10-01
High commercial incentives have driven conventional olefin production technologies to near their material limits, leaving the possibility of further efficiency improvements only in the development of entirely new techniques. One strategy known as the Shock Wave Reactor, which employs gas dynamic processes to circumvent limitations of conventional reactors, has been demonstrated effective at the University of Washington. Preheated hydrocarbon feedstock and a high enthalpy carrier gas (steam) are supersonically mixed at a temperature below that required for thermal cracking. Temperature recovery is then effected via shock recompression to initiate pyrolysis. The evolution to proof-of-concept and analysis of experiments employing ethane and propane feedstocks are presented. The Shock Wave Reactor's high enthalpy steam and ethane flows severely limit diagnostic capability in the proof-of-concept experiment. Thus, a preliminary blow down supersonic air tunnel of similar geometry has been constructed to investigate recompression stability and (especially) rapid supersonic mixing necessary for successful operation of the Shock Wave Reactor. The mixing capabilities of blade nozzle arrays are therefore studied in the air experiment and compared with analytical models. Mixing is visualized through Schlieren imaging and direct photography of condensation in carbon dioxide injection, and interpretation of visual data is supported by pressure measurement and flow sampling. The influence of convective Mach number is addressed. Additionally, thermal behavior of a blade nozzle array is analyzed for comparison to data obtained in the course of succeeding proof-of-concept experiments. Proof-of-concept is naturally succeeded by interest in industrial adaptation of the Shock Wave Reactor, particularly with regard to issues involving the scaling and refinement of the shock recompression. Hence, an additional, variable geometry air tunnel has been constructed to study the parameter
Directory of Open Access Journals (Sweden)
Fanny Mondet
2014-08-01
Full Text Available Over the past fifty years, annual honeybee (Apis mellifera colony losses have been steadily increasing worldwide. These losses have occurred in parallel with the global spread of the honeybee parasite Varroa destructor. Indeed, Varroa mite infestations are considered to be a key explanatory factor for the widespread increase in annual honeybee colony mortality. The host-parasite relationship between honeybees and Varroa is complicated by the mite's close association with a range of honeybee viral pathogens. The 10-year history of the expanding front of Varroa infestation in New Zealand offered a rare opportunity to assess the dynamic quantitative and qualitative changes in honeybee viral landscapes in response to the arrival, spread and level of Varroa infestation. We studied the impact of de novo infestation of bee colonies by Varroa on the prevalence and titres of seven well-characterised honeybee viruses in both bees and mites, using a large-scale molecular ecology approach. We also examined the effect of the number of years since Varroa arrival on honeybee and mite viral titres. The dynamic shifts in the viral titres of black queen cell virus and Kashmir bee virus mirrored the patterns of change in Varroa infestation rates along the Varroa expansion front. The deformed wing virus (DWV titres in bees continued to increase with Varroa infestation history, despite dropping infestation rates, which could be linked to increasing DWV titres in the mites. This suggests that the DWV titres in mites, perhaps boosted by virus replication, may be a major factor in maintaining the DWV epidemic after initial establishment. Both positive and negative associations were identified for several pairs of viruses, in response to the arrival of Varroa. These findings provide important new insights into the role of the parasitic mite Varroa destructor in influencing the viral landscape that affects honeybee colonies.
Mondet, Fanny; de Miranda, Joachim R; Kretzschmar, Andre; Le Conte, Yves; Mercer, Alison R
2014-08-01
Over the past fifty years, annual honeybee (Apis mellifera) colony losses have been steadily increasing worldwide. These losses have occurred in parallel with the global spread of the honeybee parasite Varroa destructor. Indeed, Varroa mite infestations are considered to be a key explanatory factor for the widespread increase in annual honeybee colony mortality. The host-parasite relationship between honeybees and Varroa is complicated by the mite's close association with a range of honeybee viral pathogens. The 10-year history of the expanding front of Varroa infestation in New Zealand offered a rare opportunity to assess the dynamic quantitative and qualitative changes in honeybee viral landscapes in response to the arrival, spread and level of Varroa infestation. We studied the impact of de novo infestation of bee colonies by Varroa on the prevalence and titres of seven well-characterised honeybee viruses in both bees and mites, using a large-scale molecular ecology approach. We also examined the effect of the number of years since Varroa arrival on honeybee and mite viral titres. The dynamic shifts in the viral titres of black queen cell virus and Kashmir bee virus mirrored the patterns of change in Varroa infestation rates along the Varroa expansion front. The deformed wing virus (DWV) titres in bees continued to increase with Varroa infestation history, despite dropping infestation rates, which could be linked to increasing DWV titres in the mites. This suggests that the DWV titres in mites, perhaps boosted by virus replication, may be a major factor in maintaining the DWV epidemic after initial establishment. Both positive and negative associations were identified for several pairs of viruses, in response to the arrival of Varroa. These findings provide important new insights into the role of the parasitic mite Varroa destructor in influencing the viral landscape that affects honeybee colonies.
A Dynamical System Analysis of Three Fluid cosmological Model
Mahata, Nilanjana
2015-01-01
In Friedman-Robertson-Walker flat spacetime, we consider a three fluid cosmological model which contains dark matter, dark energy and baryonic matter in the form of perfect fluid with a barotropic equation of state. Dark matter is taken in form of dust and dark energy is described by a scalar field with a potential $V(\\phi)$. Einstein's field equations are reduced to an autonomous dynamical system by suitable redefinition of basic variables. Considering exponential potential for the scalar field, critical points are obtained for the autonomous system. Finally stability of the critical points and cosmological implications are analyzed.
Wan, Yuanyang; Roelvink, Dano; Li, Weihua; Qi, Dingman; Gu, Fengfeng
2014-07-01
Observations of storm-induced fluid mud dynamics have been conducted at the North Passage deepwater navigational channel (DNC) of the Yangtze Estuary in October to December 2010, during the occurrence of a cold-air front. The measurement data reveal that just after the critical wind wave event, a large amount of fine sediment was trapped in a state of fluid mud along the channel. The observed thickness of the fluid mud was up to about 1-5 m, which caused some significant economic and safety problems for shipping traffic in the Yangtze Delta area. The mechanisms and transport processes of the storm-induced fluid mud are analyzed and presented from the angles of both process-oriented and engineering-oriented methods. With the help of hydrodynamics and wave modeling, it could be inferred that the behavior of the storm-induced fluid mud event mainly depends on the overall hydrodynamic regimes and the exchanges of sediment, which is released by storm-wave agitation from adjacent tidal flats. These sediments are accumulated as fluid mud, and subsequently oscillate and persist at those locations with weaker longitudinal residuals in the river- and tide-dominated estuary. In addition, the downslope transport of fluid mud is also thought to have stimulated and worsened the fluid mud event observed in this study. Our modeling results and observations demonstrate that: (1) the transport of fluid mud is an advective phenomenon determining the central position of fluid mud layer along the channel, and it's also a tidal energy influenced phenomenon controlling the erosion and accumulation of fluid mud; and (2) both suspended particulate matter availability and local residual flow regime are of critical importance in determining the trapping probability of sediment and the occurrence of fluid mud.
Self-gravitating fluid solutions of Shape Dynamics
Guariento, Daniel C
2016-01-01
Shape Dynamics is a 3D conformally invariant theory of gravity which possesses a large set of solutions in common with General Relativity. When looked closely, these solutions are found to behave in surprising ways, so in order to probe the fitness of Shape Dynamics as a viable alternative to General Relativity one must find and understand increasingly more complex, less symmetrical exact solutions, on which to base perturbative studies and numerical analyses in order to compare them with data. Spherically symmetric exact solutions have been studied, but only in a static vacuum setup. In this work we construct a class of time-dependent exact solutions of Shape Dynamics from first principles, representing a central inhomogeneity in an evolving cosmological environment. By assuming only a perfect fluid source in a spherically symmetric geometry we show that this fully dynamic non-vacuum solution satisfies in all generality the Hamiltonian structure of Shape Dynamics. The simplest choice of solutions is shown to...
Dynamics of a faceted nematic-smectic-B front in thin-sample directional solidification.
Börzsönyi, T; Akamatsu, S; Faivre, G
2002-01-01
We present an experimental study of the directional-solidification patterns of a nematic-smectic-B front. The chosen system is C4H9-(C6H10)2CN (in short, CCH4) in 12 microm-thick samples, and in the planar configuration (director parallel to the plane of the sample). The nematic-smectic-B interface presents a facet in one direction-the direction parallel to the smectic layers--and is otherwise rough and devoid of forbidden directions. We measure the Mullins-Sekerka instability threshold and establish the morphology diagram of the system as a function of the solidification rate V and the angle straight theta(0) between the facet and the isotherms. We focus on the phenomena occurring immediately above the instability threshold when straight theta(0) is neither very small nor close to 90 degrees. Under these conditions, we observe drifting shallow cells and a type of solitary wave, called "faceton," which consists essentially of an isolated macroscopic facet traveling laterally at such a velocity that its growth rate with respect to the liquid is small. Facetons may propagate either in a stationary or an oscillatory way. The detailed study of their dynamics casts light on the microscopic growth mechanisms of the facets in this system.
Computational fluid dynamics modeling of a lithium/thionyl chloride battery with electrolyte flow
Energy Technology Data Exchange (ETDEWEB)
Gu, W.B.; Wang, C.Y.; Weidner, J.W.; Jungst, R.G.; Nagasubramanian, G.
2000-02-01
A two-dimensional model is developed to simulate discharge of a lithium/thionyl chloride primary battery. As in earlier one-dimensional models, the model accounts for transport of species and charge, and electrode porosity variations and electrolyte flow induced by the volume reduction caused by electrochemical reactions. Numerical simulations are performed using a finite volume method of computational fluid dynamics. The predicted discharge curves for various temperatures show good agreement with published experimental data, and are essentially identical to results published for one-dimensional models. The detailed two-dimensional flow simulations show that the electrolyte is replenished from the cell head space predominantly through the separator into the front of the cathode during most parts of the discharge, especially for higher cell temperatures.
Computational Fluid Dynamics in Solid Earth Sciences–a HPC challenge
Directory of Open Access Journals (Sweden)
Luminita Zlagnean
2012-11-01
Full Text Available Presently, the Solid Earth Sciences started to move towards implementing High Performance Computational (HPC research facilities. One of the key tenants of HPC is performance, which strongly depends on the interaction between software and hardware. In this paper, they are presented benchmark results from two HPC systems. Testing a Computational Fluid Dynamics (CFD code specific for Solid Earth Sciences, the HPC system Horus, based on Gigabit Ethernet, performed reasonably well compared with its counterpart CyberDyn, based on Infiniband QDR fabric. However, the HPCC CyberDyn based on low-latency high-speed QDR network dedicated to MPI traffic outperformed the HPCC Horus. Due to the high-resolution simulations involved in geodynamic research studies, HPC facilities used in Earth Sciences should benefit from larger up-front investment in future systems that are based on high-speed interconnects.
Use of computational fluid dynamics in respiratory medicine.
Fernández Tena, Ana; Casan Clarà, Pere
2015-06-01
Computational Fluid Dynamics (CFD) is a computer-based tool for simulating fluid movement. The main advantages of CFD over other fluid mechanics studies include: substantial savings in time and cost, the analysis of systems or conditions that are very difficult to simulate experimentally (as is the case of the airways), and a practically unlimited level of detail. We used the Ansys-Fluent CFD program to develop a conducting airway model to simulate different inspiratory flow rates and the deposition of inhaled particles of varying diameters, obtaining results consistent with those reported in the literature using other procedures. We hope this approach will enable clinicians to further individualize the treatment of different respiratory diseases.
Optics and Fluid Dynamics Department annual progress report for 1996
Energy Technology Data Exchange (ETDEWEB)
Hanson, S.G.; Johansen, P.M.; Lading, L.; Lynov, J.P.; Skaarup, B. [eds.
1997-01-01
Research in the Optics and Fluid Dynamics Department has been performed within the following three programme areas: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The work is concentrated on combinations of systems, structures and materials. The systems work is focused on sensors, information processing an storage; the structures work is concentrated on pattern formation and diffractive elements; the materials work is centred on the understanding and utilisation of nonlinear phenomena. Scientific computing is an integral part of the work. The activities are supported by several EU programmes, including EURATOM, by research councils and by industry. A summary of the activities in 1996 is presented. (au) 53 ills., 232 refs.
Computational Fluid and Particle Dynamics in the Human Respiratory System
Tu, Jiyuan; Ahmadi, Goodarz
2013-01-01
Traditional research methodologies in the human respiratory system have always been challenging due to their invasive nature. Recent advances in medical imaging and computational fluid dynamics (CFD) have accelerated this research. This book compiles and details recent advances in the modelling of the respiratory system for researchers, engineers, scientists, and health practitioners. It breaks down the complexities of this field and provides both students and scientists with an introduction and starting point to the physiology of the respiratory system, fluid dynamics and advanced CFD modeling tools. In addition to a brief introduction to the physics of the respiratory system and an overview of computational methods, the book contains best-practice guidelines for establishing high-quality computational models and simulations. Inspiration for new simulations can be gained through innovative case studies as well as hands-on practice using pre-made computational code. Last but not least, students and researcher...
Optics and Fluid Dynamics Department annual progress report for 1997
Energy Technology Data Exchange (ETDEWEB)
Hanson, S.G.; Johansen, P.M.; Lading, L.; Lynov, J.P.; Skaarup, B. [eds.
1998-04-01
Research in the Optics and Fluid Dynamics Department has been performed within the following three programme areas: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The work is concentrated on combinations of systems, structures and materials. The systems work is focused on sensors, information processing and storage; the structures work is concentrated on pattern formation and diffractive elements; the materials work is centred on the understanding and utilisation of nonlinear phenomena for optical components and systems. Scientific computing is an integral part of the work. Biomedical optics is a new activity and the work on polymer optics is enhanced considerably. The activities are supported by several EU programmes, including EURATOM, by research councils and by industry. A summary of the activities in 1997 is presented. (au) 1 tab., 63 ills., 249 refs.
Quantifying Chiral Magnetic Effect from Anomalous-Viscous Fluid Dynamics
Jiang, Yin; Yin, Yi; Liao, Jinfeng
2016-01-01
Chiral Magnetic Effect (CME) is the macroscopic manifestation of the fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as anomalous transport current in the fluid dynamics framework. Experimental observation of CME is of great interest and has been reported in Dirac and Weyl semimetals. Significant efforts have also been made to search for CME in heavy ion collisions. Encouraging evidence of CME-induced charge separation in those collisions has been reported, albeit with ambiguity due to background contamination. Crucial for addressing such issue, is the need of quantitative predictions for CME signal with sophisticated modelings. In this paper we develop such a tool, the Anomalous Viscous Fluid Dynamics (AVFD) framework, which simulates the evolution of fermion currents in QGP on top of the data-validated VISHNU bulk hydrodynamic flow. With realistic initial conditions and magnetic field lifetime, the AVFD-predicted CME signal could be quantitatively consistent with measured ch...
Lily Pad: Towards Real-time Interactive Computational Fluid Dynamics
Weymouth, Gabriel D
2015-01-01
Despite the fact that computational fluid dynamics (CFD) software is now (relatively) fast and freely available, it is still amazingly difficult to use. Inaccessible software imposes a significant entry barrier on students and junior engineers, and even senior researchers spend less time developing insights and more time on software issues. Lily Pad was developed as an initial attempt to address some of these problems. The goal of Lily Pad is to lower the barrier to CFD by adopting simple high-speed methods, utilising modern programming features and environments, and giving immediate visual feed-back to the user. The resulting software focuses on the fluid dynamics instead of the computation, making it useful for both education and research. LilyPad is open source and available online at https://github.com/weymouth/lily-pad for all use under the MIT license.
Streaming potential-modulated capillary filling dynamics of immiscible fluids.
Bandopadhyay, Aditya; Mandal, Shubhadeep; Chakraborty, Suman
2016-02-21
The pressure driven transport of two immiscible electrolytes in a narrow channel with prescribed surface potential (zeta potential) is considered under the influence of a flow-induced electric field. The latter consideration is non-trivially and fundamentally different from the problem of electric field-driven motion (electroosmosis) of two immiscible electrolytes in a channel in a sense that in the former case, the genesis of the induced electric field, termed as streaming potential, is the advection of ions in the absence of any external electric field. As the flow occurs, one fluid displaces the other. Consequently, in cases where the conductivities of the two fluids differ, imbibition dynamically alters the net conductivity of the channel. We emphasize, through numerical simulations, that the alteration in the net conductivity has a significant impact on the contact line dynamics and the concomitant induced streaming potential. The results presented herein are expected to shed light on multiphase electrokinetics devices.
Fluid-dynamical aspects of laser-metal interaction
Cantello, M.; Menin, R.; Donati, V.; Garifo, L.; La Rocca, A. V.; Onorato, M.
During the interaction of a high-power laser beam with a material surface many fluid-dynamical phenomena arise. The produced flow field interacts with the beam and affects the thermal coupling between the laser energy and the target metal. In this paper the fluid-dynamical aspects of these phenomena are discussed and new experimental results are illustrated. The experiments have been performed in conditions of interest for industrial laser processes with a 15-kW CW CO2 laser. The development and the motion of bright clouds ignited from metal targets at incident laser power up to 11.6 kW, using an f/18 focusing system, have been studied by high speed photographic records. The properties of the cloud have been examined by spectroscopic analysis and absorption measurements.
Fluid Dynamic Field in Bozhong Depression, Bohai Bay Basin
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The data from regional geology, boreholes, geophysics and tests are integrated to analyze the fluid dynamic field in the Bozhong depression, Bohai Bay basin. The current geothermal gradient is determined to be about 2.95 ℃/100 m by integrating 266 drill-stem test (DST) measurements and comparing with the global average value. The paleogeothermal gradients are calculated from the homogenization temperatures of saline inclusions, which vary both laterally and vertically. The data from sonic logs, well tests and seismic velocities are used to investigate the pressure variations in the study area. The mudstone compaction is classified as three major types: normal compaction and normal pressure, under-compaction and overpressure, and past-compaction and under-overpressure. The current pressure profile is characterized by normal pressure, slight pressure and intense overpressure from top to bottom. The faults, unconformity surfaces and interconnecting pores constitute a complex network of vertical and horizontal fluid flows within the depression. The fluid potential energy profiles present a “double-deck” structure. The depocenters are the area of fluids supply, whereas the slopes and uplifts are the main areas of fluids charge.
Stochastic Euler Equations of Fluid Dynamics with Lvy Noise
2016-08-10
Asymptotic Analysis 99 (2016) 67–103 67 DOI 10.3233/ASY-161376 IOS Press Stochastic Euler equations of fluid dynamics with Lévy noise Manil T. Mohan...References [1] D. Applebaum, Lévy Processes and Stochastic Calculus , Cambridge Studies in Advanced Mathematics, Vol. 93, Cam- bridge University Press...2004. [2] H. Bessaih and F. Flandoli, 2-D Euler equation perturbed by noise, Nonlinear Differential Equations and Applications 6 (1998), 35–54. doi
Computational Fluid Dynamics. [numerical methods and algorithm development
1992-01-01
This collection of papers was presented at the Computational Fluid Dynamics (CFD) Conference held at Ames Research Center in California on March 12 through 14, 1991. It is an overview of CFD activities at NASA Lewis Research Center. The main thrust of computational work at Lewis is aimed at propulsion systems. Specific issues related to propulsion CFD and associated modeling will also be presented. Examples of results obtained with the most recent algorithm development will also be presented.
Quality control of computational fluid dynamics in indoor environments
DEFF Research Database (Denmark)
Sørensen, Dan Nørtoft; Nielsen, P. V.
2003-01-01
Computational fluid dynamics (CFD) is used routinely to predict air movement and distributions of temperature and concentrations in indoor environments. Modelling and numerical errors are inherent in such studies and must be considered when the results are presented. Here, we discuss modelling as...... the quality of CFD calculations, as well as guidelines for the minimum information that should accompany all CFD-related publications to enable a scientific judgment of the quality of the study....
Optics and fluid dynamics department annual progress report for 1994
Energy Technology Data Exchange (ETDEWEB)
Hanson, S.G.; Lading, L.; Lynov, J.P.; Michelsen, P.
1995-01-01
Research in the Optics and Fluid Dynamics Department is performed within the following two programme areas: optics and continuum physics. In optics the activities are within (a) optical materials and electromagnetic propagation, (b) diagnostics and sensors, and (c) information processing. In continuum physics the activities are (a) nonlinear dynamics and (b) computer physics. The activities are supported by several EU programmes, including EURATOM, by research councils, and by industry. A special activity is the implementation of pellet injectors for fusion research. A summary of activities in 1994 is presented. (au) (27 ills., 44 refs.).
On the Dynamical Response of the Subarctic Front to Momentum Transfer.
1981-03-01
MAR 81 A CAMERLEN N0001-75-C-0201UNLASSIFIED 180 N2flnlflllllUf nmhEEEEEEEmnhE EEEEEEmmEEmmEE mmImmmmmEEEEEEE EmEEEEEEEEmmEE EmmEmmEEmmEEEEmhmmmmmu...the undulatory front for the case of the cyclone travelling from west to east after 10 days. viii ix Fig. 18. Circumference of equation lYr - 12 + y2...forms. In the first case, the front will be parallel to the latitudinal circles, while in the second instance the front will have an undulatory initial
A numerical model for dynamic crustal-scale fluid flow
Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel
2015-04-01
Fluid flow in the crust is often envisaged and modeled as continuous, yet minimal flow, which occurs over large geological times. This is a suitable approximation for flow as long as it is solely controlled by the matrix permeability of rocks, which in turn is controlled by viscous compaction of the pore space. However, strong evidence (hydrothermal veins and ore deposits) exists that a significant part of fluid flow in the crust occurs strongly localized in both space and time, controlled by the opening and sealing of hydrofractures. We developed, tested and applied a novel computer code, which considers this dynamic behavior and couples it with steady, Darcian flow controlled by the matrix permeability. In this dual-porosity model, fractures open depending on the fluid pressure relative to the solid pressure. Fractures form when matrix permeability is insufficient to accommodate fluid flow resulting from compaction, decompression (Staude et al. 2009) or metamorphic dehydration reactions (Weisheit et al. 2013). Open fractures can close when the contained fluid either seeps into the matrix or escapes by fracture propagation: mobile hydrofractures (Bons, 2001). In the model, closing and sealing of fractures is controlled by a time-dependent viscous law, which is based on the effective stress and on either Newtonian or non-Newtonian viscosity. Our simulations indicate that the bulk of crustal fluid flow in the middle to lower upper crust is intermittent, highly self-organized, and occurs as mobile hydrofractures. This is due to the low matrix porosity and permeability, combined with a low matrix viscosity and, hence, fast sealing of fractures. Stable fracture networks, generated by fluid overpressure, are restricted to the uppermost crust. Semi-stable fracture networks can develop in an intermediate zone, if a critical overpressure is reached. Flow rates in mobile hydrofractures exceed those in the matrix porosity and fracture networks by orders of magnitude
Review of Recent Results in Heavy Ion Fluid Dynamics
Directory of Open Access Journals (Sweden)
Csernai Laszlo P.
2014-03-01
Full Text Available Fluid dynamical phenomena in high energy heavy ion reactions were predicted in the 1970s and still today these are the most dominant and basic observables. With increasing energy and the reach of QGP the low viscosity of the plasma became apparent and this brought a new revolution in the fluid dynamical studies. The high energy and low viscosity made it possible to observe fluctuations up to high multipolarity flow harmonics. This is an obvious, direct proof of the low viscosity of QGP. Many aspects of these fluctuations are under intensive study today. The low viscosity opened ways to observe special fluid dynamical turbulent phenomena. These may arise from random fluctuations, as well as from the global symmetries of peripheral collisions. At LHC energies the angular momentum of the participant matter can reach 106ħ, which leads to rotation and turbulent instabilities, like the Kelvin-Helmholtz instability. Low viscosity ensures that these remain observable at the final freeze-out stages of the collision. Thus new investigations in addition to the standard flow analysis methods became possible. Femtoscopy may also detect rotation and turbulence. Due to the high local thermal vorticity, particle polarization and orbital rotation may reach thermal and mechanical equilibrium. This leads to baryon polarization which, in given directions may be detectable.
Aquatic and Sedimentary N-Isotope Dynamics in the Danube Delta Front
Möbius, Jürgen; Dähnke, Kirstin
2014-05-01
The North-Western Black Sea Shelf Region suffered from severe eutrophication in the past decades, mainly due to increased nutrient loads of the Danube River, the most important contributor of freshwater to this brackish sea. It is yet unclear whether the Black Sea shelf is at present on the way to recovery due to a recent decrease in nutrient discharge from the Danube River. During 2 cruises in summer and spring 2013 in the Danube River Delta/Black Sea transition zone, we analysed dissolved nutrients, and nitrate (and oxygen) isotope signatures in nitrate, suspended particulate matter, surface sediment and a sediment core from the shelf. Our rationale was two-fold: Firstly, we aimed to investigate N turnover and nutrient dynamics in the present Black Sea Shelf region to assess the effect of contemporary nutrient loads of the River Danube, and secondly, we wanted to compare these findings to the past situation as captured in the sediment record. Our data indicate intense draw-down of river-borne dissolved silica and phosphate in the transition zone, up to nutrient depletion in mesohaline waters in summer. Surprisingly, nitrate concentration follows a conservative mixing line. Despite this apparent conservative mixing of river nitrate with marine water, nitrate isotope trends confirm the importance of biological nitrate assimilation in the water column. Moreover, the relative enrichment of O to N isotopes in nitrate, following an unexpectedly steep slope of 2, suggests that this uptake cannot only be due to phytoplankton activity, which usually plots along a slope of 1. We accordingly investigated the potential effects of different nitrate turnover processes and specifically nitrate regeneration on its isotopic composition. Furthermore, notwithstanding significant nutrient input via benthic nutrient recycling, the N-isotope trend of sediment cores furthermore seems to provide a first hint towards improved water quality in the Danube Delta Front Region, possibly due
Brodsky, S. J.
2017-07-01
A fundamental problem in hadron physics is to obtain a relativistic color-confining, first approximation to QCD which can predict both hadron spectroscopy and the frame-independent light-front (LF) wavefunctions underlying hadron dynamics. The QCD Lagrangian with zero quark mass has no explicit mass scale; the classical theory is conformally invariant. Thus, a fundamental problem is to understand how the mass gap and ratios of masses - such as m ρ/m p - can arise in chiral QCD. De Alfaro, Fubini, and Furlan have made an important observation that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator and rescales the time variable. If one applies the same procedure to the light-front Hamiltonian, it leads uniquely to a confinement potential κ 4 ζ 2 for mesons, where ζ 2 is the LF radial variable conjugate to the q\\overline{q} invariant mass squared. The same result, including spin terms, is obtained using light-front holography - the duality between light-front dynamics and AdS5, the space of isometries of the conformal group if one modifies the action of AdS5 by the dilaton {e}^{κ^2}{z}^2 in the fifth dimension z . When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions predict unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons of the same parity. One also predicts observables such as hadron structure functions, transverse momentum distributions, and the distribution amplitudes defined from the hadronic light-front wavefunctions. The mass scale κ underlying confinement and hadron masses can be connected to the parameter {Λ}_{\\overline{MS}} in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The
Issues in computational fluid dynamics code verification and validation
Energy Technology Data Exchange (ETDEWEB)
Oberkampf, W.L.; Blottner, F.G.
1997-09-01
A broad range of mathematical modeling errors of fluid flow physics and numerical approximation errors are addressed in computational fluid dynamics (CFD). It is strongly believed that if CFD is to have a major impact on the design of engineering hardware and flight systems, the level of confidence in complex simulations must substantially improve. To better understand the present limitations of CFD simulations, a wide variety of physical modeling, discretization, and solution errors are identified and discussed. Here, discretization and solution errors refer to all errors caused by conversion of the original partial differential, or integral, conservation equations representing the physical process, to algebraic equations and their solution on a computer. The impact of boundary conditions on the solution of the partial differential equations and their discrete representation will also be discussed. Throughout the article, clear distinctions are made between the analytical mathematical models of fluid dynamics and the numerical models. Lax`s Equivalence Theorem and its frailties in practical CFD solutions are pointed out. Distinctions are also made between the existence and uniqueness of solutions to the partial differential equations as opposed to the discrete equations. Two techniques are briefly discussed for the detection and quantification of certain types of discretization and grid resolution errors.
Frederico, Tobias; Pace, Emanuele; Salme`, Giovanni
2010-01-01
The electromagnetic properties of the deuteron are investigated within a Light-Front Hamiltonian Dynamics framework, with a current operator that contains both one-body and two-body contributions. In this work, we are considering new two-body contributions, with a dynamical nature generated within a Yukawa model and a structure inspired by a recent analysis of the current operator, that acts on the three-dimensional valence component and fulfills the Ward-Takahashi identity. Preliminary results for the magnetic moment are shown.
Moon, Ji Young; Suh, Dae Chul; Lee, Yong Sang; Kim, Young Woo; Lee, Joon Sang
2014-02-01
Despite recent development of computational fluid dynamics (CFD) research, analysis of computational fluid dynamics of cerebral vessels has several limitations. Although blood is a non-Newtonian fluid, velocity and pressure fields were computed under the assumptions of incompressible, laminar, steady-state flows and Newtonian fluid dynamics. The pulsatile nature of blood flow is not properly applied in inlet and outlet boundaries. Therefore, we present these technical limitations and discuss the possible solution by comparing the theoretical and computational studies.
Bandopadhyay, Aditya; Le Borgne, Tanguy; Méheust, Yves; Dentz, Marco
2017-02-01
Mixing fronts, where fluids of different chemical compositions mix with each other, are known to represent hotspots of chemical reaction in hydrological systems. These fronts are typically subjected to velocity gradients, ranging from the pore scale due to no slip boundary conditions at fluid solid interfaces, to the catchment scale due to permeability variations and complex geometry of the Darcy velocity streamlines. A common trait of these processes is that the mixing interface is strained by shear. Depending on the Péclet number Pe , which represents the ratio of the characteristic diffusion time to the characteristic shear time, and the Damköhler number Da , which represents the ratio of the characteristic diffusion time to the characteristic reaction time, the local reaction rates can be strongly impacted by the dynamics of the mixing interface. So far, this impact has been characterized mostly either in kinetics-limited or in mixing-limited conditions, that is, for either low or high Da. Here the coupling of shear flow and chemical reactivity is investigated for arbitrary Damköhler numbers, for a bimolecular reaction and an initial interface with separated reactants. Approximate analytical expressions for the global production rate and reactive mixing scale are derived based on a reactive lamella approach that allows for a general coupling between stretching enhanced mixing and chemical reactions. While for Pe stretching effects are decoupled, a scenario which we name "weak stretching", for Pe > Da , we uncover a "strong stretching" scenario where new scaling laws emerge from the interplay between reaction kinetics, diffusion, and stretching. The analytical results are validated against numerical simulations. These findings shed light on the effect of flow heterogeneity on the enhancement of chemical reaction and the creation of spatially localized hotspots of reactivity for a broad range of systems ranging from kinetic limited to mixing limited situations.
Gauge/Gravity Duality and Strongly Coupled Light-Front Dynamics
Energy Technology Data Exchange (ETDEWEB)
de Teramond, Guy F.; /Costa Rica U.; Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins
2011-08-12
We find a correspondence between semiclassical gauge theories quantized on the light-front and a dual gravity model in anti-de Sitter (AdS) space, thus providing an initial approximation to QCD in its strongly coupled regime. This correspondence - light-front holography - leads to a light-front Hamiltonian and relativistic bound-state wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. Light-front holography also allows a precise mapping of transition amplitudes from AdS to physical space-time. In contrast with the usual AdS/QCD framework, the internal structure of hadrons is explicitly introduced in the gauge/gravity correspondence and the angular momentum of the constituents plays a key role. We also discuss how to introduce higher Fock-states in the correspondence as well as their relevance for describing the detailed structure of space and time-like form factors.
Low-Beta MHD Reconnection As a Showcase of Compressible Fluid Dynamics
Zenitani, S.
2014-12-01
In the solar corona, in the magnetosphere, and in other astrophysical settings, magnetic reconnection often occurs in a low-beta plasma. Unfortunately, less is known about low-beta reconnection, partially due to lack of attention and partially due to numerical difficulties. Recent MHD simulations revealed several new features of low-beta reconnection; For example, Zenitani et al.(2010,2011) [1,2] discovered a normal shock which is perpendicular to the Petschek shock and a repeated shock-reflection in front of a magnetic island. In this contribution, we extend earlier works with improved MHD codes and organize the results from the perspective of compressible fluid dynamics. In fluid dynamics, once a flow speed becomes comparable with the local sound speed, various compressible effects take place. This is the case for low-beta reconnection, because an Alfvenic reconnection jet becomes supersonic. Many phenomena can be understood as compressible fluid effects: the normal shock is equivalent to a recompression shock on a transonic airfoil, the shock-reflection corresponds to shock-diamonds in an over-expanded supersonic flow, the adiabatic acceleration similarly takes place as the Laval nozzle, and so on. They appear regardless of Sweet-Parker, plasmoid-mediated, or Petschek reconnections. We further discover another shock-diamonds in extreme cases. A critical condition for these hidden shocks is derived. All these issues can be applied to more extreme cases of relativistic reconnection, in which the sound speed is ``relatively'' slow. We will also address the relevance to the physics of extragalactic jets. References:[1] Zenitani, Hesse, & Klimas, ApJ, 716, L214 (2010).[2] Zenitani and Miyoshi, Phys. Plasmas, 18, 022105 (2011).
Dynamical fluid-type Universe scenario with dust and radiation
Mihu, Denisa-Andreea
2016-01-01
Within the context of a cosmic space whose energy source is modeled with a perfect fluid, a uniform model of Universe based on a standard FRW cosmology containing decoupled mixed matter sources namely stiff matter and cosmic dust together with a positive cosmological constant, has been studied. Within the scenario of a $k=0-$ spatially-flat geometry, we analysed the geometrodynamics of the theoretical cosmology. For the model with an added cosmological constant, the main scope was to point out the effects of it on the universe' dynamics. In this last case, the thermodynamics of the model was also considered together with the relation between the cosmological energy density and fluid pressure in terms of the inverse function of the equation of state.
Computational Fluid Dynamics Simulation of Multiphase Flow in Structured Packings
Directory of Open Access Journals (Sweden)
Saeed Shojaee
2012-01-01
Full Text Available A volume of fluid multiphase flow model was used to investigate the effective area and the created liquid film in the structured packings. The computational results revealed that the gas and liquid flow rates play significant roles in the effective interfacial area of the packing. In particular, the effective area increases as the flow rates of both phases increase. Numerical results were compared with the Brunazzi and SRP models, and a good agreement between them was found. Attention was given to the process of liquid film formation in both two-dimensional (2D and three-dimensional (3D models. The current study revealed that computational fluid dynamics (CFD can be used as an effective tool to provide information on the details of gas and liquid flows in complex packing geometries.
Two-fluid Dynamics in Clusters of Galaxies
Institute of Scientific and Technical Information of China (English)
Yu-Qing Lou
2005-01-01
We develop a theoretical formulation for the large-scale dynamics of galaxy clusters involving two spherical ‘isothermal fluids’ coupled by their mutual gravity and derive asymptotic similarity solutions analytically. One of the fluids roughly approximates the massive dark matter halo, while the other describes the hot gas, the relatively small mass contribution from the galaxies being subsumed in the gas. By properly choosing the self-similar variables, it is possible to consistently transform the set of time-dependent two-fluid equations of spherical symmetry with self-gravity into a set of coupled nonlinear ordinary differential equations (ODEs). We focus on the analytical analysis and discuss applications of the solutions to galaxy clusters.
Data Point Averaging for Computational Fluid Dynamics Data
Norman, Jr., David (Inventor)
2016-01-01
A system and method for generating fluid flow parameter data for use in aerodynamic heating analysis. Computational fluid dynamics data is generated for a number of points in an area on a surface to be analyzed. Sub-areas corresponding to areas of the surface for which an aerodynamic heating analysis is to be performed are identified. A computer system automatically determines a sub-set of the number of points corresponding to each of the number of sub-areas and determines a value for each of the number of sub-areas using the data for the sub-set of points corresponding to each of the number of sub-areas. The value is determined as an average of the data for the sub-set of points corresponding to each of the number of sub-areas. The resulting parameter values then may be used to perform an aerodynamic heating analysis.
Spreading dynamics and dynamic contact angle of non-Newtonian fluids.
Wang, X D; Lee, D J; Peng, X F; Lai, J Y
2007-07-17
The spreading dynamics of power-law fluids, both shear-thinning and shear-thickening fluids, that completely or partially wet solid substrate was investigated theoretically and experimentally. An evolution equation for liquid-film thickness was derived using a lubrication approximation, from which the dynamic contact angle versus the contact line moving velocity relationship was evaluated. In the capillary spreading regime, film thickness h is proportional to xi3/(n+2) (xi is the distance from the contact line), whereas in the gravitational regime, h is proportional to xi1/(n+2), relating to the rheological power exponent n. The derived model fit the experimental data well for a shear-thinning fluid (0.2% w/w xanthan solution) or a shear-thickening fluid (7.5% w/w 10 nm silica in polypropylene glycol) on a completely wetted substrate. The derived model was extended using Hoffmann's proposal for partially wetting fluids. Good agreement was also attained between model predictions and the shear-thinning fluid (1% w/w cmc solution) and shear-thickening fluid (10% w/w 15 nm silica) on partially wetted surfaces.
Fluid dynamics of ventricular filling in the embryonic heart.
Miller, Laura A
2011-09-01
The vertebrate embryonic heart first forms as a valveless tube that pumps blood using waves of contraction. As the heart develops, the atrium and ventricle bulge out from the heart tube, and valves begin to form through the expansion of the endocardial cushions. As a result of changes in geometry, conduction velocities, and material properties of the heart wall, the fluid dynamics and resulting spatial patterns of shear stress and transmural pressure change dramatically. Recent work suggests that these transitions are significant because fluid forces acting on the cardiac walls, as well as the activity of myocardial cells that drive the flow, are necessary for correct chamber and valve morphogenesis. In this article, computational fluid dynamics was used to explore how spatial distributions of the normal forces acting on the heart wall change as the endocardial cushions grow and as the cardiac wall increases in stiffness. The immersed boundary method was used to simulate the fluid-moving boundary problem of the cardiac wall driving the motion of the blood in a simplified model of a two-dimensional heart. The normal forces acting on the heart walls increased during the period of one atrial contraction because inertial forces are negligible and the ventricular walls must be stretched during filling. Furthermore, the force required to fill the ventricle increased as the stiffness of the ventricular wall was increased. Increased endocardial cushion height also drastically increased the force necessary to contract the ventricle. Finally, flow in the moving boundary model was compared to flow through immobile rigid chambers, and the forces acting normal to the walls were substantially different.
The stochastic dynamics of tethered microcantilevers in a viscous fluid
Energy Technology Data Exchange (ETDEWEB)
Robbins, Brian A.; Paul, Mark R. [Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Radiom, Milad; Ducker, William A. [Department of Chemical Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Walz, John Y. [Department of Chemical Engineering, University of Kentucky, Lexington, Kentucky 40506 (United States)
2014-10-28
We explore and quantify the coupled dynamics of a pair of micron scale cantilevers immersed in a viscous fluid that are also directly tethered to one another at their tips by a spring force. The spring force, for example, could represent the molecular stiffness or elasticity of a biomolecule or material tethered between the cantilevers. We use deterministic numerical simulations with the fluctuation-dissipation theorem to compute the stochastic dynamics of the cantilever pair for the conditions of experiment when driven only by Brownian motion. We validate our approach by comparing directly with experimental measurements in the absence of the tether which shows excellent agreement. Using numerical simulations, we quantify the correlated dynamics of the cantilever pair over a range of tether stiffness. Our results quantify the sensitivity of the auto- and cross-correlations of equilibrium fluctuations in cantilever displacement to the stiffness of the tether. We show that the tether affects the magnitude of the correlations which can be used in a measurement to probe the properties of an attached tethering substance. For the configurations of current interest using micron scale cantilevers in water, we show that the magnitude of the fluid coupling between the cantilevers is sufficiently small such that the influence of the tether can be significant. Our results show that the cross-correlation is more sensitive to tether stiffness than the auto-correlation indicating that a two-cantilever measurement has improved sensitivity when compared with a measurement using a single cantilever.
Fluid Dynamics Appearing during Simulated Microgravity Using Random Positioning Machines
Stern, Philip; Casartelli, Ernesto; Egli, Marcel
2017-01-01
Random Positioning Machines (RPMs) are widely used as tools to simulate microgravity on ground. They consist of two gimbal mounted frames, which constantly rotate biological samples around two perpendicular axes and thus distribute the Earth’s gravity vector in all directions over time. In recent years, the RPM is increasingly becoming appreciated as a laboratory instrument also in non-space-related research. For instance, it can be applied for the formation of scaffold-free spheroid cell clusters. The kinematic rotation of the RPM, however, does not only distribute the gravity vector in such a way that it averages to zero, but it also introduces local forces to the cell culture. These forces can be described by rigid body analysis. Although RPMs are commonly used in laboratories, the fluid motion in the cell culture flasks on the RPM and the possible effects of such on cells have not been examined until today; thus, such aspects have been widely neglected. In this study, we used a numerical approach to describe the fluid dynamic characteristic occurring inside a cell culture flask turning on an operating RPM. The simulations showed that the fluid motion within the cell culture flask never reached a steady state or neared a steady state condition. The fluid velocity depends on the rotational velocity of the RPM and is in the order of a few centimeters per second. The highest shear stresses are found along the flask walls; depending of the rotational velocity, they can reach up to a few 100 mPa. The shear stresses in the “bulk volume,” however, are always smaller, and their magnitude is in the order of 10 mPa. In conclusion, RPMs are highly appreciated as reliable tools in microgravity research. They have even started to become useful instruments in new research fields of mechanobiology. Depending on the experiment, the fluid dynamic on the RPM cannot be neglected and needs to be taken into consideration. The results presented in this study elucidate the fluid
Fluid Dynamics Appearing during Simulated Microgravity Using Random Positioning Machines.
Wuest, Simon L; Stern, Philip; Casartelli, Ernesto; Egli, Marcel
2017-01-01
Random Positioning Machines (RPMs) are widely used as tools to simulate microgravity on ground. They consist of two gimbal mounted frames, which constantly rotate biological samples around two perpendicular axes and thus distribute the Earth's gravity vector in all directions over time. In recent years, the RPM is increasingly becoming appreciated as a laboratory instrument also in non-space-related research. For instance, it can be applied for the formation of scaffold-free spheroid cell clusters. The kinematic rotation of the RPM, however, does not only distribute the gravity vector in such a way that it averages to zero, but it also introduces local forces to the cell culture. These forces can be described by rigid body analysis. Although RPMs are commonly used in laboratories, the fluid motion in the cell culture flasks on the RPM and the possible effects of such on cells have not been examined until today; thus, such aspects have been widely neglected. In this study, we used a numerical approach to describe the fluid dynamic characteristic occurring inside a cell culture flask turning on an operating RPM. The simulations showed that the fluid motion within the cell culture flask never reached a steady state or neared a steady state condition. The fluid velocity depends on the rotational velocity of the RPM and is in the order of a few centimeters per second. The highest shear stresses are found along the flask walls; depending of the rotational velocity, they can reach up to a few 100 mPa. The shear stresses in the "bulk volume," however, are always smaller, and their magnitude is in the order of 10 mPa. In conclusion, RPMs are highly appreciated as reliable tools in microgravity research. They have even started to become useful instruments in new research fields of mechanobiology. Depending on the experiment, the fluid dynamic on the RPM cannot be neglected and needs to be taken into consideration. The results presented in this study elucidate the fluid
Effect of dynamic contact angle in a volume of fluid (VOF) model for a microfluidic capillary flow.
Ashish Saha, Auro; Mitra, Sushanta K
2009-11-15
We perform three-dimensional numerical and experimental study of the dynamic contact angle using volume of fluid (VOF) method applied to microfluidic channels with integrated pillars. Initially, we evaluated different dynamic contact angle models (hydrodynamic, molecular kinetic and empirical) for capillary filling of a two-dimensional microchannel using analytical formulation. Further, the models which require a minimum prescription of adjustable parameters are only used for the study of capillary filling of microchannels with integrated pillars using different working fluids such as DI water, ethanol and isopropyl alcohol. Different microchannel geometry with varying diameter/height/spacing were studied for circular pillars. Effect of square pillars and changing the overall number of pillars on the capillary phenomena were also simulated. Our study demonstrated that the dynamic contact angle models modifies the transient response of the meniscus displacement and also the observed trends are model specific for the various microchannel geometries and working fluids. However, the different models have minimal effect on the meniscus profile. Different inlet boundary conditions were applied to observe the effect of grid resolution selected for numerical study on the capillary filling time. A grid dependent dynamic contact angle model which incorporates effective slip in the model was also used to observe the grid convergence of the numerical results. The grid independence was shown to improve marginally by applying the grid dependent dynamic contact angle model. Further we did numerical experiments of capillary filling considering variable surface wettability on the top and bottom walls of the microchannel with alternate hydrophilic-hydrophobic patterns. The meniscus front pinning was noticed for a high wetting contrast between the patterns. Non uniform streamline patterns indicated mixing of the fluid when using patterned walls. Such a microfluidic device with
Coslovich, Daniele; Kahl, Gerhard; Krakoviack, Vincent
2011-06-01
Over the past two decades, the dynamics of fluids under nanoscale confinement has attracted much attention. Motivation for this rapidly increasing interest is based on both practical and fundamental reasons. On the practical and rather applied side, problems in a wide range of scientific topics, such as polymer and colloidal sciences, rheology, geology, or biophysics, benefit from a profound understanding of the dynamical behaviour of confined fluids. Further, effects similar to those observed in confinement are expected in fluids whose constituents have strong size or mass asymmetry, and in biological systems where crowding and obstruction phenomena in the cytosol are responsible for clear separations of time scales for macromolecular transport in the cell. In fundamental research, on the other hand, the interest focuses on the complex interplay between confinement and structural relaxation, which is responsible for the emergence of new phenomena in the dynamics of the system: in confinement, geometric constraints associated with the pore shape are imposed to the adsorbed fluids and an additional characteristic length scale, i.e. the pore size, comes into play. For many years, the topic has been mostly experimentally driven. Indeed, a broad spectrum of systems has been investigated by sophisticated experimental techniques, while theoretical and simulation studies were rather scarce due to conceptual and computational issues. In the past few years, however, theory and simulations could largely catch up with experiments. On one side, new theories have been put forward that duly take into account the porosity, the connectivity, and the randomness of the confinement. On the other side, the ever increasing available computational power now allows investigations that were far out of reach a few years ago. Nowadays, instead of isolated state points, systematic investigations on the dynamics of confined fluids, covering a wide range of system parameters, can be realized
Dynamic Multiscaling in Two-dimensional Fluid Turbulence
Ray, Samriddhi Sankar; Perlekar, Prasad; Pandit, Rahul
2011-01-01
We obtain, by extensive direct numerical simulations, time-dependent and equal-time structure functions for the vorticity, in both quasi-Lagrangian and Eulerian frames, for the direct-cascade regime in two-dimensional fluid turbulence with air-drag-induced friction. We show that different ways of extracting time scales from these time-dependent structure functions lead to different dynamic-multiscaling exponents, which are related to equal-time multiscaling exponents by different classes of bridge relations; for a representative value of the friction we verify that, given our error bars, these bridge relations hold.
Coupling lattice Boltzmann and molecular dynamics models for dense fluids
Dupuis, A.; Kotsalis, E. M.; Koumoutsakos, P.
2007-04-01
We propose a hybrid model, coupling lattice Boltzmann (LB) and molecular dynamics (MD) models, for the simulation of dense fluids. Time and length scales are decoupled by using an iterative Schwarz domain decomposition algorithm. The MD and LB formulations communicate via the exchange of velocities and velocity gradients at the interface. We validate the present LB-MD model in simulations of two- and three-dimensional flows of liquid argon past and through a carbon nanotube. Comparisons with existing hybrid algorithms and with reference MD solutions demonstrate the validity of the present approach.
Computational fluid dynamics in fire engineering theory, modelling and practice
Yuen, Kwok Kit
2009-01-01
Fire and combustion presents a significant engineering challenge to mechanical, civil and dedicated fire engineers, as well as specialists in the process and chemical, safety, buildings and structural fields. We are reminded of the tragic outcomes of 'untenable' fire disasters such as at King's Cross underground station or Switzerland's St Gotthard tunnel. In these and many other cases, computational fluid dynamics (CFD) is at the forefront of active research into unravelling the probable causes of fires and helping to design structures and systems to ensure that they are less likely in the f
Continuing Validation of Computational Fluid Dynamics for Supersonic Retropropulsion
Schauerhamer, Daniel Guy; Trumble, Kerry A.; Kleb, Bil; Carlson, Jan-Renee; Edquist, Karl T.
2011-01-01
A large step in the validation of Computational Fluid Dynamics (CFD) for Supersonic Retropropulsion (SRP) is shown through the comparison of three Navier-Stokes solvers (DPLR, FUN3D, and OVERFLOW) and wind tunnel test results. The test was designed specifically for CFD validation and was conducted in the Langley supersonic 4 x4 Unitary Plan Wind Tunnel and includes variations in the number of nozzles, Mach and Reynolds numbers, thrust coefficient, and angles of orientation. Code-to-code and code-to-test comparisons are encouraging and possible error sources are discussed.
Experimental investigations of fluid dynamic and thermal performance of nanofluids
Kulkarni, Devdatta Prakash
The goal of this research was to investigate the fluid dynamic and thermal performance of various nanofluids. Nanofluids are dispersions of metallic nanometer size particles (choice of base fluid is an ethylene or propylene glycol and water mixture in cold regions. Initially the rheological characterization of copper oxide (CuO) nanofluids in water and in propylene glycol was performed. Results revealed that higher concentrations of CuO nanoparticles (5 to 15%) in water exhibited time-independent pseudoplastic and shear-thinning behavior. Lower concentrations (1 to 6%) of CuO nanofluids in propylene glycol revealed that these nanofluids behaved as Newtonian fluids. Both nanofluids showed that viscosity decreased exponentially with increase in temperature. Subsequent correlations for viscosities as a function of volume concentration and temperature were developed. Effects of different thermophysical properties on the Prandtl number of CuO, silicon dioxide (SiO2) and aluminum oxide (A12O 3) nanofluids were investigated. Results showed that the Prandtl number increased with increasing volume concentrations, which in turn increased the heat transfer coefficients of the nanofluids. Various nanofluids were compared for their heat transfer rates based on the Mouromtseff number, which is a Figure of Merit for heat transfer fluids. From this analysis, the optimal concentrations of nanoparticles in base fluids were found for CuO-water nanofluids. Experiments were performed to investigate the convective heat transfer enhancement and pressure loss of CuO, SiO2 and A12O 3 nanofluids in the turbulent regime. The increases in heat transfer coefficient by nanofluids for various volume concentrations compared to the base fluid were determined. Pressure loss was observed to increase with nanoparticle volume concentration. It was observed that an increase in particle diameter increased the heat transfer coefficient. Calculations showed that application of nanofluids in heat
Front-end electronics for CsI based charged particle array for the study of reaction dynamics
Energy Technology Data Exchange (ETDEWEB)
Jhingan, Akhil, E-mail: akhil@iuac.res.in [Inter University Accelerator Centre, P.O. Box 10502, New Delhi 110067 (India); Sugathan, P. [Inter University Accelerator Centre, P.O. Box 10502, New Delhi 110067 (India); Kaur, Gurpreet; Kapoor, K. [Department of Physics, Panjab University, Chandigarh 160014 (India); Saneesh, N.; Banerjee, T. [Inter University Accelerator Centre, P.O. Box 10502, New Delhi 110067 (India); Singh, Hardev [Department of Physics, Kurukshetra University, Kurukshetra 136119 (India); Kumar, A.; Behera, B.R. [Department of Physics, Panjab University, Chandigarh 160014 (India); Nayak, B.K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)
2015-06-21
The characteristics and performance of a new detector system based on CsI(TI) scintillators, and its front-end electronics are presented. The detector system has been developed for the detection of light charged particles to investigate fusion–fission dynamics, and will also serve as ancillary detector for an array of neutron detectors. CsI scintillators are read by photo-diodes. The main feature of the array is its compact and simple high density front-end electronics which includes custom developed low noise charge sensitive preamplifiers (with very low power consumption for operation inside vacuum), NIM differential drivers, and commercially available Mesytec amplifiers with two different time constants for particle identification using a ballistic deficit technique.
Computational Fluid Dynamics Simulation of Fluidized Bed Polymerization Reactors
Energy Technology Data Exchange (ETDEWEB)
Fan, Rong [Iowa State Univ., Ames, IA (United States)
2006-01-01
Fluidized beds (FB) reactors are widely used in the polymerization industry due to their superior heat- and mass-transfer characteristics. Nevertheless, problems associated with local overheating of polymer particles and excessive agglomeration leading to FB reactors defluidization still persist and limit the range of operating temperatures that can be safely achieved in plant-scale reactors. Many people have been worked on the modeling of FB polymerization reactors, and quite a few models are available in the open literature, such as the well-mixed model developed by McAuley, Talbot, and Harris (1994), the constant bubble size model (Choi and Ray, 1985) and the heterogeneous three phase model (Fernandes and Lona, 2002). Most these research works focus on the kinetic aspects, but from industrial viewpoint, the behavior of FB reactors should be modeled by considering the particle and fluid dynamics in the reactor. Computational fluid dynamics (CFD) is a powerful tool for understanding the effect of fluid dynamics on chemical reactor performance. For single-phase flows, CFD models for turbulent reacting flows are now well understood and routinely applied to investigate complex flows with detailed chemistry. For multiphase flows, the state-of-the-art in CFD models is changing rapidly and it is now possible to predict reasonably well the flow characteristics of gas-solid FB reactors with mono-dispersed, non-cohesive solids. This thesis is organized into seven chapters. In Chapter 2, an overview of fluidized bed polymerization reactors is given, and a simplified two-site kinetic mechanism are discussed. Some basic theories used in our work are given in detail in Chapter 3. First, the governing equations and other constitutive equations for the multi-fluid model are summarized, and the kinetic theory for describing the solid stress tensor is discussed. The detailed derivation of DQMOM for the population balance equation is given as the second section. In this section
MagIC: Fluid dynamics in a spherical shell simulator
Wicht, J.; Gastine, T.; Barik, A.; Putigny, B.; Yadav, R.; Duarte, L.; Dintrans, B.
2017-09-01
MagIC simulates fluid dynamics in a spherical shell. It solves for the Navier-Stokes equation including Coriolis force, optionally coupled with an induction equation for Magneto-Hydro Dynamics (MHD), a temperature (or entropy) equation and an equation for chemical composition under both the anelastic and the Boussinesq approximations. MagIC uses either Chebyshev polynomials or finite differences in the radial direction and spherical harmonic decomposition in the azimuthal and latitudinal directions. The time-stepping scheme relies on a semi-implicit Crank-Nicolson for the linear terms of the MHD equations and a Adams-Bashforth scheme for the non-linear terms and the Coriolis force.
Relativistic Fluid Dynamics: Physics for Many Different Scales
Directory of Open Access Journals (Sweden)
Comer Gregory L.
2007-01-01
Full Text Available The relativistic fluid is a highly successful model used to describe the dynamics of many-particle, relativistic systems. It takes as input basic physics from microscopic scales and yields as output predictions of bulk, macroscopic motion. By inverting the process, an understanding of bulk features can lead to insight into physics on the microscopic scale. Relativistic fluids have been used to model systems as “small” as heavy ions in collisions, and as large as the Universe itself, with “intermediate” sized objects like neutron stars being considered along the way. The purpose of this review is to discuss the mathematical and theoretical physics underpinnings of the relativistic (multiple fluid model. We focus on the variational principle approach championed by Brandon Carter and his collaborators, in which a crucial element is to distinguish the momenta that are conjugate to the particle number density currents. This approach differs from the “standard” text-book derivation of the equations of motion from the divergence of the stress-energy tensor in that one explicitly obtains the relativistic Euler equation as an “integrability” condition on the relativistic vorticity. We discuss the conservation laws and the equations of motion in detail, and provide a number of (in our opinion interesting and relevant applications of the general theory.
Dissolution Dynamic Nuclear Polarization capability study with fluid path
Malinowski, Ronja M.; Lipsø, Kasper W.; Lerche, Mathilde H.; Ardenkjær-Larsen, Jan H.
2016-11-01
Signal enhancement by hyperpolarization is a way of overcoming the low sensitivity in magnetic resonance; MRI in particular. One of the most well-known methods, dissolution Dynamic Nuclear Polarization, has been used clinically in cancer patients. One way of ensuring a low bioburden of the hyperpolarized product is by use of a closed fluid path that constitutes a barrier to contamination. The fluid path can be filled with the pharmaceuticals, i.e. imaging agent and solvents, in a clean room, and then stored or immediately used at the polarizer. In this study, we present a method of filling the fluid path that allows it to be reused. The filling method has been investigated in terms of reproducibility at two extrema, high dose for patient use and low dose for rodent studies, using [1-13C]pyruvate as example. We demonstrate that the filling method allows high reproducibility of six quality control parameters with standard deviations 3-10 times smaller than the acceptance criteria intervals in clinical studies.
Dissolution Dynamic Nuclear Polarization capability study with fluid path.
Malinowski, Ronja M; Lipsø, Kasper W; Lerche, Mathilde H; Ardenkjær-Larsen, Jan H
2016-11-01
Signal enhancement by hyperpolarization is a way of overcoming the low sensitivity in magnetic resonance; MRI in particular. One of the most well-known methods, dissolution Dynamic Nuclear Polarization, has been used clinically in cancer patients. One way of ensuring a low bioburden of the hyperpolarized product is by use of a closed fluid path that constitutes a barrier to contamination. The fluid path can be filled with the pharmaceuticals, i.e. imaging agent and solvents, in a clean room, and then stored or immediately used at the polarizer. In this study, we present a method of filling the fluid path that allows it to be reused. The filling method has been investigated in terms of reproducibility at two extrema, high dose for patient use and low dose for rodent studies, using [1-13C]pyruvate as example. We demonstrate that the filling method allows high reproducibility of six quality control parameters with standard deviations 3-10 times smaller than the acceptance criteria intervals in clinical studies. Copyright © 2016 Elsevier Inc. All rights reserved.
Computational Fluid Dynamics Analysis of Canadian Supercritical Water Reactor (SCWR)
Movassat, Mohammad; Bailey, Joanne; Yetisir, Metin
2015-11-01
A Computational Fluid Dynamics (CFD) simulation was performed on the proposed design for the Canadian SuperCritical Water Reactor (SCWR). The proposed Canadian SCWR is a 1200 MW(e) supercritical light-water cooled nuclear reactor with pressurized fuel channels. The reactor concept uses an inlet plenum that all fuel channels are attached to and an outlet header nested inside the inlet plenum. The coolant enters the inlet plenum at 350 C and exits the outlet header at 625 C. The operating pressure is approximately 26 MPa. The high pressure and high temperature outlet conditions result in a higher electric conversion efficiency as compared to existing light water reactors. In this work, CFD simulations were performed to model fluid flow and heat transfer in the inlet plenum, outlet header, and various parts of the fuel assembly. The ANSYS Fluent solver was used for simulations. Results showed that mass flow rate distribution in fuel channels varies radially and the inner channels achieve higher outlet temperatures. At the outlet header, zones with rotational flow were formed as the fluid from 336 fuel channels merged. Results also suggested that insulation of the outlet header should be considered to reduce the thermal stresses caused by the large temperature gradients.
Ringin' the water bell: dynamic modes of curved fluid sheets
Kolinski, John; Aharoni, Hillel; Fineberg, Jay; Sharon, Eran
2015-11-01
A water bell is formed by fluid flowing in a thin, coherent sheet in the shape of a bell. Experimentally, a water bell is created via the impact of a cylindrical jet on a flat surface. Its shape is set by the splash angle (the separation angle) of the resulting cylindrically symmetric water sheet. The separation angle is altered by adjusting the height of a lip surrounding the impact point, as in a water sprinkler. We drive the lip's height sinusoidally, altering the separation angle, and ringin' the water bell. This forcing generates disturbances on the steady-state water bell that propagate forward and backward in the fluid's reference frame at well-defined velocities, and interact, resulting in the emergence of an interference pattern unique to each steady-state geometry. We analytically model these dynamics by linearizing the amplitude of the bell's response about the underlying curved geometry. This simple model predicts the nodal structure over a wide range of steady-state water bell configurations and driving frequencies. Due to the curved water bell geometry, the nodal structure is quite complex; nevertheless, the predicted nodal structure agrees extremely well with the experimental data. When we drive the bell beyond perturbative separation angles, the nodal locations surprisingly persist, despite the strikingly altered underlying water bell shape. At extreme driving amplitudes the water sheet assumes a rich variety of tortuous, non-convex shapes; nevertheless, the fluid sheet remains intact.
Fluid-dynamic design optimization of hydraulic proportional directional valves
Amirante, Riccardo; Catalano, Luciano Andrea; Poloni, Carlo; Tamburrano, Paolo
2014-10-01
This article proposes an effective methodology for the fluid-dynamic design optimization of the sliding spool of a hydraulic proportional directional valve: the goal is the minimization of the flow force at a prescribed flow rate, so as to reduce the required opening force while keeping the operation features unchanged. A full three-dimensional model of the flow field within the valve is employed to accurately predict the flow force acting on the spool. A theoretical analysis, based on both the axial momentum equation and flow simulations, is conducted to define the design parameters, which need to be properly selected in order to reduce the flow force without significantly affecting the flow rate. A genetic algorithm, coupled with a computational fluid dynamics flow solver, is employed to minimize the flow force acting on the valve spool at the maximum opening. A comparison with a typical single-objective optimization algorithm is performed to evaluate performance and effectiveness of the employed genetic algorithm. The optimized spool develops a maximum flow force which is smaller than that produced by the commercially available valve, mainly due to some major modifications occurring in the discharge section. Reducing the flow force and thus the electromagnetic force exerted by the solenoid actuators allows the operational range of direct (single-stage) driven valves to be enlarged.
Computational Fluid Dynamics Analysis of High Injection Pressure Blended Biodiesel
Khalid, Amir; Jaat, Norrizam; Faisal Hushim, Mohd; Manshoor, Bukhari; Zaman, Izzuddin; Sapit, Azwan; Razali, Azahari
2017-08-01
Biodiesel have great potential for substitution with petrol fuel for the purpose of achieving clean energy production and emission reduction. Among the methods that can control the combustion properties, controlling of the fuel injection conditions is one of the successful methods. The purpose of this study is to investigate the effect of high injection pressure of biodiesel blends on spray characteristics using Computational Fluid Dynamics (CFD). Injection pressure was observed at 220 MPa, 250 MPa and 280 MPa. The ambient temperature was kept held at 1050 K and ambient pressure 8 MPa in order to simulate the effect of boost pressure or turbo charger during combustion process. Computational Fluid Dynamics were used to investigate the spray characteristics of biodiesel blends such as spray penetration length, spray angle and mixture formation of fuel-air mixing. The results shows that increases of injection pressure, wider spray angle is produced by biodiesel blends and diesel fuel. The injection pressure strongly affects the mixture formation, characteristics of fuel spray, longer spray penetration length thus promotes the fuel and air mixing.
Computational Fluid Dynamics (CFD) Technology Programme 1995- 1999
Energy Technology Data Exchange (ETDEWEB)
Haekkinen, R.J.; Hirsch, C.; Krause, E.; Kytoemaa, H.K. [eds.
1997-12-31
The report is a mid-term evaluation of the Computational Fluid Dynamics (CFD) Technology Programme started by Technology Development Centre Finland (TEKES) in 1995 as a five-year initiative to be concluded in 1999. The main goal of the programme is to increase the know-how and application of CFD in Finnish industry, to coordinate and thus provide a better basis for co-operation between national CFD activities and encouraging research laboratories and industry to establish co-operation with the international CFD community. The projects of the programme focus on the following areas: (1) studies of modeling the physics and dynamics of the behaviour of fluid material, (2) expressing the physical models in a numerical mode and developing a computer codes, (3) evaluating and testing current physical models and developing new ones, (4) developing new numerical algorithms, solvers, and pre- and post-processing software, and (5) applying the new computational tools to problems relevant to their ultimate industrial use. The report consists of two sections. The first considers issues concerning the whole programme and the second reviews each project
Dynamic hysteresis in the rheology of complex fluids.
Puisto, Antti; Mohtaschemi, Mikael; Alava, Mikko J; Illa, Xavier
2015-04-01
Recently, rheological hysteresis has been studied systematically in a wide range of complex fluids combining global rheology and time-resolved velocimetry. In this paper we present an analysis of the roles of the three most fundamental mechanisms in simple-yield-stress fluids: structure dynamics, viscoelastic response, and spatial flow heterogeneities, i.e., time-dependent shear bands. Dynamical hysteresis simulations are done analogously to rheological ramp-up and -down experiments on a coupled model which incorporates viscoelasticity and time-dependent structure evolution. Based on experimental data, a coupling between hysteresis measured from the local velocity profiles and that measured from the global flow curve has been suggested. According to the present model, even if transient shear banding appears during the shear ramps, in typical narrow-gap devices, only a small part of the hysteretic response can be attributed to heterogeneous flow. This results in decoupling of the hysteresis measured from the local velocity profiles and the global flow curve, demonstrating that for an arbitrary time-dependent rheological response this proposed coupling can be very weak.
Meniscal Tear Film Fluid Dynamics Near Marx’s Line
Zubkov, V. S.
2013-07-03
Extensive studies have explored the dynamics of the ocular surface fluid, though theoretical investigations are typically limited to the use of the lubrication approximation, which is not guaranteed to be uniformly valid a-priori throughout the tear meniscus. However, resolving tear film behaviour within the meniscus and especially its apices is required to characterise the flow dynamics where the tear film is especially thin, and thus most susceptible to evaporatively induced hyperosmolarity and subsequent epithelial damage. Hence, we have explored the accuracy of the standard lubrication approximation for the tear film by explicit comparisons with the 2D Navier-Stokes model, considering both stationary and moving eyelids. Our results demonstrate that the lubrication model is qualitatively accurate except in the vicinity of the eyelids. In particular, and in contrast to lubrication theory, the solution of the full Navier-Stokes equations predict a distinct absence of fluid flow, and thus convective mixing in the region adjacent to the tear film contact line. These observations not only support emergent hypotheses concerning the formation of Marx\\'s line, a region of epithelial cell staining adjacent to the contact line on the eyelid, but also enhance our understanding of the pathophysiological consequences of the flow profile near the tear film contact line. © 2013 Society for Mathematical Biology.
Fluid dynamics in airway bifurcations: I. Primary flows.
Martonen, T B; Guan, X; Schreck, R M
2001-04-01
The subject of fluid dynamics within human airways is of great importance for the risk assessment of air pollutants (inhalation toxicology) and the targeted delivery of inhaled pharmacologic drugs (aerosol therapy). As cited herein, experimental investigations of flow patterns have been performed on airway models and casts by a number of investigators. We have simulated flow patterns in human lung bifurcations and compared the results with the experimental data of Schreck (1972). The theoretical analyses were performed using a third-party software package, FIDAP, on the Cray T90 supercomputer. This effort is part of a systematic investigation where the effects of inlet conditions, Reynolds numbers, and dimensions and orientations of airways were addressed. This article focuses on primary flows using convective motion and isovelocity contour formats to describe fluid dynamics; subsequent articles in this issue consider secondary currents (Part II) and localized conditions (Part III). The agreement between calculated and measured results, for laminar flows with either parabolic or blunt inlet conditions to the bifurcations, was very good. To our knowledge, this work is the first to present such detailed comparisons of theoretical and experimental flow patterns in airway bifurcations. The agreement suggests that the methodologies can be employed to study factors affecting airflow patterns and particle behavior in human lungs.
Respiratory mechanics and fluid dynamics after lung resection surgery.
Miserocchi, Giuseppe; Beretta, Egidio; Rivolta, Ilaria
2010-08-01
Thoracic surgery that requires resection of a portion of lung or of a whole lung profoundly alters the mechanical and fluid dynamic setting of the lung-chest wall coupling, as well as the water balance in the pleural space and in the remaining lung. The most frequent postoperative complications are of a respiratory nature, and their incidence increases the more the preoperative respiratory condition seems compromised. There is an obvious need to identify risk factors concerning mainly the respiratory function, without neglecting the importance of other comorbidities, such as coronary disease. At present, however, a satisfactory predictor of postoperative cardiopulmonary complications is lacking; postoperative morbidity and mortality have remained unchanged in the last 10 years. The aim of this review is to provide a pathophysiologic interpretation of the main respiratory complications of a respiratory nature by relying on new concepts relating to lung fluid dynamics and mechanics. New parameters are proposed to improve evaluation of respiratory function from pre- to the early postoperative period when most of the complications occur.
Computational fluid dynamic modeling of fluidized-bed polymerization reactors
Energy Technology Data Exchange (ETDEWEB)
Rokkam, Ram [Iowa State Univ., Ames, IA (United States)
2012-01-01
Polyethylene is one of the most widely used plastics, and over 60 million tons are produced worldwide every year. Polyethylene is obtained by the catalytic polymerization of ethylene in gas and liquid phase reactors. The gas phase processes are more advantageous, and use fluidized-bed reactors for production of polyethylene. Since they operate so close to the melting point of the polymer, agglomeration is an operational concern in all slurry and gas polymerization processes. Electrostatics and hot spot formation are the main factors that contribute to agglomeration in gas-phase processes. Electrostatic charges in gas phase polymerization fluidized bed reactors are known to influence the bed hydrodynamics, particle elutriation, bubble size, bubble shape etc. Accumulation of electrostatic charges in the fluidized-bed can lead to operational issues. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the dynamics of a fluidized-bed. The multi-fluid CFD model for gas-particle flow is based on the kinetic theory of granular flows closures. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer, polymer fines) phase. The combined CFD model is first verified using simple test cases, validated with experiments and applied to a pilot-scale polymerization fluidized-bed reactor. The CFD model reproduced qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments. For the scale up of fluidized bed reactor, filtered models are developed and implemented on pilot scale reactor.
Dynamics of fluid and light intensity in mechanically stirred photobioreactor.
Zhang, T
2013-10-10
Turbulent flows in a single-stage and a two-stage impeller-stirred photobioreactor with a simple geometric configuration were analyzed using computational fluid dynamics. The trajectories of the microorganisms entrained in the flow field were traced by the particle tracking method. By projecting these trajectories onto a radial-axial (r-z) plane with a given azimuth angle, we were able to observe four different dynamics zones: circulation, pure rotation, trap, and slow-motion. Within the pure rotation zone, turbulence can be observed near the edges of the impeller. The light intensity and the light/dark cycles subjected by the microorganisms differ significantly in these zones. These differences can be further changed by providing different incident light illuminations on the reactor surface. The dynamics zones can be altered by modifying the geometric configuration of the reactor and the impeller stirring mechanism. In combination with the utilization of different incident light illuminations, the light intensity dynamics and the light/dark cycles subjected by the microorganisms can be controlled such that an optimal photobioreactor design with a high efficiency of light utilization and a high formation rate of the biochemical products can be realized.
Computational fluid dynamics framework for aerodynamic model assessment
Vallespin, D.; Badcock, K. J.; Da Ronch, A.; White, M. D.; Perfect, P.; Ghoreyshi, M.
2012-07-01
This paper reviews the work carried out at the University of Liverpool to assess the use of CFD methods for aircraft flight dynamics applications. Three test cases are discussed in the paper, namely, the Standard Dynamic Model, the Ranger 2000 jet trainer and the Stability and Control Unmanned Combat Air Vehicle. For each of these, a tabular aerodynamic model based on CFD predictions is generated along with validation against wind tunnel experiments and flight test measurements. The main purpose of the paper is to assess the validity of the tables of aerodynamic data for the force and moment prediction of realistic aircraft manoeuvres. This is done by generating a manoeuvre based on the tables of aerodynamic data, and then replaying the motion through a time-accurate computational fluid dynamics calculation. The resulting forces and moments from these simulations were compared with predictions from the tables. As the latter are based on a set of steady-state predictions, the comparisons showed perfect agreement for slow manoeuvres. As manoeuvres became more aggressive some disagreement was seen, particularly during periods of large rates of change in attitudes. Finally, the Ranger 2000 model was used on a flight simulator.
Computational Fluid Dynamics Demonstration of Rigid Bodies in Motion
Camarena, Ernesto; Vu, Bruce T.
2011-01-01
The Design Analysis Branch (NE-Ml) at the Kennedy Space Center has not had the ability to accurately couple Rigid Body Dynamics (RBD) and Computational Fluid Dynamics (CFD). OVERFLOW-D is a flow solver that has been developed by NASA to have the capability to analyze and simulate dynamic motions with up to six Degrees of Freedom (6-DOF). Two simulations were prepared over the course of the internship to demonstrate 6DOF motion of rigid bodies under aerodynamic loading. The geometries in the simulations were based on a conceptual Space Launch System (SLS). The first simulation that was prepared and computed was the motion of a Solid Rocket Booster (SRB) as it separates from its core stage. To reduce computational time during the development of the simulation, only half of the physical domain with respect to the symmetry plane was simulated. Then a full solution was prepared and computed. The second simulation was a model of the SLS as it departs from a launch pad under a 20 knot crosswind. This simulation was reduced to Two Dimensions (2D) to reduce both preparation and computation time. By allowing 2-DOF for translations and 1-DOF for rotation, the simulation predicted unrealistic rotation. The simulation was then constrained to only allow translations.
An Automated High Aspect Ratio Mesher for Computational Fluid Dynamics Project
National Aeronautics and Space Administration — Computational fluid dynamics (CFD) simulations are routinely used while designing, analyzing, and optimizing air- and spacecraft. An important component of CFD...
Frozen reaction fronts in steady flows: a burning-invariant-manifold perspective
Mahoney, John R; Boyer, Carleen; Solomon, Tom; Mitchell, Kevin A
2015-01-01
The dynamics of fronts, such as chemical reaction fronts, propagating in two-dimensional fluid flows can be remarkably rich and varied. For time-invariant flows, the front dynamics may simplify, settling in to a steady state in which the reacted domain is static, and the front appears "frozen". Our central result is that these frozen fronts in the two-dimensional fluid are composed of segments of burning invariant manifolds---invariant manifolds of front-element dynamics in $xy\\theta$-space, where $\\theta$ is the front orientation. Burning invariant manifolds (BIMs) have been identified previously as important local barriers to front propagation in fluid flows. The relevance of BIMs for frozen fronts rests in their ability, under appropriate conditions, to form global barriers, separating reacted domains from nonreacted domains for all time. The second main result of this paper is an understanding of bifurcations that lead from a nonfrozen state to a frozen state, as well as bifurcations that change the topol...
Wu, Binxin
2010-12-01
In this paper, 12 turbulence models for single-phase non-newtonian fluid flow in a pipe are evaluated by comparing the frictional pressure drops obtained from computational fluid dynamics (CFD) with those from three friction factor correlations. The turbulence models studied are (1) three high-Reynolds-number k-ε models, (2) six low-Reynolds-number k-ε models, (3) two k-ω models, and (4) the Reynolds stress model. The simulation results indicate that the Chang-Hsieh-Chen version of the low-Reynolds-number k-ε model performs better than the other models in predicting the frictional pressure drops while the standard k-ω model has an acceptable accuracy and a low computing cost. In the model applications, CFD simulation of mixing in a full-scale anaerobic digester with pumped circulation is performed to propose an improvement in the effective mixing standards recommended by the U.S. EPA based on the effect of rheology on the flow fields. Characterization of the velocity gradient is conducted to quantify the growth or breakage of an assumed floc size. Placement of two discharge nozzles in the digester is analyzed to show that spacing two nozzles 180° apart with each one discharging at an angle of 45° off the wall is the most efficient. Moreover, the similarity rules of geometry and mixing energy are checked for scaling up the digester.
Improvement of Basic Fluid Dynamics Models for the COMPASS Code
Zhang, Shuai; Morita, Koji; Shirakawa, Noriyuki; Yamamoto, Yuichi
The COMPASS code is a new next generation safety analysis code to provide local information for various key phenomena in core disruptive accidents of sodium-cooled fast reactors, which is based on the moving particle semi-implicit (MPS) method. In this study, improvement of basic fluid dynamics models for the COMPASS code was carried out and verified with fundamental verification calculations. A fully implicit pressure solution algorithm was introduced to improve the numerical stability of MPS simulations. With a newly developed free surface model, numerical difficulty caused by poor pressure solutions is overcome by involving free surface particles in the pressure Poisson equation. In addition, applicability of the MPS method to interactions between fluid and multi-solid bodies was investigated in comparison with dam-break experiments with solid balls. It was found that the PISO algorithm and free surface model makes simulation with the passively moving solid model stable numerically. The characteristic behavior of solid balls was successfully reproduced by the present numerical simulations.
Adaptive thermo-fluid moving boundary computations for interfacial dynamics
Institute of Scientific and Technical Information of China (English)
Chih-Kuang Kuan; Jaeheon Sim; Wei Shyy
2012-01-01
In this study,we present adaptive moving boundary computation technique with parallel implementation on a distributed memory multi-processor system for large scale thermo-fluid and interfacial flow computations.The solver utilizes Eulerian-Lagrangian method to track moving (Lagrangian) interfaces explicitly on the stationary (Eulerian)Cartesian grid where the flow fields are computed. We address the domain decomposition strategies of EulerianLagrangian method by illustrating its intricate complexity of the computation involved on two different spaces interactively and consequently,and then propose a trade-off approach aiming for parallel scalability.Spatial domain decomposition is adopted for both Eulerian and Lagrangian domain due to easy load balancing and data locality for minimum communication between processors.In addition,parallel cell-based unstructured adaptive mesh refinement (AMR)technique is implemented for the flexible local refinement and even-distributed computational workload among processors.Selected cases are presented to highlight the computational capabilities,including Faraday type interfacial waves with capillary and gravitational forcing,flows around varied geometric configurations and induced by boundary conditions and/or body forces,and thermo-fluid dynamics with phase change.With the aid of the present techniques,large scale challenging moving boundary problems can be effectively addressed.
Transcapillary fluid dynamics during ovarian stimulation for in vitro fertilization.
Tollan, A; Holst, N; Forsdahl, F; Fadnes, H O; Oian, P; Maltau, J M
1990-02-01
Transcapillary fluid dynamics were studied in 10 women during ovarian stimulation for in vitro fertilization. The examinations were done on the first day of stimulation (day 3 of the menstrual cycle, mean serum estradiol concentration 0.2 nmol/L), and the day before oocyte aspiration (day 10 to 12, mean serum estradiol concentration 6.8 nmol/L). Interstitial colloid osmotic pressure was measured on the thorax at heart level by the "wick" method, and interstitial hydrostatic pressure by the "wick-in-needle" method. Plasma colloid osmotic pressure decreased (mean, 2.0 mm Hg; p less than 0.002) and interstitial colloid osmotic pressure increased (mean, 1.0 mm Hg; p less than 0.02) during hormonal stimulation. This implies a reduced transcapillary colloid osmotic gradient (plasma colloid osmotic pressure--interstitial colloid osmotic pressure), probably because of increased capillary permeability to plasma proteins. Hemoglobin and hematocrit were significantly reduced, and body weight and foot volume significantly increased. These results demonstrate that during ovarian stimulation there are both water retention and augmented filtration of fluid from the vascular to the interstitial compartment. This may be of significance for the pathophysiologic condition in the ovarian hyperstimulation syndrome.
Review of computational fluid dynamics applications in biotechnology processes.
Sharma, C; Malhotra, D; Rathore, A S
2011-01-01
Computational fluid dynamics (CFD) is well established as a tool of choice for solving problems that involve one or more of the following phenomena: flow of fluids, heat transfer,mass transfer, and chemical reaction. Unit operations that are commonly utilized in biotechnology processes are often complex and as such would greatly benefit from application of CFD. The thirst for deeper process and product understanding that has arisen out of initiatives such as quality by design provides further impetus toward usefulness of CFD for problems that may otherwise require extensive experimentation. Not surprisingly, there has been increasing interest in applying CFD toward a variety of applications in biotechnology processing in the last decade. In this article, we will review applications in the major unit operations involved with processing of biotechnology products. These include fermentation,centrifugation, chromatography, ultrafiltration, microfiltration, and freeze drying. We feel that the future applications of CFD in biotechnology processing will focus on establishing CFD as a tool of choice for providing process understanding that can be then used to guide more efficient and effective experimentation. This article puts special emphasis on the work done in the last 10 years.
Molecular dynamics of fluid flow at solid surfaces
Koplik, Joel; Banavar, Jayanth R.; Willemsen, Jorge F.
1989-05-01
Molecular dynamics techniques are used to study the microscopic aspects of several slow viscous flows past a solid wall, where both fluid and wall have a molecular structure. Systems of several thousand molecules are found to exhibit reasonable continuum behavior, albeit with significant thermal fluctuations. In Couette and Poiseuille flow of liquids it is found that the no-slip boundary condition arises naturally as a consequence of molecular roughness, and that the velocity and stress fields agree with the solutions of the Stokes equations. At lower densities slip appears, which can be incorporated into a flow-independent slip-length boundary condition. The trajectories of individual molecules in Poiseuille flow are examined, and it is also found that their average behavior is given by Taylor-Aris hydrodynamic dispersion. An immiscible two-fluid system is simulated by a species-dependent intermolecular interaction. A static meniscus is observed whose contact angle agrees with simple estimates and, when motion occurs, velocity-dependent advancing and receding angles are observed. The local velocity field near a moving contact line shows a breakdown of the no-slip condition and, up to substantial statistical fluctuations, is consistent with earlier predictions of Dussan [AIChE J. 23, 131 (1977)].
Dynamic dielectrophoresis model of multi-phase ionic fluids.
Directory of Open Access Journals (Sweden)
Ying Yan
Full Text Available Ionic-based dielectrophoretic microchips have attracted significant attention due to their wide-ranging applications in electro kinetic and biological experiments. In this work, a numerical method is used to simulate the dynamic behaviors of ionic droplets in a microchannel under the effect of dielectrophoresis. When a discrete liquid dielectric is encompassed within a continuous fluid dielectric placed in an electric field, an electric force is produced due to the dielectrophoresis effect. If either or both of the fluids are ionic liquids, the magnitude and even the direction of the force will be changed because the net ionic charge induced by an electric field can affect the polarization degree of the dielectrics. However, using a dielectrophoresis model, assuming ideal dielectrics, results in significant errors. To avoid the inaccuracy caused by the model, this work incorporates the electrode kinetic equation and defines a relationship between the polarization charge and the net ionic charge. According to the simulation conditions presented herein, the electric force obtained in this work has an error exceeding 70% of the actual value if the false effect of net ionic charge is not accounted for, which would result in significant issues in the design and optimization of experimental parameters. Therefore, there is a clear motivation for developing a model adapted to ionic liquids to provide precise control for the dielectrophoresis of multi-phase ionic liquids.
Computational fluid dynamics (CFD) studies of a miniaturized dissolution system.
Frenning, G; Ahnfelt, E; Sjögren, E; Lennernäs, H
2017-02-08
Dissolution testing is an important tool that has applications ranging from fundamental studies of drug-release mechanisms to quality control of the final product. The rate of release of the drug from the delivery system is known to be affected by hydrodynamics. In this study we used computational fluid dynamics to simulate and investigate the hydrodynamics in a novel miniaturized dissolution method for parenteral formulations. The dissolution method is based on a rotating disc system and uses a rotating sample reservoir which is separated from the remaining dissolution medium by a nylon screen. Sample reservoirs of two sizes were investigated (SR6 and SR8) and the hydrodynamic studies were performed at rotation rates of 100, 200 and 400rpm. The overall fluid flow was similar for all investigated cases, with a lateral upward spiraling motion and central downward motion in the form of a vortex to and through the screen. The simulations indicated that the exchange of dissolution medium between the sample reservoir and the remaining release medium was rapid for typical screens, for which almost complete mixing would be expected to occur within less than one minute at 400rpm. The local hydrodynamic conditions in the sample reservoirs depended on their size; SR8 appeared to be relatively more affected than SR6 by the resistance to liquid flow resulting from the screen.
High-Performance Java Codes for Computational Fluid Dynamics
Riley, Christopher; Chatterjee, Siddhartha; Biswas, Rupak; Biegel, Bryan (Technical Monitor)
2001-01-01
The computational science community is reluctant to write large-scale computationally -intensive applications in Java due to concerns over Java's poor performance, despite the claimed software engineering advantages of its object-oriented features. Naive Java implementations of numerical algorithms can perform poorly compared to corresponding Fortran or C implementations. To achieve high performance, Java applications must be designed with good performance as a primary goal. This paper presents the object-oriented design and implementation of two real-world applications from the field of Computational Fluid Dynamics (CFD): a finite-volume fluid flow solver (LAURA, from NASA Langley Research Center), and an unstructured mesh adaptation algorithm (2D_TAG, from NASA Ames Research Center). This work builds on our previous experience with the design of high-performance numerical libraries in Java. We examine the performance of the applications using the currently available Java infrastructure and show that the Java version of the flow solver LAURA performs almost within a factor of 2 of the original procedural version. Our Java version of the mesh adaptation algorithm 2D_TAG performs within a factor of 1.5 of its original procedural version on certain platforms. Our results demonstrate that object-oriented software design principles are not necessarily inimical to high performance.
Osmoregulation with Focus on Fluid and Solute Dynamics in Tardigradia
DEFF Research Database (Denmark)
Halberg, Kenneth Agerlin
a continuous traffic of compounds in and out of the organism. These demands appear to be in fundamental contradiction however cells and animals achieve so-called “steady-state” by means of an array of transport proteins, which provide a stringent control on the exchange of water and solutes across body......, with the main focus being on fluid and solute dynamics in Tardigrada. For example, the inorganic ion composition of several species was investigated, which revealed that tardigrades contain roughly similar relative contributions of inorganic ions to total osmotic concentration, when compared to closely related...... animal groups. Moreover, it was inferred that cryptobiotic tardigrades (species able to enter a state of latent life) contain a large fraction of organic osmolytes. The mechanisms of organic anion transport in a marine species of tardigrade was investigated pharmacologically, and compared...
Dynamic phase transitions in confined lubricant fluids under shear
Energy Technology Data Exchange (ETDEWEB)
Drummond, Carlos; Israelachvili, Jacob
2001-04-01
A surface force apparatus was used to measure the transient and steady-state friction forces between molecularly smooth mica surfaces confining thin films of squalane, C{sub 30}H{sub 62}, a saturated, branched hydrocarbon liquid. The dynamic friction ''phase diagram'' was determined under different shearing conditions, especially the transitions between stick-slip and smooth sliding ''states'' that exhibited a chaotic stick-slip regime. The apparently very different friction traces exhibited by simple spherical, linear, and branched hydrocarbon films under shear are shown to be due to the much longer relaxation times and characteristic length scales associated with transitions from rest to steady-state sliding, and vice versa, in the case of branched liquids. The physical reasons and tribological implications for the different types of transitions observed with spherical, linear, and branched fluids are discussed.
Computational Fluid Dynamics and Building Energy Performance Simulation
DEFF Research Database (Denmark)
Nielsen, Peter V.; Tryggvason, Tryggvi
An interconnection between a building energy performance simulation program and a Computational Fluid Dynamics program (CFD) for room air distribution will be introduced for improvement of the predictions of both the energy consumption and the indoor environment. The building energy performance...... simulation program requires a detailed description of the energy flow in the air movement which can be obtained by a CFD program. The paper describes an energy consumption calculation in a large building, where the building energy simulation program is modified by CFD predictions of the flow between three...... program and a building energy performance simulation program will improve both the energy consumption data and the prediction of thermal comfort and air quality in a selected area of the building....
Uncertainty quantification in computational fluid dynamics and aircraft engines
Montomoli, Francesco; D'Ammaro, Antonio; Massini, Michela; Salvadori, Simone
2015-01-01
This book introduces novel design techniques developed to increase the safety of aircraft engines. The authors demonstrate how the application of uncertainty methods can overcome problems in the accurate prediction of engine lift, caused by manufacturing error. This in turn ameliorates the difficulty of achieving required safety margins imposed by limits in current design and manufacturing methods. This text shows that even state-of-the-art computational fluid dynamics (CFD) are not able to predict the same performance measured in experiments; CFD methods assume idealised geometries but ideal geometries do not exist, cannot be manufactured and their performance differs from real-world ones. By applying geometrical variations of a few microns, the agreement with experiments improves dramatically, but unfortunately the manufacturing errors in engines or in experiments are unknown. In order to overcome this limitation, uncertainty quantification considers the probability density functions of manufacturing errors...
Computational Fluid Dynamics Analysis of an Evaporative Cooling System
Directory of Open Access Journals (Sweden)
Kapilan N.
2016-11-01
Full Text Available The use of chlorofluorocarbon based refrigerants in the air-conditioning system increases the global warming and causes the climate change. The climate change is expected to present a number of challenges for the built environment and an evaporative cooling system is one of the simplest and environmentally friendly cooling system. The evaporative cooling system is most widely used in summer and in rural and urban areas of India for human comfort. In evaporative cooling system, the addition of water into air reduces the temperature of the air as the energy needed to evaporate the water is taken from the air. Computational fluid dynamics is a numerical analysis and was used to analyse the evaporative cooling system. The CFD results are matches with the experimental results.
Simulating Smoke Filling in Big Halls by Computational Fluid Dynamics
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W. K. Chow
2011-01-01
Full Text Available Many tall halls of big space volume were built and, to be built in many construction projects in the Far East, particularly Mainland China, Hong Kong, and Taiwan. Smoke is identified to be the key hazard to handle. Consequently, smoke exhaust systems are specified in the fire code in those areas. An update on applying Computational Fluid Dynamics (CFD in smoke exhaust design will be presented in this paper. Key points to note in CFD simulations on smoke filling due to a fire in a big hall will be discussed. Mathematical aspects concerning of discretization of partial differential equations and algorithms for solving the velocity-pressure linked equations are briefly outlined. Results predicted by CFD with different free boundary conditions are compared with those on room fire tests. Standards on grid size, relaxation factors, convergence criteria, and false diffusion should be set up for numerical experiments with CFD.
Modeling of a continuous pretreatment reactor using computational fluid dynamics.
Berson, R Eric; Dasari, Rajesh K; Hanley, Thomas R
2006-01-01
Computational fluid dynamic simulations are employed to predict flow characteristics in a continuous auger driven reactor designed for the dilute acid pretreatment of biomass. Slurry containing a high concentration of biomass solids exhibits a high viscosity, which poses unique mixing issues within the reactor. The viscosity increases significantly with a small increase in solids concentration and also varies with temperature. A well-mixed slurry is desirable to evenly distribute acid on biomass, prevent buildup on the walls of the reactor, and provides an uniform final product. Simulations provide flow patterns obtained over a wide range of viscosities and pressure distributions, which may affect reaction rates. Results provide a tool for analyzing sources of inconsistencies in product quality and insight into future design and operating parameters.
Computational methods of the Advanced Fluid Dynamics Model
Energy Technology Data Exchange (ETDEWEB)
Bohl, W.R.; Wilhelm, D.; Parker, F.R.; Berthier, J.; Maudlin, P.J.; Schmuck, P.; Goutagny, L.; Ichikawa, S.; Ninokata, H.; Luck, L.B.
1987-01-01
To more accurately treat severe accidents in fast reactors, a program has been set up to investigate new computational models and approaches. The product of this effort is a computer code, the Advanced Fluid Dynamics Model (AFDM). This paper describes some of the basic features of the numerical algorithm used in AFDM. Aspects receiving particular emphasis are the fractional-step method of time integration, the semi-implicit pressure iteration, the virtual mass inertial terms, the use of three velocity fields, higher order differencing, convection of interfacial area with source and sink terms, multicomponent diffusion processes in heat and mass transfer, the SESAME equation of state, and vectorized programming. A calculated comparison with an isothermal tetralin/ammonia experiment is performed. We conclude that significant improvements are possible in reliably calculating the progression of severe accidents with further development.
Teaching an Undergraduate Course on Computational Fluid Dynamics
Sheikhi, Reza H.
2013-11-01
A new computational fluid dynamics (CFD) course is introduced to Mechanical Engineering undergraduate curriculum at Northeastern University. The main objective is to enable students to make use of CFD in their cooperative-education work, senior capstone project as well as future engineering career. CFD has become an indispensable tool for engineering design & analysis, and it is now available to broad range of users, through commercial software packages. Proper use of these softwares, however, requires basic knowledge of CFD to understand their capabilities and limitations, to be aware of the pitfalls and to interpret the predictions. The course is designed to offer a balanced coverage of essential and applied CFD, with particular emphasis on verification & validation and CFD analysis. Training for a commercial CFD package is an integral part of the course which is facilitated by the use of project-based learning. In this presentation, details of development and implementation of this course will be discussed.
Mutual Dynamics of Swimming Microorganisms and Their Fluid Habitat
Kessler, John O.; Burnett, G. David; Remick, Katherine E.
"Organisms alter their material environment, and their environment constrains and naturally selects organisms." Lenton's [17] statement applies especially well to populations of swimming micro-organisms. The mutual dynamic of themselves and their fluid habitat orders and constrains them, generates concentration-convection patterns [12], [15], enhances transport of metabolites and, at all scales, guides many of their interactions. Our objective is to describe mathematical models sufficient for reaching insights that can further guide theory and experiment. These models necessarily include nonlinear and stochastic features. To illustrate self-organization and the type of experimental statistical inputs available, we present some rather astonishing data concerning the motile bacteria Bacillus subtilis and hydrodynamics associated with their activity. The inescapable interdependence of physics and biology emerges from the analysis.
Osmoregulation with Focus on Fluid and Solute Dynamics in Tardigradia
DEFF Research Database (Denmark)
Halberg, Kenneth Agerlin
, with the main focus being on fluid and solute dynamics in Tardigrada. For example, the inorganic ion composition of several species was investigated, which revealed that tardigrades contain roughly similar relative contributions of inorganic ions to total osmotic concentration, when compared to closely related...... animal groups. Moreover, it was inferred that cryptobiotic tardigrades (species able to enter a state of latent life) contain a large fraction of organic osmolytes. The mechanisms of organic anion transport in a marine species of tardigrade was investigated pharmacologically, and compared...... to that of insects. These data showed that organic anion transport is localized to the midgut epithelium and that the transport is both active and transporter mediated with a pharmacological profile similar to that of insects. Tardigrades survive in a variety of osmotic environments (semi-terrestrial, limnic...
Transport Properties of Fluids in Micropores by Molecular Dynamics Simulation
Institute of Scientific and Technical Information of China (English)
LIU, Ying-Chun(刘迎春); WANG, Qi(王琦); Lü, Ling-Hong(吕玲红)
2004-01-01
The transport properties of fluid argon in micropores, i.e. diffusivity and viscosity, were studied by molecular dynamics simulations. The effects of pore width, temperature and density on diffusivity and viscosity were analyzed in micropores with pore widths from 0.8 to 4.0 nm. The results show that the diffusivity in micropores is much lower than the bulk diffusivity, and it decreases as the pore width decreases; but the viscosity in micropores is significantly larger than the bulk one, and it increases sharply in narrow micropores. The diffusivity in channel parallel direction is obviously larger than that in channel perpendicular direction. The temperature and density are important factors that obviously affect diffusivity and viscosity in micropores.
Fluid dynamics in airway bifurcations: III. Localized flow conditions.
Martonen, T B; Guan, X; Schreck, R M
2001-04-01
Localized flow conditions (e.g., backflows) in transition regions between parent and daughter airways of bifurcations were investigated using a computational fluid dynamics software code (FIDAP) with a Cray T90 supercomputer. The configurations of the bifurcations were based on Schreck s (1972) laboratory models. The flow intensities and spatial regions of reversed motion were simulated for different conditions. The effects of inlet velocity profiles, Reynolds numbers, and dimensions and orientations of airways were addressed. The computational results showed that backflow was increased for parabolic inlet conditions, larger Reynolds numbers, and larger daughter-to-parent diameter ratios. This article is the third in a systematic series addressed in this issue; the first addressed primary velocity patterns and the second discussed secondary currents.
Computational fluid dynamics for defect control in semiconductor processing
Kempka, S. N.; Geller, A. S.
Finite element simulations of mixed convection flow (Re less than 100, Gr less than 10(exp 6)) are presented for two gas flow reactors characteristic of those used in the manufacture of microchips. The simulations demonstrate the usefulness of FIDAP (a finite element, Navier-Stokes code developed by Fluid Dynamics International, Inc.) as a tool to design new reactors and to assess the effects of varying operating conditions in present reactors. The calculations predict the existence of thermal plumes and recirculation regions within reactors. These flow nonuniformities are important since they can result in fatal defects in microchips. Comparisons between solutions obtained using a Boussinesq model and FIDAP's variable density model are presented. The FIDAP calculations agree with previous simulations using more detailed models, supporting the use of FIDAP as a design tool in the semiconductor industry.
Dynamic response of shear thickening fluid under laser induced shock
Wu, Xianqian; Zhong, Fachun; Yin, Qiuyun; Huang, Chenguang
2015-02-01
The dynamic response of the 57 vol./vol. % dense spherical silica particle-polyethylene glycol suspension at high pressure was investigated through short pulsed laser induced shock experiments. The measured back free surface velocities by a photonic Doppler velocimetry showed that the shock and the particle velocities decreased while the shock wave transmitted in the shear thickening fluid (STF), from which an equation of state for the STF was obtained. In addition, the peak stress decreased and the absorbed energy increased rapidly with increasing the thickness for a thin layer of the STF, which should be attributed to the impact-jammed behavior through compression of particle matrix, the deformation or crack of the hard-sphere particles, and the volume compression of the particles and the polyethylene glycol.
Mapping flow distortion on oceanographic platforms using computational fluid dynamics
Directory of Open Access Journals (Sweden)
N. O'Sullivan
2013-10-01
Full Text Available Wind speed measurements over the ocean on ships or buoys are affected by flow distortion from the platform and by the anemometer itself. This can lead to errors in direct measurements and the derived parametrisations. Here we computational fluid dynamics (CFD to simulate the errors in wind speed measurements caused by flow distortion on the RV Celtic Explorer. Numerical measurements were obtained from the finite-volume CFD code OpenFOAM, which was used to simulate the velocity fields. This was done over a range of orientations in the test domain from −60 to +60° in increments of 10°. The simulation was also set up for a range of velocities, ranging from 5 to 25 m s−1 in increments of 0.5 m s−1. The numerical analysis showed close agreement to experimental measurements.
Computational Fluid Dynamics in Aerospace Industry in India
Directory of Open Access Journals (Sweden)
K. P. Singh
2010-10-01
Full Text Available The role of computational fluid dynamics (CFD in the design of fighter aircraft, transport aircraft, launch vehicle and missiles in India is explained. Indigenous developments of grid generators, 3-D Euler and Navier-Stokes solvers using state-of-the-art numerical techniques and physical models have been described. Applications of these indigenous softwares for the prediction of various complex aerodynamic flows over a wide range of Mach number, angle of attacks, are presented. Emergence of CFD methods as an efficient tool for aerospace vehicle design is highlighted.Defence Science Journal, 2010, 60(6, pp.639-652, DOI:http://dx.doi.org/10.14429/dsj.60.582
Evaluation of nacelle drag using Computational Fluid Dynamics
Directory of Open Access Journals (Sweden)
Luis Gustavo Trapp
2010-08-01
Full Text Available Thrust and drag components must be defined and properly accounted in order to estimate aircraft performance, and this hard task is particularty essential for propulsion system where drag components are functions of engine operating conditions. The present work describes a numerical method used to calculate the drag in different nacelles, long and short ducted. Two- and three-dimensional calculations were performed, solving the Reynolds Averaged Navier-Stokes (RANS equations with a commercial Computational Fluid Dynamics (CFD code. It is then possible to obtain four drag components: wave, induced, viscous and spurious drag using a far-field formulation. An expression in terms of entropy variations was shown and drag for different nacelle geometries was estimated.
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.
Development of a Laminar Flow Bioreactor by Computational Fluid Dynamics
Directory of Open Access Journals (Sweden)
Meir Israelowitz
2012-01-01
Full Text Available The purpose of this study is to improve the design of a bioreactor for growing bone and other three-dimensional tissues using a computational fluid dynamics (CFD software to simulate flow through a porous scaffold, and to recommend design changes based on the results. Basic requirements for CFD modeling were that the flow in the reactor should be laminar and any flow stagnation should be avoided in order to support cellular growth within the scaffold. We simulated three different designs with different permeability values of the scaffold and tissue. Model simulation addressed flow patterns in combination with pressure distribution within the bioreactor. Pressure build-up and turbulent flow within the reactor was solved by introduction of an integrated bypass system for pressure release. The use of CFD afforded direct feedback to optimize the bioreactor design.
Parallel Computational Fluid Dynamics: Current Status and Future Requirements
Simon, Horst D.; VanDalsem, William R.; Dagum, Leonardo; Kutler, Paul (Technical Monitor)
1994-01-01
One or the key objectives of the Applied Research Branch in the Numerical Aerodynamic Simulation (NAS) Systems Division at NASA Allies Research Center is the accelerated introduction of highly parallel machines into a full operational environment. In this report we discuss the performance results obtained from the implementation of some computational fluid dynamics (CFD) applications on the Connection Machine CM-2 and the Intel iPSC/860. We summarize some of the experiences made so far with the parallel testbed machines at the NAS Applied Research Branch. Then we discuss the long term computational requirements for accomplishing some of the grand challenge problems in computational aerosciences. We argue that only massively parallel machines will be able to meet these grand challenge requirements, and we outline the computer science and algorithm research challenges ahead.
Fluid dynamics of aortic root dilation in Marfan syndrome
Querzoli, Giorgio; Espa, Stefania; Costantini, Martina; Sorgini, Francesca
2014-01-01
Aortic root dilation and propensity to dissection are typical manifestations of the Marfan Syndrome (MS), a genetic defect leading to the degeneration of the elastic fibres. Dilation affects the structure of the flow and, in turn, altered flow may play a role in vessel dilation, generation of aneurysms, and dissection. The aim of the present work is the investigation in-vitro of the fluid dynamic modifications occurring as a consequence of the morphological changes typically induced in the aortic root by MS. A mock-loop reproducing the left ventricle outflow tract and the aortic root was used to measure time resolved velocity maps on a longitudinal symmetry plane of the aortic root. Two dilated model aortas, designed to resemble morphological characteristics typically observed in MS patients, have been compared to a reference, healthy geometry. The aortic model was designed to quantitatively reproduce the change of aortic distensibility caused by MS. Results demonstrate that vorticity released from the valve ...
On Computational Fluid Dynamics Tools in Architectural Design
DEFF Research Database (Denmark)
Kirkegaard, Poul Henning; Hougaard, Mads; Stærdahl, Jesper Winther
engineering computational fluid dynamics (CFD) simulation program ANSYS CFX and a CFD based representative program RealFlow are investigated. These two programs represent two types of CFD based tools available for use during phases of an architectural design process. However, as outlined in two case studies...... the durability of the two program types for simulation of flow is strongly depended of the purpose. One case presents results obtained with the programs with respect to the accuracy and physical behaviour of the flow. Another case deals with wind flow around a complex building design, the roof of the new Utzon...... Centre in Aalborg, Denmark. The obtained results show that detailed and accurate flow predictions can be obtained using a simulation tool like ANSYS CFX. On the other hand RealFlow provides satisfactory flow results for evaluation of a proposed building shape in an early phase of a design process...
Computational fluid dynamics of developing avian outflow tract heart valves.
Bharadwaj, Koonal N; Spitz, Cassie; Shekhar, Akshay; Yalcin, Huseyin C; Butcher, Jonathan T
2012-10-01
Hemodynamic forces play an important role in sculpting the embryonic heart and its valves. Alteration of blood flow patterns through the hearts of embryonic animal models lead to malformations that resemble some clinical congenital heart defects, but the precise mechanisms are poorly understood. Quantitative understanding of the local fluid forces acting in the heart has been elusive because of the extremely small and rapidly changing anatomy. In this study, we combine multiple imaging modalities with computational simulation to rigorously quantify the hemodynamic environment within the developing outflow tract (OFT) and its eventual aortic and pulmonary valves. In vivo Doppler ultrasound generated velocity profiles were applied to Micro-Computed Tomography generated 3D OFT lumen geometries from Hamburger-Hamilton (HH) stage 16-30 chick embryos. Computational fluid dynamics simulation initial conditions were iterated until local flow profiles converged with in vivo Doppler flow measurements. Results suggested that flow in the early tubular OFT (HH16 and HH23) was best approximated by Poiseuille flow, while later embryonic OFT septation (HH27, HH30) was mimicked by plug flow conditions. Peak wall shear stress (WSS) values increased from 18.16 dynes/cm(2) at HH16 to 671.24 dynes/cm(2) at HH30. Spatiotemporally averaged WSS values also showed a monotonic increase from 3.03 dynes/cm(2) at HH16 to 136.50 dynes/cm(2) at HH30. Simulated velocity streamlines in the early heart suggest a lack of mixing, which differed from classical ink injections. Changes in local flow patterns preceded and correlated with key morphogenetic events such as OFT septation and valve formation. This novel method to quantify local dynamic hemodynamics parameters affords insight into sculpting role of blood flow in the embryonic heart and provides a quantitative baseline dataset for future research.
Light-Front Dynamics Of Massive Vector Chern-Simons Gravity
Aragone, C; Khoudeir, A
1993-01-01
We present a second order gravity action which consists of ordinary Einstein action augmented by a first-order, vector like, Chern-Simons quasi topological term. This theory is ghost-free and propagates a pure spin-2 mode. It is diffeomorphism invariant, although its local Lorentz invariance has been spontaneuosly broken. We perform the light-front (LF) analysis for both the linearized system and the exact curved model. In constrast to the 2+1 canonical analysis, in the quasi LF coordinates the differential constraints can be solved. Its solution is presented here.
Ferrarini, M.; Varoli, V.; Favalli, A.; Caresana, M.; Pedersen, B.
2010-02-01
This paper describes a wide dynamic range neutron monitor based on a BF 3 neutron detector. The detector is used in current mode, and front-end electronics based on a logarithmic amplifier are used in order to have a measurement capability ranging over many orders of magnitude. The system has been calibrated at the Polytechnic of Milan, CESNEF, with an AmBe neutron source, and has been tested in a pulsed field at the PUNITA facility at JRC, Ispra. The detector has achieved a dynamic range of over 6 orders of magnitude, being able to measure single neutron pulses and showing saturation-free response for a reaction rate up to 10 6 s -1. It has also proved effective in measuring the PUNITA facility pulse integral fluence.
Energy Technology Data Exchange (ETDEWEB)
Ferrarini, M., E-mail: michele.ferrarini@polimi.i [Politecnico di Milano, Dipartimento Energia, via G. Ponzio 34/3, I-20133 Milano (Italy); Fondazione CNAO, via Caminadella 16, 20123 Milano (Italy); Varoli, V. [Politecnico di Milano, Dipartimento Energia, via G. Ponzio 34/3, I-20133 Milano (Italy); Favalli, A. [European Commission, Joint Research Centre, Institute for the Protection and Security of Citizen, TP 800, Via E. Fermi, 21027 Ispra (Vatican City State, Holy See) (Italy); Caresana, M. [Politecnico di Milano, Dipartimento Energia, via G. Ponzio 34/3, I-20133 Milano (Italy); Pedersen, B. [European Commission, Joint Research Centre, Institute for the Protection and Security of Citizen, TP 800, Via E. Fermi, 21027 Ispra (Italy)
2010-02-01
This paper describes a wide dynamic range neutron monitor based on a BF{sub 3} neutron detector. The detector is used in current mode, and front-end electronics based on a logarithmic amplifier are used in order to have a measurement capability ranging over many orders of magnitude. The system has been calibrated at the Polytechnic of Milan, CESNEF, with an AmBe neutron source, and has been tested in a pulsed field at the PUNITA facility at JRC, Ispra. The detector has achieved a dynamic range of over 6 orders of magnitude, being able to measure single neutron pulses and showing saturation-free response for a reaction rate up to 10{sup 6} s{sup -1}. It has also proved effective in measuring the PUNITA facility pulse integral fluence.
A fully dynamic magneto-rheological fluid damper model
Jiang, Z.; Christenson, R. E.
2012-06-01
Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, thus reducing structural damage and preventing failure. Semiactive control devices have received significant attention in recent years. The magneto-rheological (MR) fluid damper is a promising type of semiactive device for civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate-dependent, both as a function of the displacement across the MR damper and the command current being supplied to the MR damper. As such, to develop control algorithms that take maximum advantage of the unique features of the MR damper, accurate models must be developed to describe its behavior for both displacement and current. In this paper, a new MR damper model that includes a model of the pulse-width modulated (PWM) power amplifier providing current to the damper, a proposed model of the time varying inductance of the large-scale 200 kN MR dampers coils and surrounding MR fluid—a dynamic behavior that is not typically modeled—and a hyperbolic tangent model of the controllable force behavior of the MR damper is presented. Validation experimental tests are conducted with two 200 kN large-scale MR dampers located at the Smart Structures Technology Laboratory (SSTL) at the University of Illinois at Urbana-Champaign and the Lehigh University Network for Earthquake Engineering Simulation (NEES) facility. Comparison with experimental test results for both prescribed motion and current and real-time hybrid simulation of semiactive control of the MR damper shows that the proposed MR damper model can accurately predict the fully dynamic behavior of the large-scale 200 kN MR damper.
Non-Ideal Compressible Fluid Dynamics: A Challenge for Theory
Kluwick, A.
2017-03-01
The possibility that compression as well as rarefaction shocks may form in single phase vapours was envisaged first by Bethe (1942). However calculations based on the Van der Waals equation of state indicated that the latter type of shock is possible only if the specific heat at constant volume cv divided by the universal gas constant R is larger than about 17.5 which he considered too large to be satisfied by real fluids. This conclusion was contested by Thompson (1971) who showed that the type of shock capable of forming in arbitrary fluids is determined by the sign of the thermodynamic quantity to which he referred to as fundamental derivative of gas dynamics. Here v, p, s and c denote the specific volume, the pressure, the entropy and the speed of sound. Thompson and co-workers also showed that the required condition for the existence of rarefaction shocks, that Γ may take on negative values, is indeed satisfied for a number of hydrocarbon and fluorocarbon vapours. This finding spawned a burst of theoretical studies elaborating on the unusual and often counterintuitive behaviour of shocks with rarefaction shocks present. These produced both results of theoretical character but also results suggesting the practical importance of Non-Ideal Compressible Fluid Dynamics in general. The present paper addresses some of the challenges encountered in connection with the theoretical treatment of the associated flow behaviour. Weakly nonlinear acoustic waves of finite amplitude serve as a starting point. Here mixed rather than strictly positive nonlinearity generates a wealth of phenomena not possible in perfect gases. Examples of steady flows where these non-classical effects play a decisive role (and which may be useful also for future experimental work) are quasi one-dimensional nozzle flows and transonic two-dimensional flows past corners. The study of viscous effects concentrates on laminar flows of boundary layer type. Here non-classical phenomena are caused by the
Studying microstructural dynamics of complex fluids with particle tracking microrheology
Breedveld, Victor
2004-11-01
Over the last decade, particle tracking microrheology has matured as a new tool for complex fluids research. The main advantages of microrheology over traditional macroscopic rheometry are: the required sample size is extremely small ( ˜ 1 microliter); local viscoelastic properties in a sample can be probed with high spatial resolution ( ˜1-10 micrometer); and the sample is not disturbed by moving rheometer parts. I will present two examples of recent work in my group that highlight how these characteristics can be exploited to acquire unique information about the microstructure of complex fluids. First, we have studied protein unfolding. Traditionally, protein unfolding is studied with spectroscopic techniques (circular dichroism, NMR, fluorescence). Although viscosity has been listed in textbooks as a suitable technique, few -if any- quantitative rheological studies of unfolding have been reported, mainly due to technical difficulties. With microrheology, we have been able to quantify the size of the folded and unfolded protein, as well as the Gibbs free energy of unfolding, for aqueous bovine serum albumine solutions upon addition of urea as a denaturant. The results are in excellent agreement with literature data. Secondly, we have developed new technology for studying the microstructural dynamics of solvent-responsive complex fluids. In macroscopic rheometry it is virtually impossible to change solvent composition and measure the rheological response of a sample. By integrating microfluidics and microrheology we have been able to overcome this barrier: due to the micrometer lengthscales in microfluidiv devices, diffusive timescales in a dialysis set-up become short enough to achieve rapid and reversible changes in sample composition, without affecting the concentration of macromolecular components. Our dialysis cell for microrheology is a unique tool for studying the dynamics of structural and rheological changes induced by solvent composition. I will
Fluid dynamics of competitive swimming: An experimental study
Wei, T.; Voorhees, A.; Mark, R.; Mittal, R.
2004-11-01
The world of competitive swimming is dynamic. Swimmers today are bigger, stronger and faster than they ever have been. The training regimen of an elite athlete includes not only endless practice of his or her skills, but also a carefully planned diet, strength and endurance training, and hours of mental preparation. Within this framework, researchers from Rutgers and George Washington Universities have teamed with USA Swimming to develop advanced, fluid dynamics based training and analysis tools for current and future Olympic swimmers. The focus of this presentation will be on the objectives, methodologies and early outcomes of DPIV measurements of flow around swimmers. Testing was conducted at the Olympic training center in Colorado Springs and focussed specifically on the dolphin kick, an undulating motion swimmers use at the beginning of a race and after pushing off from the wall during a turn. Movies of flow measurements around swimmers, including Beth Botsford, the 1996 Olympic Gold Medalist in the 100 m backstroke, will be presented.
Climate dynamics and fluid mechanics: Natural variability and related uncertainties
Ghil, Michael; Simonnet, Eric; 10.1016/j.physd.2008.03.036
2010-01-01
The purpose of this review-and-research paper is twofold: (i) to review the role played in climate dynamics by fluid-dynamical models; and (ii) to contribute to the understanding and reduction of the uncertainties in future climate-change projections. To illustrate the first point, we focus on the large-scale, wind-driven flow of the mid-latitude oceans which contribute in a crucial way to Earth's climate, and to changes therein. We study the low-frequency variability (LFV) of the wind-driven, double-gyre circulation in mid-latitude ocean basins, via the bifurcation sequence that leads from steady states through periodic solutions and on to the chaotic, irregular flows documented in the observations. This sequence involves local, pitchfork and Hopf bifurcations, as well as global, homoclinic ones. The natural climate variability induced by the LFV of the ocean circulation is but one of the causes of uncertainties in climate projections. Another major cause of such uncertainties could reside in the structural ...
APS presents prizes in fluid dynamics and plasma physics
Energy Technology Data Exchange (ETDEWEB)
1992-12-01
This article reviews the presentation of the American Physical Society awards in fluid dynamics and plasma physics. The recipient of the plasma physics James Clerk Maxwell Prize was John M. Green for contributions to the theory of magnetohydrodynamics equilibria and ideal and resistive instabilities, for discovering the inverse scattering transform leading to soliton solutions of many nonlinear partial differential equations and for inventing the residue method of determining the transition to global chaos. The excellence in Plasma Physics Research Award was presented to Nathaniel A. Fisch for theoretical investigations of noninductive current generation in toroidally confined plasma. Wim Pieter Leemans received the Simon Ramo Award for experimental and simulational contributions to laser-plasma physics. William R. Sears was given the 1992 Fuid Dynamics Prize for contributions to the study of steady and unsteady aerodynamics, aeroacoustics, magnetoaerodynamics,and wind tunnel design. William C. Reynolds received the Otto Laporte Award for experimental, theoretical, and computational work in turbulence modeling and control and leadership in direct numerical simulation and large eddy simulation.
Dynamic self-consistent field theory for unentangled homopolymer fluids
Mihajlovic, Maja; Lo, Tak Shing; Shnidman, Yitzhak
2005-10-01
We present a lattice formulation of a dynamic self-consistent field (DSCF) theory that is capable of resolving interfacial structure, dynamics, and rheology in inhomogeneous, compressible melts and blends of unentangled homopolymer chains. The joint probability distribution of all the Kuhn segments in the fluid, interacting with adjacent segments and walls, is approximated by a product of one-body probabilities for free segments interacting solely with an external potential field that is determined self-consistently. The effect of flow on ideal chain conformations is modeled with finitely extensible, nonlinearly elastic dumbbells in the Peterlin approximation, and related to stepping probabilities in a random walk. Free segment and stepping probabilities generate statistical weights for chain conformations in a self-consistent field, and determine local volume fractions of chain segments. Flux balance across unit lattice cells yields mean field transport equations for the evolution of free segment probabilities and of momentum densities on the Kuhn length scale. Diffusive and viscous contributions to the fluxes arise from segmental hops modeled as a Markov process, with transition rates reflecting changes in segmental interaction, kinetic energy, and entropic contributions to the free energy under flow. We apply the DSCF equations to study both transient and steady-state interfacial structure, flow, and rheology in a sheared planar channel containing either a one-component melt or a phase-separated, two-component blend.
Directory of Open Access Journals (Sweden)
Azrar A.
2012-07-01
Full Text Available The dynamic instabilities of Carbon NanoTubes (CNTs conveying fluid are modeled and numerically simulated based on the nonlocal elasticity theory. The small scale parameter and the fluid-tube interaction effects on the dynamic behaviors of the CNT-fluid system as well as the instabilities induced by the fluid-velocity are investigated. The critical fluid-velocity and frequency-amplitude relationships as well as the flutter and divergence instability types and the associated time responses can be obtained based on the presented methodological approach.
Experimental Observation of Differences in the Dynamic Response of Newtonian and Viscoelastic Fluids
Castrejon-Pita, J R; Castrejon-Pita, A A; Huelsz, G
2003-01-01
In this paper we present an experimental study of the dynamic responses of a Newtonian fluid and a Maxwellian fluid under an oscillating pressure gradient. We use laser Doppler anemometry in order to determine the velocity of each fluid inside a cylindrical tube. In the case of the Newtonian fluid, the dissipative nature is observed and the response obeys the Zhou and Sheng universality (PRB 39, 12027 (1989)). In the dynamic response of the Maxwellian fluid an enhancement at the frequencies predicted by the corresponding theory (PRE 39, 12027 (1989)) is observed.
On the tribological characteristics of dynamically loaded journal bearing with micropolar fluids
Institute of Scientific and Technical Information of China (English)
WANG; Xiaoli; WANG; Kongying; ZHU; Keqin
2004-01-01
The addition of the additives to the lubricant oil to enhance the characteristics of the lubricant will influence the performance of the bearings. Based on the theory of micropolar fluids, the tribological characteristics of a dynamically-loaded journal bearing are numerically studied. Comparisons are made between the Newtonian fluids and the micropolar fluids. It is shown that for a dynamically-loaded journal bearing, the micropolar fluids yield an increase not only in the friction force, but also in the friction coefficient. In addition, the oil film pressure and the oil film thickness are obviously higher than that of Newtonian fluids.
Norby, W. P.; Ladd, J. A.; Yuhas, A. J.
1996-01-01
A procedure has been developed for predicting peak dynamic inlet distortion. This procedure combines Computational Fluid Dynamics (CFD) and distortion synthesis analysis to obtain a prediction of peak dynamic distortion intensity and the associated instantaneous total pressure pattern. A prediction of the steady state total pressure pattern at the Aerodynamic Interface Plane is first obtained using an appropriate CFD flow solver. A corresponding inlet turbulence pattern is obtained from the CFD solution via a correlation linking root mean square (RMS) inlet turbulence to a formulation of several CFD parameters representative of flow turbulence intensity. This correlation was derived using flight data obtained from the NASA High Alpha Research Vehicle flight test program and several CFD solutions at conditions matching the flight test data. A distortion synthesis analysis is then performed on the predicted steady state total pressure and RMS turbulence patterns to yield a predicted value of dynamic distortion intensity and the associated instantaneous total pressure pattern.
Capturing the 3D Motion of an Infalling Galaxy via Fluid Dynamics
Su, Yuanyuan; Kraft, Ralph P.; Nulsen, Paul E. J.; Roediger, Elke; Forman, William R.; Churazov, Eugene; Randall, Scott W.; Jones, Christine; Machacek, Marie E.
2017-01-01
The Fornax Cluster is the nearest (≤slant 20 Mpc) galaxy cluster in the southern sky. NGC 1404 is a bright elliptical galaxy falling through the intracluster medium (ICM) of the Fornax Cluster. The sharp leading edge of NGC 1404 forms a classical “cold front” that separates 0.6 keV dense interstellar medium and 1.5 keV diffuse ICM. We measure the angular pressure variation along the cold front using a very deep (670 ks) Chandra X-ray observation. We are taking the classical approach—using stagnation pressure to determine a substructure’s speed—to the next level by not only deriving a general speed but also directionality, which yields the complete velocity field as well as the distance of the substructure directly from the pressure distribution. We find a hydrodynamic model consistent with the pressure jump along NGC 1404's atmosphere measured in multiple directions. The best-fit model gives an inclination of 33° and a Mach number of 1.3 for the infall of NGC 1404, in agreement with complementary measurements of the motion of NGC 1404. Our study demonstrates the successful treatment of a highly ionized ICM as ideal fluid flow, in support of the hypothesis that magnetic pressure is not dynamically important over most of the virial region of galaxy clusters.
Collapse dynamics and runout of dense granular materials in a fluid.
Topin, V; Monerie, Y; Perales, F; Radjaï, F
2012-11-02
We investigate the effect of an ambient fluid on the dynamics of collapse and spread of a granular column simulated by means of the contact dynamics method interfaced with computational fluid dynamics. The runout distance is found to increase as a power law with the aspect ratio of the column, and, surprisingly, for a given aspect ratio and packing fraction, it may be similar in the grain-inertial and fluid-inertial regimes but with considerably longer duration in the latter case. We show that the effect of fluid in viscous and fluid-inertial regimes is to both reduce the kinetic energy during collapse and enhance the flow by lubrication during spread. Hence, the runout distance in a fluid may be below or equal to that in the absence of fluid due to compensation between those effects.
Evaluation of a front-end ASIC for the readout of PMTs in large dynamic range
Wu, Weihao; Liang, Yu; Yu, Li; Liu, Jianfeng; Liu, Shubin; An, Qi
2015-01-01
The Large High Altitude Air Shower Observatory (LHAASO) project has been proposed for the survey and study of cosmic rays. In the LHAASO project, the Water Cherenkov Detector Array (WCDA) is one of major detectors for searching gamma ray sources. A Charge-to-Time Convertor (QTC) ASIC (Application Specification Integrated Circuit) fabricated in Global Foundry 0.35 {\\mu}m CMOS technology, has been developed for readout of Photomultiplier Tubes (PMTs) in the WCDA. This paper focuses on the evaluation of this front-end readout ASIC performance. Test results indicate that the time resolution is better than 400 ps and the charge resolution is better than 1% with large input signals and remains better than 15% @ 1 Photo Electron (P.E.), both beyond the application requirement. Moreover, this ASIC has a weak ambient temperature dependence, low input rate dependence and high channel-to-channel isolation.
Energy Technology Data Exchange (ETDEWEB)
Sentman, L.H.; Nayfeh, M.H.
1983-12-01
This research is an integrated theoretical and experimental investigation of the nonlinear interactions which may occur between the chemical kinetics, the fluid dynamics and the unstable resonator of a continuous wave fluid flow laser. The objectives of this grant were to measure the frequency and amplitude of the time dependent pulsations in the power spectral output which have been predicted to occur in cw chemical lasers employing unstable resonators to extract power.
Gibson, J. C.; Carbotte, S. M.; Han, S.; Carton, H. D.; Canales, P.; Nedimovic, M. R.
2013-12-01
Evidence of active fluid flow and the nature of the sediment section near the Cascadia deformation front are explored using multi-channel (MCS) seismic and multi-beam sonar data collected in summer 2012 using the R/V Marcus G. Langseth during the Juan de Fuca Ridge to Trench Survey. The MCS data were collected along two full plate transects (the 'Oregon' and 'Washington' transects) and one trench parallel line using a 6600 cubic inch source, and an 8 km streamer with 636 channels (12.5 m spacing). The MCS data pre-stack processing sequence includes geometry definition, trace editing, F-K filter, and deconvolution. Velocity analysis is performed via semblance and constant velocity stacks in order to create a velocity model of the sediments and upper oceanic crust. The traces are then stacked, and post-stack time migrated. The sonar data were collected using the R/V Langseth's Kongsberg EM122 1°x1° multi-beam sonar with 288 beams and 432 total soundings across track. Using MB-system the sonar data are cleaned, and the bathymetry data are then gridded at 35 m, while the backscatter data are gridded at 15 m. From the high-resolution mapping data 48 pockmarks varying in diameter from 50 m - 1 km are identified within 60 km outboard of the deformation front. The surface expression of these large features in an area of heavy sedimentation is likely indicative of active fluid flow. In order to gain sub-seafloor perspective on these features the MCS data are draped below the bathymetry/backscatter grids using QPS Fledermaus. From this perspective, specific locations for detailed velocity and attribute analysis of the sediment section are chosen. Sediment velocity and attribute analysis also provide insight into apparent differences in the sediment section and décollement formation along the Oregon and Washington plate transects. While both lines intersect areas of dense pockmark concentration, the area around the Oregon transect has been shown to contain a continuous
Code Verification of the HIGRAD Computational Fluid Dynamics Solver
Energy Technology Data Exchange (ETDEWEB)
Van Buren, Kendra L. [Los Alamos National Laboratory; Canfield, Jesse M. [Los Alamos National Laboratory; Hemez, Francois M. [Los Alamos National Laboratory; Sauer, Jeremy A. [Los Alamos National Laboratory
2012-05-04
The purpose of this report is to outline code and solution verification activities applied to HIGRAD, a Computational Fluid Dynamics (CFD) solver of the compressible Navier-Stokes equations developed at the Los Alamos National Laboratory, and used to simulate various phenomena such as the propagation of wildfires and atmospheric hydrodynamics. Code verification efforts, as described in this report, are an important first step to establish the credibility of numerical simulations. They provide evidence that the mathematical formulation is properly implemented without significant mistakes that would adversely impact the application of interest. Highly accurate analytical solutions are derived for four code verification test problems that exercise different aspects of the code. These test problems are referred to as: (i) the quiet start, (ii) the passive advection, (iii) the passive diffusion, and (iv) the piston-like problem. These problems are simulated using HIGRAD with different levels of mesh discretization and the numerical solutions are compared to their analytical counterparts. In addition, the rates of convergence are estimated to verify the numerical performance of the solver. The first three test problems produce numerical approximations as expected. The fourth test problem (piston-like) indicates the extent to which the code is able to simulate a 'mild' discontinuity, which is a condition that would typically be better handled by a Lagrangian formulation. The current investigation concludes that the numerical implementation of the solver performs as expected. The quality of solutions is sufficient to provide credible simulations of fluid flows around wind turbines. The main caveat associated to these findings is the low coverage provided by these four problems, and somewhat limited verification activities. A more comprehensive evaluation of HIGRAD may be beneficial for future studies.
Simulating the Dynamic Behavior of Shear Thickening Fluids
Ozgen, Oktar; Brown, Eric
2015-01-01
While significant research has been dedicated to the simulation of fluids, not much attention has been given to exploring new interesting behavior that can be generated with the different types of non-Newtonian fluids with non-constant viscosity. Going in this direction, this paper introduces a computational model for simulating the interesting phenomena observed in non-Newtonian shear thickening fluids, which are fluids where the viscosity increases with increased stress. These fluids have unique and unconventional behavior, and they often appear in real world scenarios such as when sinking in quicksand or when experimenting with popular cornstarch and water mixtures. While interesting behavior of shear thickening fluids can be easily observed in the real world, the most interesting phenomena of these fluids have not been simulated before in computer graphics. The fluid exhibits unique phase changes between solid and liquid states, great impact resistance in its solid state and strong hysteresis effects. Our...
Dynamic modeling of fluid power transmissions for wind turbines
Diepeveen, N.F.B.; Jarquin Laguna, A.
2011-01-01
Fluid power transmission for wind turbines is quietly gaining more ground/interest. The principle of the various concepts presented so far is to convert aerodynamic torque of the rotor blades into a pressurized fluid flow by means of a positive displacement pump. At the other end of the fluid power
Dynamic modeling of fluid power transmissions for wind turbines
Diepeveen, N.F.B.; Jarquin Laguna, A.
2011-01-01
Fluid power transmission for wind turbines is quietly gaining more ground/interest. The principle of the various concepts presented so far is to convert aerodynamic torque of the rotor blades into a pressurized fluid flow by means of a positive displacement pump. At the other end of the fluid power
Garcia-Lechuga, Mario; Solis, Javier; Siegel, Jan
2016-04-01
Several studies in dielectrics have reported the presence of a thin heat-affected layer underneath the ablation crater produced by femtosecond laser irradiation. In this work, we present a time-resolved microscopy technique that is capable of monitoring the formation dynamics of this layer and apply it to the study of a phosphate glass exposed to single pulses below the ablation threshold. A few nanoseconds after laser excitation, a melt front interface can be detected, which propagates into the bulk, gradually slowing down its speed. By means of image analysis combined with optical modeling, we are able to determine the temporal evolution of the layer thickness and its refractive index. Initially, a strong transient decrease in the refractive index is observed, which partially recovers afterwards. The layer resolidifies after approximately 1 μs after excitation, featuring a maximum thickness of several hundreds of nanometers.
Energy Technology Data Exchange (ETDEWEB)
Garcia-Lechuga, Mario, E-mail: mario@io.cfmac.csic.es, E-mail: j.siegel@io.cfmac.csic.es; Solis, Javier; Siegel, Jan, E-mail: mario@io.cfmac.csic.es, E-mail: j.siegel@io.cfmac.csic.es [Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, 28006 Madrid (Spain)
2016-04-25
Several studies in dielectrics have reported the presence of a thin heat-affected layer underneath the ablation crater produced by femtosecond laser irradiation. In this work, we present a time-resolved microscopy technique that is capable of monitoring the formation dynamics of this layer and apply it to the study of a phosphate glass exposed to single pulses below the ablation threshold. A few nanoseconds after laser excitation, a melt front interface can be detected, which propagates into the bulk, gradually slowing down its speed. By means of image analysis combined with optical modeling, we are able to determine the temporal evolution of the layer thickness and its refractive index. Initially, a strong transient decrease in the refractive index is observed, which partially recovers afterwards. The layer resolidifies after approximately 1 μs after excitation, featuring a maximum thickness of several hundreds of nanometers.
In-vitro interferometric characterization of dynamic fluid layers on contact lenses
Primeau, Brian C.; Greivenkamp, John E.; Sullivan, John J.
2011-08-01
The anterior refracting surface of the eye when wearing a contact lens is the thin fluid layer that forms on the surface of the contact lens. Under normal conditions, this fluid layer is less than 10 microns thick. The fluid layer thickness and topography change over time and are affected by the material properties of the contact lens, and may affect vision quality and comfort. An in vitro method of characterizing dynamic fluid layers applied to contact lenses mounted on mechanical substrates has been developed using a phase-shifting Twyman-Green interferometer. This interferometer continuously measures light reflected from the surface of the fluid layer, allowing precision analysis of the dynamic fluid layer. Movies showing this fluid layer behavior can be generated. The fluid behavior on the contact lens surface is measured, allowing quantitative analysis beyond what typical contact angle or visual inspection methods provide. The interferometer system has measured the formation and break up of fluid layers. Different fluid and contact lens material combinations have been used, and significant fluid layer properties have been observed in some cases. The interferometer is capable of identifying features in the fluid layer less than a micron in depth with a spatial resolution of about ten microns. An area on the contact lens approximately 6 mm wide can be measured with the system. This paper will discuss the interferometer design and analysis methods used. Measurement results of different material and fluid combinations are presented.
Tang, Z. B.; Deng, Y. D.; Su, C. Q.; Yuan, X. H.
2015-06-01
In this study, a numerical model has been employed to analyze the internal flow field distribution in a heat exchanger applied for an automotive thermoelectric generator based on computational fluid dynamics. The model simulates the influence of factors relevant to the heat exchanger, including the automotive waste heat mass flow velocity, temperature, internal fins, and back pressure. The result is in good agreement with experimental test data. Sensitivity analysis of the inlet parameters shows that increase of the exhaust velocity, compared with the inlet temperature, makes little contribution (0.1 versus 0.19) to the heat transfer but results in a detrimental back pressure increase (0.69 versus 0.21). A configuration equipped with internal fins is proved to offer better thermal performance compared with that without fins. Finally, based on an attempt to improve the internal flow field, a more rational structure is obtained, offering a more homogeneous temperature distribution, higher average heat transfer coefficient, and lower back pressure.
Huang, J.; Monteiro Santos, F. A.; Triantafilis, J.
2016-11-01
Characterization of the spatiotemporal distribution of soil volumetric water content (θ) is fundamental to agriculture, ecology, and earth science. Given the labor intensive and inefficient nature of determining θ, apparent electrical conductivity (ECa) measured by electromagnetic induction has been used as a proxy. A number of previous studies have employed inversion algorithms to convert ECa data to depth-specific electrical conductivity (σ) which could then be correlated to soil θ and other soil properties. The purpose of this study was to develop a spatiotemporal inversion algorithm which accounts for the temporal continuity of ECa. The algorithm was applied to a case study where time-lapse ECa was collected on a 350 m transect on seven different days on an alfalfa farm in the USA. Results showed that the approach was able to map the location of moving wetting front along the transect. Results also showed that the spatiotemporal inversion algorithm was more precise (RMSE = 0.0457 cm3/cm3) and less biased (ME = -0.0023 cm3/cm3) as compared with the nonspatiotemporal inversion approach (0.0483 cm3/cm3 and ME = -0.0030 cm3/cm3, respectively). In addition, the spatiotemporal inversion algorithm allows for a reduced set of ECa surveys to be used when non abrupt changes of soil water content occur with time. To apply this spatiotemporal inversion algorithm beyond low induction number condition, full solution of the EM induction phenomena can be studied in the future.
Zooplankton community dynamics in the N. Aegean front (E. Mediterranean in the winter spring period
Directory of Open Access Journals (Sweden)
I. SIOKOU
2015-01-01
Full Text Available Zooplankton community composition was studied in the North Aegean frontal area in the winter-spring period along a trophic gradient going from the less saline and cold modified Black Sea water to the high salinity and temperature waters of Levantine origin. Samples were collected at the upper 100 m of three stations positioned along this gradient by using three nets with different mesh sizes (45 μm, 200 μm and 500 μm. Τhe community composition (all sizes was differentiated along the gradient with smoother seasonal succession and higher diversity with increasing oligotrophy and salinity. The temporal variability of the community composition revealed significant changes in the January-April period as well as gradual decrease of diversity index values at the station positioned within the front. The major characteristic at this station was the abrupt increment and dominance of Centropages typicus in April, especially within the layer occupied by the modified Black Sea water. Significant difference in the community composition between March and April was a common feature in the whole study area and for all zooplankton fractions, though not of the same strength. The inflow of the Black Sea water and the trophic gradient were found to be important factors for the observed temporal variability and its spatial differentiation, while changes in the phytoplankton and protozoa abundance and community composition could account for the seasonal succession in species dominance.
A direct examination of the dynamics of dipolarization fronts using MMS
Yao, Z. H.; Rae, I. J.; Guo, R. L.; Fazakerley, A. N.; Owen, C. J.; Nakamura, R.; Baumjohann, W.; Watt, C. E. J.; Hwang, K. J.; Giles, B. L.; Russell, C. T.; Torbert, R. B.; Varsani, A.; Fu, H. S.; Shi, Q. Q.; Zhang, X.-J.
2017-04-01
Energy conversion on the dipolarization fronts (DFs) has attracted much research attention through the suggestion that intense current densities associated with DFs can modify the more global magnetotail current system. The current structures associated with a DF are at the scale of one to a few ion gyroradii, and their duration is comparable to a spacecraft's spin period. Hence, it is crucial to understand the physical mechanisms of DFs with measurements at a timescale shorter than a spin period. We present a case study whereby we use measurements from the Magnetospheric Multiscale (MMS) Mission, which provides full 3-D particle distributions with a cadence much shorter than a spin period. We provide a cross validation amongst the current density calculations and examine the assumptions that have been adopted in previous literature using the advantages of MMS mission (i.e., small-scale tetrahedron and high temporal resolution). We also provide a cross validation on the terms in the generalized Ohm's law using these advantageous measurements. Our results clearly show that the majority of the currents on the DF are contributed by both ion and electron diamagnetic drifts. Our analysis also implies that the ion frozen-in condition does not hold on the DF, while electron frozen-in condition likely holds. The new experimental capabilities allow us to accurately calculate Joule heating within the DF, which shows that plasma energy is being converted to magnetic energy in our event.
CAB Furnace Atmosphere Visualisation Using Computational Fluid Dynamics
Institute of Scientific and Technical Information of China (English)
P F Stratton; A P Richardson
2004-01-01
In today's automotive industry almost all car and truck radiators, oil coolers and air conditioning heat exchangers are manufactured using Nocolok Controlled Atmosphere Brazing (CAB). One of the most critical elements of the brazing process is the atmosphere used to protect the flux. Oxygen content is the major variable affecting the performance of the nitrogen atmosphere. Furnace design and flow rate are the major factors affecting oxygen content. Optimisation of these atmosphere parameters has a significant impact on operating cost, and on the quality and consistency of the brazed product.Computational fluid dynamics provides a tool to visualise the atmosphere conditions within the furnace and to explore the effects of changing some of the variables. Modelling the atmosphere in a typical CAB furnace has shown the importance of the integrity of the curtains in maintaining the low oxygen levels required for successful Nocolok brazing. For a given set of curtains it has shown that the only effective way of decreasing oxygen levels is to increase atmosphere gas flow.
CAB Furnace Atmosphere Visualisation Using Computational Fluid Dynamics
Institute of Scientific and Technical Information of China (English)
PFStratton; APRichardson
2004-01-01
In today's automotive industry almost all car and truck radiators, oil coolers and air conditioning heat exchangers are manufactured using Nocolok Controlled Atmosphere Brazing (CAB). One of the most critical elements of the brazing process is the atmosphere used to protect the flux. Oxygen content is the major variable affecting the performance of the nitrogen atmosphere. Furnace design and flow rate are the major factors affecting oxygen content. Optimisation of these atmosphere parameters has a significant impact on operating cost, and on the quality and consistency of the brazed product. Computational fluid dynamics provides a tool to visualise the atmosphere conditions within the furnace and to explore the effects of changing some of the variables. Modelling the atmosphere in a typical CAB furnace has shown the importance of the integrity of the curtains in maintaining the low oxygen levels required for successful Nocolok brazing. For a given set of curtains it has shown that the only effective way of decreasing oxygen levels is to increase atmosphere gas flow.
Fluid Dynamics of Competitive Swimming: A Computational Study
Mittal, Rajat; Loebbeck, Alfred; Singh, Hersh; Mark, Russell; Wei, Timothy
2004-11-01
The dolphin kick is an important component in competitive swimming and is used extensively by swimmers immediately following the starting dive as well as after turns. In this stroke, the swimmer swims about three feet under the water surface and the stroke is executed by performing an undulating wave-like motion of the body that is quite similar to the anguilliform propulsion mode in fish. Despite the relatively simple kinematics of this stoke, considerable variability in style and performance is observed even among Olympic level swimmers. Motivated by this, a joint experimental-numerical study has been initiated to examine the fluid-dynamics of this stroke. The current presentation will describe the computational portion of this study. The computations employ a sharp interface immersed boundary method (IBM) which allows us to simulate flows with complex moving boudnaries on stationary Cartesian grids. 3D body scans of male and female Olympic swimmers have been obtained and these are used in conjuction with high speed videos to recreate a realistic dolphin kick for the IBM solver. Preliminary results from these computations will be presented.
Computational Fluid Dynamics Analysis of Flexible Duct Junction Box Design
Energy Technology Data Exchange (ETDEWEB)
Beach, R.; Prahl, D.; Lange, R.
2013-12-01
IBACOS explored the relationships between pressure and physical configurations of flexible duct junction boxes by using computational fluid dynamics (CFD) simulations to predict individual box parameters and total system pressure, thereby ensuring improved HVAC performance. Current Air Conditioning Contractors of America (ACCA) guidance (Group 11, Appendix 3, ACCA Manual D, Rutkowski 2009) allows for unconstrained variation in the number of takeoffs, box sizes, and takeoff locations. The only variables currently used in selecting an equivalent length (EL) are velocity of air in the duct and friction rate, given the first takeoff is located at least twice its diameter away from the inlet. This condition does not account for other factors impacting pressure loss across these types of fittings. For each simulation, the IBACOS team converted pressure loss within a box to an EL to compare variation in ACCA Manual D guidance to the simulated variation. IBACOS chose cases to represent flows reasonably correlating to flows typically encountered in the field and analyzed differences in total pressure due to increases in number and location of takeoffs, box dimensions, and velocity of air, and whether an entrance fitting is included. The team also calculated additional balancing losses for all cases due to discrepancies between intended outlet flows and natural flow splits created by the fitting. In certain asymmetrical cases, the balancing losses were significantly higher than symmetrical cases where the natural splits were close to the targets. Thus, IBACOS has shown additional design constraints that can ensure better system performance.
Numerical simulation of landfill aeration using computational fluid dynamics.
Fytanidis, Dimitrios K; Voudrias, Evangelos A
2014-04-01
The present study is an application of Computational Fluid Dynamics (CFD) to the numerical simulation of landfill aeration systems. Specifically, the CFD algorithms provided by the commercial solver ANSYS Fluent 14.0, combined with an in-house source code developed to modify the main solver, were used. The unsaturated multiphase flow of air and liquid phases and the biochemical processes for aerobic biodegradation of the organic fraction of municipal solid waste were simulated taking into consideration their temporal and spatial evolution, as well as complex effects, such as oxygen mass transfer across phases, unsaturated flow effects (capillary suction and unsaturated hydraulic conductivity), temperature variations due to biochemical processes and environmental correction factors for the applied kinetics (Monod and 1st order kinetics). The developed model results were compared with literature experimental data. Also, pilot scale simulations and sensitivity analysis were implemented. Moreover, simulation results of a hypothetical single aeration well were shown, while its zone of influence was estimated using both the pressure and oxygen distribution. Finally, a case study was simulated for a hypothetical landfill aeration system. Both a static (steadily positive or negative relative pressure with time) and a hybrid (following a square wave pattern of positive and negative values of relative pressure with time) scenarios for the aeration wells were examined. The results showed that the present model is capable of simulating landfill aeration and the obtained results were in good agreement with corresponding previous experimental and numerical investigations.
Development of new flux splitting schemes. [computational fluid dynamics algorithms
Liou, Meng-Sing; Steffen, Christopher J., Jr.
1992-01-01
Maximizing both accuracy and efficiency has been the primary objective in designing a numerical algorithm for computational fluid dynamics (CFD). This is especially important for solutions of complex three dimensional systems of Navier-Stokes equations which often include turbulence modeling and chemistry effects. Recently, upwind schemes have been well received for their capability in resolving discontinuities. With this in mind, presented are two new flux splitting techniques for upwind differencing. The first method is based on High-Order Polynomial Expansions (HOPE) of the mass flux vector. The second new flux splitting is based on the Advection Upwind Splitting Method (AUSM). The calculation of the hypersonic conical flow demonstrates the accuracy of the splitting in resolving the flow in the presence of strong gradients. A second series of tests involving the two dimensional inviscid flow over a NACA 0012 airfoil demonstrates the ability of the AUSM to resolve the shock discontinuity at transonic speed. A third case calculates a series of supersonic flows over a circular cylinder. Finally, the fourth case deals with tests of a two dimensional shock wave/boundary layer interaction.
Shape Optimization of Vehicle Radiator Using Computational Fluid Dynamics (cfd)
Maddipatla, Sridhar; Guessous, Laila
2002-11-01
Automotive manufacturers need to improve the efficiency and lifetime of all engine components. In the case of radiators, performance depends significantly on coolant flow homogeneity across the tubes and overall pressure drop between the inlet and outlet. Design improvements are especially needed in tube-flow uniformity to prevent premature fouling and failure of heat exchangers. Rather than relying on ad-hoc geometry changes, the current study combines Computational Fluid Dynamics with shape optimization methods to improve radiator performance. The goal is to develop an automated suite of virtual tools to assist in radiator design. Two objective functions are considered: a flow non-uniformity coefficient,Cf, and the overall pressure drop, dP*. The methodology used to automate the CFD and shape optimization procedures is discussed. In the first phase, single and multi-variable optimization methods, coupled with CFD, are applied to simplified 2-D radiator models to investigate effects of inlet and outlet positions on the above functions. The second phase concentrates on CFD simulations of a simplified 3-D radiator model. The results, which show possible improvements in both pressure and flow uniformity, validate the optimization criteria that were developed, as well as the potential of shape optimization methods with CFD to improve heat exchanger design. * Improving Radiator Design Through Shape Optimization, L. Guessous and S. Maddipatla, Paper # IMECE2002-33888, Proceedings of the 2002 ASME International Mechanical Engineering Congress and Exposition, November 2002
Experimental methodology for computational fluid dynamics code validation
Energy Technology Data Exchange (ETDEWEB)
Aeschliman, D.P.; Oberkampf, W.L.
1997-09-01
Validation of Computational Fluid Dynamics (CFD) codes is an essential element of the code development process. Typically, CFD code validation is accomplished through comparison of computed results to previously published experimental data that were obtained for some other purpose, unrelated to code validation. As a result, it is a near certainty that not all of the information required by the code, particularly the boundary conditions, will be available. The common approach is therefore unsatisfactory, and a different method is required. This paper describes a methodology developed specifically for experimental validation of CFD codes. The methodology requires teamwork and cooperation between code developers and experimentalists throughout the validation process, and takes advantage of certain synergisms between CFD and experiment. The methodology employs a novel uncertainty analysis technique which helps to define the experimental plan for code validation wind tunnel experiments, and to distinguish between and quantify various types of experimental error. The methodology is demonstrated with an example of surface pressure measurements over a model of varying geometrical complexity in laminar, hypersonic, near perfect gas, 3-dimensional flow.
Model Order Reduction for Fluid Dynamics with Moving Solid Boundary
Gao, Haotian; Wei, Mingjun
2016-11-01
We extended the application of POD-Galerkin projection for model order reduction from usual fixed-domain problems to more general fluid-solid systems when moving boundary/interface is involved. The idea is similar to numerical simulation approaches using embedded forcing terms to represent boundary motion and domain change. However, such a modified approach will not get away with the unsteadiness of boundary terms which appear as time-dependent coefficients in the new Galerkin model. These coefficients need to be pre-computed for prescribed motion, or worse, to be computed at each time step for non-prescribed motion. The extra computational cost gets expensive in some cases and eventually undermines the value of using reduced-order models. One solution is to decompose the moving boundary/domain to orthogonal modes and derive another low-order model with fixed coefficients for boundary motion. Further study shows that the most expensive integrations resulted from the unsteady motion (in both original and domain-decomposition approaches) have almost negligible impact on the overall dynamics. Dropping these expensive terms reduces the computation cost by at least one order while no obvious effect on model accuracy is noticed. Supported by ARL.
Computational analysis of fluid dynamics in pharmaceutical freeze-drying.
Alexeenko, Alina A; Ganguly, Arnab; Nail, Steven L
2009-09-01
Analysis of water vapor flows encountered in pharmaceutical freeze-drying systems, laboratory-scale and industrial, is presented based on the computational fluid dynamics (CFD) techniques. The flows under continuum gas conditions are analyzed using the solution of the Navier-Stokes equations whereas the rarefied flow solutions are obtained by the direct simulation Monte Carlo (DSMC) method for the Boltzmann equation. Examples of application of CFD techniques to laboratory-scale and industrial scale freeze-drying processes are discussed with an emphasis on the utility of CFD for improvement of design and experimental characterization of pharmaceutical freeze-drying hardware and processes. The current article presents a two-dimensional simulation of a laboratory scale dryer with an emphasis on the importance of drying conditions and hardware design on process control and a three-dimensional simulation of an industrial dryer containing a comparison of the obtained results with analytical viscous flow solutions. It was found that the presence of clean in place (CIP)/sterilize in place (SIP) piping in the duct lead to significant changes in the flow field characteristics. The simulation results for vapor flow rates in an industrial freeze-dryer have been compared to tunable diode laser absorption spectroscopy (TDLAS) and gravimetric measurements.
Computational fluid dynamics for turbomachinery internal air systems.
Chew, John W; Hills, Nicholas J
2007-10-15
Considerable progress in development and application of computational fluid dynamics (CFD) for aeroengine internal flow systems has been made in recent years. CFD is regularly used in industry for assessment of air systems, and the performance of CFD for basic axisymmetric rotor/rotor and stator/rotor disc cavities with radial throughflow is largely understood and documented. Incorporation of three-dimensional geometrical features and calculation of unsteady flows are becoming commonplace. Automation of CFD, coupling with thermal models of the solid components, and extension of CFD models to include both air system and main gas path flows are current areas of development. CFD is also being used as a research tool to investigate a number of flow phenomena that are not yet fully understood. These include buoyancy-affected flows in rotating cavities, rim seal flows and mixed air/oil flows. Large eddy simulation has shown considerable promise for the buoyancy-driven flows and its use for air system flows is expected to expand in the future.
Methodology for computational fluid dynamics code verification/validation
Energy Technology Data Exchange (ETDEWEB)
Oberkampf, W.L.; Blottner, F.G.; Aeschliman, D.P.
1995-07-01
The issues of verification, calibration, and validation of computational fluid dynamics (CFD) codes has been receiving increasing levels of attention in the research literature and in engineering technology. Both CFD researchers and users of CFD codes are asking more critical and detailed questions concerning the accuracy, range of applicability, reliability and robustness of CFD codes and their predictions. This is a welcomed trend because it demonstrates that CFD is maturing from a research tool to the world of impacting engineering hardware and system design. In this environment, the broad issue of code quality assurance becomes paramount. However, the philosophy and methodology of building confidence in CFD code predictions has proven to be more difficult than many expected. A wide variety of physical modeling errors and discretization errors are discussed. Here, discretization errors refer to all errors caused by conversion of the original partial differential equations to algebraic equations, and their solution. Boundary conditions for both the partial differential equations and the discretized equations will be discussed. Contrasts are drawn between the assumptions and actual use of numerical method consistency and stability. Comments are also made concerning the existence and uniqueness of solutions for both the partial differential equations and the discrete equations. Various techniques are suggested for the detection and estimation of errors caused by physical modeling and discretization of the partial differential equations.
Computational fluid dynamics challenges for hybrid air vehicle applications
Carrin, M.; Biava, M.; Steijl, R.; Barakos, G. N.; Stewart, D.
2017-06-01
This paper begins by comparing turbulence models for the prediction of hybrid air vehicle (HAV) flows. A 6 : 1 prolate spheroid is employed for validation of the computational fluid dynamics (CFD) method. An analysis of turbulent quantities is presented and the Shear Stress Transport (SST) k-ω model is compared against a k-ω Explicit Algebraic Stress model (EASM) within the unsteady Reynolds-Averaged Navier-Stokes (RANS) framework. Further comparisons involve Scale Adaptative Simulation models and a local transition transport model. The results show that the flow around the vehicle at low pitch angles is sensitive to transition effects. At high pitch angles, the vortices generated on the suction side provide substantial lift augmentation and are better resolved by EASMs. The validated CFD method is employed for the flow around a shape similar to the Airlander aircraft of Hybrid Air Vehicles Ltd. The sensitivity of the transition location to the Reynolds number is demonstrated and the role of each vehicle£s component is analyzed. It was found that the ¦ns contributed the most to increase the lift and drag.
Introducing Computational Fluid Dynamics Simulation into Olfactory Display
Ishida, Hiroshi; Yoshida, Hitoshi; Nakamoto, Takamichi
An olfactory display is a device that delivers various odors to the user's nose. It can be used to add special effects to movies and games by releasing odors relevant to the scenes shown on the screen. In order to provide high-presence olfactory stimuli to the users, the display must be able to generate realistic odors with appropriate concentrations in a timely manner together with visual and audio playbacks. In this paper, we propose to use computational fluid dynamics (CFD) simulations in conjunction with the olfactory display. Odor molecules released from their source are transported mainly by turbulent flow, and their behavior can be extremely complicated even in a simple indoor environment. In the proposed system, a CFD solver is employed to calculate the airflow field and the odor dispersal in the given environment. An odor blender is used to generate the odor with the concentration determined based on the calculated odor distribution. Experimental results on presenting odor stimuli synchronously with movie clips show the effectiveness of the proposed system.
The role of computational fluid dynamics (CFD) in hair science.
Spicka, Peter; Grald, Eric
2004-01-01
The use of computational fluid dynamics (CFD) as a virtual prototyping tool is widespread in the consumer packaged goods industry. CFD refers to the calculation on a computer of the velocity, pressure, and temperature and chemical species concentrations within a flowing liquid or gas. Because the performance of manufacturing equipment and product designs can be simulated on the computer, the benefit of using CFD is significant time and cost savings when compared to traditional physical testing methods. CFD has been used to design, scale-up and troubleshoot mixing tanks, spray dryers, heat exchangers and other process equipment. Recently, computer models of the capillary wicking process inside fibrous structures have been added to CFD software. These models have been used to gain a better understanding of the absorbent performance of diapers and feminine protection products. The same models can also be used to represent the movement of shampoo, conditioner, colorants and other products through the hair and scalp. In this paper, we provide an introduction to CFD and show some examples of its application to the manufacture of consumer products. We also provide sonic examples to show the potential of CFD for understanding the performance of products applied to the hair and scalp.
Design of airborne wind turbine and computational fluid dynamics analysis
Anbreen, Faiqa
Wind energy is a promising alternative to the depleting non-renewable sources. The height of the wind turbines becomes a constraint to their efficiency. Airborne wind turbine can reach much higher altitudes and produce higher power due to high wind velocity and energy density. The focus of this thesis is to design a shrouded airborne wind turbine, capable to generate 70 kW to propel a leisure boat with a capacity of 8-10 passengers. The idea of designing an airborne turbine is to take the advantage of higher velocities in the atmosphere. The Solidworks model has been analyzed numerically using Computational Fluid Dynamics (CFD) software StarCCM+. The Unsteady Reynolds Averaged Navier Stokes Simulation (URANS) with K-epsilon turbulence model has been selected, to study the physical properties of the flow, with emphasis on the performance of the turbine and the increase in air velocity at the throat. The analysis has been done using two ambient velocities of 12 m/s and 6 m/s. At 12 m/s inlet velocity, the velocity of air at the turbine has been recorded as 16 m/s. The power generated by the turbine is 61 kW. At inlet velocity of 6 m/s, the velocity of air at turbine increased to 10 m/s. The power generated by turbine is 25 kW.
Dynamic oxygen-enhanced MRI of cerebrospinal fluid.
Directory of Open Access Journals (Sweden)
Taha M Mehemed
Full Text Available Oxygen causes an increase in the longitudinal relaxation rate of tissues through its T1-shortening effect owing to its paramagnetic properties. Due to such effects, MRI has been used to study oxygen-related signal intensity changes in various body parts including cerebrospinal fluid (CSF space. Oxygen enhancement of CSF has been mainly studied using MRI sequences with relatively longer time resolution such as FLAIR, and T1 value calculation. In this study, fifteen healthy volunteers were scanned using fast advanced spin echo MRI sequence with and without inversion recovery pulse in order to dynamically track oxygen enhancement of CSF. We also focused on the differences of oxygen enhancement at sulcal and ventricular CSF. Our results revealed that CSF signal after administration of oxygen shows rapid signal increase in both sulcal CSF and ventricular CSF on both sequences, with statistically significant predominant increase in sulcal CSF compared with ventricular CSF. CSF is traditionally thought to mainly form from the choroid plexus in the ventricles and is absorbed at the arachnoid villi, however, it is also believed that cerebral arterioles contribute to the production and absorption of CSF, and controversy remains in terms of the precise mechanism. Our results demonstrated rapid oxygen enhancement in sulcal CSF, which may suggest inhaled oxygen may diffuse into sulcal CSF space rapidly probably due to the abundance of pial arterioles on the brain sulci.
Weingart, Robert
This thesis is about the validation of a computational fluid dynamics simulation of a ground vehicle by means of a low-budget coast-down test. The vehicle is built to the standards of the 2014 Formula SAE rules. It is equipped with large wings in the front and rear of the car; the vertical loads on the tires are measured by specifically calibrated shock potentiometers. The coast-down test was performed on a runway of a local airport and is used to determine vehicle specific coefficients such as drag, downforce, aerodynamic balance, and rolling resistance for different aerodynamic setups. The test results are then compared to the respective simulated results. The drag deviates about 5% from the simulated to the measured results. The downforce numbers show a deviation up to 18% respectively. Moreover, a sensitivity analysis of inlet velocities, ride heights, and pitch angles was performed with the help of the computational simulation.
Gyergyek, T.; Kovačič, J.
2016-06-01
Plasma-wall transition is studied by a one-dimensional steady state two-fluid model. Continuity and momentum exchange equations are used for the electrons, while the continuity, momentum exchange, and energy transport equation are used for the ions. Electrons are assumed to be isothermal. The closure of ion equations is made by the assumption that the heat flux is zero. The model equations are solved for potential, ion and electron density, and velocity and ion temperature as independent variables. The model includes coulomb collisions between ions and electrons and charge exchange collisions between ions and neutral atoms of the same species and same mass. The neutral atoms are assumed to be essentially at rest. The model is solved for finite ratio ɛ = /λ D L between the Debye length and λD and ionization length L in the pre-sheath and in the sheath at the same time. Charge exchange collisions heat the ions in the sheath and the pre-sheath. Even a small increase of the frequency of charge exchange collisions causes a substantial increase of ion temperature. Coulomb collisions have negligible effect on ion temperature in the pre-sheath, while in the sheath they cause a small cooling of ions. The increase of ɛ causes the increase of ion temperature. From the ion density and temperature profiles, the polytropic function κ is calculated according to its definition given by Kuhn et al. [Phys. Plasmas 13, 013503 (2006)]. The obtained profiles of κ indicate that the ion flow is isothermal only in a relatively narrow region in the pre-sheath, while close to the sheath edge and in the sheath it is closer to adiabatic. The ion sound velocity is space dependent and exhibits a maximum. This maximum indicates the location of the sheath edge only in the limit ɛ → 0 .
Connor, C. L.; Fatland, D. R.; Heavner, M.; Korzen, N.; Galbraith, J.; Sauer, D.; Hood, E. W.
2009-12-01
Extrapolation of 2000-2009 GPS results from terminus position surveys of the Mendenhall Glacier near Juneau, Alaska suggests that the lake front glacier terminus will no longer be in contact with proglacial Mendenhall Lake by July 2011. Meteorologic stations located near the glacier terminus at 44m asl, on the glacier surface at 430m (Northstar Camp), and at 1569m near the Mendenhall-Taku Glacier ice divide, provide data from rainfall events and temperature variation which contribute to glacier velocity and ultimately ice mass transfer to the lower glacier. Mendenhall weather data in combination with wind direction, wind velocity, and lake water temperature profiles (0-40m) and bathymetric surveys in 2009 provide detailed information about the physical conditions of the glacier and lake which are also captured visually by hourly and 30 second image records of the glacier terminus. Cameras are located at 500m from the terminus on bedrock and at ~2km from the terminus at the USFS Mendenhall Glacier Visitor Center roof. Ice berg motions and their changing positions in Mendenhall Lake can be used to create a gyre model for lake circulation. Summer 2009 lake water column temperature profiles collected at 15 minute intervals can also be linked with met station data, and USGS discharge data for the Mendenhall River to identify subglacial meltwater discharge events into the lake. We present here a synthetic view of these sensor data to evaluate what can be inferred and what remains mysterious concerning Mendenhall Glacier recession. Webcam photo Mendenhall Glacier Terminus 01-Sept-2009 10:02 am http://seamonster.jun.alaska.edu/webcam/Mendterm
Drainage network over the migrating front of dynamic uplift in Patagonia
Jeandet, Louise; Robert, Xavier; Audin, Laurence; Husson, Laurent; Guillaume, Benjamin
2016-04-01
Dynamic topography disturbs the regional morphology at long wavelength and with very low topographic gradients. Nevertheless, fluvial erosion and the drainage pattern should respond to the spatial and temporal topographic variations. In Patagonia, the mid-Miocene, opening and northward migration of an asthenospheric window beneath the South American plate triggered a northward propagating wave of dynamic topography. Based on a morphometric analysis, we explore the long-wavelength response of the drainage system to the recent dynamics of the continental lithosphere. Our analysis of Patagonian rivers (stream profile analysis) and basins (R/Sr analysis) shows a transient state of the drainage network responding to a likely recent signal that prevails at the latitudes of the Chile Triple Junction in Argentina. Moreover, the distribution of the perturbation signal among the drainage network shows a South-to-North gradient, with the low Strahler order tributaries more affected with increasing latitudes. We interpret this observation as the differential timing of response to a Northward propagating signal of dynamic topography. We further use the geometry of the drainage network combined to numerical model predictions to infer the characteristic response time of the surface processes. While the main tributaries respond within ~1-3 Ma, the lower order remain disturbed for longer times. This observation is further supported by the persistently high mean elevation where incision is high, which we take as indicative of the fact that erosion has not yet thoroughly achieved its resurfacing action.
Directory of Open Access Journals (Sweden)
Wei Liu
2013-01-01
Full Text Available This paper takes the electric off-road vehicle with separated driven axles as the research object. To solve the longitudinal dynamics driving control problems, vehicle dynamics model, and control strategies were studied and the corresponding simulation was carried out. An 8-DOF vehicle dynamics model with separated driven axles was built. The driving control strategies on the typical roads were put forward. The recognition algorithm of the typical road surfaces based on the wheels’ slip rates was proposed. And the two control systems were designed including the pedal opening degree adjustment control system based on PI algorithm and the interaxle torque distribution control system based on sliding mode control algorithm. The driving control flow of the proposed vehicle combining the pedal adjustment control system with the interaxle torque distribution control system was developed. And the driven control strategies for the typical roads were simulated. Simulation results show that the proposed drive control strategies can adapt to different typical road surfaces, limit the slip rates of the driving wheels within the stable zone, and ensure the vehicle driving safely and stably in accordance with the driver's intention.
Cerebrospinal fluid dynamics in Chiari malformation associated with syringomyelia
Institute of Scientific and Technical Information of China (English)
LIU Bin; WANG Zhen-yu; XIE Jing-cheng; HAN Hong-bin; PEI Xin-long
2007-01-01
Background About 50%-70% of patients with Chiari malformation I (CMI) presented with syringomyelia (SM), which is supposed to be related to abnormal cerebrospinal fluid (CSF) flow around the foramen magnum. The aim of this study was to investigate the cerebrospinal fluid dynamics at levels of the aqueduct and upper cervical spine in patients with CMI associated with SM, and to discuss the possible mechanism of formation of SM.Methods From January to April 2004, we examined 10 adult patients with symptomatic CMI associated with SM and 10 healthy volunteers by phase-contrast MRI. CSF flow patterns were evaluated at seven regions of interest (ROI): the aqueduct and ventral and dorsal subarachnoid spaces of the spine at levels of the cerebellar tonsil, C2-3, and C5-6. The CSF flow waveforms were analyzed by measuring CSF circulation time, durations and maximum velocities of cranial- and caudal-directed flows, and the ratio between the two maximum velocities. Data were analyzed by ttest using SPSS 11.5.Results We found no definite communication between the fourth ventricle and syringomyelia by MRI in the 10 patients.In both the groups, we observed cranial-directed flow of CSF in the early cardiac systolic phase, which changed the direction from cranial to caudal from the middle systolic phase to the early diastolic phase, and then turned back in cranial direction in the late diastolic phase. The CSF flow disappeared at the dorsal ROI at the level of C2-3 in 3 patients and 1 volunteer, and at the level of C5-6 in 6 patients and 3 volunteers. The durations of CSF circulation at all the ROIs were significantly shorter in the patients than those in the healthy volunteers (P=0.014 at the midbrain aqueduct, P=0.019 at the inferior margin of the cerebellar tonsil, P=0.014 at the level of C2-3, and P=0.022 at the level of C5-6). No significant difference existed between the two groups in the initial point and duration of the caudal-directed CSF flow during a cardiac cycle at
Sen, Seema; Lake, Markus; Kroppen, Norman; Farber, Peter; Wilden, Johannes; Schaaf, Peter
2017-02-01
This study describes the self-propagating exothermic reaction in Ti/Al reactive multilayer foils by using experiments and computational fluid dynamics simulation. The Ti/Al foils with different molar ratios of 1Ti/1Al, 1Ti/2Al and 1Ti/3Al were fabricated by magnetron sputtering method. Microstructural characteristics of the unreacted and reacted foils were analyzed by using electronic and atomic force microscopes. After an electrical ignition, the influence of ignition potentials on reaction propagation has been experimentally investigated. The reaction front propagates with a velocity of minimum 0.68 ± 0.4 m/s and maximum 2.57 ± 0.6 m/s depending on the input ignition potentials and the chemical compositions. Here, the 1Ti/3Al reactive foil exhibits both steady state and unsteady wavelike reaction propagation. Moreover, the numerical computational fluid dynamics (CFD) simulation shows the time dependent temperature flow and atomic mixing in a nanoscale reaction zone. The CFD simulation also indicates the potentiality for simulating exothermic reaction in the nanoscale Ti/Al foil.
Applications of laser based measurements to combustion related fluid dynamics
Energy Technology Data Exchange (ETDEWEB)
Klingmann, J.
1998-12-01
This thesis is concerned with laser based techniques for the measurement of fluid dynamical properties and their application to combusting flow fields or flow fields related to combustion. As an introduction, the theory of turbulent flow and combustion is shortly presented. An overview of laser based measuring techniques is given. Next, seven papers are included. The main topic of papers 1 and 2 is the measurements of swirling pipe flows with sudden axi-symmetric expansions. These flow fields are related to the flow fields of gas turbine combustors. Measurements and computations using commercial software are compared. Papers 3 and 7 deal with a laser Doppler anemometry based method for the measurement of the turbulent dissipation rate and its application to an axi-symmetric free jet, respectively. The measurements rely on two-point measurements with high spatial resolution. Also three-component one-point measurements are used to obtain the triple velocity correlations. Together these measurements are sufficient to present the energy balance, if pressure effects are neglected. Papers 4, 5 and 6 are concerned with the turbulent flame speed under premixed conditions. Papers 4 and 5 present flame speed measurements from a stationary burner using methane and Danish natural gas. Particle image velocimetry and one- and two-point Laser Doppler anemometry is used to measure flame speed and turbulent quantities, including integral length scales. Paper 7 presents measurements of flame speed and turbulence parameters in a spark ignition engine. Here heat release analyses from pressure measurements are combined with one- and two-point laser Doppler anemometry to analyze influence of turbulence on flame propagation 50 refs, 25 figs
PIV Application to Fluid Dynamics of Bass Reflex Ports
Rossi, Massimiliano; Esposito, Enrico; Tomasini, Enrico Primo
A bass reflex (or vented or ported) loudspeaker system (BRS) is a particular type of loudspeaker enclosure that makes use of the combination of two second-order mechanic/acoustic devices, i.e., the driver and a Helmotz resonator, in order to create a new system with reinforced emission in the low frequency region. The resonator is composed by the box itself in which one or more ports are present with suitable shapes and dimensions. This category of loudspeaker presents several advantages compared to closed-box systems such as higher efficiency and power, smaller dimensions and reduced distortion at lower frequencies. Notwithstanding these advantages, they present some drawbacks like more complexity and unloading of the cone below the tuning frequency. Moreover, at high power levels the airflow in the port(s) may generate unwanted noises due to turbulence as well as distortion and acoustic compression. In this work we will present and compare a series of experiments conducted on two different bass reflex ports designs to assess their performance in terms of flow turbulence and sound-level compression at high input power levels. These issues are quite important in professional sound systems, where increasing power levels and sound clarity require exponentially growing cost and weight. For these reasons it is vital to optimize port design. To the knowledge of the authors there does not exist an accurate, nonintrusive experimental full-field study of air flows emitting from reflex ports in operating conditions. In this work, the experimental fluid dynamic investigation has been conducted by means of PIV and LDA techniques.
Computational fluid dynamics modeling for emergency preparedness and response
Energy Technology Data Exchange (ETDEWEB)
Lee, R.L.; Albritton, J.R.; Ermak, D.L.; Kim, J.
1995-02-01
Computational fluid dynamics (CFD) has (CFD) has played an increasing in the improvement of atmospheric dispersion modeling. This is because many dispersion models are now driven by meteorological fields generated from CFD models or, in numerical weather prediction`s terminology, prognostic models. Whereas most dispersion models typically involve one or a few scalar, uncoupled equations, the prognostic equations are a set of highly-couple equations whose solution requires a significant level of computational power. Recent advances in computer hardware and software have enabled modestly-priced, high performance, workstations to exhibit the equivalent computation power of some mainframes. Thus desktop-class machines that were limited to performing dispersion calculations driven by diagnostic wind fields may now be used to calculate complex flows using prognostic CFD models. The Release and Advisory Capability (ARAC) program at Lawrence Livermore National Laboratory (LLNL) has, for the past several years, taken advantage of the improvements in hardware technology to develop a national emergency response capability based on executing diagnostic models on workstations. Diagnostic models that provide wind fields are, in general, simple to implement, robust and require minimal time for execution. Because these models typically contain little physics beyond mass-conservation, their performance is extremely sensitive to the quantity and quality of input meteorological data and, in spite of their utility, can be applied with confidence to only modestly complex flows. We are now embarking on a development program to incorporate prognostic models to generate, in real-time, the meteorological fields for the dispersion models. In contrast to diagnostic models, prognostic models are physically-based and are capable of incorporating many physical processes to treat highly complex flow scenarios.
Turbomachinery computational fluid dynamics: asymptotes and paradigm shifts.
Dawes, W N
2007-10-15
This paper reviews the development of computational fluid dynamics (CFD) specifically for turbomachinery simulations and with a particular focus on application to problems with complex geometry. The review is structured by considering this development as a series of paradigm shifts, followed by asymptotes. The original S1-S2 blade-blade-throughflow model is briefly described, followed by the development of two-dimensional then three-dimensional blade-blade analysis. This in turn evolved from inviscid to viscous analysis and then from steady to unsteady flow simulations. This development trajectory led over a surprisingly small number of years to an accepted approach-a 'CFD orthodoxy'. A very important current area of intense interest and activity in turbomachinery simulation is in accounting for real geometry effects, not just in the secondary air and turbine cooling systems but also associated with the primary path. The requirements here are threefold: capturing and representing these geometries in a computer model; making rapid design changes to these complex geometries; and managing the very large associated computational models on PC clusters. Accordingly, the challenges in the application of the current CFD orthodoxy to complex geometries are described in some detail. The main aim of this paper is to argue that the current CFD orthodoxy is on a new asymptote and is not in fact suited for application to complex geometries and that a paradigm shift must be sought. In particular, the new paradigm must be geometry centric and inherently parallel without serial bottlenecks. The main contribution of this paper is to describe such a potential paradigm shift, inspired by the animation industry, based on a fundamental shift in perspective from explicit to implicit geometry and then illustrate this with a number of applications to turbomachinery.
Imaging X-ray detector front-end with high dynamic range: IDeF-X HD
Energy Technology Data Exchange (ETDEWEB)
Gevin, O.; Lemaire, O.; Lugiez, F. [CEA, Irfu, Service d' Electronique, de Detecteurs et d' Informatique, Bat. 141, F-91191 Gif-sur-Yvette (France); Michalowska, A., E-mail: alicja.michalowska@cea.fr [CEA, Irfu, Service d' Electronique, de Detecteurs et d' Informatique, Bat. 141, F-91191 Gif-sur-Yvette (France); Baron, P. [CEA, Irfu, Service d' Electronique, de Detecteurs et d' Informatique, Bat. 141, F-91191 Gif-sur-Yvette (France); Limousin, O. [CEA, Irfu, Service d' Astrophysique, Bat. 709 Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Delagnes, E. [CEA, Irfu, Service d' Electronique, de Detecteurs et d' Informatique, Bat. 141, F-91191 Gif-sur-Yvette (France)
2012-12-11
Presented circuit, IDeF-X HD (Imaging Detector Front-end) is a member of the IDeF-X ASICs family for space applications. It has been optimized for a half millimeter pitch CdTe or CdZnTe pixelated detector arranged in 16 Multiplication-Sign 16 array. It is aimed to operate in the hard X-ray range from few keV up to 250 keV or more. The ASIC has been realized in AMS 0.35 {mu}m CMOS process. The IDeF-X HD is a 32 channel analog front-end with self-triggering capability. The architecture of the analog channel includes a chain of charge sensitive amplifier with continuous reset system and non-stationary noise suppressor, adjustable gain stage, pole-zero cancellation stage, adjustable shaping time low pass filter, baseline holder and peak detector with discriminator. The power consumption of the IDeF-X HD is 800 {mu}W per channel. With the in-channel variable gain stage the nominal 250 keV dynamic range of the ASIC can be extended up to 1 MeV anticipating future applications using thick sensors. Measuring the noise performance without a detector at the input with minimized leakage current (programmable) at the input, we achieved ENC of 33 electrons rms at 10.7 {mu}s peak time. Measurements with CdTe detector show good energy resolution FWHM of 1.1 keV at 60 keV and 4.3 keV at 662 keV with detection threshold below 4 keV. In addition, an absolute temperature sensor has been integrated with resolution of 1.5 Degree-Sign C.
Imaging X-ray detector front-end with high dynamic range: IDeF-X HD
Gevin, O.; Lemaire, O.; Lugiez, F.; Michalowska, A.; Baron, P.; Limousin, O.; Delagnes, E.
2012-12-01
Presented circuit, IDeF-X HD (Imaging Detector Front-end) is a member of the IDeF-X ASICs family for space applications. It has been optimized for a half millimeter pitch CdTe or CdZnTe pixelated detector arranged in 16×16 array. It is aimed to operate in the hard X-ray range from few keV up to 250 keV or more. The ASIC has been realized in AMS 0.35 μm CMOS process. The IDeF-X HD is a 32 channel analog front-end with self-triggering capability. The architecture of the analog channel includes a chain of charge sensitive amplifier with continuous reset system and non-stationary noise suppressor, adjustable gain stage, pole-zero cancellation stage, adjustable shaping time low pass filter, baseline holder and peak detector with discriminator. The power consumption of the IDeF-X HD is 800 μW per channel. With the in-channel variable gain stage the nominal 250 keV dynamic range of the ASIC can be extended up to 1 MeV anticipating future applications using thick sensors. Measuring the noise performance without a detector at the input with minimized leakage current (programmable) at the input, we achieved ENC of 33 electrons rms at 10.7 μs peak time. Measurements with CdTe detector show good energy resolution FWHM of 1.1 keV at 60 keV and 4.3 keV at 662 keV with detection threshold below 4 keV. In addition, an absolute temperature sensor has been integrated with resolution of 1.5 °C.
Morlighem, M.; Bondzio, J. H.; Seroussi, H. L.; Wood, M.; Rignot, E. J.
2016-12-01
Glacier-front dynamics is an important control on Greenland's ice mass balance. Warmer ocean waters trigger ice-front retreats of marine-terminating glaciers, and the corresponding loss in resistive stress leads to glacier acceleration and thinning. Here, we quantify the sensitivity and vulnerability of marine-terminating glaciers along the Northwest coast of Greenland (from 73°N to 7°N) to ocean-induced melt using the Ice Sheet System Model (ISSM) and bathymetry data collected by NASA's Occreans Melting Greenland (OMG). We first combine OMG bathymetry data with ice velocity from satellites and ice thickness from airborne radars using a mass conservation approach on land to produce ice thickness and bed elevation mapping across the ice-ocean boundary that are more precise and reliable than ever before. Using this new map, we then develop a plan-view model of this region that includes a level set based moving boundary capability, a parameterized ocean-induced melt and a calving law based on a Von Mises criterion. We find that some glaciers, such as Dietrichson Gletscher or Alison Gletscher, are sensitive to small increases in ocean-induced melt, while others, such as Steenstrup Gletscher or Qeqertarsuup Sermia, are very difficult to destabilize, even with a quadrupling of the melt. Under the most intense melt experiment of 12 m/day in the summer, we find that Hayes Gletscher retreats by more than 50 km inland into a deep trough and its velocity increases by a factor of 10 over only 15 years. The model suggests that ice-ocean interactions are the triggering mechanism of glacier retreat, but the bed controls its magnitude. This work was performed at the University of California Irvine under a contract with the National Aeronautics and Space Administration, Cryospheric Sciences Program, grant NNX15AD55G.
Global Dynamics of Shaft Lines Rotating in Surrounding Fluids Application to Thin Fluid Films
Directory of Open Access Journals (Sweden)
David Lornage
2004-01-01
a disc and a thin-walled shaft mounted on a hydrodynamic bearing. The second is intended for studying a more realistic structure composed of a shaft and a wheel coupled with a fluid film between the wheel and a casing. These applications make it possible to identify trends related to fluid effects and couplings between the flexible structural parts.
Kleis, Stanley J.; Truong, Tuan; Goodwin, Thomas J,
2004-01-01
This report is a documentation of a fluid dynamic analysis of the proposed Automated Static Culture System (ASCS) cell module mixing protocol. The report consists of a review of some basic fluid dynamics principles appropriate for the mixing of a patch of high oxygen content media into the surrounding media which is initially depleted of oxygen, followed by a computational fluid dynamics (CFD) study of this process for the proposed protocol over a range of the governing parameters. The time histories of oxygen concentration distributions and mechanical shear levels generated are used to characterize the mixing process for different parameter values.
Fluid dynamic constraints on resource acquisition in small pelagic organisms
DEFF Research Database (Denmark)
Kiørboe, Thomas
2016-01-01
by the application of formal fluid physics. Here, I examine resource acquisition mechanisms in small aquatic organisms, ranging from uptake of dissolved molecules to feeding on suspended particulate prey, and examine how organism behaviors and morphologies may be shaped by the often non-intuitive small-scale fluid...
Poster on MPI application in Computational Fluid Dynamics
Argentini, Gianluca
2003-01-01
Poster-presentation of the paper "Message Passing Fluids: molecules as processes in parallel computational fluids" held at "EURO PVMMPI 2003" Congress; the paper is on the proceedings "Recent Advances in Parallel Virtual Machine and Message Passing Interface", 10th European PVM/MPI User's Group Meeting, LNCS 2840, Springer-Verlag, Dongarra-Laforenza-Orlando editors, pp. 550-554.
On Subextensive Corrections to Fluid Dynamics from Gravity
Lópes-Cardoso, G; Grass, V
2010-01-01
We use the fluid-gravity correspondence to compute subextensive corrections, proportional to the shear tensor, to the energy-momentum tensor of fluids on three-spheres. The dual configurations we consider are charged black hole solutions of N = 2 gauged supergravity theories in five dimensions.
Modeling of Dynamic Fluid Forces in Fast Switching Valves
DEFF Research Database (Denmark)
Roemer, Daniel Beck; Johansen, Per; Pedersen, Henrik Clemmensen;
2015-01-01
force, but these models are computationally expensive and are not suitable for evaluating large numbers of different operation conditions or even design optimization. In the present paper, an effort is done to describe these fluid forces and their origin. An example of the total opposing fluid force...
Energy Technology Data Exchange (ETDEWEB)
Marc Cremer; Kirsi St. Marie; Dave Wang
2003-04-30
This is the first Semiannual Technical Report for DOE Cooperative Agreement No: DE-FC26-02NT41580. The goal of this project is to systematically assess the sensitivity of furnace operational conditions to burner air and fuel flows in coal fired utility boilers. Our approach is to utilize existing baseline furnace models that have been constructed using Reaction Engineering International's (REI) computational fluid dynamics (CFD) software. Using CFD analyses provides the ability to carry out a carefully controlled virtual experiment to characterize the sensitivity of NOx emissions, unburned carbon (UBC), furnace exit CO (FECO), furnace exit temperature (FEGT), and waterwall deposition to burner flow controls. The Electric Power Research Institute (EPRI) is providing co-funding for this program, and instrument and controls experts from EPRI's Instrument and Controls (I&C) Center are active participants in this project. This program contains multiple tasks and good progress is being made on all fronts. A project kickoff meeting was held in conjunction with NETL's 2002 Sensors and Control Program Portfolio Review and Roadmapping Workshop, in Pittsburgh, PA during October 15-16, 2002. Dr. Marc Cremer, REI, and Dr. Paul Wolff, EPRI I&C, both attended and met with the project COR, Susan Maley. Following the review of REI's database of wall-fired coal units, the project team selected a front wall fired 150 MW unit with a Riley Low NOx firing system including overfire air for evaluation. In addition, a test matrix outlining approximately 25 simulations involving variations in burner secondary air flows, and coal and primary air flows was constructed. During the reporting period, twenty-two simulations have been completed, summarized, and tabulated for sensitivity analysis. Based on these results, the team is developing a suitable approach for quantifying the sensitivity coefficients associated with the parametric tests. Some of the results of the CFD
Dynamic Simulation and Analysis of Vehicle Macpherson Front Suspension System%汽车麦弗逊前悬架动力学特性仿真分析
Institute of Scientific and Technical Information of China (English)
罗明军; 郜二妙
2011-01-01
Based on the dynamic simulation analysis software ADAMS/CAR automobile macpherson front suspension system was built, silulated and ansysed by using parallel wheel travel.The thesis had acquired dynamic feature for macpherson front suspension in the case of automobiles running,for wheel bearing front suspension, vertical stiffness, frequency of the front side and wheel Alignment Parameters.It put up plan for adjustment of system performance of macpherson front suspension.%基于动力学仿真分析软件ADAMS/CAR建立了汽车麦弗逊前悬架的仿真模型,采用双轮同向激振方式对汽车麦弗逊前悬架虚拟样机模型进行动力学仿真分析,得到了在汽车运行过程中汽车麦弗逊前悬架的前悬架轮荷、垂直刚度、车身前偏频、车轮定位参数等悬架的主要参数随车轮的跳动变化情况,提出了改善麦弗逊前悬架系统性能的调整方案.
Energy Technology Data Exchange (ETDEWEB)
Greene, Patrick T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Schofield, Samuel P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Nourgaliev, Robert [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-06-21
A new mesh smoothing method designed to cluster mesh cells near a dynamically evolving interface is presented. The method is based on weighted condition number mesh relaxation with the weight function being computed from a level set representation of the interface. The weight function is expressed as a Taylor series based discontinuous Galerkin projection, which makes the computation of the derivatives of the weight function needed during the condition number optimization process a trivial matter. For cases when a level set is not available, a fast method for generating a low-order level set from discrete cell-centered elds, such as a volume fraction or index function, is provided. Results show that the low-order level set works equally well for the weight function as the actual level set. Meshes generated for a number of interface geometries are presented, including cases with multiple level sets. Dynamic cases for moving interfaces are presented to demonstrate the method's potential usefulness to arbitrary Lagrangian Eulerian (ALE) methods.
Greene, Patrick T.; Schofield, Samuel P.; Nourgaliev, Robert
2017-04-01
A new mesh smoothing method designed to cluster cells near a dynamically evolving interface is presented. The method is based on weighted condition number mesh relaxation with the weight function computed from a level set representation of the interface. The weight function is expressed as a Taylor series based discontinuous Galerkin projection, which makes the computation of the derivatives of the weight function needed during the condition number optimization process a trivial matter. For cases when a level set is not available, a fast method for generating a low-order level set from discrete cell-centered fields, such as a volume fraction or index function, is provided. Results show that the low-order level set works equally well as the actual level set for mesh smoothing. Meshes generated for a number of interface geometries are presented, including cases with multiple level sets. Dynamic cases with moving interfaces show the new method is capable of maintaining a desired resolution near the interface with an acceptable number of relaxation iterations per time step, which demonstrates the method's potential to be used as a mesh relaxer for arbitrary Lagrangian Eulerian (ALE) methods.
Greene, Patrick; Schofield, Sam; Nourgaliev, Robert
2016-11-01
A new mesh smoothing method designed to cluster cells near a dynamically evolving interface is presented. The method is based on weighted condition number mesh relaxation with the weight function being computed from a level set representation of the interface. The weight function is expressed as a Taylor series based discontinuous Galerkin (DG) projection, which makes the computation of the derivatives of the weight function needed during the condition number optimization process a trivial matter. For cases when a level set is not available, a fast method for generating a low-order level set from discrete cell-centered fields, such as a volume fraction or index function, is provided. Results show that the low-order level set works equally well for the weight function as the actual level set. The method retains the excellent smoothing capabilities of condition number relaxation, while providing a method for clustering mesh cells near regions of interest. Dynamic cases for moving interfaces are presented to demonstrate the method's potential usefulness as a mesh relaxer for arbitrary Lagrangian Eulerian (ALE) methods. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
A 155-dB Dynamic Range Current Measurement Front End for Electrochemical Biosensing.
Dai, Shanshan; Perera, Rukshan T; Yang, Zi; Rosenstein, Jacob K
2016-10-01
An integrated current measurement system with ultra wide dynamic range is presented and fabricated in a 180-nm CMOS technology. Its dual-mode design provides concurrent voltage and frequency outputs, without requiring an external clock source. An integrator-differentiator core provides a voltage output with a noise floor of 11.6 fA/ [Formula: see text] and a -3 dB cutoff frequency of 1.4 MHz. It is merged with an asynchronous current-to-frequency converter, which generates an output frequency linearly proportional to the input current. Together, the voltage and frequency outputs yield a current measurement range of 155 dB, spanning from 204 fA (100 Hz) or 1.25 pA (10 kHz) to 11.6 μA. The proposed architecture's low noise, wide bandwidth, and wide dynamic range make it ideal for measurements of highly nonlinear electrochemical and electrophysiological systems.
Energy Technology Data Exchange (ETDEWEB)
Zhou, Yijie [ORNL; Lim, Hyun-Kyung [ORNL; de Almeida, Valmor F [ORNL; Navamita, Ray [State University of New York, Stony Brook; Wang, Shuqiang [State University of New York, Stony Brook; Glimm, James G [ORNL; Li, Xiao-lin [State University of New York, Stony Brook; Jiao, Xiangmin [ORNL
2012-06-01
This progress report describes the development of a front tracking method for the solution of the governing equations of motion for two-phase micromixing of incompressible, viscous, liquid-liquid solvent extraction processes. The ability to compute the detailed local interfacial structure of the mixture allows characterization of the statistical properties of the two-phase mixture in terms of droplets, filaments, and other structures which emerge as a dispersed phase embedded into a continuous phase. Such a statistical picture provides the information needed for building a consistent coarsened model applicable to the entire mixing device. Coarsening is an undertaking for a future mathematical development and is outside the scope of the present work. We present here a method for accurate simulation of the micromixing dynamics of an aqueous and an organic phase exposed to intense centrifugal force and shearing stress. The onset of mixing is the result of the combination of the classical Rayleigh- Taylor and Kelvin-Helmholtz instabilities. A mixing environment that emulates a sector of the annular mixing zone of a centrifugal contactor is used for the mathematical domain. The domain is small enough to allow for resolution of the individual interfacial structures and large enough to allow for an analysis of their statistical distribution of sizes and shapes. A set of accurate algorithms for this application requires an advanced front tracking approach constrained by the incompressibility condition. This research is aimed at designing and implementing these algorithms. We demonstrate verification and convergence results for one-phase and unmixed, two-phase flows. In addition we report on preliminary results for mixed, two-phase flow for realistic operating flow parameters.
Analytical, Computational Fluid Dynamics and Flight Dynamics of Coandă MAV
Djojodihardjo, H.; Ahmed, RI
2016-11-01
The paper establishes the basic working relationships among various relevant variables and parameters governing the aerodynamics forces and performance measures of Coandă MAV in hover and translatory motion. With such motivation, capitalizing on the basic fundamental principles, the Fluid Dynamics and Flight Mechanics of semi-spherical Coandă MAV configurations are revisited and analyzed as a baseline. To gain better understanding on the principle of Coandă MAV lift generation, a mathematical model for a spherical Coandă MAV is developed and analyzed from first physical principles. To gain further insight into the prevailing flow field around a Coandă MAV, as well as to verify the theoretical prediction presented in the work, a computational fluid dynamic CFD simulation for a Coandă MAV generic model are elaborated using commercial software FLUENT®. In addition, the equation of motion for translatory motion of Coandă MAV is elaborated. The mathematical model and derived performance measures are shown to be capable in describing the physical phenomena of the flow field of the semi-spherical Coandă MAV. The relationships between the relevant parameters of the mathematical model of the Coandă MAV to the forces acting on it are elaborated subsequently.
Relativistic vortex dynamics in axisymmetric stationary perfect fluid configuration
Prasad, G.
2017-06-01
Relativistic formulation of Helmholtz's vorticity transport equation is presented on the basis of Maxwell-like version of Euler's equation of motion. Entangled characteristics associated with vorticity flux conservation in a vortex tube and in a stream tube are displayed on basis of Greenberg's theory of spacelike congruence of vortex lines and 1+1+(2) decomposition of the gradient of fluid's 4-velocity. Vorticity flux surfaces are surfaces of revolution about the rotation axis and are rotating with fluid's angular velocity due to gravitational isorotation in a stationary axisymmetric perfect fluid configuration. Fluid's angular velocity, angular momentum per baryon, injection energy, and invariant rotational potential are constant on such vorticity flux surfaces. Gravitation causes distortion of coaxial cylindrical vorticity flux surfaces in the limit of post-Newtonian approximation. The rotation of the fluid with angular velocity relative to vorticity flux surfaces generates swirl which causes the stretching of material vortex lines being wrapped on vorticity flux surfaces. Fluid helicity which is conserved in the fluid's rest frame does not remain conserved in a locally nonrotating frame because of the existence of swirl. Vortex lines are twist free in the absence of meridional circulations, but the twisting of spacetime due to dragging effect leads to the increase in vorticity flux in a vortex tube.
Flow study in channel with the use computational fluid dynamics (CFD)
Oliveira, W. D.; Pires, M. S. G.; Canno, L. M.; Ribeiro, L. C. L. J.
2016-08-01
The Computational Fluid Dynamics (CFD) is a tool used to numerically simulate fluid flow behavior, and all the laws that govern the study of fluids is the mass transfer and energy, chemical reactions, hydraulic behaviors, among others applications. This tool mathematical equation solves the problem in a specific manner over a region of interest, with predetermined boundary conditions on this region. This work is to study the flow channel through the CFD technique.
Dynamics of Biomembranes: Effect of the Bulk Fluid
Bonito, A.
2011-01-01
We derive a biomembrane model consisting of a fluid enclosed by a lipid membrane. The membrane is characterized by its Canham-Helfrich energy (Willmore energy with area constraint) and acts as a boundary force on the Navier-Stokes system modeling an incompressible fluid. We give a concise description of the model and of the associated numerical scheme. We provide numerical simulations with emphasis on the comparisons between different types of flow: the geometric model which does not take into account the bulk fluid and the biomembrane model for two different regimes of parameters. © EDP Sciences, 2011.
Modeling of Dynamic Fluid Forces in Fast Switching Valves
DEFF Research Database (Denmark)
Roemer, Daniel Beck; Johansen, Per; Pedersen, Henrik Clemmensen
2015-01-01
Switching valves experience opposing fluid forces due to movement of the moving member itself, as the surrounding fluid volume must move to accommodate the movement. This movement-induced fluid force may be divided into three main components; the added mass term, the viscous term and the socalled...... is given using an analytically solvable example, showing the explicit form of the force terms and highlighting the significance of the added mass and history term in certain fast switching valve applications. A general approximate model for arbitrary valve geometries is then proposed with offset...
Dynamic Analysis of Fluid Power Drive-trains for Variable Speed Wind Turbines: a Parameter Study
Jarquin Laguna, A.; Diepeveen, N.F.B.
2013-01-01
In the pursuit of making wind energy technology more economically attractive, the application of fluid power technology for the transmission of wind energy is being developed by several parties all over the world. This paper presents a dynamic model of a fluid power transmission for variable speed w
Direct control of the small-scale energy balance in two-dimensional fluid dynamics
Frank, Jason; Leimkuhler, Benedict; Myerscough, Keith W.
2015-01-01
We explore the direct modification of the pseudo-spectral truncation of two-dimensional, incompressible fluid dynamics to maintain a prescribed kinetic energy spectrum. The method provides a means of simulating fluid states with defined spectral properties, for the purpose of matching simulation sta
Dynamic Analysis of Fluid Power Drive-trains for Variable Speed Wind Turbines: a Parameter Study
Jarquin Laguna, A.; Diepeveen, N.F.B.
2013-01-01
In the pursuit of making wind energy technology more economically attractive, the application of fluid power technology for the transmission of wind energy is being developed by several parties all over the world. This paper presents a dynamic model of a fluid power transmission for variable speed w
Many-body dissipative particle dynamics modeling of fluid flow in fine-grained nanoporous shales
Xia, Yidong; Goral, Jan; Huang, Hai; Miskovic, Ilija; Meakin, Paul; Deo, Milind
2017-05-01
A many-body dissipative particle dynamics model, namely, MDPD, is applied for simulation of pore-scale, multi-component, multi-phase fluid flows in fine-grained, nanoporous shales. Since this model is able to simultaneously capture the discrete features of fluid molecules in nanometer size pores and continuum fluid dynamics in larger pores, and is relatively easy to parameterize, it has been recognized as being particularly suitable for simulating complex fluid flow in multi-length-scale nanopore networks of shales. A remarkable feature of this work is the integration of a high-resolution FIB-SEM (focused ion beam scanning electron microscopy) digital imaging technique to the MDPD model for providing 3D voxel data that contain the invaluable geometrical and compositional information of shale samples. This is the first time that FIB-SEM is seamlessly linked to a Lagrangian model like MDPD for fluid flow simulation, which offers a robust approach to bridging gaps between the molecular- and continuum-scales, since the relevant spatial and temporal scales are too big for molecular dynamics, and too small for computational fluid dynamics with known constitutive models. Simulations ranging from a number of benchmark problems to a forced two-fluid flow in a Woodford shale sample are presented. Results indicate that this model can be used to deliver reasonable simulations for multi-component, multi-phase fluid flows in arbitrarily complex pore networks in shales.
Mode-by-mode fluid dynamics for relativistic heavy ion collisions
Floerchinger, Stefan
2014-01-01
We propose to study the fluid dynamic propagation of fluctuations in relativistic heavy ion collisions differentially with respect to their azimuthal, radial and longitudinal wavelength. To this end, we introduce a background-fluctuation splitting and a Bessel-Fourier decomposition of the fluctuating modes. We demonstrate how the fluid dynamic evolution of realistic events can be build up from the propagation of individual modes. We describe the main elements of this mode-by-mode fluid dynamics, and we discuss its use in the fluid dynamic analysis of heavy ion collisions. As a first illustration, we quantify to what extent only fluctuations of sufficiently large radial wave length contribute to harmonic flow coefficients. We find that fluctuations of short wave length are suppressed not only due to larger dissipative effects, but also due to a geometrical averaging over the freeze-out hyper surface. In this way, our study further substantiates the picture that harmonic flow coefficients give access to a coars...
Terzic, Jenny; Nagarajah, Romesh; Alamgir, Muhammad
2013-01-01
Accurate fluid level measurement in dynamic environments can be assessed using a Support Vector Machine (SVM) approach. SVM is a supervised learning model that analyzes and recognizes patterns. It is a signal classification technique which has far greater accuracy than conventional signal averaging methods. Ultrasonic Fluid Quantity Measurement in Dynamic Vehicular Applications: A Support Vector Machine Approach describes the research and development of a fluid level measurement system for dynamic environments. The measurement system is based on a single ultrasonic sensor. A Support Vector Machines (SVM) based signal characterization and processing system has been developed to compensate for the effects of slosh and temperature variation in fluid level measurement systems used in dynamic environments including automotive applications. It has been demonstrated that a simple ν-SVM model with Radial Basis Function (RBF) Kernel with the inclusion of a Moving Median filter could be used to achieve the high levels...
Riemann solvers and numerical methods for fluid dynamics a practical introduction
Toro, Eleuterio F
2009-01-01
High resolution upwind and centred methods are a mature generation of computational techniques applicable to a range of disciplines, Computational Fluid Dynamics being the most prominent. This book gives a practical presentation of this class of techniques.
Fluid dynamics and noise in bacterial cell—cell and cell—surface scattering
National Research Council Canada - National Science Library
Knut Drescher; Jörn Dunkel; Luis H. Cisneros; Sujoy Ganguly; Raymond E. Goldstein
2011-01-01
.... While the importance of stochastic fluctuations has been appreciated for chemotaxis, it is currently believed that deterministic long-range fluid dynamical effects govern cell—cell and cell—surface scattering...
Sega, Marcello; Sbragaglia, Mauro; Kantorovich, Sofia Sergeevna; Ivanov, Alexey Olegovich
2013-01-01
Complex fluid-fluid interfaces featuring mesoscale structures with adsorbed particles are key components of newly designed materials which are continuously enriching the field of soft matter. Simulation tools which are able to cope with the different scales characterizing these systems are fundamental requirements for efficient theoretical investigations. In this paper we present a novel simulation method, based on the approach of Ahlrichs and D\\"unweg [Ahlrichs and D\\"unweg, Int. J. Mod. Phy...
Dynamics of non-minimally coupled perfect fluids
Bettoni, Dario
2015-01-01
We present a general formulation of the theory for a non-minimally coupled perfect fluid in which both conformal and disformal couplings are present. We discuss how such non-minimal coupling is compatible with the assumptions of a perfect fluid and derive both the Einstein and the fluid equations for such model. We found that, while the Euler equation is significantly modified with the introduction of an extra force related to the local gradients of the curvature, the continuity equation is unaltered, thus allowing for the definition of conserved quantities along the fluid flow. As an application to cosmology and astrophysics we compute the effects of the non-minimal coupling on a Friedmann--Lema\\^itre--Robertson--Walker background metric and on the Newtonian limit of our theory.
Body drop into a fluid tank and dynamic loads calculation
Directory of Open Access Journals (Sweden)
Komarov Aleksandr Andreevich
2014-05-01
Full Text Available The theory of a body striking a fluid began intensively developing due to the tasks of hydroplanes landing. For the recent years the study of a stroke and submersion of bodies into fluid became even more current. We face them in the process of strength calculation of ship hulls and other structures in modern technology. These tasks solution represents great mathematical difficulty even in case of the mentioned simplifications. These difficulties emerge due to the unsteady character of fluid motion in case of body submersion, and also jet and spray phenomena, which lead to discontinuous motions. On the basis of G.V. Logvinovich’s concept the problem of loads determination with consideration for air gap is solved for both a body and reservoir enclosing structures when a body falls into a fluid. Numerical method is based on the decay of an arbitrary discontinuity.
Dentinal fluid dynamics in human teeth, in vivo.
Ciucchi, B; Bouillaguet, S; Holz, J; Pashley, D
1995-04-01
Cavities were prepared in human premolars scheduled for extraction for orthodontic reasons. The smear layer was removed from the dentin surface by acid etching, and the cavity was sealed using a hollow chamber. The chamber was filled with sterile saline solution and connected via tubing to a hydraulic circuit featuring an adjustable pressure reservoir and a device that measures fluid movement across dentin. In the absence of any exogenous pressure, all cavities exhibited an outward fluid flow rate of 0.36 microliters min-1 cm-2. As exogenous pressure was applied to the cavity, the outward flow slowed. The exogenous pressure that stopped outward fluid flow was taken to be equal to normal pulpal tissue pressure. The mean value was 14.1 cm H2O in five teeth. This simple method permits measurement of dentinal fluid flux, the hydraulic conductance of dentin, and estimates pulpal tissue pressure.
Superconfinement tailors fluid flow at microscales.
Setu, Siti Aminah
2015-06-15
Understanding fluid dynamics under extreme confinement, where device and intrinsic fluid length scales become comparable, is essential to successfully develop the coming generations of fluidic devices. Here we report measurements of advancing fluid fronts in such a regime, which we dub superconfinement. We find that the strong coupling between contact-line friction and geometric confinement gives rise to a new stability regime where the maximum speed for a stable moving front exhibits a distinctive response to changes in the bounding geometry. Unstable fronts develop into drop-emitting jets controlled by thermal fluctuations. Numerical simulations reveal that the dynamics in superconfined systems is dominated by interfacial forces. Henceforth, we present a theory that quantifies our experiments in terms of the relevant interfacial length scale, which in our system is the intrinsic contact-line slip length. Our findings show that length-scale overlap can be used as a new fluid-control mechanism in strongly confined systems.
Superconfinement tailors fluid flow at microscales
Setu, Siti Aminah; Dullens, Roel P.A.; Hernández-Machado, Aurora; Pagonabarraga, Ignacio; Aarts, Dirk G.A.L.; Ledesma-Aguilar, Rodrigo
2015-01-01
Understanding fluid dynamics under extreme confinement, where device and intrinsic fluid length scales become comparable, is essential to successfully develop the coming generations of fluidic devices. Here we report measurements of advancing fluid fronts in such a regime, which we dub superconfinement. We find that the strong coupling between contact-line friction and geometric confinement gives rise to a new stability regime where the maximum speed for a stable moving front exhibits a distinctive response to changes in the bounding geometry. Unstable fronts develop into drop-emitting jets controlled by thermal fluctuations. Numerical simulations reveal that the dynamics in superconfined systems is dominated by interfacial forces. Henceforth, we present a theory that quantifies our experiments in terms of the relevant interfacial length scale, which in our system is the intrinsic contact-line slip length. Our findings show that length-scale overlap can be used as a new fluid-control mechanism in strongly confined systems. PMID:26073752
The effect of shadow fronts on dynamics of the surface layer during evening transitions
Pardyjak, E.; Hoch, S. W.; Jensen, D. D.; Gunawardena, N.; Di Sabatino, S.; Whiteman, C. D.; Leo, L.; Hocut, C. M.; Higgins, C. W.; Fernando, H. J.
2013-12-01
Two MATERHORN-X (Mountain Terrain Atmospheric Modeling and Observation Program) field campaigns were conducted at Dugway, UT, USA during the last year. An Autumn Campaign from 25 September - 21 October 2012 and a Spring Campaign from 1- 31 May 2013. A subset of the campaigns included dense observations along the East Slope of Granit Peak (40.096° N, -113.253° W). Observations included five multi-sonic anemometer eddy covariance towers (two with full energy budget stations), eleven small energy budget stations, fifteen automated weather stations, a distributed temperature sensing (DTS) system, hot-film anemometry, infrared camera surface temperature observations and up to three Doppler lidars. For this presentation, our analysis will focus on characterizing the response of mean wind and thermodynamics variables, as well as turbulence quantities during the evening transitions on East Slope. Previous observations have indicated that the dynamics of turbulence during evening transitions in steep mountainous terrain rapidly follows surface temperature changes associated with shadows produced by the local topography. The observations of flow transitions over the more moderate East Slope of Granite (~3-8%) indicate that wind shift direction and turbulence decay is not as tightly coupled to the shadow. Details of the transition response will be presented in the context of a new process model.
Computational Fluid Dynamics (CFD) Research Branch Technical Briefs
1993-06-09
models 13 Stability Analysis of a Combined Couette - Poiseuille , Two-Fluid Flow Lt John J. Nelson Interdisciplinary and Applied CFD Section Research...analysis and weakly non- tortion of the mean flow , the rise of the second ,armonic linear analysis for a combined Couette - Poiseuille , two and growth...Stability Analysis of a Combined Couette -Poiseulle, Two-Fluid Flow . . I I Computational Aerodynamic Analysis of a Decoy Configuration ....... 15 Euler
Dynamic changes of phase in a van der Waals fluid
Hagan, R.; Serrin, J.
1984-03-01
This paper gives sufficient conditions to guarantee the existence of a shock layer solution connecting two different equilibrium states in a van der Waals fluid. In particular, the equilibrium states can belong to two different phases of the fluid. The constitutive laws come from a modified Korteweg theory which is compatible with the Clausius Duhem inequality. The Clausius Duhem inequality in turn gives rise to a Liapunov function. The main mathematical tool is the LaSalle invariance principle.
Computational Fluid Dynamics Analysis of Butterfly Valve Performance Factors
Del Toro, Adam
2012-01-01
Butterfly valves are commonly used in industrial applications to control the internal flow of both compressible and incompressible fluids. A butterfly valve typically consists of a metal disc formed around a central shaft, which acts as its axis of rotation. As the valve's opening angle is increased from 0 degrees (fully closed) to 90 degrees (fully open), fluid is able to more readily flow past the valve. Characterizing a valve's performance factors, such as pressure drop, hydrodynamic torqu...
Suspended Sediment Transport and Fluid Mud Dynamics in Tidal Estuaries
Becker, Marius
2011-01-01
Cohesive sediments transport has been systematically studied for more than a century from field studies, laboratory experiments, and mathematical models. During the past decades, the accumulation of flocculated cohesive sediments and the formation of weakly consolidated mud deposits, including fluid mud, gained increased attention. Despite extensive research efforts, the governing processes of fluid mud formation are far from being fully understood. The primary objective of this study is to i...
Cerebrospinal fluid clearance in Alzheimer disease measured with dynamic PET
DEFF Research Database (Denmark)
De Leon, Mony J.; Li, Yi; Okamura, Nobuyuki
2017-01-01
Evidence supporting the hypothesis that reduced cerebrospinal fluid (CSF) clearance is involved in the pathophysiology of Alzheimer disease (AD) comes primarily from rodent models. However, unlike rodents, in which predominant extracranial CSF egress is via olfactory nerves traversing the cribrif......Evidence supporting the hypothesis that reduced cerebrospinal fluid (CSF) clearance is involved in the pathophysiology of Alzheimer disease (AD) comes primarily from rodent models. However, unlike rodents, in which predominant extracranial CSF egress is via olfactory nerves traversing...
THREE DIMENSIONAL MULTIPHASE COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF VENTILATED SUPERCAVITATION
Institute of Scientific and Technical Information of China (English)
YANG Wugang; ZHANG Yuwen; YANG Jie; ZUO Liankai
2008-01-01
For some vehicles travelling through water, it is advantageous to cover the vehicle in a supercavity for the sake of reducing the drag acting on it. The method of artificial ventilation is most effective for generating and dominating the supercavity. This paper focuses on the numerical simulation of flow field around three dimensional body. The method is based on the multiphase computational fluid dynamics (CFD) model combined with the turbulence model and the full cavity model. The flow field of cavity is simulated by solving the compressible Navier-Stokes equations. The fundamental similarity parameters of ventilated supercavitaty flows that include cavitation number, Froude number, ventilation rate and drag coefficient are all investigated numerically in the case of steady flow and gravity field. We discuss the following simulations results in section 3: The variations of the cavitation number and the supercavity's relative diameter with ventilation rate (subtopic 3.1); The drag coefficient versus the cavitation number (subtopic 3.2); Deformation of supercavity axis caused by gravitational effect for three different fixed Froude numbers-2.8, 3.4, 4.2 (subtopic 3.3). In subtopic 3.2, we give the comparison results of the drag reduction ratio among numerical simulation and experiment conducted in hydrodynamic tunnel and towing tank respectively. In subtopic 3.3, we summarize our discussion of gravitational effect on the axis deformation of supercavity as follows: In the case of smaller Froude number, the inclination of the cavity axis increases monotonously with increasing horizontal length, and reaches its maximal value at the end of supercavity; This deformation can be almost completely negligible when the Froude number Fr>7. The comparisons with the experimental data in the hydrodynamic tunnel and the towing tank indicate that the present method is effective for predicting the flows around ventilated supercavity; that the numerical results is in good agreement
Thermodynamics and fluid dynamics of effusive subglacial eruptions
Höskuldsson, A.; Sparks, R. S. J.
We consider the thermodynamic and fluid dynamic processes that occur during subglacial effusive eruptions. Subglacial eruptions typically generate catastrophic floods (jökulhlaups) due to melting of ice by lava and generation of a large water cavity. We consider the heat transfer from basaltic and rhyolitic lava eruptions to the ice for typical ranges of magma discharge and geometry of subglacial lavas in Iceland. Our analysis shows that the heat flux out of cooling lava is large enough to sustain vigorous natural convection in the surrounding meltwater. In subglacial eruptions the temperature difference driving convection is in the range 10-100 °C. Average temperature of the meltwater must exceed 4 °C and is usually substantially greater. We calculate melting rates of the walls of the ice cavity in the range 1-40m/day, indicating that large subglacial lakes can form rapidly as observed in the 1918 eruption of Katla and the 1996 eruption of Gjálp fissure in Vatnajökull. The volume changes associated with subglacial eruptions can cause large pressure changes in the developing ice cavity. These pressure changes can be much larger than those associated with variation of bedrock and glacier surface topography. Previous models of water-cavity stability based on hydrostatic and equilibrium conditions may not be applicable to water cavities produced rapidly in volcanic eruptions. Energy released by cooling of basaltic lava at the temperature of 1200 °C results in a volume deficiency due to volume difference between ice and water, provided that heat exchange efficiency is greater than approximately 80%. A negative pressure change inhibits escape of water, allowing large cavities to build up. Rhyolitic eruptions and basaltic eruptions, with less than approximately 80% heat exchange efficiency, cause positive pressure changes promoting continual escape of meltwater. The pressure changes in the water cavity can cause surface deformation of the ice. Laboratory
Computational fluid dynamics analysis of aerosol deposition in pebble beds
Mkhosi, Margaret Msongi
2007-12-01
The Pebble Bed Modular Reactor is a high temperature gas cooled reactor which uses helium gas as a coolant. The reactor uses spherical graphite pebbles as fuel. The fuel design is inherently resistant to the release of the radioactive material up to high temperatures; therefore, the plant can withstand a broad spectrum of accidents with limited release of radionuclides to the environment. Despite safety features of the concepts, these reactors still contain large inventories of radioactive materials. The transport of most of the radioactive materials in an accident occurs in the form of aerosol particles. In this dissertation, the limits of applicability of existing computational fluid dynamics code FLUENT to the prediction of aerosol transport have been explored. The code was run using the Reynolds Averaged Navier-Stokes turbulence models to determine the effects of different turbulence models on the prediction of aerosol particle deposition. Analyses were performed for up to three unit cells in the orthorhombic configuration. For low flow conditions representing natural circulation driven flow, the laminar flow model was used and the results were compared with existing experimental data for packed beds. The results compares well with experimental data in the low flow regime. For conditions corresponding to normal operating of the reactor, analyses were performed using the standard k-ɛ turbulence model. From the inertial deposition results, a correlation that can be used to estimate the deposition of aerosol particles within pebble beds given inlet flow conditions has been developed. These results were converted into a dimensionless form as a function of a modified Stokes number. Based on results obtained in the laminar regime and for individual pebbles, the correlation developed for the inertial impaction component of deposition is believed to be credible. The form of the correlation developed also allows these results to be applied to pebble beds of different
Computational Fluid Dynamics Simulation of Dual Bell Nozzle Film Cooling
Braman, Kalen; Garcia, Christian; Ruf, Joseph; Bui, Trong
2015-01-01
Marshall Space Flight Center (MSFC) and Armstrong Flight Research Center (AFRC) are working together to advance the technology readiness level (TRL) of the dual bell nozzle concept. Dual bell nozzles are a form of altitude compensating nozzle that consists of two connecting bell contours. At low altitude the nozzle flows fully in the first, relatively lower area ratio, nozzle. The nozzle flow separates from the wall at the inflection point which joins the two bell contours. This relatively low expansion results in higher nozzle efficiency during the low altitude portion of the launch. As ambient pressure decreases with increasing altitude, the nozzle flow will expand to fill the relatively large area ratio second nozzle. The larger area ratio of the second bell enables higher Isp during the high altitude and vacuum portions of the launch. Despite a long history of theoretical consideration and promise towards improving rocket performance, dual bell nozzles have yet to be developed for practical use and have seen only limited testing. One barrier to use of dual bell nozzles is the lack of control over the nozzle flow transition from the first bell to the second bell during operation. A method that this team is pursuing to enhance the controllability of the nozzle flow transition is manipulation of the film coolant that is injected near the inflection between the two bell contours. Computational fluid dynamics (CFD) analysis is being run to assess the degree of control over nozzle flow transition generated via manipulation of the film injection. A cold flow dual bell nozzle, without film coolant, was tested over a range of simulated altitudes in 2004 in MSFC's nozzle test facility. Both NASA centers have performed a series of simulations of that dual bell to validate their computational models. Those CFD results are compared to the experimental results within this paper. MSFC then proceeded to add film injection to the CFD grid of the dual bell nozzle. A series of
Immersed Particle Dynamics in Fluctuating Fluids with Memory
Hohenegger, Christel; McKinley, Scott
2014-11-01
Multibead passive microrheology characterizes bulk fluid properties of viscoelastic liquids by connecting statistically measurable quantities (e.g. mean-square displacement, auto-correlation to mechanical fluid properties (loss and storage modulus). Understanding how these material properties relate to biological quantities (e.g. exit time, first passage time through a layer) is of crucial importance for many pharmaceutical and industrial applications. To correctly model the correlations due to the fluid's memory, it is necessary to include a thermally fluctuating stress in the Stokes equations (Landau and Lifschitz 1958). We present such a model for an immersed particle passively advected by a fluctuating Maxwellian fluid. We describe the resulting stochastic partial differential equations for the underlying non-Markovian, stationary fluid velocity process and we present a covariance based numerical method for generating particle paths. Finally, we apply standard experimental one and two-point microrheology protocol to recover bulk loss and storage modulus and quantify the resulting errors. Our approach can be applied to a Stokes fluid with memory created by a large suspension of active swimmers or to the diffusion of a particle in a crowded environment.
DEFF Research Database (Denmark)
Dam Jensen, Mette; Ingildsen, Pernille; Rasmussen, Michael R.;
2005-01-01
shown to be more effective than others. To improve the design of less effective plants Computational Fluid Dynamics (CFD) modelling of hydraulics and sedimentation has been applied. The paper discusses the results at one particular plant experiencing problems with partly short-circuiting of the inlet...... been suggested and tested by means of computational fluid dynamics modelling. The most promissing design change have been found and reported....
Convective chemical fronts in a Poiseuille flow.
Vasquez, Desiderio A
2007-11-01
Autocatalytic reaction fronts propagating in a Poiseuille flow present a change of speed and curvature depending on the strength of the flow and on the direction of front propagation. These chemical fronts separate reacted and unreacted fluids of different densities, consequently convection will always be present due to the horizontal density gradient of the curved front. In this paper, we find the change of speed caused by gravity for fronts propagating in vertical tubes under a Poiseuille flow. For small density differences, we find axisymmetric fronts. Our theory predicts a transition to nonaxisymmetric fronts as the distance between the walls is increased. The transition depends on the average speed of the Poiseuille flow.
Macqueron, Corentin
2014-01-01
The traditional sauna is studied from a thermal and fluid dynamics standpoint using the NIST's Fire Dynamics Simulator (FDS) software. Calculations are performed in order to determine temperature and velocity fields, heat flux, soot and steam cloud transport, etc. Results are discussed in order to assess the reliability of this new kind of utilization of the FDS fire safety engineering software.
Directory of Open Access Journals (Sweden)
Andrew James Cooper
2015-08-01
Full Text Available This paper presents an unmanned aircraft system (UAS that uses a probabilistic model for autonomous front-on environmental sensing or photography of a target. The system is based on low-cost and readily-available sensor systems in dynamic environments and with the general intent of improving the capabilities of dynamic waypoint-based navigation systems for a low-cost UAS. The behavioural dynamics of target movement for the design of a Kalman filter and Markov model-based prediction algorithm are included. Geometrical concepts and the Haversine formula are applied to the maximum likelihood case in order to make a prediction regarding a future state of a target, thus delivering a new waypoint for autonomous navigation. The results of the application to aerial filming with low-cost UAS are presented, achieving the desired goal of maintained front-on perspective without significant constraint to the route or pace of target movement.
Srikanth, S
2014-01-01
The proposed upgrade for the LHCb experiment envisages a system of 500 Data sources each generating data at 100 Gbps, the acquisition and processing of which is a big challenge even for the current state of the art FPGAs. This requires an FPGA DAQ module that not only handles the data generated by the experiment but also is versatile enough to dynamically adapt to potential inadequacies of other components like the network and PCs. Such a module needs to maintain real time operation while at the same time maintaining system stability and overall data integrity. This also creates a need for a Front-end source Emulator capable of generating the various data patterns, that acts as a testbed to validate the functionality and performance of the Header Generator. The rest of the abstract briefly describes these modules and their implementation. The Header Generator is used to packetize the streaming data from the detectors before it is sent to the PCs for further processing. This is achieved by continuously scannin...
Dynamics of Shells and Fluid-Loaded Plates.
Wang, Zhang
This thesis is composed of two parts. The first part is concerned with wave propagation on elastic structures in vacuum. An asymptotic approximation is obtained for the dispersion relation of flexural waves propagating in an infinite, flat plate, with material and/or geometric properties periodic in one direction. A matrix approach is proposed to investigate waves in circular cylindrical thin shells joined with circular plates. Both the general propagator matrix and S-matrix formalisms are presented, with emphasis on the latter. The second part is devoted to structures with ambient fluid loading. The Green's function for a fluid-loaded plate under line loading is expressed as a sum of five fluid-loaded plate waves and an acoustic wave with magnitude given by an infinite integral, similar to a branch cut integral. A scattering matrix approach is presented to solve wave propagation problems on fluid-loaded plates with attached ribs. The low frequency asymptotic dispersion relation for a fluid-loaded plate with infinite number of equally spaced identical ribs is derived, from which an equation of motion for the plate is inferred which is valid also at low frequencies.
The fluid dynamics of a downer fluidised bed using a cluster-based approach (CBA
Directory of Open Access Journals (Sweden)
Germán González Silva
2010-05-01
Full Text Available The fluid dynamics of a downer reactor were numerically resolved by adapting a mathematical conservation model. The mathematical model was based on the solid and fluid properties and physical characteristics using a cluster-based approach (CBA. Comparing the numerical results to the experimental data found in the literature indicated that the mathematical model could satisfactorily predict the experimental data. The mathematical simulation determined that there were three fluid dynamic areas in the downer reactor which were characterized by accelerated, slowed-down and fully-developed flow. The fully developed flow area in the downer decreased with increased gas surface speed keeping solid flux constant.
Symmetry breaking in fluid dynamics: Lie group reducible motions for real fluids
Energy Technology Data Exchange (ETDEWEB)
Holm, D.D.
1976-07-01
The physics of fluids is based on certain kinematical invariance principles, which refer to coordinate systems, dimensions, and Galilean reference frames. Other, thermodynamic, symmetry principles are introduced by the material description. In the present work, the interplay between these two kinds of invariance principles is used to solve for classes of one-dimensional non-steady isentropic motions of a fluid whose equation of state is of Mie-Gruneisen type. Also, the change in profile and attenuation of weak shock waves in a dissipative medium is studied at the level of Burgers' approximation from the viewpoint of its underlying symmetry structure. The mathematical method of approach is based on the theory of infinitesimal Lie groups. Fluid motions are characterized according to inequivalent subgroups of the full invariance group of the flow description and exact group reducible solutions are presented.
Variational discretizations for the dynamics of fluid-conveying flexible tubes
Gay-Balmaz, François; Putkaradze, Vakhtang
2016-11-01
We derive a variational approach for discretizing fluid-structure interactions, with a particular focus on the dynamics of fluid-conveying elastic tubes. Our method is based on a discretization of the fluid's back-to-labels map and a Lie group discretization of the tube's variables, coupled with an appropriately formulated discrete version of the fluid conservation law. This approach allows the development of geometric numerical schemes for the dynamics of fluid-conveying collapsible tubes, which preserve several intrinsic geometric properties of the continuous system, such as symmetries and symplecticity. In addition, our approach can also be used to derive simplified, but geometrically consistent, low-component models for further analytical and numerical analysis of the system. xml:lang="fr"