Showing papers on "Fluid dynamics published in 2006"
Book•
06 Nov 2006TL;DR: A comprehensive unified treatment of atmospheric and oceanic fluid dynamics is provided in this paper, including rotation and stratification, vorticity, scaling and approximations, and wave-mean flow interactions and turbulence.
Abstract: Fluid dynamics is fundamental to our understanding of the atmosphere and oceans. Although many of the same principles of fluid dynamics apply to both the atmosphere and oceans, textbooks tend to concentrate on the atmosphere, the ocean, or the theory of geophysical fluid dynamics (GFD). This textbook provides a comprehensive unified treatment of atmospheric and oceanic fluid dynamics. The book introduces the fundamentals of geophysical fluid dynamics, including rotation and stratification, vorticity and potential vorticity, and scaling and approximations. It discusses baroclinic and barotropic instabilities, wave-mean flow interactions and turbulence, and the general circulation of the atmosphere and ocean. Student problems and exercises are included at the end of each chapter. Atmospheric and Oceanic Fluid Dynamics: Fundamentals and Large-Scale Circulation will be an invaluable graduate textbook on advanced courses in GFD, meteorology, atmospheric science and oceanography, and an excellent review volume for researchers. Additional resources are available at www.cambridge.org/9780521849692.
1,022 citations
TL;DR: The resulting discrete Boltzmann models are based on a kinetic representation of the fluid dynamics, hence the drawbacks in conventional higher-order hydrodynamic formulations can be avoided.
Abstract: We present in detail a theoretical framework for representing hydrodynamic systems through a systematic discretization of the Boltzmann kinetic equation. The work is an extension of a previously proposed formulation. Conventional lattice Boltzmann models can be shown to be directly derivable from this systematic approach. Furthermore, we provide here a clear and rigorous procedure for obtaining higher-order approximations to the continuum Boltzmann equation. The resulting macroscopic moment equations at each level of the systematic discretization give rise to the Navier–Stokes hydrodynamics and those beyond. In addition, theoretical indications to the order of accuracy requirements are given for each discrete approximation, for thermohydrodynamic systems, and for fluid systems involving long-range interactions. All these are important for complex and micro-scale flows and are missing in the conventional Navier–Stokes order descriptions. The resulting discrete Boltzmann models are based on a kinetic representation of the fluid dynamics, hence the drawbacks in conventional higher-order hydrodynamic formulations can be avoided.
914 citations
TL;DR: In this article, the effect of finite thermal conductivity and recirculation in droplets can be taken into account using the so-called parabolic model, which is a reasonable compromise between accuracy and CPU efficiency.
724 citations
TL;DR: In this paper, a large-scale simulation of the Rayleigh-Taylor instability is presented, which reaches a Reynolds number of 32,000, far exceeding that of all previous Rayleigh−Taylor simulations, and the scaling constant cannot be found by fitting a curve to the width of the mixing layer, but can be obtained by recourse to the similarity equation for the expansion rate of the turbulent region.
Abstract: Spontaneous mixing of fluids at unstably stratified interfaces occurs in a wide variety of atmospheric, oceanic, geophysical and astrophysical flows. The Rayleigh–Taylor instability, a process by which fluids seek to reduce their combined potential energy, plays a key role in all types of fusion. Despite decades of investigation, fundamental questions regarding turbulent Rayleigh–Taylor flow persist, namely: does the flow forget its initial conditions, is the flow self-similar, what is the scaling constant, and how does mixing influence the growth rate? Here, we show results from a large direct numerical simulation addressing such questions. The simulated flow reaches a Reynolds number of 32,000, far exceeding that of all previous Rayleigh–Taylor simulations. We find that the scaling constant cannot be found by fitting a curve to the width of the mixing layer (as is common practice) but can be obtained by recourse to the similarity equation for the expansion rate of the turbulent region. Moreover, the ratio of kinetic energy to released potential energy is not constant, but exhibits a weak Reynolds number dependence, which might have profound consequences for flame propagation models in type Ia supernova simulations.
407 citations
TL;DR: A novel numerical algorithm for simulating interfacial dynamics of non-Newtonian fluids using an efficient adaptive meshing scheme governed by the phase-field variable that easily accommodates complex flow geometry and makes it possible to simulate large-scale two-phase systems of complex fluids.
378 citations
TL;DR: This study involves a spatially varying resolution, based on the so-called variable smoothing length technique, for which a new formulation of the equations is proposed, aiming at an accurate numerical simulation of solid-fluid coupling in a free surface flow context.
363 citations
Journal Article•
TL;DR: In this paper, the authors use coupled fluid flow and geomechanical fault slip analysis to estimate the maximum sustainable injection pressure during geological sequestration of CO2, and they conclude that a fully coupled numerical analysis can more accurately account for the spatial evolution of both in situ stresses and fluid pressure, and therefore results in a more accurate estimation of the CO2 injection pressure.
Abstract: This paper demonstrates the use of coupled fluid flow and geomechanical fault slip (fault reactivation) analysis to estimate the maximum sustainable injection pressure during geological sequestration of CO2. Two numerical modeling approaches for analyzing faultslip are applied, one using continuum stress-strain analysis and the other using discrete fault analysis. The results of these two approaches to numerical fault-slip analyses are compared to the results of a more conventional analytical fault-slip analysis that assumes simplified reservoir geometry. It is shown that the simplified analytical fault-slip analysis may lead to either overestimation or underestimation of the maximum sustainable injection pressure because it cannot resolve important geometrical factors associated with the injection induced spatial evolution of fluid pressure and stress. We conclude that a fully coupled numerical analysis can more accurately account for the spatial evolution of both in situ stresses and fluid pressure, and therefore results in a more accurate estimation of the maximum sustainable CO2 injection pressure.
357 citations
TL;DR: In this paper, a three-dimensional visco-plastic flow of metals and the temperature fields in friction stir welding have been modeled based on the previous work on thermomechanical processing of metals.
Abstract: Three-dimensional visco-plastic flow of metals and the temperature fields in friction stir welding have been modeled based on the previous work on thermomechanical processing of metals. The equations of conservation of mass, momentum, and energy were solved in three dimensions using spatially variable thermophysical properties and non-Newtonian viscosity. The framework for the numerical solution of fluid flow and heat transfer was adapted from decades of previous work in fusion welding. Non-Newtonian viscosity for the metal flow was calculated considering strain rate, temperature, and temperature-dependent material properties. The computed profiles of strain rate and viscosity were examined in light of the existing literature on thermomechanical processing. The heat and mass flow during welding was found to be strongly three-dimensional. Significant asymmetry of heat and mass flow, which increased with welding speed and rotational speed, was observed. Convective transport of heat was an important mechanism of heat transfer near the tool surface. The numerically simulated temperature fields, cooling rates, and the geometry of the thermomechanically affected zone agreed well with independently determined experimental values.
330 citations
01 May 2006
TL;DR: The Navier-Stokes equations were established in the 19th century as the system of nonlinear partial differential equations which describe the motion of most commonly occurring fluids in air and water, and since that time exact solutions have been sought by scientists as mentioned in this paper.
Abstract: The Navier-Stokes equations were firmly established in the 19th Century as the system of nonlinear partial differential equations which describe the motion of most commonly occurring fluids in air and water, and since that time exact solutions have been sought by scientists. Collectively these solutions allow a clear insight into the behavior of fluids, providing a vehicle for novel mathematical methods and a useful check for computations in fluid dynamics, a field in which theoretical research is now dominated by computational methods. This 2006 book draws together exact solutions from widely differing sources and presents them in a coherent manner, in part by classifying solutions via their temporal and geometric constraints. It will prove to be a valuable resource to all who have an interest in the subject of fluid mechanics, and in particular to those who are learning or teaching the subject at the senior undergraduate and graduate levels.
325 citations
TL;DR: In this paper, the authors considered the modeling of the interaction of fluid flow with flexibly supported rigid bodies, governed by the incompressible Navier-Stokes equations and modelled by employing stabilised low order velocity-pressure finite elements.
TL;DR: In this article, analytical solutions are derived, describing the transport characteristics of a non-Newtonian fluid flow in a rectangular microchannel, under the sole influence of electrokinetic forces.
Book•
01 Jan 2006
TL;DR: In this article, Navier and Stokes this article proposed a solution to the problem of finding a solution for the problem in a three-dimensional (3-dimensional) boundary layer.
Abstract: Important Nomenclature Kinematics of Fluid Motion Introduction to Continuum Motion Fluid Particles Inertial Coordinate Frames Motion of a Continuum The Time Derivatives Velocity and Acceleration Steady and Nonsteady Flow Trajectories of Fluid Particles and Streamlines Material Volume and Surface Relation between Elemental Volumes Kinematic Formulas of Euler and Reynolds Control Volume and Surface Kinematics of Deformation Kinematics of Vorticity and Circulation References Problems The Conservation Laws and the Kinetics of Flow Fluid Density and the Conservation of Mass Principle of Mass Conservation Mass Conservation Using a Control Volume Kinetics of Fluid Flow Conservation of Linear and Angular Momentum Equations of Linear and Angular Momentum Momentum Conservation Using a Control Volume Conservation of Energy Energy Conservation Using a Control Volume General Conservation Principle The Closure Problem Stokes' Law of Friction Interpretation of Pressure The Dissipation Function Constitutive Equation for Non-Newtonian Fluids Thermodynamic Aspects of Pressure and Viscosity Equations of Motion in Lagrangian Coordinates References Problems The Navier--Stokes Equations Formulation of the Problem Viscous Compressible Flow Equations Viscous Incompressible Flow Equations Equations of Inviscid Flow (Euler's Equations) Initial and Boundary Conditions Mathematical Nature of the Equations Vorticity and Circulation Some Results Based on the Equations of Motion Nondimensional Parameters in Fluid Motion Coordinate Transformation Streamlines and Stream Surfaces Navier--Stokes Equations in Stream Function Form References Problems Flow of Inviscid Fluids Introduction Part I: Inviscid Incompressible Flow The Bernoulli Constant Method of Conformal Mapping in Inviscid Flows Sources, Sinks, and Doublets in Three Dimensions Part II: Inviscid Compressible Flow Basic Thermodynamics Subsonic and Supersonic Flow Critical and Stagnation Quantities Isentropic Ideal Gas Relations Unsteady Inviscid Compressible Flow in One-dimension Steady Plane Flow of Inviscid Gases Theory of Shock Waves References Problems Laminar Viscous Flow Part I: Exact Solutions Introduction Exact Solutions Exact Solutions for Slow Motion Part II: Boundary Layers Introduction Formulation of the Boundary Layer Problem Boundary Layer on 2-D Curved Surfaces Separation of the 2-D Steady Boundary Layers Transformed Boundary Layer Equations Momentum Integral Equation Free Boundary Layers Numerical Solution of the Boundary Layer Equation Three-Dimensional Boundary Layers Momentum Integral Equations in Three Dimensions Separation and Attachment in Three Dimensions Boundary Layers on Bodies of Revolution and Yawed Cylinders Three-Dimensional Stagnation Point Flow Boundary Layer On Rotating Blades Numerical Solution of 3-D Boundary Layer Equations Unsteady Boundary Layers Second-Order Boundary Layer Theory Inverse Problems in Boundary Layers Formulation of the Compressible Boundary Layer Problem Part III: Navier--Stokes Formulation Incompressible Flow Compressible Flow Hyperbolic Equations and Conservation Laws Numerical Transformation and Grid Generation Numerical Algorithms for Viscous Compressible Flows Thin-Layer Navier--Stokes Equations (TLNS) References Problems Turbulent Flow Part I: Stability Theory and the Statistical Description of Turbulence Introduction Stability of Laminar Flows Formulation for Plane-Parallel Laminar Flows Temporal Stability at In nite Reynolds Number Numerical Algorithm for the Orr--Sommerfeld Equation Transition to Turbulence Statistical Methods in Turbulent Continuum Mechanics Statistical Concepts Internal Structure in Physical Space Internal Structure in the Wave-Number Space Theory of Universal Equilibrium Part II: Development of Averaged Equations Introduction Averaged Equations for Incompressible Flow Averaged Equations for Compressible Flow Turbulent Boundary Layer Equations Part III: Basic Empirical and Boundary Layer Results in Turbulence The Closure Problem Prandtl's Mixing-Length Hypothesis Wall-Bound Turbulent Flows Analysis of Turbulent Boundary Layer Velocity Pro les Momentum Integral Methods in Boundary Layers Differential Equation Methods in 2-D Boundary Layers Part IV: Turbulence Modeling Generalization of Boussinesq's Hypothesis Zero-Equation Modeling in Shear Layers One-Equation Modeling Two-Equation (K-Ae) Modeling Reynolds' Stress Equation Modeling Application to 2-D Thin Shear Layers Algebraic Reynolds' Stress Closure Development of A Nonlinear Constitutive Equation Current Approaches to Nonlinear Modeling Heuristic Modeling Modeling for Compressible Flow Three-Dimensional Boundary Layers Illustrative Analysis of Instability Basic Formulation of Large Eddy Simulation References Problems Mathematical Exposition 1: Base Vectors and Various Representations Introduction Representations in Rectangular Cartesian Systems Scalars, Vectors, and Tensors Differential Operations On Tensors Multiplication of A Tensor and A Vector Scalar Multiplication of Two Tensors A Collection of Usable Formulas Taylor Expansion in Vector Form Principal Axes of a Tensor Transformation of T to the Principal Axes Quadratic Form and the Eigenvalue Problem Representation in Curvilinear Coordinates Christoffel Symbols in Three Dimensions Some Derivative Relations Scalar and Double Dot Products of Two Tensors Mathematical Exposition 2: Theorems of Gauss, Green, and Stokes Gauss' Theorem Green's Theorem Stokes' Theorem Mathematical Exposition 3: Geometry of Space and Plane Curves Basic Theory of Curves Mathematical Exposition 4: Formulas for Coordinate Transformation Introduction Transformation Law for Scalars Transformation Laws for Vectors Transformation Laws for Tensors Transformation Laws for the Christoffel Symbols Some Formulas in Cartesian and Curvilinear Coordinates Mathematical Exposition 5: Potential Theory Introduction Formulas of Green Potential Theory General Representation of a Vector An Application of Green's First Formula Mathematical Exposition 6: Singularities of the First-Order ODEs Introduction Singularities and Their Classi cation Mathematical Exposition 7: Geometry of Surfaces Basic De nitions Formulas of Gauss Formulas of Weingarten Equations of Gauss Normal and Geodesic Curvatures Grid Generation in Surfaces Mathematical Exposition 8: Finite Difference Approximation Applied to PDEs Introduction Calculus of Finite Differences Iterative Root Finding Numerical Integration Finite Difference Approximations of Partial Derivatives Finite Difference Approximation of Parabolic PDEs Finite Difference Approximation of Elliptic Equations Mathematical Exposition 9: Frame Invariancy Introduction Orthogonal Tensor Arbitrary Rectangular Frames of Reference Check for Frame Invariancy Use of Q References for the Mathematical Expositions Index
TL;DR: In this paper, a three-dimensional transient model was developed for a coaxial powder injection laser cladding process, where physical phenomena including heat transfer, melting and solidification phase changes, mass addition, and fluid flow in the melt pool were modeled in a self-consistent manner.
Abstract: The coaxial laser cladding process is the heart of direct metal deposition (DMD). Rapid materials processing, such as DMD, is steadily becoming a tool for synthesis of materials, as well as rapid manufacturing. Mathematical models to develop the fundamental understanding of the physical phenomena associated with the coaxial laser cladding process are essential to further develop the science base. A three-dimensional transient model was developed for a coaxial powder injection laser cladding process. Physical phenomena including heat transfer, melting and solidification phase changes, mass addition, and fluid flow in the melt pool, were modeled in a self-consistent manner. Interactions between the laser beam and the coaxial powder flow, including the attenuation of beam intensity and temperature rise of powder particles before reaching the melt pool were modeled with a simple heat balance equation. The level-set method was implemented to track the free surface movement of the melt pool, in a continuous las...
TL;DR: A laboratory experiment is reported, demonstrating that non-magnetic quasi-keplerian flows at Reynolds numbers up to millions are essentially steady, indirectly support the magnetorotational instability as the likely cause of turbulence, even in cool disks.
Abstract: The accretion disks that harness gravitational energy to power quasars or form stars and planets are among the most efficient energy sources known. A disk around a black hole, for instance, converts rest-mass energy to radiation at up to 40% efficiency. The nature of this conversion remains something of a mystery. Taylor–Couette experiments (involving fluid flow between rotating cylinders) are central to studies of nonlinear fluid dynamics and transition to turbulence, but mostly in flow regimes irrelevant to astrophysics. In a rare example of experimental astrophysics, a Taylor–Couette apparatus was used to model the forces involved in a rotating fluid in astrophysical conditions. The results rule out purely hydrodynamic turbulence, thereby supporting magnetorotational instabilities as the likely cause of turbulence. A laboratory experiment demonstrates that non-magnetic quasi-keplerian flows at Reynolds numbers up to millions are essentially steady. By ruling out purely hydrodynamic turbulence, results support magnetorotational instabilities as the likely cause of turbulence. The most efficient energy sources known in the Universe are accretion disks. Those around black holes convert 5–40 per cent of rest-mass energy to radiation. Like water circling a drain, inflowing mass must lose angular momentum, presumably by vigorous turbulence in disks, which are essentially inviscid1. The origin of the turbulence is unclear. Hot disks of electrically conducting plasma can become turbulent by way of the linear magnetorotational instability2. Cool disks, such as the planet-forming disks of protostars, may be too poorly ionized for the magnetorotational instability to occur, and therefore essentially unmagnetized and linearly stable. Nonlinear hydrodynamic instability often occurs in linearly stable flows (for example, pipe flows) at sufficiently large Reynolds numbers. Although planet-forming disks have extreme Reynolds numbers, keplerian rotation enhances their linear hydrodynamic stability, so the question of whether they can be turbulent and thereby transport angular momentum effectively is controversial3,4,5,6,7,8,9,10,11,12,13,14,15. Here we report a laboratory experiment, demonstrating that non-magnetic quasi-keplerian flows at Reynolds numbers up to millions are essentially steady. Scaled to accretion disks, rates of angular momentum transport lie far below astrophysical requirements. By ruling out purely hydrodynamic turbulence, our results indirectly support the magnetorotational instability as the likely cause of turbulence, even in cool disks.
TL;DR: In this paper, a new methodology is proposed for the topology optimization of fluid in Stokes flow, where the binary design variable and no-slip condition along the solid-fluid interface are regularized to allow for the use of continuous mathematical programming techniques.
Abstract: A new methodology is proposed for the topology optimization of fluid in Stokes flow. The binary design variable and no-slip condition along the solid–fluid interface are regularized to allow for the use of continuous mathematical programming techniques. The regularization is achieved by treating the solid phase of the topology as a porous medium with flow governed by Darcy's law. Fluid flow throughout the design domain is then expressed as a single system of equations created by combining and scaling the Stokes and Darcy equations. The mixed formulation of the new Darcy–Stokes system is solved numerically using existing stabilized finite element methods for the individual flow problems. Convergence to the no-slip condition is demonstrated by assigning a low permeability to solid phase and results suggest that auxiliary boundary conditions along the solid–fluid interface are not needed. The optimization objective considered is to minimize dissipated power and the technique is used to solve examples previously examined in literature. The advantages of the Darcy–Stokes approach include that it uses existing stabilization techniques to solve the finite element problem, it produces 0–1 (void–solid) topologies (i.e. there are no regions of artificial material), and that it can potentially be used to optimize the layout of a microscopically porous material. Copyright © 2005 John Wiley & Sons, Ltd.
TL;DR: In this paper, the authors investigated the amount of attenuation and velocity dispersion caused by different types of heterogeneities in the rock properties, namely, porosity, grain and frame moduli, permeability, and fluid properties.
Abstract: Recent research has established that the dominant P-wave attenuation mechanism in reservoir rocks at seismic frequencies is because of wave-induced fluid flow (mesoscopic loss). The P-wave induces a fluid-pressure difference at mesoscopic-scale inhomogeneities (larger than the pore size but smaller than the wavelength, typically tens of centimeters) and generates fluid flow and slow (diffusion) Biot waves (continuity of pore pressure is achieved by energy conversion to slow P-waves, which diffuse away from the interfaces). In this context, we consider a periodically stratified medium and investigate the amount of attenuation (and velocity dispersion) caused by different types of heterogeneities in the rock properties, namely, porosity, grain and frame moduli, permeability, and fluid properties. The most effective loss mechanisms result from porosity variations and partial saturation, where one of the fluids is very stiff and the other is very compliant, such as, a highly permeable sandstone at shallow depths, saturated with small amounts of gas (around 10% saturation) and water. Grain- and frame-moduli variations are the next cause of attenuation. The relaxation peak moves towards low frequencies as the (background) permeability decreases and the viscosity and thickness of the layers increase. The analysis indicates in which cases the seismic band is in the relaxed regime, and therefore, when the Gassmann equation can yield a good approximation to the wave velocity.
TL;DR: The method couples a semi-implicit discretization for solving the surfactant transport equation recently developed by Xu and Zhao with the immersed interface method originally developed by LeVeque and Li, for the first time that the level-set method has been used to simulate fluid interfaces with surfactants.
TL;DR: In this paper, a two-scale numerical model is developed for fluid flow in fractured, deforming porous media, where the flow in the cavity of a fracture is modelled as a viscous fluid.
Abstract: A two-scale numerical model is developed for fluid flow in fractured, deforming porous media. At the microscale the flow in the cavity of a fracture is modelled as a viscous fluid. From the micromechanics of the flow in the cavity, coupling equations are derived for the momentum and the mass couplings to the equations for a fluid-saturated porous medium, which are assumed to hold on the macroscopic scale. The finite element equations are derived for this two-scale approach and integrated over time. By exploiting the partition-of-unity property of the finite element shape functions, the position and direction of the fractures is independent from the underlying discretization. The resulting discrete equations are non-linear due to the non-linearity of the coupling terms. A consistent linearization is given for use within a Newton–Raphson iterative procedure. Finally, examples are given to show the versatility and the efficiency of the approach, and show that faults in a deforming porous medium can have a significant effect on the local as well as on the overall flow and deformation patterns. Copyright © 2006 John Wiley & Sons, Ltd.
TL;DR: In this paper, a numerical model based on smoothed particle hydrodynamics (SPH) was developed and used to simulate immiscible and miscible fluid flows in porous media and to study effects of pore scale heterogeneity and anisotropy on such flows.
TL;DR: Object-oriented programming techniques were applied in developing the program to facilitate a modular, highly flexible and customizable design platform and in building a graphic user-friendly interface.
Abstract: A simulation and design tool to improve effectiveness and efficiency in design, and analysis of air to refrigerant heat exchangers, CoilDesigner, is introduced. A network viewpoint was adopted to establish the general-purpose solver and allow for analysis of arbitrary tube circuitry and mal-distribution of fluid flow inside the tube circuits. A segment-by-segment approach within each tube was implemented, to account for two-dimensional non-uniformity of air distribution across the heat exchanger, and heterogeneous refrigerant flow patterns through a tube. Coupled heat exchangers with multiple fluids inside different subsets of tubes can be modeled and analyzed simultaneously. A further sub-dividing-segment model was developed in order to address the significant change of properties and heat transfer coefficients in the single-phase and two-phase regime when a segment experiences flow regime change. Object-oriented programming techniques were applied in developing the program to facilitate a modular, highly flexible and customizable design platform and in building a graphic user-friendly interface. A wide variety of working fluids and correlations of heat transfer and pressure drop are available at the user's choice. The model prediction with CoilDesigner was verified against experimentally determined data collected from a number of sources.
Book•
01 Jan 2006TL;DR: In this paper, the Lagrangian Formulation is used to define real fluids and their dynamics, including wave, instabilities and vortices, as well as the relative dispersion of real fluids.
Abstract: Part I. The Lagrangian Formulation: 1. Lagrangian kinematics 2. Lagrangian statistics 3. Lagrangian dynamics 4. Coordinates 5. Real fluids Part II. Lagrangian Flows: 6. Some analytical Lagrangian solutions 7. Waves, instabilities and vortices 8. Viscous incompressible flow 9. General solvability Part III. Diffusion: 10. Absolute dispersion 11. Relative dispersion 12. Convective subranges, scalar variance spectrum 13. Diffusion Part IV. Lagrangian Data: 14. Observing systems 15. Data analysis: the single particle 16. Data analysis: particle clusters References.
TL;DR: In this paper, numerical simulation of the fluid flow and particle dynamics is presented by CFD technique to characterize the performance of two types of cyclones with the conventional single inlet (SI) and spiral double inlets (DI), respectively.
Abstract: The numerical simulation of the fluid flow and particle dynamics is presented by CFD technique to characterize the performance of two types of cyclones with the conventional single inlet (SI) and spiral double inlets (DI), respectively. The Reynolds-averaged Navier-Stokes equations with the Reynolds stress turbulence model (RSM) for fluid flow are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the fluid computational domain. A Lagrangian method is employed to track the particle motion and calculate the gas–particle separation efficiency in the cyclones. According to the computational results, the differences of pressure, velocity and turbulence parameters of the gas flow are described to address the effects of the inlet geometry on the flow pattern of cyclones. Especially for the tangential velocity distribution, a key flow parameter in cyclones, are analysed using the classical Rankine vortex theories. Furthermore, the separation performances of cyclones are predicted, with the comparison of experimental data and theoretical model. The results indicate that the CFD method can effectively reveal the mechanism of gas–particle flow and separation in cyclone with different inlet configuration.
Book•
01 Jul 2006
TL;DR: In this paper, the purpose and value of geophysical fluid dynamics are discussed and a discussion of the relationship between geophysical dynamics and geophysical models is presented. But this paper is limited to geophysical modeling.
Abstract: Preface Symbols 1. Purposes and value of geophysical fluid dynamics 2. Fundamental dynamics 3. Barotropic and vortex dynamics 4. Rotating shallow-water and wave dynamics 5. Baroclinic and jet dynamics 6. Boundary-layer and wind-gyre dynamics Afterword Exercises References Index.
TL;DR: In this article, the authors provide an overview of recent advances in the theoretical modeling and numerical simulation of cryogenic fluid injection and mixing in transcritical and supercritical environments, using a general theoretical and numerical framework that accommodates full conservation laws and real-fluid thermodynamic and transport phenomena.
Abstract: This paper provides an overview of recent advances in the theoretical modeling and numerical simulation of cryogenic fluid injection and mixing in transcritical and supercritical environments. The basis of the analysis is a general theoretical and numerical framework that accommodates full conservation laws and real-fluid thermodynamic and transport phenomena. All of the thermophysical properties are determined directly from fundamental thermodynamics theories, along with the use of corresponding-state principles. Turbulence closure is achieved using a large-eddy-simulation technique, in which large-scale motions are calculated explicitly and the effects of unresolved small-scale turbulence are modeled either analytically or empirically. The analysis has been applied to study: (1) fluid jet dynamics, (2) swirl injection of liquid oxygen through a simplex swirl injector, and (3) shear co-axial injection and mixing of liquid oxygen and methane. Various effects, including density stratification, she...
14 Mar 2006
TL;DR: In this paper, a three-dimensional CFD Reynolds stress model was used to describe the gas and gas-solid flow in a cyclone with a scroll inlet duct at three different inlet section angles in relation to the cyclone body.
Abstract: A three-dimensional computational fluid dynamics (CFD) Reynolds stress model (RSM) was used to describe the gas and gas–solid flow in a cyclone with a scroll inlet duct at three different inlet section angles in relation to the cyclone body. The effects of the inlet section angles on the fluid dynamics inside the cyclone and on the performance parameters (collection efficiency and pressure drop) were analyzed by means of the finite volume method using a computational code and an industrial-sized cyclone for separation of gas-particle phases operated by Votorantim Cimentos Company. The numerical results show that the value for overall collection efficiency in this work increased to 77.2% for the 45° inlet section angle, while that for the normal inlet duct was 54.4% under the same operating conditions.
TL;DR: In this paper, the role of frictional heating and thermal pressurization on earthquake ruptures was investigated by modeling the spontaneous propagation of a 3D crack on a planar fault governed by assigned constitutive laws and allowing the evolution of effective normal stress.
Abstract: [1] We investigate the role of frictional heating and thermal pressurization on earthquake ruptures by modeling the spontaneous propagation of a three-dimensional (3-D) crack on a planar fault governed by assigned constitutive laws and allowing the evolution of effective normal stress. We use both slip-weakening and rate- and state-dependent constitutive laws; in this latter case we employ the Linker and Dieterich evolution law for the state variable, and we couple the temporal variations of friction coefficient with those of effective normal stress. In the companion paper we investigate the effects of thermal pressurization on the dynamic traction evolution. We solve the 1-D heat conduction equation coupled with Darcy's law for fluid flow in porous media. We obtain a relation that couples pore fluid pressure to the temperature evolution on the fault plane. We analytically solve the thermal pressurization problem by considering an appropriate heat source for a fault of finite thickness. Our modeling results show that thermal pressurization reduces the temperature increase caused by frictional heating. However, the effect of the slipping zone thickness on temperature changes is stronger than that of thermal pressurization, at least for a constant porosity model. Pore pressure and effective normal stress evolution affect the dynamic propagation of the earthquake rupture producing a shorter breakdown time and larger breakdown stress drop and rupture velocity. The evolution of the state variable in the framework of rate- and state-dependent friction laws is very different when thermal pressurization is active. In this case the evolution of the friction coefficient differs substantially from that inferred from a slip-weakening law. This implies that the traction evolution and the dynamic parameters are strongly affected by thermal pressurization.
01 Jan 2006
TL;DR: In this paper, the dispersion coefficients of a fluid through random packing of non-overlapping spheres in a cylindrical geometry are investigated and the results compare to the previous work (Soleymani et al., 2002).
Abstract: Numerical study of flow through random packing of non-overlapping spheres in a cylindrical geometry is investigated. Dimensionless pressure drop has been studied for a fluid through the porous media at moderate Reynolds numbers (based on pore permeability and interstitial fluid velocity), and numerical solution of Navier-Stokes equations in three dimensional porous packed bed illustrated in excellent agreement with those reported by Macdonald [1979] in the range of Reynolds number studied. The results compare to the previous work (Soleymani et al., 2002) show more accurate conclusion because the problem of channeling in a duct geometry. By injection of solute into the system, the dispersivity over a wide range of flow rate has been investigated. It is shown that the lateral fluid dispersion coefficients can be calculated by comparing the concentration profiles of solute obtained by numerical simulations and those derived analytically by solving the macroscopic dispersion equation for the present geometry.Copyright © 2006 by ASME
TL;DR: In this paper, a parallel-plate Electrowetting on dielectric (EWOD) device is used to model the fluid dynamics by using Hele-Shaw type equations with a focus on the relevant boundary phenomena.
Abstract: This paper discusses the modeling and simulation of a parallel-plate Electrowetting On Dielectric (EWOD) device that moves fluid droplets through surface tension effects. We model the fluid dynamics by using Hele-Shaw type equations with a focus on including the relevant boundary phenomena. Specifically, we show that contact angle saturation and hysteresis are needed to predict the correct shape and time scale of droplet motion. We demonstrate this by comparing our simulation to experimental data for a splitting droplet. Without these boundary effects, the simulation shows the droplet splitting into three pieces instead of two and the motion is over 15 times faster than the experiment. We then show how including the saturation characteristics of the device, and a simple model of contact angle hysteresis, allows the simulation to better predict the splitting experiment. The match is not perfect and suffers mainly because contact line pinning is not included. This is followed by a comparison between our simulation, whose parameters are now frozen, and a new experiment involving bulk droplet motion. Our numerical implementation uses the level set method, is fast, and is being used to design algorithms for the precise control of microdroplet motion, mixing, and splitting
TL;DR: In this article, the authors investigated the gravitational settling of an initially random suspension of small solid particles in homogeneous turbulence and showed that the effect of the particles on the carrier fluid involves an additional increase in their mean settling velocity compared to one-way coupling.
Abstract: The gravitational settling of an initially random suspension of small solid particles in homogeneous turbulence is investigated numerically. The simulations are based on a pseudospectral method to solve the fluid equations combined with a Lagrangian point-particle model for the particulate phase (Eulerian-Lagrangian approach). The focus is on the enhancement of the mean particle settling velocity in a turbulent carrier fluid, as compared to the settling velocity of a single particle in quiescent fluid. Results are presented for both one-way coupling, when the fluid flow is not affected by the presence of the particles, and two-way coupling, when the particles exert a feedback force on the fluid. The first case serves primarily for validation purposes. In the case with two-way coupling, it is shown that the effect of the particles on the carrier fluid involves an additional increase in their mean settling velocity compared to one-way coupling. The underlying physical mechanism is analyzed, revealing that t...