Showing papers on "Fluid dynamics published in 2001"

Shear-Dependent Boundary Slip in an Aqueous Newtonian Liquid

Abstract: We report direct measurements of hydrodynamic drainage forces, which show clear evidence of boundary slip in a Newtonian liquid. The degree of boundary slip is found to be a function of the liquid viscosity and the shear rate, as characterized by the slip length, and is up to $\ensuremath{\sim}20\mathrm{nm}$. This has implications for confined biological systems, the permeability of microporous media, and for the lubrication of nanomachines, and will be important in the microcontrol of liquid flow. We also show that current theories of slip do not adequately describe the experimental data.

Navier-Stokes Equations and Turbulence by C. Foias

Abstract: A catalog record for this book is available from the British Library.

A Comparative Analysis of Studies on Heat Transfer and Fluid Flow in Microchannels

Abstract: The extremely high rates of heat transfer obtained by employing microchannels makes them an attractive alternative to conventional methods of heat dissipation, especially in applications related to the cooling of microelectronics. A compilation and analysis of the results from investigations on fluid flow and heat transfer in micro- and mini-channels and microtubes in the literature is presented in this review, with a special emphasis on quantitative experimental results and theoretical predictions. Anomalies and deviations from the behavior expected for conventional channels, both in terms of the frictional and heat transfer characteristics, are discussed.

Stochastic rotation dynamics: a Galilean-invariant mesoscopic model for fluid flow.

Abstract: A recently introduced stochastic model for fluid dynamics with continuous velocities and efficient multiparticle collisions is investigated, and it is shown how full Galilean-invariance can be achieved for arbitrary Mach numbers. Analytic expressions for the viscosity and diffusion constant are also derived and compared with simulation results. Long-time tails in the velocity and stress autocorrelation functions are measured.

On average properties of inhomogeneous fluids in general relativity II: perfect fluid cosmologies

Abstract: We investigate effective equations governing the volume expansion of spatially averaged portions of inhomogeneous cosmologies in spacetimes filled with an arbitrary fluid. This work is a follow-up to previous studies focused on irrotational dust models (Paper I) and irrotational perfect fluids (Paper II) in flow-orthogonal foliations of spacetime. It complements them by considering arbitrary foliations, arbitrary lapse and shift, and by allowing for a tilted fluid flow with vorticity. As for the first studies, the propagation of the spatial averaging domain is chosen to follow the congruence of the fluid, which avoids unphysical dependencies in the averaged system that is obtained. We present two different averaging schemes and corresponding systems of averaged evolution equations providing generalizations of Papers I and II. The first one retains the averaging operator used in several other generalizations found in the literature. We extensively discuss relations to these formalisms and pinpoint limitations, in particular regarding rest mass conservation on the averaging domain. The alternative averaging scheme that we subsequently introduce follows the spirit of Papers I and II and focuses on the fluid flow and the associated 1+3 threading congruence, used jointly with the 3+1 foliation that builds the surfaces of averaging. This results in compact averaged equations with a minimal number of cosmological backreaction terms. We highlight that this system becomes especially transparent when applied to a natural class of foliations which have constant fluid proper time slices.

Modeling multiphase non-isothermal fluid flow and reactive geochemical transport in variably saturated fractured rocks: 1. methodology

Abstract: Reactive fluid flow and geochemical transport in unsaturated fractured rocks have received increasing attention for studies of contaminant transport, ground- water quality, waste disposal, acid mine drainage remediation, mineral deposits, sedimentary diagenesis, and fluid-rock interactions in hydrothermal systems. This paper presents methods for modeling geochemical systems that emphasize: (1) involvement of the gas phase in addition to liquid and solid phases in fluid flow, mass transport, and chemical reactions; (2) treatment of physically and chemically heterogeneous and fractured rocks, (3) the effect of heat on fluid flow and reaction properties and processes, and (4) the kinetics of fluid-rock interaction. The physical and chemical process model is embodied in a system of partial differential equations for flow and transport, coupled to algebraic equations and ordinary differential equations for chemical interactions. For numerical solution, the continuum equations are discretized in space and time. Space discretization is based on a flexible integral finite difference approach that can use irregular gridding to model geologic structure; time is discretized fully implicitly as a first-order finite difference. Heterogeneous and fractured media are treated with a general multiple interacting continua method that includes double-porosity, dual-permeability, and multi-region models as special cases. A sequential iteration approach is used to treat the coupling between fluid flow and mass transport on the one hand, chemical reactions on the other. Applications of the methods developed here to variably saturated geochemical systems are presented in a companion paper (part 2, this issue).

Phase field model for three-dimensional dendritic growth with fluid flow.

Abstract: We study the effect of fluid flow on three-dimensional (3D) dendrite growth using a phase-field model on an adaptive finite-element grid In order to simulate 3D fluid flow, we use an averaging method for the flow problem coupled to the phase-field method and the semi-implicit approximated projection method (SIAPM) We describe a parallel implementation for the algorithm, using the CHARM++ FEM framework, and demonstrate its efficiency We introduce an improved method for extracting dendrite tip position and tip radius, facilitating accurate comparison to theory We benchmark our results for 2D dendrite growth with solvability theory and previous results, finding them to be in good agreement The physics of dendritic growth with fluid flow in three dimensions is very different from that in two dimensions, and we discuss the origin of this behavior

Theory of Solidification

Abstract: 1. Introduction 2. Pure substances 3. Binary substances 4. Nonlinear theory for directional solidification 5. Anisotrophy 6. Disequilibrium 7. Dendrites 8. Eutectics 9. Microscale fluid flow 10. Mesoscale fluid flow 11. Phase-field models.

About Lifespan of Regular Solutions of Equations Related to Viscoelastic Fluids

Abstract: We prove existence and uniqueness of local and global solutions for a system of equations concerning an incompressible viscoelastic fluid of the Oldroyd type. We also show a new a priori estimate f...

Fluid Dynamics: Theory, Computation, and Numerical Simulation

Abstract: 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 book is a must for students in all fields of engineering, computational physics, scientific computing, and applied mathematics. It can be used in both undergraduate and graduate courses in fluid mechanics, aerodynamics, and computational fluid dynamics. The audience includes not only advanced undergraduate and entry-level graduate students, but also a broad class of scientists and engineers with a general interest in scientific computing.

Mathematical Modeling of Fluid Flow in Continuous Casting

Abstract: Fluid flow is very important to quality in the continuous casting of steel. With the high cost of empirical investigation and the increasing power of computer hardware and software, mathematical modeling is becoming an important tool to understand fluid flow phenomena. This paper reviews recent developments in modeling phenomena related to fluid flow in the continuous casting mold region, and the resulting implications for improving the process. These phenomena include turbulent flow in the nozzle and mold, the transport of bubbles and inclusion particles, multi-phase flow phenomena, the effect of electromagnetic forces, heat transfer, interfacial phenomena and interactions between the steel surface and the slag layers, the transport of solute elements and segregation. The work summarized in this paper can help to provide direction for further modeling investigation of the continuous casting mold, and to improve understanding of this important process.

Limits of the Turbine Efficiency for Free Fluid Flow

Abstract: An accurate estimate of the theoretical power limit of turbines in free fluid flows is important because of growing interest in the development of wind power and zero-head water power resources. The latter includes the huge kinetic energy of ocean currents, tidal streams, and rivers without dams. Knowledge of turbine efficiency limits helps to optimize design of hydro and wind power farms. An explicitly solvable new mathematical model for estimating the maximum efficiency of turbines in a free (nonducted) fluid is presented. This result can be used for hydropower turbines where construction of dams is impossible (in oceans) or undesirable (in rivers), as well as for wind power farms. The model deals with a finite two-dimensional, partially penetrable plate in an incompressible fluid. It is nearly ideal for two-dimensional propellers and less suitable for three-dimensional crossflow Darrieus and helical turbines. The most interesting finding of our analysis is that the maximum efficiency of the plane propeller is about 30 percent for free fluids. This is in a sharp contrast to the 60 percent given by the Betz limit, commonly used now for decades. It is shown that the Betz overestimate results from neglecting the curvature of the fluid streams. We also show that the three-dimensional helical turbine is more efficient than the two-dimensional propeller, at least in water applications. Moreover, well-documented tests have shown that the helical turbine has an efficiency of 35 percent, making it preferable for use in free water currents.

Global Existence in Critical Spaces¶for Flows of Compressible¶Viscous and Heat-Conductive Gases

Abstract: We are concerned with global existence and uniqueness of strong solutions for a general model of viscous and heat-conductive gases. The initial data are supposed to be close to a stable equilibrium with constant density and temperature. Using uniform estimates for the linearized system with a convection term, we get global well-posedness in a functional setting invariant with respect to the scaling of the associated equations (in space dimension N≧3). We also show a smoothing effect on the velocity and the temperature, and a decay on the difference between the density and the constant reference state. These results extend a previous paper devoted to the barotropic case (see [5]).

Multi-particle collision dynamics: Flow around a circular and a square cylinder

Abstract: A particle-based model for mesoscopic fluid dynamics is used to simulate steady and unsteady flows around a circular and a square cylinder in a two-dimensional channel for a range of Reynolds numbers between 10 and 130. Numerical results for the recirculation length, the drag coefficient, and the Strouhal number are reported and compared with previous experimental measurements and computational fluid dynamics data. The good agreement demonstrates the potential of this method for the investigation of complex flows.

Fluid flow in nanopores: An examination of hydrodynamic boundary conditions

Abstract: Steady-state Poiseuille flow of a simple fluid in carbon slit pores under a gravity-like force is simulated using a realistic empirical many-body potential model for carbon. In this work we focus on the small Knudsen number regime, where the macroscopic equations are applicable, and simulate different wetting conditions by varying the strength of fluid–wall interactions. We show that fluid flow in a carbon pore is characterized by a large slip length even in the strongly wetting case, contrary to the predictions of Tolstoi’s theory. When the surface density of wall atoms is reduced to values typical of a van der Waals solid, the streaming velocity profile vanishes at the wall, in accordance with earlier findings. From the velocity profiles we have calculated the slip length and by analyzing temporal profiles of the velocity components of particles colliding with the wall we obtained values of the Maxwell coefficient defining the fraction of molecules thermalized by the wall.

Volumetric sand production model and experiment

Abstract: A sand production model was developed for volumetric sand production predictions that take into account the effects of the external stresses and fluid flow rate. The model couples the poro-mechanical behaviour of the solid–fluid system with the erosion behaviour of the solids due to fluid flow. It predicts reasonably experimental volumetric sand production data from a hollow cylinder test on a weak sandstone. The test results show that in weak and compactive sandstones, sand production is associated with decohesioning and plasticification of a zone around the inner hole which can then be mobilized by the hydrodynamic forces of the fluid flow. The sand production rate increases both with external applied stress and fluid flow rate but it is constant with time under constant external stress and fluid flow rate. In both cases a critical lower limit has to be exceeded for sand production initiation. Copyright © 2001 John Wiley & Sons, Ltd.

Fluid flow control system, fluid delivery and control system for a fluid delivery line, and method for controlling pressure oscillations within fluid of a fluid delivery line

Abstract: A fluid delivery and control system is provided for a fluid delivery line having elastic components. The system includes a pressure sensor, an electronically controlled valve, processing circuitry, and computer program code logic. The pressure sensor is operative to detect fluid pressure within a fluid delivery line. The electronically controlled valve includes an adjustable flow regulating aperture disposed in the line, interposed along a linear flow axis, and operative to regulate fluid flow through the line. The processing circuitry communicates with the pressure sensor and the electronically controlled valve. The computer program code logic is executed by the processing circuitry and is configured to generate an output signal. The output signal comprises an operating parameter of at least one of the pressure sensor and the electronically controlled valve to adjust flow capacity of the flow regulating aperture of the valve to dissipate pressure oscillations within the fluid delivery line. A method is also provided.

Stable Isotope Transport and Contact Metamorphic Fluid Flow

Abstract: Stable isotopes are a powerful tool for deciphering the fluid histories of metamorphic terranes. The nature of fluid flow, fluid sources, and fluid fluxes can be delineated in well-constrained studies. Observed isotopic gradients in metamorphic rocks and minerals can thus shed light on many processes involved in mass-transport including diffusion, recrystallization, fluid infiltration, volatilization, metasomatism, and heat flow. Modeling of fluid flow and mineral exchange kinetics offers greatly enhanced understanding of metamorphic processes that can be tested and refined by application of new micro-analytical techniques. This review will concentrate on the principles of stable isotope fluid-rock interaction with an emphasis on fluid-rock interaction and fluid flow in contact metamorphism. Earlier reviews discuss some aspects of regional metamorphism and hydrothermal systems (Valley 1986; Kerrich 1987; Nabelek 1991; Young 1995; Ferry and Gerdes 1998; Bowman 1998). Isotopic studies are especially useful for defining the scale of fluid migration. The intensity of interaction between fluids and the minerals in rocks can be assessed. During metamorphism, the scale of isotopic exchange can vary from less than a micrometer to over 10 kilometers. Many fluid-driven processes are characterized by the degree to which fluid flow is concentrated into zones of high permeability. Thus, the definition of two end-member situations is useful. The flow of a pervasive fluid is distributed throughout the pores in a rock. Pervasive flow can be along grain boundaries or fine-scale crack networks and the effect is to homogenize the chemical potential of all components, including stable isotopes, at a macroscopic scale. In contrast, the flow of a channeled fluid is along vein systems, shear zones or other channelways such as rock contacts or more permeable lithologic units. Channeled flow leads to local chemical heterogeneity, allowing some rocks to remain unaffected while others are extensively infiltrated …

Foundations of Fluid Dynamics

Abstract: 1 Continua and Generalities About Their Equations.- 2 Empirical Algorithms.- 3 Analytical Theories and Mathematical Aspects.- 4 Incipient Turbulence and Chaos.- 5 Ordering Chaos.- 6 Developed Turbulence.- 7 Statistical Properties of Turbulence.- Name Index.- Citations Index.