Showing papers on "Fluid dynamics published in 1984"

Physical and Computational Aspects of Convective Heat Transfer

Abstract: 1 Introduction- 11 Momentum Transfer- 12 Heat and Mass Transfer- 13 Relations between Heat and Momentum Transfer- l4 Coupled and Uncoupled Flows- 15 Units and Dimensions- l6 Outline of the Book- Problems- References- 2 Conservation Equations for Mass, Momentum, and Energy- 21 Continuity Equation- 22 Momentum Equations- 23 Internal Energy and Enthalpy Equations- 24 Conservation Equations for Turbulent Flow- 25 Equations of Motion: Summary- Problems- References- 3 Boundary-Layer Equations- 3l Uncoupled Flows- 32 Estimates of Density Fluctuations in Coupled Turbulent Flows- 33 Equations for Coupled Turbulent Flows- 34 Integral Equations- 35 Boundary Conditions- 36 Thin-Shear-Layer Equations: Summary- Problems- References- 4 Uncoupled Laminar Boundary Layers- 41 Similarity Analysis- 42 Two-Dimensional Similar Flows- 43 Two-Dimensional Nonsimilar Flows- 44 Axisymmetric Flows- 45 Wall Jets and Film Cooling- Problems- References- 5 Uncoupled Laminar Duct Flows- 51 Fully Developed Duct Flow- 52 Thermal Entry Length for a Fully Developed Velocity Field- 53 Hydrodynamic and Thermal Entry Lengths- Problems- References- 6 Uncoupled Turbulent Boundary Layers- 61 Composite Nature of a Turbulent Boundary Layer- 62 The Inner Layer- 63 The Outer Layer- 64 The Whole Layer- 65 Two-Dimensional Boundary Layers with Zero Pressure Gradient- 66 Two-Dimensional Flows with Pressure Gradient- 67 Wall Jets and Film Cooling- Problems- References- 7 Uncoupled Turbulent Duct Flows- 71 Fully Developed Duct Flow- 72 Thermal Entry Length for a Fully Developed Velocity Field- 73 Hydrodynamic and Thermal Entry Lengths- Problems- References- 8 Free Shear Flows- 81 Two-Dimensional Laminar Jet- 82 Laminar Mixing Layer between Two Uniform Streams at Different Temperatures- 83 Two-Dimensional Turbulent Jet- 84 Turbulent Mixing Layer between Two Uniform Streams at Different Temperatures- 85 Coupled Flows- Problems- References- 9 Buoyant Flows- 91 Natural-Convection Boundary Layers- 92 Combined Natural- and Forced-Convection Boundary Layers- 93 Wall Jets and Film Heating or Cooling- 94 Natural and Forced Convection in Duct Flows- 95 Natural Convection in Free Shear Flows- Problems- References- 10 Coupled Laminar Boundary Layers- 101 Similar Flows- 102 Nonsimilar Flows- 103 Shock-Wave/Shear-Layer Interaction- 104 A Prescription for Computing Interactive Flows with Shocks- Problems- References- 11 Coupled Turbulent Boundary Layers- 111 Inner-Layer Similarity Analysis for Velocity and Temperature Profiles- 112 Transformations for Coupled Turbulent Flows- 113 Two-Dimensional Boundary Layers with Zero Pressure Gradient- 114 Two-Dimensional Flows with Pressure Gradient- 115 Shock-Wave/Boundary-Layer Interaction- References- 12 Coupled Duct Flows- 121 Laminar Flow in a Tube with Uniform Heat Flux- 122 Laminar, Transitional and Turbulent Flow in a Cooled Tube- References- 13 Finite-Difference Solution of Boundary-Layer Equations- 131 Review of Numerical Methods for Boundary-Layer Equations- 132 Solution of the Energy Equation for Internal Flows with Fully Developed Velocity Profile- 133 Fortran Program for Internal Laminar and Turbulent Flows with Fully Developed Velocity Profile- 134 Solution of Mass, Momentum, and Energy Equations for Boundary-Layer Flows- 135 Fortran Program for Coupled Boundary-Layer Flows- References- 14 Applications of a Computer Program to Heat-Transfer Problems- 141 Forced and Free Convection between Two Vertical Parallel Plates- 142 Wall Jet and Film Heating- 143 Turbulent Free Jet- 144 Mixing Layer between Two Uniform Streams at Different Temperatures- References- Appendix A Conversion Factors- Appendix B Physical Properties of Gases, Liquids, Liquid Metals, and Metals- Appendix C Gamma, Beta and Incomplete Beta Functions- Appendix D Fortran Program for Head's Method

Foundations of radiation hydrodynamics

Abstract: Exposes the great foundation-stones of research on radiating flows in astrophysics. Upon them are built the walls of methodology (some understandably incomplete). Concentration is on fundamentals but with only few applications. Coverage broadly involves non-radiating fluids, physics of radiation, radiation transport, and dynamics of radiating fluids, and finally the elements of sensor calculus as used in this volume. Contents, abridged: Microphysics of gases. Dynamics of ideal fluids. Relativistic fluid flow. Radiation and radiative transfer. Radiating flows. Glossary of physical symbols. Index.

Applied fluid dynamics handbook

Abstract: Applied fluid dynamics handbook , Applied fluid dynamics handbook , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

SUTRA (Saturated-Unsaturated Transport). A Finite-Element Simulation Model for Saturated-Unsaturated, Fluid-Density-Dependent Ground-Water Flow with Energy Transport or Chemically-Reactive Single-Species Solute Transport.

Abstract: : SUTRA (Saturated-Unsaturated Transport) is a computer program which simulates fluid movement and the transport of either energy or dissolved substances in a subsurface environment. The mathematical model employs a two-dimensional hybrid finite-element and integrated-finite-difference method to approximate the governing equations that describe the two interdependent processes that are simulated by SUTRA: (1) fluid density-dependent saturated or unsaturated ground-water flow, and either; (2a) transport of a solute in the ground water, in which the solute may be subject to: equilibrium adsorption on the porous matrix, and both first-order and zero-order production or decay, or, (2b) transport of thermal energy in the ground water and solid matrix of the aquifer. SUTRA provides, as the primary calculated result, fluid pressures and either solute concentrations or temperatures, as they vary with time, everywhere in the simulated subsurface system. SUTRA may also be used to simulate simpler subsets of the above process. Additional keywords: Fluid flow; Radial flow; FORTRAN. (Author)

The three‐dimensional flow due to a stretching flat surface

Abstract: An exact similarity solution of the Navier–Stokes equations is found. The solution represents the three‐dimensional fluid motion caused by the stretching of a flat boundary.

Numerical calculation of the fluid dynamics of drop-on-demand jets

Abstract: A numerical method that makes use of the complete incompressible flow equations with a free surface is discussed and used to study an impulsively driven laminar jet. Flow behavior dependence upon fluid properties (characterized by a Reynolds number over Weber number nondimensionalization) is compared jor drop integrity purposes. Several variations of square wave pressure history applied at a nozzle inlet are discussed in relation to drop velocities produced and structure of ejected drops. Timewise development of flow both interior and exterior to the nozzle is illustrated through computed contour sequences.

Double‐Porosity Models for a Fissured Groundwater Reservoir With Fracture Skin

Abstract: Theories of flow to a well in a double-porosity groundwater reservoir are modified to incorporate effects of a thin layer of low-permeability material or fracture skin that may be present at fracture-block interfaces as a result of mineral deposition or alteration. The commonly used theory for flow in double- porosity formations that is based upon the assumption of pseudo–steady state block-to-fissure flow is shown to be a special case of the theory presented in this paper. The latter is based on the assumption of transient block-to-fissure flow with fracture skin. Under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock, it may be assumed to impede the interchange of fluid between the fissures and blocks. Resistance to flow at fracture-block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks. This provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo–steady state flow model. Coupled boundary value problems for flow to a well discharging at a constant rate were solved in the Laplace domain. Both slab-shaped and sphere-shaped blocks were considered, as were effects of well bore storage and well bore skin. Results obtained by numerical inversion were used to construct dimensionless-type curves that were applied to well test data, for a pumped well and for an observation well, from the fractured volcanic rock terrane of the Nevada Test Site.

Theoretical analysis of the role of groundwater flow in the genesis of stratabound ore deposits; 1, Mathematical and numerical model

Abstract: Carbonate-hosted lead-zinc deposits of the mississippi valley type are thought to have formed through the migration of warm (50 degrees -150 degrees C) subsurface fluids in sedimentary basins. The fundamental role of fluid flow is poorly understood; depending on the stage of evolution of a basin, either a compaction-drive or gravity-drive fluid-flow system may be developed. Quantitative examination of the role of one flow mechanism in ore genesis; gravity-driven groundwater flow. Equations governing fluid flow, heat transport, mass transport, and geochemical mass transfer. Numerical modeling techniques are used to develop a computer code for simulation of regional transport processes along cross sections. The finite-element method is applied to solve the steady-state, fluid-flow, and heat-transport equations, and a moving-particle random-walk algorithm is developed to predict the advection and dispersion of aqueous species.--Modified journal abstract.

The Effect of Tortuosity on Fluid Flow Through a Single Fracture

Abstract: Calculations to investigate the effect of path tortuosity and connectivity on fluid flow rate through a single rough fracture were carried out. The flow paths are represented by electrical resistors placed on a two-dimensional grid, and the resistances vary as the inverse of the fracture aperture cubed. The electric current through the circuit bears a one-to-one correspondence to the fluid flow rate. Both fracture apertures derived from measurements and from hypothetical analytic functions were used in a parameter study to investigate the dependence of tortuosity on fracture roughness characteristics. It was found that the more small apertures there are in the aperture distribution, the larger is the effect of tortuosity. When the fraction of contact area between the fracture surfaces rises above 30%, the aperture distributions are invariably large at small apertures, and the effect of fracture roughness and flow path tortuosity depresses flow rate from the value predicted by the parallel plate representation of a fracture by three or more orders of magnitude. The impact of these results on the calculations and measurements in fracture hydrology is discussed.

A two-dimensional transient model for convection in laser melted pool

Abstract: A two-dimensional transient model for convective heat transfer and surface tension driven fluid flow is developed. The model describes the transient behavior of the heat transfer process of a stationary band source. Semi-quantitative understanding of scanning is obtained by a coordinate transformation. The non-dimensional forms of the equations are derived and four dimensionless parameters are identified, namely, Peclet number (Pe), Prandtl number (Pr), surface tension number(S), and dimensionless melting temperature(@#@ Tm * @#@). Their governing characteristics and their effects on pool shape, cooling rate, velocity field, and solute redistribution are discussed. A numerical solution is obtained and presented. Quantitative effects of Prandtl number and surface tension number on surface velocity, surface temperature, pool shape, and cooling rate are presented graphically.

The generation and decay of vorticity

Abstract: Vorticity, although not the primary variable of fluid dynamics, is an important derived variable playing both mathematical and physical roles in the solution and understanding of problems. The following treatment discusses the generation of vorticity at rigid boundaries and its subsequent decay. It is intended to provide a consistent and very broadly applicable framework within which a wide range of questions can be answered explicitly. The rate of generation of vorticity is shown to be the relative tangential acceleration of fluid and boundary without taking viscosity into account and the generating mechanism therefore involves the tangential pressure gradient within the fluid and the external acceleration of the boundary only. The mechanism is inviscid in nature and independent of the no-slip condition at the boundary, although viscous diffusion acts immediately after generation to spread vorticity outward from boundaries. Vorticity diffuses neither out of boundaries nor into them, and the only...

Modelling fluid flow in fractured‐porous rock masses by finite‐element techniques

Abstract: One of the major difficulties of modeling fluid flow processes in hard-rock geologies is the complex nature of the porosity systems. Hydraulic behavior in these rock masses is characterized by both porous and fractured interflow zones. Traditionally, fractured-porous rocks have been modeled as an equivalent porous medium or as a system of fractures separated by impermeable blocks. A new method is proposed that unifies these two approaches for modeling fluid flow processes in fractured-porous media. The basic idea is to use a combination of isoparametric elements for the porous zones and line elements for the fractures. The coupling between the governing equations for each element type is achieved using the superposition principle. The effectiveness of the new approach is demonstrated by comparing numerical solutions with known solutions for problems of flow and solute transport in fractured-porous media.

Visualization Studies of a Shear Driven Three-Dimensional Recirculating Flow

Abstract: A facility has been constructed to study shear-driven, recirculating flows. In this particular study, the circulation cell structure in the lid-driven cavity was studied as a function of the speed of the lid which provides the shearing force to a constant and uniform density fluid. The flow is three-dimensional and exhibits regions where Taylor-type instabilities and Taylor Goertler-like vortices are present. One main circulation cell and three secondary cells are present for the Reynolds number (based on cavity width and lid speed) range considered, viz., 1000-10000. The flows becomes turbulent at Reynolds numbers between 6000 to 8000. The transverse fluid motions (in the direction perpendicular to the lid motion) are significant. In spite of this, some key results from two-dimensional numerical simulations agree well with the results of the present cavity experiments.

Heat- and fluid-flow phenomena in weld pools

Abstract: A mathematical formulation is presented for the transient development of the fluid-flow field and the temperature field in a liquid pool, generated by a spatially variable heat flux falling on an initially solid metal block. This physical situation is an idealized representation of a TIG (tungsten-inert-gas) welding process. In the formulation allowance is made for electromagnetic, buoyancy and surface forces and the resultant equations are solved numerically.It is found that both the convective flow field and the temperature field are markedly affected by the nature of the heat flux and the flux of electric current falling on the free surface.In the absence of surface-tension effects a broadly distributed heat flux and corresponding current distribution cause a situation where both electromagnetic and buoyancy forces are important in determining the fluid-flow field; however, in these systems the fluid-flow field does not play a significant role in defining the heat-transfer process. In contrast, a sharply focused heat flux and current density on the free surface give rise to strong electromagnetically driven flows, which play an important role in determining the shape of the weld pool.Calculations are also done exploring the effect of surface-tension-driven flows. It is found that surface-tension gradients may produce quite high surface velocities and can have a profound effect on determining the weld-pool shape.

On the decay of solutions to the linearized equations of electro-magneto-fluid dynamics

Abstract: The linearized equations of the electrically conducting compressible viscous fluids are studied. It is shown that the decay estimate (1+t)−3/4 inL 2(R 3) holds for solutions of the above equations, provided that the initial data are inL 2(R 3)∩L 1(R 3). Since the systems of equations are not rotationally invariant, the perturbation theory for one parameter family of matrices is not useful enough to derive the above result. Therefore, by exploiting an energy method, we show that the decay estimate holds for the solutions of a general class of equations of symmetric hyperbolic-parabolic type, which contains the linearized equations in both electro-magneto-fluid dynamics and magnetohydrodynamics.

Richardson number criterion for the nonlinear stability of three-dimensional stratified flow

Abstract: With use of a method of Arnol'd, we derive the necessary and sufficient conditions for the formal stability of a parallel shear flow in a three-dimensional stratified fluid. When the local Richardson number defined with respect to density variations is everywhere greater than unity, the equilibrium is formally stable under nonlinear pertrubations. The essential physical content of the nonlinear stability result is that the total energy acts as a "potential well" for deformations of the fluid across constant density surfaces; this well is required to have definite curvature to assure stability under these deformations.

Laboratory studies of volcanic jets

Abstract: The study of the fluid dynamics of violent volcanic eruptions by laboratory experiment is described, and the important fluid-dynamic processes that can be examined in laboratory models are discussed in detail. In preliminary experiments, pure gases are erupted from small reservoirs. The gases used are Freon 12 and Freon 22, two gases of high molecular weight and high density that are good analogs of heavy and particulate-laden volcanic gases; nitrogen, a moderate molecular weight, moderate density gas for which the thermodynamic properties are well known; and helium, a low molecular weight, lowdensity gas that is used as a basis for comparison with the behavior of the heavier gases and as an analog of steam, the gas that dominates many volcanic eruptions. Transient jets erupt from the reservoir into the laboratory upon rupture of a thin diaphragm at the exit of a convergent nozzle. The gas accelerates from rest in the reservoir to high velocity in the jet. Reservoir pressures and geometries are such that the fluid velocity in the jets is initially supersonic and later decays to subsonic. The measured reservoir pressure decreases as the fluid expands through repetitively reflecting rarefaction waves, but for the conditions of these experiments, a simple steady-discharge model is sufficient to explain the pressure decay and to predict the duration of the flow. Density variations in the flow field have been visualized with schlieren and shadowgraph photography. The observed structure of the jet is correlated with the measured pressure history. The starting vortex generated when the diaphragm ruptures becomes the head of the jet. Though the exit velocity is sonic, the flow head in the helium jet decelerates to about one-third of sonic velocity in the first few nozzle diameters, the nitrogen head decelerates to about three-fourths of sonic velocity, while Freon maintains nearly sonic velocity. The impulsive acceleration of reservoir fluid into the surrounding atmosphere produces a compression wave. The strength of this wave depends primarily on the sound speed of the fluid in the reservoir but also, secondarily with opposite effect, on the density: helium produces a relatively strong atmospheric shock while the Freons do not produce any optically observable wave front. Well-formed N waves are detected with a microphone far from the reservoir. Barrel shocks, Mach disks, and other familiar features of steady underexpanded supersonic jets form inside the jet almost immediately after passage of the flow head. These features are maintained until the pressure in the reservoir decays to sonic conditions. At low pressures the jets are relatively structureless. Gas-particle jets from volcanic eruptions may behave as pseudogases if particle concentrations and mass and momentum exchange between the components are sufficiently small. The sound speed of volcanic pseudogases can be as large as 1000 m s^(−1) or as small as a few tens of meters per second depending on the mass loading and initial temperature. Fluids of high sound speed produce stronger atmospheric shock waves than do those of low sound speed. Therefore eruption of a hot gas lightly laden with particulates should produce a stronger shock than eruption of a cooler or heavily laden fluid. An empirical expression suggests that the initial velocity of the head of supersonic volcanic jets is controlled by the sound speed and the ratio of the density of the erupting fluid to that of the atmosphere. The duration of gas or pseudogas eruptions is controlled by the sound speed of the fluid and the ratio of reservoir volume to vent area.

Modern Optical Techniques in Fluid Mechanics

Abstract: Optical techniques are widely used in fluid mechanics to observe and measure properties of flow fields such as velocities or densities. Many of these techniques are qualitative but of great value in guiding intuition for further research by quantitative means. Beautiful examples can be seen in the Album of Fluid Motion (Van Dyke 1982). Optical techniques are usually known for their largely nonintrusive properties as compared with methods like the Pitot tube or the hot-wire technique. The last few years, however, have seen some examples where light has been used not only to probe fluid flows but to generate them (Lauterborn 1980). This gives rise to a new classification of optical techniques in fluid mechanics (see Figure 1). Flow­ visualization techniques use light as an information carrier where the information is impressed on the light beam by the fluid flow. Flow­ generation techniques use light as an energy carrier to initiate fluid flow by radiation pressure, heating, or optical breakdown. Flow-visualization techniques may be coarsely subdivided into two categories: those that make use of light scattered by tiny particles in the fluid and those that make use of variations in refractive index. Among the methods that rely on scattered light, laser Doppler anemometry is now a standard means of obtaining fluid velocities. This method and its various refinements are well documented (Durst et al. 1976, Durrani & Greated 1977, Drain 1980, Schulz-DuBois 1983) and are not discussed here. In laser Doppler anemometry, the fluid velocity can be measured with high accuracy as a function of time but only at a single point in the fluid at any given time. The ultimate aim, of course, is the simultaneous determination of fluid velocities in a whole volume of a fluid. First steps in this direction

Hyperbolicity and change of type in the flow of viscoelastic fluids. Technical summary report

Abstract: The equations governing the flow of viscoelastic liquids are classified according to the symbol of their differential operators. Propagation of singularities is discussed and conditions for a change of type are investigated. The vorticity equation for steady flow can change type when a critical condition involving speed and stresses is satisfied. This leads to a partitioning of the field of flow into subcritical and supercritical regions, as in the problem of transonic flow.

Analysis and Control of Unsteady Flow in Pipelines

Abstract: Note: An Ann Arbor sciencebook Reference Record created on 2004-09-07, modified on 2016-08-08

Flow development in a porous channel and tube

Abstract: The spatial development of the inlet velocity profile in a uniformly porous channel and tube is investigated. For tubes which are very long compared with their radius, it is shown that above a critical Reynolds number of 2.3 the inlet velocity profile does not necessarily decay into the fully developed, similarity profile for an infinite tube. Rather, the structure of the flow throughout the entire tube is influenced by the inlet profile. This loss of validity of the similarity solution is due to the fact that the tube is of finite length and the inlet profile is not of the similarity form. The actual length of the tube is, however, unimportant. Analogous results hold for the flow in a porous channel, with a critical Reynolds number of approximately 6.

Front tracking for gas dynamics

Abstract: Front tracking is an adaptive computational method in which a lower dimensional moving grid is fitted to and follows the dynamical evolution of distinguished waves in a fluid flow. The method takes advantage of known analytic solutions, derived from the Rankine-Hugoniot relations, for idealized discontinuities. In this paper the method is applied to the Euler equations describing compressible gas dynamics. The main thrust here is validation of the front tracking method: we present results on a series of test problems for which comparison answers can be obtained by independent methods.