Showing papers on "Fluid dynamics published in 1971"

Mechanism of bond zone wave formation in explosion-clad metals

Abstract: Results of experiments in which the collision variables were carefully controlled showed that bond zone wave formation during explosion cladding is analogous to the formation of vortex streets in fluid flow around an obstacle or in the collision of liquid streams. The fluid flow analogy explains the observed transition from a smooth metal-to-metal bond zone to a wavy bond zone above a critical collision velocity. This model is capable of predicting the minimum collision velocity necessary for bond zone wave formation in different metal systems and it also predicts correctly the strong dependence of wave size on collision angle. The magnitude of the wave size agrees with that predicted from fluid flow past a flat plate. Two other mechanisms of bond zone wave formation were explored experimentally and found to be invalid.

Suspended Particles in Fluid Flow Through Tubes

Abstract: Interesting modes of behavior are exhibited by particles suspended in a fluid that is flowing through a tube. The phenomena are important in many branches of science and technology, such as the flow of dissolved macro­ molecules, of fiber suspensions in paper making, of latex particles in emulsion paints, of leinforcing particles in polymer melts, of rock crystals in molten lavas and red cells and other bodies in blood, to cite a few examples in diverse fields. In this review, the behavior of particles flowing through tubes of circular cross section will be discussed; because of space limitations no mention will be made of the widespread application of the principles that are considered. It will be assumed, unless otherwise stated, that the suspending fluid, which may be either liquid or gas, is Newtonian so that the velocity u and pressure p within it satisfy the Navier-Stokes and continuity equations. The particles themselves, however, will be assumed to consist either of solid material or of drops or bubbles of a fluid immiscible with the suspending medium. Two important parameters in these circumstances are the flow Reynolds number Ret defined by

An experimental study of peristaltic pumping

Abstract: An apparatus that approximates a two-dimensional, infinite train of peristaltic waves yields measurements of mean flow, of mean pressure rise, and of pressure-time pulses at fixed locations. In addition, visual observations of ‘reflux’ and ‘trapping’, using dyed fluid, are shown. The inertia-free range extends up to a Reynolds number of about 1. In this range, the theory of Shapiro, Jaffrin & Weinberg (1969) is confirmed with respect to mean pressure vs. mean flow, pressure vs. time, reflux, and trapping. The controversy regarding the criterion of material reflux is settled in favour of the Lagrangian time-mean velocity rather than the Eulerian time-mean velocity. Experiments at higher Reynolds numbers show that the second-order expansion theory of Jaffrin (1971) is valid up to a Reynolds number of about 10.

NMR Spin‐Echo Flow Measurements

Abstract: Patterns of fluid flow are investigated by a technique utilizing NMR spin echoes. Spin‐echo amplitudes are sensitive to the phase distribution of the resonating nuclei in the fluid, and the phase distribution is dependent upon the flow. A mathematical transformation of the spin‐echo amplitudes observed provides a velocity distribution function which indicates the relative number of molecules flowing in any given velocity range when plotted. Experimental data are obtained from ordinary laminar flow, and blood flow in human fingers.

A Laboratory Investigation of Miscible Displacement by Carbon Dioxide

Abstract: Displacements of reconstituted reservoir fluids in Boise outcrop sandstone cores of 6 to 42.5 ft in length using COD2U at various pressures were conducted. The studies indicate that a miscible displacement may be achieved by COD2U injection at pressures well below those necessary when methane is the injection fluid. Miscibility by COD2U is generated through multiple contact equilibria in which the COD2U is progressively enriched with intermediates (ethane through hexane) from the oil. The miscibility pressure for COD2U and a given reservoir fluid is difficult to determine, because COD2U exhibits highly efficient swelling and vaporization of the oil. Also it was found to be impractical to operate below the rates where differences in density between displaced and displacing fluids prevent viscous fingering in vertical cores. The miscibility pressure was defined using the anticipated increasing recovery as a function of core length in miscible displacements in combination with effluent fluid visual cell observations and chromatographic data. (23 refs.)

Jet Turbulence Dissipation Rate Measurements and Correlations

Abstract: : The rate of viscous dissipation in a turbulent jet is examined in some detail. A correlation of the mean rate of dissipation on the center-line in terms of the orifice Reynolds number and axial position is established. Measurements of the velocity and velocity derivative are described for a jet with an orifice Reynolds number of 120000. The spectrum of the square of the velocity derivative was examined for similarity to those obtained for atmospheric boundary layer flows at very large Reynolds numbers when normalized with Kolmogoroff length and time scales. Spectra of higher order moments of the velocity derivative are also presented and compared to Novikov's predictions of the power law subranges. (Author)

Magneto-fluid-mechanic pipe flow in a transverse magnetic field. Part 1. Isothermal flow

Abstract: An experimental investigation was conducted in a circular pipe to examine the influence of a transverse magnetic field on the structure of turbulent shear flow of a conducting fluid (mercury). In the present paper, part 1, mean velocity profiles, turbulence intensity profiles, velocity fluctuation spectra, axial pressure drop profiles, and skin friction data are presented which quantitatively exhibit the Hartmann effect and damping of the velocity fluctuations over a broad range of Reynolds numbers and magnetic fields. The results of heat transfer experiments will be reported by the authors in the following paper, part 2.

Light valve with flowing fluid suspension

Abstract: A light valve having a cell containing a fluid suspension of minute particles dispersed therein capable of orientation by an electric or magnetic field to change the transmission of light through the suspension, and means for applying such a field thereto, includes circulating means for producing a flow of the fluid suspension through the cell during operation thereof to reduce or avoid agglomeration of the particles. Various means are described for producing a smooth generally laminar flow of the fluid suspension in the active region of the cell. The circulating means may include means for dispensing agglomerated particles which may be produced during cell operation. A sheet for polarizing material in the path of light from the valve, with its direction of polarization perpendicular to fluid flow in the cell, markedly increases the closing speed. Two valves with fluid flow at right angles increases the closing speed without seriously decreasing the density ratio between closed and open states.

Propagation of Sound through a Variable‐Area Duct with a Steady Compressible Flow

Abstract: The equations governing the progagation of sound in a nonconstant area duct with a one‐dimensional fluid flow are derived by a linearizing perturbation technique. The governing equations are transformed successively into two decoupled linear ordinary differential equations with a variable coefficient. By the appropriate choice of duct shape, the variable coefficient is made constant. The duct shape chosen is semi‐infinite, diverging from the sonic throat. Solutions are obtained for several choices of the parameter ωL/2as, which relates frequency, duct shape, and speed of sound. The solutions exhibit standing‐wave characteristics and reveal certain aspects of energy transfer between the mean flow and sound. The study bears on noise growth and decay in the input and output ducts of certain fluidic amplifiers.

Measurement of fluid flow rates

Abstract: Apparatus and a method for measuring the flow rate of a fluid in which a beam of ultrasonic ≮, electromagnetic, optical or other radiant.]. energy is transmitted across the flow at each of two positions spaced apart in the direction of flow, the noise amplitude, frequency or phase modulation on each beam due to disturbances in the flow is detected, and the two resultant signals are cross correlated to determine the time delay therebetween producing maximum correlation, i.e. the mean fluid transport time between the beams, and thus the mean fluid flow rate.

Theoretical analysis of the turbulent flow of non‐newtonian slurries in pipes

Abstract: A theoretical model is derived which permits the analytical calculation of the friction factor-Reynolds number curves for non-Newtonian slurries flowing isothermally in smooth pipes. This model is based upon the Bingham plastic rheological equation of state. A change of mechanism in the transition phenomenon is observed to occur for N/sub He/ = 5 (10/sup 5/), where N/sub He/ is the familiar Hedstrom number. Below this value turbulence is suppressed relative to Newtonian flow, while above this value the transition is delayed but turbulence is enhanced relative to Newtonian flow. A set of theoretical design curves of friction factor versus Reynolds number covering laminar, transitional, and turbulent flows is calculated and presented for a range of N/sub He/ values from 10/sup 3/ to 10/sup 9/.

Stability and convergence in fluid flow problems

Abstract: The general convergence and stability theory for finite-difference approximations to fluid flow problems is described. The methods of analysis are outlined and applied to a typical problem. Simple models are then used to consider the behaviour of common difference schemes under practical conditions of finite mesh intervals. Practical stability limits, mode propagation and conservation properties, and nonlinear instabilities are particular characteristics considered. The leapfrog method when used with appropriate safeguards emerges as the most generally suitable basic method.

Slow steady flows of a conducting fluid at large Hartmann numbers

Abstract: We consider slow steady flows of a conducting fluid at large values of the Hartmann number and small values of the magnetic Reynolds number in an inhomogeneous magnetic field. The general solution is obtained in explicit form for the basic portion (core) of the flow, where the inertia and viscous forces may be neglected. The boundary conditions which this solution must satisfy at the outer edges of the boundary layers which develop at the walls are considered. Possible types of discontinuity surfaces and other singularities in the flow core are examined. An exact solution is obtained for the problem of conducting fluid flow in a tube of arbitrary section in an inhomogeneous magnetic field. The content of this paper is a generalization of some results on flows in a homogeneous magnetic field, obtained in [1–8], to the case of arbitrary flows in an inhomogeneous magnetic field. The author's interest in the problems considered in this study was attracted by a report presented by Professor Shercliff at the Institute of Mechanics, Moscow State University, in May 1967, on the studies of English scientists on conducting fluid flows in a strong uniform magnetic field.

Hydromagnetic flow in a rotating channel

Abstract: The steady flow in a parallel plate channel rotating with an angular velocity Ω and subjected to a constant transverse magnetic field is analysed. An exact solution of the governing equations is obtained. The solution in the dimensionless form contains two parameters: the Hartmann number, M2, and K2 which is the reciprocal of the Ekman number. The effects of these parameters on the velocity and magnetic field distributions are studied. For large values of the parameters, there arise thin boundary layers on the walls of the channel.

Equations of motion and continuity for fluid flow in a porous medium

Abstract: This paper is devoted to a rigorous derivation of the fundamental laws governing the macroscopic flow of fluids in a porous medium. The derivation is given within the framework of classical continuum mechanics and the resulting equations contain the continuity equation and the Euler equations of motion of hydrodynamics as well as Darcy's law as special cases.

Flows and Wave Propagation in Ferrofluids

Abstract: The dynamic behavior of magnetically polarizable fluids (ferrofluids) is considered in two instances differing in the dependence of the fluid magnetization on temperature. When the magnetization can be regarded as temperature independent, the influence of the magnetic field on the force distribution acting on a submerged body is demonstrated, the flow pattern of the associated ordinary fluid dynamics problem remaining unaffected. In the other instance, when the temperature dependence of the magnetization must be considered, the question of thermal stability of the ferrofluid is considered and the appropriate magnetic Rayleigh number and its influence are determined. Furthermore, it is shown that small disturbances in a ferrofluid are quickly damped so that vorticity generated by the thermomagnetic interaction for such disturbances does not propagate.

Stable Numerical Integration of Conservation Equations for Hydraulic Networks

Abstract: Hydraulic-network models have been used to study transient flow phenomena in pressurized water reactor plants. The nature of the differential equations associated with these networks imposes severe...

Thermo-Fluid Dynamics of Separated Two-Phase Flow.

Abstract: : A general thermo-fluid dynamic formulation of separated two-phase flow has been provided and used for the analysis of various dynamic aspects of the film flow regime. The conservation equations which are expressed both in terms of the two-fluid model and of the diffusional, i.e., drift, model were derived from the space averaging procedure and take into account the effects of surface phenomena such as surface tension and surface shear and of surface processes such as momentum, heat and mass transfer at the interface. These equations were then used to establish the similarity groups appropriate to separated flows.

Flap-equipped power fluid amplifier

Abstract: A fluid amplifier having a fluid flow inlet, a pair of fluid flow outlets, a control fluid flow inlet and a pivotable triangular flap member located in the branching point of the fluid flow outlets, said member being located downstream of the control fluid inlet and adapted to open either of said fluid flow outlets. The flap member is free from direct actuation by the control fluid but is actuated by the fluid flow guided into either outlet and is pivotably journalled about an axis located within the triangular contour, whereby the flap member is automatically switched over to a position with the selected active outlet opened and the other passive outlet completely closed.

Flow measurement and control

Abstract: A device for controlling fluid flow in accordance with measured flow. A housing with a passage therethrough is provided internally with movable control members and control means therefor extending externally of the housing to thus define a variable venturi or variable flow nozzle for controllably restricting fluid flow through the passage. A pair of apertures in the housing communicating with the passage, one at or near the throat of the venturi or flow nozzle and one upstream thereof, are adapted for connection to a differential pressure indicating means, which may also include recording and controlling functions. A capacity curve is employed with the indicated differential pressure to determine the proper throat opening for any desired fluid flow.

Stagnation point flow of a second-order viscoelastic fluid

Abstract: The boundary-layer equations are solved for the case of two-dimensional flow of a second-order viscoelastic fluid near a stagnation point. It is shown that the effect of viscoelasticity is not only to increase the wall-shear stress but also to cause oscillations in the velocity profile. It is further shown that the constitutive equation for the second-order viscoelastic fluid is not applicable to the analysis of stagnation point flow for Weissenberg numbers greater than approximately 0.32.