Chemical Engineering Commons^™

Optimization Of An Lda System, Robert Smid

Symposia on Turbulence in Liquids

This paper discusses the various considerations leading to the optimization of a laser Doppler anemometer for measurements in the flows of gases, liquids, and solids. The requirements placed on the various parameters of the optics by the experiment are discussed in general for different modes of operation. Expressions determining these optical parameters in certain instances given by various authorities are presented and compared. This includes such topics as: laser power, particle size, measuring volume size, optical variation in transmitting and receiving optics, and photodetector selection.

Phase Separation In Turbulent Two-Phase Flow, Francois J. Resch, Hans J. Leutheusser

Symposia on Turbulence in Liquids

The paper is based on an experimental study of a typical instance of bubbly two-phase flow, viz. the air-entraining roller zone of hydraulic jumps in open channels. The investigation was undertaken with the aid of hot-film anemometry techniques involving instant digitization of analog signals, and delayed electronic processing of the tape-recorded data. Special computer programs were designed to separate the two phases according to a well-defined signal threshold. It is this aspect of the work which is being dealt with in the paper.

Turbulent Characteristics Of Two-Phase, Gas-Liquid Stratified Channel Flow, D. M. Johns, T. G. Theofanous, R. N. Houze

Symposia on Turbulence in Liquids

The turbulence characteristics of the bulk phases were studied in a stratified, two-dimensional, gas- liquid channel flow. Initial results are presented comparing mean velocity and turbulent intensity profiles with those obtained in a prior study at the same bulk phase Reynolds numbers. The results indicate that comparison of two realizations of stratified gas- liquid flow cannot be adequately done on the basis of bulk-phase Reynolds numbers. Comparisons must be based on some more fundamental relationships involving the gas-liquid interactions.

Experimental Measurement Of Particle Dispersion In Turbulent Flow, N. M. Howard, C. C. Meek, B. G. Jones

Symposia on Turbulence in Liquids

The dispersion of particles in turbulent flows, phenomena such as dispersion, diffusion, and sedimentation, and a more fundamental point of view, the description of particle interaction with the turbulent field are recently of increasing interest. A system capable of investigating statistical structure of the motion of particles in a turbulent fluid flow using a turbulent water pipe flow system and particles tagged with C0-60 radioactive pellets has been constructed and tested. The particles were followed in their trajectory by a group of detectors consisting of NaI(Tℓ) crystals mounted on photomultiplier tubes which move with the particles on a movable carriage. …

Conditioned Sampling Techniques, R. E. Kaplan

Symposia on Turbulence in Liquids

The concept of organized, spatially coherent large scale structures has been investigated for a variety of turbulent shear flows by a technique called "Conditional Sampling." It can be shown that these structures are related to physically important activities such as, 1) the entrainment of turbulent boundary layers, and 2) the maintenance of turbulence by a wall, 3) the growth of free shear layers, and 4) the structure and noise production of turbulent jets.

The general technique of conditioned sampling is related to visualizations of the flow, and to problems of synchronization of images in the presence of noise. While there …

A Comparison And Analysis Of Detection Methods For The Measurement Of Production In A Boundary Layer, G. R. Offen, S. J. Kline

Symposia on Turbulence in Liquids

Two hot films and dye visualizations have been employed, simultaneously, in a turbulent boundary layer to explore the relations among visual observations and five kinds of detection methods using conditional sampling. The results show that all methods correlate positively with each other, but not with high enough values of correlation coefficients to indicate true correspondence between any two thus far studied. Moreover, none of the detection methods devised to date indicate a plateau in number of events as a function of trigger threshold.

The results also provide additional information on several other matters: (i) the relationship of outward motions from …

On The Interpretation Of The Output Of Hot-Film Anemometers And A Scheme Of Dynamic Compensation For Water Temperature Variation, J. Tan-Atichat, H. M. Nagib, J. W. Pluister

Symposia on Turbulence in Liquids

Using a special calibration tunnel developed during the course of this study, the static and dynamic response of several kinds of commercially available hot-film probes with single and multiple sensors of the cylindrical-fiber type are examined. The effects of different parameters, including those of the anemometer bridge, on the output and performance of the probes are evaluated. In particular, the consequences of variations in water temperature on the hot-film anemometer output are determined. The results reveal a large effect of the water temperature on the calibration curves (in an extreme case a change in temperature of only 5.5°F can result …

An Experimental And Theoretical Study Of The Viscous Sublayer For Turbulent Tube Flow, Lindon C. Thomas, H. L. Greene

Symposia on Turbulence in Liquids

Flush-mounted anemometer probes have been used to further study characteristics of the viscous sublayer for both Newtonian and drag reducing solutions, with particular emphasis given to low Reynolds number turbulent tube flow. Experimental measurements for the mean frequency of bursting or renewal within the wall region are compared with theoretical predictions obtained on the basis of the surface renewal and penetration model.

Both theory and experiment taken together suggest that the effect of the mean axial pressure gradient on the viscous sublayer becomes important for the deeper molecular penetration associated with low Reynolds number flow. Also, a pronounced lessening of …

Front Matter, University Of Missouri--Rolla

Symposia on Turbulence in Liquids

No abstract provided.

Current Investigations Of Turbulent Shear, S. J. Kline, G. R. Offen, W. C. Reynolds

Symposia on Turbulence in Liquids

The paper covers first a short review of the history of research on turbulent shear and second a description of current experiments which may lead to further understanding.

The first portion categorizes the kinds of data which have been taken and discusses what can be learned from each. It then summarizes what is firmly established concerning the nature of turbulent shear, mostly from work of the past decade. A description of the several interpretations of these data under theoretic study by current leading researchers is then given.

The second portion of the paper discusses the extraordinarily difficult problem of identifying …

Interpretation Of Hot-Film Anemometer Response In A Non-Isothermal Field, W. E. Burchill, B. G. Jones

Symposia on Turbulence in Liquids

A new technique for interpretation of hot-film anemometer sensor response is described. This technique has been applied to simultaneous measurement of profiles of mean velocity, the three components of velocity vector fluctuation, and temperature fluctuation in non-isothermal pipe flow of water using multiple sensors. Sensors operated in the constant temperature mode (CTA) respond to both mean and fluctuating velocity and temperature. The influence of mean temperature gradient on CTA sensor response was eliminated by appropriate adjustment of the sensors' operating resistances as the temperature gradient was traversed. The adjustments were derived from analysis of linearized CTA sensor response. A sensor …

Near Wall Visual Measurements In Drag Reducing Flow, H. C. Hershey

Symposia on Turbulence in Liquids

A review of several explanations for the mechanisms of drag reduction is presented. Visual studies of ordinary liquids are reviewed briefly, and visual studies in drag reducing flow are discussed. Finally, current work at Ohio State University is described where high speed motion pictures will be taken of drag reducing flow using the technique of Brodkey and Corino.

Energy Relations For Turbulent Flow In Routh Pipes, H. W. Townes

Symposia on Turbulence in Liquids

This paper describes the results of an experimental and analytical study of turbulent flow in rough pipes. Appropriate forms of mean and turbulence energy balances were developed by including mean radial and angular velocity components and using a spatial averaging technique in addition to the normal time average. An experimental program was then devised for determining the various terms in these equations. The quantities measured included the longitudinal mean velocity, rms values of fluctuating velocity components in the 3 coordinate directions, second and third order correlations between fluctuating velocities, and various components of the dissipation function. All of these quantities …

Correlation And Statistical Characteristics Of Turbulence Fronts In The Wakes Of Hypervelocity Bodies, R. H. Howell, J. L. French

Symposia on Turbulence in Liquids

Data on statistical wake turbulence of the far wake of sphere and cone models with velocities from 9,800 to 21,500 feet/second and range pressures from 50 to 120 mm Hg. are presented and analyzed. The measurement technique used is that of observing the turbulence edge position of the wake on schlieren films. The measured parameters are the wake width; edge roughness; auto-correlation function; microscale; e-fold; integral, and average eddy lengths; wake dissipation parameter; Kolmogoroff and energy containing wave number parameters; Lagrangian integral time scale parameter; Strouhal number; cross-correlation function; and wake edge velocity. The results of these measurements are compared …

Turbulence Measurements Using The Laser Doppler Velocimeter, J. W. Dunning, N. S. Berman

Symposia on Turbulence in Liquids

Although the laser Doppler velocimeter has been used for turbulence measurements in the past, no set of measurements in practical turbulent flows has been available to evaluate the instrument. In this work we examine in detail the photomultiplier signal representing the axial velocity of water within a glass pipe. We show that with proper analysis of the photomultiplier signal, the turbulent information that can be obtained in liquid flows is equivalent to recent hot-film studies. In shear flows the signal from the laser Doppler velocimeter contains additional information which may be related to the average shear.

Turbulence Measurements With The Split-Film Anemometer Probe, B. W. Spencer, B. G. Jones

Symposia on Turbulence in Liquids

The newly developed split-film anemometer probe, manufactured by Thermo- Systems, Inc. of St. Paul, Minnesota, has been applied to the measurement of two-dimensional turbulence characteristics, including turbulent shear stress, in mixing layer and boundary layer shear flows. Probes of both 6-mil and 2- mil diameters were used which had the same physical dimensions as ordinary hot-film anemometer probes. The film on this sensor is split into two 170° elements resulting in two independent sensors. This enables the probe to detect vertical as well as axial components of the instantaneous velocity vector. It therefore serves the same purpose as an x-probe, …

On Velocity Measurements In Non-Isothermal Turbulent Flows, R. Chevray, N. K. Tutu

Symposia on Turbulence in Liquids

Turbulent velocity measurements in non-isothermal flows are conventionally performed by constant current hot-wire anemometry. The procedure involved however is cumbersome, the output signals are nonlinear and more critically a continuous signal of velocity fluctuations is not provided. The method described here utilizes two orthogonal wires situated a fraction of a millimeter apart. The upstream wire is operated in a low overheat, constant-current compensated mode thus providing a signal proportional to temperature while the down-stream wire, practically unaffected by the thermal wake of the first wire is operated in the constant temperature mode. Compensation for the effects of local temperature on …

Boundary Pressure Fluctuations Due To Macroturbulence In Hydraulic Jumps, F. R. Schiebe, C. E. Bowers

Symposia on Turbulence in Liquids

Data concerning the statistical properties of pressure fluctuations on the containment structure associated with the hydraulic jump have been studied at the St. Anthony Falls Hydraulic Laboratory. The incident Froude numbers were investigated through the practical range from 4 to 9. The mean square of the fluctuating pressure, the mean pressure, and the power spectrum were determined as a function of position under the jump. In addition, mean and rms turbulent velocity profiles and entrained air concentration profiles throughout the jump volume were determined.

The principal tests were performed in a channel 20 inches wide and 3 feet deep. Other …

A Proposed Interpretation Of Transitional And Turbulent Energy Flow Processes, J. N. Cannon, R. W. Hanks

Symposia on Turbulence in Liquids

This paper discusses the consequence of a continuum analysis of turbulence using the Reynolds convention, on the cascade of energy to internal thermal energy. It is observed that there are two distinct dissipative paths or traps that the energy follows, neither of which involves vorticity. It is observed that the so-called "Reynolds' Stresses" are not involved in these irreversible dissipative paths, but are in the reversible bridge between the mean and fluctuating flows.

An effort is made to generate a consistent physical interpretation of all of the terms in the equations used rather than selecting isolated terms for explanation. Some …

Dissipation Of An Axially Symmetric Turbulent Wake In The Very Far Field, R. H. Waser

Symposia on Turbulence in Liquids

A wake visualization technique has been used to observe the turbulent wake at distances of 10⁶ diameters behind an axially symmetric streamlined body traveling submerged in water. It has been found that a transition occurs in the rate of wake growth between 10⁴ and 10⁵ diameters which is attributed to a "reverse transition" from turbulent to laminar flow.

The wake visualization technique involves dropping a dye-coated body down a taut vertical guide wire into a large water-filled tank. Measurement of the wake growth and dissipation is made from a time series of photographs.

The bodies tested were …

Author Index, University Of Missouri--Rolla

Symposia on Turbulence in Liquids

No abstract provided.

Turbulent Interface Detector Using A Multiple Array Of Single Hot Wires, W. H. Schwarz

Symposia on Turbulence in Liquids

Intermittency circuits can be used to experimentally determine some of the properties of the turbulent interface that occur in turbulent shear flows. The signal I(x,t) is unity if turbulence is present at x and zero otherwise. Using the signals obtained from detectors at one or more points, certain statistical measures of the interface position Y(x,t) can be determined. Also using a linear array of conventional single hot-wire probes, the position of the interface can be detected continuously to within some small error. The intent of this h-detector is similar to the wave-height detector used in studies of sea surfaces. The …

Experiments In Magneto-Fluid-Mechanic Natural And Forced Heat Transfer From Horizontal Hot-Film Probes, P. F. Dunn, P. S. Lykoudis

Symposia on Turbulence in Liquids

Experiments investigating magneto-fluid-mechanic effects on the heat transfer of quartz-coated hot-film probes are described. A standard heat transfer-velocity calibration curve is obtained by traversing a probe, whose axis is aligned horizontally, in the presence of a magnetic field parallel to the probe's axis. The working medium is mercury. Results indicate a significant reduction of the probe1s heat transfer in both the free and forced convection regimes.

The Unpolarized Electrode In A Pulsating Poiseuille Pipe Flow, B. M. Bergmann, T. H. Hodgson

Symposia on Turbulence in Liquids

In recent years three workers have described methods of measurement of unsteady flow quantities in water using unpolarized electrodes. Both Binder and Chuang have attempted measurements of turbulent velocity fluctuations, whereas Dumargue described a method of fluctuating pressure measurement.

In this paper, analysis and experiment were used to critically compare the previous workers' experiments. From measurements in an oscillating Poiseuille pipe flow it is concluded that an electrode positioned in the wall detects a signal with a phase angle of π/4 ahead of the fluctuating velocity as measured by a hot-film probe in the pipe center. This is exactly the …

A Critical Survey Of Turbulence In Bearings, E. A. Saibel, N. A. Macken

Symposia on Turbulence in Liquids

The subject of turbulence in bearings is critically surveyed. Both experimental and theoretical investigations are discussed. It is noted that beyond the laminar range, Taylor vortices develop. Some vortex structure exists even up to the highest Reynolds numbers. This suggests that the turbulence in bearings is much different from that which is found in other flows such as pipes or boundary layers. Unfortunately, the theoretical models have been based on mixing length or "law of the wall" information. A call is made for experimental information to formulate new theory applicable to bearings.

Measurements To Elucidate The Mechanism Of Drag Reduction, R. J. Hansen

Symposia on Turbulence in Liquids

A number of investigators have attributed the reduced turbulent flow drag exhibited by polymer solutions to their high elongational viscosity. The results of a recent theoretical study of drag reduction are summarized, which show that it may instead be a consequence of the non-Newtonian behavior of polymer solutions in time-varying shear fields. Experiments are proposed to ascertain the relative importance of these transient shear effects and elongational effects in reducing drag.

Wavevector/Frequency Spectrum Of Turbulent-Boundary-Layer Pressure, D. M. Chase

Symposia on Turbulence in Liquids

Knowledge of the wavevector/frequency spectrum of wall pressure, P(K,ω) [K = (k₁,k₃)], for a normal turbulent boundary layer has been largely confined to properties depending on the mean-convective ridge (k₁=ω/u_c). Recent theoretical work yields the wavevector dependence of P(K,ω), for flow at low Mach numbers, also in the acoustic wave number domain where K ≤ ω/c, except for undetermined functions of ωδ/U_∞. In the nonconvective but incompressive domain of wavevectors (important in underwater acoustics), apart from the proportionality to K² where ω/c ≤ K ≤ δ^-1, the …

Effect Of Randomly Fluctuating Pressure Gradients, With Arbitrarily Specified Power Spectrum And Probability Density, On Flow In Channels, M. Perlmutter

Symposia on Turbulence in Liquids

A randomly fluctuating longitudinal pressure gradient of a non-Gaussian form and arbitrary power spectrum will cause a randomly fluctuating velocity to be superimposed on the steady incompressible flow in a channel. Pressure- gradient and velocity correlations, frequency response functions and system power loss are calculated. Numerical random pressure gradient signals were generated using Fourier series expansion, with random picking of discrete Fourier spectrum values and a nonlinear no memory transformation. Numerical values of the velocity signal were then calculated by linear transformation of the pressure-gradient signal. Pressure-gradient and velocity signals were compared for difference in amplitude, frequency, time lag, and …

Turbulent Velocity And Pressure Fields In Boundary-Layer Flows Over Rough Surfaces, W. K. Blake

Symposia on Turbulence in Liquids

This paper is a discussion of recent measurements of the statistics of the turbulent velocity and wall pressure fields in rough-wall boundary layers. These measurements, made in part by the author, have been performed over a variety of walls covering a wide range of roughness sizes and configurations. The various measurements are compared in order to determine the structure and scaling parameters of the turblulent field convected at speeds near the mean velocity of the boundary layer. The mean square turbulent velocities, their one-dimensional spectral densities, and their longitudinal and vertical microscales are compared for different walls. The velocity fields …

Recent Developments Of Electrochemical Wall Mass Transfer Probes And Their Application To Drag-Reducing Polymers, T. J. Hanratty, L. D. Eckelman, G. Fortuna

Symposia on Turbulence in Liquids

Electrochemical mass transfer probes are used to measure the velocity gradient at a wall. Recent advances in their application are reviewed. These include corrections for the time response of the probe, the simultaneous measurement at a number of locations of the two components of the fluctuating velocity gradient and a study of the influence of drag reducing polymers on turbulence. It is found that drag-reducing polymers cause an increase in the scale of flow oriented eddies in the viscous sublayer.