Chemical Engineering Commons^™

Some Observations Of Wake Behavior In Laminar And Turbulence Free Stream Flow, L. E. Seeley, R. L. Hummel, J. W. Smith

Symposia on Turbulence in Liquids

Visual observations of the sphere wake have been obtained using the flash photolysis technique. Free stream turbulence of 7 and 10% was found to progressively reduce the size of the wake but no turbulence was found in the attached shear layer nor was the position of the separation point affected. A separation bubble was identified as predicted by Son and Hanratty (1969). Evidence is presented to show that drag reduction in turbulent free streams is not due to turbulence in the attached boundary layer but to enhanced momentum transfer in the wake.

The Roles Of Large Scale Structures In The Initial Development Of Circular Jets, F. K. Browand, J. Laufer

Symposia on Turbulence in Liquids

Experimental results are presented describing the flow field surrounding the potential core of a circular water jet in the Reynolds number region between 5,000 and 15,000. This field is divided into three regions: 1) the shear layer instability zone; 2) the vortex interaction region; and 3) the zone of higher order instability mode and turbulence generation. It is shown that the origin of the large scale structures just downstream of the potential cone can be traced to the upstream vortices, but their statistical behaviour (passage frequency, spatial coherence) seems to be independent of the initial shear layer instability.

Stereoscopic Photography Of Shear Flow Turbulence, A. K. Praturi, H. C. Hershey, R. S. Brodkey

Symposia on Turbulence in Liquids

The last several years have seen numerous advances in the understanding of the coherent motions that exist in turbulent shear flows. These studies have provided the underlying basis of most of the experimental investigations of coherent motions using conditional sampling, quadrant splitting, pattern recognition, etc. Lacking, however, in the visual work is a true three- dimensional view of the processes, which are known to be three-dimensional in nature. Possible means of providing information about the third dimension are reviewed. Details of an evaluation of a stereoscopic-photographic, high-speed motion picture system are given. The system utilizes the boundary layer flow channel …

Two-Dimensional Analysis Of The Coherent Instationary Motion Induced By An Obstacle, Using Electrochemical Methods, B. Py, C. Tournier

Symposia on Turbulence in Liquids

The non stationary flow induced by a cylinder with a square cross-section was studied on the cylinder's surface and in the wake with two different electrochemical probes. On the cylinder was mounted split rectangular electrodes with high enough aspect ratio so as to measure the chordwise component of the wall shear stress with its sign. The non-linear response of this transducer was studied. In the wake, the longitudinal component of the velocity was obtained with conical electroactive elementswhich are mainly sensitive to this component.

The fluctuating coherent components are separated from the aleatory part of the signal and then decomposited …

Author Index, University Of Missouri--Rolla

Symposia on Turbulence in Liquids

No abstract provided.

Conference Proceedings Of The 4th Biennial Symposium On Turbulence In Liquids, University Of Missouri--Rolla

Symposia on Turbulence in Liquids

No abstract provided.

On The Role Of Conditional Averages In Turbulence Theory, R. J. Adrian

Symposia on Turbulence in Liquids

It is shown that conditional averages in the form of expected values of functions of the velocity at an arbitrary point given the velocities at a finite number of distinct points, appear naturally in certain types of turbulence theories and that the closure problems in such theories ultimately reduce to the approximation of these averages. Two exemplary theories are considered. The first is characteristic of turbulence models formulated in terms of probability density functions whereas the second is related to the derivation of optimal algorithms for the numerical integration of the turbulent Navier-Stokes equations at large Reynolds numbers. Some mathematical …

Front Matter, University Of Missouri--Rolla

Symposia on Turbulence in Liquids

No abstract provided.

Measurements In Turbulent Water And Two-Phase Flows By Laser Anemometry, A. Melling, J. H. Whitelaw

Symposia on Turbulence in Liquids

Measurements of the mean and rms values of the longitudinal velocity in a rectangular duct are reported. These results were obtained in a water flow using a laser anemometer. The important design criteria which facilitated the measurements are described and gradient, transit-time, noise and refractive-index corrections are specifically discussed. The results demonstrate the development of a rectangular duct flow and, in particular, reveal that a small lack of symmetry at the duct entrance can readily be identified in the normal- stress results, 37 hydraulic diameters downstream.

The possibility of utilizing water droplets in steam and gas bubbles in water to …

Individual Realization Laser-Doppler Technique Applied To Turbulent Channel Flow, W. G. Tiederman, D. K. Mclaughlin, M. M. Reischman

Symposia on Turbulence in Liquids

Measurements of the mean and turbulence intensity of the streamwise velocity component in a fully developed, two-dimensional channel flow of water are presented. The measurements were made with the individual realization laser Doppler technique and emphasize the near-wall region of the flow. A dual-scatter optical arrangement was used which employs 90° scattering and yields a probe volume whose length normal to the wall is 0.0075 inches. A correction has been made to the data that accounts for the statistical biasing which occurs in the individual realization technique. The corrected data demonstrate that the individual realization technique can yield accurate velocity …

Intermittency And Structure Of A Jet Exhausting Into A Stratified Fluid, Alan Brandt, H. E. Gilreath, C. L. Yates, C. R. Walton

Symposia on Turbulence in Liquids

This preliminary study of the mechanism by which local turbulent regions generate internal gravity waves in a stably stratified fluid is based on comparisons of the visual and hot-film- anemometer observations of a jet exhausting into a stratified fluid with those for a jet exhausting into a homogeneous medium. The stratified environment limits the growth of the mean jet boundary, or from another point of view, inhibits the vertical motion of the instantaneous turbulent/non-turbulent interface. The visual and non-conditional statistical averages agree with expectations and with previous measurements in stratified turbulent wakes. Application of a standard criterion to determine the …

Promising Directions For Liquid Turbulence Research --Panel Discussion, Victor Goldschmidt, J. H. Whitelaw, V. A. Sandborn, Val Kibens, R. E. Kaplan

Symposia on Turbulence in Liquids

No abstract provided.

Dynamic Response Of Forced Convective Heat Transfer From Cylinders To Low Prandtl Number Fluids, D. G. Malcolm, V. Verma

Symposia on Turbulence in Liquids

The present paper can be viewed as an extension of the work of Lim and Sleicher (9). They evaluated the frequency response of the heated element submerged in liquid metal by a perturbation method for Peclet numbers of up to 0.4. Velocity fluctuations were assumed small and second-order perturbations neglected. The Oseen approximation was made to the velocity field. Here the velocity configuration has been approximated to that of potential flow and the convection equation has been solved numerically with the aid of a digital computer. The potential flow approximation, as compared with the Oseen approximation, is reasonable over a …

Oceanic Shear Measurements Using The Airfoil Probe, Thomas Osborn, Thomas Siddon

Symposia on Turbulence in Liquids

Vertical profiles of salinity and temperature in the ocean reveal fluctuations with length scales as small as a few mil 1imeters. These fluctuations, called microstructure by oceanographers, are the small scale results of turbulent mixing processes. It is hoped that through the study of microstructure we can evaluate the relative importance of different sources of the turbulent energy (e.g., tides, large scale internal waves, etc.) and the mechanisms for generation of the turbulence (e.g., wave overturn, shear instability, etc.).

There is a considerable body of evidence to suggest that shear instability is an important mechanism in the generation of ocean …

Use Of The Split-Film Sensor To Measure Turbulence In Water Near A Wall, Paul H. Blinco, V. A. Sandborn

Symposia on Turbulence in Liquids

Because of its small size and unique design, the 0.15-mm diameter split-film sensor has many significant advantages over the conventional X-configuration hot-film sensor and the yaw-wire technique for measuring turbulence near a wall. Calibration of the split- film sensor indicates that the magnitude and yaw angle of the instantaneous velocity vector is dependent only on the sum and ratio of the sensor outputs, respectively. Results of limited measurements of the longitudinal and vertical turbulence intensities and Reynolds stress for hydraulically smooth, free surface flows are presented. Digital time series of the split-film outputs revealed the following information: (1) the split-film …

Author Index, University Of Missouri--Rolla

Symposia on Turbulence in Liquids

No abstract provided.

Statistical Analysis Of Instantaneous Velocities In Turbulent Flow Of Dilute Viscoelastic Solutions, A. L. Rollin, F. A. Seyer

Symposia on Turbulence in Liquids

An experimental study, based on streak photograph determination of instantaneous velocities, was directed at determining the structure of turbulence within the boundary layer and core regions of circular pipes. The measurements lend support to the ejection phenomenon as the mechanism controlling drag reduction.

A correlation factor, defined as the ratio of the observed number of positive instantaneous radial velocities, to the observed number of negative instantaneous radial velocities, suggests acceleration in the radial direction as the elements of fluid move through the sublayer. The correlation factor also provides information about the thickening of the boundary layer for drag reducers relative …

Flow Visualization Studies On Drag-Reducing Turbulent Flows, R. H. J. Sellin

Symposia on Turbulence in Liquids

Flow visualisation studies in a square duct of internal dimensions 44.5 x 44.5 mm are reported. The flow marker is a stream of opaque white dye, released from a downstream facing stationary tube, and it is photographed through the plexiglass wall of the duct. The point of dye release can be traversed in a direction perpendicular to the duct wall and three locations are investigated, two in the core of the flow and one in the near- wall region. By using Is exposure times photographs are obtained of a dye dispersion cone and the cone angle is measured and related …

Experiments On The Structure Of Turbulence In Fully Developed Pipe Flow, T. R. Heidrick, S. Banerjee, R. S. Azad

Symposia on Turbulence in Liquids

This paper describes a series of two-point measurements in fully developed pipe flow. Measurements of the phase shifts between the Fourier components of the axial velocity fluctuations at two points were made with three different orientations of the two points. In all cases the two points were close enough together that the turbulent structure remained essentially "frozen" while passing between the sensors. The phase velocities, C₁(f), and inclinations, α(f) (defined previously by Heidrick et al. (8)), of each frequency component, f, were determined from these measurements.

In general, the Fourier components are inclined to the wall - the …

Measurements Of Pulsating Turbulent Water Flow In A Tube, S.-Z. Lu, R. J. Nunge, F. F. Erian, M. Mohajery

Symposia on Turbulence in Liquids

The experimental method associated with obtaining meaningful information from the hot-film anemometer signals in fully developed pulsating turbulent flow where the pulsations are sinusoidal in time is discussed. The results of a number of experiments in water reveal the nature of the longtime and short-time average velocity and pressure. Velocity measurements between 0.95 radii and the centerline demonstrate that the long-time average velocity distribution is coincident with that for steady turbulent flow at the same Reynolds number. Also, no significant differences between the longtime average axial pressure drop in the pulsating and steady flows were noted, although this requires further …

Measurement Of Unsteady Flows In Mercury With Hot-Film Anemometers, Charles A. Sleicher, G. B. Lim

Symposia on Turbulence in Liquids

The difficulties in making turbulence measurements in liquid metals are discussed briefly. Attention is then focused on the problem of frequency response attenuation of hot-film anemometers by the thermal capacity of the thermal boundary layer near cylindrical sensors. A solution is given to the problem of heat transfer from an infinite cylinder normal to the potential flow of a fluid with a small sinusoidal velocity component. Application of the results to anemometer measurements is discussed. Some preliminary experiments on dynamic calibration are reported, and they are in reasonable agreement with the theory for Peclet numbers less than one.

Turbulence Measurements In Submerged Water Jets By Electromagnetic Induction Anemometry, Walter C. Mih

Symposia on Turbulence in Liquids

This paper describes the measurement and data analysis of the turbulence in a two-dimensional water jet discharging from a thin slot into a large body of stationary water having the same width as the slot. Tap water without additives was used as the flow medium. The electromagnetic induction method (commonly known as magnetohydrodynamics, or the MHD method) was used to sense the fluctuation velocities in the diffusion zone of the jet. A DC magnet was placed outside the flow field with the magnetic flux density of 885 Gauss perpendicular to the plane of homogeneity of the two-dimensional flow field. A …

Hydrogen-Bubble Flow-Visualization: Limitations In Drag Reducing Polymer Solutions, George L. Donohue

Symposia on Turbulence in Liquids

Hydrogen-bubble flow-visualization experiments have demonstrated that distinct bubble pulses cannot be obtained in water solutions of polyacrylamide of high enough molecular weight to cause drag reduction at low shear stresses. Good bubble pulses were obtained in poly(ethylene oxide) and in surfactant solutions, but they did not cause drag reduction at feasible shear stresses.

Measurement Of Reynolds Stress And Turbulence In Dilute Polymer Solution By Laser Velocimeter, Samuel E. Logan

Symposia on Turbulence in Liquids

Measurements of Reynolds stress and axial and transverse turbulence intensities have been made in turbulent pipe flow of a dilute solution of high molecular weight polymer and compared to measurements made with pure water. A laser velocimeter capable of measuring these turbulence parameters has been developed and utilized.

Axial turbulence intensities are consistent in behavior and magnitude with previous polymer results and the measurements of transverse intensity and Reynolds stress are similarly well behaved and self consistent. Sublayer thickening in drag reducing polymer solution is observed, in consonance with earlier work. New results include demonstration that the turbulent shearing stress …

Conference Proceedings Of The 3rd Biennial Symposium On Turbulence In Liquids, University Of Missouri--Rolla

Symposia on Turbulence in Liquids

The Third Biennial Symposium on Turbulence in Liquids showed further progress in the investigator's ability to measure turbulence parameters and in the general understanding of turbulence. The most impressive advances in measurement seemed to be the ability to measure deeper into the turbulent boundary layer in order to obtain profiles over the entire turbulence production region and the rapid development of conditioned-sampling techniques for studying hypotheses for mechanisms.

Ldv Measurements In Turbulent Free Convection, R. J. Adrian

Symposia on Turbulence in Liquids

The design and performance of a laser Doppler velocimeter (LDV) used in a turbulent water-overice convection experiment are described. The LDV was operated in a reference beam mode with an ultrasonic diffraction grating shifting the reference beam frequency to provide bipolar sensing of the vertical velocity, and a phase-locked loop was used to demodulate the Doppler frequency information. The maximum observed velocities in the experiment were ± 1 mm/sec, and the accuracy of instantaneous measurement was limited by Brownian motion and laser line width to ± .04 mm/sec for a 2 Hz frequency response. The practical difficulties encountered in this …

Features Of A Separating Turbulent Boundary Layer As Revealed By Laser And Hot-Film Anemometry, R. L. Simpson, J. H. Strickland, P. W. Barr

Symposia on Turbulence in Liquids

Experiments have been performed to determine the fundamental nature of boundary layer separation produced by an adverse pressure gradient. Measurements upstream and downstream of the separation zone have been made utilizing laser and hot-film anemometry techniques.

A completely mobile backscattering laser anemometer was developed. This alone is a significant development because of the relatively long focal lengths required for measurements in a 36" wide wind tunnel. Signal processing was achieved by a digital signal sampling and storage system. Both mean and fluctuating velocities in both the unseparated and separated flow regions were measured. Experimental results are in fairly good agreement …

Turbulence Measurements With A Sampling Laser-Doppler Velocimeter, P. D. Iten

Symposia on Turbulence in Liquids

A novel sampling signal processor overcomes the difficulties encountered with frequency trackers in the investigation of unseeded highly turbulent flows. This sampling system consists essentially of a swept filter, e.g. a standard RF-spectrum analyzer, a digital data memory and a storage oscilloscope. It is able to determine first-order statistical averages of turbulent flows with high fluctuation frequencies and amplitudes even at very low scattering particle concentrations. Since the velocity samples are not statistically independent of the velocity, the sampled velocity data has to be corrected in order to obtain unbiased statistical averages. A theoretical analysis and experimental investigations of the …

Analysis Of A Laser Correlation Anemometer, L. Lading

Symposia on Turbulence in Liquids

An analysis of a laser anemometer is given. The anemometer is based on the cross correlation of the random signals generated by the scattering from -- and/or extinction of -- two parallel laser beams. The basic set-up is compared with the laser Doppler anemometer.

It is shown that the correlation function exhibits a broadening and generally also a skewness - equivalent to the broadening (transit time) and skewness (velocity gradients) of the Doppler spectrum.

The conditions for "instantaneous point" measurements are derived.

It is shown how a particle (drop/bubble) size versus particle velocity spectrum can be obtained by appropriate electronic …

Design Considerations For A Laser Doppler Velocimeter, Leroy M. Fingerson

Symposia on Turbulence in Liquids

In optimizing an instrument design, it is important to differentiate between the theoretical limitations of the technique and apparent limitations that can be reduced or eliminated by design. In the laser-Doppler anemometer, the theoretical limits are associated with the fact that particle velocity is the measurement rather than fluid velocity. The accuracy and speed of the particle velocity measurements do not appear to have theoretical limitations. Therefore, instrument design must concentrate on improving the measurement of particle velocity.

A complete system has been designed to optimize accuracy, speed, convenience, and flexibility in measuring particle velocity. The problems inherent in transferring …