Engineering Commons^™

Continuous Interfacial Polycondensation Of Nylon 6-6, Chandrakant A. Patel

Theses

Nylon 6-6 has been prepared by continuous interfacial polycondensation from hexamethylene diamine and adipyl chloride in a stirred system. The effect of monomer concentration and stirring on the intrinsic viscosity of polyamide 6-6 solution in formic acid (90%) was determined.

As stirring rate and monomer ratio increased, the intrinsic viscosity and polymer yield went through a maximum. Diffusion coefficient (D_AB) for hexamethylene diamine was calculated and from that J_D and mass transfer coefficient /D_AB were calculated. A relation between Reynolds number and J_D factor was established by correlation curve.

Dielectric Properties Of Atactic And Isotactic Polystyrene, Thaddeus F. Kroplinski

Theses

The purpose of this investigation was to determine the dielectric constant and dissipation factor of atactic and isotactic polystyrene at 25°C and at frequencies of 0.1, 1.0, 10, and 100 kilocycles per second. In addition, the effects of molecular weight and crystallinity on the dielectric properties of polystyrene mos also studied.

Polystyrene slabs of uniform thickness mere prepared by molding the polymer under heat and pressure. The isotactic polystyrene slabs Imre annealed at 175°g for various lengths of time to achieve varying degrees of crystallinity.

The molded polystyrene slabs were fitted with circular aluminum foil electrodes to form a three …

Front Matter, 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.

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, …

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 …

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 …

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 …

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.

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 …

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.

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 …

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 …

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 …

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.

An Experimental Investigation In A Turbulent Channel Flow With A Thick Viscous Sublayer (Hot-Film Measurements In Oil), H. Eckelmann, H. Reichardt

Symposia on Turbulence in Liquids

In a turbulent channel-flow hot-film measurements have been made. To achieve a sublayer thickness of approximately 1 cm at y⁺ = 10, oil was used. The Reynolds numbers used for the investigations were 5,600 and 8,200 based on the channel-width of 22 cm and the channel center-line velocity.

In the vicinity of the wall, y⁺ < 0.1, the u'-fluctuations were found to be proportional to the wall distance, y⁺. The u'-values obtained with a hot-film probe for y⁺ > 0.7 were all greater than those obtained with a hot-film wall probe, but extrapolation of the data from the movable hot-film probe to the wall gave good agreement with the data …

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 …

Phase Velocities And Angle Of Inclination For Frequency Components In Fully Developed Turbulent Flow Through Pipes, T. Hedrick, R. S. Azad, S. Banerjee

Symposia on Turbulence in Liquids

Measurements of phase shift and coherence between the streamwise velocity fluctuations at two sensors placed very close to each other have been made in fully developed turbulent flow in a smooth pipe. For the frequencies where the √coherence is near unity (i.e. the correlation between the frequency components is near unity) the phase shifts have been related to the phase velocities and angle of inclination of a "frozen" pattern of turbulence.

Several other quantities such as intensities, energy spectral densities and mean velocities have also been obtained from the data taken with each sensor and these are in good agreement …

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.

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 …

The Comparison Of A New Constant Temperature Anemometer With Several Laser Anemometer Configurations, R. L. Humphrey

Symposia on Turbulence in Liquids

This paper covers electronic design advances that have made it possible to adjust the frequency response of a film probe and make it comparable to that of a wire probe. Also, a test setup for the laser anemometer will be presented using the forward scattering technique. Sample data taken in a hydraulic loop will be related to the laser system output. Following the presentation of the anemometer and laser systems, five fluid flow measurement features will be discussed in order to help the experimenter choose the method most suited to his particular application.

The Spectrum Of Light Scattered From Particles Suspended In A Turbulent Fluid, R. V. Edwards, J. C. Angus, R. Maurer, J. W. Dunning

Symposia on Turbulence in Liquids

All Laser Doppler Velocimeter (LDV) measurements are made by scattering light from small particles suspended in the flow. Further, the scattered light is collected from some finite region within the flow -- commonly called the "sample-volume." These two facts comprise the necessary starting point of an analysis of an LDV.

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 …

Visualization Of Unsteady Flow Over Oscillating Airfoils, G. H. Ruiter, H. M. Nagib, A. A. Fejer

Symposia on Turbulence in Liquids

This study is concerned primarily with the complex nature of leading edge flow separation occurring on airfoils oscillating in a uniform flow field at low Reynolds numbers. The flow field past an oscillating airfoil and a fixed airfoil with an oscillating flap were investigated using various visualization techniques in water. The role of mean flow velocity, instantaneous angle of attack, mean angle of attack and amplitude and frequency of oscillation as well as the location of the support point are examined. The results which were obtained over a range of parameters substantially beyond previous studies include new information regarding the …

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.

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.

The Oxidation Of Carbon Monoxide By Magnesium Aluminate, James A. Whelan

Dissertations

In this research the catalytic oxidation of carbon monoxide was investigated on magnesium aluminate catalysts, MgO:xAl₂O₃, with five different compositions, x, ranging from 1.0 to 3.0. The reaction was run at temperatures ranging from 500 to 600 °C. with radioactive carbon monoxide as the tracer. An experimental technique has been devised for the analysis of unreacted CO which takes into account a correction for the solubility of CO in CO₂.

Four mathematical models were postulated to explain the mechanism of reaction. The models were examined against experimental data by means of non-linear least squares …