Near Wall Visual Measurements in Drag Reducing Flow

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

Drag reduction in Newtonian polymer solutions

Prior work in the area of drag reduction has been mainly limited to aqueous solutions. Theoretical and empirical analyses of the resulting data in aqueous solutions have been hindered by the fact that some polymers cause drag reduction and others do not...This investigation was directed to the study of how the size and configuration of the polymer molecule in solution affected drag reduction and the related phenomenon of turbulence suppression. Apparatuses were designed and built to measure viscometric flow, curves, friction factors, velocity profiles, and normal stresses (by a jet thrust technique developed by Metzner and associates) --Summary, page 1-2

Existence Of Two Types Of Drag Reduction In Pipe Flow Of Dilute Polymer Solutions

Drag reduction in the pipe flow of polymer solutions is shown to be of two types which apparently occur by two separate mechanisms. In turbulent flow, drag reduction is probably caused by viscoelastic effects. The critical solvent Reynolds number at the onset of drag reduction is proportional to about the first power of the diameter. Thus, the critical velocity is independent of tube diameter. Polymers dissolved in good solvents show more drag reduction than in poor solvents. The other type of drag reduction occurs when the laminar region is extended to high Reynolds numbers. It is followed by a transition region and a turbulent region in which the drag is not affected. © 1967, American Chemical Society. All rights reserved

Price Elasticity of Demand for Term Life Insurance and Adverse Selection

This paper provides an empirical estimate of price' and risk' elasticities of demand for term life insurance for those who purchase some insurance. It finds that the elasticity with respect to changes in premiums is generally higher than the elasticity with respect to changes in risk. It also finds that the elasticity, in the range of -0.3 to -0.5, is sufficiently low that adverse selection in term life insurance is unlikely to lead to a death spiral and may not even lead to measured effects of adverse selection on total purchases.

Numerical Differentiation Of Equally Spaced And Not Equally Spaced Experimental Data

Procedures are given for smoothing and differentiating experimental data with both equal and nonequal spacing in the independent variable. Selection of the number of points to be included in the movable strip technique and of the degree of the polynomial is discussed. Equations are given to estimate the error by calculating a confidence interval on each slope. A technique for handling certain types of nonrandom errors is presented. © 1967, American Chemical Society. All rights reserved

Promises and Lies: Restoring Violated Trust

Trust is critical for organizations, effective management, and efficient negotiations, yet trust violations are common. Prior work has often assumed trust to be fragile—easily broken and difficult to repair. We investigate this proposition in a laboratory study and find that trust harmed by untrustworthy behavior can be effectively restored when individuals observe a consistent series of trustworthy actions. Trust harmed by the same untrustworthy actions and deception, however, never fully recovers—even when deceived participants receive a promise, an apology, and observe a consistent series of trustworthy actions. We also find that a promise to change behaviour can significantly speed the trust recovery process, but prior deception harms the effectiveness of a promise in accelerating trust recovery

How Physicians React to Cost-Effectiveness Information

Since 1998, the growth of health care spending has accelerated to levels not seen since the 1980s. This growth has renewed pressures on physicians to practice “cost-effective” care, since physicians’ decisions account for the vast majority of all health care spending. But little is known about what physicians think about cost containment, and how they incorporate cost-effectiveness information into their practice patterns. This Issue Brief summarizes three related studies that describe primary care physicians’ attitudes toward considering costs in their clinical decisions, and the effects of providing cost-effectiveness information on physicians’ recommendations

An Experimental Facility for the Visual Study of Turbulent Flows

An experimental technique which allows visual observations of the wall area in turbulent pipe flow is described in detail. It requires neither the introduction of any injection or measuring device into the flow nor the presence of a two-phase flow or of a non-Newtonian fluid. The technique involves suspending solid MgO particles of colloidal size in trichloroethylene and photographing their motions near the wall with a high speed movie camera moving with the flow. Trichloroethylene was chosen in order to eliminate the index of refraction problem in a curved wall. Evaluation of the technique including a discussion of limitations is included. Also the technique is compared with previous methods of visual observations of turbulent flow

Stereoscopic Photography of Shear Flow Turbulence

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 previously developed in our work by Nychas, Hershey and Brodkey (J. Fluid Mech. (1973) 6l, 513)