Properties of conditional eddies in free shear flows
Abstract
Large structures in two types of free turbulent flows namely, grid turbulence and twostream, plane mixing flow, were investigated through studies of conditional averages. The conditional averages of interest were expected values of the instantaneous velocity and the secondorder velocity moment around a point where the velocity was specified. Fourthorder estimation of the conditional velocity as a truncated Taylor's series expansion in terms of the given velocity was derived explicitly by using properties of isotropic turbulence. Typical grid turbulence data of higherorder velocity moments and space correlations were used to derive estimated flow patterns. It was found that the linear estimation is as good, in studying the conditional eddies in isotropic turbulence, as higherorder estimation for most probably fluctuation intensities. A welldefined twostream, plane mixing layer was produced with a lowspeed wind tunnel for the experimental study. The conditional averages were measured in the selfpreserving region with two xsensor, hotwire anemometers. The resulting conditional eddies represented large structures depicted from unconditional observations in an averaged sense. Also, linear estimates were evaluated from measured and modeled space correlations, and their evaluated from measured and modeled space correlations, and their adequacy in approximating measured conditional velocity was confirmed.
 Publication:

Ph.D. Thesis
 Pub Date:
 1982
 Bibcode:
 1982PhDT........19T
 Keywords:

 Flow Characteristics;
 Shear Flow;
 Turbulent Flow;
 Vortices;
 Average;
 Estimating;
 Flow Velocity;
 Mixing Layers (Fluids);
 Series Expansion;
 Taylor Series;
 Turbulent Mixing;
 Wind Tunnel Tests;
 Fluid Mechanics and Heat Transfer