Doctoral Dissertations

P. Sundaram

Date of Award

3-1987

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Aerospace Engineering

Major Professor

J. M. Wu

Committee Members

K. C. Reddy, Edward Kraft, John Steinhoff, Mitsuru Kurosaka, Trevor Moulden

Abstract

An inviscid unsteady vortex dynamics study is presented here to study the flow details in several free and bounded shear flows. The specific flows considered here are the starting vortex behind sharp edges, the vortex street behind bluff body wakes, the plane mixing layers between two streams and the wall bounded vortex street. Using the unsteady vortex dynamics models developed for each of these flows and through the Lagrangian dynamics computational approach, the streakline and pathline pattern have been computed for these flows. From the combined study of the computed streakline and pathline pattern, various flow visualization details and the illusions created by the streaklines have been identified and explained.

With the accuracy of the unsteady vortex model for the vortex street wake having been verified by the good agreement obtained between the computed and flow visualization results, the model has been used to investigate the different flow interactions present in this complex flow. The first case chosen for analysis is the thermo-fluid interaction that exists in this flow. It has been shown, through the computed instantaneous total temperature, that the bluff body wake exhibits regions of separated energy. Further, the well known phenomenon of Eckert-Weise effect, which predicts a cold near wake, has been obtained by temporally averaging the instantaneous total temperature, thus proving that the cause of this phenomenon is the unsteady vortex motion in the wake. In a similar manner, the familiar result of a loss in total pressure in the near wake can be interpreted to result from the time averaged total pressure separation phenomenon.

The second case considered here for the vortex interaction study is the interference caused by the channel walls in a wall bounded vortex street wake. From the computed streakline pattern and also through the flow visualization studies, an interesting vortex dynamics result that forces the flow from both sides of the wake to interchange their sides has been obtained. This result explains the mechanism for the static temperature reversal between the two sides of a wall bounded wake that was observed by Minchin. Further, the present computational study highlights the important inviscid entrainment effects of the convecting vortices by showing that the eruption-like appearance of the wall layer streaklines observed in the flow visualization pictures is predominantly due to the inviscid entrainment effects and not merely caused by the viscous effects.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS