Response of Two-Dimensional Separation to Three-Dimensional Disturbances

[+] Author and Article Information
Laura L. Pauley

Department of Mechanical Engineering, The Pennsylvania State University, University Park, PA 16802

J. Fluids Eng 116(3), 433-438 (Sep 01, 1994) (6 pages) doi:10.1115/1.2910295 History: Received August 03, 1993; Revised February 16, 1994; Online May 23, 2008


The present study investigates the development and structure of three-dimensionality due to a three-dimensional velocity perturbation applied to the inlet of an unsteady two-dimensional separation computation. A random noise perturbation and a sine-wave perturbation are considered separately. In both cases, the spanwise variations were amplified in the separation and within the shed vortices. The vortex shedding frequency observed in the two-dimensional computation was not altered by the three dimensionality of the flow field. No observable spanwise structure was produced by the random noise perturbation. The sine-wave perturbation, however, produced longitudinal Görtler vortices within the separation. Using a linear stability analysis, the presence of longitudinal vortices in a separated laminar boundary layer was predicted by Inger (1987). When the velocity field was averaged across the span, it was found that the sine-wave perturbation increased the separation length and reduced the strength of shed vortex. The span-averaged streamlines from the random noise perturbation, however, reproduced the unsteady separation of the two-dimensional computations.

Copyright © 1994 by The American Society of Mechanical Engineers
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