Pattern recognition analysis of a turbulent separated flow with D-PIV
by
Fulvio Scarano
von Karman Institute for Fluid Dynamics (Belgium) and DETEC University of Naples (Italy)

A pattern recognition technique for the investigation of large-scale coherent structures, is applied in the turbulent separated flow over a backward facing step (BFS) at a Reynolds number of Reh=5000. The Instantaneous two-dimensional velocity distribution is obtained by means of digital particle image velocimetry (D-PIV). High spatial resolution (delta_r=0.05h) is achieved with the application of an iterative window refinement image processing algorithm. The measurement plane is oriented in order to investigate span-wise aligned vortices footprints. The detection algorithm is based on velocity patterns spatial cross-correlation. An additional isotropy condition is proposed to improve the detection of vortices and shear layer. The structure of the shear layer emanating from the step edge is examined emphasising the role of coherent fluctuations with scale d ranging from 0.25h to 0.65h. Conditional data averaging is also applied to the results and structural properties (coherent velocity and vorticity) are obtained.

Date received: February 9, 1999

Copyright © 1999 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cacp-43.