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CONTROL OF THREE-DIMENSIONAL FLOW OVER A TURRET WITH A FLAT APERTURE

Miguel R. Palaviccini
Mechanical and Aerospace Engineering Department IMG, University of Florida Gainesville, FL 32611, USA

Louis N. Cattafesta III
Department of Mechanical Engineering Florida Center for Advanced Aero-Propulsion, Florida State University 2003 Levy Ave, Tallahassee, FL 32310, United States of America

Résumé

A study of the baseline flow physics around a submerged hemispherical turret with a flat aperture at Ma < 0.26 is characterized, identifying potential sources of aero-optic distortion. Unsteady pressure measurements reveal that the recirculation region and separated shear layer are two dominant regions contributing to the unsteadiness of the flow. Oil flow-visualization illustrates the three dimensional separation line and length of recirculation region, both investigated as possible metrics for flow control applications. Stereoscopic PIV is used to characterize the separated shear layer showing its two-dimensional nature near the separation location. Malley probe measurements are made along the flat window, providing one-dimensional slices of optical wavefronts in the direction of the beam propagation vector. Passive control is implemented via cylindrical pins to generate streamwise vortices that promote cross stream mixing between the high momentum freestream and the lower momentum boundary layer. Flow visualization determined that the length of the recirculation region shows a direct correlation with the measured aero-optics. Active flow control is achieved via steady blowing along the top portion of the flat aperture. Results suggest that full reattachment along the window is not necessary to achieve an improvement in the optical environment.