Accession Number : ADA185662

Title :   Studies of Unsteadiness in Boundary Layers.

Descriptive Note : Annual rept. 1 May 86-30 Apr 87,

Corporate Author : UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF AEROSPACE ENGINEERING

Personal Author(s) : Blackwelder, Ron ; Kaplan, R E ; Ho, Chih-Ming ; Huerre, Patrick ; Redekopp, Larry G

PDF Url : ADA185662

Report Date : 26 Jun 1987

Pagination or Media Count : 11

Abstract : Experimental and theoretical efforts aimed at clarifying and revealing important dynamical features of several turbulent shear flows are described. The flows studied include boundary layers, jets, wakes and separated flows on lifting surfaces. Significant progress has been made through experimental studies toward understanding: (i) processes in turbulent boundary layers responsible for the production of turbulent energy via local, inflectional-instability events and the modification of boundary layer growth and entrainment by passive large-eddy manipulation devices; (ii) procedures for enhancing entrainment and mixing in jets either by actively forcing the flow or by passively contouring the jet exit; and (iii) characteristics of boundary layer separation and its control on lifting surfaces in unsteady flows. Theoretical studies on the temporal and spatial structure in blunt-body wakes have revealed the necessary conditions under which global, self-sustained oscillations appear and, also, have provided firm criteria for specifying the frequency of these oscillations. The results are consistent with existing experimental evidence and suggest promising approaches for drag modifications for flow over bluff bodies. Several experimental facilities have been designed. Keywords: Separated flows; Unsteady flows; Turbulent shear flows.

Descriptors :   *LIFTING SURFACES, *SHEAR PROPERTIES, *TURBULENT BOUNDARY LAYER, *UNSTEADY FLOW, BOUNDARY LAYER, DRAG, FLOW SEPARATION, GROWTH(GENERAL), MODIFICATION, OSCILLATION, PRODUCTION, RESEARCH FACILITIES, SELF OPERATION, TURBULENT FLOW, WAKE, AERODYNAMIC DRAG, BLUNT BODIES, EXPERIMENTAL DESIGN

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE