Accession Number : ADP004066

Title :   Turbulent Drag Reduction Research,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER

Personal Author(s) : Bushnell,D. M. ; Anders,J. B. ; Walsh,M. J. ; McInville,R. V.

Report Date : AUG 1984

Pagination or Media Count : 13

Abstract : This paper summarizes recent NASA research in the area of turbulent drag reduction for attached flows. The most promising passive techniques utilize non-planar geometry and indicate a possible combined net performance on the order of 20 percent. Of particular interest is the suitability of these devices for retrofit of existing vehicles. Research to optimize an active system involving tangential slot injection of low momentum (LFC) air indicates that free shear layers which are initially turbulent can be favorably controlled through use of rigid plates (large eddy-breakup devices). More conventional flow control approaches -- such as narrow-band acoustic inputs -- are evidently not effective for free mixing regions imbedded in thick turbulent layers. Experiments indicate that high frequency forcing of Emmons spots in the initial transition region to create small scale motions provides localized drag reductions, but net reductions are not yet available due to the high levels of forcing energy required.

Descriptors :   *Drag reduction, *Boundary layer control, Skin friction, Turbulent boundary layer, Attachment, Laminar flow, Suction, Eddies(Fluid mechanics), Aerodynamic control surfaces, Retrofitting, Grooving, Aerodynamic slots, Injection, Ribs

Distribution Statement : APPROVED FOR PUBLIC RELEASE