Effect of micron-sized roughness on transition in swept-wing flowsBoundary-layer transition-to-turbulence studies are conducted in the Arizona State University Unsteady Wind Tunnel on a 45-degree swept airfoil. The pressure gradient is designed so that the initial stability characteristics are purely crossflow-dominated. Flow visualization and hot-wire measurements show that the development of the crossflow vortices is influenced by roughness near the attachment-line. Comparisons of transition location are made between a painted surface, a machine-polished surface, and a hand-polished surface. Then, isolated 6 micron roughness elements are placed near the attachment line on the airfoil surface under conditions of the final polish (0.25 micron rms). These elements amplify a centered stationary crossflow vortex and its neighbors, resulting in localized early transition. The diameter, height, and location of these roughness elements are varied in a systematic manner. Spanwise hot-wire measurements are taken behind the roughness element to document the enhanced vortices. These scans are made at several different chord locations to examine vortex growth.
Document ID
19930036191
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Radeztsky, Ronald H., Jr. (NASA Langley Research Center Hampton, VA, United States)
Reibert, Mark S. (NASA Langley Research Center Hampton, VA, United States)
Saric, William S. (Arizona State Univ. Tempe, United States)
Takagi, Shohei (National Aerospace Lab. Tokyo, Japan)
Date Acquired
August 15, 2013
Publication Date
January 1, 1993
Subject Category
Aerodynamics
Report/Patent Number
AIAA PAPER 93-0076
Meeting Information
Meeting: AIAA, Aerospace Sciences Meeting and Exhibit