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Turbulence and Shear Flow Phenomena -1 First International Symposium

ISBN:
1-56700-135-1 (Print)

MODIFICATION OF NEAR-WALL STRUCTURE IN A THREE-DIMENSIONAL TURBULENT BOUNDARY LAYER

Robert O. Kiesow
School of Mechanical Engineering Maurice J. Zucrow Laboratories (formerly Thermal Sciences and Propulsion Center) Purdue University West Lafayette, IN 47907, USA

Michael W. Plesniak
Maurice J. Zucrow Laboratories (formerly Thermal Sciences and Propulsion Center), School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA; Department of Mechanical and Aerospace Engineering The George Washington University

Abstract

The near-wall physics and turbulence structure of a planar, shear-driven, three-dimensional turbulent boundary layer (3DTBL) are examined in a specialized facility with varying strengths of crossflow. The spanwise shear results in a modification of the near-wall turbulence structure. Analysis of flow visualization data reveals a reduction of mean streak length by as much as 50% with increasing spanwise shear, while streak spacing remains relatively constant. Power spectra of velocity confirm this shift towards higher temporal frequencies, corresponding to decreased streamwise length scales. Particle image velocimetry measurements indicate a significant modification of the inner region of the boundary layer with increasing spanwise shear. Streamwise velocity profiles exhibit an increasing velocity deficit with increased crossflow. Increased levels of the normal Reynolds stresses u2 and v2 and an increase in the − uv Reynolds shear stress are also observed. Notable modifications in the spanwise vorticity were also observed at higher shear rates.