Modification of Near-Wall Structure in a Shear-Driven 3-D Turbulent Boundary Layer

Abstract

The near-wall physics of a planar, shear-driven, 3-D turbulent boundary layer with varying strengths of crossflow are examined. Flow visualization data reveals a reduction of mean streak length by as much as 50% with increasing spanwise shear. Power spectra of velocity confirm this shift towards higher temporal frequencies, corresponding to decreased streamwise length scales. PIV 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 u′2 and v′2 and an increase in the −u′v′ Reynolds shear stress are also observed. Modifications in the spanwise and transverse vorticity were also observed at higher shear rates.