International Journal of Rotating Machinery 
Volume 2006 (2006), Article ID 60234, 12 pages
doi:10.1155/IJRM/2006/60234

Wake Turbulence Structure Downstream of a Cambered Airfoil in Transonic Flow: Effects of Surface Roughness and Freestream Turbulence Intensity

Qiang Zhang and Phillip M. Ligrani

 Turbomachinery Laboratory, Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PG, UK
Received 3 April 2006; Revised 18 July 2006; Accepted 20 July 2006

Abstract

The wake turbulence structure of a cambered airfoil is studied experimentally, including the effects of surface roughness, at different freestream turbulence levels in a transonic flow. As the level of surface roughness increases, all wake profile quantities broaden significantly and nondimensional vortex shedding frequencies decrease. Freestream turbulence has little effect on the wake velocity profiles, turbulence structure, and vortex shedding frequency, especially downstream of airfoils with rough surfaces. Compared with data from a symmetric airfoil, wake profiles produced by the cambered airfoils also have significant dependence on surface roughness, but are less sensitive to variations of freestream turbulence intensity. The cambered airfoil also produces larger streamwise velocity deficits, and broader wakes compared to the symmetric airfoil.