Kinematic and Acoustic Similarities of Separated Turbulent Boundary Layers

摘要

A similarity model for separated turbulent boundary layer is proposed as a function of the velocity associated with the maximum local mean shear U_m = (Tm/p)~(1/2). A linear relation between mean velocity and reduced wall-normal coordinate is observed for approximately 40—50% of the boundary layer height. A corresponding similarity model of the far-field sound pressure levels was also derived. The proposed scaling law shows less variability than the classical trailing-edge noise scaling within a range of the freestream velocity and airfoil's angle of attack. In comparison to classical trailing-edge noise, the sound pressure level scaling of separated flow is tuned by a factor of U_m~2, a non-dimensional velocity variable associated with the maximum mean shear stress in the separated boundary layer.