Scaling of flat plate drag reduction using plasma-generated streamwise vortices

Abstract

Skin-friction drag reduction (DR) in a turbulent boundary layer (TBL) using plasma-generated streamwise vortices (PGSVs) is governed by plasma-induced spanwise wall-jet velocity, the distance between the positive electrodes of two adjacent plasma actuators (PAs) and the friction Reynolds number. It is found experimentally that DR increases logarithmically with the growing maximum spanwise mean velocity but decreases with rising and, where superscript '+' denotes normalization by the inner scales. It is further found from theoretical and empirical scaling analyses that the dimensionless drag variation may be reduced to, where and are different functions and the scaling factor (and are constants) is physically the circulation of the PGSVs. Discussion is conducted based on, which provides important insight into the physics of TBL control based on PAs.