Spectral Energy Transfer in Transition of Plane Wake

Abstract

Energy transfer mechanisms from the mean flow to unstable modes and among these modes play an important role in the sequence of instabilities that take place in the transition to turbulence of shear flows. An experimental investigation is carried out to quantify the linear and nonlinear energy transfer rates among unstable modes in the transition to turbulence of a plane wake. These quantities are derived from higher-order statistical moments. The results show that, initially, the dominant features of the transition are exponential growth of unstable modes and nonlinear energy transfer from these modes to their sum (harmonic bands) and difference (low-frequency) components. By distant interactions the low-frequency modes play an important role in the redistribution of energy to all other components throughout the transition.