A model for Reynolds-dependent linear instability in wall-bounded shear flows

Abstract

Recent work demonstrated that alternative models to the "no-slip" boundary condition for incipient flow perturbations can produce linear instabilities that do not arise in the classical formulation. The present study introduces a Robin-type boundary condition with explicit Reynolds-number dependence, which leads to a more physically realistic transition to instability in wall-bounded shear flows. The results show that instability occurs within a Reynolds number range consistent with empirical observations. A physical interpretation of the modified boundary condition in terms of near-wall vorticity dynamics is discussed.