Hydrodynamic stability of HeII periodic boundary layer flows

He II periodic boundary layer experiments on the damping of torsional oscil lations of a sphere have been re-analyzed based on recent classical stabili ty theory. We have verified this theory using a torsionally oscillating sph ere and an electrochemical visualization scheme in water. We show that macr oscopic He II periodic boundary layer flows exhibit instabilities that are described by classical stability criteria if the kinematic viscosity is reg arded as the dynamic viscosity over the total fluid density. (C) 2000 Elsev ier Science B.V. All rights reserved.