A note on the stability of slip channel flows

We consider the influence of slip boundary conditions on the modal and nonmodal stability of pressure-driven channel flows. In accordance with previous results by Gersting ["Hydrodynamic stability of plane porous slip flow," Phys. Fluids 17, 2126 (1974)] but in contradiction with the recent investigation of Chu ["Instability of Navier slip flow of liquids," C. R. Mec. 332, 895 (2004)], we show that the slip increases significantly the value of the critical Reynolds number for linear instability. The nonmodal stability analysis, however, reveals that slip has a very weak influence on the maximum transient energy growth of perturbations at subcritical Reynolds numbers. Slip boundary conditions are therefore not likely to have a significant effect on the transition to turbulence in channel flows. (c) 2005 American Institute of Physics.