The Combined Effects of Pressure Gradient and Heating on the Stability and Transition of Boundary Layers in Water

Abstract : Appreciable drag reduction is possible if extended regions of laminar flow can be maintained. Although a variety of techniques for boundary-layer control have been explored, only recently has the powerful effect of heat transfer on the stability and transition of water boundary layers been realized. This report presents computational results for the stability and predicted transition characteristics of water boundary-layer 'wedge' flows for various combinations of pressure gradient and heat transfer. Both the minimum critical Reynolds number and the predicted transition Reynolds number of these 'similar' boundary layers increase as surface temperature increases above the ambient level. The interacting effects of pressure gradient and surface heating on stability and predicted transition may be approximately characterized by a boundary-layer shape parameter. To maintain an extended region of laminar flow, the boundary-layer development should follow a path in which the shape parameter is kept as low as possible over as great a range of Reynolds number as possible.