Influence of pressure gradient upon boundary layer stability and transition

Summary The present paper deals with the effect of adverse pressure gradient on boundary layer stability and transition in an incompressible fluid qualitatively as well as quantitatively. In order to produce various kinds of pressure gradients along a flat plate located horizontally, the cross sectional area of the working chamber is varied by the vertical side walls. Changes in velocity profiles and in intensity of streamwise velocity fluctuation in a boundary layer are measured in the transition region. The distribution of dynamic pressure at 0.43 mm from the surface is correlated with that of intensity of velocity fluctuation. Moreover, transition length is correlated with a shape parameter. Further, the process of transition is shown to be different from the case of zero pressure gradient when the half included angle is 3.6 degree. Finally, mention is made of the relation between transition Reynolds number and a characteristic frequency from the standpoint of linear stability theory.With 11 Figures