Boundary Layer with a Streamwise Pressure Gradient

The presence of a streamwise pressure gradient has a significant effect on the boundary-layer profile and growth. Thus, a flat-plate solution should not be used (except as an approximation) to describe the boundary layer on an airfoil or wing surface, where the results of Chapters 5 and 6 show significant variations in chord – wise surface-pressure distribution, especially with increasing angle of attack.

The effect of a streamwise pressure gradient first is discussed from a qualitative physical viewpoint to fix ideas. Then, similar solutions are explained. These solutions are restricted to pressure gradients that have a particular dependence on streamwise distance; namely, xm. The topic of streamwise pressure gradients concludes with a dis­cussion of integral and numerical methods, both of which can be used for boundary – layer profiles in the presence of arbitrary streamwise pressure distributions.