ABSTRACT
It was pointed out in Chapter 5 that the equations that result from the boundary-layer (or thin-shearlayer) approximation provide a useful mathematical model for several important §ows occurring in engineering applications. Among these are many jet and wake §ows, two-dimensional (2-D) or axisymmetric §ows in channels and tubes, as well as the classical wall boundary layer. Certain three-dimensional (3-D) §ows can also be economically treated through the boundary-layer approximation. In addition, methods have been developed to extend the boundary-layer approximation to §ows containing small regions of recirculation. Often, a small region exists near the streamwise starting plane of these §ows in which the thin-shear-layer approximation is a poor one, but for moderate to large Reynolds numbers, this region is very (and usually negligibly) small.
