Viscous Effects in External Flows

The analysis we have carried out so far are such that viscosity did not make a direct appearance. Then the potential flows we considered in the previous Chapters were inviscid, i.e., we deliberately ignored viscosity. In reality these flows are theoretical. we saw in the case of flow about a cylinder how viscosity alters the flow completely aft of the cylinder and its consequences. Any real flow in nature is viscous. In fact, it is viscosity that makes the flow interesting and of course challenging to understand and calculate. It is viscosity that gives rise to many of the interesting physical features of a flow. One other area that makes a flow exciting even though inviscid is that of compressible flow.

The birth and development of a Boundary Layer, its transition, the way a flow handles a pressure gradient and a possible separation are some of the topics we consider in this chapter. We postpone any discussion of the calculation procedures to later chapters and deal with only qualitative features at present.

(c) Aerospace, Mechanical & Mechatronic Engg. 2005
University of Sydney