chapter  12
116 Pages

Viscous Flows and Boundary Layers

This chapter is devoted to real gas flows past bodies with due account for accompanying dissipative effects, such as viscosity and heat conduction, which were neglected in the preceding chapters, with the exception, maybe, of their separate fragments. Bearing in mind, first of all, high-Reynolds-number flows, the emphasis will be placed on boundary layer theory (see Section 1.16) and its generalization to thin shock layers. In the introduction to the main content of the chapter (Sections 12.1 to 12.4) we will give

some elements of the general theory of viscous and boundary-layer flows and present some simple reference problems, which provide useful insight into the role played by dissipative effects in the formation of flows as awhole. Inmore detail, the presentation of these general issues of the theory can be found in books already cited in the introduction to Chapter 1, as well as in the monographs of Schlichting, 1968, and Slezkin, 1960, to name but a few. In the sections devoted to particular questions, the primary emphasis will be made upon

hypersonic flows and, since purely hypersonic effects in viscous flows are associated with the flight at comparatively high altitudes (see Figure 1.2 of Section 1.1), where the laminar flow regime is usually realized, we will focus on precisely this flow regime unless otherwise indicated. As for the few examples of turbulent flows, these will be outlined using the available semi-empirical closure relations without discussing the relations themselves in detail. As in the case of inviscid flows, all basic gas dynamic effects will first be studied with

reference to the example of equilibrium gases, while nonequilibrium flows constitute the subject of Chapter 13. Finally, we will everywhere, except for Section 12.15, mean and consider only two-dimensional (plane and axisymmetric) flows. Unfortunately, the limitations on the volume of the book, as well as the shortage in time, hindered the author from describing in more detail this important division of three-dimensional viscous flows. For the same reason, the boundary layer problems are considered only on an imperme-

able surface, that is, without regard for material melting or evaporation under the action of intense heat fluxes.