Overview

At the begin of Chapter 6 we have noted that in the hypersonic flight domain, like in the lower speed regimes, flow fields can be separated into inviscid and viscous portions. At large altitudes, in general at the limit of the continuum regime, this separation becomes questionable. However, the central topic of this chapter is attached viscous flow, whose basic properties we describe with help of the phenomenological model "boundary layer".

We look first at the typical phenomena arising in viscous flows and at their consequences for aerothermodynamic vehicle design. Attached viscous flow is characterized, in general, by the molecular transport of momentum, energy and mass, Chapter 4, towards the vehicle surface, with wall-shear stress, the thermal state of the surface, thermo-chemical wall phenomena, et cetera, as consequences. We treat the boundary-layer equations, consider their limits in hypersonic flow, examine the implications of radiation cooling of vehicle surfaces, and define integral properties and surface parameters, including viscous thermal-surface effects. Finally we give simple relations for laminar and turbulent flow, with extensions to compressible flow by means of the reference temperature/enthalpy concept, for the estimation of boundary-layer thicknesses, wall-shear stress, and the thermal state of a surface (wall heat flux and wall temperature) for planar surfaces, spherical noses and cylindrical swept edges. A case study closes the chapter.

Laminar-turbulent transition and turbulence in attached viscous flow, which we have to cope with at altitudes below approximately 40.0 to 60.0 km, are considered in Chapter 8. We discuss there the...