Fundamentals of Aerodynamics 2024, 49: Elements of Hypersonic Flow

In hypersonic flow, the generated shock layer tends to be much thinner than at supersonic flows. Interaction between inviscid flow behind the shock and the viscous boundary layer of the surface is much stronger. In practice, hypersonic travel is applied mostly in large heights, meaning that the medium has relatively low density, and hence a low Reynolds number and thick boundary layers. When the boundary-layer is about as thick as the shock-layer, the shock layer might be fully viscous, and viscous interaction phenomena might end up affecting the surface pressure distribution. In hypersonic flow the shock layer is also at high temperatures, leading to aerodynamic heating of the foil. The gas around the body may even form a partially ionized plasma, introducing free electrons. Heat transfer to the body is a regular matter of thermal conduction at its surface, which is in contact with the shock layer at some temperature. The process is referred to as "convective heating". Like usual, the heating effect is dominated by the blackbody radiation component.

The deflection angle of the streamlines is expected to be pretty shallow, while the shock cone follows a straight line. This makes the model simple enough to analyse with using Newtonian methods

In modified models, the pressure coefficient carries a normalization constant, instead of a 2.

For oblique shock waves, in a perfect caloric gas, the shock relation and angle is known. Using quantities from the subsonic cases,

For the Newtonian case, replace the subscript 1 in the ratios with ∞. The energy transfer through aerodynamic heating is given by

As the ratio of drag coefficient and skin friction drag is very small for blunt bodies, hypersonic travels tend to dissipate heat better for hypersonic travel.