Basics of Aerothermodynamics

The basics of aerothermodynamics are treated in this book with special regard to the fact that outer surfaces of hypersonic vehicles primarily are radiation cooled. The implications of this fact are different for different vehicle classes. In any case the properties of both attached viscous and separated flows are of importance in this regard. After a discussion of flight environment and transport phenomena in general, the most important aerothermodynamic phenomena are treated. Thermal surface effects are particularly considered, taking into account both radiation cooling and/or active cooling, for example of inner surfaces. Finally the simulation means of aerothermodynamics are discussed. Computational methods and their modelling problems as well as the problems of ground facility and flight simulation, including the hot experimental technique, are treated.

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The last two decades have brought two important developments for aeroth- modynamics. One is that airbreathing hypersonic flight became the topic of technology programmes and extended system studies. The other is the emergence and maturing of the discrete numerical methods of aerodyn- ics/aerothermodynamics complementary to the ground-simulation facilities, with the parallel enormous growth of computer power. Airbreathing hypersonic flight vehicles are, in contrast to aeroassisted re-entry vehicles, drag sensitive. They have, further, highly integrated lift and propulsion systems. This means that viscous eflFects, like boundary-layer development, laminar-turbulent transition, to a certain degree also strong interaction phenomena, are much more important for such vehicles than for re-entry vehicles. This holds also for the thermal state of the surface and thermal surface effects, concerning viscous and thermo-chemical phenomena (more important for re-entry vehicles) at and near the wall. The discrete numerical methods of aerodynamics/aerothermodynamics permit now - what was twenty years ago not imaginable - the simulation of high speed flows past real flight vehicle configurations with thermo-chemical and viscous effects, the description of the latter being still handicapped by in sufficient flow-physics models. The benefits of numerical simulation for flight vehicle design are enormous: much improved aerodynamic shape definition and optimization, provision of accurate and reliable aerodynamic data, and highly accurate determination of thermal and mechanical loads. Truly mul- disciplinary design and optimization methods regarding the layout of thermal protection systems, all kinds of aero-servoelasticity problems of the airframe, et cetera, begin now to emerge.