Computation of the hypersonic heat flux with application to small launchers

Abstract

The paper focuses on the computation of the heat flux across a small launcher fairing using both CFD analyses and analytical formulations. The thermal loads must be assessed to correctly dimension the thermal protection system; high flow temperatures and wall heat fluxes mainly appear in the high supersonic and hypersonic flow regimes. The effects of different mathematical models for hypersonic flows over the fairing are numerically investigated and compared in order to provide information that can be used for future analyses. Among the physical models employed, the current work focuses on the effects of air dissociation and turbulence on the wall heat flux. At the high Mach numbers and high temperatures encountered after the shock wave the air begins to dissociate and thus the necessity of employing a chemical reactions model is studied. It is important to mention that the reactions that are associated with the air dissociation are endothermic, thus lowering the heat flux. Since a turbulence model implies a high mixing capacity of the flow (transporting the energy and reaction products) it is expected to have a high impact on the distribution of the heat flux. Sometimes the interaction of the dissociation model with the turbulence model is of large significance since the two can have opposite effects. For the zero angle of attack cases, analytical models, axisymmetric and full 3D flows using CFD are performed, while for non-zero angle of attack, only the 3D CFD modelling is used.