Study On Flow Field And Heat Protection Of An Opposing Jet

Aircrafts or reusable space vehicles will encounter severe aerodynamic heating when flying at supersonic speed. Opposing jet thermal protection is an ideal method for use in the future reusable spacecrafts due to its reusable characteristics and good performance. But the nose flow field becomes very complex after the joint of an opposing jet, which makes it more difficult to predict the wall heat flux and calculate the aerodynamic forces. Based on previous tests of opposing jet, following contents are mainly studied in this paper:1) The opposing jet flow field of the test model is simulated by numerical method. And the effects of jet control parameters to heat reduction are qualitative researched at a given jet flow-per-second. Jet control parameters include: Mach number at jet exit, the total temperature and diameter of nozzle. According to different flow field structure characteristics under different situations, conditions of obtaining stable flow are derived in theory.2) The opposing jet thermal protection of a two-dimensional wedge board is studied, and the effects of angle of attack and the chemical reaction are taken into account. The results show that: the opposing jet flow is still stable in a small angle of attack, but Mach disk is in the shape of a small tilt; wall heat flux can be calculated without necessity of taking chemical reaction into account.3) The oscillations of stable and unstable flow are numerically studied based on the turbulence effect for the first time, and the oscillation mechanism is discussed in this paper. It is pointed out that the time-averaged algorithm is needed when an opposing jet flow is numerically studied, even for stable flow, and flow parameters should be averaged in at least one cycle of oscillation. The time-averaged density contours obtained in numerical simulation are in good agreement with schlieren photographs, the wall heat flux predicted at this time is fairly coincide with experiment result. It shows that wall heat flux can be predicted successfully only when the flow field structure is simulated correctly.