Abstract: A CFD aided theoretical analysis is reported of the energy exchange and conversion process occurring in the near wakes of bluff bodies in hypersonic flight. The study proceeds by first selecting a point on the Mars atmospheric entry trajectory of the Beagle II spacecraft as the datum case. The freestream values of the pi groups are then varied in a systematic fashion and the flowfield is recalculated in order to discover the underlying dependence on pi groups of the two phenomena of particular interest. The first of these is the presence an aft facing shock in the reverse flow ahead of the aft stagnation point on the body. The second is a newly identified phenomenon of wake flow thermal inversion in which total temperatures in the near wake flow are elevated above those of the freestream by strong viscous coupling of the external flow driving the wake vortex coupled with poor heat transfer out of the wake. Cyclic heating and cooling behavior is examined for closed streamlines in the wake as further evidence of the energy exchange origins of the thermal inversion observed in the computed flows.

Abstract: A computational fluid dynamics (CFD) based dimensional analysis of the flow in the base region of a planetary re-entry configuration is presented. Reynolds number and the free stream Mach number are found to have the dominant influence on the Mach number of the trapped recirculating flow in the wake. Prandtl number is found to have the strongest influence on the temperature of the wake recirculating flow. Two associated flow phenomena, wake reverse flow shock (WRFS) and wake flow thermal inversion are introduced. The governing role of the Prandtl number on the wake flow energy budget and thus the base region heating is discussed.