CFD Simulations and Wind Tunnel Experiments for Re-usable Launch Vehicles

In the frame of the RETALT project a large number of CFD simulations and Wind Tunnel experiments were made for both the RETALT1 and RETALT2 configurations to better understand the physics and mechanisms of retro-propulsion at supersonic flow conditions. For RETALT1, it was found in both CFD and Wind Tunnel experiments that the flow structure (bow shock stand-off distance, location of the Mach disk) varies linearly with 􏰂(cT ), with cT the thrust coeffi- cient. However, other flow features, as for example the ratio of nozzle exit pressure with the post-stagnation pressure, show a linear dependence on the cT . For RETALT2 a hys- teresis effect was observed in the Wind Tunnel experiments when varying the incidence angle, and a similar behavior was found in the CFD calculations.