Computational study of aerodynamic characteristics on reentry capsule aft-body shape in transonic flow

Pitching moment characteristics and the flow field around blunt-body reentry capsule at transonic speeds were studied by computational simulation using three different model shapes. Dynamic instability such as pitching oscillation greatly influences the flight control and landing accuracy of a capsule, hence understanding the flight characteristics is an important challenge. In this study we focused on the influence of flow reattachment on the aft-body, and performed steady RANS calculations using the fast unstructured-grid flow solver “FaSTAR” developed by JAXA. The effect of aft-body shape was investigated by comparing the resulting differences in pitching moment coefficient and flow field. The results showed that as the pitching moment coefficient trend changed significantly for capsule shapes with shallow aft-bodies. It was possible to see from examining the flow visualization results that there were notable differences in the flow separation and reattachment on the upper side of the capsule, and the upper side of the recirculation region due to the difference in the shape of the aft-body. It is suggested that these differences influenced the pressure distribution and thus the pitching moment characteristics.