Low-speed aerodynamics of a planetary entry capsule

Results of an investigation of the global aerodynamic coefficients and flow characterization around an Apollo-style capsule model at low speed are pre sented. Flow features were ascertained quantitatively with laser Doppler ve locimetry, digital particle image velocimetry, and hot-wire measurements, a s well as qualitatively by how visualizations. The study revealed a meander ing vortex ring around the capsule, well organized streamwise vortices whos e maximum vorticity increased in the recirculating wake before decaying far ther downstream, as well as a complex array of flow separation and reattach ment features. A number of particularities in the flowfield have been ident ified as potential candidates for triggering the onset of vehicle instabili ty. Based on these findings, a modeling approach is proposed.