Low-Speed Aerodynamics of a Planetary Entry Capsule

Results of an investigation of the global aerodynamic coefe cients and e ow characterization around an Apollostyle capsule model at low speed are presented. Flow features were ascertained quantitatively with laser Doppler velocimetry, digital particle image velocimetry, and hot-wire measurements, as well as qualitatively by e ow visualizations. The study revealed a meandering vortex ring around the capsule, well-organized streamwise vortices whose maximum vorticity increased in the recirculating wake before decaying farther downstream, as well as a complex array ofe ow separation and reattachmentfeatures. A numberofparticularitiesin the e owe eld have been identie ed as potential candidates for triggering the onset of vehicle instability. Based on these e ndings, a modeling approach is proposed.