Numerical Investigation of Supersonic Oscillatory Flow with Strong Interference over a Capsule-shaped Abort System

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The flow past a capsule-shaped space transportation system (STS) is numerically analyzed using computational fluid dynamics (CFD) for different free stream Mach numbers ranging from 1.2 to 5.0, where a capsule is modeled by a cone, and a rocket by a circular cylinder. The objective of this research is to study Mach number effects on phenomena of the supersonic aerodynamic interference with periodic flow oscillations at supersonic regime. So far we have considered two models: model A (without disk) and model B (with disk). It was found from experimental and computational results that the flow around model A becomes steady, where aerodynamic interaction is not observed, while in model B, flow becomes unsteady with periodic oscillations. This flow oscillation is considered to be a potentially high risk in separation of the capsule and rocket. Therefore, the present study focuses on the unsteady case of model B. Numerical results at M=3.0 compared well with experimental ones, which validates the present CFD. Time-averaged results are employed to see the whole trajectories of shock waves and the variation in amplitude of flow oscillation during one cycle. Moreover, a fence is proposed as a device to suppress the flow oscillation.