Global Stability Analysis of JAXA H-II Transfer Vehicle Re-entry Capsule

The Japan Aerospace Exploration Agency (JAXA) conducted experimental and numerical investigations on the H-II Transfer Vehicle Re-entry (HTV-R) capsule and showed the existence of strong self-excited oscillations at an angle of attack of 20 degrees and Mach 0.4. The present work aims at performing fully three-dimensional global stability analysis on the HTV-R capsule to characterize its wake dynamic instabilities. An implicit pseudo-unsteady approach at high Courant-Friedrichs-Lewy (CFL) number is used to obtain a Reynolds-Averaged-Navier-Stokes (RANS) solution. Separation occurs on the capsule shoulder and a large steady planar-symmetric recirculation bubble appears. The RANS solution is used as baseflow for the global stability and the leading eigen-modes are calculated by coupling a time-stepper technique to an Arnoldi algorithm. A globally unstable mode is found at a non-dimensional frequency of 0.161. Both frequency and spatial structure of the global mode correspond to the dominant hairpin-like vortex shedding mode found by Ohmichi et al. [1] using Dynamic Mode Decomposition (DMD). No evidence of the other two dominant DMD modes, associated with helical vortex shedding and low-frequency recirculation bubble breathing, was found by the global stability analysis.