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Supersonic Wake Flow Analysis of Finned Projectile Afterbodies at Various Spin Rates
Abstract
The wake flow of finned cylindrical afterbodies aligned with a Mach number 2.0 air stream is studied in the wind tunnel and also by numerical simulations. Pressure measurements for spinning straight-finned afterbodies show a base pressure dependency on the spin rate. While for low spin rates the base pressure increases, it decreases again for higher spin rates. Particle image velocimetry shows a fundamental change in the flow field for non-spinning surrogate models introducing a swirling motion by canted fins. A counter-rotating circumferential vortex pair is formed due to the streamwise swirling motion. The direction of the flow directly at the base and on the axis of symmetry changes and the base pressure decreases up to an order of magnitude. Higher swirling rates lead to an annular separation line on the base indicating another change in the wake flow structure. In the far wake a region of low upstream directed velocities is formed.