The wake flow of finned cylindrical afterbodies aligned with a Mach number 2.0 air streamis studied in the wind tunnel and also by numerical simulations. Pressure measurements forspinning straight-finned afterbodies show a base pressure dependency on the spin rate. Whilefor low spin rates the base pressure increases, it decreases again for higher spin rates. Particleimage velocimetry shows a fundamental change in the flow field for non-spinning surrogatemodels introducing a swirling motion by canted fins. A counter-rotating circumferentialvortex pair is formed due to the streamwise swirling motion. The direction of the flow directlyat the base and on the axis of symmetry changes and the base pressure decreases up to anorder of magnitude. Higher swirling rates lead to an annular separation line on the baseindicating another change in the wake flow structure. In the far wake a region of low upstreamdirected velocities is formed.
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