Experimental and numerical investigation of the turbulent wake flow of a generic space launcher configuration

Abstract

The turbulent wake of a generic space launcher at cold hypersonic freestream conditions is investigated experimentally and numerically to gain detailed insight into the intricate base §ow phenomena of space vehicles at upper stages of the §ight trajectory. The experiments are done at Ma ∞ = 6 and Re D = 1.7 · 10 6 m −1 by the German Aerospace Center (DLR) and the corresponding computations are performed by the Institute of Aerodynamics Aachen using a zonal Reynolds-averaged Navier Stokes / Large-Eddy Simulation (RANS/LES) approach. Two di¨erent aft-body geometries consisting of a blunt base and an attached cylindrical nozzle dummy are considered. It is found that the wind tunnel model support attached to the upper side of the main body has a nonnegligible impact on the wake along the whole circumference, albeit on the opposite side, the e¨ects are minimal compared to an axisymmetric con¦guration. In the blunt-base case, the turbulent supersonic boundary layer undergoes a strong aftexpansion on the model shoulder leading to the formation of a con¦ned low-pressure (p/p ∞ ≈ 0.2) recirculation region. Adding a nozzle dummy causes the shear layer to reattach on the its wall at x/D ∼ 0.6 and the base pressure level to increase (p/p ∞ ≈ 0.25) compared to the blunt-base case. For both con¦gurations, the pressure §uctuations on the base wall feature dominant frequencies at Sr D ≈ 0.05 and Sr D ≈ 0.2 0.27, but are of small amplitudes (p rms /p ∞ = 0.02 0.025) compared to the main body boundary layer. For the nozzle dummy con¦guration, when moving downstream along the nozzle extension, the wall pressure is increasingly in §uenced by the reattaching shear layer and the periodic low-frequency behavior

Propulsive jet influence on generic launcher base flow

“…This peak is found by several authors [6,10,15,19]. For hypersonic base flows Statnikov et al [25] and Saile et al [28] found similar peaks. With jet flow we obtained an additional peak at higher Strouhal numbers.…”

“…The results with jet shows additional high frequencies information. Statnikov et al [25,26] performed numerical flow analysis of the wake of a generic launcher model at M = 6 including dynamic mode decomposition analysis. Using this analysis they associated dominating frequencies to wake flow phenomena, i.e., longitudinal pumping of the cavity, a swinging mode of the shear layer and a radial flapping motion of the shear layer.…”

Mach number dependence of Spectral Character of Unsteady Pressure field on Axisymmetric Backward Facing Step: Transonic Flows

“…Pain et al [13] noticed that its influence is felt in the regions close to the separation and mean reattachment points, whereas Kiya and Sasaki [42] observed it close to the separation point and relate the vertical motion of the shear layer to the streamwise oscillations of the instantaneous reattachment point. However, Saile et al [20] and Statnikov et al [21][22][23] relate the low frequency to the motion of the large vortices within the recirculation bubble. In the current study, the low-frequency broadband peak attains its maximum amplitude at x/H=3.38, which is neither close to the separation nor the reattachment points.…”

“…2). Statnikov et al [22][23] associated these frequencies with the vortex motions within the recirculation bubble. Cherry et al [45] stated that the low frequencies scale well with the length of the recirculation bubble, or the mean reattachment length.…”

“…The peak at Sr D =0.192 is linked to the coupled effect of the pulsatile motion of the recirculating fluid and the recompression shock motion. Statnikov et al[22][23] performed an experimental and computational study of the flow over an axisymmetric afterbody with and without a dummy nozzle at M ∞ =6. The presence of the nozzle enhanced the base pressure compared to the no-nozzle afterbody.…”