Extended abstract of the dissertation "Experimental characterization of turbulent wake of generic space launcher" In this thesis the influence on the turbulent wake of a generic space launcher model due to the presence of an underexpanded jet is experimentally investigated. Wake flow phenomena represent a significant source of uncertainties in the design of a space launcher. Especially critical are dynamic loads on the structure. The wake flow is investigated at supersonic (M∞=2.9) and hypersonic (M∞=5.9) flow regimes. The flow topology is described by Schlieren visualization, mean-pressure and PIV measurements. Furthermore RANS simulations of the wind tunnel model are performed. For physics-based jet simulation, two major afterbody flow mechanisms are important. One mechanism is flow displacement by plume shape. The plume shape affects the positions of the shear layer and the plume shock. It mainly depends on the ratio of nozzle exit pressure to static pressure in the freestream. The second mechanism is flow entrainment into the plume. The entrainment describes the effect of the shear layer to entrain gas from the base flow. The jet flow is simulated using air and helium as working gases. Due to the lower molar mass of helium higher jet velocities are realized and therefore velocity ratios similar to space launchers can be simulated. The degree of underexpansion of the jet is moderate for the supersonic case (pe/p∞≈5) and high for the hypersonic case (pe/p∞≈90). Unsteady pressure measurements are performed to describe the dynamic wake flow. The influences of the underexpanded jet with different jet velocities are reported. A peak compared to the wellknown “shedding” at the base near Strouhal number StD≈0.25 was observed. Peaks related to longitudinal pumping, swinging and radial flapping motion of the shear layer are found, based on published numerical flow analysis. In hypersonic flow regime by the present of an air jet the fluctuation level increase on the base for Strouhal numbers above StD≈0.75. On the other hand with helium jet distinct peaks at higher frequencies are found. The peaks at higher frequencies indicate a high-energy motion of the shear layer and is attributed to the interactions between external and jet flow. Comparing the PIV measurements, the jet influence on the mixing area between the external and jet flow clearly appears at the end of the nozzle. The air jet reduces the Reynolds stresses at the end of the nozzle, which indicates a stabilization of the flow. Due to the influence of the heated helium jet, the area with increased Reynolds stresses increases further. Additional this area extends into the mixing layer between the helium jet and the external flow. The results show that, in addition to the displacement effect of the jet plume, the turbulent mixing between the jet plume and the external flow is important for the physically based investigations of base flows. The underexpanded jet and the degree of underexpansion have a major influence on the base flow topology. The variation of the jet velocity has an influence on the dominant frequencies of the pressure fluctuations in the wake area. In particular, the results of the Reynolds stresses show the need for physics based jet simulation in order to investigate the unsteady base flow.weiterlesen