An assessment of the hypersonic Ludwieg Tube of Delft University of Technology (Hypersonic Test Facility Delft, HTFD) is given. The facility is discussed theoretically and an experimental evaluation is performed to infer the facility performance. Experiments are performed using conventional techniques such as static and total head pressure measurements and Fay-Riddell heat flux evaluations by means of infrared thermography. Furthermore PIV (particle image velocimetry), a more state of the art technique is used to deduce nozzle boundary layer parameters as well as the free stream flow field and the static and total temperature for the Mach 7 nozzle. Finally for the Mach 9 nozzle, stagnation heat flux measurements were performed to obtain the total temperature of the flow.
In the framework of the NATO-RTO-AVT-WG10 entitled "Technologies for Propelled Hypersonic Flight", base flow test cases have been selected for code validation. Concerning the first dataset devoted to base flowplume interaction at moderate nozzle pressure ratios, the influence of numerical discretization technique and turbulence models are discussed. The multi-dimensional upwind (MDU) discretization technique on unstructured grids applied to the axisymmetric base flow model with an underexpanded jet predicts base pressures that are consistently lower than the experimental values. If no proper conclusions can be drawn from this comparison because of the 3-D model support influence in the experiments, conclusions in relation to the turbulence models and to the axisymmetric results of the other code, the finite-volume technique on multiblock grids (LORE), may be of interest. Concerning the second dataset of a boattailed afterbody flowfield with plume-induced-separation, RANS calculations with transport equations turbulence models reproduce the general organization of the flow, in particular the free separation phenomenon with a X-shock system induced by the jet/external flow interaction. The afterbody wall-pressure profile on the cylindrical part and during the expansion wave is well restituted. But it seems difficult to predict accurately the afterbody wall-pressure profile on the boat-tail because turbulence models have difficulties to reproduce positive pressure gradients. Calculations do not reveal the existence of a singular reflection on the symmetry axis for the recompression barrel shock of the propulsive jet, with a Mach disc, as it has been experimentally observed.
The asymptotic flow structure is considered for a viscous–inviscid conical interaction, in particular that between a swept shock wave and a boundary layer. A flow model is devised based on the three-layer interaction concept. Assuming conicity of the inviscid flow regions, a viscous layer structure is established that is compatible with the inviscid outer flow, and which produces a geometrically conical surface flow pattern. This result is obtained from a dimensional analysis, which reveals similarity of the viscous layer in cross-flow planes at different radial distances from the conical origin. The results of this analysis provide a tool for the quantitative interpretation of surface flow visualizations in terms of the related topological structure of the flow in the cross-flow plane. This method is illustrated by application to the surface flow visualization of a Mach 3 shock-wave/boundary-layer interaction.
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