Planar and Conical Boundary Layer Stability Experiments at Mach 5

Kurzfassung

As part on an investigation on hypersonic boundary layer transition, first sucessful hot-wire and fluctuating pressure measurements have been conducted in the Ludwieg-Tube facility of DLR at Mach number M infinity = 5. The distrubance amplitudes (rms-values) of the fluctuations of Pitot pressure and mass flow are smaller than the values measured in conventional, i.e. continuoulsy driven or blowdown type, hypersonic wind-tunnels. Hot-wire measurements in the laminar boundary layer on a flat plate and on a cone in the same windtunnel at Mach 5 did not show the expected dominance of high-frequency second mode instabilities, as predicted by linear stability theory and found in other experiments. However, the growth of natural disturbances within a broad frequency band up to 50 kHz could be observed on the flat plate. The measured amplification rates are in good agreement with theoretical results for three dimensional first mode disturbances.