Experimentelle und theoretische Untersuchungen zur Instabiliaet und Transition in Hyperschallstroemungen

Abstract

As part of an investigation on hypersonic boundary layer transition, first successful hot-wire and fluctuating pressure measurements have been conducted in the Ludwieg-Tube facility of DLR at Mach number M infinity &#61 5. The disturbance amplitudes (rms-values) of the fluctuations of Pitot pressure and mass flow are smaller than the values measured in conventional, i.e. continuously driven or blowdown type, hypersonic wind-tunnel. Hot-wire measurements in the laminar boundary layer on a flat plate and on a cone in the same wind tunnel at Mach 5 did not show the expected dominance of high-frequency second mode instabilities, as presdicted 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 ratesare in good agreement with theoretical results for three dimensional first mode disturbances.