| Popis: |
The primary experiment for HIFiRE-1 was to measure boundary-layer transition in hypersonic flight on a 7 degree half-angle, axisymmetric cone with a 2.5 mm radius bluntness. A secondary experiment measured mean and fluctuating pressure, and heat transfer on a cylinder-33-degreee-flare geometry. The ascent provided smooth-body, low angle-of-attack, boundary-layer transition at Mach numbers greater than 5. The end of turbulent-to-laminar transition occurred at Reynolds numbers between 10.3 to 12.2 million. Second-mode N-factors of approximately 14 correlated transition. A diamond-shaped trip retained turbulent flow until reaching a roughness Reynolds number Rekk = 2200. During re-entry, transition was measured around the circumference of the cone at Reynolds numbers ranging from 3 million on the leeside to 5 million on the windward side. In the shock-boundary layer interaction, maximum sound pressure levels of 173 dB were recorded upstream of the flare, and 185 dB on the flare itself. The principal goal of HIFiRE-5 was to measure hypersonic boundary layer transition on an elliptic cone. The second stage booster failed to ignite, so the experiment reached a maximum Mach number of only 3. Nevertheless, supersonic pressure and temperature data were obtained under laminar and turbulent flow, and flight systems were validated. Traveling and stationary crossflow instabilities were clearly measured for HIFiRE-5 in ground test in a quiet flow tunnel. The frequency, phase speed, and wave angle were all in good agreement with computations. |
