Investigation of mach 10 boundary layer stability of sharp cones at angle of attack, part 1: Experiments
The boundary layer transition and stability characteristics of sharp cones at angle of attack are investigated with measurements at Mach 10 in the Arnold Engineering Development Complex (AEDC) Hypervelocity Wind Tunnel 9 on a 1.5 m long, 7 deg cone at unit Reynolds numbers between 1.8 and 15 million per meter. The transition location is determined with coaxial thermocouples and temperature sensitive paint, and stability measurements are obtained using high frequency response pressure sensors. The measurements are used to validate the STABL 3D linear stability theory (LST) code at angles of attack up to 6 deg. The computations are found to reproduce the experimental trends regarding the effect of angle of attack on the growth of 2 mode waves. The amplitude of the 2 mode waves near breakdown on the leeward and windward meridians scale linearly with edge Mach number. The initial amplitudes estimated using linear stability computations are found to scale with Pitot noise in the unstable 2 mode frequency band. Linear stability computations along with the ability to correlate initial 2 mode amplitudes to tunnel noise and to correlate maximum 2 mode amplitudes to edge Mach number enables the use of Mack's amplitude method to predict 2 mode transition. This methodology is investigated to accurately predict sharp cone boundary layer transition at 0 deg AoA. Extension to sharp cones at angle of attack is expected to be straightforward.