極超音速境界層遷移における 2 次モード波の非線形共鳴成長

抄録

Non-linear growing process of surface pressure fluctuation in the hypersonic boundary layer was studied. A 1100mm-length 7-degree half angle cone was applied for the series of experiments conducted in the high-enthalpy shock tunnel JAXA-HIEST. On the surface of the cone, sixteen high-speed pressure transducers-PCB132A were flush mounted from x=412mm (CH1) to x=1012mm (CH16) each 40mm apart (x shows the distance from the nose). Surface pressure fluctuations in the boundary layer on the cone was measured under the high-enthalpy condition (H₀=3MJ/kg), in which Reynolds number was 2.4x10⁶. The typical surface pressure histories depicted low-frequency (around 10kHz) Tollmien-Schlichting wave and extremely high-frequency (around 450kHz) 2^nd mode waves. To determine the resonant interaction of the 2^nd mode wave and other low frequency waves, cross-bispectrum analysis was applied. The analysis showed that a significant bispectrum coefficient was found at around 10kHz and around 450kHz, which result meant that there was a notable phase coupling between 2^nd mode wave and a low frequency wave, which frequency was identified to the Tollmien-Schlichting wave.