The Experiments and Stability Analysis of Hypersonic Boundary Layer Transition on a Flat Plate.

Experimental and linear stability theory (LST) investigation of boundary layer transition on a flat plate was conducted with a flow of Mach number 5. The temperature distributions and second-mode disturbances on the flat plate surface at different unit Reynolds number (Re_unit) values were captured by infrared thermography and PCB technology, respectively, which revealed the transition location of the flat-plate boundary layer. The PCB sensors successfully captured the second-mode disturbances within the boundary layer initially at a frequency of about 100 kHz, with a gradually expanding frequency range as the distance travelled downstream increased. The evolution characteristics of the second-mode instabilities were also investigated by LST and obtained for the second mode, ranging from 100 to 250 kHz. The amplitude amplification factor (N-factor) of the second-mode instabilities was calculated by the e^N method. The N-factor of the transition location in the wind tunnel experiment predicted by LST is about 0.98 and 1.25 for Re_unit = 6.38 × 10⁶ and 8.20 × 10⁶, respectively. [ABSTRACT FROM AUTHOR]