Abstract:
Effects of different wall temperature conditions on stabilities and transition of three-dimensional hypersonic boundary layer over a flat plate blunt delta wing with large sweep angle are studied by using linear stability theory (LST) analysis. An adiabatic wall case and three isothermal wall cases with wall-to-total temperature ratios of 0.357, 0.714, which are lower than adiabatic case ratio, and 0.952, which is higher than adiabatic case ratio, are considered. The results indicate that the increase of wall-to-total temperature ratio promotes the growth of cross mode and T-S mode disturbances, while suppressing second mode disturbances, which leads to a transition reversal, the
N-factor decreases first and then increases at high temperature ratio (about 0.8 near adiabatic wall condition). The mechanism of the transition reversal is the opposite influence tendency of temperature ratio on different disturbance modes, and the different influence degrees at different locations of delta wing. When there is a low temperature ratio, the increase of ratio mainly affects the second mode near center line of delta wing, resulting in the delay of transition; however, when the ratio is high, it affects cross mode and T-S mode along leading edge more than the second mode near center, which in turn causes the transition to move forward.