Boundary-layer instability experiments in a tandem nozzle supersonic wind tunnel

The mechanism of laminar-turbulent boundary-layer transition in high-speed flow, particularly in supersonic flow, is still incompletely understood despite significant progress has been made since the past few decades. In order to obtain deep insight of boundary-layer transition mechanism in supersonic flow regime, a collaboration study based on experimental investigation and numerical calculation is conducted in this dissertation. A new Tandem Nozzle Mach 3 Wind Tunnel is designed and manufactured based on the infrastructure of the existing Mach 6 Ludwieg. By introducing an extra nozzle and a settling chamber, the desired supersonic flow can be achieved. Based on the theoretical and numerical design, the Mach 3 wind tunnel is built. The wind tunnel calibration is performed next for both mean and fluctuating flow. Afterwards the instability wave on a 7° half-angle sharp cone model with zero angle of attack in Mach 3 supersonic flow is studied, both numerically and experimentally. The linear stability theory is applied to the basic flow to predict the property of instability wave. Later, the instability experiments are performed using PCB sensors and hot-wire anemometry. The PCB sensors are surface mounted to capture the pressure fluctuations along the cone model, whereas the hot-wire probe is traversed through the boundary-layer of the cone flow at different axial stations. The instability waves ranging from 17 kHz to 50 kHz are observed with both instruments. They are quantitatively characterized and compared with the numerical calculation, and good agreement is achieved. Eventually, the critical N-factor is also estimated for the sharp cone in present tunnel.