Hypersonic Boundary-Layer Transition Experiments in Ludwieg Tube

Hypersonic boundary layer laminar/turbulent transition is one of the most difficult and prevalent problems in hypersonic vehicle design. To lower the requirement of experiment research on hypersonic boundary layer instability and transition, a Mach 6 hypersonic wind tunnel was designed and constructed based on the Ludwieg tube principle. This research focused on the starting and operating processes of Ludwieg wind tunnel using the numerical method. The influence of the bending storage section on flow quality in test section was analyzed. Thereafter, the static and dynamic characterizations of the hypersonic flow in the test section of hypersonic wind tunnel were carried out. The design Mach number of the wind tunnel was verified, and the dynamic disturbance characteristics were given. Finally, the experimental investigation on hypersonic boundary layer transition was carried out based on the 7° half-angle sharp cone model. The instability waves were obtained by the high frequency PCB pressure sensors which were flush mounted on the cone surface, and the evolution characteristics of unsteady waves in hypersonic boundary layer were analyzed. This study indicates that Ludwieg tube wind tunnel has advantages such as low construction and operation cost, high operation efficiency and good flow field quality compared with conventional hypersonic wind tunnel, and it is extremely suitable for fundamental experimental research such as hypersonic boundary layer transition.