Design and preliminary freestream calibration of HUST Φ 0.5 m Mach 6 Ludwieg tube wind tunnel

Hypersonic wind tunnels are essential in the fundamental research of hypersonic aerodynamics. However, the low operating efficiency, low flow-field quality, and high construction and operating costs of conventional hypersonic wind tunnels make delicate experimental investigations difficult. This paper aims to design a low-cost and large-diameter research-oriented hypersonic wind tunnel based on a Φ 0.5 m Mach 6 Ludwieg tube. The design of the storage tube, fast-opening valve, and Laval nozzle is analyzed using numerical simulations, particularly emphasizing the unsteady starting process of the Ludwieg tube tunnel with a bent storage tube. Preliminary freestream calibration of the Ludwieg tube is also conducted. Results show that the hypersonic Ludwieg wind tunnel controlled by the fast-opening valve can obtain high flow quality in the test section. The bent storage tube slightly affects the propagation intensity of the expansion waves locally. However, it does not affect the propagation speed of expansion waves within the storage tube and the freestream quality in the test section. The Mach number distribution in the test section is reasonably excellent. The Pitot probe results show that the intensity of freestream pressure disturbances is lower than in similar facilities in Germany and UAS. The wind tunnel, therefore, shows promising potential in experimental studies of hypersonic aerodynamics. Hopefully, this study will shed light on constructing a low-cost, research-oriented hypersonic wind tunnel.