Suppressed strong reflection surface friction measurement by using shear sensitive liquid in hypersonic flow

Precise surface friction measurement is important in hypersonic flight. Shear sensitive liquid crystal(SSLC) coating technique is an advantage method. However, there are some unsolved problems. Strong reflection occurs when poses and curvature vary. To conquer the challenge, the optical property of SSLC is studied. A novel optics system is designed based on photometry. Specular reflection effect reduces with color reproduction retained. Overexposure phenomena fade away, so we can acquire multiple friction distribution results from the wind tunnel experiment at one time. Experiments were carried out in the hypersonic wind tunnel of China Academy of Aerospace Aerodynamics. The test Mach number is 5.933, and the Reynolds number per unit based on the free-stream conditions is 0.95 × 10⁷ m^-1. In the experiment, the friction resistance was investigated at angles of attack that ranged from 0° to 10°. Results show that the suggested method is able to obtain the friction measurement results while the attack angles change. Compared with traditional means, the efficiency is a threefold improvement. The application range has extended in hypersonic wind tunnel experiments.