Development of pulse-type skin friction balance use in shock tunnel

The wall shear stress significantly affects the aerodynamic characteristics and flight safety of hypersonic aircraft. More accurate and reliable diagnostic instruments are required to fully understand and optimize the distribution of wall shear stress in hypersonic high-enthalpy flow. Two types of assembled and integrated skin friction balances for high-enthalpy impulse facilities were developed. The integrated balance was processed using additive manufacturing, also known as 3D printing. The static calibration uncertainty of the two types of skin friction balances is lower than 0.2% FS at 95% confidence. The first-order vibration frequency is about 50 Hz. The applicability and reliability of the developed skin friction balance were verified in the JF-12 shock tunnel built by the Institute of Mechanics, Chinese Academy of Sciences. A series of wall shear measurement tests for flat-plate boundary layers were carried out, in a freestream with a nominal Mach number of 7 and a unit Reynolds number of about 106. The wall shear results were in good agreement with the numerical simulation and empirical formula results. The minimum deviation can reach 3.67% of the measured value, which verifies the applicability and reliability of the two types of skin friction balances for accurate wall shear stress in high-enthalpy pulse flow, especially providing experimental support for the feasibility of the additive-manufactured balance.