Accuracy of Direct Skin-Friction Measurements in High-Enthalpy Supersonic Flows

Abstract

Measurement of skin friction and a survey of airflow momentum were conducted in a rectangular straight duct with airflow Mach number, unit Reynolds number, and stagnation enthalpy at the nozzle exit of 2.5, 2.7 x 10 7 m -1 , and 1.1 MJ/kg, respectively. Skin fiction was measured by a direct skin-friction sensor at the test section that was connected to the duct exit, with the state of airflow there also being surveyed. From the result of the measurement and survey at two streamwise locations with different lengths, mean skin friction was calculated by two different and independent methods. The mean skin friction calculated by the directly measured skin friction was compared with that calculated by the momentum conservation law in order to examine the accuracy of direct skin-friction measurement. The accuracy of skin-friction measurement using the direct skin-friction sensor in the test was found to be ±5% (root-sum-square value).