Skin friction measurements in short duration high enthalpy flows
1995, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. An experimental study was carried out to directly measure skin friction in a SCRAMjet model in an impulsive, high enthalpy test facility. A force measuring device consisting of a miniature, plastic, cantilever sensor with strain gages at the beam base was mounted in both the inlet ramp and combustor chamber of a SCRAMjet model at the NASA Ames 16" shock tunnel facility. The engineering plastics utilized allowed for high frequency response and high shear sensitivity with low specific gravity, low thermal conductivity, and low manufacturing cost. The gages were designed such that high temperature gradients would not contaminate the results until after the tunnel test time. Variations to the gage both increased durability and reduced maintenance times and also explored the sensitivity-time response design space. Tests at the 16" Shock Tunnel facility simulated true Mach 12-14 enthalpy conditions with reservoir Pt = 4700 psi and Tt = 10000 R and local Mach numbers on the order of 6. Measured wall shear values agreed well with predictions from theory.