Elastic Films for Cyrogenic Skin Friction Measurements

Here we introduce a new sensor for measurement of skin friction and pressure, Surface Stress Sensitive Film (S3F). This technique can operate over a range of temperatures from cryogenic (160 K, -113„aC) to well above ambient (470 K, 197„aC). The operation of the sensor is based on the deformations of an elastic film that distorts under the action of the applied normal and tangential loads. Skin friction and pressure gradients are determined by monitoring these distortions and applying a finite element model to the film. Quantitative measurements of skin friction and pressure have been demonstrated on aerodynamic models from 10-m/s to Mach 5. Among these tests was an experiment that included S3F on one side of the model and PSP on the other side. Data from each sensor was acquired simultaneously, thus demonstrating the compatibility of the S3F with existing PSP hardware. Tunnels with existing PSP systems could be upgraded to include skin friction capability. The opportunity to develop this sensor system for measurements of skin friction in production facilities, including cryogenic tunnels as well as tunnels with operating temperatures up to 200C, is recognized and this is the focus of this proposal.