Abstract
New method and means are proposed to measure the skin friction force on an aerodynamic surface based on elastic deformations of silicon rubber and gel coatings. Object is coated by elastic polymeric film with known shear modulus. The displacement of coating is calculated from the correlation of two images between wind-on and wind-off. We conduct the theoretical analysis for the elastic polymer film and propose the material properties of the coatings required to measure the surface skin friction in the wide range of flow speed. There are two ways to calibrate the skin friction force to the displacement of coatings. These methods are tested and compared to quantitative skin friction force measurement. The skin friction over the plate is measured using this technique in various Reynolds number. The hot wire measurement is conducted to validate this technique. The time averaged measurements of this technique are in good agreement with the traditional results. However, the unsteady characteristics of surface skin friction are not captured by the lack of time resolution of the CCD camera.
