Fiber optic pressure/skin friction gage for supersonic flow applications

A fiber optic skin friction gage has been developed for supersonic flow applications. Experimental results for a Mach 3 2-D flow are presented. Accuracy within 5% was attained. Also presented is a fiber optic combined pressure/skin friction gage for similar environments. The skin friction balance design is a non-nulling cantilevered beam with a sensing head attached to the end and is similar to other designs previously constructed by Schetz and his graduate students. The sensing head is aligned with the plane of the wall so that it is exposed only to the shear force. The cantilever beam deflects under the load due to the shearing force, and the resulting strain can be measured. In previous designs, either foil or semiconductor strain gages have been used. Fiber optic gages offer to increase resolution while substantially reducing temperature sensitivity