Measurement and visualization of surface friction beneath jet flow over planar surface using liquid crystal coatings

The ability of Shear Sensitive Liquid Crystal （SSLC） coatings to measure and visualize surface friction fields is studied. Liquid crystal coatings are used to measure surface friction beneath the subsonic jet flow over a planar surface at various jet velocities, and to visualize unsteady surface friction fields of supersonic jet flow with shock cells. Experimental study shows that in terms of quantitative measurement, a single liquid crystal coating is able to measure surface friction rapidly with a high resolution and a wide range, and is also suitable for studying the variation of surface friction with the jet flow velocity. In the aspect of flow visualization, liquid crystal coatings provide another way for visualizing the flow field structures such as diamond shock cells of the supersonic jet flow and the unsteady characteristics of the shock cells.