Shear stress measurement of flat plate in incompressible flow based on deformed viscous liquid in cavity

This paper introduces an innovative technique for measuring surface shear stress on a flat plate in incompressible flow, utilizing viscous fluid deformation within a cylindrical cavity. Skin friction forces were initially captured using both hot-wire anemometry and Computational Fluid Dynamics (CFD) simulations across various incoming flow speeds. Thereafter, experiments were conducted in a low-speed closed-circuit wind tunnel to measure viscous fluid deformation using a camera mounted above the wind tunnel test section and a background point at the bottom of the cylindrical cavity. The deformation was quantified by measuring the deflection angle of a light beam passing through the center of the cylindrical cavity containing the viscous liquid. Assuming a fixed proportional relationship between friction and form resistance, the correlation between the deflection angle and shear stress was analyzed, resulting in an exponential fitting formula. Results demonstrate that the proposed method exhibits excellent repeatability, offering an approach for surface shear stress measurement in aerodynamic applications.