Panoramic diagnostics of shear stresses on the channel wall with a step using the liquid crystals

Abstract

Measurements results on the shear stresses of surface friction by means of thin-film coatings based on cholesteric liquid crystals and specialized software for digital processing of experimental video are presented in the paper. The calibration dependencies of shear stress relative to the hue and azimuth angle as well as shear stress spatial distribution at subsonic turbulent flow (V_∝ = 84 m/s) around a step, trapezoidal in plane (Reynolds number calculated for step height h, Re_h = 2.57•10⁴), with a base angle of 46° were derived for two geometries of experiment. The experiments demonstrated high sensitivity of liquid crystals to rearrangement of the near-wall flow structure and possibility to obtain quantitative data about mean shear stress levels.