PROBLEMS AND ACHIEVEMENTS IN PANORAMIC SHEAR STRESS DIAGNOSTICS BY LIQUID CRYSTALS

摘要

For panoramic diagnostics of the mean shearstresses  on the studied model, thin-filmcoatings based on optically-active liquidcrystals which are sensitive to shear stress (SSLCs) may be applied.Different LC materials and approaches areconsidered in this work including choice ofexperimental technique, practical technologicalaspects and data processing.Potentialities of cholesteric LCs manufacturedat ITAM (Novosibirsk) are studied and testedunder subsonic and transonic flow conditions incommercial wind tunnels (WT) T-128 and T-103(TsAGI). Visualization of laminar-turbulenttransition, flow separation and shock waves wassuccessfully performed.The method of using nematic LCs twisted by theflow for shear stress diagnostics is investigatedin laboratory subsonic wind tunnel (ITAM).Calibration functions of the reflected lightintensity dependent on shear stress wereobtained.Experiments showed that liquid crystals are apromise for panoramic shear stress diagnostics.