Shear-stress measurement in aerodynamic testing using cholesteric liquid crystals

Abstract

The change in the selective reflection spectra of cholesteric liquid crystals with shear is described, and the results indicate that, although it appears to be a promising technique for flow visualization in aerodynamic testing, the method is only suitable for approximate measurement of shear. An improved method for visualising flow is proposed that utilizes a shear-induced texture change from the uncoloured focal-conic state to the selectively reflecting Grandjean state. The sensitivity of the transition to shear is investigated and the effects of adding silica particles to modify the viscosity is examined.