The evaluation of shear sensitive liquid crystals at Mach 3

This paper examines the performance of a range of shear sensitive liquid crystals (manufactured by Hallcrest) in wind tunnel boundary layers upto Mach 3. The changes in observed color were assessed, using digital analysis of CCD video recordings, in terms of the hue, saturation and intensity. The measurement program included the assessment of crystal behavior under the following conditions: (i) turbulent boundary layer at Mach 3, (ii) around a half model in a Mach 2 boundary layer, and (iii) whilst being mechanically sheared in a rotational rig. The results show that the various crystal formulations possess different characteristics which cannot be defined simply by the viscosity of the crystal mixture.