Measurement of Wall Shear Stress in High Speed Air Flow Using Shear-Sensitive Liquid Crystal Coating

Abstract

Wall shear stress is an important quantity in fluid mechanics, but its measurement is a challenging task. An approach to measure wall shear stress vector distribution using shear-sensitive liquid crystal coating (SSLCC) is described. The wall shear stress distribution on the test surface beneath high speed jet flow is measured while using the proposed technique. The flow structures inside the jet flow are captured and the results agree well with the streakline pattern that was visualized using the oil-flow technique. In addition, the shock diamonds inside the supersonic jet flow are visualized clearly using SSLCC and the results are compared with the velocity contour that was measured using the particle image velocimetry (PIV) technique. The work of this paper demonstrates the application of SSLCC in the measurement/visualization of wall shear stress in high speed flow.

Reconstructing wall shear stress from thermal wall imprints

“…To overcome these limitations, flow visualisation techniques have been developed. The thin oil film technique (Maltby, 1962;Tanner and Blows, 1976;Tanner, 1977) based on the thin-oil-film equations derived by Squire (Maltby, 1962) and the liquid crystal coating (Reda and Muratore, 1994;Zhao, 2018) are two such techniques.…”

Skin-Friction-Based Identification of the Critical Lines in a Transonic, High Reynolds Number Flow via Temperature-Sensitive Paint

“…A major challenge for non-intrusive testing at these flow conditions may be the integration of the S 3 F into the surface of the wind-tunnel models. Skin-friction fields can be also determined via Shear-Sensitive Liquid Crystals (SSLC) [ 9 , 54 , 55 ], but the strong sensitivity of SSLC to lighting and viewing directions, combined with complicated data analysis, generally limits their application in aerodynamic studies [ 21 , 28 ].…”