Measurement of surface shear stress vectors using liquid crystal coatings

AIAA Journal ◽  
1994 ◽  
Vol 32 (8) ◽  
pp. 1576-1582 ◽  
Author(s):  
Daniel C. Reda ◽  
Joseph J. Muratore
Keyword(s):  
Shear Stress ◽  
Liquid Crystal ◽  
Surface Shear Stress ◽  
Surface Shear

Areal measurements of surface shear stress vector distributions using liquid crystal coatings

1996 ◽  
Author(s):  
D. Reda ◽  
M. Wilder ◽  
D. Farina ◽  
G. Zilliac ◽  
R. McCabe ◽  
...  
Keyword(s):  
Shear Stress ◽  
Liquid Crystal ◽  
Surface Shear Stress ◽  
Stress Vector ◽  
Surface Shear

Measurement of surface shear stress vector beneath high-speed jet flow using liquid crystal coating

2018 ◽  
Vol 32 (12n13) ◽  
pp. 1840029
Author(s):  
Cheng-Peng Wang ◽  
Ji-Song Zhao ◽  
Yun Jiao ◽  
Ke-Ming Cheng
Keyword(s):  
Shear Stress ◽  
Liquid Crystal ◽  
Wind Tunnel ◽  
High Speed ◽  
Jet Flow ◽  
Test Surface ◽  
Surface Shear Stress ◽  
Stress Vector ◽  
Surface Shear ◽  
Coating Color

The shear-sensitive liquid crystal coating (SSLCC) technique is investigated in the high-speed jet flow of a micro-wind-tunnel. An approach to measure surface shear stress vector distribution using the SSLCC technique is established, where six synchronous cameras are used to record the coating color at different circumferential view angles. Spatial wall shear stress vector distributions on the test surface are obtained at different velocities. The results are encouraging and demonstrate the great potential of the SSLCC technique in high-speed wind-tunnel measurement.

Visualization of separation and reattachment in an incident shock-induced interaction

2021 ◽  
pp. 095441002098349
Author(s):  
Yun Jiao ◽  
Chengpeng Wang
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Shear Stress ◽  
Separation Bubble ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Bottom Wall ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Oil Flow

An experimental study is conducted on the qualitative visualization of the flow field in separation and reattachment flows induced by an incident shock interaction by several techniques including shear-sensitive liquid crystal coating (SSLCC), oil flow, schlieren, and numerical simulation. The incident shock wave is generated by a wedge in a Mach 2.7 duct flow, where the strength of the interaction is varied from weak to moderate by changing the angle of attack α of the wedge from 8° and 10° to 12°. The stagnation pressure upstream was set to approximately 607.9 kPa. The SSLCC technique was used to visualize the surface flow characteristics and analyze the surface shear stress fields induced by the initial incident shock wave over the bottom wall and sidewall experimentally which resolution is 3500 × 200 pixels, and the numerical simulation was also performed as the supplement for a clearer understanding to the flow field. As a result, surface shear stress over the bottom wall was visualized qualitatively by SSLCC images, and flow features such as separation/reattachment and the variations of position/size of separation bubble with wedge angle were successfully distinguished. Furthermore, analysis of shear stress trend over the bottom wall by a hue value curve indicated that the relative magnitude of shear stress increased significantly downstream of the separation bubble compared with that upstream. The variation trend of shear stress was consistent with the numerical simulation results, and the error of separation position was less than 2 mm. Finally, the three-dimensional schematic of incident shock-induced interaction has been achieved by qualitative summary by multiple techniques, including SSLCC, oil flow, schlieren, and numerical simulation.

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