タイトル | Experimental investigations of the time and flow-direction responses of shear-stress-sensitive liquid crystal coatings |
著者(英) | Heineck, James T.; Reda, Daniel C.; Muratore, Joseph J., Jr. |
著者所属(英) | NASA Ames Research Center |
発行日 | 1993-01-01 |
言語 | eng |
内容記述 | Time and flow-direction responses of shearstress-sensitive liquid crystal coatings were explored experimentally. For the time-response experiments, coatings were exposed to transient, compressible flows created during the startup and off-design operation of an injector-driven supersonic wind tunnel. Flow transients were visualized with a focusing Schlieren system and recorded with a 1000 frame/sec color video camera. Liquid crystal responses to these changing-shear environments were then recorded with the same video system, documenting color-play response times equal to, or faster than, the time interval between sequential frames (i.e., 1 millisecond). For the flow-direction experiments, a planar test surface was exposed to equal-magnitude and known-direction surface shear stresses generated by both normal and tangential subsonic jet-impingement flows. Under shear, the sense of the angular displacement of the liquid crystal dispersed (reflected) spectrum was found to be a function of the instantaneous direction of the applied shear. This technique thus renders dynamic flow reversals or flow divergences visible over entire test surfaces at image recording rates up to 1 KHz. Extensions of the technique to visualize relatively small changes in surface shear stress direction appear feasible. |
NASA分類 | INSTRUMENTATION AND PHOTOGRAPHY |
レポートNO | 93A25508 AIAA PAPER 93-0181 |
権利 | Copyright |
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