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Flow visualization tests have been performed to examine the structure of the near-wall flow over a low-aspect ratio straight wing installed at various angles of attack IX and chord Reynolds number Re,» Ucct» = 1.76 X 10 5 The experiments were carried out at two free-stream turbulence levels, E = 0.1% and E = 1%, the latter one having been achieved using a baffling grid. To visualize the flow, termochromic cholesteric liquid crystals and digital processing of video images were used. At the low turbulence level and IX = 27", a flow stall on the lee side of the wing was observed, with a pair oflargescale vortices rotating in the wing plane. Simultaneously, no vortex structures were observed on the windward wing surface. It was found the flow patterns on either side of the wing significantly changed with increasing free-stream turbulence level. A separation bubble appeared near the leading edge on the lee side of the airfoil at E = 1%, and large-scale stationary longitudinal vortices originated over the wing windward surface. The number and sizes ofthe longitudinal structures were found to be dependent on the angle of attack.

A method of film formation based on polymer-dispersed liquid crystals doped with an organic luminophore is proposed. A film is obtained on the basis of thermosensitive cholesteric liquid crystals, encapsulated in a polyvinyl acetate polymer with the addition of a platinum porphyrin complex, whose emission depends on pressure. The presence in the film spectrum of the liquid crystals selective reflection wavelength and the luminophore phosphorescence wavelength makes it possible to measure temperature and pressure distributions on the studied surface simultaneously in one aerodynamic experiment. The main aspects of the method and its possibilities are discussed.

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Images (1-3) show a time variation of the surface temperature on lee side of the straight wing obtained by Liquid Crystal Thermography technique. The wing model with symmetric profile and aspect ratio 0.87 was made of wood. The heated model was exposed to the flow and pictures were recorded by a video system. For comparison image 4 shows a flow pattern (limiting streamlines) obtained by liquid fihn technique (titanium dioxide powder in kerosene).Chord Reynolds number Re, = Usclv = 235 000. Angle of attack a = 27°. Flow direction is from the top to the bottom.