Effect of free-stream turbulence on the flow structure near a wedge and the windward side of an airfoil

The flow structure behind wire grids is studied for flows with a low subsonic velocity, and the effect of grids on the boundary-layer flow structure is considered. It is shown that the mean-velocity inhomogeneity induced by the grid does not disappear until a distance of 925 calibers downstream of the grid is reached. Liquid-crystal thermography combined with hot-wire measurements made it possible to find the source of steady large-scale streamwise vortex structures in the boundary layer on a wedge and on an airfoil and to determine the parameters of these structures.