Experimental review of devices to artificially thicken wind tunnel boundary layers

Three devices that artificially increase the thickness of the boundary layer in a wind tunnel working section have been tested. These included a serrated fence to disturb the flow, and the use of various secondary jet arrays injected into the boundary layer through the bounding surface. Momentum and turbulence profiles in the boundary layer downstream from the thickening devices were measured. The greatest boundary layer thickness was achieved using an array of varying diameter crossflow jets with the jet diameter reducing with distance downstream.However, the fence thickener and a plate with varying jets increasing in diameter downstream produce a boundary layer with momentum and turbulence profiles more typical of a natural equilibrium boundary layer.