An experimental study of the forerunners of boundary-layer localized disturbances at an enhanced turbulence level
V.N. Gorev, M.M. Katasonov, V.V. Kozlov, P.A. Motyrev
Keywords: laminar-turbulent transition, high free-stream turbulence, forerunners, longitudinal structures
Pages: 573-581
Abstract
Turbulence production processes in boundary layer at a high level of free-stream turbulence have been studied. The tests were carried out in the MT-324 subsonic wind tunnel of ITAM, SB RAS, on models of straight and 45° swept wings at Reynolds numbers Rec1 = 97000 and Rec2 = 137000, and also at low (Tu = 0.18 % U∞) and high (Tu = 0.79 and 2.31 % U∞) levels of free-stream turbulence. The longitudinal localized disturbances developing in the boundary layer under the action of free-stream turbulence were artificially modeled using local air suction through a slot on the model surface. Wave packets, or forerunners, produced in the boundary layer, in the region preceding the abrupt local change of flow velocity near the localized-disturbance fronts, were examined. The high level of free-stream turbulence was found to accelerate the downstream evolution of the wave packets and their transformation into turbulent spots.
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