Краткое описание

In order to control the crossflow dominated transition process, an experimental investigation in a 3D-boundary layer was conducted using a swept flat-plate model with a displacement body. A generation of a stationary vortex structure is done, placing micron sized roughness elements in span wise direction at x/c = 0.17, generating a fixed vortex streaks wavelength of λ = 12.5 mm, equal to the most amplified wavelength under natural condition.
Based on this, a second row of micron sized roughness elements was placed further downstream to reduce the secondary instability which is responsible for transition in highly distorted 3D- boundary layers. Hot wire measurements in the 3D- boundary layer at various chord wise position were conducted detecting the secondary instability locations. A localization of the ideal positioning of the second roughness elements was done by a variation of three different span wise positions. Maintaining the wavelength of λ = 12.5 mm, a transition delay for one of the test cases was obtained.