Control of crossflow-induced laminar-turbulent transition in a 3-d boundary-layer flow using plasma actuators

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Investigations for the control of crossflow-induced laminar-turbulent transition in 3-d boundary-layer flows by cold plasma actuators are planned using direct numerical simulations. 3-d boundary layers are typical on swept-back wings, but also on rotor blades of wind turbines where the level of oncoming turbulence is higher than in free airplane flight at relatively high altitude. To date, suction at the wall or a special setup of micron-sized roughness elements have been investigated and used for laminar flow control of 3-d boundary layers, but dielectric barrier discharge (cold) plasma actuators can be more easily operated, producing a localized volume force extending up to the boundary-layer edge. Successful operation has been demonstrated for 2-d boundary layers so far, but the control of steady and unsteady crossflow modes leading to steady or travelling crossflow vortices is promising. Based on first investigations with respect to steady modes, the primary goal of this proposal is to scrutinize the plasma-actuator control of scenarios comprising travelling modes induced by medium-level oncoming turbulence, in order to check the fundamental applicability of such a control on wind-turbine blades to improve their efficiency. The new DLR-Göttingen Prinzipexperiment serves as base flow in this stage to enable a later direct fundamental testing of the numerical findings.