Effect of upstream flow deformation using plasma actuators on crossflow transition induced by unsteady vortical free-stream disturbances

QC 20170816
Upstream flow deformation (UFD) has been shown to be an effective technique to delay roughness induced laminar-turbulent transition at low free-stream turbulence level in three-dimensional boundary-layer flows. Beneficial steady crossflow vortex (CFV) control modes are excited and the resulting nonlinear CFVs induce a useful mean-flow distortion. We recently showed by direct numerical simulations that plasma actuators, modeled by localized steady volume forcing, can be employed to excite the UFD control modes. In the current work we investigate the same actuator set-ups to control transition caused by traveling CFVs that are excited by single unsteady vortical free-stream disturbances (FSDs) impinging on the boundary layer. FSDs of various wavenumbers and frequencies are imposed either upstream or downstream, or at the position of the actuators to also scrutinize if the volume forcing has a direct unfavorable effect on the receptivity to the FSDs that adds to the stabilization by the UFD. For all investigated cases we show that a significant transition delay is achieved.

TEKNIK OCH TEKNOLOGIER Maskinteknik Strömningsmekanik och akustik hsv//swe
ENGINEERING AND TECHNOLOGY Mechanical Engineering Fluid Mechanics and Acoustics hsv//eng
Atmospheric thermodynamics
Boundary layer flow
Boundary layers
Deformation
Fluid dynamics
Laminar boundary layer
Vortex flow
Control modes
Freestream turbulence
Laminar turbulent transitions
Plasma actuator
Steady crossflow
Three-dimensional boundary layer flows
Transition delays
Upstream flow
Actuators

Kloker, M. J. (författare)
Hanifi, ArdeshirKTH,Stabilitet, Transition, Kontroll,Linné Flow Center, FLOW,SeRC - Swedish e-Science Research Centre(Swepub:kth)u1t125t9 (författare)
KTHStabilitet, Transition, Kontroll (creator_code:org_t)

Ingår i:47th AIAA Fluid Dynamics Conference, 2017Reston, Virginia : American Institute of Aeronautics and Astronautics

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