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Calibri 83ffff̙̙3f3fff3f3f33333f33333.59TU Delft Repositoryg l0uuidrepository linktitleauthorcontributorpublication yearabstract
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departmentresearch group programmeprojectcoordinates)uuid:813e16e49a174ffeb5b958c9837604ecDhttp://resolver.tudelft.nl/uuid:813e16e49a174ffeb5b958c9837604ec`Experimental control of sweptwing transition through baseflow modification by plasma actuatorsdYadala Venkata, Srikar (TU Delft Aerodynamics; Universit de Poitiers); Hehner, M.T. (TU Delft Aerodynamics; University of Stuttgart); Serpieri, J. (TU Delft Aerodynamics); Benard, Nicolas (CNRSUniversit de PoitiersISAEENSMA); Drr, Philipp C. (University of Stuttgart); Kloker, Markus J. (University of Stuttgart); Kotsonis, M. (TU Delft Aerodynamics)Control of laminartoturbulent transition on a sweptwing is achieved by baseflow modification in an experimental framework, up to a chord Reynolds number of 2.5 million. This technique is based on the control strategy used in the numerical simulation by Drr & Kloker (J. Phys. D: Appl. Phys., vol. 48, 2015b, 285205). A spanwise uniform body force is introduced using dielectric barrier discharge plasma actuators, to either force against or along the local crossflow component of the boundary layer. The effect of forcing on the stability of the boundary layer is analysed using a simplified model proposed by Serpieri et al. (J. Fluid Mech., vol. 833, 2017, pp. 164 205). A minimal thickness plasma actuator is fabricated using sprayon techniques and positioned near the leading edge of the sweptwing, while infrared thermography is used to detect and quantify transition location. Results from both the simplified model and experiment indicate that forcing along the local crossflow component promotes transition while forcing against successfully delays transition. This is the first experimental demonstration of sweptwing transition delay via baseflow modification using plasma actuators.Eboundary layer control; boundary layer stability; instability controlenjournal article
20181001Aerodynamics)uuid:6c890da8be9b40c88f0f074a7022385bDhttp://resolver.tudelft.nl/uuid:6c890da8be9b40c88f0f074a7022385b`Conditioning of crossflow instability modes using dielectric barrier discharge plasma actuatorsSerpieri, J. (TU Delft Aerodynamics); Yadala Venkata, Srikar (TU Delft Aerodynamics; CNRSUniversit de PoitiersISAEENSMA); Kotsonis, M. (TU Delft Aerodynamics)*In the current study, selective forcing of crossflow instability modes evolving on a swept wing at is achieved by means of spanwisemodulated plasma actuators, positioned near the leading edge. In the perspective of laminar flow control, the followed methodology holds on the discrete roughness elements/upstream flow deformation (DRE/UFD) approach, thoroughly investigated by e.g. Saric et al. (AIAA Paper 1998781, 1998), Malik et al. (J. Fluid Mech., vol. 399, 1999, pp. 85115) and Wassermann & Kloker (J. Fluid Mech., vol. 456, 2002, pp. 4984). The possibility of using active devices for UFD provides several advantages over passive means, allowing for a wider range of operating numbers and pressure distributions. In the present work, customised alternating current dielectric barrier discharge plasma actuators have been designed, manufactured and characterised. The authority of the actuators in forcing monochromatic stationary crossflow modes at different spanwise wavelengths is assessed by means of infrared thermography. Moreover, quantitative spatiotemporal measurements of the boundary layer velocity field are performed using timeresolved particle image velocimetry. The results reveal distinct steady and unsteady forcing contributions of the plasma actuator on the boundary layer. It is shown that the actuators introduce unsteady fluctuations in the boundary layer, amplifying at frequencies significantly lower than the actuation frequency. In line with the DRE/UFD strategy, forcing a subcritical stationary mode, with a shorter<> wavelength compared to the naturally selected mode, results in less amplified primary vortices and related fluctuations, compared to the critical forcing case. The effect of the forcing on the flow stability is further inspected by combining the measured actuators body force with the numerical solution of the laminar boundary layer and linear stability theory. The simplified methodology yields fast and computationally cheap estimates on the effect of steady forcing (magnitude and direction) on the boundary layer stability.
20180801)uuid:0bea8476570d4ee988ac9be020008f03Dhttp://resolver.tudelft.nl/uuid:0bea8476570d4ee988ac9be020008f03dLocalised estimation and control of linear instabilities in twodimensional wallbounded shear flowsTol, H.J. (TU Delft Control & Simulation); Kotsonis, M. (TU Delft Aerodynamics); de Visser, C.C. (TU Delft Control & Simulation); Bamieh, B. (University of California)A new framework is presented for estimation and control of instabilities in wallbounded shear flows described by the linearised NavierStokes equations. The control design considers the use of localised actuators/sensors to account for convective instabilities in an optimal control framework. External sources of disturbances are assumed to enter the control domain through the inflow. A new inflow disturbance model is proposed for external excitation of the perturbation modes that contribute to transition. This model allows efficient estimation of the flow perturbations within the localised control region of a conceptually unbounded domain. The statespace discretisation of the infinitedimensional system is explicitly obtained, which allows application of linear control theoretic tools. A reducedorder model is subsequently derived using exact balanced truncation that captures the input/output behaviour and the dominant perturbation dynamics. This model is used to design an optimal controller to suppress the instability growth. The twodimensional nonperiodic channel flow is considered as an application case. Disturbances are generated upstream of the control domain and the resulting flow perturbations are estimated/controlled using point wall shear measurements and localised unsteady blowing and suction at the wall. The controller is able to cancel the perturbations and is robust to both unmodelled disturbances and sensor inaccuracies. For singlefrequency and multiplefrequency disturbances with low sensor noise a nearly full cancellation is achieved. For stochastic forced disturbances and high sensor noise an energy reduction in perturbation wall shear stress of 96 % is shown.1control theory; flow control; instability control
20180101Control & Simulation
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