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Rizzo, Paolo (author), Serpieri, J. (author), Kotsonis, M. (author)The present work is an experimental investigation of stationary crossflow (CF) instability-induced transition of the boundary layer over a 45°swept wing, under varying free-stream turbulence, surface roughness, angle of attack and Reynolds number. Key topological features of the transition front, such as the mean transition location and the...conference paper 2019
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Yadala, Srikar (author), Benard, Nicolas (author), Kotsonis, M. (author), Kerherve, Franck (author), Moreau, Eric (author)The influence of linear (spanwise-uniform) forcing applied by a DBD plasma actuator on the growth of a turbulent mixing layer and the dynamics of large-scale spanwise vortices, are investigated experimentally. Furthermore, the freestream turbulence intensity in the low-velocity stream is maintained at a high level to examine its impact on the...conference paper 2019
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Kurelek, J.W. (author), Yarusevych, S. (author), Kotsonis, M. (author)This work examines flow development in a laminar separation bubble (LSB) undergoing natural transition and transition controlled with two-dimensional and spanwise modulated disturbances. The investigation is carried out in a series of wind tunnel tests, with the separation bubble formed over a flat plate subjected to an adverse pressure...conference paper 2019
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Tol, H.J. (author), Kotsonis, M. (author), de Visser, C.C. (author)This paper investigates the use of point wall pressure measurements for output feedback control of Tollmien–Schlichtingwaves in Falkner–Skan boundary layers.Anewapproach is presented for input–outputmodeling of the linear dynamics of the fluid system and the integration withH2∕Linear Quadratic Gaussian reduced-order control design. The pressure...journal article 2019
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Kurelek, J.W. (author), Yarusevych, S. (author), Kotsonis, M. (author)Vortex merging in a laminar separation bubble (LSB) is studied experimentally. The bubble is formed on the suction side of a NACA 0018 airfoil at an angle of attack of 4° and a Reynolds number of 125 000. The merging process in the bubble is manipulated through acoustic forcing applied as a tone at either the fundamental vortex shedding...journal article 2019
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Benard, Nicolas (author), Zong, H. (author), Zhang, Yang (author), Kotsonis, M. (author), Acher, Gwenael (author), Cattafesta, Louis N. (author), Bonnet, Jean-Paul (author), Moreau, Eric (author)Active flow control is demanding for new actuation technologies as none of the actual available actuators has reached all the criterions for expecting an implementation in the coming years. Here, a new type of pulsed jet is designed and preliminary measurements of its performances in quiescent flow are conducted. Pulsed operation has been chosen...conference paper 2020
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Yadala, Srikar (author), Benard, Nicolas (author), Kotsonis, M. (author), Moreau, Eric (author)The influence of spanwise-uniform (linear) forcing applied by a dielectric barrier discharge (DBD) plasma actuator on the growth of a plane mixing layer and the dynamics of large-scale spanwise vortices within, are investigated experimentally. Quantitative spatio-temporal measurement of the flow field is acquired using high-speed planar particle...conference paper 2020
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Hehner, M. T. (author), Gatti, D. (author), Kriegseis, J. (author), Mattern, P. (author), Kotsonis, M. (author)A modified concept for generating DBD-based virtual spanwise wall oscillations is introduced in continuation of earlier efforts by Hehner et al. (2019) ["Stokes-layer formation under absence of moving parts – A novel oscillatory plasma actuator design for turbulent drag reduc-tion", Phys. Fluids 31, 051701]. Four groups of a multi-electrode...conference paper 2020
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Rezaeiha, Abdolrahim (author), Kotsonis, M. (author)Wind tunnel measurements are performed to investigate the potential for mitigation of aerodynamic load fluctuations on airfoils, as the main source of fatigue for wind turbines, using plasma actuators. The experiment consists of aerodynamic force measurements using six strain gauges and 2-component velocity measurements using particle image...journal article 2020
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Merino Martinez, R. (author), Rubio Carpio, A. (author), Lima Pereira, L.T. (author), van Herk, S.W.L. (author), Avallone, F. (author), Ragni, D. (author), Kotsonis, M. (author)The newly refurbished vertical tunnel (V-tunnel) at Delft University of Technology has been redesigned as a state-of-the-art facility for research in aeroacoustics (A-tunnel), as well as fundamental studies in laminar-turbulent transition and flow control. This manuscript focuses on the design and refurbishment aspects of the facility,...journal article 2020
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Rius Vidales, A.F. (author), Kotsonis, M. (author)The impact of a forward-facing step (FFS) on the development of stationary crossflow instability is investigated on a swept wing model in a low-turbulence wind tunnel at chord Reynolds number of. Infrared thermography and particle image velocimetry measurements are used to quantify the transition location and growth of the crossflow...journal article 2021
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Zoppini, G. (author), Ragni, D. (author), Kotsonis, M. (author)An experimental parametric study of the effect of discrete roughness elements (DRE) on the development and breakdown of stationary crossflow instability on a swept wing is presented. A systematic investigation of the receptivity to various elements height and chord locations is carried out in a crossflow dominated flow. The flow is globally and...conference paper 2021
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Casacuberta Puig, J. (author), Hickel, S. (author), Kotsonis, M. (author)We study the interaction between a stationary crossflow instability and forward-facing steps in a swept-wing boundary layer using Direct Numerical Simulations (DNS). The station- ary primary crossflow mode is imposed at the inflow. Steps of several heights are modeled. Particular emphasis is placed on ensuring a fully stationary solution, in...conference paper 2021
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Peng, K. (author), Avallone, F. (author), Kotsonis, M. (author)Plasma-based flow control poses a simple and robust technique for transition delay on swept wings. However, a clear understanding of how plasma actuators affect crossflow instabilities is necessary to develop and mature crossflow control based on plasma actuators. In this paper, the design of a new swept wing model optimised for the study of...conference paper 2021
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Casacuberta Puig, J. (author), Groot, K.J. (author), Hickel, S. (author), Kotsonis, M. (author)The evolution of secondary instabilities in a three-dimensional stationary-crossflow-domina- ted boundary layer is investigated by means of Direct Numerical Simulations (DNS) and linear spanwise BiGlobal stability analysis. Single-frequency unsteady disturbances and a critical stationary crossflow mode are considered. Unsteady perturbation...conference paper 2022
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Zoppini, G. (author), Ragni, D. (author), Kotsonis, M. (author)The application of an isolated roughness element in the laminar boundary layer developing on the surface of a wing, introduces flow instabilities that eventually lead to the breakdown of the laminar flow structures and the formation of a turbulent wedge. The present work, investigates the instabilities and transition process initiated by an...conference paper 2022
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Hehner, Marc T. (author), Gatti, Davide (author), Kotsonis, M. (author), Kriegseis, Jochen (author)Two different plasma actuation strategies for producing near-wall flow oscillations, namely the burst-modulation and beat-frequency mode, are characterized with planar particle image velocimetry in quiescent air. Both concepts are anticipated to work as non-mechanical surrogates of oscillating walls aimed at turbulent flow drag reduction,...journal article 2022
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Scarano, F. (author), Ujjaini Kempaiah, K. (author), Kotsonis, M. (author)In the present work, planar and tomographic PIV are used to investigate how the organisation of wall turbulence is altered when actuators are operated with the objective of reducing the skin friction drag. When the wall is mechanically oscillated in the spanwise direction, high-resolution planar PIV enable the direct measurement of wall shear...conference paper 2022
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Castellanos, Rodrigo (author), Michelis, Theodorus (author), Discetti, Stefano (author), Ianiro, Andrea (author), Kotsonis, M. (author)The effect of streamwise plasma vortex generators on the convective heat transfer of a turbulent boundary layer is experimentally investigated. A Dielectric Barrier Discharge (DBD) plasma-actuator array is employed to promote pairs of counter-rotating, streamwise-aligned vortices embedded in a well-behaved turbulent boundary layer over a flat...journal article 2022
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Zoppini, G. (author), Westerbeek, S.H.J. (author), Ragni, D. (author), Kotsonis, M. (author)The effect of discrete roughness elements on the development and breakdown of stationary crossflow instability on a swept wing is explored. Receptivity to various element heights and chordwise locations is explored using a combination of experimental and theoretical tools. Forcing configurations, determined based on linear stability...journal article 2022