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Bugeat, B. (author), Boldini, P.C. (author), Hasan, A.M. (author), Pecnik, Rene (author)This paper addresses the stability of plane Couette flow in the presence of strong density and viscosity stratifications. It demonstrates the existence of a generalised inflection point that satisfies the generalised Fjørtoft criterion of instability when a minimum of kinematic viscosity is present in the base flow. The characteristic scales...journal article 2024
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Arkesteijn, Joerie (author)Following recent proof of swept wing laminar-to-turbulent boundary layer transition delay through base-flow modification using AC-DBD plasma actuators, an experimental investigation is performed to study the responsible physical mechanism. An experiment is conducted on a 45° swept wing in the anechoic wind tunnel at the Delft University of...master thesis 2021
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Ebrahimi, Amin (author), Kleijn, C.R. (author), Richardson, I.M. (author)Molten metal melt pools are characterised by highly non-linear responses, which are very sensitive to imposed boundary conditions. Temporal and spatial variations in the energy flux distribution are often neglected in numerical simulations of melt pool behaviour. Additionally, thermo-physical properties of materials are commonly changed to...journal article 2021
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van Meerkerk, M. (author), Poelma, C. (author), Hofland, Bas (author), Westerweel, J. (author)We present an experimental study on the variation in wave impact location and present a mechanism for the development of free surface instabilities on the wave crest for repeatable plunging wave impacts on a vertical wall. The existence of free surface instabilities on an impacting wave is well known, but their characteristics and formation...journal article 2020
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Ebrahimi, Amin (author), Kleijn, C.R. (author), Richardson, I.M. (author)Heat and fluid flow in low Prandtl number melting pools during laser processing of materials are sensitive to the prescribed boundary conditions, and the responses are highly nonlinear. Previous studies have shown that fluid flow in melt pools with surfactants can be unstable at high Marangoni numbers. In numerical simulations of molten metal...conference paper 2019
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Groot, K.J. (author)Laminar-turbulent transition dictates an increase in skin friction. The resulting turbulent skin friction contributes to approximately 40% of the total drag of commercial aircraft. Reducing the turbulent flow region by postponing transition can therefore significantly reduce the carbon footprint and costs of flying. Transition prediction is...doctoral thesis 2018
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Tol, H.J. (author)Dynamical systems theory can significantly contribute to the understanding and control of fluid flows. Fluid dynamical systems are governed by the Navier-Stokes equations, which are continuous in both time and space, resulting in a state space of infinite dimension. To incorporate tools from systems theory it has become common practise to...doctoral thesis 2018
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Serpieri, J. (author), Kotsonis, M. (author)In this study, experiments are performed towards the identification and measurement of unsteady modes occurring in a transitional swept wing boundary layer. These modes are generated by the interaction between the primary stationary and travelling cross-flow instabilities or by secondary instability mechanisms of the stationary cross-flow...journal article 2018
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Serpieri, J. (author)The research presented in this booklet focusses on the cross-flow instability. Applying traditional and advanced flow diagnostics, the boundary layer evolution is studied in detail. The topology and evolution of both primary and secondary instability mechanisms is revealed with unprecedented detail for experimental research paving the way for...doctoral thesis 2018
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Vermes, A.G. (author)With heavy duty propulsion systems under development for upcoming Mars missions, such as the Space Launch System and the Interplanetary Spaceship, the stability of high-performance liquid-propellant rocket engines is of renewed interest. High-power-density rocket turbopumps forward pressurized fuel to the combustor at high rates. Turbopumps...master thesis 2017
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Rinaldi, E. (author), Patel, A. (author), Schlatter, Philipp (author), Pecnik, Rene (author)We investigate the stability of streaks in the buffer layer of turbulent channel flows with temperature-dependent density and viscosity by means of linear theory. The adopted framework consists of an extended set of the Orr-Sommerfeld-Squire equations that accounts for density and viscosity nonuniformity in the direction normal to the walls....journal article 2017
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Korevaar, T.J.A. (author)Navigation locks are used to transport vessels between waterways with different water levels. In the nearby future many navigation locks will be renovated or replaced. During the design of a new lock still some unknown factors are encountered. One of these factors is the vibration of the valve. The valve is part of the filling and emptying...master thesis 2016
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Meulenbroek, B.J. (author), Farajzadeh, R. (author), Bruining, J. (author)Carbon dioxide injected in an aquifer rises quickly to the top of the reservoir and forms a gas cap from where it diffuses into the underlying water layer. Transfer of the CO2 to the aqueous phase below is enhanced due to the high density of the carbon dioxide containing aqueous phase. This paper investigates the behavior of the diffusive...journal article 2013
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Geschiere, S.D. (author), Ziemecka, I. (author), Van Steijn, V. (author), Koper, G.J.M. (author), Van Esch, J.H. (author), Kreutzer, M.T. (author)This paper studies the Rayleigh-Plateau instability for co-flowing immiscible aqueous polymer solutions in a microfluidic channel. Careful vibration-free experiments with controlled actuation of the flow allowed direct measurement of the growth rate of this instability. Experiments for the well-known aqueous two phase system (ATPS, or aqueous...journal article 2012
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Violato, D. (author), Scarano, F. (author)The three-dimensional behavior of flow transition in circular and 6-chevron jets at Re?=?5000 is investigated with experiments conducted on a free water jet by time-resolved tomographic particle image velocimetry. The emphasis is on the unsteady organization of coherent flow structures, which play a role in the generation of acoustic noise....journal article 2011
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Kotsonis, M. (author), Veldhuis, L. (author)An experimental investigation is performed on the operation of dielectric barrier discharge plasma actuators used as manipulators of secondary and unsteady flow structures such as boundary layer instabilities or shedding vortices. The actuators are tested mainly in pulse mode. High sample rate hot-wire measurements of the induced velocity field...journal article 2010
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Mortensen, P.H. (author), Andersson, H.I. (author), Gillissen, J.J.J. (author), Boersma, B.J. (author)The dynamical behavior of tiny elongated particles in a directly simulated turbulent flow field is investigated. The ellipsoidal particles are affected both by inertia and hydrodynamic forces and torques. The time evolution of the particle orientation and translational and rotational motions in a statistically steady channel flow is obtained for...journal article 2008
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Sobera, M.P. (author), Kleijn, C.R. (author), Van den Akker, H.E.A. (author)A study of the flow at subcritical Re = 3900 around a circular cylinder, surrounded at some fixed small distance by a porous layer with a hydraulic resistance typical for that of textile materials, has been performed by means of direct numerical simulations. The flow in the space between the porous layer and the solid cylinder was found to be...journal article 2006
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Tsai, Y.S. (author), Grass, A.J. (author), Simons, R.R. (author)The initial growth of mechanically generated small amplitude water waves below a laminar air stream was examined numerically and experimentally in order to explore the primary growth mechanism, that is, the interfacial instability of coupled laminar air and water flows. Measurements of the laminar velocity profile in the air over the water...journal article 2005
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Blanckaert, K. (author), De Vriend, H.J. (author)In spite of its importance, little is known about the turbulence characteristics in open-channel bends. This paper reports on an experimental investigation of turbulence in one cross section of an open-channel bend. Typical flow features are a bicellular pattern of cross-stream circulation (secondary flow) and a turbulence activity in the outer...journal article 2005
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