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Modesti, D. (author), Sathyanarayana, Srikanth (author), Salvadore, Francesco (author), Bernardini, Matteo (author)We perform direct numerical simulation of supersonic turbulent channel flow over cubical roughness elements, spanning bulk Mach numbers -, both in the transitional and fully rough regime. We propose a novel definition of roughness Reynolds number which is able to account for the viscosity variations at the roughness crest and should be used...journal article 2022
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Angka Bayu Putranto, Angka (author)This thesis concerns a numerical investigation for the stabilization (delay of laminar-to-turbulent transition) of ows over a at plate with a meta-unit of a possible metamaterial. The type of instability studied is that due to small disturbances in an incompressible, two-dimensional boundary layer. The linear growth of the disturbance in the...master thesis 2021
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Blom, Peter (author)Research into constructing reduced-order models (ROM) to reduce computational cost or to interpret complex datasets from numerical or experimental sources has steadily been gaining popularity over the past few years. Many methods currently exist to construct ROMs. The proper orthogonal decomposition (POD) is one of the most widely adopted...master thesis 2021
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ANAND, ABHIRATH (author)The turbulent boundary layer development under the influence of an air cavity is studied experimentally using planar PIV, with the aim of gaining insight and building upon the flow physics typically encountered in the application of air layer drag reduction. A detection technique based on correlation values is implemented to obtain an...master thesis 2021
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Hartog, Friso (author)Turbulent drag is the largest source of fuel consumption in aviation and forms a significant contribution to climate warming. Recent numerical studies have suggested the ability of surfaces with streamwise-preferential permeability to reduce turbulent friction, and a theoretical framework behind the working mechanism has been proposed. This work...master thesis 2021
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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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Breedijk, Myrthe (author)This study aims to look into the effect of small-scale surface heterogeneity on the mixing properties within the stable boundary layer (SBL) and the impact of different configurations of the heterogeneity on this mixing. The motivation for this research is to better understand the turbulent mixing phenomena in the SBL and to be able to represent...master thesis 2021
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Chaves García-Mascaraque, Adrián (author)A formulation based on the evaluation of power conversions within the system allows to overcome the limitations of conventional momentum analyses to study tightly coupled airframe-propulsion configurations such as Boundary Layer Ingestion. The so-called power balance method is applied in a CFD framework to gain insight about the application of...master thesis 2021
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de Koning, Coert (author)To achieve delay of laminar-to-turbulent transition of boundary layers, the application of acoustic metamaterial concepts is investigated. This is done analytically, numerically and experimentally by studying the interaction between a Helmholtz resonator and a TS wave. A Helmholtz resonator can serve as a meta-atom in a metamaterial. The desired...master thesis 2021
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Lambers, Tim (author)Due to the growing energy demand and global warming renewable energy is currently of interest. To deal with the production intermittency of renewable energy, energy might be stored in hydrogen. Hydrogen can be converted into electricity with a fuel cell or by combusting hydrogen in a gas turbine. Gas turbines are more suitable for large power...master thesis 2021
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Lai, Yu-Jui (author)This research studies the fluid-structure interaction (FSI) of compliant surfaces in air flows, with an objective of finding possible turbulent viscous drag reduction. A compliant surface is a thin layer of viscoelastic material drawing inspiration from dolphin epidermis, which was thought to have drag-reducing capabilities by Gray (1936)....master thesis 2021
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Lin, Yuyu (author)Dimples are shallow, indented surfaces that attempt to reduce drag in turbulent boundary layer flows. However, the underlying effect of the dimples on the drag is not entirely understood. This thesis sets out to expand our understanding; a numerical investigation of turbulent boundary layer flow over dimpled surfaces is conducted. This research...master thesis 2021
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van der Voort Maarschalk, Joost (author)Drag in pipelines is composed almost solely of skin friction drag. The most common technique to achieve drag reduction (DR) is by adding drag-reducing agents. However, in the aerospace industry, various impressive passive drag-reducing techniques have been suggested to reduce skin friction drag in the past decades. Among these techniques,...master thesis 2021
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Penmathsa, Akhil (author)Flame flashback is a failure mode in the operation of lean premixed combustion system. Due to higher flame speeds and lower quenching distances, hydrogen-rich fuel mixtures are prone to boundary layer flashback (BLF), where mixture flow speeds are low compared to the local flow velocity. Research at TU Munich (Eichler 2011) has resulted in new...master thesis 2021
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van Hooft, J.A. (author)Weather and climate influence life in many ways; varying climatic conditions can be associated with varying human cultures and on a day-to-day basis, the weather influences our plans and mood. As such, a proper prediction of the weather is of great importance. Ultimately, the weather is fueled by solar irradiation, which changes sharply over the...doctoral thesis 2021
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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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Luesutthiviboon, S. (author), Ragni, D. (author), Avallone, F. (author), Snellen, M. (author)This study focuses upon a new permeable topology design concept as an alternative to porous metal foams, for turbulent boundary layer trailing-edge (TBL-TE) noise attenuation. The present permeable topology has unconventional characteristics with respect to the metal foams: a combination of low flow resistivity r and high form drag...journal article 2021
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Hu, W. (author), Hickel, S. (author), van Oudheusden, B.W. (author)The low-frequency unsteady motions behind a backward-facing step (BFS) in a turbulent flow at and are investigated using a well-resolved large-eddy simulation. The instantaneous flow field illustrates the unsteady phenomena of the shock wave/boundary layer interaction (SWBLI) system, including vortex shedding in the shear layer, the flapping...journal article 2021
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Modesti, D. (author), Endrikat, Sebastian (author), Hutchins, Nicholas (author), Chung, Daniel (author)We carry out direct numerical simulations of turbulent flow over riblets, streamwise- aligned grooves that are designed to reduce drag by modifying the near-wall flow. Twenty riblet geometries and sizes are considered, namely symmetric triangular with tip angle, and, asymmetric triangular, blade and trapezoidal. To save on computational cost,...journal article 2021
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Tambe, S.S. (author), Schrijer, F.F.J. (author), Gangoli Rao, A. (author), Veldhuis, L.L.M. (author)Centrifugal instability of the boundary layer is known to induce spiral vortices over a rotating slender cone that is facing an axial inflow. This paper shows how a deviation from the symmetry of such axial inflow affects the boundary layer instability over a rotating slender cone with half-angle. The spiral vortices are experimentally...journal article 2021