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Knoop, Max (author)Turbulent drag reduction (DR) is a crucial research area, as this can contribute to significant energy and emission reductions in various industrial and transportation applications. One such technique is the active flow control method of spanwise forcing. Spanwise forcing introduces a spatio-temporal spanwise wall oscillation as a boundary...master thesis 2023
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Jose, Nikhil (author)Surfaces that induce slip at the wall have been shown to reduce skin friction drag in the turbulent regime. While superhydrophobic and liquid-infused surfaces are capable of drag reduction in turbulent hydrodynamic flows, neither would be feasible in aerodynamic applications due to the added roughness and the minuscule slip lengths created by...master thesis 2023
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Kooij, Robert (author)From the desire to reduce the impact of traveling on the environment and the increase in fuel prices over the past years, the propeller has regained interest as a propulsion mechanism in the aviation industry. Two main reasons can be found in their high propulsive efficiency and ability to combine with electric motors. The scaling of the motors...master thesis 2023
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van Campenhout, O.W.G. (author), van Nesselrooij, M. (author), Lin, Y. (author), Casacuberta Puig, J. (author), van Oudheusden, B.W. (author), Hickel, S. (author)Although several previous studies have reported a potential drag-reducing effect of dimpled surfaces in turbulent boundary layers, there is a lack of replicability across experiments performed by different research groups. To contribute to the dialogue, we scrutinize one of the most studied dimple geometries reported in the literature, which...journal article 2023
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JAWAHAR, SAHANA (author)Flat surfaces with arrays of wall-normal pores called micro-cavity arrays have shown potential to reduce turbulent skin friction drag. Their designs have been inspired by acoustic liners which are sandwich panels consisting of a honeycomb core, a perforated top plate and a solid back sheet used on...master thesis 2022
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Carrasco Grau, Julio (author)In the last decades, the prevailing belief that smooth surfaces offer the lowest drag has been challenged often. Scholars have, for example, introduced rough and modified surfaces to reduce turbulent skin friction. One of the technologies proposed in the literature is an array of chevron-shaped protrusions; however, there is no academic...master thesis 2022
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Lin, J. (author)Estuaries are the core area of land-sea interactions and have significant ecological and economic value. In estuaries, hydrodynamics and sediment dynamics are the crucial processes governing geomorphology, navigability, and primary production. Since the turn of the 20th century, increased human activities (e.g., damming, dredging, and...doctoral thesis 2022
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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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Sem, Jacopo (author)The reduction of turbulent skin-friction drag has the potential to generate numerous societal benefits. In large-scale industrial applications, the largest share of energy consumption goes into overcoming the friction drag produced by turbulent boundary layers formed on the outside wall. Estimates assess that over 50% of the total fuel burn is...master thesis 2021
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Levoni, Andrea (author)In the aviation, maritime and oil&gas sector, the potential benefit in yearly savings deriving from the reduction of turbulent skin-friction drag through active flow control are estimated in the millions of U.S. Dollars and million tonnes of CO2 emissions. Research in this topic has brought forward numerous techniques, offering enticing drag...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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Claro Dittrich, Eric (author)Dimples are shallow surface indentations that have been recently considered as a passive viscous drag reducing technique for turbulent boundary layers. Studies so far were limited to incompressible low-Re flows and display little consensus on whether dimples can actually produce net improvements in total drag. Conversely, dimple geometry can be...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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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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Lin, J. (author), van Prooijen, Bram (author), Guo, Leicheng (author), Zhu, C. (author), He, Qing (author), Wang, Zhengbing (author)Channel deepening often triggers positive feedback between tidal deformation, sediment import and drag reduction, which leads to the regime shift in estuaries from low-turbid to hyper-turbid state. In this study, a transition in profiles of suspended sediment concentration (SSC) is hypothesised by including a positive feedback loop of...journal article 2021
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Timmer, W.A. (author), Veldhuis, L.L.M. (author)At the 1998 Nagano Winter Olympic Games, zigzag tape was introduced on the race suit lower legs and cap of speed skaters. Application of these zigzag devices on live skaters and cylinders in the wind tunnel showed large improvements in the aerodynamic drag. These wind-tunnel results were unfortunately not widely published, and the impact of...journal article 2021
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Greidanus, A.J. (author)This thesis describes the investigation of the dynamics of turbulent shear flows over non-smooth surfaces. The research was conducted in two parts, related to the experimental facility used in combination with the applied functional surface. The first part describes the experiments of a turbulent Taylor-Couette flow over a...doctoral thesis 2020
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Mahalingesh, Nikhil (author)Aerodynamics plays a significant role in the field of cycling as it is the dominant resistive force at racing speeds of 50 km/h. Sporting events involving multiple cyclists leads to aerodynamic interactions between the cyclists and these interactions have been exploited for performance benefits. One such aerodynamic interaction is drafting,...master thesis 2020
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Raghunathan Srikumar, Sampath (author)Large Eddy Simulations (LES) of a novel type of wing/body junction called the anti-fairing are performed in the current thesis to study the complex turbulent flow physics involved in the junction area and also to obtain a clear understanding of the drag reduction capabilities of the anti-fairing. In regards to that, two separate LES are...master thesis 2019