Searched for: subject%3A%22boundary%255C%2Blayers%22
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Schilder, Jop (author)
Contrary to conventional wisdom favouring smooth surfaces for drag reduction, the last decades have brought forth different textured surfaces showing drag reduction in turbulent boundary layers, of which riblets are the most studied.<br/>Sirovich and Karlson (1997) introduced a different textured surface named chevron-shaped protrusions,...
master thesis 2024
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Laguarda, L. (author), Hickel, S. (author), Schrijer, F.F.J. (author), van Oudheusden, B.W. (author)
Wall-resolved large-eddy simulations (LES) are performed to investigate Reynolds number effects in supersonic turbulent boundary layers (TBLs) at Mach 2.0. The resulting database covers more than a decade of friction Reynolds number Re<sub>τ</sub>, from 242 to 5554, which considerably extends the parameter range of current high-fidelity...
journal article 2024
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PENG, Yi-Kai (author)
Boundary Layer Ingestion (BLI) is a promising propulsion concept for aviation, aiming to reduce fuel burn. This configuration involves using the propulsor to ingest the boundary layer from the fuselage or wing. Typically, aircraft with BLI propulsors also integrate a hybrid-electric powertrain. This integrated setup has shown potential in fuel...
master thesis 2023
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Jha, Mayanka (author)
With ongoing research towards clean combustion, hydrogen has been identified as a potential alternative to natural gas fuel, for example in power generation sectors utilizing gas turbines because of their inherent nature of being a carbon-free energy carrier. However, it is crucial to clarify that the ultimate goal is not just carbon-free...
master thesis 2023
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Tosto, F. (author)
The vast majority of energy conversion systems currently makes use of fossil fuels, whose combustion generates harmful greenhouse gases. Transitioning to renewable energy sources is thus paramount to limiting the environmental impact of human activities on the climate. In this regard, the harvesting of wasted thermal energy constitutes a...
doctoral thesis 2023
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Zoppini, G. (author)
The research presented in this thesis focuses on the receptivity to surface roughness of swept wing boundary layers dominated by crossflow instabilities (CFI), providing insights into how surface roughness can be used to passively control the developing instabilities. Discrete roughness elements (DRE) arrays and distributed randomized roughness...
doctoral thesis 2023
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Janoff, Philipp (author)
Leading edge roughness is an important challenge for the wind energy industry as blades are permanently exposed to the damaging impacts of the environment. The contamination due to impact of insects, ice accretion and dust; as well as the erosion of the blade due to rain, debris and abrasive airborne particles increase roughness upon the surface...
master thesis 2023
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Budanko, Toma (author)
An experimental investigation is presented in which an array of pulsed jet actuators is used to control a turbulent separation bubble formed on a curved backward facing ramp. The array is positioned upstream of detachment and consists of wall-normal high aspect ratio skewed rectangular jets which generate streamwise vortices in the boundary...
master thesis 2023
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Kukučka, Tomas (author)
Boundary Layer Ingestion (BLI) is a promising technology for reducing the impact of aviation on the environment. By placing a propulsor on an aircraft such that it ingests the slower moving air within the boundary layer, a decrease in power consumption can be achieved. Evaluating the performance of BLI configurations remains a challenge though....
master thesis 2023
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Topper, Friso (author)
Boundary layer ingestion is an airframe-propulsion integration technology capable of enhancing aircraft propulsive efficiency. The Propulsive Fuselage Concept, a tube-and-wing layout with an rear-fuselage-mounted propulsor in the boundary layer ingestion configuration, especially takes advantage this. However, the relation between physical shape...
master thesis 2023
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Formidabile, Martina (author)
TOP contoured nozzles, with large area-ratios, are commonly employed in rocket propulsion systems as they feature an excellent thrust-to-weight ratio. A significant shortcoming to this design is that, during the startup and shutdown transients of a LRE, the internal nozzle flow progresses through a series of overexpanded flow states - Free Shock...
master thesis 2023
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Singh, Pratyush Kumar (author)
In recent years, research for turbulent boundary layer (TBL) has shifted towards developing novel approaches to reduce drag. This shift is driven by new industrial standards emphasizing fuel-efficient and environmentally friendly air transportation. As wall-bounded turbulence plays a significant role in the overall drag experienced by an...
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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Makaveev, Momchil (author)
This project proposes and evaluates a novel concept for an airspeed instrument aimed at small hybrid unmanned aerial vehicles. The working principle is to relate the power spectra of the wall-pressure fluctuations beneath the turbulent boundary layer formed over the vehicle’s body to its airspeed. The instrument consists of two microphones,...
master thesis 2023
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Makaveev, M.K. (author), Snellen, M. (author), Smeur, E.J.J. (author)
This paper puts forward a novel design for an airspeed instrument aimed at small fixed-wing tail-sitter unmanned aerial vehicles. The working principle is to relate the power spectra of the wall-pressure fluctuations beneath the turbulent boundary layer present over the vehicle’s body in flight to its airspeed. The instrument consists of two...
journal article 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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Pirozzoli, Sergio (author), Modesti, D. (author)
We carry out direct numerical simulations (DNS) of turbulent flow and heat transfer in pressure-driven plane channels, by considering cases with heating on both walls, as well as asymmetric heating limited to one of the channel walls. Friction Reynolds numbers up to are considered, and Prandtl numbers from to, the temperature field being...
journal article 2023
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Allaerts, D.J.N. (author), Quon, Eliot (author), Churchfield, Matt (author)
Reproducing realistic date- and site-specific unsteady wind conditions in large-eddy simulations is becoming increasingly useful in wind energy. How to run a large-eddy simulation to match observed conditions, however, remains an open research question. One approach that has received considerable attention is mesoscale-to-microscale coupling,...
journal article 2023
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Zoppini, G. (author), Michelis, Theodorus (author), Ragni, D. (author), Kotsonis, M. (author)
This work presents the first experimental characterization of the flow field in the vicinity of periodically spaced discrete roughness elements (DRE) in a swept wing boundary layer. The time-averaged velocity fields are acquired in a volumetric domain by high-resolution dual-pulse tomographic particle tracking velocimetry. Investigation of...
journal article 2023
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Della Posta, Giacomo (author), Blandino, M. (author), Modesti, D. (author), Salvadore, Francesco (author), Bernardini, M (author)
Microvortex generators are passive control devices smaller than the boundary layer thickness that energise the boundary layer to prevent flow separation with limited induced drag. In this work, we use direct numerical simulations (DNS) to investigate the effect of the Reynolds number in a supersonic turbulent boundary layer over a microramp...
journal article 2023
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