Searched for: subject%3A%22Turbulent%255C+boundary%255C+layer%22
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Laguarda, L. (author)
doctoral thesis 2024
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Cimarelli, Andrea (author), Boga, Gabriele (author), Pavan, Anna (author), Costa, Pedro (author), Stalio, Enrico (author)
Direct numerical simulations of channel flow and temporal boundary layer at a Reynolds number Reτ=1500 are used to assess the scale-by-scale mechanisms of wall turbulence. From the peak of turbulence production embedded at the small scales of the near-wall region, spatially ascending reverse cascades are generated that move through self-similar...
journal article 2024
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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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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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Avallone, F. (author), Ragni, D. (author)
Noise reduction is one of the major challenges to the societal acceptance of wind turbines. Aerodynamic noise sources are the dominant ones, assuming that mechanical noise can be reduced by correct insulation and periodic maintenance of the gearbox and drive train and by adding insulating material in the wind-turbine nacelle. The dominant...
book chapter 2023
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Cimarelli, Andrea (author), Boga, Gabriele (author), Pavan, Anna (author), Costa, Pedro (author), Stalio, Enrico (author)
The geometrically complex mechanisms of energy transfer in the compound space of scales and positions of wall turbulent flows are investigated in a temporally evolving boundary layer. The phenomena consist of spatially ascending reverse and forward cascades from the small production scales of the buffer layer to the small dissipative scales...
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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Carrasco Grau, J. (author), van Campenhout, O.W.G. (author), Hartog, F.H. (author), van Nesselrooij, M. (author), Baars, W.J. (author), Schrijer, F.F.J. (author)
Chevron-shaped protrusions have been proposed in the literature for turbulent skin friction reduction. However, there is no consensus on the performance of this passive flow control technique; both an increase and a decrease in drag have been observed in previous studies. There is also no experimental evidence to support the working mechanism...
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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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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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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Siebols, Renko (author)
An experimental study is presented towards inner-scaled Helmholtz-Resonators (HRs) as a passive turbulent boundary layer (TBL) flow control method. Using acoustic pressure-velocity coupling at the orifice of the HR, it is aimed to attenuate the kinetic energy of the grazing turbulence to reduce the mean skin friction. The HRs are tuned towards...
master thesis 2022
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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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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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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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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
Searched for: subject%3A%22Turbulent%255C+boundary%255C+layer%22
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