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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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Eisma, H.E. (author), Westerweel, J. (author), van de Water, W. (author)A scalar emanating from a point source in a turbulent boundary layer does not mix homogeneously, but is organized in large regions with little variation of the concentration: uniform concentration zones. We measure scalar concentration using laser-induced fluorescence and, simultaneously, the three-dimensional velocity field using tomographic...journal article 2021
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Laskari, A. (author), McKeon, Beverley J. (author)The probability density function (p.d.f.) of the streamwise velocity has been shown to indicate the presence of uniform momentum zones in wall-bounded turbulent flows. Most studies on the topic have focused on the instantaneous characteristics of this p.d.f. In this work, we show how the use of time-resolved particle image velocimetry data...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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Samie, M. (author), Baars, W.J. (author), Rouhi, A. (author), Schlatter, P. (author), Örlü, R. (author), Marusic, I. (author), Hutchins, N. (author)Opposition-control of the energetic cycle of near wall streaks in wall-bounded turbulence, using numerical approaches, has shown promise for drag reduction. For practical implementation, real-time opposition control is only realizable if there is a degree of coherence between the turbulent velocities passing a sensor and the target point...journal article 2020
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Dijkshoorn, Dominic (author)Organic Rankine Cycle (ORC) Power Plants can be of greatimportance in the energy transition as they are suitable for converting wasteheat to power and can utilize renewable energy for their operation. To improvethe efficiency of ORC Power Plants, the physical phenomena inside thesemachines must be understood....master thesis 2020
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CUI, Guangyao (author), PAN, C. (author), WU, Di (author), Ye, Q. (author), WANG, Jinjun (author)The characteristics of turbulent boundary layer over streamwise aligned drag reducing riblet surface under zero-pressure gradient are investigated using particle image velocimetry. The formation and distribution of large-scale coherent structures and their effect on momentum partition are analyzed using two-point correlation and probability...journal article 2019
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Mayer, Jonathan (author), Rubio Carpio, A. (author), Ragni, D. (author)The present work analyses broadband noise scattering from permeable trailing edges with identical micro-structure but under a change of temperature. Experiments are performed in an anechoic wind tunnel using a NACA0018 airfoil at chord-based Reynolds numbers between 1.88 × 10<sup>5</sup> and 3.14 × 10<sup>5</sup> and no incidence. A...journal article 2019
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De Petter, Christophe (author)Shock-Wave/Turbulent-Boundary Layer Interactions (SWTBLI) often occur in applications of technological interest. The associated inherent low-frequency unsteadiness dictates the use of Large-Eddy Simulation (LES) approaches to resolve the interaction, which unavoidably implies a very high computational cost. For this reason, no well-resolved long...master thesis 2019
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van Weersch, Yorin (author)Dimples are spherical indentations applied at a surface that have been found to yield a skin-friction drag reduction within a turbulent boundary layer. Shallow dimples have inherent advantages over traditional flow control techniques that require heavy active systems to be installed or pose maintenance problems. Proven drag-reducing mechanisms...master thesis 2017
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Patel, A. (author)Wall-bounded turbulence involving mixing of scalars, such as temperature or concentration fields, play an important role in many engineering applications. In applications with large temperature or concentration differences, the variation of scalar dependent thermos physical properties can be strong. In such cases the strong coupling between...doctoral thesis 2017
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Pecnik, Rene (author), Patel, A. (author)We derive an alternative formulation of the turbulent kinetic energy equation for flows with strong near-wall density and viscosity gradients. The derivation is based on a scaling transformation of the Navier-Stokes equations using semi-local quantities. A budget analysis of the semi-locally scaled turbulent kinetic energy equation shows that...journal article 2017
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Avallone, F. (author), van der Velden, W.C.P. (author), Ragni, D. (author)Far-field noise and flow field over a novel curved trailing-edge serration (named as iron-shaped serration) are investigated. Spectra of the far-field broadband noise, directivity plots and the flow-field over the iron-shaped serration are obtained from numerical computations performed using a compressible Lattice-Boltzmann solver. The new...journal article 2017
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Ragni, D. (author), Avallone, F. (author), van der Velden, W.C.P. (author)The far-field noise and flow field of a novel curved trailing-edge serration (i.e. iron-shaped) are investigated. Spectra of the far-field broadband noise, directivity plots and the flow-field over the iron-shaped serration are obtained from numerical computations performed using a compressible Lattice-Boltzmann solver. The new design is...conference paper 2017
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van Campenhout, O.W.G. (author)Any reduction in vehicle drag or fluid resistance provides a potential of substantial energy savings, with obvious benefits to the economy, environment and overall industrial competitiveness. Although various experimental studies have confirmed the potential drag reduction of dimpled surfaces in a turbulent boundary layer (BL), the working...master thesis 2016
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van Campenhout, O.W.G. (author), van Nesselrooij, M. (author), Veldhuis, L.L.M. (author), van Oudheusden, B.W. (author), Schrijer, F.F.J. (author)Although various experimental studies have confirmed a potential drag reduction of dimpled surfaces in turbulent boundary layers, the working mechanism behind the effect remains largely unresolved. The goal of this experimental study is to reveal the flow structures that could explain this drag reduction. To this end, flow visualizations over...conference paper 2016
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- Ghaemi, S. (author), Scarano, F. (author) journal article 2013
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Novara, M. (author)This research deals with advanced developments in 3D particle image velocimetry based on the tomographic PIV technique (Tomo-PIV). The latter is a relatively recent measurement technique introduced by Elsinga et al. in 2005, which is based on the tomographic reconstruction of particle tracers in three-dimensional space from a small number of its...doctoral thesis 2013
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Gillissen, J.J.J. (author)Using direct numerical simulations of turbulent Couette flow, we predict drag reduction in suspensions of neutrally buoyant fluid spheres, of diameter larger than the Kolmogorov length scale. The velocity fluctuations are enhanced in the streamwise direction, and reduced in the cross-stream directions, which is similar to the more studied case...journal article 2013
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- Elsinga, G.E. (author), Poelma, C. (author), Schröder, A. (author), Geisler, R. (author), Scarano, F. (author), Westerweel, J. (author) journal article 2012