Searched for: author:"Delfos, R."
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Tokgoz, S. (author), Elsinga, G.E. (author), Delfos, R. (author), Westerweel, J. (author)
We report on the experimental investigation of the large-scale instantaneous flow structures in turbulent Taylor–Couette flow using tomographic particle image velocimetry. The results indicate three distinct regimes for counter-rotating flow within a shear Reynolds number range of 11000<ReS<47000 . Close to only inner cylinder rotation,...
journal article 2020
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Benschop, H.O.G. (author), Greidanus, A.J. (author), Delfos, R. (author), Westerweel, J. (author), Breugem, W.P. (author)
We investigate the deformation of a linear viscoelastic compliant coating in a turbulent flow for a wide range of coating parameters. A one-way coupling model is proposed in which the turbulent surface stresses are expressed as a sum of streamwise-travelling waves with amplitudes determined from the stress spectra of the corresponding flow...
journal article 2019
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Delfos, R. (author)
Stromingsleer is de naam van het vakgebied dat ‘stromende media’ beschrijft. Dat medium kan lucht of water zijn, maar ook olie, mayonaise, of lucht-watermengsels. Als we het vakgebied wat ruimer nemen dan stromen zand- of suikerkorrels ook. Kortom, alles stroomt, of zoals Heraclitus het rond 500 vóór Christus verwoordde: ‘Panta Rhei’. En dat is...
book chapter 2017
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Greidanus, A.J. (author), Delfos, R. (author), Westerweel, J. (author)
The flow motions in the turbulent boundary layer between water and a rowing boat initiate a turbulent skin friction. Reducing this skin friction results in better rowing performances. A Taylor-Couette (TC) facility was used to verify the power losses due to velocity fluctuations P<sub>V′</sub> in relation to the total power, as a function of...
conference paper 2016
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Alidai, A. (author), Greidanus, A.J. (author), Delfos, R. (author), Westerweel, J. (author)
The transition from the laminar to the turbulent regime in linearly stable shear flows, for example, pipe and plane Couette flows, occurs abruptly with no precursor. The evolution of turbulent spots has been studied to better understand the dynamics of this transition and the onset of turbulence. These studies have mostly focused on pipe flows...
journal article 2015
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In linearly stable shear flows like pipe and plane Couette flows, the transition from the laminar to the turbulent regime occurs abruptly. To better understand this transition, the time evolution of turbulent patches, created by controlled finite amplitude perturbations, have been studied in the literature. These studies mostly focused on pipe flows...
conference paper 2015
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Alidai, A. (author), Delfos, R. (author)
In linearly stable shear ?ows like pipe and plane Couette ?ows, the transition from the laminar to the turbulent regime occurs abruptly. To better understand this transition, the time evolution of turbulent patches, created by controlled ?nite amplitude perturbations, have been studied in the literature. These studies mostly focused on pipe ?ows...
conference paper 2015
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Friction measurements were performed in a Taylor-Couette setup. Drag reduction was obtained with a riblet surface and indicated a drag reduction for a wide range of shear Reynolds numbers, with a maximum of 5.3% at Re_s=47000 (s+=14). Tomographic PIV verified that the friction coefficients are strongly related to the flow regimes and structures....
conference paper 2015
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Greidanus, A. (author), Delfos, R. (author), Tokgoz, S. (author), Westerweel, J. (author)
Friction measurements were performed in a Taylor-Couette setup. Drag reduction was obtained with a riblet surface and indicated a drag reduction for a wide range of shear Reynolds numbers, with a maximum of 5.3% at Re_s=47000 (s+=14). Tomographic PIV verified that the friction coefficients are strongly related to the flow regimes and structures....
conference paper 2015
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Greidanus, A.J. (author), Delfos, R. (author), Tokgoz, S. (author), Westerweel, J. (author)
A Taylor–Couette facility was used to measure the drag reduction of a riblet surface on the inner cylinder. The drag on the surfaces of the inner and outer cylinders is determined from the measured torque when the cylinders are in exact counter-rotation. The three velocity components in the instantaneous flow field were obtained by tomographic...
journal article 2015
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Greidanus, A.J. (author), Delfos, R. (author), Tokgoez, S. (author), Westerweel, J. (author)
Low drag surfaces are often desired in many industries with applications in open and closed channel flows, such as ship hulls and pipe flows. Drag reduction is a phenomenon that can have substantial energy savings, resulting in ecological and economical benefits. We use a Taylor-Couette facility as experimental instrument to measure the drag...
conference paper 2015
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Birvalski, M. (author), Tummers, M. (author), Delfos, R. (author), Henkes, R.A.W.M. (author)
The technique for obtaining detailed velocity fields in a wavy liquid layer in stratified air/water pipe flow is described in this paper. By combining Particle Image Velocimetry (PIV) with an interface detection technique, the velocity field is resolved in the whole liquid layer. Furthermore, since the shape of the interface is resolved at each...
conference paper 2013
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Greidanus, A.J. (author), Delfos, R. (author), Westerweel, J. (author)
The largest part of hydrodynamic drag during rowing, sailing or canoeing is the turbulent skin friction (80-90%). Higher velocities can be achieved by reducing the friction drag as a result of surface treatment. This research focuses on the development, characterization, and testing of drag-reducing surfaces, like nano- and micro-structured...
journal article 2012
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Tokgoz, S. (author), Elsinga, G.E. (author), Delfos, R. (author), Westerweel, J. (author)
journal article 2012
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Zverkhovskyi, O. (author), van Terwisga, T.J.C. (author), Delfos, R. (author), Westerweel, J. (author)
conference paper 2012
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Harleman, M.J.W. (author), Delfos, R. (author), Van Terwisga, T.J.C. (author), Westerweel, J. (author)
Dispersion and preferential concentration of small, low Stokes number bubbles in horizontal turbulent channel flow is studied by DNS and experiments. A DNS of turbulent channel flow at Re = 360 with Lagrangian tracking of one-way coupled bubbles (d < n, St = 1.3×10?3) shows that equilibrium bubble concentration profiles can be described by a...
conference paper 2011
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Warncke, N.G.W. (author), Delfos, R. (author), Ooms, G. (author), Westerweel, J. (author)
In this work we study the preferential concentration of small particles in the turbulent wake behind a spherical-cap object. We present a model predicting the mean particle concentration in the near-wake as a function of the characteristic Stokes number of the problem, the turbulence level and the Froude number. We compare the model with our...
conference paper 2011
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Greidanus, A.J. (author), Delfos, R. (author), Westerweel, J. (author)
We use a Taylor-Couette facility to study the drag reducing effects of commercial surface products at high shear Reynolds numbers (Res) under perfect couter-rotating conditions (riwi=rowo). The correlation between torque contribution of the von Karman flow and shear Reynolds number is investigated. At this moment no significant drag changes are...
conference paper 2011
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Slot, H.J. (author), Moore, P. (author), Delfos, R. (author), Boersma, B.J. (author)
In this paper we present the experimental results of a detailed investigation of the flow and acoustic properties of a turbulent jet with Mach number 0·75 and Reynolds number 3·5 103. We describe the methods and experimental procedures followed during the measurements, and subsequently present the flow field and acoustic field. The experiment...
journal article 2009
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Hunt, J.C.R. (author), Delfos, R. (author), Eames, I. (author), Perkins, R.J. (author)
journal article 2007
Searched for: author:"Delfos, R."
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