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Barrett, R. (author), Corpening, J. (author), Reasonover, C. (author)
This paper describes a new method for drag elimination and stall suppression via tangential synthetic jet actuators. This boundary layer control (BLC) method is shown to perform as well as continuous and normal synthetic jet BLC methods but without fouling difficulties, system-level complexity or extreme sensitivity to Reynolds number. Classical...
conference paper 2005
document
Abbas, A. (author), Dias, J. (author)
With the increase in fuel prices, flow control technologies are becoming of greater interest as being the means of achieving a technology quantum leap in the next generation of aircrafts, providing the means to achieve significant reduction in drag (fuel burn) and improvements in aircraft performance, shortening thus the path to accomplish the...
conference paper 2006
document
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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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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Den Toonder, J.M.J. (author)
doctoral thesis 1996
document
van der Hoeven, J.G.Th. (author)
doctoral thesis 2000
document
Gillissen, J.J.J. (author)
doctoral thesis 2008
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Van Raemdonck, G.M.R. (author)
Low drag bluff road vehicle design can be obtained effectively and efficiently with a three phase approach that uses numerical simulations, scaled wind tunnel experiments and full-scale road testing. By applying this generalised method, SideWings were developed for an improved trailer underbody flow and tails for the trailer's rear-end. A...
doctoral thesis 2012
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Harleman, M.J.W. (author)
Previous research has shown that the addition of gas bubbles to a turbulent boundary layer in water can reduce the local skin-friction drag by up to 80%. Application of this technique to ships seems promising, but to date no significant drag reductions are obtained on full-scale ships. More knowledge about the drag reduction mechanism is...
doctoral thesis 2012
document
Gillissen, J.J.J. (author), Boersma, B.J. (author), Mortensen, P.H. (author), Andersson, H.I. (author)
Turbulent fiber suspension channel flow is studied using direct numerical simulation. The effect of the fibers on the fluid mechanics is governed by a stress tensor, involving the distribution of fiber position and orientation. Properties of this function in channel flow are studied by computing the trajectories and orientations of individual...
journal article 2007
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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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Gillissen, J.J.J. (author), Hoving, J.P. (author)
Pipe flow experiments show that turbulent drag reduction in plug-flow of concentrated suspensions of macroscopic fibers is a self-similar function of the wall shear stress over the fiber network yield stress. We model the experimental observations, by assuming a central fiber network plug, whose radius is determined by the yield stress....
journal article 2012
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Zhao, L.H. (author), Andersson, H.I. (author), Gillissen, J.J.J. (author)
This letter reports on the pronounced turbulence modulations and the accompanying drag reduction observed in a two-way coupled simulation of particle-laden channel flow. The present results support the view that drag reduction can be achieved not only by means of polymeric or fiber additives but also with spherical particles.
journal article 2010
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Gillissen, J.J.J. (author)
Polymer-induced drag reduction is the phenomenon by which the friction factor of a turbulent flow is reduced by the addition of small amounts of high-molecular-weight linear polymers, which conformation in solution at rest can vary between randomly coiled and rodlike. It is well known that drag reduction is positively correlated to viscous...
journal article 2008
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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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Gillissen, J.J.J. (author), Boersma, B.J. (author), Mortensen, P.H. (author), Andersson, H.I. (author)
Fiber-induced drag reduction can be studied in great detail by means of direct numerical simulation [ J. S. Paschkewitz et al., J. Fluid Mech. 518, 281 (2004) ]. To account for the effect of the fibers, the Navier-Stokes equations are supplemented by the fiber stress tensor, which depends on the distribution function of fiber orientation angles....
journal article 2007
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Thuwis, G.A.A. (author), De Breuker, R. (author), Abdalla, M.M. (author), Gürdal, Z. (author)
The aim of the present work is to passively reduce the induced drag of the rear wing of a Formula One car at high velocity through aeroelastic tailoring. The angle-of-attack of the rear wing is fixed and is determined by the required downforce needed to get around a turn. As a result, at higher velocity, the amount of downforce and related...
journal article 2009
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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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Vilumbrales-Garcia, Rodrigo (author), Kurt, Melike (author), Weymouth, Gabriel D. (author), Ganapathisubramani, Bharathram (author)
The hydrodynamic influence of surface texture on static surfaces ranges from large drag penalties (roughness) to potential performance benefits (shark-like skin). Although it is of wide-ranging research interest, the impact of roughness on flapping systems has received limited attention. In this work, we explore the effect of roughness on the...
journal article 2024
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Benschop, H.O.G. (author), Guerin, A. J. (author), Brinkmann, A. (author), Dale, M. L. (author), Finnie, A. A. (author), Breugem, W.P. (author), Clare, A. S. (author), Stübing, D. (author), Price, C. (author), Reynolds, K. J. (author)
The manufacture and preliminary testing of a drag-reducing riblet texture with fouling-control properties is presented. The commercial fouling-release product Intersleek® 1100SR was modified to manufacture riblet-textured coatings with an embossing technology. Hydrodynamic drag measurements in a Taylor–Couette set-up showed that the modified...
journal article 2018
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