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van Nieuwburg, W.C.A.M. (author), van Spreuwel, B.J.J. (author), Tran, Minh Tâm Kevin (author), Yang, M.D. (author), Greidanus, A.J. (author), Mulder, G. (author), Tummers, M.J. (author), Westerweel, J. (author), Suijker, W. (author), van Wijk, R. (author)The principal aim of the work presented here is to investigate and demonstrate that a forward tilted rowing blade would result in a more efficient and effective motion of the blade through the water that would result in a higher boat speed when an equal input power is provided. A 1:5 scaled rowing boat is used to determine the performance of...journal article 2023
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Reijtenbagh, J. (author), Tummers, M.J. (author), Westerweel, J. (author)We report results on the instantaneous drag force on plates that are accelerated in a direction normal to the plate surface, which show that this force scales with the square root of the acceleration. This is associated with the generation and advection of vorticity at the plate surface. A new scaling law is presented for the drag force on...journal article 2023
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Tummers, M.J. (author), Schenker, M.C. (author), Delfos, R. (author), Twerda, A. (author), Westerweel, J. (author)Measurements were conducted in the fully developed turbulent flow in a pipe with internal diameter D at a Reynolds number of Re <sub>D</sub>= 1.6 × 10 <sup>5</sup> . The pipe walls were equipped with regularly spaced square ribs of relative height h/ D= 0.154 , while the pitch-to-roughness height was varied between p/ h= 1.67 and p/ h= 6.67 ....journal article 2023
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Huang, X. (author), Tummers, M.J. (author), van Veen, E.H. (author), Roekaerts, D.J.E.M. (author)The flamelet generated manifold (FGM) model is suitable for moderate or intense low oxygen dilution (MILD) combustion provided the flamelets underlying the manifold include the effects of strong dilution by products of the fuel/oxidizer mixture. Here we propose such an extended model based on the use of non-premixed flamelets diluted at the...journal article 2022
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Reijtenbagh, J. (author), Tummers, M.J. (author), Westerweel, J. (author)We present results on the instantaneous drag force acting on a rectangular plate that accelerates in a direction normal to the plate surface. Conventionally the drag force on an accelerating object is divided into a steady state term and an added mass term, which can both be time-dependent. However, for prolonged accelerations this theory...conference paper 2022
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Grift, E.J. (author), Tummers, M.J. (author), Westerweel, J. (author)This paper presents the results of the time resolved flow field measurements around a realistic rowing oar blade that moves along a realistic path through water. To the authors' knowledge no prior account of this complex flow field has been given. Simultaneously with the flow field measurements, the hydrodynamic forces acting on the blade...journal article 2021
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Chakkingal, M. (author), de Geus, Julia (author), Kenjeres, S. (author), Ataei Dadavi, I. (author), Tummers, M.J. (author), Kleijn, C.R. (author)We report numerical simulations of assisting and opposing mixed convection in a side-heated, side-cooled cavity packed with relatively large solid spheres. The mixed convection is generated by imposing a movement on the isothermal vertical walls, either in or opposite to the direction of natural convection flow. For a fluid Prandtl number of...journal article 2020
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Ataei Dadavi, I. (author), Chakkingal, M. (author), Kenjeres, S. (author), Kleijn, C.R. (author), Tummers, M.J. (author)This paper reports on an experimental study of mixed convection flow and heat transfer in a vented, differentially side-heated cubical cavity filled with a porous medium consisting of relatively large solid low-conductivity spheres. Rayleigh numbers and Reynolds numbers are varied over the ranges 6 × 10<sup>6</sup> < Ra < 7 × 10<sup>7<...journal article 2020
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Chakkingal, M. (author), Kenjeres, S. (author), Ataei Dadavi, I. (author), Tummers, M.J. (author), Kleijn, C.R. (author)We report numerical simulations of natural convection and conjugate heat transfer in a differentially heated cubical cavity packed with relatively large hydrogel beads (d/L=0.2) in a Simple Cubic Packing configuration. We study the influence of a spatially non-uniform, sinusoidally varying, wall temperature on the local flow and heat transfer...journal article 2020
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Chakkingal, M. (author), Schiavo, Sabino (author), Ataei Dadavi, I. (author), Tummers, M.J. (author), Kleijn, C.R. (author), Kenjeres, S. (author)We numerically investigate natural convection in a bottom-heated top-cooled cavity, fully and partially filled with adiabatic spheres (with diameter-to-cavity-size ratio d/L=0.2) arranged in a Simple Cubic Packing (SCP) configuration. We study the influence of packing height and location of porous media. We carry out the simulations using...journal article 2020
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Grift, E.J. (author), Tummers, M.J. (author), Overmars, E.F.J. (author), Westerweel, J. (author)We investigate the fluid motion generated by a moving rowing blade. The blade follows a complex path with rather strong acceleration and subsequent deceleration. The blade path is mimicked at a 1:2 scale in a large open-top water tank using a robot system. The tank is transparent, thus enabling full optical access for performing large-field...conference paper 2019
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Contreras, P. S. (author), Ataei Dadavi, I. (author), Speetjens, M. F.M. (author), Kleijn, C.R. (author), Tummers, M.J. (author), Clercx, H. J.H. (author)The present study concerns Lagrangian transport and (chaotic) advection in three-dimensional (3D) flows in cavities under steady and laminar conditions. The main goal is to investigate topological equivalences between flow classes driven by different forcing; streamline patterns and their response to nonlinear effects are examined. To this...journal article 2019
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Ataei Dadavi, I. (author), Chakkingal, M. (author), Kenjeres, S. (author), Kleijn, C.R. (author), Tummers, M.J. (author)This paper reports on an experimental study of natural convection in an enclosure that is heated at the bottom and cooled at the top, filled with a packed bed of relatively large solid spheres. Nusselt numbers were measured for various sphere conductivities, spheres sizes and sphere packings for Rayleigh numbers varying between 10<sup>7</sup>...journal article 2019
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Ataei Dadavi, I. (author), Rounaghi, Nima (author), Chakkingal, M. (author), Kenjeres, S. (author), Kleijn, C.R. (author), Tummers, M.J. (author)Flow and heat transfer in a differentially side heated cubic cavity filled with relatively large solid spheres forming a coarse porous medium have been studied experimentally. Nusselt numbers were measured for Rayleigh numbers between 1.9 × 10<sup>7</sup> and 1.7 × 10<sup>9</sup>, solid-to-fluid conductivity ratios between 0.32 and 618, and...journal article 2019
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Tummers, M.J. (author), Steunebrink, M. (author)This paper reports on an experimental study of the effects of surface roughness on the flow and heat transfer in cubical Rayleigh-Bénard convection cells for Rayleigh numbers between 10<sup>7</sup> and 10<sup>10</sup>. In the rough cells the top and bottom surfaces are equipped with square arrays of copper cubes. In line with other studies,...journal article 2019
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Lintmeijer, Lotte L. (author), Onneweer, John P.T. (author), Hofmijster, Mathijs J. (author), Wijgergangs, Willem A. (author), De Koning, Hans (author), Clairbois, Bert (author), Westerweel, J. (author), Grift, E.J. (author), Tummers, M.J. (author), van Soest, A.M.J. (author)To analyze on-water rowing performance, a valid determination of the power loss due to the generation of propulsion is required. This power los can be calculated as the dot product of the net water force vector ( <sup>~</sup> F <sub>w;o</sub> ) and the time derivative of the position vector of the point at the blade where <sup>~</sup> F <sub...journal article 2019
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Grift, E.J. (author), Vijayaragavan, N. B. (author), Tummers, M.J. (author), Westerweel, J. (author)We present results on the drag on, and the flow field around, a submerged rectangular normal flat plate, which is uniformly accelerated to a constant target velocity along a straight path. The plate aspect ratio is chosen to be to resemble an oar blade in (competitive) rowing, the sport which inspired this study. The plate depth, i.e. the...journal article 2019
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Numerical analysis of natural convection with conjugate heat transfer in coarse-grained porous mediaChakkingal, M. (author), Kenjeres, S. (author), Ataei Dadavi, I. (author), Tummers, M.J. (author), Kleijn, C.R. (author)We report numerical simulations of fluid natural convection with conjugate heat transfer in a bottom-heated, top-cooled cubical cavity packed with relatively large (d/L=0.2) solid spheres in a Body Centred Tetragonal (BCT) configuration. We study largely varying solid-to-fluid thermal conductivity ratios between 0.3 and 198, for a fluid...journal article 2019
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- Huang, X. (author), van Veen, E.H. (author), Tummers, M.J. (author), Roekaerts, D.J.E.M. (author) abstract 2018
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Huang, X. (author), Tummers, M.J. (author), Roekaerts, D.J.E.M. (author)Flameless combustion, named as Moderate or Intense Low-oxygen Dilution (MILD) combustion or high-temperature air combustion (HiTAC), is a promising technology to improve the thermal efficiency while suppressing NOx formation in combustion systems. Flameless combustion can occur when fresh air (and/or fuel)...abstract 2017
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