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van Vliet, E. (author)
doctoral thesis 2003
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Vrieling, A.J. (author)
This thesis deals with mixing of passive scalars in a turbulent flow. The passive scalars are released in a turbulent plane channel flow and interpreted as either non-reactive components or reactive components that are involved in a competitive-consecutive reaction system. The evolution of these passive scalars under influence of turbulent...
doctoral thesis 2003
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Holmen, J. (author), Hughes, T.J.R. (author), Oberai, A.A. (author), Wells, G.N. (author)
The variational multiscale method has been shown to perform well for large-eddy simulation (LES) of turbulent flows. The method relies upon a partition of the resolved velocity field into large- and small-scale components. The subgrid model then acts only on the small scales of motion, unlike conventional LES models which act on all scales of...
journal article 2004
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Geers, L.F.G. (author)
Because of their high efficiency and their ability to provide high heat transfer rates, impinging jets are applied for rapid cooling and heating in a wide variety of industrial processes. However, the physical phenomena controlling the heat transfer from impinging jets are to a large degree unknown. The goal of the present project was to gain a...
doctoral thesis 2004
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Kenjereš, S. (author), Hanjali?, K. (author), Bal, D. (author)
A magnetic field, imposed on turbulent flow of an electrically conductive fluid, is known to cause preferential damping of the velocity and its fluctuations in the direction of Lorentz force, thus leading to an increase in stress anisotropy. Based on direct numerical simulations (DNS), we have developed a model of magnetohydrodynamic (MHD)...
journal article 2004
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Hughes, T.J.R. (author), Wells, G.N. (author), Wray, A.A. (author)
Energy transfers within large-eddy simulation (LES) and direct numerical simulation (DNS) grids are studied. The spectral eddy viscosity for conventional dynamic Smagorinsky and variational multiscale LES methods are compared with DNS results. Both models underestimate the DNS results for a very coarse LES, but the dynamic Smagorinsky model is...
journal article 2004
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Groen, J.S. (author)
In this project a detailed experimental analysis was performed of the dynamic flow field in bubbly flows, with the purpose of determining local hydrodynamics and scale effects. Measurements were done in gas-liquid systems (air-water bubble columns) and in gas-solid systems (air-sand bubbing fluidized beds) of different size. Amongst others with...
doctoral thesis 2004
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Geers, L.F.G. (author), Tummers, M.J. (author), Hanjali?, K. (author)
To gain a better insight into the effects of eddy structure and their thermal imprint on the impinging surface, we applied several methods to identify coherent structures in two arrangements of multiple jets. High-resolution particle imaging velocimetry measurements of the instantaneous fluid velocity have been performed to provide data for...
journal article 2005
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Hartmann, H. (author)
This thesis aims at a contribution to reliable and accurate predictions of complex, multi-phase processes. The reader is presented detailed simulations on liquid and solid-liquid mixing using large eddy simulations (LES) including scalar mixing and particle transport in a Rushton turbine stirred tank geometry. Large eddy simulations have been...
doctoral thesis 2005
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Ooms, G. (author), Poesio, P. (author)
A theoretical model is presented for the effect of particle inertia and gravity on the turbulence in a homogeneous suspension. It is an extension of the one-fluid model developed by L’vov, Ooms, and Pomyalov [Phys. Rev. E 67, 046314 (2003)] , in which the effect of gravity was not considered. In the extended model the particles are assumed to...
journal article 2005
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Hofland, B. (author)
Layers of stone or rock are often applied around hydraulic structures to protect the sand bed from scouring. Determining the size of the rocks is complicated by the fact that the flow over a bed protection usually is non-uniform. This thesis describes two experimental series in which the stability of a single stone under non-uniform flows is...
doctoral thesis 2005
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Harteveld, W.K. (author)
The aim of the thesis is to contribute to the understanding of the hydrodynamics of the gravity driven bubbly flow that can be found in bubble columns. Special attention is paid to the large scale structures that have a strong impact on several key parameters such as the degree of mixing, mass and heat transfer. An experimental investigation has...
doctoral thesis 2005
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Panara, D. (author), Porta, M. (author), Schoenfeld, T. (author)
The use of wall functions has been investigated for LES and URANS numerical simulation in pulsating and oscillating channel flow applications. The results show that the wall function approach is accurate in the so-called quasi-steady regime but there are discrepancies with the experimental results in the intermediate frequency range. A special...
conference paper 2006
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De Hoogh, J. (author), Kuerten, J.G.M. (author)
To investigate the behavior of the concentration of a passive scalar in a turbulent flow with realistic high Schmidt numbers, one needs a very fine grid to capture all length-scales that are present in the concentration. An efficient method to increase the spatial resolution without a drastic raise of the computational costs is to apply a Local...
conference paper 2006
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De Borst, R. (author), Hulshoff, S.J. (author), Lenz, S. (author), Munts, E.A. (author), Van Brummelen, E.H. (author), Wall, W.A. (author)
The basic idea of multiscale methods, namely the decomposition of a problem into a coarse scale and a fine scale, has in an intuitive manner been used in engineering for many decades, if not for centuries. Also in computational science, large-scale problems have been solved, and local data, for instance displacements, forces or velocities, have...
conference paper 2006
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De Borst, R. (author), Hulshoff, S.J. (author), Lenz, S. (author), Munts, E.A. (author), Van Brummelen, E.H. (author), Wall, W.A. (author)
The basic idea of multiscale methods, namely the decomposition of a problem into a coarse scale and a fine scale, has in an intuitive manner been used in engineering for many decades, if not for centuries. Also in computational science, large-scale problems have been solved, and local data, for instance displacements, forces or velocities, have...
conference paper 2006
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Guermond, J.L. (author), Prudhomme, S. (author)
The purpose of this paper is to show that the Fourier-based Nonlinear Galerkin Method (NLGM) constructs suitable weak solutions to the periodic Navier--Stokes equations in three dimensions. We re-interpret NLGM as a Large-Eddy Simulation technique (LES) and we rigorously deduce a relationship between the mesh size and the large-eddy scale.
conference paper 2006
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Meyers, J. (author), Sagaut, P. (author)
A theoretical analysis is presented on the dependence of the standard and variational multi-scale Smagorinsky models on the proximity of the LES filter width Delta to the integral length scale of turbulence L on the one hand, and to the Kolmogorov scale eta on the other hand. Moreover modifications of the models are formulated, which respond...
conference paper 2006
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Thornber, B. (author), Drikakis, D. (author)
Simulations of three dimensional freely decaying homogeneous turbulence in a periodic cube have been used to examine in a detailed and quantitative manner the behaviour of a Large Eddy Simulation (LES) using implicit subgrid modelling. This paper details the form and behaviour of the implicit subgrid models for the Minmod and third order...
conference paper 2006
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Geurts, B.J. (author)
Non-uniform filtering of the Navier-Stokes equations expresses itself, next to the turbulent stresses, in additional closure terms known as commutator errors. These terms require explicit subgrid modeling if the non-uniformity of the filter is sufficiently pronounced. We derive expressions for the magnitude of the mean flux, the turbulent stress...
conference paper 2006
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