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Tsinober, A. (author), Vedula, P. (author), Yeung, P.K. (author)
The properties of acceleration fluctuations in isotropic turbulence are studied in direct numerical simulations (DNS) by decomposing the acceleration as the sum of local and convective contributions (aL = ?u/?t and aC = u??u), or alternatively as the sum of irrotational and solenoidal contributions [aI = ??(p/?) and aS = ??2u]. The main emphasis...
journal article 2001
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Li, Y. (author), McLaughlin, J.B. (author), Kontomaris, K. (author), Portela, L. (author)
This paper presents results for the behavior of particle-laden gases in a small Reynolds number vertical channel down flow. Results will be presented for the effects of particle feedback on the gas-phase turbulence and for the concentration profile of the particles. The effects of density ratio, mass loading, and particle inertia will be...
journal article 2001
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Manceau, R. (author), Hanjali?, K. (author)
A new approach to modeling the effects of a solid wall in one-point second-moment (Reynolds-stress) turbulence closures is presented. The model is based on the relaxation of an inhomogeneous (near-wall) formulation of the pressure–strain tensor towards the chosen conventional homogeneous (far-from-a-wall) form using the blending function ?, for...
journal article 2001
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Van Prooijen, B.C. (author), Uijttewaal, W.S.J. (author)
The development of large coherent structures in a shallow mixing layer is analyzed. The results are validated with experimental data obtained from particle tracking velocimetry. The mean flow field is modeled using the self-similarity of the velocity profiles. The characteristic features of the down-stream development of a shallow mixing layer...
journal article 2002
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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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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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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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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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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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Humble, R.A. (author), Scarano, F. (author), Van Oudheusden, B.W. (author)
The unsteady flow features of a series of two-dimensional, planar base flows are examined, within a range of low-supersonic Mach numbers in order to gain a better understanding of the effects of compressibility on the organized global dynamics. Particle image velocimetry is used as the primary diagnostic tool in order to characterize the...
journal article 2007
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Wackers, J. (author), Koren, J. (author)
journal article 2007
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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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Van Reeuwijk, M. (author), Jonker, H.J.J. (author), Hanjali?, K. (author)
journal article 2008
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Van Reeuwijk, M. (author), Jonker, H.J.J. (author), Hanjali?, K. (author)
journal article 2008
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Mortensen, P.H. (author), Andersson, H.I. (author), Gillissen, J.J.J. (author), Boersma, B.J. (author)
The dynamical behavior of tiny elongated particles in a directly simulated turbulent flow field is investigated. The ellipsoidal particles are affected both by inertia and hydrodynamic forces and torques. The time evolution of the particle orientation and translational and rotational motions in a statistically steady channel flow is obtained for...
journal article 2008
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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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Grosse, S. (author), Schröder, W. (author)
Wall-shear stress results from the relative motion of a fluid over a body surface as a consequence of the no-slip condition of the fluid in the vicinity of the wall. To determine the two-dimensional wall-shear stress distribution is of utter importance in theoretical and applied turbulence research. In this article, characteristics of the Micro...
journal article 2009
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Van Balen, W. (author), Uijttewaal, W.S.J. (author), Blanckaert, K. (author)
Large-eddy simulation (LES) is performed of a curved open-channel flow over topography based on the laboratory experiment by Blanckaert [“Topographic steering, flow circulation, velocity redistribution and bed topography in sharp meander bends,” Water Resour. Res., doi:10.1029/2009WR008303 (in press)] . In the experiment, the large-scale bed...
journal article 2010
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Fraanje, P.R. (author), Rice, J. (author), Verhaegen, M. (author), Doelman, N. (author)
Efficient and optimal prediction of frozen flow turbulence using the complete observation history of the wavefront sensor is an important issue in adaptive optics for large ground-based telescopes. At least for the sake of error budgeting and algorithm performance, the evaluation of an accurate estimate of the optimal performance of a particular...
journal article 2010
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