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Dignum, M. (author)
journal article 2015
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We address two issues of paradigmatic nature. The first one, among other things, concerns the fact how it is possible to have predominant vortex stretching mostly due to the largest eigen-strain without predominant alignment of vorticity ω with the eigen-vector λ1 corresponding to the largest eigen-strain Λ1. The second is about the paradigmatic...
conference paper 2015
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We have conducted hot wire anemometry measurements of six different axisymmetric turbulent wakes which demonstrate the existence in all these wakes of non-equilibrium mean flow profile scalings and of the underlying self-preservation and non-equilibrium dissipation scalings. These mean flow profile scalings are different from those of all...
conference paper 2015
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This paper presents the results of a study between two types of forcing, namely steady blowing and a tripwire, on the control of laminar separated boundary layers. The analysis focuses on the differences in the transition process between these two types of forcing. This effect will be studied using direct numerical simulation. The main...
conference paper 2015
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Lashgari, I. (author), Picano, F. (author), Breugem, W.P. (author), Brandt, L. (author)
Inertial regimes in a channel flow of suspension of finite-size neutrally buoyant particles are studied for a wide range of Reynolds numbers: 500 Re 5000, and particle volume fractions: 0 0:3. The flow is classified in three different regimes according to the phase-averaged stress budget across the channel [2]. The laminar viscous regime at low...
conference paper 2015
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We investigate the transport of both passive and active scalars in fully developed turbulent axisymmetric jets and plumes using data from direct numerical simulation. In both cases we simulate the response of the flow to an instantaneous increase in the scalar flux at the source and our focus is on the determination of the rate at which the...
conference paper 2015
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Dokter, R.G. (author)
Even in a bicycle friendly infrastructure as the Netherlands, lack of space is a continually rising problem. Re-urbanization describes the increasing population of especially young adults in the urban environments of conurbation ‘de Randstad’. These young adults have a changing perception on mobility and shift away from car usage in favor of...
master thesis 2015
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Direct numerical simulations of natural convection in liquid metal within rectangular box heated uniformly from below with uniform strong vertical magnetic field are conducted. The main aim is to explore the possibilities and mechanisms of convection instabilities in such flows. The effects of parameter range on the flow structure, i.e....
conference paper 2015
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We report the observations from turbulent thermal Rayleigh-Benard convection experiment with a two-phase liquid-vapor binary mixture. Evaporation/condensation processes in a turbulent convection are accompanied by the formation of cloud like structures above the liquid-vapor interface. We also found that a liquid film condensation on the...
conference paper 2015
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Kumar, N. (author), Abdi, F.F. (author), Trzesniewski, B. (author), Smith, W.A. (author), Planken, P.C.M. (author), Adam, A.J.L. (author)
We demonstrate emission of terahertz pulses from a BiVO4/Au thin film interface, illuminated with femtosecond laser pulses. Based on the experimental observations, we propose that the most likely cause of the THz emission is the Photo-Dember effect caused by the standing wave intensity distribution formed at the BiVO4/Au interfaces.
journal article 2015
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We present combined experimental and numerical studies of the heat transfer of paramagnetic or diamagnetic fluid inside a differentially heated cubical enclosure subjected to the magnetic field gradients of different strength and orientation. In contrast to the previously reported studies in literature, which observed solely laminar flow regimes...
conference paper 2015
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Active drag reduction of a turbulent boundary layer has been experimentally investigated using periodic blowing through one array of streamwise slits. Local skin-friction drag exhibits a strong dependence on control parameters, including the blowing amplitude A+ and frequency f +. A maximum drag reduction of almost 70% has been achieved at x+=33...
conference paper 2015
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A method for the triple decomposition of fluctuating velocity in a multiscale flow, suitable for a spatiotemporal data set, is presented. It is applied to experimental data gathered by means of particle image velocimetry (PIV). The basic properties of the decomposed parts are shown. The presented method is then used to perform a conditional...
conference paper 2015
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Morales Velasquez, S. (author)
Multiple frameworks and procedures are used in organizations to analyse and assess risks in the most efficient way possible. COBIT, COSO or ISO as some of the most popular frameworks used to evaluate enterprise threats, but each of them offer an independent view on risks that are not the best solution for chains or well stablished organization...
master thesis 2015
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We investigate the behavior of flows, including turbulent flows, driven by a horizontal body-force and subject to a vertical magnetic field, with the following question in mind: for very strong applied magnetic field, is the flow mostly two-dimensional, with remaining weak three-dimensional fluctuations, or does it become exactly 2D, with no...
conference paper 2015
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The interaction between the large-scale velocity fluctuations (uL) and the small-scale velocity gradient phenomena, such as dissipation and the vortex stretching term, are examined in a turbulent free-shear flow. The difference between the probability density functions of these small-scale quantities conditioned on the sign of uL is quantified...
conference paper 2015
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Overtoom, M.E. (author), Hekkert, P.P.M. (author)
Houses were among the first structures that were built, and remain the most common type of building today. The design of housing has been the subject of architecture, while from a psychological point of view the meaning of home has been a major subject of research. These two different viewpoints are combined in this research to provide a tool...
abstract 2015
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In the present abstract, DNS results obtained for turbulent plane Couette flow with wall-normal transpiration velocity are presented. Important equations valid in such a flow are derived, describing the total shear stress and the relation between the friction velocities at the lower and upper wall. These expressions are of importance, as there...
conference paper 2015
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Turbulent secondary flow in straight open ducts with rectangular cross-section are studied numerically by means of pseudo- spectral direct numerical simulation (DNS). Similarly to the corresponding closed duct flows, the mean streamwise vorticity pattern in turbulent open duct flows were found to be the statistical footprint of the most probable...
conference paper 2015
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The optimal transient growth process in a particle-laden channel flow is studied under the influence of the linear feedback control. The equilibrium Eulerian approach with the assumption that the particles are small and spherical is adopted. The effect of initial distribution of particles on the optimal transient growth of perturbations is...
conference paper 2015
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