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Gul, M. (author), Elsinga, G.E. (author), Westerweel, J. (author)
This study investigates the effect of the Taylor-Couette geometry, namely the aspect ratio, Γ, and the gap width ratio, ƞ, on the torque hysteresis reported by [1]. Measurements were taken at two shear Reynolds numbers, Re s, of 5.5x10⁴ and 9x10⁴.The torque was recorded while decreasing or increasing the rotation frequency ratio a=-fo/fi,...
conference paper 2015
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Motivated by work on stagnation-point type exact solutions of the 3D Euler fluid equations by Gibbon [Gibbon et. al. Phys. D, 132, 497, (1999)] and the subsequent demonstration of finite-time blowup by Constantin [Constantin, Math. Res. Notices, 9, 455, (2000)] we introduce a one-parameter family of models of the 3D Euler equations on a 2D...
conference paper 2015
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We study the kinematic dynamo problem of a two dimensional turbulent flow with the third velocity component being advected as a passive scalar (2.5D flow). Both helical and nonhelical forcing is considered. The low-dimensionality of the system allows us to study it for a wide range of parameters of the system, here specifically the Reynolds...
conference paper 2015
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Hellendoorn, V.J. (author)
Communication is fundamental to human nature and underlies many of its successes as a species. In recent decades, the adoption of increasingly abstract software languages has supported many advances in computer science and software engineering. Although in many regards distinct from natural language, software language has proven surprisingly...
master thesis 2015
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We construct a unified shell model for stably stratified and convective turbulence. Shell model simulation of stably stratified flow in turbulent regime exhibit Bolgiano-Obukhbov (BO) scaling in which the kinetic energy spectrum varies as $k^{-11/5}$. However, simulation of convective turbulence shows Kolmogorov's spectrum. These results are...
conference paper 2015
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A three dimensional direct numerical simulation has been performed to study the flow around the asymmetric NACA-4412 wing at a moderate chord Reynolds number (Rec = 400, 000) with an angle of attack of 5◦ . The flow case under investigation poses numerous challenges for a numerical method due to the wide range of scales and complicated flow...
conference paper 2015
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A combined wind tunnel and computational study of grid-generated turbulence along the centreline shows that the close to -5/3 power law signature of energy spectra in the frequency domain originates in the production region close to the grid where the velocity derivative statistics become quite suddenly isotropic but also where the turbulent...
conference paper 2015
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This study looks at the spatio-temporal dynamics of the coherent structures found in under-expanded supersonic impinging jets from a circular nozzle at a pressure ratio of 3.4 and standoff distances of 2d and 5d. In these jets the development of coherent structures within the shear layer and their interaction with a standoff-shock are the...
conference paper 2015
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The 2d-Laser Cantilever Anemometer (2d-LCA) is an novel anemometer for two-dimensional velocity measurements in fluids. It uses a mico-structured cantilever with a specifically designed tip as a sensing element and is capable of performing measure- ments with extremely high temporal (≈ 100kHz) and spatial (≈ 140μm) resolutions. Another big...
conference paper 2015
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We present data from direct numerical simulations of homogeneous isotropic decaying turbulence showing both the non-equilibrium and the classical dissipation scalings reported in wind-tunnel experiments of both regular and fractal grid-generated turbulence, i.e. Cε ∼ (Re0/Reλ)n with n of order unity and Cε ∼ constant, respectively (Re0 and Reλ...
conference paper 2015
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We are investigating a droplet-laden flow in an air-filled turbulence chamber, forced by speaker-driven air jets. The speakers are running in a random manner; yet they allow us to control and define the statistics of the turbulence. We study the motion of droplets with tunable size in a turbulent flow, mimicking the early stages of raindrop...
conference paper 2015
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Hollenberg, F. (author)
Bending of dual-phase (DP) steels has introduced new issues concerning the analysis by finite element (FE) modelling. During the investigation of the microstructure of a DP1000 steel, it is found that there is crack formation at lower bending angles and elongations than would be expected based on the forming limit curves (FLCs). The results of...
master thesis 2015
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The dynamics of the boundary layers of temperature and velocity are the key to deeper understanding of turbulent transport of heat and momentum in thermal convection. Here, the structure of the skin friction field at the bottom and top plates of a Rayleigh-B\'{e}nard convection setup is investigated. We therefore analyze data obtained in direct...
conference paper 2015
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Three spatially periodic travelling wave exact coherent states are presented for channel flow. Two of the flows, which are asymmetric with respect to the channel centreplane, are derived by homotopy from solutions for channel flow subject to a spanwise rotation investigated by [1]. The third flow satisfies a half-turn rotational symmetry about a...
conference paper 2015
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The edge state solution in pipe flow at Re=2200 is calculated numerically. The solution has the form of spatially localized puff-like structure drifting downstream. In the moving frame it is represented by a steady average flow and time-periodic pulsation flow. It is shown, that the Kelvin-Helmholtz instability mechanism is not valid for...
conference paper 2015
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Rayleigh-Bénard convection is a canonical system for the investigation of buoyancy-driven natural convection phenomena which abound in nature and technology. Under the influence of rotation and depending on the system parameters, the flow exhibits different regimes with disparate heat transfer characteristics even in the turbulent state. The...
conference paper 2015
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Clouds are one of the major sources of uncertainty in climate prediction.The present work is to study the dynamics of orographic clouds. We considered a planar turbulent wall jet with off source volumetric heating as an appropriate low order fluid-dynamical model for studying the turbulence and entrainment in orographic-clouds. Entrainment was...
conference paper 2015
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We study through high resolution numerical simulations unknown features of a random velocity field based on the so-called multiplicative chaos, previously proposed in the literature to model turbulence. We investigate the influence of the intermittency parameter, observing the behaviour of the field as it is changed. In this way, we can...
conference paper 2015
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The interaction of different scales is among the most interesting and challenging features in turbulence research. Existing approaches used for scaling analysis such as structure-function and Fourier spectrum method have their respective limitations, for instance scale mixing, i.e. the so-called infrared and ultraviolet effects. To make...
conference paper 2015
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We perform direct simulation of a statistically steady jets and plume and present the value of the entrainment coefficient decomposed into 1) turbulence production; 2) buoyancy effects; and 3) deviations from self-similarity. We explain theoretically how the two cases are linked and present a generalisation valid for forced and lazy plumes.
conference paper 2015
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