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A friction factor in a fully developed pipe flow is measured very accurately over wide range Reynolds number from 103 to 107 at the high Reynolds number facility in AIST,NMIJ. Also a velocity profile is measured by using a LDV up to 106. From the comparison between a velocity profile and the friction factor, we found that a log-law profile is...conference paper 2015
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We study the Lagrangian dynamics of semi-flexible particles in laminar as well as in homogeneous and isotropic turbulent flows by means of analytically solvable stochastic models and direct numerical simulations. The statistics of the bending angle is qualitatively different in laminar and turbulent flows and exhibits a strong dependence on the...conference paper 2015
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This work explores a route to unify Reynolds averaged (RANS) and large eddy simulation (LES). The approach is to use a slightly modified Reynolds stress transport model for any mesh resolution. The model is formulated in terms of both total kinetic energy and modeled kinetic energy in such a way that the RST model correctly reproduces RANS...conference paper 2015
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Thermal flows are ubiquitous in natural and industrial systems, this is why they have been studied for decades. In these kinds of flows, an important quantity is the local heat flux, but it remains experimentally nearly unstudied since it is difficult to measure it. We introduce a new local convective heat flux probe, based on a joint...conference paper 2015
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Turbulence models are expected to satisfy the conflicting requirements of accuracy and computational efficiency. Here we discuss a new model that was recently developed in order to accurately and efficiently describe the dynamic of a clouds of tracers particles in Large Eddy Simulations of homogeneous and isotropic turbulent flows. The models...conference paper 2015
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We report the results from two distinct direct numerical simulations (DNS) of turbulent Rayleigh-Bénard convection (RBC) for Rayleigh number of 10^5 and Prandtl number of 0.7 in a laterally unbounded domain confined between two horizontal isothermal plates with no-slip and free-slip boundary conditions respectively. The central aim of the...conference paper 2015
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Laser Doppler velocimetry (LDV) is a powerful experimental tool that finds increasing application in industrial research and product development. For example, LDV may be used to support the development of water, heat, and cooling meters as well as the design and validation of the associated testing and calibration facilities. For such...conference paper 2015
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We investigated the rotation of non-spherical particles (rod-like and disk-like) in turbulent channel flow with focus on inertial effects. A direct numerical simulation (DNS) with an Eulerian-Lagrangian approach was performed. A wide range of particle aspect ratios, λ, ranging from 0.01 to 50 were considered for Stokes numbers St equal to 1 and...conference paper 2015
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We investigate the onset of chaotic reversals of thermal convection cell in a two–dimensional square cavity using direct numerical simulation. To our knowledge, the chaotic reversal motion at the lowest Rayleigh number is related to the unicellular motion in this system. As Rayleigh number increases, the two antisymmetric attractors, which arise...conference paper 2015
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Sharp transitions between potentially different turbulent states are unexpected because one might think that they should be washed out by the prevailing intense fluctuations and short coherence lengths and times. Contrary to this expectation, we found a sequence of such transitions in turbulent rotating Rayleigh-Bénard convection as the rotation...conference paper 2015
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Over the last decade wind tunnel experiments and numerical simulations have shown that steady spanwise mean velocity gradients are able to attenuate the growth of different types of boundary layer disturbances if introduced in a controlled way. In this paper different techniques to setup the spanwise mean velocity variations are reviewed and...conference paper 2015
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The directional change of a fluid particle can be measured by the angle between two subsequent particle displacement increments. At small values of the time-increment the so-defined angle is proportional to the curvature of the trajectory. At large values this coarse-grained curvature should be affected by the presence of solid no-slip walls...conference paper 2015
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The aim of the present study is to investigate the sedimentation of large non-colloidal spherical particles in both quiescent and turbulent environments. To this aim, Direct Numerical Simulations are performed using an Immersed Boundary Method to account for the dispersed phase. The solid volume fractions considered are in the range 0.5%-1.0%,...conference paper 2015
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We study effects of thin (10 nm) layers of adsorbed proteins on the water surface hydrodynamics. We show that extremely small concentrations of protein (less than 1 ppm) form strong viscoelastic layer at the water-air interface. This layer greatly reduces single particle dispersion on the surface perturbed by Faraday waves and turns disordered...conference paper 2015
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Leveque, E. (author), Naso, A. (author), (author)Longitudinal and transverse Lagrangian velocity increments are introduced as components along, and perpendicular to, the displacement of fluid particles during a time scale τ. These increments provide a new path to the characterization of Lagrangian statistics in homogeneous and isotropic turbulence, and allows us to establish some bridge with...conference paper 2015
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We investigate the response of energy flux in isotropic turbulence to step-function like perturbation in external forcing at large length scales. From both physical experiments and direct numerical simulations, we measured the evolution of the Eulerian velocity structure functions, such as $D_{LL}(r)$, $D_{NN}(r)$, before and after the...conference paper 2015
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We report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014...conference paper 2015
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The orientation distribution and rotations of anisotropic particles in turbulent flows play a key role in many applications ranging from icy clouds to papermaking and drag reduction in pipe flow. However, experimental access to time-resolved orientations of anisotropic particles has not been easy to achieve. The use of 3D printing opens up the...conference paper 2015
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In the current study we aim to go beyond the dissipative description of turbulent flows that is provided by eddy viscosity models for large-eddy simulation. As a starting point, we consider a general subgrid-scale model that is nonlinear in the velocity gradient. To reduce the number of degrees of freedom of the model, we propose a first...conference paper 2015
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Bubble dynamics in turbulent flows has been extensively studied using the point-bubble approximation. But when the carrier flow varies on length scales smaller than the bubble size, this approximation is no longer appropriate and one needs to resolve all the scales present in the two-phase flow. 3D Direct Numerical Simulations of turbulent...conference paper 2015
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