Federico Toschi | Eindhoven University of Technology (original) (raw)
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Papers by Federico Toschi
Physical Review Letters, 2001
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Physics of Fluids, 2005
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Journal of Fluid Mechanics, 2007
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Physical Review Letters, 2000
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Europhysics Letters (epl), 2005
A modified lattice Boltzmann model with a stochastic relaxation mechanism mimicking "virtual'' co... more A modified lattice Boltzmann model with a stochastic relaxation mechanism mimicking "virtual'' collisions between free-streaming particles and solid walls is introduced. This modified scheme permits to compute plane channel flows in satisfactory agreement with analytical results over a broad spectrum of Knudsen numbers, ranging from the hydrodynamic regime, all the way to quasi-free flow regimes up to Kn 30.
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Physical Review Letters, 2006
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Physics of Fluids, 2005
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Physics of Fluids, 2006
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Journal of Fluid Mechanics, 2006
We present the results of direct numerical simulations of heavy particle transport in homogeneous... more We present the results of direct numerical simulations of heavy particle transport in homogeneous, isotropic, fully developed turbulence, up to resolution 5123512^35123 ($R_\lambda\approx 185$). Following the trajectories of up to 120 million particles with Stokes numbers, StStSt, in the range from 0.16 to 3.5 we are able to characterize in full detail the statistics of particle acceleration. We show that: ({\it i}) The root-mean-squared acceleration armrmsa_{\rm rms}armrms sharply falls off from the fluid tracer value already at quite small Stokes numbers; ({\it ii}) At a given StStSt the normalised acceleration armrms/(epsilon3/nu)1/4a_{\rm rms}/(\epsilon^3/\nu)^{1/4}armrms/(epsilon3/nu)1/4 increases with RlambdaR_\lambdaRlambda consistently with the trend observed for fluid tracers; ({\it iii}) The tails of the probability density function of the normalised acceleration a/armrmsa/a_{\rm rms}a/armrms decrease with StStSt. Two concurrent mechanisms lead to the above results: preferential concentration of particles, very effective at small StStSt, and filtering induced by the particle response time, that takes over at larger StStSt.
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Physical Review E, 2006
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Physics of Fluids, 2005
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Physics of Fluids, 1999
Well defined scaling laws clearly appear in wall bounded turbulence, even very close to the wall,... more Well defined scaling laws clearly appear in wall bounded turbulence, even very close to the wall, where a distinct violation of the refined Kolmogorov similarity hypothesis (RKSH) occurs together with the simultaneous persistence of scaling laws. A new form of RKSH for the wall region is here proposed in terms of the structure functions of order two which, in physical terms, confirms the prevailing role of the momentum transfer towards the wall in the near wall dynamics.
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Physics Reports-review Section of Physics Letters, 2004
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Physical Review Letters, 1999
We find that, near the center of the channel the values of zetap/zeta3\zeta_p /\zeta_3zetap/zeta3 up to p=7p=7p=7 are con... more We find that, near the center of the channel the values of zetap/zeta3\zeta_p /\zeta_3zeta_p/zeta_3 up to p=7p=7p=7 are consistent with the assumption of homogeneous/isotropic turbulence. Moving towards the boundaries, we observe a growth of intermittency which appears to be related to an intensified presence of ordered vortical structures. In fact, the behaviour along the normal-to-wall direction of suitably normalized scaling exponents shows a remarkable correlation with the local strength of the Reynolds stress and with the \rms value of helicity density fluctuations. We argue that the clear transition in the nature of intermittency appearing in the region close to the wall, is related to a new length scale which becomes the relevant one for scaling in high shear flows.
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Journal of Fluid Mechanics, 2002
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Physical Review E, 2002
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Journal of Turbulence, 2006
The statistical properties of fluid particles transported by a fully developed turbulent flow are... more The statistical properties of fluid particles transported by a fully developed turbulent flow are investigated by means of high resolution direct numerical simulations. Single trajectory statistics is investigated in a time range spanning more than three decades, from less than a tenth of the Kolmogorov timescale up to one large-eddy turnover time. Acceleration and velocity statistics show a neat quantitative agreement with recent experimental results. Trapping effects in vortex filaments give rise to enhanced small-scale intermittency on Lagrangian observables.
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Physical Review Letters, 2001
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Physics of Fluids, 2005
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Journal of Fluid Mechanics, 2007
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Physical Review Letters, 2000
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Europhysics Letters (epl), 2005
A modified lattice Boltzmann model with a stochastic relaxation mechanism mimicking "virtual'' co... more A modified lattice Boltzmann model with a stochastic relaxation mechanism mimicking "virtual'' collisions between free-streaming particles and solid walls is introduced. This modified scheme permits to compute plane channel flows in satisfactory agreement with analytical results over a broad spectrum of Knudsen numbers, ranging from the hydrodynamic regime, all the way to quasi-free flow regimes up to Kn 30.
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Physical Review Letters, 2006
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Physics of Fluids, 2005
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Physics of Fluids, 2006
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Journal of Fluid Mechanics, 2006
We present the results of direct numerical simulations of heavy particle transport in homogeneous... more We present the results of direct numerical simulations of heavy particle transport in homogeneous, isotropic, fully developed turbulence, up to resolution 5123512^35123 ($R_\lambda\approx 185$). Following the trajectories of up to 120 million particles with Stokes numbers, StStSt, in the range from 0.16 to 3.5 we are able to characterize in full detail the statistics of particle acceleration. We show that: ({\it i}) The root-mean-squared acceleration armrmsa_{\rm rms}armrms sharply falls off from the fluid tracer value already at quite small Stokes numbers; ({\it ii}) At a given StStSt the normalised acceleration armrms/(epsilon3/nu)1/4a_{\rm rms}/(\epsilon^3/\nu)^{1/4}armrms/(epsilon3/nu)1/4 increases with RlambdaR_\lambdaRlambda consistently with the trend observed for fluid tracers; ({\it iii}) The tails of the probability density function of the normalised acceleration a/armrmsa/a_{\rm rms}a/armrms decrease with StStSt. Two concurrent mechanisms lead to the above results: preferential concentration of particles, very effective at small StStSt, and filtering induced by the particle response time, that takes over at larger StStSt.
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Physical Review E, 2006
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Physics of Fluids, 2005
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Physics of Fluids, 1999
Well defined scaling laws clearly appear in wall bounded turbulence, even very close to the wall,... more Well defined scaling laws clearly appear in wall bounded turbulence, even very close to the wall, where a distinct violation of the refined Kolmogorov similarity hypothesis (RKSH) occurs together with the simultaneous persistence of scaling laws. A new form of RKSH for the wall region is here proposed in terms of the structure functions of order two which, in physical terms, confirms the prevailing role of the momentum transfer towards the wall in the near wall dynamics.
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Physics Reports-review Section of Physics Letters, 2004
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Physical Review Letters, 1999
We find that, near the center of the channel the values of zetap/zeta3\zeta_p /\zeta_3zetap/zeta3 up to p=7p=7p=7 are con... more We find that, near the center of the channel the values of zetap/zeta3\zeta_p /\zeta_3zeta_p/zeta_3 up to p=7p=7p=7 are consistent with the assumption of homogeneous/isotropic turbulence. Moving towards the boundaries, we observe a growth of intermittency which appears to be related to an intensified presence of ordered vortical structures. In fact, the behaviour along the normal-to-wall direction of suitably normalized scaling exponents shows a remarkable correlation with the local strength of the Reynolds stress and with the \rms value of helicity density fluctuations. We argue that the clear transition in the nature of intermittency appearing in the region close to the wall, is related to a new length scale which becomes the relevant one for scaling in high shear flows.
Bookmarks Related papers MentionsView impact
Journal of Fluid Mechanics, 2002
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Physical Review E, 2002
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Journal of Turbulence, 2006
The statistical properties of fluid particles transported by a fully developed turbulent flow are... more The statistical properties of fluid particles transported by a fully developed turbulent flow are investigated by means of high resolution direct numerical simulations. Single trajectory statistics is investigated in a time range spanning more than three decades, from less than a tenth of the Kolmogorov timescale up to one large-eddy turnover time. Acceleration and velocity statistics show a neat quantitative agreement with recent experimental results. Trapping effects in vortex filaments give rise to enhanced small-scale intermittency on Lagrangian observables.
Bookmarks Related papers MentionsView impact