One-particle two-time diffusion in three-dimensional homogeneous isotropic turbulence

2005 ◽  
Vol 17 (3) ◽  
pp. 035104 ◽  
Author(s):  
D. R. Osborne ◽  
J. C. Vassilicos ◽  
J. D. Haigh
Keyword(s):  
Isotropic Turbulence ◽  
Three Dimensional ◽  
Homogeneous Isotropic Turbulence

Direct Numerical Simulations of Colliding Particles Suspended in Homogeneous Isotropic Turbulence

2009 ◽  
Author(s):  
M. Ernst ◽  
M. Sommerfeld
Keyword(s):  
Numerical Simulations ◽  
Isotropic Turbulence ◽  
Three Dimensional ◽  
Stokes Number ◽  
Direct Numerical Simulations ◽  
Spherical Particles ◽  
Collision Rate ◽  
Homogeneous Isotropic Turbulence ◽  
And Performance ◽  
Fluid Behaviour

Direct numerical simulations of particle-laden homogeneous isotropic turbulence are performed to characterize the collision rate as a function of different particle properties. The fluid behaviour is computed using a three-dimensional Lattice Boltzmann Method including a spectral forcing scheme to generate the turbulence field. Under assumption of mass points, the transport of spherical particles is modelled in a Lagrangian frame of reference. In the simulations the influence of the particle phase on the fluid flow is neglected. The detection and performance of inelastic interparticle collisions are based on a deterministic collision model. Different studies with monodisperse particles are considered. According to the executed simulations, particles with small Stokes number possess a collision rate similar to the prediction of Saffman and Turner [1], whereas particles with larger Stokes numbers behave similarly to the theory of Abrahamson [2].

scholarly journals On the velocity distribution in homogeneous isotropic turbulence: correlations and deviations from Gaussianity

2011 ◽  
Vol 676 ◽  
pp. 191-217 ◽  
Author(s):  
MICHAEL WILCZEK ◽  
ANTON DAITCHE ◽  
RUDOLF FRIEDRICH
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Isotropic Turbulence ◽  
Single Point ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Homogeneous Isotropic Turbulence ◽  
Navier Stokes Equation ◽  
Conditional Averaging

We investigate the single-point probability density function of the velocity in three-dimensional stationary and decaying homogeneous isotropic turbulence. To this end, we apply the statistical framework of the Lundgren–Monin–Novikov hierarchy combined with conditional averaging, identifying the quantities that determine the shape of the probability density function. In this framework, the conditional averages of the rate of energy dissipation, the velocity diffusion and the pressure gradient with respect to velocity play a key role. Direct numerical simulations of the Navier–Stokes equation are used to complement the theoretical results and assess deviations from Gaussianity.

Kármán–Howarth solutions of homogeneous isotropic turbulence

2021 ◽  
Vol 932 ◽  
Author(s):  
L. Djenidi ◽  
R.A. Antonia
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Three Dimensional ◽  
Order Moment ◽  
Homogeneous Isotropic Turbulence ◽  
The Difference ◽  
Decaying Turbulence ◽  
The Impact ◽  
Good Agreement

The Kármán–Howarth equation (KHEq) is solved using a closure model to obtain solutions of the second-order moment of the velocity increment, $S_2$ , in homogeneous isotropic turbulence (HIT). The results are in good agreement with experimental data for decaying turbulence and are also consistent with calculations based on the three-dimensional energy spectrum for decaying HIT. They differ, however, from those for forced HIT, the difference occurring mainly at large scales. This difference is attributed to the fact that the forcing generates large-scale motions which are not compatible with the KHEq. As the Reynolds number increases, the impact of forcing on the small scales decreases, thus allowing the KHEq and spectrally based solutions to agree well in the range of scales unaffected by forcing. Finally, the results show that the two-thirds law is compatible with the KHEq solutions as the Reynolds number increases to very large, if not infinite, values.

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