Accurate Parallel Algorithm for Tracking Inertial Particles in Large-Scale Direct Numerical Simulations of Turbulence

2015 ◽  
pp. 522-527 ◽  
Author(s):  
Takashi Ishihara ◽  
Kei Enohata ◽  
Koji Morishita ◽  
Mitsuo Yokokawa ◽  
Katsuya Ishii
Keyword(s):  
Numerical Simulations ◽  
Parallel Algorithm ◽  
Large Scale ◽  
Direct Numerical Simulations ◽  
Inertial Particles

scholarly journals Inertial-particle accelerations in turbulence: a Lagrangian closure

2016 ◽  
Vol 798 ◽  
pp. 187-200 ◽  
Author(s):  
S. Vajedi ◽  
K. Gustavsson ◽  
B. Mehlig ◽  
L. Biferale
Keyword(s):  
Numerical Simulations ◽  
Numerical Data ◽  
Direct Numerical Simulations ◽  
Inertial Particles ◽  
Inertial Particle ◽  
Order Unity ◽  
Heavy Particles ◽  
Preferential Sampling ◽  
Closure Scheme ◽  
Light Particles

The distribution of particle accelerations in turbulence is intermittent, with non-Gaussian tails that are quite different for light and heavy particles. In this article we analyse a closure scheme for the acceleration fluctuations of light and heavy inertial particles in turbulence, formulated in terms of Lagrangian correlation functions of fluid tracers. We compute the variance and the flatness of inertial-particle accelerations and we discuss their dependency on the Stokes number. The closure incorporates effects induced by the Lagrangian correlations along the trajectories of fluid tracers, and its predictions agree well with results of direct numerical simulations of inertial particles in turbulence, provided that the effects induced by inertial preferential sampling of heavy/light particles outside/inside vortices are negligible. In particular, the scheme predicts the correct functional behaviour of the acceleration variance, as a function of $St$, as well as the presence of a minimum/maximum for the flatness of the acceleration of heavy/light particles, in good qualitative agreement with numerical data. We also show that the closure works well when applied to the Lagrangian evolution of particles using a stochastic surrogate for the underlying Eulerian velocity field. Our results support the conclusion that there exist important contributions to the statistics of the acceleration of inertial particles independent of the preferential sampling. For heavy particles we observe deviations between the predictions of the closure scheme and direct numerical simulations, at Stokes numbers of order unity. For light particles the deviation occurs for larger Stokes numbers.

Direct numerical simulations of supersonic compression-expansion slope with a multi-GPU parallel algorithm

2021 ◽  
Vol 179 ◽  
pp. 20-32
Author(s):  
Dequan Xu ◽  
Shibin Luo ◽  
Jiawen Song ◽  
Jian Liu ◽  
Wenbin Cao
Keyword(s):  
Numerical Simulations ◽  
Parallel Algorithm ◽  
Direct Numerical Simulations

scholarly journals Oscillatory migratory large-scale fields in mean-field and direct simulations

2009 ◽  
Vol 5 (S264) ◽  
pp. 197-201
Author(s):  
Dhrubaditya Mitra ◽  
Reza Tavakol ◽  
Axel Brandenburg ◽  
Petri J. Käpylä
Keyword(s):  
Magnetic Field ◽  
Numerical Simulations ◽  
Large Scale ◽  
Mean Field ◽  
Direct Numerical Simulations ◽  
Mhd Equations ◽  
Perfect Conductor ◽  
Large Scale Magnetic Field ◽  
Wedge Shape ◽  
Polarity Reversals

AbstractWe summarise recent results form direct numerical simulations of both non-rotating helically forced and rotating convection driven MHD equations in spherical wedge-shape domains. In the former, using perfect-conductor boundary conditions along the latitudinal boundaries we observe oscillations, polarity reversals and equatorward migration of the large-scale magnetic fields. In the latter we obtain angular velocity with cylindrical contours and large-scale magnetic field which shows oscillations, polarity reversals but poleward migration. The occurrence of these behviours in direct numerical simulations is clearly of interest. However the present models as they stand are not directly applicable to the solar dynamo problem. Nevertheless, they provide general insights into the operation of turbulent dynamos.

Settling regimes of inertial particles in isotropic turbulence

2014 ◽  
Vol 759 ◽  
Author(s):  
G. H. Good ◽  
P. J. Ireland ◽  
G. P. Bewley ◽  
E. Bodenschatz ◽  
L. R. Collins ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Isotropic Turbulence ◽  
Direct Numerical Simulations ◽  
Inertial Particles ◽  
Mean Square ◽  
Particle Inertia ◽  
Turbulent Eddies ◽  
Air Turbulence ◽  
Large Particles ◽  
Linear Drag

AbstractWe investigate the settling speeds and root mean square (r.m.s.) velocities of inertial particles in isotropic turbulence with gravity using experiments with water droplets in air turbulence from 32 loudspeaker jets and direct numerical simulations (DNS). The dependence on particle inertia, gravity and the scales of both the smallest and largest turbulent eddies is investigated. We isolate the mechanisms of turbulence settling modification and find that the reduced settling speeds of large particles in experiments are due to nonlinear drag effects. We demonstrate using DNS that reduced settling speeds with linear drag (e.g. see Nielsen, J. Sedim. Petrol., vol. 63, 1993, pp. 835–838) only arise in artificial flows that, by design, eliminate preferential sweeping by the eddies. Gravity and inertia both reduce the particle r.m.s. velocities and falling particles are more responsive to vertical than to horizontal fluctuations. The model by Wang & Stock (J. Atmos. Sci., vol. 50, 1993, pp. 1897–1913) captures these trends.

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