scholarly journals Shock interaction with a deformable particle: Direct numerical simulation and point-particle modeling

2013 ◽  
Vol 113 (1) ◽  
pp. 013504 ◽  
Author(s):  
Y. Ling ◽  
A. Haselbacher ◽  
S. Balachandar ◽  
F. M. Najjar ◽  
D. S. Stewart
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Point Particle ◽  
Shock Interaction ◽  
Particle Modeling ◽  
Deformable Particle

scholarly journals Direct numerical simulation analysis of local flow topology in a particle-laden turbulent channel flow

2010 ◽  
Vol 653 ◽  
pp. 35-56 ◽  
Author(s):  
M. J. BIJLARD ◽  
R. V. A. OLIEMANS ◽  
L. M. PORTELA ◽  
G. OOMS
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Direct Numerical Simulation ◽  
Channel Flow ◽  
Coupling Effect ◽  
Turbulent Channel Flow ◽  
Viscous Sublayer ◽  
Point Particle ◽  
Flow Topology ◽  
Local Flow

The results of point-particle Eulerian–Lagrangian direct numerical simulation (DNS) calculations of dilute particle-laden turbulent channel flow are used to study the effect of the particles on the local flow topology. It is found that in the viscous sublayer, the flow becomes increasingly more two-dimensional as the two-way coupling effect (due to interaction between particles and fluid flow) increases with increasing particle load. Beyond the viscous sublayer the modifications in flow topology are not strongly related to the preferential concentration of particles in the flow field, which is in contrast to previous channel flow simulations. The effect of particles on the turbulent flow beyond the viscous sublayer is mostly a result of the overall changing near-wall dynamics of the fluid flow.

A direct comparison of particle-resolved and point-particle methods in decaying turbulence

2018 ◽  
Vol 850 ◽  
pp. 336-369 ◽  
Author(s):  
M. Mehrabadi ◽  
J. A. K. Horwitz ◽  
S. Subramaniam ◽  
A. Mani
Keyword(s):  
Numerical Simulation ◽  
Particle Acceleration ◽  
Direct Numerical Simulation ◽  
Volume Fraction ◽  
Fluid Velocity ◽  
Point Particle ◽  
Particle Methods ◽  
Particle Model ◽  
Second Moment ◽  
Acceleration Model

We use particle-resolved direct numerical simulation (PR-DNS) as a model-free physics-based numerical approach to validate particle acceleration modelling in gas-solid suspensions. To isolate the effect of the particle acceleration model, we focus on point-particle direct numerical simulation (PP-DNS) of a collision-free dilute suspension with solid-phase volume fraction $\unicode[STIX]{x1D719}=0.001$ in a decaying isotropic turbulent particle-laden flow. The particle diameter $d_{p}$ in the suspension is chosen to be the same as the initial Kolmogorov length scale $\unicode[STIX]{x1D702}_{0}$ ($d_{p}/\unicode[STIX]{x1D702}_{0}=1$) in order to overlap with the regime where PP-DNS is valid. We assess the point-particle acceleration model for two different particle Stokes numbers, $St_{\unicode[STIX]{x1D702}}=1$ and 100. For the high Stokes number case, the Stokes drag model for particle acceleration under-predicts the true particle acceleration. In addition, second moment quantities which play key roles in the physical evolution of the gas–solid suspension are not correctly captured. Considering finite Reynolds number corrections to the acceleration model improves the prediction of the particle acceleration probability density function and second moment statistics of the point-particle model compared with the particle-resolved simulation. We also find that accounting for the undisturbed fluid velocity in the acceleration model can be of greater importance than using the most appropriate acceleration model for a given physical problem.

Direct Numerical Simulation of the Motion of Particles Larger Than the Kolmogorov Scale in a Homogeneous Isotropic Turbulence

2008 ◽  
Author(s):  
Cedric Corre ◽  
Jean-Luc Estivalezes ◽  
Stephane Vincent ◽  
Olivier Simonin
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Isotropic Turbulence ◽  
Industrial Applications ◽  
Point Particle ◽  
Solid Particles ◽  
Physical Forcing ◽  
Kolmogorov Length Scale ◽  
Free Case ◽  
Grid Points

Predicting interactions between particles and a surrounding viscous fluid is the concern of many environmental and industrial applications. A Direct Numerical Simulation (DNS) of dilute isotropic turbulent particulate flow has been conducted in a periodic box, with 1283 grid points. The objective is to understand the modification of isotropic turbulence due to dispersed solid particles by analyzing the DNS results. Previous numerical simulations have been, for the most part, limited to the point-particle regime. On the opposite, in these simulations, the diameter of the particles is larger than the Kolmogorov length scale. In order to maintain a constant turbulent kinetic energy, a physical forcing scheme is implemented. Thereby, statistics on the characteristics of the particles are more reliable. Furthermore, interactions between particles are treated via a repulsing force, consequently, simulations are four-way coupling. Simulations are performed with a fictitious domain approach and with the penalty method. For solving the velocity-pressure coupling, an augmented Lagrangian optimization algorithm is used. Results present the influence of the particle phase on the turbulence spectrum. Moreover, the comparison with particle-free case is particularly interesting notably about the anisotropy of the flow caused by the presence of the particles.

scholarly journals Particle-resolved direct numerical simulation of homogeneous isotropic turbulence modified by small fixed spheres

2016 ◽  
Vol 796 ◽  
pp. 40-85 ◽  
Author(s):  
A. W. Vreman
Keyword(s):  
Numerical Simulation ◽  
Kinetic Energy ◽  
Direct Numerical Simulation ◽  
Velocity Gradient ◽  
Dissipation Rate ◽  
Point Particle ◽  
Turbulence Kinetic Energy ◽  
Spherical Particles ◽  
Particle Model ◽  
Particle Simulations

A statistically stationary homogeneous isotropic turbulent flow modified by 64 small fixed non-Stokesian spherical particles is considered. The particle diameter is approximately twice the Kolmogorov length scale, while the particle volume fraction is 0.001. The Taylor Reynolds number of the corresponding unladen flow is 32. The particle-laden flow has been obtained by a direct numerical simulation based on a discretization of the incompressible Navier–Stokes equations on 64 spherical grids overset on a Cartesian grid. The global (space- and time-averaged) turbulence kinetic energy is attenuated by approximately 9 %, which is less than expected. The turbulence dissipation rate on the surfaces of the particles is enhanced by two orders of magnitude. More than 5 % of the total dissipation occurs in only 0.1 % of the flow domain. The budget of the turbulence kinetic energy has been computed, as a function of the distance to the nearest particle centre. The budget illustrates how energy relatively far away from particles is transported towards the surfaces of the particles, where it is dissipated by the (locally enhanced) turbulence dissipation rate. The energy flux towards the particles is dominated by turbulent transport relatively far away from particles, by viscous diffusion very close to the particles, and by pressure diffusion in a significant region in between. The skewness and flatness factors of the pressure, velocity and velocity gradient have also been computed. The global flatness factor of the longitudinal velocity gradient, which characterizes the intermittency of small scales, is enhanced by a factor of six. In addition, several point-particle simulations based on the Schiller–Naumann drag correlation have been performed. A posteriori tests of the point-particle simulations, comparisons in which the particle-resolved results are regarded as the standard, show that, in this case, the point-particle model captures both the turbulence attenuation and the fraction of the turbulence dissipation rate due to particles reasonably well, provided the (arbitrary) size of the fluid volume over which each particle force is distributed is suitably chosen.

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