Experiments and Simulations on Turbulence Modification by Dispersed Particles

1994 ◽  
Vol 47 (6S) ◽  
pp. S44-S48 ◽  
Author(s):  
John K. Eaton
Keyword(s):  
Numerical Simulations ◽  
Gas Phase ◽  
Fine Particles ◽  
Isotropic Turbulence ◽  
Homogeneous Isotropic Turbulence ◽  
Preferential Concentration ◽  
Turbulence Modification ◽  
Dispersed Particles ◽  
Simple Flows ◽  
Highly Strained

Experiments and direct numerical simulations on simple flows have been performed to examine the attenuation of gas-phase turbulence by fine particles. The experiments were performed in a developing boundary layer and in a fully developed channel flow. Both showed significant turbulence attenuation for mass loading ratios greater than 10%. Numerical simulations on homogeneous/isotropic turbulence show similar levels of turbulence attenuation. Both experiments and simulations have demonstrated the importance of preferential concentration in which particles are collected in highly strained regions of the flow. Two-equation models for turbulence attenuation have been found to be inadequate when preferential concentration occurs.

Particle Dispersion in Fine Scales of Homogeneous Isotropic Turbulence

2007 ◽  
Author(s):  
M. Sato ◽  
M. Tanahashi ◽  
T. Miyauchi
Keyword(s):  
Isotropic Turbulence ◽  
Major Axis ◽  
Stokes Number ◽  
High Energy ◽  
Energy Dissipation Rate ◽  
Particle Dispersion ◽  
Fine Scale ◽  
Number Density ◽  
Homogeneous Isotropic Turbulence ◽  
Preferential Concentration

Direct numerical simulations of homogeneous isotropic turbulence laden with particles have been conducted to clarify the relationship between particle dispersion and coherent fine scale eddies in turbulence. Dispersion of 106 particles are analyzed for several particle Stokes numbers. The spatial distributions of particles depend on their Stokes number, and the Stokes number that causes preferential concentration of particles is closely related to the time scale of coherent fine scale eddies in turbulence. On the plane perpendicular to the rotating axes of fine scale eddies, number density of particle with particular Stokes number is low at the center of the fine scale eddy, and high in the regions with high energy dissipation rate around the eddy. The maximum number density can be observed at about 1.5 to 2.0 times the eddy radius on the major axis of the fine scale eddy.

A Dual-Scale LES Subgrid Model for Turbulent Liquid/Gas Phase Interface Dynamics

2015 ◽  
Author(s):  
Marcus Herrmann
Keyword(s):  
Surface Tension ◽  
Numerical Simulations ◽  
Gas Phase ◽  
Isotropic Turbulence ◽  
Phase Interface ◽  
Spatial Filtering ◽  
Direct Numerical Simulations ◽  
Scale Model ◽  
Interface Dynamics ◽  
Dual Scale

Turbulent liquid/gas phase interface dynamics are at the core of many applications. For example, in atomizing flows, the properties of the resulting liquid spray are determined by the interplay of fluid and surface tension forces. The resulting dynamics typically span 4–6 orders of magnitude in length scales, making direct numerical simulations exceedingly expensive. This motivates the need for modeling approaches based on spatial filtering or ensemble averaging. In this paper, a dual-scale modeling approach is presented to describe turbulent two-phase interface dynamics in a large-eddy-simulation-type spatial filtering context. To close the unclosed terms related to the phase interface arising from filtering the Navier-Stokes equation, a resolved realization of the phase interface dynamics is explicitly filtered. This resolved realization is maintained on a high-resolution over-set mesh using a Refined Local Surface Grid approach [1] employing an un-split, geometric, bounded, and conservative Volume-of-Fluid method [2]. The required model for the resolved realization of the interface advection velocity includes the effects of sub-filter surface tension, dissipation, and turbulent eddies. Results of the dual-scale model are compared to recent direct numerical simulations of an interface in homogeneous isotropic turbulence [3].

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