Wind tunnel measurements of the preferential concentration of inertial droplets in homogeneous isotropic turbulence

2012 ◽  
Vol 52 (6) ◽  
pp. 1373-1387 ◽  
Author(s):  
Colin P. Bateson ◽  
Alberto Aliseda
Keyword(s):  
Wind Tunnel ◽  
Isotropic Turbulence ◽  
Homogeneous Isotropic Turbulence ◽  
Preferential Concentration ◽  
Wind Tunnel Measurements

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.

Lift Force Effects on the Behavior of Bubbles in Homogeneous Isotropic Turbulence

2005 ◽  
Author(s):  
Mustapha Abbad ◽  
Benoiˆt Oesterle´
Keyword(s):  
Relative Velocity ◽  
Lift Force ◽  
Isotropic Turbulence ◽  
Stokes Number ◽  
Rise Velocity ◽  
Homogeneous Isotropic Turbulence ◽  
Preferential Concentration ◽  
Coupling Approximation ◽  
Lagrangian Tracking ◽  
Small Bubbles

The influence of lift forces on the dispersion of small bubbles is numerically studied in a homogeneous isotropic turbulence generated by random Fourier modes, under one-way coupling approximation. The effects of bubble Stokes number and mean relative velocity are investigated by computing the statistics from Lagrangian tracking of a large number of bubbles in many flow field realizations, and comparison is provided between the results obtained with and without taking the lift force into account. The effects of preferential concentration, which are known to reduce the terminal rise velocity of bubbles, are also investigated. The lift force is found to drastically modify the correlations and integral time scales of the fluid seen by the bubbles in their fluctuating motion, and to significantly enhance the accumulation of bubbles in high vorticity regions.

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.

The interference of two passive scalars in a homogeneous isotropic turbulent field

1989 ◽  
Vol 203 ◽  
pp. 273-287 ◽  
Author(s):  
H. Kaplan ◽  
N. Dinar
Keyword(s):  
Wind Tunnel ◽  
Time Evolution ◽  
Correlation Coefficient ◽  
Cross Correlation ◽  
Isotropic Turbulence ◽  
Homogeneous Isotropic Turbulence ◽  
Wind Tunnel Experiments ◽  
Passive Scalars ◽  
Turbulent Field ◽  
Good Agreement

In this work, we study the interference of two scalars diffusing in homogeneous isotropic turbulence. We use the method described by Kaplan & Dinar (1988b) to calculate the cross-correlation coefficient ρ between the concentration fluctuations of two sources. The dependence of ρ on the source separation, shapes and sizes, and its time evolution is calculated for different points in space. Results for the case of two line sources are compared with data from wind tunnel experiments (Warhaft 1984), and seen to be in good agreement. At the centreline ρ is shown to increase as overlap of the two plumes increases. ρ may be either negative or positive depending on the separation between the two sources.

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