Large-eddy simulation of heavy particle dispersion in wall-bounded turbulent flows

2015 ◽  
Author(s):  
M.V. Salvetti
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flows ◽  
Heavy Particle ◽  
Particle Dispersion ◽  
Eddy Simulation ◽  
Large Eddy

EVALUATION OF PARTICLE STOCHASTIC SEPARATED FLOW MODELS VIA LARGE EDDY SIMULATION

2010 ◽  
Vol 21 (07) ◽  
pp. 867-890 ◽  
Author(s):  
BING WANG ◽  
HUIQIANG ZHANG ◽  
XILIN WANG
Keyword(s):  
Time Series ◽  
Large Eddy Simulation ◽  
Turbulent Flows ◽  
Spatial Dispersion ◽  
Computational Cost ◽  
Separated Flow ◽  
Particle Dispersion ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy

This paper evaluates three widely used particle stochastic separated flow (SSF) models through large eddy simulation (LES) of gas-particle two-phase turbulent flows over a backward-facing step. The ability of the models to predict mean velocities, fluctuating velocities, and spatial dispersion of particles are carefully examined in comparison with LES reference results. Evaluation shows that the improved time-series SSF model produces good predictions on mean and fluctuating velocities in the particle phase which highly agree with LES results. However, the time-series SSF model has higher computational cost. Further, compared with the two other models, the time-series SSF model predicts better results on the spatial dispersion of particles. It has an overall advantage in terms of accuracy and efficiency in predicting velocity moments and particle dispersion even without the presence of so many particles. The dependence of different SSF models on the number of computational particles in a converged flow field is also discussed. This paper is useful for the selection and application of SSF models in numerical simulations of practical two-phase turbulent flows.

Large-eddy simulation of turbulence and particle dispersion inside the canopy roughness sublayer

2014 ◽  
Vol 753 ◽  
pp. 499-534 ◽  
Author(s):  
Ying Pan ◽  
Marcelo Chamecki ◽  
Scott A. Isard
Keyword(s):  
Large Eddy Simulation ◽  
Drag Coefficient ◽  
Turbulent Flows ◽  
Fungal Spores ◽  
Particle Dispersion ◽  
Roughness Sublayer ◽  
Quadrant Analysis ◽  
Eddy Simulation ◽  
Velocity Statistics ◽  
Large Eddy

AbstractModelling the dispersion of small particles such as fungal spores, pollens and small seeds inside and above plant canopies is important for many applications. Transport of these particles is driven by strongly inhomogeneous and non-Gaussian turbulent flows inside the canopy roughness sublayer, the region that extends from the ground to approximately three canopy heights. A large-eddy simulation (LES) approach is refined to study particle dispersion within and above the canopy region. Effects of plant reconfiguration are parameterized through a velocity-dependent drag coefficient, which is shown to be critical for accurate reproduction of velocity statistics and mean spore concentrations. The model yields predictions of turbulence statistics that are in good agreement with measurements. This is particularly true of the stress fractions carried by strong events, as revealed by standard quadrant analysis of the resolved velocity fluctuations, which is a known weakness of earlier LES studies of canopy flow using a constant drag coefficient. Experimental data on spore dispersal inside and above a maize canopy are reproduced successfully as well. Characteristics of the particle plume are analysed using LES results, and a pre-existing theoretical framework is adapted to model particle dispersal above the canopy. The results suggest that the plume above the canopy can be approximated using a simple analytical solution if the fraction of spores that escape the canopy region is known. Source height and gravitational settling have strong effects on the plume inside the canopy region and consequently determine the escape fraction. These effects are parameterized in the theoretical model by using the escape fraction to rescale the source strength.

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