Large-eddy simulation (LES) of the large scale bubble plume

2009 ◽  
Vol 64 (11) ◽  
pp. 2692-2704 ◽  
Author(s):  
Mahesh T. Dhotre ◽  
Bojan Niceno ◽  
Brian L. Smith ◽  
Marco Simiano
Keyword(s):  
Large Eddy Simulation ◽  
Large Scale ◽  
Bubble Plume ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Sensitivity of local air quality to the interplay between small- and large-scale circulations: a large-eddy simulation study

2017 ◽  
Vol 17 (11) ◽  
pp. 7261-7276 ◽  
Author(s):  
Tobias Wolf-Grosse ◽  
Igor Esau ◽  
Joachim Reuder
Keyword(s):  
Air Pollution ◽  
Air Quality ◽  
Large Eddy Simulation ◽  
Air Pollutants ◽  
Large Scale ◽  
Wind Speeds ◽  
Street Level ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Air Pockets

Abstract. Street-level urban air pollution is a challenging concern for modern urban societies. Pollution dispersion models assume that the concentrations decrease monotonically with raising wind speed. This convenient assumption breaks down when applied to flows with local recirculations such as those found in topographically complex coastal areas. This study looks at a practically important and sufficiently common case of air pollution in a coastal valley city. Here, the observed concentrations are determined by the interaction between large-scale topographically forced and local-scale breeze-like recirculations. Analysis of a long observational dataset in Bergen, Norway, revealed that the most extreme cases of recurring wintertime air pollution episodes were accompanied by increased large-scale wind speeds above the valley. Contrary to the theoretical assumption and intuitive expectations, the maximum NO2 concentrations were not found for the lowest 10 m ERA-Interim wind speeds but in situations with wind speeds of 3 m s−1. To explain this phenomenon, we investigated empirical relationships between the large-scale forcing and the local wind and air quality parameters. We conducted 16 large-eddy simulation (LES) experiments with the Parallelised Large-Eddy Simulation Model (PALM) for atmospheric and oceanic flows. The LES accounted for the realistic relief and coastal configuration as well as for the large-scale forcing and local surface condition heterogeneity in Bergen. They revealed that emerging local breeze-like circulations strongly enhance the urban ventilation and dispersion of the air pollutants in situations with weak large-scale winds. Slightly stronger large-scale winds, however, can counteract these local recirculations, leading to enhanced surface air stagnation. Furthermore, this study looks at the concrete impact of the relative configuration of warmer water bodies in the city and the major transport corridor. We found that a relatively small local water body acted as a barrier for the horizontal transport of air pollutants from the largest street in the valley and along the valley bottom, transporting them vertically instead and hence diluting them. We found that the stable stratification accumulates the street-level pollution from the transport corridor in shallow air pockets near the surface. The polluted air pockets are transported by the local recirculations to other less polluted areas with only slow dilution. This combination of relatively long distance and complex transport paths together with weak dispersion is not sufficiently resolved in classical air pollution models. The findings have important implications for the air quality predictions over urban areas. Any prediction not resolving these, or similar local dynamic features, might not be able to correctly simulate the dispersion of pollutants in cities.

Comparative Large Eddy Simulation study of a large-scale buoyant fire

2011 ◽  
Vol 47 (9) ◽  
pp. 1197-1208 ◽  
Author(s):  
G. H. Yeoh ◽  
S. C. P. Cheung ◽  
J. Y. Tu ◽  
T. J. Barber
Keyword(s):  
Large Eddy Simulation ◽  
Simulation Study ◽  
Large Scale ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Large-eddy simulation of ash deposition in a large-scale laboratory furnace

2019 ◽  
Vol 37 (4) ◽  
pp. 4409-4418 ◽  
Author(s):  
Min-min Zhou ◽  
John C. Parra-Álvarez ◽  
Philip J. Smith ◽  
Benjamin J. Isaac ◽  
Jeremy N. Thornock ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Large Scale ◽  
Ash Deposition ◽  
Laboratory Furnace ◽  
Eddy Simulation ◽  
Large Eddy

Application of Near Wall Model to Large Eddy Simulation Based on Boundary Layer Approximation

2006 ◽  
Author(s):  
Takashi Takata ◽  
Akira Yamaguchi ◽  
Masaaki Tanaka ◽  
Hiroyuki Ohshima
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Frequency Characteristic ◽  
Large Scale ◽  
Plane Channel ◽  
Boundary Layer Approximation ◽  
Eddy Simulation ◽  
Turbulent Statistics ◽  
Large Eddy ◽  
Near Wall

Turbulent statistics near a structural surface, such as a magnitude of temperature fluctuation and its frequency characteristic, play an important role in damage progression due to thermal stress. A Large Eddy Simulation (LES) has an advantage to obtain the turbulent statistics especially in terms of the frequency characteristic. However, it still needs a great number of computational cells near a wall. In the present paper, a two-layer approach based on boundary layer approximation is extended to an energy equation so that a low computational cost is achieved even in a large-scale LES analysis to obtain the near wall turbulent statistics. The numerical examinations are carried out based on a plane channel flow with constant heat generation. The friction Reynolds numbers (Reτ) of 395 and 10,000 are investigated, while the Prandtl number (Pr) is set to 0.71 in each analysis. It is demonstrated that the present method is cost-effective for a large-scale LES analysis.

Large Eddy Simulation of Self-Sustained Cavity Oscillation for Subsonic and Supersonic Flows

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
K. M. Nair ◽  
S. Sarkar
Keyword(s):  
Large Eddy Simulation ◽  
Shear Layer ◽  
Acoustic Waves ◽  
Large Scale ◽  
Hydrodynamic Instability ◽  
Supersonic Flows ◽  
Large Scale Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Scale Structures

The primary objective is to perform a large eddy simulation (LES) using shear improved Smagorinsky model (SISM) to resolve the large-scale structures, which are primarily responsible for shear layer oscillations and acoustic loads in a cavity. The unsteady, three-dimensional (3D), compressible Navier–Stokes (N–S) equations have been solved following AUSM+-up algorithm in the finite-volume formulation for subsonic and supersonic flows, where the cavity length-to-depth ratio was 3.5 and the Reynolds number based on cavity depth was 42,000. The present LES resolves the formation of shear layer, its rollup resulting in large-scale structures apart from shock–shear layer interactions, and evolution of acoustic waves. It further indicates that hydrodynamic instability, rather than the acoustic waves, is the cause of self-sustained oscillation for subsonic flow, whereas the compressive and acoustic waves dictate the cavity oscillation, and thus the sound pressure level for supersonic flow. The present LES agrees well with the experimental data and is found to be accurate enough in resolving the shear layer growth, compressive wave structures, and radiated acoustic field.

Large-eddy simulation and parameterization of buoyant plume dynamics in stratified flow

2016 ◽  
Vol 794 ◽  
pp. 798-833 ◽  
Author(s):  
Di Yang ◽  
Bicheng Chen ◽  
Scott A. Socolofsky ◽  
Marcelo Chamecki ◽  
Charles Meneveau
Keyword(s):  
Large Eddy Simulation ◽  
Large Fraction ◽  
Bubble Plume ◽  
Mean Velocity ◽  
Neutral Buoyancy ◽  
Buoyant Plumes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Consistent Manner ◽  
Trap Height

Characteristics of laboratory-scale bubble-driven buoyant plumes in a stably stratified quiescent fluid are studied using large-eddy simulation (LES). As a bubble plume entrains stratified ambient water, its net buoyancy decreases due to the increasing density difference between the entrained and ambient fluids. A large fraction of the entrained fluid eventually detrains and falls along an annular outer plume from a height of maximum rise (peel height) to a neutral buoyancy level (trap height), during which less buoyant scalars (e.g. small droplets) are trapped and dispersed horizontally, forming quasi-horizontal intrusion layers. The inner/outer double-plume structure and the peel/intrusion process are found to be more distinct for cases with small bubble rise velocity, while weak and unstable when the slip velocity is large. LES results are averaged to generate distributions of mean velocity and turbulent fluxes. These distributions provide data for assessing the performance of previously developed closures used in one-dimensional integral plume models. In particular, the various LES cases considered in this study yield consistent behaviour for the entrainment coefficients for various plume cases. Furthermore, a new continuous peeling model is derived based on the insights obtained from LES results. Comparing to previous peeling models, the new model behaves in a more self-consistent manner, and it is expected to provide more reliable performance when applied in integral plume models.

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