Large-eddy simulation of katabatic winds. Part 2: Sensitivity study and comparison with analytical models

This study examines the dynamics of turbulent flow in the wake of a turning ship using the large eddy simulation (LES) technique. LES is applied in conjunction with a random flow generation (RFG) technique originally developed at West Virginia University to provide unsteady inflow boundary conditions. As the ship is turning, the effects of the Coriolis and centrifugal forces on vortical structures are included. The effects of the Coriolis force on the flow-field are assessed and a grid sensitivity study is performed. The predicted turbulence structures are analyzed and compared with the wake of a non-turning ship.

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Large eddy simulation of ship tracks in the collapsed marine boundary layer: a case study from the Monterey area ship track experiment

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-5851-2015 ◽

2015 ◽

Vol 15 (10) ◽

pp. 5851-5871 ◽

Cited By ~ 12

Author(s):

A. H. Berner ◽

C. S. Bretherton ◽

R. Wood

Keyword(s):

Boundary Layer ◽

Large Eddy Simulation ◽

Liquid Water ◽

Satellite Images ◽

Sensitivity Study ◽

Liquid Water Path ◽

Water Path ◽

Eddy Simulation ◽

Large Eddy ◽

Ship Tracks

Abstract. For the first time, a large eddy simulation (LES) coupled to a bulk aerosol scheme is used to simulate an aircraft-sampled ship track. The track was formed by the M/V Sanko Peace on 13 June 1994 in a shallow drizzling boundary layer with high winds but very low background aerosol concentrations (10 cm−3). A Lagrangian framework is used to simulate the evolution of a short segment of track as it is advected away from the ship for 8 h (a downwind distance exceeding 570 km). Using aircraft observations for initialization, good agreement is obtained between the simulated and observed features of the ambient boundary layer outside the track, including the organization of the cloud into mesoscale rolls. After 8 h, a line of aerosol is injected to start the ship track. The simulation successfully reproduces the significant albedo enhancement and suppression of drizzle observed within the track. The aerosol concentration within the track dilutes as it broadens due to turbulent mixing. A sensitivity study shows the broadening rate strongly depends on the alignment between the track and the wind-aligned boundary layer rolls, as satellite images of ship tracks suggest. Entrainment is enhanced within the simulated track, but the observed 100 m elevation of the ship track above the surrounding layer is not simulated, possibly because the LES quickly sharpens the rather weak observed inversion. Liquid water path within the simulated track increases with time even as the ambient liquid water path is decreasing. The albedo increase in the track from liquid water and cloud fraction enhancement (second indirect effect) eventually exceeds that from cloud droplet number increases (first indirect or Twomey effect). In a sensitivity study with a higher initial ambient aerosol concentration, stronger ship track aerosol source, and much weaker drizzle, there is less liquid water inside the track than outside for several hours downwind, consistent with satellite estimates for such situations. In that case, the Twomey effect dominates throughout, although, as seen in satellite images, the albedo enhancement of the track is much smaller.

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On the Performance of Air-Lift Pumps: From Analytical Models to Large Eddy Simulation

Journal of Fluids Engineering ◽

10.1115/1.4027473 ◽

2014 ◽

Vol 136 (11) ◽

Cited By ~ 8

Author(s):

E. M. Wahba ◽

M. A. Gadalla ◽

D. Abueidda ◽

A. Dalaq ◽

H. Hafiz ◽

...

Keyword(s):

Large Eddy Simulation ◽

Flow Patterns ◽

Quantitative Agreement ◽

Analytical Models ◽

Pump Performance ◽

One Dimensional ◽

Eddy Simulation ◽

Riser Pipe ◽

Large Eddy ◽

Air Lift

The present study investigates a hierarchy of models for predicting the performance of air-lift pumps. Investigated models range from simplified one-dimensional analytical models to large eddy simulation (LES). Numerical results from LES and from two different analytical models are validated against experimental data available from the air-lift pump research program at Alexandria University. Present LES employs the volume of fluid (VOF) method to model the multiphase flow in the riser pipe. In general, LES is shown to provide fairly accurate predictions for the air-lift pump performance. Moreover, numerical flow patterns in the riser pipe are in good qualitative and quantitative agreement with their corresponding experimental patterns and with flow pattern maps available in the literature. On the other hand, analytical models are shown to provide results that are of surprisingly comparable accuracy to LES in terms of predicting the pump performance curve. However, due to the steady one-dimensional nature of these models, they are incapable of providing information about the different flow patterns developing in the riser pipe and the transient nature of the pumping process.

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Large-eddy simulation of ship tracks in the collapsed marine boundary layer: a case study from the Monterey Area Ship Track experiment

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-24387-2014 ◽

2014 ◽

Vol 14 (17) ◽

pp. 24387-24439

Author(s):

A. H. Berner ◽

C. S. Bretherton ◽

R. Wood

Keyword(s):

Boundary Layer ◽

Large Eddy Simulation ◽

Liquid Water ◽

Satellite Images ◽

Sensitivity Study ◽

Liquid Water Path ◽

Water Path ◽

Eddy Simulation ◽

Large Eddy ◽

Ship Tracks

Abstract. For the first time, a large-eddy simulation (LES) coupled to a bulk aerosol scheme is used to simulate an aircraft-sampled ship track. The track was formed by the M/V Sanko Peace on 13 June 1994 in a shallow drizzling boundary layer with high winds but very low background aerosol concentrations (10 cm−3). A Lagrangian framework is used to simulate the evolution of a short segment of track as it is advected away from the ship for eight hours (a downwind distance exceeding 570 km). Using aircraft observations for initialization, good agreement is obtained between the simulated and observed features of the ambient boundary layer outside the track, including the organization of cloud into mesoscale rolls. After eight hours, a line of aerosol is injected to start the ship track. The simulation successfully reproduces the significant albedo enhancement and suppression of drizzle observed within the track. The aerosol concentration within the track dilutes as it broadens due to turbulent mixing. A sensitivity study shows the broadening rate strongly depends on the alignment between the track and the wind-aligned boundary layer rolls, as satellite images of ship tracks suggest. Entrainment is enhanced within the simulated track, but the observed 100 m elevation of the ship track above the surrounding layer is not simulated, possibly because the LES quickly sharpens the rather weak observed inversion. Liquid water path within the simulated track increases with time even as the ambient liquid water path is decreasing. The albedo increase in the track from liquid water and cloud fraction enhancement (second indirect effect) eventually exceeds that from cloud droplet number increases (first indirect or Twomey effect). In a sensitivity study with a higher initial ambient aerosol concentration, stronger ship track aerosol source, and much weaker drizzle, there is less liquid water inside the track than outside for several hours downwind, consistent with satellite estimates for such situations. In this case, the Twomey effect dominates throughout, although, as seen in satellite images, the albedo enhancement of the track is much smaller.

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Large Eddy Simulation of a Bluff Body Stabilized Lean Premixed Flame

Journal of Combustion ◽

10.1155/2014/710254 ◽

2014 ◽

Vol 2014 ◽

pp. 1-18 ◽

Cited By ~ 7

Author(s):

A. Andreini ◽

C. Bianchini ◽

A. Innocenti

Keyword(s):

Large Eddy Simulation ◽

Gas Turbine ◽

Turbulent Combustion ◽

Bluff Body ◽

Sensitivity Study ◽

Flame Stabilization ◽

Combustion Model ◽

Eddy Simulation ◽

Large Eddy ◽

Lean Premixed

The present study is devoted to verify current capabilities of Large Eddy Simulation (LES) methodology in the modeling of lean premixed flames in the typical turbulent combustion regime of Dry LowNOxgas turbine combustors. A relatively simple reactive test case, presenting all main aspects of turbulent combustion interaction and flame stabilization of gas turbine lean premixed combustors, was chosen as an affordable test to evaluate the feasibility of the technique also in more complex test cases. A comparison between LES and RANS modeling approach is performed in order to discuss modeling requirements, possible gains, and computational overloads associated with the former. Such comparison comprehends a sensitivity study to mesh refinement and combustion model characteristic constants, computational costs, and robustness of the approach. In order to expand the overview on different methods simulations were performed with both commercial and open-source codes switching from quasi-2D to fully 3D computations.

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Large-Eddy Simulation of ECN Spray A: Sensitivity Study on Modeling Assumptions

Energies ◽

10.3390/en13133360 ◽

2020 ◽

Vol 13 (13) ◽

pp. 3360

Author(s):

Mahmoud Gadalla ◽

Jeevananthan Kannan ◽

Bulut Tekgül ◽

Shervin Karimkashi ◽

Ossi Kaario ◽

...

Keyword(s):

Large Eddy Simulation ◽

Sensitivity Study ◽

Droplet Breakup ◽

Injection Volume ◽

Eddy Simulation ◽

Large Eddy ◽

Subgrid Scales ◽

Secondary Breakup ◽

Breakup Model ◽

Model Approach

In this study, various mixing and evaporation modeling assumptions typically considered for large-eddy simulation (LES) of the well-established Engine Combustion Network (ECN) Spray A are explored. A coupling between LES and Lagrangian particle tracking (LPT) is employed to simulate liquid n-dodecane spray injection into hot inert gaseous environment, wherein Lagrangian droplets are introduced from a small cylindrical injection volume while larger length scales within the nozzle diameter are resolved. This LES/LPT approach involves various modeling assumptions concerning the unresolved near-nozzle region, droplet breakup, and LES subgrid scales (SGS) in which their impact on common spray metrics is usually left unexplored despite frequent utilization. Here, multi-parametric analysis is performed on the effects of (i) cylindrical injection volume dimensions, (ii) secondary breakup model, particularly Kelvin–Helmholtz Rayleigh–Taylor (KHRT) against a no-breakup model approach, and (iii) LES SGS models, particularly Smagorinsky and one-equation models against implicit LES. The analysis indicates the following findings: (i) global spray characteristics are sensitive to radial dimension of the cylindrical injection volume, (ii) the no-breakup model approach performs equally well, in terms of spray penetration and mixture formation, compared with KHRT, and (iii) the no-breakup model is generally insensitive to the chosen SGS model for the utilized grid resolution.

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Large Eddy Simulation of Bluff-Body Flame Approaching Blow-Off: A Sensitivity Study

Combustion Science and Technology ◽

10.1080/00102202.2018.1536125 ◽

2018 ◽

Vol 191 (10) ◽

pp. 1815-1842

Author(s):

Erdzan Hodzic ◽

Mehdi Jangi ◽

Robert-Zoltan Szasz ◽

Christophe Duwig ◽

Marco Geron ◽

...

Keyword(s):

Large Eddy Simulation ◽

Bluff Body ◽

Sensitivity Study ◽

Eddy Simulation ◽

Large Eddy

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Exploration of the impact of nearby sources on urban atmospheric inversions using large eddy simulation

Elem Sci Anth ◽

10.1525/elementa.247 ◽

2017 ◽

Vol 5 ◽

Cited By ~ 3

Author(s):

Brian J. Gaudet ◽

Thomas Lauvaux ◽

Aijun Deng ◽

Kenneth J. Davis

Keyword(s):

Large Eddy Simulation ◽

Mesoscale Model ◽

Near Field ◽

Turbulent Transport ◽

Analytical Models ◽

Source Inversion ◽

Mesoscale Models ◽

Eddy Simulation ◽

Large Eddy ◽

The Impact

The Indianapolis Flux Experiment (INFLUX) aims to quantify and improve the effectiveness of inferring greenhouse gas (GHG) source strengths from downstream concentration measurements in urban environments. Mesoscale models such as the Weather Research and Forecasting (WRF) model can provide realistic depictions of planetary boundary layer (PBL) structure and flow fields at horizontal grid lengths (Δx) down to a few km. Nevertheless, a number of potential sources of error exist in the use of mesoscale models for urban inversions, including accurate representation of the dispersion of GHGs by turbulence close to a point source. Here we evaluate the predictive skill of a 1-km chemistry-adapted WRF (WRF-Chem) simulation of daytime CO2 transport from an Indianapolis power plant for a single INFLUX case (28 September 2013). We compare the simulated plume release on domains at different resolutions, as well as on a domain run in large eddy simulation (LES) mode, enabling us to study the impact of both spatial resolution and parameterization of PBL turbulence on the transport of CO2. Sensitivity tests demonstrate that much of the difference between 1-km mesoscale and 111-m LES plumes, including substantially lower maximum concentrations in the mesoscale simulation, is due to the different horizontal resolutions. However, resolution is insufficient to account for the slower rate of ascent of the LES plume with downwind distance, which results in much higher surface concentrations for the LES plume in the near-field but a near absence of tracer aloft. Physics sensitivity experiments and theoretical analytical models demonstrate that this effect is an inherent problem with the parameterization of turbulent transport in the mesoscale PBL scheme. A simple transformation is proposed that may be applied to mesoscale model concentration footprints to correct for their near-field biases. Implications for longer-term source inversion are discussed.

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