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

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
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.

Large Eddy Simulation of GDI Single-Hole Flow and Near-Field Spray

2012 ◽  
Vol 5 (2) ◽  
pp. 620-636 ◽  
Author(s):  
Bizhan Befrui ◽  
Giovanni Corbinelli ◽  
Peter Spiekermann ◽  
Mark Shost ◽  
Ming-Chia Lai
Keyword(s):  
Large Eddy Simulation ◽  
Near Field ◽  
Single Hole ◽  
Eddy Simulation ◽  
Large Eddy

Compressible large eddy simulation of the unsteady evolution process in a LPT Cascade with incoming wakes

2020 ◽  
pp. 095441002096753
Author(s):  
Yunfei Wang ◽  
Huanlong Chen ◽  
Huaping Liu ◽  
Yanping Song ◽  
Fu Chen
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Boundary Layer Separation ◽  
Main Flow ◽  
Reynolds Stresses ◽  
Flow Area ◽  
Eddy Simulation ◽  
Reduced Frequency ◽  
Large Eddy ◽  
The Impact

An in-house large eddy simulation (LES) code based on three-dimensional compressible N-S equations is used to research the impact of incoming wakes on unsteady evolution characteristic in a low-pressure turbine (LPT) cascade. The Mach number is 0.4 and Reynolds number is 0.6 × 105 (based on the axial chord and outlet velocity). The reduced frequency of incoming wakes is Fred = 0 (without wakes), 0.37 and 0.74. A detailed analysis of Reynolds stresses and turbulent kinetic energy inside the boundary layer has been carried out. Particular consideration is devoted to the transport process of incoming wakes and the intermittent property of the unsteady boundary layer. With the increase of reduced frequency, the inhibiting effect of wakes on boundary layer separation gradually enhances. The separation at the rear part of the suction side is weakened and the separation point moves downstream. However, incoming wakes lead to an increase in dissipation and aerodynamic losses in the main flow area. Excessive reduced frequency ( Fred = 0.74) causes the main flow area to become one of the main source areas of loss. An optimal reduced frequency exists to minimize the aerodynamic loss of the linear cascade.

Large eddy simulation and experimental measurements of the near-field of a large turbulent helium plume

2004 ◽  
Vol 16 (6) ◽  
pp. 1866-1883 ◽  
Author(s):  
Paul E. DesJardin ◽  
Timothy J. O’Hern ◽  
Sheldon R. Tieszen
Keyword(s):  
Large Eddy Simulation ◽  
Near Field ◽  
Experimental Measurements ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Helium Plume

scholarly journals Modelling waving crops using large-eddy simulation: comparison with experiments and a linear stability analysis

2010 ◽  
Vol 652 ◽  
pp. 5-44 ◽  
Author(s):  
S. DUPONT ◽  
F. GOSSELIN ◽  
C. PY ◽  
E. DE LANGRE ◽  
P. HEMON ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Large Eddy Simulation ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Coupled Model ◽  
Wind Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Eddy Structures ◽  
The Impact

In order to investigate the possibility of modelling plant motion at the landscape scale, an equation for crop plant motion, forced by an instantaneous velocity field, is introduced in a large-eddy simulation (LES) airflow model, previously validated over homogeneous and heterogeneous canopies. The canopy is simply represented as a poroelastic continuous medium, which is similar in its discrete form to an infinite row of identical oscillating stems. Only one linear mode of plant vibration is considered. Two-way coupling between plant motion and the wind flow is insured through the drag force term. The coupled model is validated on the basis of a comparison with measured movements of an alfalfa crop canopy. It is also compared with the outputs of a linear stability analysis. The model is shown to reproduce the well-known phenomenon of ‘honami’ which is typical of wave-like crop motions on windy days. The wavelength of the main coherent waving patches, extracted using a bi-orthogonal decomposition (BOD) of the crop velocity fields, is in agreement with that deduced from video recordings. The main spatial and temporal characteristics of these waving patches exhibit the same variation with mean wind velocity as that observed with the measurements. However they differ from the coherent eddy structures of the wind flow at canopy top, so that coherent waving patches cannot be seen as direct signatures of coherent eddy structures. Finally, it is shown that the impact of crop motion on the wind dynamics is negligible for current wind speed values. No lock-in mechanism of coherent eddy structures on plant motion is observed, in contradiction with the linear stability analysis. This discrepancy may be attributed to the presence of a nonlinear saturation mechanism in LES.

scholarly journals Entrained flow gasification. Part 3: Insight into the injector near-field by Large Eddy Simulation with detailed chemistry

Fuel ◽  
2018 ◽  
Vol 223 ◽  
pp. 164-178 ◽  
Author(s):  
Georg Eckel ◽  
Patrick Le Clercq ◽  
Trupti Kathrotia ◽  
Alexander Saenger ◽  
Sabine Fleck ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Near Field ◽  
Detailed Chemistry ◽  
Entrained Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Entrained Flow Gasification ◽  
Insight Into

scholarly journals Numerical modelling of microburst with Large-Eddy Simulation

2010 ◽  
Vol 10 (10) ◽  
pp. 24345-24370
Author(s):  
V. Anabor ◽  
U. Rizza ◽  
G. A. Degrazia ◽  
E. de Lima Nascimento
Keyword(s):  
Large Eddy Simulation ◽  
Time Scale ◽  
Doppler Radar ◽  
Leading Edge ◽  
Ring Vortex ◽  
Short Time Scale ◽  
Eddy Simulation ◽  
Cloud Models ◽  
Large Eddy ◽  
The Impact

Abstract. An isolated and stationary microburst is simulated using a 3-D time-dependent, high resolution Large-Eddy Simulation (LES) model. The microburst downdraft is initiated by specifying a simplified cooling source at the top of the domain near 2 km. The modelled time scale for this damaging wind (30 m/s) is of order of few min with a spatial scale enclosing a region with 500 m radius around the impact point. These features are comparable with results obtained from full-cloud models. The simulated flow shows the principal features observed by Doppler radar and others observational full-scale downburst events. In particular are observed the expansion of the primary and secondary cores, the presence of the ring vortex at the leading edge of the cool outflow, and finally an accelerating outburst of surface winds. This result evidences the capability of LES to reproduce complexes phenomena like a Microburst and indicates the potential of LES for utilization in atmospheric phenomena situated below the storm scale and above the microscale, which generally involves high velocities in a short time scale.

Study on micro-atmospheric environment by coupling large eddy simulation with mesoscale model

2012 ◽  
Vol 107-108 ◽  
pp. 106-117 ◽  
Author(s):  
Y.S. Liu ◽  
S.G. Miao ◽  
C.L. Zhang ◽  
G.X. Cui ◽  
Z.S. Zhang
Keyword(s):  
Large Eddy Simulation ◽  
Mesoscale Model ◽  
Atmospheric Environment ◽  
Eddy Simulation ◽  
Large Eddy
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