Passive scalar flux footprint analysis over horizontally inhomogeneous plant canopy using large-eddy simulation

2008 ◽  
Vol 42 (21) ◽  
pp. 5446-5458 ◽  
Author(s):  
Shaolin Mao ◽  
Monique Y. Leclerc ◽  
Efstathios E. Michaelides
Keyword(s):  
Large Eddy Simulation ◽  
Passive Scalar ◽  
Plant Canopy ◽  
Scalar Flux ◽  
Flux Footprint ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Footprint Analysis ◽  
Horizontally Inhomogeneous

Large-eddy simulation of turbulent confined coannular jets

1996 ◽  
Vol 315 ◽  
pp. 387-411 ◽  
Author(s):  
Knut Akselvoll ◽  
Parviz Moin
Keyword(s):  
Large Eddy Simulation ◽  
Combustion Chamber ◽  
Recirculation Zone ◽  
Passive Scalar ◽  
Sudden Expansion ◽  
Subgrid Scale ◽  
Reynolds Stresses ◽  
Scalar Flux ◽  
Eddy Simulation ◽  
Large Eddy

Large-eddy simulation (LES) was used to study mixing of turbulent, coannular jets discharging into a sudden expansion. This geometry resembles that of a coaxial jet-combustor, and the goal of the calculation was to gain some insight into the phenomena leading to lean blow-out (LBO) in such combustion devices. This is a first step in a series of calculations, where the focus is on the fluid dynamical aspects of the mixing process in the combustion chamber. The effects of swirl, chemical reactions and heat release were not taken into account. Mixing of fuel and oxidizer was studied by tracking a passive scalar introduced in the central jet. The dynamic subgrid-scale (DM) model was used to model both the subgrid-scale stresses and the subgrid-scale scalar flux. The Reynolds number was 38000, based on the bulk velocity and diameter of the combustion chamber. Mean velocities and Reynolds stresses are in good agreement with experimental data. Animated results clearly show that intermittent pockets of fuel-rich fluid (from the central jet) are able to cross the annular jet, virtually undiluted, into the recirculation zone. Most of the fuel-rich fluid is, however, entrained into the recirculation zone near the instantaneous reattachment point. Fuel trapped in the recirculation zone is, for the most part, entrained back into the step shear layer close to the base of the burner.

Large eddy simulation of evolution of a passive scalar in plane jet

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 1509-1516 ◽  
Author(s):  
C. Le Ribault ◽  
S. Sarkar ◽  
S. A. Stanley
Keyword(s):  
Large Eddy Simulation ◽  
Passive Scalar ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Plane Jet

scholarly journals Direct numerical simulation and large-eddy simulation of stationary buoyancy-driven turbulence

2009 ◽  
Vol 643 ◽  
pp. 279-308 ◽  
Author(s):  
D. CHUNG ◽  
D. I. PULLIN
Keyword(s):  
Numerical Simulation ◽  
Large Eddy Simulation ◽  
Direct Numerical Simulation ◽  
Density Ratio ◽  
Stationary Flow ◽  
Small Scale ◽  
Scalar Flux ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Active Scalar

We report direct numerical simulation (DNS) and large-eddy simulation (LES) of statistically stationary buoyancy-driven turbulent mixing of an active scalar. We use an adaptation of the fringe-region technique, which continually supplies the flow with unmixed fluids at two opposite faces of a triply periodic domain in the presence of gravity, effectively maintaining an unstably stratified, but statistically stationary flow. We also develop a new method to solve the governing equations, based on the Helmholtz–Hodge decomposition, that guarantees discrete mass conservation regardless of iteration errors. Whilst some statistics were found to be sensitive to the computational box size, we show, from inner-scaled planar spectra, that the small scales exhibit similarity independent of Reynolds number, density ratio and aspect ratio. We also perform LES of the present flow using the stretched-vortex subgrid-scale (SGS) model. The utility of an SGS scalar flux closure for passive scalars is demonstrated in the present active-scalar, stably stratified flow setting. The multi-scale character of the stretched-vortex SGS model is shown to enable extension of some second-order statistics to subgrid scales. Comparisons with DNS velocity spectra and velocity-density cospectra show that both the resolved-scale and SGS-extended components of the LES spectra accurately capture important features of the DNS spectra, including small-scale anisotropy and the shape of the viscous roll-off.

scholarly journals Large-eddy-simulation closures of passive scalar turbulence: a systematic approach

2003 ◽  
Vol 496 ◽  
pp. 355-364 ◽  
Author(s):  
M. MARTINS AFONSO ◽  
A. CELANI ◽  
R. FESTA ◽  
A. MAZZINO
Keyword(s):  
Large Eddy Simulation ◽  
Systematic Approach ◽  
Passive Scalar ◽  
Eddy Simulation ◽  
Scalar Turbulence ◽  
Large Eddy

Rapid and Slow Decomposition in Large Eddy Simulation of Scalar Turbulence

2010 ◽  
Author(s):  
L. Fang ◽  
L. Shao ◽  
J. P. Bertoglio ◽  
L. P. Lu ◽  
Z. S. Zhang
Keyword(s):  
Large Eddy Simulation ◽  
A Priori ◽  
Scalar Dissipation ◽  
Scalar Flux ◽  
Mean Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Slow Part ◽  
The Mean ◽  
Subgrid Stress

In large eddy simulation of turbulent flow, because of the spatial filter, inhomogeneity and anisotropy affect the subgrid stress via the mean flow gradient. A method of evaluating the mean effects is to split the subgrid stress tensor into “rapid” and “slow” parts. This decomposition was introduced by Shao et al. (1999) and applied to A Priori tests of existing subgrid models in the case of a turbulent mixing layer. In the present work, the decomposition is extended to the case of a passive scalar in inhomogeneous turbulence. The contributions of rapid and slow subgrid scalar flux, both in the equations of scalar variance and scalar flux, are analyzed. A Priori numerical tests are performed in a turbulent Couette flow with a mean scalar gradient. Results are then used to evaluate the performances of different popular subgrid scalar models. It is shown that existing models can not well simulate the slow part and need to be improved. In order to improve the modeling, an extension of the model proposed by Cui et al. (2004) is introduced for the slow part, whereas the Scale-Similarity model is used reproduce the rapid part. Combining both models, A Priori tests lead to a better performance. However, the remaining problem is that none eddy-diffusion model can correctly represent the strong scalar dissipation near the wall. This problem will be addressed in future work.

A large eddy simulation study to assess low-speed wind and baffle orientation effects in a water treatment sedimentation basin

2018 ◽  
Vol 2017 (2) ◽  
pp. 412-421 ◽  
Author(s):  
Danial Goodarzi ◽  
Kaveh Sookhak Lari ◽  
Abolghasem Alighardashi
Keyword(s):  
Large Eddy Simulation ◽  
Wastewater Treatment Plants ◽  
Numerical Study ◽  
Three Dimensional ◽  
Passive Scalar ◽  
Hydraulic Performance ◽  
Water And Wastewater Treatment ◽  
Particle Tracing ◽  
Eddy Simulation ◽  
Large Eddy

Abstract Hydraulic performance of clarifiers in water and wastewater treatment plants significantly affects the settling efficiency of suspended particles. Structural and ambient parameters can deteriorate this performance. Through a verified three dimensional numerical study, we evaluated hydraulic performance and settling efficiency in a rectangular clarifier with a nominal hydraulic retention time (HRT) of 1 h and options for structural baffles with angles of 20°, 30°, 45° and 70°. Large eddy simulation and Lagrangian particle tracing were used to trace particles 80 to 850 μm in diameter. A passive scalar tracer study was conducted to reveal discrepancies in nominal and real HRT. By posing a 5 m/s wind, ten different scenarios were simulated. The wind caused 17% and 6% reduction in HRT and settling efficiency, respectively. Baffles improved these indicators with the 45° baffle showing the best performance with an approximate settling efficiency of 93%. The study highlighted the importance of using baffles, in particular for small size particles for which influencing factors such as wind deteriorate their settling efficiency.

scholarly journals Large eddy simulation of organized structure and momentum transfer within and above a plant canopy.

1993 ◽  
pp. 39-48 ◽  
Author(s):  
Manabu KANDA ◽  
Satoshi INAGAKI ◽  
Mikio HINO
Keyword(s):  
Large Eddy Simulation ◽  
Momentum Transfer ◽  
Plant Canopy ◽  
Eddy Simulation ◽  
Large Eddy
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