Simulation of the Scalar Transport above and within the Amazon Forest Canopy

The parallelized large-eddy simulation model (PALM) was used to understand better the turbulent exchanges of a passive scalar above and within a forested region located in the central Amazon. Weak (2 ms−1) and strong (6 ms−1) wind conditions were simulated. A passive scalar source was introduced to the forest floor for both simulations. The simulations reproduced the main characteristics of the turbulent flow and of the passive scalar transport between the forest and the atmosphere. Noteworthily, strong and weak wind conditions presented different turbulence structures that drove different patterns of scalar exchange both within and above the forest. These results show how passive scalar concentration is influenced by the wind speed at the canopy top. Additionally, higher wind speeds are related to stronger sweep and ejection regimes, generating more intense plumes that are able to reduce the passive scalar concentration inside the forest canopy. This work was the first that used PALM to investigate scalar transport between the Amazon rainforest and the atmosphere.

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Numerical Investigations of Passive Scalar Transport in Turbulent Taylor-Couette Flows: Code Validation

ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting: Volume 1, Symposia – Parts A, B, and C ◽

10.1115/fedsm-icnmm2010-31296 ◽

2010 ◽

Author(s):

Yacine Salhi ◽

El-Khider Si-Ahmed ◽

Ge´rard Degrez ◽

Jack Legrand ◽

Fethi Aloui

Keyword(s):

Finite Element ◽

Stokes Equations ◽

Passive Scalar ◽

Scalar Transport ◽

Diffusion Reaction ◽

Navier Stokes ◽

Eddy Simulation ◽

Passive Scalar Transport ◽

Taylor Couette ◽

Spectral Finite Element

The highly turbulent flow occurring inside (electro)chemical reactors requires accurate simulation of scalar mixing if CFD methods are to be used with confidence in design. This has motivated the present paper, which describes the implementation of a passive scalar transport equation into a hybrid spectral/finite-element code. For this purpose, direct numerical simulations (DNS) and Large Eddy Simulation (LES) have been performed to study the effects of the gravitational and the centrifugal potentials on the stability of incompressible Taylor-Couette flow. The flow is confined between two concentric cylinders and only the inner cylinder is allowed to rotate while the outer one is at rest. The Navier-Stokes equations and the uncoupled convection–diffusion–reaction (CDR) equation are solved using a code named SFELES which consists on spectral development in one direction combined with a finite element discretisation in the two remaining directions. The performance of the LES code is validated against published DNS data for a channel flow for the velocity and scalar statistics with good agreement between the current LES predictions and DNS data.

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Numerical Investigations of Passive Scalar Transport in Turbulent Taylor-Couette Flows: Large Eddy Simulation Versus Direct Numerical Simulations

Journal of Fluids Engineering ◽

10.1115/1.4006467 ◽

2012 ◽

Vol 134 (4) ◽

Cited By ~ 2

Author(s):

Yacine Salhi ◽

El-Khider Si-Ahmed ◽

Gérard Degrez ◽

Jack Legrand

Keyword(s):

Finite Element ◽

Large Eddy Simulation ◽

Numerical Simulations ◽

Passive Scalar ◽

Direct Numerical Simulations ◽

Scalar Transport ◽

Eddy Simulation ◽

Passive Scalar Transport ◽

Large Eddy ◽

Spectral Finite Element

The highly turbulent flow occurring inside (electro)chemical reactors requires accurate simulation of scalar mixing if computational fluid dynamics (CFD) methods are to be used with confidence in design. This has motivated the present paper, which describes the implementation of a passive scalar transport equation into a hybrid spectral/finite-element code. Direct numerical simulations (DNS) and large eddy simulation (LES) were performed to study the effects of gravitational and centrifugal potentials on the stability of incom-pressible Taylor-Couette flow. The flow is confined between two concentric cylinders with an inner rotating cylinder while the outer one is at rest. The Navier-Stokes equations with the uncoupled convection–diffusion–reaction (CDR) equation are solved using a code named spectral/finite element large eddy simulations (SFELES) which is based on spectral development in one direction combined with a finite element discretization in the remaining directions. The performance of the LES code is validated with published DNS data for channel flow. Velocity and scalar statistics showed good agreement between the current LES predictions and DNS data. Special attention was given to the flow field, in the vicinity of Reynolds number of 68.2 with radii ratio of 0.5. The effect of Sc on the concentration peak is pointed out while the magnitude of heat transfer shows a dependence of the Prandtl number with an exponent of 0.375.

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