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

2012 ◽  
Vol 134 (4) ◽  
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.

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

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.

Partially Averaged Navier-Stokes Turbulence Modeling of Flow in 5x5 PWR Fuel Assembly With Spacer Grid

2018 ◽  
Author(s):  
Giacomo Busco ◽  
Yassin A. Hassan
Keyword(s):  
Large Eddy Simulation ◽  
Numerical Simulations ◽  
Stokes Equations ◽  
Direct Numerical Simulations ◽  
Navier Stokes ◽  
Spacer Grid ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

The highly turbulent flow inside a pressurized water reactor makes unpractical the use of scale resolving simulations, due to the large number of space and time turbulent structures. The high computational cost associated with typical large eddies simulations or direct numerical simulations techniques is unsuitable due to the large spatiotemporal resolution required. Partially averaged Navier-Stokes turbulence model is presented as bridging model between Reynolds averaged Navier-Stokes equations and direct numerical simulations. As filtered representation of the Navier-Stokes equations, the model is able to continuously shift its energy-based filter, inside the turbulence spectrum, being able to resolve the turbulent scales of interest. The choice of energy based cut-off filters gives the chance to directly impose the degree of needed resolution, where the most important large scales unsteadiness are resolved at minimal computational expenses. The partially averaged Navier-Stokes modelling approach has been tested for a Reynolds number of 14,000, inside a 5 × 5 fuel bundle, with a single spacer grid and split-type mixing vanes. Four different filters have been tested, whose resolution ranged from Reynolds averaged Navier-Stokes and large eddy simulation. A comparison with large eddy simulation will be presented. The results show that the partially averaged Navier-Stokes modeling produces results comparable to those of large eddy simulation when the appropriate cut-off energy filter is chosen. The turbulence models results will be compared with the available particle image velocimetry experimental data.

Immersed Boundary Method for Large Eddy Simulation and Lagrangian Stochastic Modeling of Passive Scalar Dispersion Downstream of an Obstacle

2010 ◽  
Author(s):  
C. Le Ribault ◽  
S. Simoe¨ns
Keyword(s):  
Large Eddy Simulation ◽  
Immersed Boundary Method ◽  
Passive Scalar ◽  
Immersed Boundary ◽  
Two Dimensional ◽  
Scalar Dispersion ◽  
Eddy Simulation ◽  
Boundary Method ◽  
Passive Scalar Transport ◽  
Large Eddy

A large-eddy simulation (LES) using the atmospheric code ARPS is performed to study the passive scalar dispersion downstream of an obstacle. An immersed boundary method has been introduced to take into account the obstacle. To simulate the scalar dispersion, instead of resolving the passive scalar transport equation, fluid particles containing scalar are tracked in a Lagrangian way. The results of the LES are compared with the experiments of Vinc¸ont et al. [1]. In those experiments, simultaneous measurements of the velocity and scalar concentration fields have been made in the plume emitting from a two-dimensional line source flushed with the wall. The source is one obstacle height downstream of a two-dimensional square obstacle located on the wall of a turbulent boundary layer. Our simulations predict the qualitative and quantitative features of the experimental results.

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

LARGE EDDY SIMULATION OF HYDROELASTIC VIBRATION USING THE FINITE ELEMENT METHOD

2010 ◽  
Vol 24 (24) ◽  
pp. 4683-4706 ◽  
Author(s):  
W. Q. WANG ◽  
L. X. ZHANG ◽  
X. Q. HE ◽  
Y. GUO
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Large Eddy Simulation ◽  
Guide Vane ◽  
The Finite Element Method ◽  
Hydro Turbine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Hydroelasticity Problem ◽  
Element Method

This work is concerned with modeling the interaction of fluid flow with flexible solid structures. An improving spring smooth analogy and an improved constant volume transfer (ICVT) are used to provide fluid mesh control and transfer the information on the interfaces between fluid and structure, respectively. The time integrating algorithm is based on the predictor multi-corrector algorithm (PMA). An important aspect of this work is that we present a directly coupled approach, in which a large eddy simulation (LES) fluid solver and a structure solver have been coupled together to solve a hydroelasticity problem using the finite element method. To demonstrate the performance of the proposed approach, two working examples were used. One is the vibration of a beam immersed in incompressible fluid, another is the hydroelastic behavior of an ideal guide vane in a hydro turbine passage. The numerical results show the validity of the proposed approach.

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