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.

scholarly journals Comparative Studies of RANS Versus Large Eddy Simulation for Fan–Intake Interaction

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Yunfei Ma ◽  
Nagabhushana Rao Vadlamani ◽  
Jiahuan Cui ◽  
Paul Tucker
Keyword(s):  
Large Eddy Simulation ◽  
Turbulence Model ◽  
Immersed Boundary Method ◽  
Immersed Boundary ◽  
Flow Acceleration ◽  
Eddy Simulation ◽  
Boundary Method ◽  
Fan Effect ◽  
Wide Range ◽  
Large Eddy

The present research applied a mixed-fidelity approach to examine the fan–intake interaction. Flow separation induced by a distortion generator (DG) is either resolved using large eddy simulation (LES) or modeled using the standard k–ω model, Spalart–Allmaras (SA) model, etc. The immersed boundary method with smeared geometry (immersed boundary method with smeared geometry (IBMSG)) is employed to represent the effect of the fan and a wide range of test cases is studied by varying the (a) height of the DG and (b) proximity of the fan to the DG. Comparisons are drawn between the LES and the Reynolds-averaged Navier–Stokes (RANS) approaches with/without the fan effect. It is found that in the “absence of fan,” the discrepancies between RANS and LES are significant within the separation and reattachment region due to the well-known limitations of the standard RANS models. “With the fan installed,” the deviation between RANS and LES decreases substantially. It becomes minimal when the fan is closest to the DG. It implies that with an installed fan, the inaccuracies of the turbulence model are mitigated by the strong flow acceleration at the casing due to the fan. More precisely, the mass flow redistribution due to the fan has a dominant primary effect on the final predictions and the effect of turbulence model becomes secondary, thereby suggesting that high fidelity eddy resolving simulations provide marginal improvements to the accuracy for the installed cases, particularly for the short intake–fan strategies with fan getting closer to intake lip.

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