Parallel Dynamic Large Eddy Simulation of Turbulent Flow Around MIRA Model

2002 ◽  
Author(s):  
H. G. Choi ◽  
S. W. Kang ◽  
J. Y. Yoo
Keyword(s):  
Boundary Condition ◽  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Experimental Result ◽  
Open Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Parallel Code ◽  
Grid Points

For the large scale computation of turbulent flows around an arbitrarily shaped body, a parallel LES (large eddy simulation) code has been recently developed in which domain decomposition method is adopted. METIS and MPI (message passing interface) libraries are used for domain partitioning and data communication between processors, respectively. For unsteady computation of the incompressible Navier-Stokes equation, 4-step splitting finite element algorithm [1] is adopted and Smagorinsky or dynamic LES model can be chosen for the modeling of small eddies in turbulent flows. For the outlet (open) boundary condition, a Dirichlet boundary condition for the pressure is proposed. For the validation and performance-estimation of the parallel code, a three-dimensional laminar flow generated by natural convection inside a cube has been solved. We have confirmed that our code gives accurate results compared with previous studies. Regarding the speed-up of the code, the present parallel code with parallel block-Jacobi preconditioner is about 50 times faster than the corresponding serial code with 64 processors when approximately one million grid points are used. Most of the CPU time is consumed in solving elliptic type pressure equation. For the validation of LES models, turbulent channel flows are simulated at Re = 180, which is based on the channel half height and friction velocity using 51 × 71 × 71 grid system. It has been shown that our results agree well with the well-known results by Kim et al. [2] with less grid points than used by them in terms of time-averaged velocity field and velocity fluctuation. Lastly, we have solved the turbulent flow around MIRA (Motor Industry Research Association) model at Re = 1.6 × 106 which is based on the model height and inlet free stream velocity. Both Smagorinsky and dynamic models are tested, comparing estimated drag coefficients and pressure distribution along the model surface with the existing experimental data [3]. With the help of the parallel code developed in this study, we are able to obtain a unsteady solution of the turbulent flow field around a vehicle discretized by approximately three million grid points within two weeks when 32 IBM-SP2-processors are used. The calculated drag coefficient agrees better with the experimental result [3] than those using two equation turbulence models [4].

Development of a Spectral Element DNS/LES Method for Turbulent Flow Simulations

2007 ◽  
Author(s):  
Xu Zhang ◽  
Dan Stanescu ◽  
Jonathan W. Naughton
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Compressible Flows ◽  
Time Integration ◽  
Flow Simulation ◽  
Spectral Element ◽  
Order Of Accuracy ◽  
Eddy Simulation ◽  
Large Eddy

This paper describes a turbulent flow simulation method, which is based on combination of spectral element and large eddy simulation (LES) technique. The robust, high-order discontinuous Galerkin (DG) spectral element method for large-eddy simulation of compressible flows allows for arbitrary order of accuracy and has excellent stability properties. A local spectral discretization in terms of Legendre polynomials is used on each element of the (possibly unstructured) mesh, which allows for high-accurate simulations of turbulent flows. Discontinuities across the interfaces of the elements are resolved using a Riemann solver. An isoparametric representation of the geometry is implemented, with boundaries of the domain discretized to the same order of accuracy as the solution, and explicit low-storage Runge-Kutta methods are used for time integration. Large eddy simulation has proven to be a valuable technique for the calculation of turbulent flows. An element based filtering technique is used in conjunction with the standard Smagorinsky eddy viscosity model to estimate the effect of sub-grid scales stresses in this paper. The recently developed nonlinear model [1] will also be added in the future. The final aim of this project is to use the LES methodology in swirling jet flow simulation. As a first step towards these simulations, simulations of compressible turbulent mixing layer and back-facing step are also performed to evaluate the robust method. Initial results based on both DNS and large eddy simulations are presented in this paper. Future work will be to validate the code.

Large Eddy Simulation

1996 ◽  
Author(s):  
Joel H. Ferziger
Keyword(s):  
Numerical Simulation ◽  
Large Eddy Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Flow Simulation ◽  
Simulation Methods ◽  
Eddy Simulation ◽  
Simulation Techniques ◽  
Large Eddy

Over a decade ago, the author (Ferziger, 1983) wrote a review of the then state-of-the-art in direct numerical simulation (DNS) and large eddy simulation (LES). Shortly thereafter, a second review was written by Rogallo and Moin (1984). In those relatively early days of turbulent flow simulation, it was possible to write comprehensive reviews of what had been accomplished. Since then, the widespread availability of supercomputers has led to an explosion in this field so, although the subject is undoubtedly overdue for another review, it is not clear that the task can be accomplished in anything less than a monograph. The author therefore apologizes in advance for omissions (there must be many) and for any bias toward the accomplishments of people on the west coast of North America. In the earlier review, the author listed six approaches to the prediction of turbulent flow behavior. The list included: correlations, integral methods, single-point Reynolds-averaged closures, two-point closures, large eddy simulation and direct numerical simulation. Even then the distinction between these methods was not always clear; if anything, it is less clear today. It was possible in the earlier review to give a relatively complete overview of what had been accomplished with simulation methods. Since then, simulation techniques have been applied to an ever expanding range of flows so a thorough review of simulation results is no longer possible in the space available here. Simulation techniques have become well established as a means of studying turbulent flows and the results of simulations are best presented in combination with experimental data for the same flow. There is also a danger that the success of simulation methods will lead to attempts to apply them too soon to flows which the models and techniques are not ready to handle. To some extent, this is already happening. Direct numerical simulation (DNS) is a method in which all of the scales of motion of a turbulent flow are computed. A DNS must include everything from the large energy-containing or integral scales to the dissipative scales; the latter is usually taken to be the viscous or Kolmogoroff scales.

Constrained large-eddy simulation of turbulent flow over rough walls

2021 ◽  
Vol 6 (4) ◽  
Author(s):  
Wen Zhang ◽  
Minping Wan ◽  
Zhenhua Xia ◽  
Jianchun Wang ◽  
Xiyun Lu ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Eddy Simulation ◽  
Rough Walls ◽  
Large Eddy

Large eddy simulation study of turbulent flow around smooth and rough domes

2013 ◽  
Vol 227 (12) ◽  
pp. 2686-2700 ◽  
Author(s):  
N Kharoua ◽  
L Khezzar
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Flow Behavior ◽  
Pressure Coefficient ◽  
Horseshoe Vortex ◽  
Scale Model ◽  
Stream Velocity ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Large Eddy

Large eddy simulation of turbulent flow around smooth and rough hemispherical domes was conducted. The roughness of the rough dome was generated by a special approach using quadrilateral solid blocks placed alternately on the dome surface. It was shown that this approach is capable of generating the roughness effect with a relative success. The subgrid-scale model based on the transport of the subgrid turbulent kinetic energy was used to account for the small scales effect not resolved by large eddy simulation. The turbulent flow was simulated at a subcritical Reynolds number based on the approach free stream velocity, air properties, and dome diameter of 1.4 × 105. Profiles of mean pressure coefficient, mean velocity, and its root mean square were predicted with good accuracy. The comparison between the two domes showed different flow behavior around them. A flattened horseshoe vortex was observed to develop around the rough dome at larger distance compared with the smooth dome. The separation phenomenon occurs before the apex of the rough dome while for the smooth dome it is shifted forward. The turbulence-affected region in the wake was larger for the rough dome.

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