Comparison of Characteristics of Flow Around a Sphere With Trip Wire Using Different Turbulence Modeling Approaches

2017 ◽  
Author(s):  
Madhu Vellakal ◽  
Muris Torlak ◽  
Seid Koric ◽  
Ahmed Taha
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
High Performance ◽  
Turbulence Modeling ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Bluff Bodies ◽  
Eddy Simulation ◽  
Simulation Techniques ◽  
Turbulent Models

The flow characteristics of spherical bodies, arising in a variety of important engineering and environmental problems, range from laminar to turbulent flow. Turbulent flows are predominantly studied using the models based on Reynolds-averaged Navier-Stokes (RANS) equations. Especially, in case of flows around bluff bodies RANS models have limitations in capturing flow separation and other characteristic flow properties. Hence, the use of high-fidelity turbulent models is required to investigate the physics of these types of flow in detail. This study aims to compare and analyze the results of an incompressible turbulent flow around a sphere with additional geometric detail, like a trip wire, using different simulation techniques: Large Eddy Simulation (LES) and RANS. Modeling bodies with different characteristic geometric scales may require high-performance computing (HPC) resources due to the need to include accurate spatial and temporal resolution using unstructured mesh generation. This may be under circumstances additional criterion for decision which simulation approach is to be adopted.

BEM Based Solution of Turbulent Flow Over Periodic Hills With Heat Transfer

2011 ◽  
Author(s):  
Leopold Sˇkerget ◽  
Jure Ravnik
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Small Scale ◽  
Test Case ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Turbulent Models

Detached turbulent flows are difficult to predict numerically and often serve as benchmark cases for developing new numerical schemes and new turbulent models. Turbulent flow over periodic hills is one such examples, since the flow exhibits separation and reattachment on a smoothly and/or sharp curved geometry, strong pressure gradients and fluctuation of the separation point in time. These cases have been chosen by many authors for testing different turbulence simulation approaches. When the bottom wall is heated, the complexity of the problem increased, since convective heat transfer is defined by small scale turbulent structures close to the wall. We developed a Reynolds-Averaged Navier-Stokes and Large Eddy Simulation solver based on the velocity-vorticity formulation of Navier Stokes equations. RANS equations are coupled by a low-Reynolds number turbulent model, while Smagorinsky subgrid model is used for LES. The governing equations are solved with a numerical solution algorithm, which is based on the boundary element method. The pressure field is computed in a post processing step by solving a Poisson equation. The single domain as well as domain decomposition approaches are applied. The developed method was validated using flow over periodic hills test case.

Lattice Boltzmann Method Based on Large-Eddy Simulation (LES) Used to Investigate the Unsteady Turbulent Flow on Series of Cavities

2020 ◽  
Author(s):  
Insaf Mehrez ◽  
Ramla Gheith ◽  
Fethi Aloui
Keyword(s):  
Boltzmann Equation ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Turbulence Modeling ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy

Abstract A numerical study is proposed to analyze the turbulent flow structures. This paper aims to determine the effect of the series of the cavities. The configuration is similar to that represented by two walls with infinite width, one of which is mobile and the other is fixed. The series of cavity are placed on the fixed wall. The objectives are to study the aero acoustic capabilities of LBM and to build and to assess the efficiency of the Lattice Boltzmann Equation (LBE) as a new computational tool to perform the Large-Eddy Simulations (LES) for turbulent flows. In the first part, the background of LBM is presented and the construction of Navier-Stokes equations from Boltzmann equation is discussed. The LBM-LES model for solving transition is developed and turbulence modeling is implemented. In the second part, the dynamics of the flows in the vicinity of cavities with symmetric or asymmetric edges are considered, to then discuss the oscillation phenomenon. The effect of the geometric of the cavity and the Reynolds numbers were studied to investigate the fluid flow dynamics. We were focusing on the dynamics of asymmetric deep cavity flows, to put forward the topology of the cavity flow and to highlight the effects of dissymmetry and aspect ratio.

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.

scholarly journals Numerical Study of the Turbulent Flow from a Steam Dumping Pressurizer Relief Tank

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4059
Author(s):  
Sen Zhang ◽  
Xiao-Wei Guo ◽  
Chao Li ◽  
Yi Liu ◽  
Ran Zhao ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Open Source ◽  
Complex Geometry ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Source Codes ◽  
Model Based ◽  
Eddy Simulation

Due to the complex geometry and turbulent flow characteristics, it is hard to simulate the process of steam dumping of the pressurizer relief tank (PRT). In this study, we develop a compressible fluid solver PRTFOAM to numerically study the turbulent flow dynamics from a PRT. The PRTFOAM is implemented based on the OpenFOAM and designed to be capable of integrating various turbulence models. Two representative Reynolds-averaged Navier–Stokes (RANS) models and a Smagorinsky–Lilly SGS model based on Large Eddy Simulation (LES) are coupled and tested with PRTFOAM. The case of a flow past a circular cylinder (Re = 3900) is tested and analyzed comprehensively as a benchmark case. Then, the turbulent steam dumping process in the full geometry of a PRT is analyzed and compared with ANSYS CFX and literature reports. In addition, we tested the WALE model based on the PRT steam dumping process. The results show that SST k-ω model and Smagorinsky–Lilly SGS model-based LES approach are more appropriate than the LRR model for PRT simulations. Moreover, it shows that the simulation results of Smagorinsky–Lilly SGS model and WALE model are basically consistent under the condition of PRT steam dumping process. Under this condition, the drawbacks of Smagorinsky–Lilly SGS model are not obvious. Furthermore, the comparison with CFX showed that our open source solver could be used to obtain better results in complex engineering cases. The design and testing results would provide guidance for further analysis of thermal-hydraulics in reactors based on open source codes.

Simulation and Modeling of Turbulent Flows

1996 ◽  
Keyword(s):  
Numerical Simulation ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Simulation And Modeling ◽  
Simulation Techniques ◽  
Rational Development ◽  
Group Methods ◽  
Turbulent Closure ◽  
The Subject ◽  
Renormalization Group Methods

This book provides students and researchers in fluid engineering with an up-to-date overview of turbulent flow research in the areas of simulation and modeling. A key element of the book is the systematic, rational development of turbulence closure models and related aspects of modern turbulent flow theory and prediction. Starting with a review of the spectral dynamics of homogenous and inhomogeneous turbulent flows, succeeding chapters deal with numerical simulation techniques, renormalization group methods and turbulent closure modeling. Each chapter is authored by recognized leaders in their respective fields, and each provides a thorough and cohesive treatment of the subject.

Simulating flow separation from continuous surfaces: routes to overcoming the Reynolds number barrier

2009 ◽  
Vol 367 (1899) ◽  
pp. 2885-2903 ◽  
Author(s):  
Michael Leschziner ◽  
Ning Li ◽  
Fabrizio Tessicini
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Major Elements ◽  
Wall Layer ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Models ◽  
High Reynolds ◽  
Near Wall

This paper provides a discussion of several aspects of the construction of approaches that combine statistical (Reynolds-averaged Navier–Stokes, RANS) models with large eddy simulation (LES), with the objective of making LES an economically viable method for predicting complex, high Reynolds number turbulent flows. The first part provides a review of alternative approaches, highlighting their rationale and major elements. Next, two particular methods are introduced in greater detail: one based on coupling near-wall RANS models to the outer LES domain on a single contiguous mesh, and the other involving the application of the RANS and LES procedures on separate zones, the former confined to a thin near-wall layer. Examples for their performance are included for channel flow and, in the case of the zonal strategy, for three separated flows. Finally, a discussion of prospects is given, as viewed from the writer's perspective.

On Direct Numerical Simulation of Turbulent Flows

2011 ◽  
Vol 64 (2) ◽  
Author(s):  
Giancarlo Alfonsi
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
High Performance Computing ◽  
Turbulent Flows ◽  
High Performance ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Turbulent Shear ◽  
Navier Stokes Equations ◽  
Performance Computing

The direct numerical simulation of turbulence (DNS) has become a method of outmost importance for the investigation of turbulence physics, and its relevance is constantly growing due to the increasing popularity of high-performance-computing techniques. In the present work, the DNS approach is discussed mainly with regard to turbulent shear flows of incompressible fluids with constant properties. A body of literature is reviewed, dealing with the numerical integration of the Navier-Stokes equations, results obtained from the simulations, and appropriate use of the numerical databases for a better understanding of turbulence physics. Overall, it appears that high-performance computing is the only way to advance in turbulence research through the front of the direct numerical simulation.

Parameter Extension Simulation of Turbulent Flows in a Compressor Cascade With a High Reynolds Number

2020 ◽  
Author(s):  
Yan Jin
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Stokes Equations ◽  
Simulation Method ◽  
Potential Method ◽  
Navier Stokes ◽  
Reference Solution ◽  
Compressor Cascade ◽  
High Reynolds

Abstract The turbulent flow in a compressor cascade is calculated by using a new simulation method, i.e., parameter extension simulation (PES). It is defined as the calculation of a turbulent flow with the help of a reference solution. A special large-eddy simulation (LES) method is developed to calculate the reference solution for PES. Then, the reference solution is extended to approximate the exact solution for the Navier-Stokes equations. The Richardson extrapolation is used to estimate the model error. The compressor cascade is made of NACA0065-009 airfoils. The Reynolds number 3.82 × 105 and the attack angles −2° to 7° are accounted for in the study. The effects of the end-walls, attack angle, and tripping bands on the flow are analyzed. The PES results are compared with the experimental data as well as the LES results using the Smagorinsky, k-equation and WALE subgrid models. The numerical results show that the PES requires a lower mesh resolution than the other LES methods. The details of the flow field including the laminar-turbulence transition can be directly captured from the PES results without introducing any additional model. These characteristics make the PES a potential method for simulating flows in turbomachinery with high Reynolds numbers.

scholarly journals 3D Numerical Study of the Flow Properties in a Double-Spur Dikes Field during a Flood Process

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1574 ◽  
Author(s):  
Xun Han ◽  
Pengzhi Lin
Keyword(s):  
Water Surface ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
River Bed ◽  
Hydrodynamic Evolution ◽  
Spur Dikes ◽  
Potential Damage

A 3D numerical model is developed to study the flow characteristics of a double-spur dikes field on Yangtze River during a flood process, which was presented by the variation of the flow condition. The model is based on Navier–Stokes (NS) equations, the porous medium method (PMM) is employed to treat the solid structures including the river bed surface, the volume of fluid (VOF) method is applied to track the motion of the water surface during the flood process, and large eddy simulation (LES) is adopted to capture the turbulence transport and dissipation. Using this model, the target reach’s flow field before the construction of double-spur dikes is simulated first, while the numerical results are compared to the field measurements on flow velocity and water surface level, and fairly good agreements are shown. Then, the model is applied to reproduce the hydrodynamic evolution during a flood process after double-spur dikes’ constructions, while the detailed 3D flow fields are obtained under some certain states with different submergence rates of the spur dikes; finally, the potential damage positions around these spur dikes are analyzed accordingly.

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