LATTICE-BOLTZMANN SIMULATIONS OF FLOWS OVER BACKWARD-FACING INCLINED STEPS

2013 ◽  
Vol 25 (01) ◽  
pp. 1340021 ◽  
Author(s):  
RUPESH B. KOTAPATI ◽  
RICHARD SHOCK ◽  
HUDONG CHEN
Keyword(s):  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Turbulence Modeling ◽  
Laser Doppler Anemometry ◽  
Expansion Ratio ◽  
Outlet Section ◽  
Inlet Section ◽  
Eddy Simulation ◽  
Lattice Boltzmann Simulations ◽  
Inclination Angles

The lattice-Boltzmann method (LBM) is used in conjunction with a very large-eddy simulation (VLES) turbulence modeling approach to compute separated flows over backward-facing steps at different wall inclination angles. The Reynolds number Re H based on the step height H and center-line velocity at the channel inlet ucl is 64 000. The expansion ratio of the outlet section to the inlet section of the channel is 1.48. Wall inclination angles α considered include 10°, 15°, 20°, 25°, 30° and 90°. The computed flow fields for different inclination angles of the step are assessed against the laser Doppler anemometry (LDA) measurements of Makiola [B. Makiola, Ph.D. Thesis, University of Karlsruhe (1992); B. Ruck and B. Makiola, Flow separation over the step with inclined walls, in Near-Wall Turbulent Flows, eds. R. M. C. So, C. G. Speziale and B. E. Launder (Elsevier, 1993), p. 999.]. In addition to validating the lattice-Boltzmann solution with the experiments, this study also investigates the effects of three dimensionality, the proximity of the inlet to the step, and the grid resolution on the quality of the predictions.

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.

Lattice Boltzmann for Turbulence Modeling

2018 ◽  
Author(s):  
Sauro Succi
Keyword(s):  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Turbulence Modeling ◽  
Real Life ◽  
Practical Interest ◽  
Reynolds Numbers ◽  
Full Resolution ◽  
To Come ◽  
Highly Turbulent Flows ◽  
Main Ideas

This chapter introduces the main ideas behind the application of LBE methods to the problem of turbulence modeling, namely the simulation of flows which contain scales of motion too small to be resolved on present-day and foreseeable future computers. Many real-life flows of practical interest exhibit Reynolds numbers far too high to be directly simulated in full resolution on present-day computers and arguably for many years to come. This raises the challenge of predicting the behavior of highly turbulent flows without directly simulating all scales of motion which take part to turbulence dynamics, but only those that fall within the computer resolution at hand.

scholarly journals Wall-modeled large-eddy simulation of the flow past a rod-airfoil tandem by the Lattice Boltzmann method

2018 ◽  
Vol 28 (5) ◽  
pp. 1096-1116 ◽  
Author(s):  
Emmanuel Leveque ◽  
Hatem Touil ◽  
Satish Malik ◽  
Denis Ricot ◽  
Alois Sengissen
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Early Stage ◽  
Content Type ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbulent Airflow ◽  
High Reynolds ◽  
Boltzmann Method

Purpose The Lattice Boltzmann (LB) method offers an alternative to conventional computational fluid dynamics (CFD) methods. However, its practical use for complex turbulent flows of engineering interest is still at an early stage. This paper aims to outline an LB wall-modeled large-eddy simulation (WMLES) solver. Design/methodology/approach The solver is dedicated to complex high-Reynolds flows in the context of WMLES. It relies on an improved LB scheme and can handle complex geometries on multi-resolution block structured grids. Findings Dynamic and acoustic characteristics of a turbulent airflow past a rod-airfoil tandem are examined to test the capabilities of this solver. Detailed direct comparisons are made with both experimental and numerical reference data. Originality/value This study allows assessing the potential of an LB approach for industrial CFD applications.

Lattice Boltzmann for Turbulent Flows

2018 ◽  
Author(s):  
Sauro Succi
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Turbulence Modeling ◽  
Grid Resolution ◽  
Subsequent Chapter ◽  
Main Ideas

This chapter presents the main ideas behind the application of LB methods to the simulation of turbulent flows. The attention is restricted to the case of direct numerical simulation, in which all scales of motion within the grid resolution are retained in the simulation. Turbulence modeling, in which the effect of unresolved scales on the resolved ones is taken into account by various forms of modeling, will be treated in a subsequent chapter.

Large Eddy Simulation Turbulence Model Applied to the Lattice Boltzmann Method

2018 ◽  
pp. 337-360
Author(s):  
Iñaki Zabala ◽  
Jesús M. Blanco
Keyword(s):  
Large Eddy Simulation ◽  
Lattice Boltzmann Method ◽  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Convection Diffusion ◽  
Eddy Simulation ◽  
Novel Approach ◽  
Large Eddy ◽  
Mesh Density ◽  
Boltzmann Method

The lattice Boltzmann method (LBM) is a novel approach for simulating convection-diffusion problems. It can be easily parallelized and hence can be used to simulate fluid flow in multi-core computers using parallel computing. LES (large eddy simulation) is widely used in simulating turbulent flows because of its lower computational needs compared to others such as direct numerical simulation (DNS), where the Kolmogorov scales need to be solved. The aim of this chapter consists of introducing the reader to the treatment of turbulence in fluid dynamics through an LES approach applied to LBM. This allows increasing the robustness of LBM with lower computational costs without increasing the mesh density in a prohibitive way. It is applied to a standard D2Q9 structure using a unified formulation.

Incorporating Turbulence Models into the Lattice-Boltzmann Method

1998 ◽  
Vol 09 (08) ◽  
pp. 1159-1175 ◽  
Author(s):  
Christopher M. Teixeira
Keyword(s):  
Lattice Boltzmann Method ◽  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Turbulence Models ◽  
Algebraic Model ◽  
Expansion Ratio ◽  
Equation Model ◽  
Recirculation Length ◽  
Boltzmann Method ◽  
Good Agreement

The Lattice-Boltzmann method (LBM) is extended to allow incorporation of traditional turbulence models. Implementation of a two-layer mixing-length algebraic model and two versions of the k-ε two-equation model, Standard and RNG, in conjunction with a wall model, are presented. Validation studies are done for turbulent flows in a straight pipe at three Re numbers and over a backwards facing step of expansion ratio 1.5 and Re H=44 000. All models produce good agreement with experiment for the straight pipes but the RNG k-ε model is best able to capture both the recirculation length, within 2% of experiment, and the detailed structure of the mean fluid flow for the backwards facing step.

Roughness-induced flow instability: a lattice Boltzmann study

2007 ◽  
Vol 573 ◽  
pp. 191-209 ◽  
Author(s):  
FATHOLLAH VARNIK ◽  
DOROTHÉE DORNER ◽  
DIERK RAABE
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Flow Instability ◽  
Wall Roughness ◽  
Navier Stokes Equation ◽  
Viscous Shear Stress ◽  
Lattice Boltzmann Simulations ◽  
Micro Channels ◽  
Viscous Shear

Effects of wall roughness/topography on flows in strongly confined (micro-)channels are studied by means of lattice Boltzmann simulations. Whereas wall roughness in macroscopic channels is considered to be relevant only for high-Reynolds-number turbulent flows (where the flow is turbulent even for smooth walls), it is shown in this paper that, in micro-channels, surface roughness may even modify qualitative features of the flow. In particular, a transition from laminar to unsteady flow is observed. It is found that this roughness-induced transition is strongly enhanced as the channel width is decreased. The reliability of our results is checked by computing the viscous shear stress and the Reynolds stress across the channel, their sum following the theoretical prediction for the stress balance perfectly. Furthermore, the solutions obtained obey the transformation rules of the Navier–Stokes equation: When expressed in reduced (dimensionless) units, results for various channel dimensions, forcing term or dynamic viscosity are identical provided that the channel shape and the Reynolds number are unchanged. The time evolution of the velocity fluctuations at the initial stages of the transition to flow instability is monitored. It is found that fluctuations first occur in the vicinity of the rough wall, supporting the interpretation of wall roughness as a source of fluctuations and thus flow instability. In addition to their physical significance, our results provide further evidence for the reliability of the lattice Boltzmann method in dealing with complex unsteady flows.

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