Numerical Investigation of Flow Over an Airfoil by the Lattice Boltzmann Method

Author(s):  
Felipe A. Valenzuela ◽  
Amador M. Guzmán ◽  
Andrés J. Díaz

During the last years the aerodynamics characteristics of airfoils have been studied solving numerically the Navier-Stokes (NS) equations. These calculations require a significant computational cost due to both the second order and the nonlinear characteristics of the NS partial differential equations. Therefore, efforts have been devoted to reduce this cost and increase the accuracy of the numerical methods. The Lattice-Boltzmann Method (LBM) has become a great alternative to simulate this problem and a variety of fluid flows. In this method, the convective operator is linear and the pressure is calculated directly by the equation of state without implementing iterative methods. This work represents a preliminary investigation of a laminar flow over airfoils under low Reynolds number conditions (Re = 500). Solutions are obtained using a Multi-Block mesh refinement method. In order to validate the computational code, calculations are performed on a SD7003 airfoil at an angle of attack of 4° and 30°, which corresponds to the available numerical and experimental results. The results of this study agree well with previous experimental and numerical studies demonstrating the capabilities of the LBM to simulate accurately laminar flows over airfoils as well as capturing and predicting the laminar separation bubbles.

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Antoine Maros ◽  
Benoît Bonnal ◽  
Ignacio Gonzalez-Martino ◽  
James Kopriva ◽  
Francesco Polidoro

Abstract Compressor corner stall is a phenomenon difficult to predict with numerical tools but essential to the design of axial compressors. Predictive methods are beneficial early in the design process to understand design and off-design limitations. Prior numerical work using Navier–Stokes computational methods has assessed the prediction capability for corner stall. Reynolds-averaged Navier–Stokes (RANS) simulations using several turbulence models have shown to over-predict the region of corner hub stall where large eddy simulations (LES) and detached eddy simulations (DES) approaches improved the airfoil surface and wake pressure loss prediction. A linear compressor cascade designed and tested at Ecole Centrale de Lyon provides a good benchmark for the evaluation of the accuracy of numerical methods for corner stall. This paper presents results obtained with Lattice-Boltzmann method (LBM) coupled with very large-eddy simulations (VLES) approach of PowerFLOW and compares them with the experimental and numerical work from Ecole Centrale de Lyon. The ability to achieve equivalent accuracy at a lower computational cost compared to LES scale resolving methods can enable multi-stage design and off-design compressor predictions. A methodical approach is taken by first accurately simulating the upstream flow conditions. Geometric trips are modeled upstream on the endwalls to match both the mean and fluctuating inflow boundary layer conditions. These conditions were then applied to the simulation of the linear compressor cascade. The benchline experimental study includes trips on both the pressure and suction of the airfoil. These trips are also included for the current simulation. The significance of capturing both inflow conditions and including trips on the airfoil is assessed. Detailed comparisons are then made to airfoil loading and downstream losses between experiment and previous RANS and LES simulations. LBM-VLES corner stall results of pitchwise averaged total pressure match LES agreement relative to experimental data at 50 times lower computational cost.


Author(s):  
Antoine Maros ◽  
Benoît Bonnal ◽  
Ignacio Gonzalez-Martino ◽  
James Kopriva ◽  
Francesco Polidoro

Abstract Compressor corner stall is a phenomenon difficult to predict with numerical tools but essential to the design of axial compressors. Predictive methods are beneficial early in the design process to understand design and off-design limitations. Prior numerical work using Navier-Stokes computational methods have assessed the prediction capability for corner stall. Reynolds Averaged Navier-Stokes (RANS) simulations using several turbulence models [1] have shown to over-predict the region of corner hub stall where Large Eddy Simulations (LES) and Detached Eddy Simulations (DES) approaches improved the airfoil surface and wake pressure loss prediction [2, 3]. A linear compressor cascade designed and tested at Ecole Centrale de Lyon [3,4] provides a good benchmark for the evaluation of the accuracy of numerical methods for corner stall. This paper presents results obtained with Lattice-Boltzmann Method (LBM) coupled with Very Large-Eddy Simulations (VLES) approach of PowerFLOW and compares them with the experimental and numerical work from Ecole Centrale de Lyon. The ability to achieve equivalent accuracy at a lower computational cost compared to LES scale resolving methods can enable multi-stage design and off-design compressor predictions. A methodical approach is taken by first accurately simulating the upstream flow conditions. Geometric trips are modeled upstream on the endwalls to match both the mean and fluctuating inflow boundary layer conditions. These conditions were then applied to the simulation of the linear compressor cascade. The benchline experimental study includes trips on both the pressure and suction of the airfoil. These trips are also included for the current simulation. The significance of capturing both inflow conditions and including trips on the airfoil are assessed. Detailed comparisons are then made to airfoil loading and downstream losses between experiment and previous RANS and LES simulations. LBM-VLES corner stall results of pitchwise averaged total pressure match LES agreement relative to experimental data at 50 times lower computational cost.


2021 ◽  
Vol 263 (6) ◽  
pp. 598-609
Author(s):  
Kazuya Kusano ◽  
Masato Furukawa ◽  
Kenichi Sakoda ◽  
Tomoya Fukui

The present study developed an unsteady RANS approach based on the lattice Boltzmann method (LBM), which can perform direct aeroacoustic simulations of low-speed fans at lower computational cost compared with the conventional LBM-LES approach. In this method, the k-ω turbulence model is incorporated into the LBM flow solver, where the transport equations of k and ω are also computed by the lattice Boltzmann method, similar to the Navier-Stokes equations. In addition, moving boundaries such as fan rotors are considered by a direct-forcing immersed boundary method. This numerical method was validated in a two-dimensional simulation of a cross-flow fan. As a result, the simulation was able to capture an eccentric vortex structure in the rotor, and the pressure rise by the work of the rotor can be reproduced. Also, the peak sound of the blade passing frequency can be successfully predicted by the present method. Furthermore, the simulation results showed that the peak sound is generated by the interaction between the rotor blade and the flow around the tongue part of the casing.


Author(s):  
Joris C. G. Verschaeve

By means of the continuity equation of the incompressible Navier–Stokes equations, additional physical arguments for the derivation of a formulation of the no-slip boundary condition for the lattice Boltzmann method for straight walls at rest are obtained. This leads to a boundary condition that is second-order accurate with respect to the grid spacing and conserves mass. In addition, the boundary condition is stable for relaxation frequencies close to two.


2014 ◽  
Vol 554 ◽  
pp. 665-669
Author(s):  
Leila Jahanshaloo ◽  
Nor Azwadi Che Sidik

The Lattice Boltzmann Method (LBM) is a potent numerical technique based on kinetic theory, which has been effectively employed in various complicated physical, chemical and fluid mechanics problems. In this paper multi-relaxation lattice Boltzmann model (MRT) coupled with a Large Eddy Simulation (LES) and the equation are applied for driven cavity flow at different Reynolds number (1000-10000) and the results are compared with the previous published papers which solve the Navier stokes equation directly. The comparisons between the simulated results show that the lattice Boltzmann method has the capacity to solve the complex flows with reasonable accuracy and reliability. Keywords: Two-dimensional flows, Lattice Boltzmann method, Turbulent flow, MRT, LES.


Author(s):  
R. Kamali ◽  
A. H. Tabatabaee Frad

It is known that the Lattice Boltzmann Method is not very effective when it is being used for the high speed compressible viscous flows; especially complex fluid flows around bodies. Different reasons have been reported for this unsuccessfulness; Lacking in required isotropy in the employed lattices and the restriction of having low Mach number in Taylor expansion of the Maxwell Boltzmann distribution as the equilibrium distribution function, might be mentioned as the most important ones. In present study, a new numerical method based on Li et al. scheme is introduced which enables the Lattice BoltzmannMethod to stably simulate the complex flows around a 2D circular cylinder. Furthermore, more stable implementation of boundary conditions in Lattice Boltzmann method is discussed.


Author(s):  
Sonam Tanwar

This chapter develops a meshless formulation of lattice Boltzmann method for simulation of fluid flows within complex and irregular geometries. The meshless feature of proposed technique will improve the accuracy of standard lattice Boltzmann method within complicated fluid domains. Discretization of such domains itself may introduce significant numerical errors into the solution. Specifically, in phase transition or moving boundary problems, discretization of the domain is a time-consuming and complex process. In these problems, at each time step, the computational domain may change its shape and need to be re-meshed accordingly for the purpose of accuracy and stability of the solution. The author proposes to combine lattice Boltzmann method with a Galerkin meshfree technique popularly known as element-free Galerkin method in this chapter to remove the difficulties associated with traditional grid-based methods.


Author(s):  
Ru Yang ◽  
Chin-Sheng Wang

A Lattice Boltzmann method is employed to investigate the flow characteristics and the heat transfer phenomenon between two parallel plates separated by a micro-gap. A nine-velocity model and an internal energy distribution model are used to obtain the mass, momentum and temperature distributions. It is shown that for small Knudsen numbers (Kn), the current results are in good agreement with those obtained from the traditional Navier-Stokes equation with non-slip boundary conditions. As the value of Kn is increased, it is found that the non-slip condition may no longer be valid at the wall boundary and that the flow behavior changes to one of slip-flow. In slip flow regime, the present results is still in good agreement with slip-flow solution by Navier Stokes equations. The non-linear nature of the pressure and friction distribution for micro-channel flow is gieven. Finally, the current investigation presents a prediction of the temperature distribution for micro-channel flow under the imposed conditions of an isothermal boundary.


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