Improved wall model treatment for aerodynamic flows in LBM

Degrigny, Johan; Cai, Shang-Gui; Boussuge, Jean‐François; Sagaut, Pierre

doi:10.1016/j.compfluid.2021.105041

Cited by 23 publications

(12 citation statements)

References 67 publications

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“…To obtain the friction velocity on the boundary points, it is preferable to interpolate the friction velocity instead of the flow velocity from the neighbor points. 18,19 It, thus, needs to invert the wall model at neighbor points, but it does not increase significantly the computation thanks to the explicit wall model. It is found in Cai et al 18 that the surface quantities are greatly smoothed even with a low order interpolation kernel, such as the inverse distance weighting.…”

Section: Attached Boundary Layermentioning

confidence: 99%

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Application of immersed boundary based turbulence wall modeling to the Ahmed body aerodynamics

et al. 2022

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This paper applies a recently developed immersed boundary-turbulence wall modeling approach to turbulent flows over a generic car geometry, known as the Ahmed body, under massive flow separation, within a lattice Boltzmann solver. Although the immersed boundary method combined with hierarchical Cartesian grid offers high flexibility in automatic grid generation around complex geometries, the near-wall solution is significantly deteriorated compared to the body-fitted simulation, especially when coupled to wall models for turbulent flows at high Reynolds number. Enhanced wall treatments have been proposed in the literature and validated for attached flow configurations. In this work, the Ahmed body with a slant surface of angle 35o is considered where the flow separates massively over the slant surface and the vertical base. The large eddy simulation is performed with a Reynolds stress constraint near-wall. The eddy viscosity is computed dynamically by taking into account the actually resolved Reynolds stresses. It approaches the mixing length eddy viscosity in attached boundary layers and returns to the subgrid eddy viscosity in detached boundary layers. An explicit equilibrium wall model has been also proposed to accelerate the calculation. Comparison with the no-slip boundary condition on the separated surfaces shows that the near-wall treatments with the equilibrium wall model operate reasonably well on both attached and detached boundary layers.

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Section: Attached Boundary Layermentioning

confidence: 99%

“…Retrieving the boundary points away from walls is also useful to reduce the oscillations, such as Ref. 19. It is found in Ref.…”

Section: Introductionmentioning

confidence: 99%

Application of immersed boundary based turbulence wall modeling to the Ahmed body aerodynamics

et al. 2022

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“…They validate the case on just one angle of attack, for low Re (up to 42,000). Degrigny et al (2021) used the same LBM–LES approach to investigate fluid flow around the airfoil for high Re . Finally, Wilhelm et al (2018) investigated the same problem with an LBM–RANS coupled model, but for a different airfoil.…”

Section: Introductionmentioning

confidence: 99%

Experimental and LBM analysis of medium-Reynolds number fluid flow around NACA0012 airfoil

Rak

Grbčić

Sikirica

et al. 2023

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Purpose The purpose of this paper is the examination of fluid flow around NACA0012 airfoil, with the aim of the numerical validation between the experimental results in the wind tunnel and the Lattice Boltzmann method (LBM) analysis, for the medium Reynolds number (Re = 191,000). The LBM–large Eddy simulation (LES) method described in this paper opens up opportunities for faster computational fluid dynamics (CFD) analysis, because of the LBM scalability on high performance computing architectures, more specifically general purpose graphics processing units (GPGPUs), pertaining at the same time the high resolution LES approach. Design/methodology/approach Process starts with data collection in open-circuit wind tunnel experiment. Furthermore, the pressure coefficient, as a comparative variable, has been used with varying angle of attack (2°, 4°, 6° and 8°) for both experiment and LBM analysis. To numerically reproduce the experimental results, the LBM coupled with the LES turbulence model, the generalized wall function (GWF) and the cumulant collision operator with D3Q27 velocity set has been used. Also, a mesh independence study has been provided to ensure result congruence. Findings The proposed LBM methodology is capable of highly accurate predictions when compared with experimental data. Besides, the special significance of this work is the possibility of experimental and CFD comparison for the same domain dimensions. Originality/value Considering the quality of results, root-mean-square error (RMSE) shows good correlations both for airfoil’s upper and lower surface. More precisely, maximal RMSE for the upper surface is 0.105, whereas 0.089 for the lower surface, regarding all angles of attack.

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“…However as no underlying mesh will conform to the solid boundary, the imposition of boundary condition at the interface can be tricky. Interpolation methods are often selected to overcome this problem, either by locally reconstructing the velocity 9,10 or by adopting a source forcing function in the momentum equation [5][6][7][8] . In fact, the two approaches are essentially the same as they both rectify the velocity in the vicinity of immersed boundary to produce solid effect 11 .…”

Section: Introductionmentioning

confidence: 99%

“…Fluid) Predict the velocity ṽn+1 f using(10); Initialize values: (•) k=0,n+1 = (•) n , where (•) includes x s , ẋs , F;4 for k = 0 to k max do 5 Fluid) Construct or update the interpolation operator matrix T (x k,n+1 s ) and the moving force coefficient matrix M (x k,n+1 s )Fluid) Interpolate the fluid velocity T (x k,n+1 Interface) Solve the moving force equation (12a) for F k+1,n+1 with ẋk,n+1 s ; Solid) Compute the solid equations for (x k+1,n+1 s ||(•) k+1,n+1 − (•) k,n+1 ||/||(•) k+1,n+1 || < tolerance then 10 (•) n+1 = (•) k+1,n+1 ; Fluid) Correct the fluid velocity to vn+1 f with F n+1 using (12b); 17 (Fluid) Solve the pressure Poisson equation and compute the final velocity v n+1 f…”

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confidence: 99%

Moving immersed boundary method for fluid–solid interaction

2022

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A strongly coupled algorithm is presented for the incompressible fluid-rigid body interaction using the moving immersed boundary method. The pressure and the boundary force are treated as Lagrange multipliers to enforce the incompressibility and no-slip wall constraints. To compute the two unknowns from the velocity field, we adopt the fractional step algorithm and successively apply the two constraints. A Poisson equation and a moving force equation are derived for the pressure and the boundary force respectively. As both coefficient matrices are formulated to be symmetric and positive-definite, the resulting linear systems are solved efficiently with the conjugate gradient solver. The strongly-coupled nonlinear fluid-solid system is achieved by a fixed point iteration. To improve the computational efficiency, we only iterate the moving force equation with the rigid body motion equation and the time-consuming pressure Poisson equation is solved once the sub-iteration is finished. The proposed method is validated with various benchmark tests and the results compare well with the literature.

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Improved wall model treatment for aerodynamic flows in LBM

Cited by 23 publications

References 67 publications

Application of immersed boundary based turbulence wall modeling to the Ahmed body aerodynamics

Application of immersed boundary based turbulence wall modeling to the Ahmed body aerodynamics

Experimental and LBM analysis of medium-Reynolds number fluid flow around NACA0012 airfoil

Moving immersed boundary method for fluid–solid interaction

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