A shifting discontinuous-grid-block lattice Boltzmann method for moving boundary simulations
TL;DR: In this article, a translating discontinuous-grid-block model for moving boundaries of finite thickness based on multi-relaxation time version of lattice Boltzmann method has been developed.
Abstract: A translating discontinuous-grid-block model for moving boundaries of finite thickness based on multi-relaxation time version of lattice Boltzmann method has been developed. The implementation of this model to simulate moving boundary flows has been demonstrated for the cases of a cylinder in simple shear flow, a single rigid wing executing ‘clap and fling’ motion, and the propulsion of a plunging flat plate. A number of interpolation schemes of linear, quadratic and cubic natures are assessed around the discontinuous grid interface. It is shown that the implementation of a body-fitted refined mesh that moves along with the object reduces the spurious oscillations registered in the force and velocity measurements compared to a single coarse grid block. Moreover, use of multiple relaxation times helps overcome stability issues at high Reynolds number, normally encountered in the single-relaxation time model. Significantly, in the former model the same base grid could handle flows with good accuracy for 10 ≤ Re ≤ 1000. The proposed technique offers significant advantage in terms of capturing flow around moving solids at lower computational cost and simulation time as compared to the stationary discontinuous-grid-block method.
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22 Jun 2015
TL;DR: The aim of the present study is to understand the mechanism of propulsion in biological flyers, initially starting from rest, using a computational analysis of the plunging motion of a flexible wing using the lattice-Boltzmann method.
Abstract: The aim of the present study is to understand the mechanism of propulsion in biological flyers, initially starting from rest, using a computational analysis of the plunging motion of a flexible wing. Simulations are performed on a self-propelled flexible wing unconstrained to move in direction perpendicular to the heaving motion. A two-dimensional lumped torsional flexibility model has been developed for a multi-component system which mimics a real insect wing. Using the lattice-Boltzmann method, this model is used to investigate the role of chordwise flexibility on fluid mechanics associated with forward propulsion. The aerodynamics and vortical wake patterns at different frequencies are investigated for a range of Reynolds number and bending stiffnesses. In addition, the behavior of input power and efficiency with stiffness has been examined. This work is anticipated to pave the way towards an improved understanding of propulsion in biological flyers employing flexible wings and thereby contribute to development of micro-air vehicles employing the same concept.
2 citations
Cites background or methods from "A shifting discontinuous-grid-block..."
...The fluid solver has been used in our earlier publications [9,28,55] and has already been validated....
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...The methodology of a moving multi-block LBM is given elsewhere [55]....
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...The size of the block was 2C×3C and the plunging of the wing was confined in it and as the wing translated, the fine block moved along with it [55]....
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TL;DR: In this paper , a series of simulations of particle-laden flows were performed using the regularized lattice Boltzmann method (RLBM) coupled with the virtual flux method (VFM) or the immersed boundary method (IBM) with the multi-direct forcing approach.
2 citations
TL;DR: In this article , a buffer grid is proposed for the first time at the interface of different levels of grids, which is used to remove the temporal interpolation calculation and simplify the spatial interpolation calculations.
Abstract: The traditional multi-level grid multiple-relaxation-time lattice Boltzmann method (MRT-LBM) requires interpolation calculations in time and space. It is a complex and computationally intensive process. By using the buffer technique, this paper proposes a new multi-level grid MRT-LBM which requires only spatial interpolation calculations. The proposed method uses a center point format to store multi-level grid information. The grid type determination in the flow field calculation domain is done using the axis aligned bounding box (AABB) triangle overlap test. According to the calculation characteristics of MRT-LBM, the buffer grid is proposed for the first time at the interface of different levels of grids, which is used to remove the temporal interpolation calculation and simplify the spatial interpolation calculation. The corresponding multi-level grid MRT-LBM algorithm is also presented for two-dimensional and three-dimensional flow field calculation problems. For the two-dimensional problem of flow around a circular cylinder, the simulation results show that a four-level grid MRT-LBM proposed in this paper can accurately obtain the aerodynamic coefficients and Strouhal number at different Reynolds numbers, and it has about 1/9 of the total number of grids as a single-level grid MRT-LBM and is 6.76 times faster. For the three-dimensional flow calculation problem, the numerical experiments of flow past a sphere are simulated to verify the numerical precision of the presented method at Reynolds numbers = 100, 200, 250, 300, and 1000. With the streamlines and velocity contours, it is demonstrated that the multi-level grid MRT-LBM can be calculated accurately even at the interface of different size grids.
1 citations
20 Jun 2022
TL;DR: In this paper , a three-dimensional numerical framework of a shifting multi-grid block for moving boundaries based on multi-relaxation time lattice Boltzmann method is developed.
Abstract: A three-dimensional numerical framework of a shifting multi-grid block for moving boundaries based on multi-relaxation time lattice Boltzmann method is developed. This work is an extension of our previous two-dimensional algorithm [1] with significant improvements where low-order temporal interpolation has been replaced with a higher-order spatial interpolation scheme. The model has been validated for the cases i.e., sedimentation of a solid sphere in a fluid medium under the action of gravity. The results demonstrate that the moving multi-block improves the resolution of a geometry that reduces the fluctuations registered in velocity and force measurements for the single coarse mesh. This approach offers a substantial advantage in terms of a significant reduction in computational cost as the grid is refined only locally around the moving body as against a fully refined computational domain.
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TL;DR: An overview of the lattice Boltzmann method, a parallel and efficient algorithm for simulating single-phase and multiphase fluid flows and for incorporating additional physical complexities, is presented.
Abstract: We present an overview of the lattice Boltzmann method (LBM), a parallel and efficient algorithm for simulating single-phase and multiphase fluid flows and for incorporating additional physical complexities. The LBM is especially useful for modeling complicated boundary conditions and multiphase interfaces. Recent extensions of this method are described, including simulations of fluid turbulence, suspension flows, and reaction diffusion systems.
6,565 citations
TL;DR: In this article, a general technique for simulating solid-fluid suspensions is described, which combines Newtonian dynamics of the solid particles with a discretized Boltzmann equation for the fluid phase; the many-body hydrodynamic interactions are fully accounted for, both in the creeping flow regime and at higher Reynolds numbers.
Abstract: A new and very general technique for simulating solid–fluid suspensions is described; its most important feature is that the computational cost scales linearly with the number of particles. The method combines Newtonian dynamics of the solid particles with a discretized Boltzmann equation for the fluid phase; the many-body hydrodynamic interactions are fully accounted for, both in the creeping-flow regime and at higher Reynolds numbers. Brownian motion of the solid particles arises spontaneously from stochastic fluctuations in the fluid stress tensor, rather than from random forces or displacements applied directly to the particles. In this paper, the theoretical foundations of the technique are laid out, illustrated by simple analytical and numerical examples; in a companion paper (Part 2), extensive numerical tests of the method, for stationary flows, time-dependent flows, and finite-Reynolds-number flows, are reported.
2,073 citations
TL;DR: It is shown that the lattice BoltZmann equation is a special discretized form of the Boltzmann equation, which means that the two-dimensional 6-bit, 7-bit and 9-bit models derived include the three-dimensional 27- bit models.
Abstract: In this paper, the lattice Boltzmann equation is directly derived from the Boltzmann equation. It is shown that the lattice Boltzmann equation is a special discretized form of the Boltzmann equation. Various approximations for the discretization of the Boltzmann equation in both time and phase space are discussed in detail. A general procedure to derive the lattice Boltzmann model from the continuous Boltzmann equation is demonstrated explicitly. The lattice Boltzmann models derived include the two-dimensional 6-bit, 7-bit, and 9-bit, and three-dimensional 27-bit models.
1,542 citations
TL;DR: In this paper, a general technique for simulating solid-fluid suspensions is described, which combines Newtonian dynamics of the solid particles with a discretized Boltzmann equation for the fluid phase; the many-body hydrodynamic interactions are fully accounted for, both in the creeping flow regime and at higher Reynolds numbers.
Abstract: A new and very general technique for simulating solid-fluid suspensions is described; its most important feature is that the computational cost scales linearly with the number of particles. The method combines Newtonian dynamics of the solid particles with a discretized Boltzmann equation for the fluid phase; the many-body hydrodynamic interactions are fully accounted for, both in the creeping-flow regime and at higher Reynolds numbers. Brownian motion of the solid particles arises spontaneously from stochastic fluctuations in the fluid stress tensor, rather than from random forces or displacements applied directly to the particles. In this paper, the theoretical foundations of the technique are laid out, illustrated by simple analytical and numerical examples; in the companion paper, extensive numerical tests of the method, for stationary flows, time-dependent flows, and finite Reynolds number flows, are reported.
1,335 citations
TL;DR: In this paper, the lattice Boltzmann equation (LBE) is applied to high Reynolds number incompressible flows, some critical issues need to be addressed, noticeably flexible spatial resolution, boundary treatments for curved solid wall, dispersion and mode of relaxation, and turbulence model.
861 citations