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Numerical investigation of flow characteristics around two side-by-side cylinders by immersed boundary-lattice Boltzmann flux solver

基于浸入边界-格子波尔兹曼通量求解法的并列双圆柱流动特性数值研究

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Abstract

In this paper, to study the characteristics of the flow in a laminar regime, an immersed boundary-lattice Boltzmann flux solver (IB-LBFS) is applied to numerically simulate the unsteady viscous flows around two fixed and rotating circular cylinders in side-by-side arrangement. This method applies finite volume discretization to solve the macroscopic governing equations with the flow variables defined at cell centers. At the cell interface, numerical fluxes are physically evaluated by a local lattice Boltzmann solution. In addition, the no-slip boundary condition is accurately imposed by using the implicit boundary condition-enforced immersed boundary method. Due to the simplicity and high efficiency of IB-LBFS on non-uniform grids, it is suitable for simulating fluid flows with complex geometries and moving boundaries. Firstly, numerical simulations of laminar flow past two side-by-side cylinder are performed with different gap spacings at Reynolds numbers of 100 and 200. The simulation results show that a small gap spacing induces a biased flow and forms an irregular big wake behind two cylinders at a low Reynolds number. As the gap spacing increases, an in-phase or anti-phase flow is observed. Then, the effects of the main important parameters on flow characteristics are analyzed for flow past two side-by-side rotating cylinders, including the rotational speed, Reynolds number, and gap spacing. As the rotational speed is increased, the numerical results illustrate that unsteady wakes are suppressed and the flow becomes steady. As the gap spacing is increased, two separate vortex streets behind each cylinder are formed with a definite phase relationship and single shedding frequency.

摘要

目的

本文旨在应用新型数值求解方法,即浸入边界-格子波尔兹曼通量求解法,研究并列双圆柱流动特性,并探索该数值方法在工程应用中的可行性。

创新点

1. 将浸入边界法与格子波尔兹曼求解法相结合,简单并高效地实现在非均匀直角网格下求解不可压流动以及动边界问题;2. 应用浸入边界-格子波尔兹曼求解法研究并列双圆柱流场特性。

方法

1. 通过理论推导,建立状态变量和通量与格子波尔兹曼方程中粒子密度分布函数之间的关系(公式(8)~(10));2. 采用强制浸入边界法处理流固界面使固壁表面满足无滑移边界条件,实现在笛卡尔网格下求解运动边界问题;3. 通过数值模拟,探讨雷诺数和圆柱间距对静止双圆柱受力及流场尾流特性的影响以及雷诺数、间距和旋转速度对旋转并列双圆柱受力及尾流特性的影响规律。

结论

1. 浸入边界-格子波尔兹曼求解法可以简单实现采用非贴体网格求解不可压流动及动边界问题。2. 对于并列静止双圆柱,随着间距的增加,双圆柱尾流场的相互作用逐渐消失,尾迹由无规则性转变为规则的同相位流动或反向流动;雷诺数影响圆柱受力系数。3. 对于并列旋转双圆柱,雷诺数对旋转圆柱受力影响较弱;旋转速度可以抑制单圆柱尾流场的非定常效应;随着圆柱间距的增加,双圆柱后方形成固定的相位关系以及同一频率的脱落涡。

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Correspondence to Xiao-di Wu.

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Wu, Xd., Liu, Hp. & Chen, F. Numerical investigation of flow characteristics around two side-by-side cylinders by immersed boundary-lattice Boltzmann flux solver. J. Zhejiang Univ. Sci. A 19, 384–398 (2018). https://doi.org/10.1631/jzus.A1700112

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  • DOI: https://doi.org/10.1631/jzus.A1700112

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