时间步长对格子玻尔兹曼法模拟室内气流精度的影响
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作者单位:

华中科技大学 建筑与城市规划学院,湖北 武汉 430074

作者简介:

韩梦涛(1987—),男,副研究员,硕士生导师,工学博士,主要研究方向为建筑与城市风热环境、绿色建筑。E-mail: hanmt@hust.edu.cn

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中图分类号:

TU11;TB126

基金项目:

中央高校基本科研业务费专项资金(2021XXJS053)


Effect of Time Steps on Accuracy of Indoor Airflow Simulation Using Lattice Boltzmann Method
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Affiliation:

School of Architecture and Urban Planning, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China

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    摘要:

    基于格子玻尔兹曼法的大涡模拟(LBM-LES)是湍流模拟的新方法,但不恰当的时间步长δt可能会影响其计算精度。首先理论总结了δt可能对LBM-LES湍流模拟造成的影响,阐明过大的δt会导致速度场产生压缩性误差,而过小的δt会导致超松弛碰撞产生速度场的数值振荡。其次,通过对等温室内气流案例进行LBM-LES模拟,定量讨论了δt引起的压缩性误差和数值振荡问题。结果表明,δt较大时流场密度变化剧烈,且格子玻尔兹曼单位的马赫数(M)超过0.3的区域中速度场产生了明显的压缩性误差。同时,过小的δt导致平均及脉动风速均产生了数值振荡,这在网格分辨率较高时尤为明显。建议模拟时在确保δt足够小以满足最大风速区域的M<0.3的基础上,尽量增大δt以防止产生数值振荡。

    Abstract:

    Lattice Boltzmann method-based large-eddy simulation (LBM-LES) is a new method to solve turbulence problems in recent decades. However, improper time step settings may affect the simulation accuracy of LBM-LES. This paper first analyzed and summarized the impact of time step δt on the results of LBM-LES,theoretically. An oversized δt will cause compressibility error in the velocity field, while a too small δt can lead to the over-relaxation colliding mode, causing the numerical oscillation of velocity field. Subsequently, LBM-LES simulations of an isothermal indoor airflow case were conducted to discuss these errors quantitatively. The results show that a large δt leads to a sharp density change, and the velocity field in the regions where the Mach number (M) in the lattice Boltzmann unit exceeds 0.3 showing that there are obvious compressibility errors. Meanwhile, a too-small δt causes apparent numerical oscillations of both time-averaged and fluctuating velocities. This phenomenon is more significant when the grid resolution is higher. Therefore,it is suggested that δt should be small enough to ensure M<0.3 in the maximum velocity regions, based on which, a larger δt should be utilized to prevent numerical oscillations.

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韩梦涛.时间步长对格子玻尔兹曼法模拟室内气流精度的影响[J].同济大学学报(自然科学版),2022,50(6):793~801

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  • 收稿日期:2021-10-15
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  • 在线发布日期: 2022-07-04
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