一种含有复杂外形运动物体的高效IB-LBM算法研究

The immersed boundary-lattice Boltzmann method (IB-LBM) is a feasible numerical method for simulating flows around moving objects. In conventional IB-LBM, the approximate satisfaction of boundary condition and low accuracy of solution near the boundary are its two major shortcomings. As a consequenc, the accuracy of force calculation on the boundary and numerical stability of method would be affected. In this project, an efficient IB-LBM for dealing with moving objects is developed. Firstly, based on our proposed boundary condition-enforced IB-LBM, the non-physical oscillation of forces on the boundary can be suppressed by using the smoothed delta function. Meanwhile, by applying the technique of adaptive mesh refinement to IB-LBM simulation for the first time, the efficiency of method can be improved and the drastic variation in flow field can be captured accurately. Secondly, by utilizing the Lagrangian interpolation with second order accuracy, a different way to deal with the boundary without use of delta function is developed. As a result, the accuracy of flow solution around the boundary is improved. Employing the proposed IB-LBM, numerious moving boundary flow problems with different geometries are simulated. Moreover, through the simulation of fish swimming and dragonfly flight, the accuracy and efficiency of the proposed method for handling moving boundary flow problems with complex geometry are validated. The research work in this project could offer a reliable CFD method and tool for dealing with the moving boundary flow problems accurately and effectively.

浸入边界-格子波尔兹曼法(IB-LBM)是一种有效模拟动边界问题的数值方法。在现有的IB-LBM中，存在着边界条件不精确满足和物面附近数值解精度低的两个主要问题，从而影响物体受力计算的准确性和数值方法的稳定性。因此，本项目的目的是发展一种高效地模拟动边界问题的IB-LBM。首先，在申请人提出的精确满足边界条件的IB-LBM基础上，通过使用光滑的delta函数，抑制物体受力的非物理震荡；首次把网格自适应技术应用到IB-LBM中，提高计算效率并精确捕捉流动的剧烈变化。其次，通过使用二阶精度的Lagrangian插值，发展一种无delta函数的边界处理方法，提高物面附近流场解的精度。应用这些方法，模拟多种含不同外形的动边界问题。此外，通过模拟鱼游和蜻蜓飞行，验证数值方法处理复杂外形动边界问题的准确性和有效性。通过本项目的研究，可以为准确而有效地处理动边界问题提供可靠的CFD模拟方法和工具。

浸入边界-格子波尔兹曼法（IB-LBM）是一种有效模拟动边界问题的数值方法。在现有的IB-LBM中，存在着边界条件不精确满足和物面附近数值解精度低的两个主要问题，从而影响物体受力计算的准确性和数值方法的稳定性。因此，本项目完善和发展了一种高效地模拟动边界问题的IB-LBM，使其能够准确而有效地模拟复杂物体在流体中的运动。首先，通过使用光滑的delta函数，抑制了物体受力的非物理震荡。其次，把网格自适应技术应用到IB-LBM中，提高计算效率并精确捕捉流动的剧烈变化。应用发展的新算法，模拟研究了多种复杂的动边界问题，包括钝体流动控制和基于拍动翼的新型能量采集系统。基于本项目的研究成果，共计发表了21篇SCI学术论文。通过本项目的研究，可以为准确而有效地处理动边界问题提供可靠的CFD模拟方法和工具。