基于多松弛格子Boltzmann方法插值反弹运动边界研究

采用多松弛格子Boltzmann方法,结合曲边插值边界处理方法,在固定笛卡尔坐标系均匀网格下,模拟了运动圆柱绕流问题.结合非平衡外推思想,提出了一种新的预估格点分布函数的方法:通过"圆柱表面垂直方向附近的流场内格点的密度和圆柱的速度"构造平衡分布函数,并将其作为新生成格点的分布函数.利用对绝对误差的频谱分析技术,与现有两种方法(基于平均和预估思想)对比结果显示:新提出的方法在具有更高的精度的同时,可以保证仅需要流体域内较少的流动信息,从而为流体内的颗粒碰撞等问题提供了有利条件.通过误差频谱结果,进一步对相应方法中的误差根源进行了讨论,为进一步改进方法提供了依据.对相同雷诺数下加大一倍流场区域的计算结果表明,加大网格可以减小升阻力误差在低频时频谱幅值.

Moving boundary simulation by interpolated bounce back scheme based on multi-relaxation time lattice Boltzmann method

Flow around a moving cylinder was simulated with interpolated bounce back scheme using the frame of multi-relaxation time lattice Boltzmann method.The flow variables on newly generated fluid grid due to cylinder moving were estimated with non-equilibrium extrapolation method: the density distributing populations were calculated according to cylinder velocity and the density on the flow domain grid,which points to the wall perpendicularly.In the frame of frequency analysis,the new method was compared to the traditional scheme.The results show that the presented method is more accurate and that less information in the domain is needed.The frequency analysis also shows the cause of the errors of the method,which can be regarded as a basis for future improvement.In addition,larger Reynolds number tests show that increasing the size of the simulation domain can dramatically reduce errors in the low frequency region.