摘要
在采用计算流体力学−离散元耦合方法(computational fluid dynamics-discrete element method,CFD-DEM)进行固液两相耦合分析时,颗粒计算时间步的选取直接影响到耦合计算精度和计算效率.为此,本文选取每个目标颗粒为研究对象,引入插值函数计算时间步的运动位移,构建可变空间搜索网格;通过筛选可能碰撞颗粒建立搜索列表,采用逆向搜索方式判断碰撞颗粒,从而提出一种改进的DEM方法(modified discrete element method,MDEM).该算法在颗粒群与流体耦合计算中,颗粒计算初始时间步选取不受颗粒碰撞时间限制,通过自动调整和修正实现大步长,由颗粒和流体耦合条件实时更新流体计算时间步,使颗粒计算时间步选取过小导致计算效率低、选取过大导致颗粒碰撞漏判的问题得以解决,为颗粒与流体耦合的数值模拟提供了行之有效的计算方法.通过两个颗粒和多个颗粒的数值模拟,得到的颗粒间碰撞力、碰撞位置及次数,与理论计算结果的相对误差均低于2%,与传统的DEM碰撞搜索算法相比,在选取的3种计算时间步均不会影响计算精度,且有较高的计算效率.通过多个颗粒与流体的耦合数值模拟,采用传统的CFD-DEM方法,只有颗粒计算时间步选取10^(−6)s或更小才能得到精确解,而采用本文方法取10^(−4)s也能够得到精确解,避免了颗粒碰撞随时间步增大而出现的漏判问题,且计算耗时降低了16.7%.
When the computational fluid dynamics discrete element method(CFD-DEM)is used for solid-liquid twophase coupling analysis,the selection of particle calculation time step directly affects the accuracy and efficiency of the coupling calculation.For this reason,each target particle is selected as the research object,and interpolation function is introduced to calculate the motion displacement of the time step,and a variable spatial search grid is constructed.An improved particle collision search algorithm(modified discrete element method,MDEM)was proposed by selecting possible collision particles to build a search list and using reverse search Method to judge collision particles.The algorithm in particle group and fluid coupling calculation,the particle counting the initial time step selection particle collision time without limit,realization of automatic adjustment and correction by large step,calculated by the real-time update of fluid particles and fluid coupling conditions,time step,the granular computing time step selection,as a result of low computational efficiency,selection is too large too small to solve the problem of false negatives,particle collision of particles and fluid coupling numerical simulation provides a effective calculation method.Through the numerical simulation of two particles and multiple particles,the relative errors of the collision forces,collision positions and times between particles obtained are all less than 2%compared with the theoretical calculation results.Compared with the traditional DEM collision search algorithm,the three calculation time steps selected do not affect the calculation accuracy,and the calculation efficiency is higher.Through the coupling numerical simulation of multiple particles and fluid,using the traditional CFD-DEM method,the precise solution can be obtained only when the particle calculation time step is 10−6 s or smaller,while the precise solution can be obtained by using the proposed method to take 10−4 s,which avoids the problem of missed decision caused by particle collision with the increase of time step,and the calculation time is reduced by 16.7%.
作者
刘巨保
王明
王雪飞
姚利明
杨明
岳欠杯
Liu Jubao;Wang Ming;Wang Xuefei;Yao Liming;Yang Ming;Yue Qianbei(School of Mechanical Science and Engineering,Northeast Petroleum University,Daqing 163318,Heilongjiang,China;School of Mechanical and Aerospace Engineering,Nanyang Technological University,639798,Singapore)
出处
《力学学报》
EI
CAS
CSCD
北大核心
2021年第6期1569-1585,共17页
Chinese Journal of Theoretical and Applied Mechanics
基金
国家自然科学基金资助项目(11972114,51904075).