基于能量守恒耗散粒子动力学方法的自然对流模拟改进研究

Improvement of natural convection simulation based on energy conservation dissipative particle dynamics

能量守恒耗散粒子动力学(eDPD)是一种研究热输运过程的介观尺度数值模拟方法,然而在eDPD系统内引入Boussinesq假设以研究自然对流问题时,eDPD系统自身的热膨胀性对模拟结果的影响常常被忽略.首先研究了eDPD系统的热膨胀性,通过模拟获得eDPD系统的热膨胀系数β;并由此模拟了不同瑞利数Ra、不同几何结构下的自然对流;利用eDPD系统自身的热膨胀性,在不引入Boussinesq假设的前提下获得了合理的温度场和速度场,与相同Ra数下有限体积法模拟结果相比,误差明显小于以往研究中相同条件下的对比误差.研究表明在eDPD系统中引入Boussinesq假设时,需要考虑eDPD系统自身热膨胀性的影响,并且进一步对Ra数的计算进行了修正.

Energy conservation dissipative particle dynamics(eDPD)is a mesoscale numerical simulation method of studying the heat transport process.In previous studies,when the Boussinesq assumption was introduced into the eDPD system to study the natural convection,the system was generally considered to be incompressible,and the effect of the thermal expansion of the eDPD system itself on the simulation results was often neglected,which would cause errors in the simulation.In the present study,the thermal expansion characteristic of the eDPD system is first investigated,and the thermal expansion coefficient b of the eDPD system is obtained by eDPD simulation.Then,based on the thermal expansion characteristic of the eDPD system itself,the natural convection is simulated with different values of Rayleigh number Ra and different geometries,specifically,square cavity,concentric rings,and eccentric rings,and reasonable temperature and velocity fields are obtained,and they are in agreement with the simulated results by the finite volume method(FVM).The error between the eDPD simulation,in which the natural convection is driven by thermal expansion of the eDPD system itself,and FVM simulated result is considerably smaller than the errors observed in previous studies where Boussinesq assumption was directly adopted to simulate natural convection phenomena while neglecting the thermal expansion effect of eDPD system.It is shown that the effect of the eDPD system’s own thermal expansion characteristic needs to be considered when introducing the Boussinesq assumption in the eDPD system,and further,the calculation of the Ra number is modified in this paper.