湍流热对流DNS多分辨率并行直接求解方法

Multiple-resolution Parallel Direct Method of DNS for Turbulence Thermal Convection

依据温度标量场与动量计算的空间和时间计算分辨率不同的特点,采用两套网格,建立多分辨率双网格并行直接求解方法,用以解决极高Ra数湍流热对流DNS模拟巨大计算工作量的难题.在两套网格的数据交换上,根据每个细网格都满足连续方程,设计了速度的守恒平移插值方法.二维极高Ra数湍流热对流的计算结果表明,采用多分辨率双网格并行直接求解方法的DNS计算,可以使计算工作量降低近一个量级.瞬时温度场显示,双网格方法的计算结果可以很好地描述极高Ra数下快速运动的小尺寸漩涡团状羽流,得到的结果与原网格一致,不同方法计算得到的传热Nu数误差不超过1%.

Spatial and time resolution of thermal scalar field and velocity fields are different in turbulence thermal convection.A multiple-resolution parallel direct method for DNS with two different girds is presented to solve the problem of huge computational cost in simulation of turbulence thermal convection with very high Rayleigh numbers.A constant translation interpolation method of speed was designed to meet continuous equations at each finer gird in data transformation between coarser gird and finer gird.Simulations of 2D turbulence thermal convection with very high Rayleigh numbers show that computational cost is reduced an order of magnitude by using this method.Small-scale eddy-like plumes,that move rapidly in thermal convection,are well performed in instantaneous temperature fields.It is consistent with results with a single gird.Difference of Nusselt number obtained by two methods is below 1%.