聚合物添加剂对Rayleigh-Bénard湍流对流热输运的影响

摘要

基于有限体积法采用雷诺应力湍流模型并结合Cross本构方程模拟研究了高分子对Rayleigh-Bénard对流在软（Ra=5×105～4×107）、硬（Ra〉4×107）湍流区热输运的影响。模拟结果显示：添加高分子可加强湍流Rayleigh-Bénard对流热输运,相对于软湍流区在硬湍流区的有效作用范围较大;相应地大尺度环流也随之充满整个腔体,封闭腔体内对角线上两个对称小涡也随着高分子浓度和Ra数的增加而减小。%In this study,the Reynolds-Averaged-Navies-Stokes（RANS）model combined with the Cross Viscosity Equation is applied to the soft turbulence region（Ra =5×105～4×107）and hard turbulence region（Ra4×107）of Rayleigh-Bénard convection（RBC）.The relation curves between heat transport（Nusselt number）and other parameters,as well as flow pattern changes of RBC are obtained with different Rayleigh number and the concentration of the polymer additive.The simulations show that the presence of polymer additive can lead to an enhancement of the heat transfer with larger effect area in the hard turbulence region than in the soft turbulence region.It is also shown that the shorter reversal cycles with higher reversal frequencies occur in the soft turbulence region,and the symmetric vortices in the diagonal corner of enclosed space are reduced accordingly.