滑移区稀薄气体外掠圆柱体换热的数值分析

摘要

针对滑移流区稀薄气体横掠圆柱体的强制对流换热问题,采用气体分子动力学,对速度滑移与温度跳跃边界条件以热流密度项与壁面切应力项形式进行修正,并植入到Fluent软件中,实现滑移流区换热的数值模拟.对雷诺数Re范围为0.001～20、克努森数Kn范围为0.001～3的工况进行了数值计算,并与实验结果进行对比.结果表明:采用滑移边界修正的CFD模型,可实现对稀薄气体滑移流区流动换热的精确模拟;当气体流态处于连续流状态(Kn≤0.01)时,边界条件的变化对数值结果影响不大;当气体流态处于滑移流状态(Kn范围为0.01～0.1)时,采用提出的滑移边界修正模型将能得到更加准确的计算结果;并且采用该模型可以对部分过渡流区(0.1＜Kn＜2)的换热进行数值预示.此方法可广泛应用于工程中滑移区流体的换热情况,为研究稀薄气体滑移流区流动换热问题提供一种有效的数值模拟方法.%For lift-off of launch vehicles,the flow regimes of gas over the wall of the tank varies with altitude,which leads to changing characteristics of the heat transfer between the tank wall and atmosphere.To reveal the characteristics of convective heat transfer across a circular cylinder for rarefied gas,the boundary conditions for the velocity slip and temperature jump are presented.A modified method of Fluent model is developed to predict the heat transfer in slip flow region within the ranges of Reynolds number from 0.001 to 20 and Knudsen number from 0.001 to 3,and in these regions,the numerical simulation results are compared with the experimental data.The results show that in continuous flow region (Kn≤0.01),different boundary conditions exert little influence on the results.However,for slip flow region(0.01＜ Kn≤0.1),the predicted results with the modified boundary condition become more accurate,and this method with the modified boundary condition could extend to partial transition flow region (0.1＜Kn＜2)to predict heat exchange.