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为了揭示封闭腔内非Boussinesq流体在浮力驱动下所特有的流动换热现象和形成机理,采用CFD软件Fluent对封闭腔内水的自然对流进行数值模拟,得到矩形封闭腔高宽比、Rayleigh数、倾斜角度、壁面温度差对流动和传热的影响规律。研究结果表明:由于水的密度在3.98℃达到最大,两竖壁面温度跨越这一点时会引起流动图像反转;具有流动反转的双涡结构降低了对流换热平均Nusselt数;相同Rayleigh数下,高宽比为1对应对流换热平均Nusselt数最大值;倾斜角度对平均Nusselt数影响与Rayleigh数和温度边界条件有关。
In order to reveal the phenomenon of flow heat transfer and formation mechanism of non-Boussinesq fluid in buoyancy-driven closed cavity, CFD software Fluent was used to simulate the natural convection of closed cavity water, and the aspect ratio, Rayleigh number, Tilt angle, wall temperature difference on the flow and heat transfer law. The results show that as the density of water reaches the maximum at 3.98 ℃, the flow image reverses when the temperature of two vertical walls exceeds this point. The double-vortex structure with flow reversal reduces the average Nusselt number of convective heat transfer. Under the same Rayleigh number , The aspect ratio of 1 corresponds to the maximum of convective heat transfer average Nusselt number; the influence of tilt angle on average Nusselt number is related to Rayleigh number and temperature boundary conditions.