多孔介质方腔内双扩散自然对流熵产的格子Boltzmann模拟

Entropy Generation in Double-diffusive Natural Convection in a Square Porous Enclosure:Lattice Boltzmann Method

用格子Boltzmann方法对倾斜多孔介质方腔内流体双扩散自然对流的熵产进行数值模拟,分析孔隙率(0.2≤ε≤0.9)、瑞利数(10^(3)≤Ra≤10^(6))、浮力比(-4≤Br≤2)和倾斜角(0°≤γ≤80°)对局部熵产与总熵产的影响。结果表明:(1)当ε和Ra增加时,因流动与传热传质引起的局部熵产峰值升高,流动熵产对总熵产的贡献逐步增大,净流体摩擦项在流动熵产中占比升高;(2)Br=-1是局部熵产分布发生变化的临界值,此时熵产趋于零;(3)随着倾斜角的增大,局部流动熵产的高熵产区域沿着顺时针方向移动;当γ=40°时,净流体摩擦造成的熵产达到极大值而达西耗散造成的熵产峰值出现在γ=60°。

A Darcy-Brinkman-Forchheimer model based lattice Boltzmann method is conducted to the simnlation of double-diffusive natural convection in an inclined square porous enclosure.Effects of porosity(0.2≤ε≤0.9),Rayleigh number(10^(3)≤Ra≤10^(6)),buoyancy ratio(-4≤Br≤2)and inclination angle(0°≤γ≤80°)on the local and total entropy generation are systematically investigated.It shows that asεand Ra increased,peaks of local entropy generation due to heat transfer,fluid friction and mass transfer grow higher and the contribution of fluid friction to total entropy generation increased prominently.In addition,the clear fluid term has more influence on fluid friction entropy generation.Br=-1 is a critical value for the change of local entropy generation distribution.At the same time,the total entropy generation tends to zero.With the increase of inclination angle,the high entropy generation region of local fluid friction entropy generation moves clockwise.The maximum entropy caused by clear fluid term and Darcy dissipation term appears at 40°and 60°,respectively.