多孔介质内自然对流驱动力与流动阻力关系的数值模拟

Numerical simulation of the relationships between the driving force and flow resistance for the natural convection in porous media

采用数值计算方法研究多孔介质内自然对流时驱动力与流动阻力的关系,进而探讨多孔介质中物质和能量的输运问题.针对不同瑞利数Ra,采用QUICK格式离散对流项,基于Matlab软件和自编计算程序,利用SIMPLER算法求解多孔介质的对流换热.结果表明:当lg Ra≤3时,驱动力和流动阻力在同一数量级,随着lg Ra增加,驱动力逐渐大于流动阻力,高温和低温壁面附近的驱动力大于中心部位的驱动力;当lg Ra≤4时,平均传质努塞尔数Nu约为4.7,主要以导热形式进行腔内换热,随着lg Ra逐渐增加,Nu迅速增大,多孔介质内换热主要依靠对流换热进行.

The relationship between driving force and flow resistance during natural convection in porous media is studied using numerical computation method and the problem of mass and heat transfer in porous media is discussed. Considering different Rayleigh number, the convection term is discretized in QUICK format. The heat convection in porous media is solved using SIMPLER algorithm based on Matlab software and self-defined calculation program. The results of the study show that driving force and flow resistance are in the same magnitude when lg Ra≤3, as lg Ra increases, driving force becomes greater than flow resistance gradually, driving force near the high and low temperature wall surface becomes greater than that at the centers when lg Ra≤4, Nu= 4.7, heat is transferred mainly by heat conduction in the cavity, as lg Ra increases gradually, Nu increases rapidly, heat convection is the main way of heat transfer in porous media.