中文摘要：

针对三维矩形腔体中超临界氮氩混合流体的Rayleigh～Benard对流进行了数值模拟，研究了活塞效应、Soret效应和DU{OHr效应在自然对流发生发展过程中所产生的影响．结果显示：3种效应作用下自然对流可分为稳定边界层、对流产生和发展、稳定对流3个阶段．活塞效应在稳定热边界层时期发挥主导作用并促进对流发生，形成双热边界层结构．受温度梯度驱动Soret效应引起组分定向迁移，产生Dufour效应促进能量输运．与拟纯流体对比后发现，

英文摘要：

This paper numerically investigated the natural convection of supercritical nitrogen/argon （n（N2） ： n（Ar）=0.9 ： 0.1, n is amount of substance） binary fluid in a 3-dimensional rectangular cavity. The results showed that a stable thermal boundary layer forms at the bottom of the cavity during the initial heating phase, and the Piston effect plays a dominant role to accelerate the energy transport in this period. After the thermal plume breaks the boundary layer and moves upward, the natural convection occurs with the appearance of a cold boundary layer near the top. The Soret effect caused by the temperature gradient drives the component migration, and results in the Dufour effect which promotes the energy transport. This results indicate that the Soret effect and Dufour effect can promote the heat and mass transfer in the natural convection of supercritical binary fluids.