中文摘要：

采用非稳态数学模型对具有对称和非对称结构的顶部送风二维方腔内混合对流流场与温度场进行了数值求解．数值计算中控制参数Ra取为固定值10^6，Re在1000～3000范围内变化．数值结果显示，随Re的增大，具有对称结构问题的数值解会分别出现定常解、周期性振荡解和非周期性振荡解；而对于非对称结构问题，数值解的最大网格Pe虽然大于对称结构问题的最大网格Pe，数值解是定常的，并未发生解的振荡．因此，判明具有对称结构的顶部送风二雏方腔内混合对流问题数值解的振荡是客观存在的物理振荡，而非数值方法不稳定所引起的数值振荡。

英文摘要：

Velocity fields and temperature fields are numerically analysed using an unsteady mathematical model for mixed convection in a rectangular cavity with symmetric and unsymmetrical top supplying air. The Rayleigh number Ra is fixed at 10^6 and Reynolds number Re is given in a range of 1 000 to 3 000. The numerical results obtained show that increasing the Reynolds number the numerical solutions change from steady symmetric state to periodically oscillatory and then to non-periodically oscillatory one for the problem with symmetric top supplying air. However, numerical solutions obtained are steady for the problem with unsymmetrical top supplying air though the maximum grid Peeler number Pe is greater than that with symmetric top supplying air. Therefore, it can be illustrated that the solution oscillation is a physical oscillation for the mixed convection in a rectangular cavity with symmetric top supplying air, and it is not a numerical oscillation.