水平板自然对流换热的非线性特性

采用SIMPLE算法,QUICK差分方案,对封闭方腔内水平板自然对流换热进行了数值模拟.数值结果显示,低Ra数时流动和换热处于稳态,当Rayleigh数超过某一临界值时,流动和换热就会发生非稳态振荡,此时流动和换热表现出非对称性.对不同Rayleigh数,流动和换热通过单周期分岔从稳态过渡到非稳态,并通过倍周期分岔过渡到混沌.在混沌区,仍然会出现周期性窗口,并且数值结果与初始条件有关.

NONLINEAR CHARACTERS OF NATURAL CONVECTION AROUND A HORIZONTAL PLATE IN AN ENCLOSURE

Numerical investigation using SIMPLE algorithm with QUICK scheme for the nonlinear phenomena of natural convection around a horizontal flat plate has been conducted.It can be found from the numerical results that flow and heat transfer around the horizontal flat plate will be steady at small Rayleigh numbers.When the Rayleigh number is over some critical value,it can be found that flow and heat transfer will be asymmetry which indicates unsteady oscillation occurs.By nonlinear analyses,it is shown that with the increase of Rayleigh number,flow and heat transfer will change from steady to unsteady state through HOPF bifurcation,and transition to chaos will occurs through multi-periodical oscillation.In the chaotic region,even though it is difficult to predict flow pattern, periodical windows still can be observed.When chaos occurs,numerical results will dramatically depended on the initial condition.