轴向通流旋转盘腔内类Rayleigh-Benard对流稳定性研究

Investigation of Rayleigh-Benard-like convection stabilities in rotating cavity with axial throughflow of cooling air

利用数值模拟的方法对冷气轴向通流旋转盘腔的流动过程进行了研究。研究发现 ,对应一进口冷气的雷诺数 ,存在一临界瑞利数 ( Rac) ,高于该瑞利数 ( Ra) ,流动出现不稳定现象 ,且 Ra越大 ,不稳定行为越严重。对于特例 ,盘腔内的流动可以看成是由类 Rayleigh-Benard对流和强迫对流两个区域构成 ,两个区域通过能量和质量交换相互影响 ,流动随着 Ra的增加从稳态发展为非稳态 ;采用频谱图分析的方法对数值解的不稳定性进行定性分析 ,结果显示随着 Ra的增大 ,数值解经历了从稳定解到分贫的周期性不稳定和准周期不稳定的发展过程。离心浮升力引起的类 Rayleigh-Benard对流是造成流动从稳定到不稳定发展的重要原因 。

Numerical experiments were performed to investigate the instability of flow and heat transfer in a heated rotating cavity with cool air axial throughflow. Numerical test showed that, for a fixed inlet Reynolds number, there always exists a critical Rayleigh number Ra c, for Ra<Ra c the flow is stable, and for Ra>Ra c, the flow becomes unstable. Among all the forces in momentum equations, the buoyancy induced by centrifugal force is the main cause of the instability. The cavity may be divided into two zones-the Rayleigh\|Benard\|like convection zone occupying the upper cavity and the forced convection zone down under. The two zones interact with each other via the exchange of mass, momentum and energy. The Coriolis force, on the other hand, made the instability take place earlier and the unstable flow field more complex, although this force alone could not lead to instability. Frequency spectra method was used to analyze the pattern of flow instability and it was shown that the numerical solution underwent the path of stable to periodically instable, through bifurcation, to quasi\|periodically instable and finally to a complete chaos with the increase of the Rayleigh number.