长方体腔内关于密度极值温度对称加热-冷却时冷水瑞利-贝纳德对流稳定性

NUMERICAL INVESTIGATION ON FLOW STABILITY OF RAYLEIGH-BéNARD CONVECTION OF COLD WATER IN A RECTANGULAR CAVITY COOLED AND HEATED SYMMETRICALLY RELATIVE TO THE TEMPERATURE OF DENSITY MAXIMUM

为了解具有密度极值流体瑞利-贝纳德对流特有现象和规律,利用有限容积法对长方体腔内关于密度极值温度对称加热-冷却时冷水瑞利-贝纳德对流的分岔特性进行了三维数值模拟,得到了不同条件下的对流结构型态及其分岔序列,分析了密度极值特性、瑞利数、热边界条件以及宽深比对瑞利-贝纳德对流的影响.结果表明:具有密度极值冷水瑞利-贝纳德对流系统较常规流体更加稳定,且流动型态及其分岔序列更加复杂;相同瑞利数下多种流型可以稳定共存,各流型在相互转变中存在滞后现象;随着宽深比的增加,流动更易失稳,对流传热能力增强;系统在导热侧壁时比绝热侧壁更加稳定,对流传热能力有所减弱;基于计算结果,采用线性回归方法,得到了热壁传热关联式.

In order to understand the special phenomena and laws of Rayleigh-Benard convection of fluids with density extremum, a series of three-dimensional numerical simulations on Rayleigh-Benard convection of cold water in a rect- angular cavity when its horizontal walls were cooled and heated symmetrically relative to the temperature of the density extremum by using finite volume method is carried out. Flow structures and their bifurcation series are obtained, and the effects of the density extremum character, the Rayleigh number, the thermal boundary condition and the aspect ratio on Rayleigh-Benard convection are discussed. The results demonstrate that the system of Rayleigh-Benard convection of cold water with density extremum is much more stable than that of common fluid, and the flow structures and their bifurcation series are much more complex. Multiple flow patterns can coexist at a constant Rayleigh number and hystere- sis phenomenon is observed in the flow evolution. The system loses its stability more easily and the heat transfer ability enhances with the increase of the aspect ratio. The system for conducting sidewalls is much more stable than that for insulating sidewalls and the heat transfer ability weakens. Furthermore, heat transfer correlations are proposed according to the multiple linear regression.