Laboratory Study Of Convection Mechanisms Of Mountain Climate

Mountain climate is one of regional climates in a small scale.The study of dynamics and heat and mass transpostation of mountain climate is of significance in fundmental research and of potential value of the regional climate prediction.The convective flows of mountain climate mainly involve in natural convection on the mountain surface and in the valley.In the thesis,experimental measurement,numerical simulation and theoretical analysis are used to study the development and transition of natural convection on the mountain and in the valley.Here,the mountain is assumed to an isothermal cone,and the valley to a (?)-shape-section cavity heated from the bottom and cooled from the top.The main results are as follows:(1)Shadowgraph visualization is used to observe the development of transient natural convection on the mountain model.The growth of the thermal boundary layer,the development and breakup of a starting plume,and the flapping of the plume stem are characterized.In comparison between three-dimensional numerical and experimental results,the heat and mass transportation of natural convection on the mountain model is quentified.(2)Dimensional analysis is addopted to determine governing parameters for natural convection on the moutain model(aspect ratio,Prandtl number and Rayleigh number).Scaling analysis is applied for the discussion of dynamics of transient natural convection;the curvature effect of the cone on natural convection on the mountain model is found and the scaling laws are obtained and validated by numerical or experimental results.(3)A new transition route is found for natural convection on the mountain model based on three dimensional numerical results.A set of bifurcations and flow structures are characterized and critical Rayleigh numbers are gained.Additionally,the heat and mass transportation in the transition is quantified.(4)Shadowgraph visualization,thermistor measurement and numerical simulation are used to investigate the development and transition of natural convection in the(?)-shape-section cavity.The development of transient natural convection is classified into the conduction stage,the transitional stage and the fully developed stage.The transition to chaos and flow structures are characterized.The heat and mass transportation is also quantified based on numerical results.The results in the thesis may make more understanding of dynamics and heat and mass transportation of natural convection of mountain climate and knowledge of fluid mechanics and heat transfer.Further,the results may also have the potential value for the regional climate prediction and be useful for the related practice in daily life and in industry.