【摘要】 本文对二维热泡的演化过程进行数值研究 ,所采用的湍流封闭模式为双方程 k-ε方程。数值结果表明 :无量纲时间大于 10后 ,流动与混合特性均符合自相似关系 ;热泡流场可分两区。混合区中示踪剂浓度场呈双峰肾形、湍流脉动强烈、旋流含一对涡眼 ,而外区示踪剂浓度为零、流动有势且符合偶极子模型 ;热泡流的附加等效质量系数近乎 1,自相似阶段热泡的宽高比约为1.4 5。所得热泡扩展率和混合率亦与实验数据相符更多还原

【Abstract】 The time evolution of a two dimensional line thermal, a turbulent flow produced by an initial element with significant buoyancy released in a large water body, was numerically studied using the two equation model for turbulence closure. The numerical results show that the thermal is characterized by a vortex pair flow and a kidney shaped concentration structure with double peak maxima; the computed flow details and scalar mixing characteristics can be described by self similar relations beyond a dimensionless time of around 10. There are two regions in the flow field of a line thermal: a mixing region where the concentration of tracer fluid is high and the flow is turbulent and rotational with a pair of vortex eyes, and an ambient region where the concentration is zero and the flow is a potential one well described by a model of doublet with strength very close to those given by early experimental and analytical studies. The added virtual mass coefficient of the thermal motion is found to be approximately 1. The aspect ratio for the kidney shaped thermal is found to be around 1.45 for self similar phase. The predicted thermal spreading and mixing rate compare well experimental data.更多还原