高紊态高溶解度水体水气质传模型相界面面积测算机理研究

The total dissolved gas supersaturation phenomenon under the Columbia River system was found 45 years ago. With the investigations and experiments to the supersaturation phenomenon, which is governed by the gas transfer law is increasingly clear. Furthermore, the accurate predict to the degree of supersaturation is longing. In predict, the interface area is given by generalization, hypothesis or pure-empirical. The predict result is accurate in one object and inaccurate in the others. The reason is the flow dynamics complex in dissipator, with the intense mixing and variable pressure condition the interface area between phrases is elusive. Especially the mass transfer bubbles distribution state and movement characters do not exist from experiment, which obstructs the theory development of gas transfer and the reasonable predict of supersaturation. This study will use concept model, physics model and gauge in prototype to study the bubbles size distribution and movement regular pattern in dissipator, provides the theoretical support and reliable method to compute the phase interface area of gas transfer model in supersaturation water in dissipation basin of high dam.

自从哥伦比亚河水利工程下游总溶解气体过饱和现象发现迄今已经近四十五年。随着对气体过饱和现象的观测和试验，其水气两相流中的质量传输机理日益清晰。进而渴望对气体过饱和程度进行准确的预测。但是在预测过程中，质传面积多通过概化、假设和经验公式获得，造成预测结果在具体工程中较为准确，应用到其他工程时往往不能获得满意结果。究其原因是由于消能工中的水动力特征复杂，在剧烈掺混及环境压强改变条件下，水气两相流的气液交界面面积变化难以捉摸。尤其是质传气泡在消能工中的基本分布和行为特征几乎完全无实测或验证数据，对水气质传理论的发展和气体过饱和的合理预测造成了严重阻碍。本研究拟通过概念模型，物理模型和原型观测探索水动力特征与消能工中水体气泡大小、分布和运动规律的关系，为高紊态高溶解度水体水气质传模型交界面面积计算提供可靠方法和理论支持。

在气体过饱和程度预测过程中，质传面积多通过概化、假设和经验公式获得，但由于消能工中的水动力特征复杂，水气两相流的气液交界面面积变化难以捉摸，对水气质传理论的发展和气体过饱和的准确预测造成了严重阻碍。本研究采用概化模型、原型观测和数值模拟的综合手段，建立高坝挑射流挟气量与水动力特征间影响关系，揭示高紊态水气掺混区气泡特性，分析泄洪消能TDG特性及成因，提出单气泡水气质传影响因素。研究表明，挟气速度与泄量、孔口水头呈正相关关系，与泄流高度呈抛物线关系；高速射流入水消能，空泡率沿程降低，气泡大小呈先大幅减小后小幅增大的趋势；水流紊动剧烈，气泡与水体接触面积、质传系数增大，是消能工下游高TDG的主要原因；气泡质传效率与气泡深度、气泡大小、溶解氧浓度密切相关，气泡越深、越小、溶解氧浓度越低，气泡质传效率越高。研究成果可为总溶解气体预测模型提供理论基础，也为高紊态高溶解度水体水气质传模型交界面面积计算提供可靠方法和理论支持。