瞬变外力场作用下汽泡行为对并行矩形窄通道流动失稳起始点的触发机制研究

Existing for parallel rectangular narrow channel flow instability research on transient force field condition mainly from the perspective of macro analysis of the thermal parameters and the motion parameters on the flow instability types and boundary, while for the mechanism of the onset of the flow instability mechanism on the parallel rectangular narrow channel research is less. And on the condition of transient force field bubble dynamics research mainly focus on bubble growth, departure, movement, coalescence and seldom take the bubble behavior and parallel rectangular narrow channel flow oscillation characteristics and the starting point for the flow instability associated conduct in-depth analysis of the development process.This topic will research the process of parallel rectangular channel flow instability associated with transient force field's influence on the bubble behaviour characteristics, by visual experiments, obtain bubble growth, movement, aggregation and movement, merger of large gas bubble behavior characteristics and the evolution of the phase distribution characteristics under the condition of force field in the parallel narrow rectangular channel ,and based on the micro-bubble behavior and gas-liquid interface fluctuation characteristics analysis of local heat transfer and pressure drop and flow instability characteristics, build based analysis model about the onset of the flow instability on the gas-liquid interface elastic wave instability, revealing the mechanism of the starting point for the gas-liquid two-phase flow instability mechanism on the parallel rectangular narrow channel, and provide technical support for core thermal safety design under the ocean condition.

现有对于瞬变外力场作用下并行矩形窄通道内流动不稳定性的研究主要从宏观角度分析热工参数和运动参数变化对流动失稳类型及边界的影响，对于通道间流动失稳起始点的触发机制研究较少；而瞬变外力场下汽泡动力学的研究重点着眼于汽泡生长、脱离、运动、聚合等汽泡行为特性的分析，很少将汽泡行为与并行矩形窄通道内流量脉动特性及流动失稳起始、发展过程相联系开展深入分析。本课题将瞬变外力场对汽泡行为的影响特性与并行矩形通道流量脉动过程相联系，通过可视化实验，获得瞬变外力场作用下并行窄矩形通道内汽泡生长、运动、聚合等汽泡行为、汽泡群运动行为和汽液相分布的演化特性，基于微观汽泡行为及汽液界面波动特征分析通道内局域压降、传热及流量脉动特性，构建基于汽液界面弹性波动的流动失稳分析模型，揭示瞬变外力场作用下汽泡行为对并行窄通道内汽液两相流动失稳起始现象的物理机制，为海洋运动条件下堆芯热工设计及安全分析提供技术支持。

海上核动力平台、浮动式核电站等在海洋环境中运行，受到风、浪、涌、流的影响，引起倾斜、摇摆、升潜等六自由度的瞬变运动，产生切向力、离心力等具有时空瞬变特点的瞬变外力场。瞬变外力场条件下堆芯通道流动沸腾换热及汽液两相流动不稳定性问题作为影响海上核动力舰船运行安全性的重要基础性问题逐步受到重视。流动失稳起始点作为界别流体稳定流动与脉动流动的起始点，是两相流动不稳定性研究的重要内容。.本课题将瞬变外力场对汽泡行为的影响特性与并行矩形通道流量脉动过程相联系，通过可视化实验，获得了瞬变外力场作用下并行窄矩形通道内汽泡及汽泡群运动行为和汽液相分布的演化特性，基于汽液界面波动特征分析通道内局域压降、传热及流量脉动特性，构建了基于汽液界面弹性波动的流动失稳分析模型，揭示了瞬变外力场作用下汽泡行为对并行窄通道内汽液两相流动失稳起始现象的物理机制，可为海洋运动条件下堆芯热工设计及安全分析提供技术支持。.本课题的主要研究内容和重要成果：（1）瞬变外力作用下并行矩形窄通道汽泡行为特性可视化实验。利用高速摄像仪可视化研究不工况条件下并行矩形窄通道流动不稳定起始点（OFI）发生时通道内汽泡及汽液界面演化过程，获得了汽泡生长、运动、聚合等实验数据，揭示了不同工况下汽泡动力学特性，获得了相分布演化规律，为后续汽泡相界面相变模型的开发提供实验依据。（2）瞬变外力作用下并行矩形通道窄相态分布演化特性与流动阻力特性研究。建立了汽泡生长、运动、聚合等相界面质量传递和能量传递过程的数学模型，采用VOF模型，对相态演化过程进行数值模拟，获得局部流场结构变化规律，分析了通道内局部压降、水动力学变化特性。（3）基于汽液界面弹性波动的并行窄通道流动失稳起始点（OFI）机理模型研究。分析了通道内局部压降、传热特性，构建了基于汽液界面弹性波动的流动失稳分析模型，揭示了瞬变外力场作用下汽泡行为对并行窄通道内汽液两相流动失稳起始现象（OFI）的物理机制。