大型水库热分层演变对水面热交换和垂向流速的响应研究

Thermal stratification may occur after storage of large reservoirs, which has a significant impact on the vertical distribution of nutrient salt and algae. Studying the evolution law of reservoir thermal stratification and its response relationship with the main influencing factors is of great significance for understanding the evolution of reservoir water quality and the process of ecological succession. This study focuses on the relationship between the thermal stratification characteristics of reservoirs, the heat flux of the water surface and vertical velocity. The Xiluodu Reservoir in Jinsha River is taken as the research object. The characteristics of the heat exchange at the water-air interface are studied. Considering the influence of the hydrodynamic pressure generated by the vertical turbulence of the water body on the water flow structure, a three-dimensional non-hydrostatic model is established to describe the vertical motion of stratified density flow. By simulating and analyzing the flow field and water temperature distribution of the reservoir under condition with heat exchange, the quantitative relationship between the characteristic parameters of thermal stratification and the surface heat flux and vertical velocity is established, so as to reveal the response mechanism of thermal stratification evolution of the reservoir to surface heat exchange and vertical velocity. This study can provide theoretical basis and technical support for the research on the analysis of reservoir thermal layer driving factors, reservoir nutrient salt and algae distribution in stratified environment.

大型水库蓄水后可能出现水温分层现象，对库区营养盐及藻类垂向分布有重大影响。研究水库热分层演变规律及其与主要影响因子之间的响应关系，对深入理解水库水质演变及生态演替过程有重要作用。本研究聚焦水库热分层特性与水面热通量和垂向流速之间的响应关系，拟以金沙江溪洛渡水库为研究对象，研究水库水-气界面热量交换特征，考虑水体垂向紊动产生的动水压强对水流结构的影响，建立能反映水库密度流垂向运动特性的三维非静压模型，模拟分析热交换条件下水库流场及水温分布规律，建立水库热分层特征参数与水面热通量和垂向流速的定量关系式，从而揭示水库热分层演变对水面热交换和垂向流速的响应机制。本研究可为水库热分层驱动因子分析、分层环境下水库营养盐及藻类分布规律研究提供理论依据和技术支持。

大型水库蓄水后可能出现水温分层现象，对库区营养盐及藻类垂向分布有重大影响。研究水库热分层演变规律及其与主要影响因子之间的响应关系，对深入理解水库水质演变及生态演替过程有重要作用。本研究聚焦水库热分层特性与水面热通量和垂向流速之间的响应关系，以金沙江下游溪洛渡-向家坝水库为研究对象，研究水库水-气界面热量交换特征，考虑水体垂向紊动产生的动水压强对水流结构的影响，建立能反映水库密度流垂向运动特性的三维非静压模型，模拟分析热交换条件下水库流场及水温分布规律，研究水库热分层特征参数与水面热通量和垂向流速的相关关系，从而揭示水库热分层演变对水面热交换和垂向流速的响应机制。主要结论如下：.（1）辨识了溪洛渡、向家坝水库水温分布的时空差异特征与水热交换特性，揭示了溪洛渡水温稳定增长、向家坝水温年内变幅逐年下降和入流水温坦化的演变趋势，查明了两库分层和混合的年内周期性转变规律（分层/混合持续时间比分别为2和0.5）。.（2）考虑水热耦合中非线性动水压力对水流和传热的影响，自主研发了基于非静压的水库热-流耦合模型，推导了控制方程，革新了数值方法和高效并行算法，解决了水库水热互作相耦合引起的强烈紊动、快速变化等诸多难题，可准确、高效地模拟水库水流、水温变化，平均精度比传统模型提高了7%，并节省了15-30%的计算时间。.（3）通过模拟揭示了外部热力和内部水动力驱动水库热分层演化的主导机制，阐明溪洛渡、向家坝水库运行的热累积影响。水气温差引起的对流散热和来流水温季节性变化浮力流是水库垂向换热的关键驱动因子，分层期间水库温跃层下移主要由上升浮力流对深层水体卷吸引起，水库下泄水温对水库调度水位变化存在3个月滞后响应。.本研究可为水库热分层驱动因子分析、分层环境下水库营养盐及藻类分布规律研究提供理论依据和技术支持。