水库漂流性鱼卵漂移扩散机理研究

The operation of the reservoir has changed the drift and spread law of pelagic eggs, which has important influence on the safe hatchery of the seedling, the accuracy of the early fish resource estimation, the locality of the fish spawning, the maintenance of the fish community structure and the ecological dispatching effect. At present, the mechanism of drift and spread of pelagic eggs is still in the initial stage, which is incompatible with the actual urgent demand. Based on the characteristics of embryonic development of pelagic eggs, this paper analyzes the mechanism and effect of typical pelagic eggs drift and diffusion by means of mechanism analysis, indoor experiment and numerical simulation, and discusses the characteristics of drift resistance and critical flow velocity, and establishes particle tracing model of pelagic eggs.The drift of the pelagic eggs are tested on straight and the curve of the channel, and the natural drift, sedimentation, suspension movement and fish density spread characteristics of the eggs are observed and analyzed at different developmental stages. The mechanism of water drift and diffusion of the whole process of pelagic eggs embryo development are analyzed. Based on the relationship between the development of the pelagic eggs and their particle size, density and water temperature, the mathematical model of the space and temporal evolution of the pelagic eggs water drift and the thermal stratification effect is established. The trajectories of the pelagic eggs, the drift density, the drift efficiency, and its relationship with the internal response of reservoir operation and dispatching are simulated, also the adaptability of pelagic eggs to dispatching is discussed. The research results have significant scientific significance, economic value and ecological and environmental benefits.

水库运行深刻改变了库区漂流性鱼卵漂移扩散规律，对卵苗的安全孵化、早期资源量估算精度、鱼类产卵场定位、鱼类群落结构维持、生态调度效果等产生重要影响。目前鱼卵漂移扩散机理仍处于起步阶段，与实际迫切需求不相适应。本研究根据漂流性鱼卵胚胎发育不同阶段特性，采用机理分析、室内试验、数值模拟等手段，解析典型鱼卵飘移扩散受力机制及作用效应，探讨鱼卵漂流阻力特性和临界流速阈值，建立鱼卵颗粒飘流运动模型。开展鱼卵漂移直道和弯道水槽试验，观测分析不同发育阶段鱼卵自然漂移、沉降、悬浮运动规律和鱼卵密度扩散特性，解析鱼卵胚胎发育全过程的水力漂移扩散机理。结合鱼卵发育与其粒径、密度、水温等关系，建立耦合水库水温迟滞效应和分层效应的鱼卵漂流时空演化数学模型，模拟分析鱼卵运动轨迹、漂流密度、有效漂程、漂时及其与水库运行调度的内在响应关系，探讨鱼卵漂流对调度的适应性。研究成果具有重大的科学意义、经济价值和生态环境效益。

水库运行深刻改变了库区漂流性鱼卵漂移扩散规律，对卵苗的安全孵化、早期资源量估算精度、鱼类产卵场定位、鱼类群落结构维持、生态调度效果等产生重要影响。目前鱼卵漂移扩散机理仍处于起步阶段。本研究采用机理分析、室内试验、数值模拟等手段，取得系列重要成果：1）研究了漂流性鱼卵不同时期胚胎发育特征，测量了鱼卵质量、直径和相对密度，获取了鱼卵发育的动态物理特性参数。2）解析了典型漂流性鱼卵飘移扩散受力机制及作用效应。结果表明：仅考虑拖曳力和鱼卵有效重力，鱼卵垂向速度随流速增大趋于定值；鱼卵比重越大，鱼卵沉速越大；相同比重下鱼卵粒径越大，鱼卵沉速越大，近似为幂函数关系；鱼卵比重越小，鱼卵沉速曲线斜率越大；鱼卵速度与水流速度的差值随着时间的推移具有渐近趋势。3）探讨了鱼卵漂流阻力特性和临界流速阈值。鱼卵静水沉降距离与沉降时间基本呈线性关系，静水沉速随鱼卵径增大而减小，建立了静水沉降阻力系数与雷诺数关系，推导了静水沉速公式。动水沉降试验表明：鱼卵悬浮状态与流速呈显著正线性关系，建立了鱼卵动水沉速公式，其漂流临界流速较大程度维持在0.30 m/s左右。4）建立了考虑重力及其他体力、粘滞力、拖曳力等作用效应的鱼卵颗粒飘流三维运动模型。模拟结果表明：随着漂流流速等量增加，沉底点后移距离增量经历了由大变小，随后又逐步增大的过程。随着拖曳系数的增加，沉底点位置后移基本线性化发展。在相同拖曳系数条件下，漂流流速越大，沉底点位置也越远。5）开展了鱼卵弯道漂流特性研究。弯道前半段横向扩散强度显著高于后半段；在相同弯道长度条件下，弯道转角越大，鱼卵沿程横向扩散强度越高；弯道沿程横向扩散强度和弯道入口横向扩散宽度呈显著的幂函数关系。6）探讨了改善三峡库区鱼卵生境条件的生态调度建议。结果表明：丰水期基本可维持在0.3m/s以上，有利于鱼卵漂流孵化；平水期和枯水期较难满足鱼卵漂流孵化条件，建议增加上游水库下泄流量，改善鱼卵漂流生境。