植被作用下过饱和总溶解气体输移释放规律研究

The presence of elevated total dissolved gas (TDG) downstream of a high-dam spillway may result in an increased incidence of gas bubble disease in fish. Vegetated floodplains are common in the downstream reaches with TDG supersaturation discharges. The submerged vegetation not only obviously affects the flow structure and the hydrodynamic characteristics of the flow, but also strongly influences the transportation and dissipation of supersaturated TDG. By employing comprehensive laboratory experiments, field observations and numerical simulation, hydrodynamic-based study about the mechanics of TDG transportation and dissipation with vegetation effects will be explored. The relation between TDG dissipation and the micro-hydrodynamic structure will be investigated. The determination method for dissipation coefficient of TDG in the vegetated flow will be proposed, and thereafter, an unsteady three-dimensional model will be developed for the prediction of the TDG transportation and dissipation process with vegetation effects. Finally, considering the accumulation effect of vegetation on TDG dissipation, the mitigation measures of TDG negative effects will be studied. The proposal extends the research about supersaturated TDG from the simple-flow without vegetation to the comprehensive flow with resistance of vegetation. It is of great importance in improving the prediction of the dissipation process of supersaturated TDG, and accelerating the study on mitigation measures of TDG negative effects. Also it is of theoretical value and practical significance in developing eco-environmentally friendly hydropower projects.

高坝泄水会产生总溶解气体（TDG）过饱和现象并可能导致鱼类患气泡病甚至死亡。TDG过饱和的泄洪水流在下游河道的输移过程中常伴随河滩地植被被淹没现象。淹没滩地上的植被不仅对水流结构及水动力学特性产生重要影响，还对过饱和TDG的输移和释放造成显著影响。本研究综合运用机理试验、原型观测及数值模拟等手段，从过饱和TDG释放与植被水流水动力学特性的关系入手，研究植被作用下过饱和TDG释放系数，揭示植被作用及微观水力结构对过饱和TDG输移释放的影响机理，建立植被作用下过饱和TDG输移释放数学模型和预测方法，基于滩地植被对过饱和TDG的促进作用探求过饱和TDG不利影响的减缓措施。本项目的研究将以往不考虑植被作用的简单水流过饱和TDG输移释放研究拓展到植被作用下复杂水流中，对于提高过饱和TDG预测水平，促进TDG过饱和不利影响的减缓措施研究，建设环境友好型水利工程具有重要的理论价值和现实意义。

高坝泄水会产生总溶解气体（TDG）过饱和并可能导致鱼类患气泡病甚至死亡。TDG过饱和的泄洪水流在下游河道的输移过程中常伴随河滩地植被被淹没现象。淹没滩地上的植被不仅对水流结构及水动力学特性产生重要影响，还对过饱和TDG的输移和释放造成显著影响。本研究综合运用机理试验、数值模拟和理论分析等手段，从过饱和TDG释放与植被水流水动力学特性的关系入手，研究过饱和TDG输移释放特性。基于静置水体和流动水体中植被对过饱和TDG释放过程影响的试验成果，建立了单位面积壁面在单位时间内对过饱和TDG吸附通量计算公式，提出了表征壁面对过饱和TDG吸附快慢的参数——吸附速率。它主要受材质影响，表面越粗糙吸附速率越大；通过对过饱和TDG释放过程的分析，将植被作用下过饱和TDG的释放过程概化为三个部分，为自由水面处传质、水体内部释放和壁面处吸附，同时针对植被作用下水流复杂的三维特征，建立了植被作用下的三维两相流水动力学模型，模型计算的水动力学和过饱和TDG释放结果均得到动水试验成果的验证；基于试验结果分析识别出对水体内部释放系数kin具有重要影响的参数，为植被密度、佛劳德数和水深，并回归建立水体内部释放系数的估算公式；根据数值模拟计算成果，对植被水流中的立柱附近的过饱和TDG特性以及过饱和TDG在纵向、横向上的分布和变化规律开展分析。研究成果形成的国家发明专利已获授权，本项目研究对于提高过饱和TDG预测水平，促进TDG过饱和不利影响的减缓措施研究，建设环境友好型水利工程具有重要的理论价值和现实意义。