With the aggravation of eutrophication in lakes and reservoirs, the frequent occurrence of algal blooms has become a significant aquatic ecological challenge. To reveal the regulatory mechanisms of hydrodynamic conditions on the growth of Cyclotella, a CFD-based hydrodynamic simulation was carried out to investigate the flow characteristics and its influence on the growth of Cyclotella (centric diatom) in an annular tank reactor. This study combined indoor annular flume experiments with three-dimensional computational fluid dynamics (CFD) numerical simulations. By setting different stirring speed gradients, this study systematically investigated the growth dynamics, nutrient metabolism characteristics, and flow field response patterns of Cyclotella under multi-gradient hydrodynamic conditions. Experimental and simulation data confirm that hydrodynamics exert a typical dual regulatory effect on the growth and metabolism of Cyclotella: moderate flow circulation significantly promotes algal cell proliferation and nitrogen/phosphorus assimilation, whereas excessive mechanical shear and intense turbulent dissipation induce severe physiological stress, leading to a substantial inhibition of biomass and metabolic activity. Based on a dual-coupling analysis of the macroscopic velocity field and the microscopic turbulent dissipation field, this study defines the suitable hydrodynamic niche for Cyclotella. The optimal growth range was identified as a mean flow velocity of 0.30-0.40 m/s, with a mean turbulent dissipation rate below 6.89 & times; 10-3 m2/s3. Within this optimal range, the water flow acts as a "material transporter" by thinning the diffusive boundary layer on the cell surface and enhancing vertical suspension; however, high-intensity turbulence exceeding the critical threshold transforms into a "structural destroyer," causing mechanical damage to the algal cells. This mechanism elucidates the physical essence of water flow regulating microalgal growth from the perspective of multiphase fluid mechanics, providing important quantitative indicators and a theoretical basis for the early warning of diatom blooms and hydraulics-based ecological prevention in natural water bodies.

To investigate the flow characteristics of a novel dual-slot overflow channel, a research approach integrating physical experiments and numerical simulations was adopted. A three-dimensional model of the overflow channel was developed, employing the RNG k-ε turbulence model and the VOF two-phase flow model to optimize the numerical simulation of the high-low dual-slot flow field. Physical experiments were conducted to verify and analyze the hydraulic characteristics of the high-low overflow channel, including the longitudinal water surface profile and flow patterns. The numerical simulation results aligned well with the physical model test results. By analyzing the flow field of the dual-slot counterflow spillway, the flow characteristics at both the spillway and outlet sections were identified. This study focused on the water surface profile along the spillway, the pressure distribution, and the counterflow characteristics of the protruding water tongue, and explored optimization strategies for the WES surface and spillway design. Physical model tests were conducted on the final optimized design, yielding good agreement between the theoretical predictions and experimental results, thereby confirming the feasibility of the energy dissipation methods for both high and low spillways. The research outcomes offer valuable references for related engineering applications.

The release of supersaturated total dissolved gas (STDG) from dams has been linked to the development of gas bubble disease, which can ultimately result in the death of fish. In order to minimize the impact of STDG on aquatic ecology, the effect of aeration on mass transfer at the air-liquid interface is taken into account. This paper selects four commonly used aerators to carry out indoor aeration tower experiments under different aeration conditions (aeration aperture, aeration water depth, and aeration volume), exploring aerators that can efficiently promote STDG release. The results indicated that the diaphragm aerator was found to have the greatest effect on STDG release, followed by corundum and spin mix aerator. In contrast, a pinhole aerator was found to have the least beneficial impact on STDG release. The increase in the release coefficient for the diaphragm aerator in comparison to the pinhole aerator is 32%. A prediction model for the aeration system was developed based on the mass transfer mechanism at the gas-liquid interface. The parameters in the model were determined using experimental data, which effectively improved the model's prediction accuracy. The findings of this study may serve as a reference point for the selection of the most suitable aerator in the actual engineering of STDG mitigation by aeration technology. [GRAPHICS]

In order to promote the application of aeration technology in alleviating the influence of supersaturated dissolved oxygen(DO),the release tests of supersaturated DO under non-aeration and aeration conditions were carried out.The impact of aeration on the dissipation process of supersaturated DO and its related laws were studied,and the release process and release coefficient of supersaturated DO under different aeration conditions were analyzed.The experimental results show that the time required for DO saturation to dissipate from about 170％to about 105％under aeration conditions is less than 11 min,while the time required under no aeration conditions is at least 240 min,indicating that aeration can significantly promote the dissipation of supersaturated DO.The supersaturated DO release coefficient increases with the increase of aeration rate,decreases with the increase of aeration depth,and shows a strong negative correlation power function relationship with aeration aperture.According to the release law of supersaturated DO,the quantitative relationship between release coefficient and aeration conditions was established.The quantitative relationship between release coefficient and aeration conditions,model size and fluid parameters was established by dimensional analysis.By comprehensively analyzing the two quantitative relationships,it can be concluded that the latter has smaller root mean square error and average absolute error,higher correlation coefficients,and easier parameter acquisition,which shows that the latter is more applicable in practice.

Supersaturation of total dissolved gas (TDG) is a common occurrence in high dams during the spill process, which can lead to fish bubble disease and threaten aquatic organisms. As a result, many scholars have taken a keen interest in this issue. Research into the gas-liquid mass transfer mechanism has improved the accuracy of TDG prediction models. This article investigates the factors affecting TDG dissipation through laboratory experiments. Especially, the mass transfer coefficient across the bubble interface based on the slip penetration model was calibrated, and the coaxial bubble coalescence added to the coefficient was studied. The results show that the aeration rate has the most significant impact, followed by water depth, and then the aeration aperture. The TDG dissipation rate increases with the parameter beta, and the parameter of 0.35 shows the highest correlation with the experimental data. Furthermore, the concentration change rate after coalescence is lower than before, suggesting that aggregation negatively impacts mass transfer. This study improves TDG concentration prediction accuracy and proposes measures for mitigating supersaturation to avoid fish bubble disease.

Supersaturation of total dissolved gas (TDG) is mainly produced by high dam discharge, excess oxygen production by plant photosynthesis, and a sharp increase in water temperature, which may directly lead to fish and aquatic organisms suffering from “gas bubble disease” (GBD) or death. Aeration was one of the methods used to solve the dissipation of supersaturated TDG. In this paper, aeration had an obvious promotion effect on the dissipation of supersaturated TDG. For the calculation and analysis of supersaturated TDG dissipation coefficient, the aeration rate was proportional to TDG dissipation coefficient and had a promoting effect on it, while the aeration depth and aeration aperture were inversely proportional to TDG dissipation coefficient and played an inhibitory effect on it. The supersaturated TDG dissipation coefficient was affected by a factor of KTDG,Q> KTDG,D> KTDG,H. A quantitative relationship between the supersaturated TDG dissipation coefficient and aeration rate, aeration depth, and aeration aperture was obtained, respectively, as well as important expressions with comprehensive effect factors; their margins of error average within 10%. This research method has an important guiding significance for improving the living environment of fish and other aquatic organisms, alleviating the adverse effects of supersaturated TDG.

过饱和总溶解气体(TDG)主要由高坝溢洪道泄流、植物光合作用产氧过剩和水温剧增等方式引起,这可能直接导致鱼类和水生生物患有"气泡病"(GBD)甚至死亡.为探索减缓过饱和TDG不利影响的措施,采用两种类型的漩混曝气盘对过饱和TDG释放进行试验.结果表明,在不同曝气条件下,漩混曝气方式对过饱和TDG释放有明显的促进作用,其作用效果略强于针孔曝气方式,且曝气速率对过饱和TDG传质系数影响最大,曝气深度次之,曝气直径最小,并获得了过饱和TDG传质系数与曝气速率、曝气直径和曝气深度的关系式,且其误差平均在士6.25％以内.研究结果为减缓过饱和TDG的不利影响提供了数据基础.

研究发现大坝泄流引起的下游总溶解气体(total dissolved gas,TDG)过饱和问题会对鱼类等水生生物的生存、繁衍产生负面影响.解决这一问题的重要途径之一是从源头上阻碍过饱和TDG的生成,降低消力池中TDG浓度,因此了解过饱和TDG的生成机理将为制定TDG消减措施提供可靠的理论依据和参考价值.基于此,文章重点分析总结了国内外学者对大坝下游过饱和TDG生成过程的研究,包括相关概述、影响因子、预测模型等内容,旨在为进一步开展研究提供参考.

Supersaturation of dissolved oxygen (DO) and total dissolved gas (TDG) is generated by high dam discharge, excess oxygen production in photosynthesis and increasing temperature in water, which may directly lead to fish suffering from "gas bubble disease' or death. In this paper, under a series of experimental aeration conditions in standing water, it was concluded that aeration had a positively promoting effect on releases of supersaturated DO and TDG, while aeration aperture and aeration depth had inhibitory effects on them. For single factor analysis, aeration had the greatest effect on the release of DO and TDG, the second effect on DO was that of aeration depth and the smallest effect was that of aeration aperture, but the second effect on TDG was that of aeration aperture and the smallest effect was that of aeration depth. Most importantly, the release coefficient of DO was greater than that of TDG, and a quantitative relationship between the release coefficient of DO and TDG and aeration conditions, respectively, was established. An exponential function relationship of the release coefficients of DO and TDG was also established. The results of the research have important guiding significance and theoretical value for reducing the harm caused by supersaturated DO and TDG.

An Interconnected River System Network (IRSN) project could change the drainage pattern and influence the river's ecological health. However, the relevant research is still in a preliminary stage and needs to have a supplement. Considering environmental and ecological characteristics of the karst area, this paper analyzed the relationship between IRSN projects and environmental indicators, and proposed a multi-layer indicator system that has three first-class indicators (water environment, river–lake organism, connectivity) and 15 second-class indicators for assessment of the ecosystem. The weight of each level of indicators' can be determined using the analytic hierarchy process (AHP), and the change rate of indicators critical value is normalized, then five threshold levels are established within the range of 0–1. Refer to the established response mechanism and threshold level of the karst basin, The Wangerhe River project taken as an example can well reflect the IRSN status through this method. These results can provide scientific support for constructing an evaluation index in other karst areas.

总溶解气体(Total Dissolved Gas,简称"TDG")过饱和可能直接导致鱼类和水中生物患有"气泡病"甚至死亡.文章为解决该问题开展研究.实验结果表明,在紊动的系列条件下,紊动能促进过饱和总溶解气体的释放,转速和温度对过饱和TDG释放起促进作用,而水深对其起抑制作用.研究还获得过饱和TDG释放系数(释放速率)分别与水深、转速和温度的关系表达式,以及紊动因素对过饱和TDG的影响大小为KTDG,n>KTDG,T>KTDG,H.该研究成果是一种减缓过饱和TDG危害的方法,为探讨减缓过饱和TDG不利影响的措施提供科学指导和依据.

随着大坝的泄流,河流出现了严重的总溶解气体过饱和问题.为缓解过饱和TDG对下游鱼类造成的危害,可尝试在珍惜鱼类保护区附近进行局部曝气的方式降低过饱和TDG浓度.通过室内机理实验,设计曝气盘的4种不同布置方式,探究不同的曝气孔径以及曝气量对过饱和TDG释放速率的影响.结果表明:不同曝气孔布置条件下过饱和TDG的释放速率,呈现十字型形曝气>口字形曝气>中心集中式>角落集中式,即在一定试验情况下,曝气孔的分散程度越均匀,释放速率越高.

以给排水专业的水处理工程实验教学课程为例,介绍了该专业实验课程开设、 教材选择、 实验条件以及教学内容更新情况,阐述了在新工科背景下,课程培养方案调整后的教学思路和教学方法,展示了学生参与教师科研的两种途径,并建立多层次教学评价机制.实践表明,通过改革教学模式,有助于培养学生独立分析和逻辑判断能力,提升高校教学质量.

以镉超富集植物孔雀草(Tagets patula L.)为试验材料,采用土培试验,研究叶面喷施不同浓度水杨酸(SA,0.1、0.2、0.3、0.4 mmol·L-1)对镉胁迫下孔雀草过氧化氢酶、过氧化物酶、超氧化物歧化酶活性,丙二醛、可溶性蛋白质、脯氨酸、叶绿素含量的影响,以期为孔雀草应用于重金属污染土壤修复提供参考依据.结果表明:适当浓度的外源SA(0.1～0.3 mmol·L-1)增强了孔雀草的抗逆性,但高浓度SA(0.4 mmol·L-1)对孔雀草植株缓解作用明显降低.其中0.1 mmol·L-1 SA处理能显著提高镉胁迫下孔雀草叶片叶绿素含量;0.3 mmol·L-1 SA处理能显著提高镉胁迫下孔雀草叶片过氧化氢酶、过氧化物酶、超氧化物歧化酶活性,可溶性蛋白质、脯氨酸的含量;0.2 mmol·L-1 SA处理能显著降低孔雀草叶片丙二醛含量;0.4 mmol·L-1 SA处理对孔雀草叶片各生理指标缓解作用明显降低.

The cascade development of water resource will lead to cumulative effect of supersaturated total dissolved gas (TDG) on the ecological environment, which will cause lethal disease to fish. The TDG dissipates slowly in deep reservoir areas and if supersaturated TDG can't recover through the spillway then it will lead to continuous accumulation in the stilling basin. In order to investigate the cumulative effect of supersaturated TDG of hydropower cascades, a validated TDG numerical model with the VOF method and DES model was used to simulate a spillway discharge of Tongjiezi dam with supersaturated TDG and 100% TDG inflow. In this model, bubble size change is calculated by bubble number density equation and TDG is simulated by transport equation considering the gas-liquid mass transfer. Comparing with the TDG 100% inflow case, it indicated forebay TDG level caused by the upstream dams should be considered and involved in the downstream TDG evaluation. This paper also proposed an engineering measure with baffle blocks in the spillway which can reduce entrained bubble mass and TDG saturation level at the entry point than the case without blocks. It shows baffle blocks in the spillway can effectively reduce the cumulative effect of supersaturated TDG. It is a critical step for the mitigation of accumulation of supersaturated TDG through the spillway and the results provide reference about mitigation measure of supersaturated TDG for hydropower cascades.

Aerated flow characterized by complex mass transfer processes with multiple hydraulic properties is a common enviro-hydraulics phenomenon, which have a variety of profound effects on aquatic ecosystems and the environment. Accurate prediction of the mass transfer process between air and water is crucial to manage the water ecosystem. In this research, an improved two-phase mass transfer smoothed particle hydrodynamics (ITMT-SPH) model is developed with considering the inherent hydrodynamic equations and transport equations to investigate multiple key factors that have ecological implications such as DO (dissolved oxygen) concentration and TDG (total dissolved gas) level. The established model can eliminate the effects of phase separation and non-physical voids for conventional SPH models, which performs better than conventional grid-based methods in terms of prediction accuracy of hydraulic calculation. In addition, to improve the prediction accuracy of mass transfer calculation, experimental and observed field data from a physical model and a practical project are used to calibrate the source parameter of transport equations. Then, a physical model of Songta Hydropower Station (1:80) is established to simulate DO concentration. At the same time, the practical project of Tongjiezi Hydropower Station is used to explore dynamics of TDG level. Simulation results show that ITMT-SPH can simulate ecological indicators of the aerated flow well. The maximum relative error of DO deficit recovery rate between simulation and experiment is 7.8% downstream of dam of Songta physical model. The predicted result of TDG level downstream of Second Dam is 130–148% for Tongjiezi Project, which is close to the monitoring result (138%). This work provides an important theoretical and technical support for the application of ITMT-SPH model to accurately simulate ecological indicators in the ecosystem management.

The total dissolved gas (TDG) supersaturation observed in a spillway that flows downstream various hydraulic structures has long been recognized as having a negative environmental effect on fish and aquatic organisms. This paper focuses on learning the mass transfer of supersaturation total dissolved gas downstream and the rule of mass transfer between air-water interfaces. Besides, the three main coefficients of mass transfer are concluded: the surface mass transfer coefficient, the bubble interface mass transfer coefficient, and the dissipation coefficient and relevant transport process model. These can provide a foundation to analyze the supersaturation of high dam in near future.

As an important water control strategy in the 21st century, interconnected river system network has been widely implemented in all parts of China. However, the possible ecological response mechanism which can be decided by the structure of rivers and the river-lake connectivity is still in the exploratory stage at present, especially in karst areas where the ecosystem is particularly fragile. Taking the Huangguoshu Waterfall-Wangerhe reservoir connection engineering in Dabang River Basin of Guizhou Province as an example, this paper collects the basic data of hydrometeorology, vegetation coverage and river water quality in the Dabang River Basin in the past 20 years, and study and analysis the connectivity of water system and the ecological factors based on GIS which include meteorological, terrestrial habitat and water environment before and after the completion of the Link Project. The results show that the implementation of the project not only changes the connectivity pattern of river and lake systems, but also has a significant impact on the hydrometeorology, terrestrial habitat and water environment. The increase of connectivity leads to the decrease of regional rainfall, evaporation and temperature year by year, while the vegetation coverage and water temperature show an annual upward trend. In addition, the water quality of the receiving area is better after the implementation of the river-lake link project, which does not bring water pollution risk to the receiving area.

我国现阶段的人才培养遇到了巨大的问题与挑战,作为整个教育系统的最顶层也是最后一个环节的高校,面临全社会的关注以及国家持续发展的急切需求,必须做出改变,深化教育改革.本文阐述了高校现阶段人才培养所存在的普遍问题,分析了在人才培养过程中出现的误区与盲区,提出了具体的教育教学完善的方式方法.研究高校教学改革,要求的是研究改革和教育模式的双重改革目标,综合考虑这些因素的变化,强化其过程管理.本文以就业和社会需求为导向,从加强教学改革项目过程管理的角度,对如何提高教学改革项目研究质量进行初步探讨.

The large deformations associated with air and water interactions are critical factors that affect the hydrodynamic characteristics of hydraulic structures. As a type of Lagrange meshless particle method, smoothed particle hydrodynamics (SPH) has been shown to have many advantages when modeling the interface flow and tracing the free surface because the particles inherit the velocity, mass, and density properties. Significant theoretical and numerical studies have been performed recently in this area. In the present study, a two-phase SPH framework was developed based on these previous studies and we explored its capacity to capture the main features of large density ratio aerated flows. The cohesive pressure was included only in the momentum equation of the air phase for additional amendments to ensure the stability and accuracy of the two-phase SPH model. Three case studies were performed to test the performance of the two-phase SPH model. A convergence study demonstrated the need to balance the CPU time consumption and the real-time requirements. A dam-break simulation based on pressure variation in the air pocket showed the superior analytical performance of the two-phase model compared with the single-phase model. The results of a hydraulic jump simulation were compared with the theoretical results in order to understand the collision between the solid and liquid using the SPH method more clearly. Thus, the consistency between the simulation and the theoretical and experimental results demonstrated the feasibility and stability of the two-phase SPH framework.