竖缝与堰组合式鱼道水力特性数值模拟研究

堤坝等水利水电工程截断河流,鱼道能克服其阻碍作用,使鱼类顺利上溯洄游。采用RNG k-ε湍流模型对竖缝与堰组合式鱼道进行数值模拟,对其池室内流速以及紊动能情况进行分析研究。结果表明：该类型鱼道池室内部水力特性稳定,具有竖缝式鱼道和堰式鱼道共同优点,适宜于不同鱼类游过,能较好地适应鱼类上溯。     

大底坡下“H”型竖缝式鱼道池室水力特性数值研究

竖缝式鱼道作为一种生态补偿工程可有效缓解水利工程对鱼类洄游造成的不利影响,研究合理参数下竖缝式鱼道水力特性对建设经济有效型鱼道具有重要意义。基于物理模型试验与三维数值模拟相结合的方法,在大底坡1∶20情况下,系统分析了9种池室长宽比的“H”型竖缝式鱼道流场分布及水力特性。结果表明：不同池室长宽比下主流均呈“S”型,主流流速最大衰减率为46.4%~61.3%;池室长宽比L∶B=10∶8为大底坡“H”型竖缝式鱼道最佳池室长宽比,该方案池室内水流流态较好,主流向右侧弯曲且曲率最大,存在较大范围的低紊流区,且满足鱼道单位体积消能率的要求,有利于鱼类洄游上溯。研究结果可为大底坡下“H”型竖缝式鱼道参数选取与水力优化设计提供参考依据。     

鱼道紊流特性研究进展

鱼道内的紊流特性对于鱼类能否顺利上溯洄游至关重要。为了解鱼道内的紊流状态,综述了丹尼尔式、竖缝式、组合式、涵洞式等鱼道内紊流流速、紊动能、紊流强度、雷诺剪切应力以及漩涡等紊流特性的研究进展,分析不同鱼道内紊流的分布规律及特点,指出鱼道中的紊流强度、紊动能等均会对鱼类对栖息地的选择以及鱼类通行造成较大的影响。此外,目前国内对鱼道内漩涡紊流特性的研究较少,建议对其深入研究,以改善鱼道内水力条件,保证鱼道有效运行。     

长洲鱼道挡板结构优化研究

广西长洲鱼道是珠江口以上第一座大型水利工程,也是我国自主设计的第一座大型鱼道,为中华鲟等六种国家级保护鱼类的主要洄游通道,为典型的竖缝鱼道。以长洲鱼道为研究对象,以流体力学理论为基础,采用理论分析、试验研究及数值模拟相结合的方法,通过改变孔口尺寸对池室内流速分布的影响进行分析。结果表明在正常运行水位为3 m时,改变正方形孔口边长,对于鱼道内流场流速、水流结构均会产生较大影响;当孔口边长为1.5 m时,最适宜目标鱼类的洄游。研究结果为竖缝鱼道的设计提供一定参考依据。图9幅。     

同侧竖缝式鱼道结构优化数值模拟研究

鱼道是保证鱼类能顺利洄游的过鱼设施。通过竖缝相对宽度分别为0.05,0.10,0.15,0.30,底坡为10%的鱼道模型进行数值计算。采用可视化显示及数据分析的方法分析不同竖缝相对宽度、底坡条件下的同侧竖缝式鱼道的水流结构特征。通过模型模拟,分析水流沿水深方向的流速分布情况、主流区最大流速沿程分布及沿程衰减情况,以及在不同竖缝相对宽度和(或)不同流速情况下的紊动能分布情况。综合各物理量的分析,得出竖缝相对宽度b₀/B=0.15、底坡为10%时,水流在池室内能形成较好的适合鱼类洄游的流态:主流区水流横向扩散范围适中,主流区最大流速沿程均匀衰减,回流区面积较为对称,流速较小。     

同侧竖缝式鱼道水力特性的数值模拟

分别采用标准的k-ε模型和雷诺应力方程模型(RSM)对同侧竖缝式鱼道池室内的水流进行了三维数值模拟。对鱼道池室内的流场、雷诺剪切应力等相关水力要素进行了分析,并应用水工模型试验成果对2种紊流模型的结果进行了验证比较。结果表明：2种紊流模型均可模拟同侧竖缝式鱼道水流基本特性,但 RSM 模型流速场的计算结果与水工模型试验结果更为吻合。     

鹤岗市关门嘴子水库横隔板竖缝式鱼道设计研究

关门嘴子水库枢纽建成后,将阻隔鱼类洄游通道,修建鱼道保护鱼类十分必要。文章根据关门嘴子水库所在河段河道地形条件及鱼类洄游能力等因素选择横隔板竖缝式鱼道进行设计计算,通过分析梧桐河流域过鱼种类、过鱼季节、水库过鱼水位,选择合理鱼道设计参数进行结构设计。研究发现,选择适合的鱼道竖缝流速,对于鱼道长度有较大影响;为适应水库水位的变化,保证鱼类洄游,需要合理设置鱼道出口个数。     

不同侧垂直竖缝式鱼道水力特性试验研究

在山区峡谷中修建水利枢纽工程,能获得较大的发电效益,但同时也阻断了流域内洄游性鱼类的生态路线,对流域内鱼类生态造成较大的影响。本文以新疆北疆伊犁河流域内拦河枢纽工程为背景,采用不同侧垂直竖缝式鱼道进行水力特性实验研究,对不同工况下鱼道竖缝处流速和水深进行了研究分析,结果表明在不同水位工况下,鱼道内的流速保持在恒定状态下,满足鱼类洄游条件。     

竖缝式鱼道池室结构变化对水力特性的影响分析

竖缝鱼道的消能主要集中在竖缝处,竖缝束窄使水流形成漩涡,导致鱼道内流速过高,水流紊乱。为了改善竖缝式鱼道池室的水流特性,采用雷诺应力(RSM)模型对不同结构形式的同侧竖缝鱼道进行数值模拟。研究表明:在池室内正对竖缝下游布置圆柱型障碍物,竖缝处流速梯度减小,紊动能和雷诺剪切力均降低约20%～30%,这种池型的鱼道水力特性稳定,能满足更多鱼类的过坝。     

鱼道水力特性研究进展

综述竖缝式、池堰式和涵洞式、丹尼尔式及组合式鱼道水力特性的国内外研究进展;对比分析水流流态、流速场特征、流量与水深的关系、紊流特性及消能率等几方面对不同鱼道的水力特性的影响;得出了竖缝式鱼道中无量纲流量与相对水深之间呈线性关系的结论,列出了池堰式鱼道中流量与水深的关系式;指出鱼道中紊流的紊动能、紊流强度及紊流结构均会对鱼道水力特性、鱼类对栖息地的选择以及鱼类通行造成较大影响;展望鱼道未来研究重心会逐渐集中于鱼道内紊流特性及其数值模拟的研究,尤其是紊流结构的研究。此外,不同结构形式鱼道内水力条件对鱼类通行的影响及改善措施亦将成为未来研究热点之一。     

Physical modelling of pool and weir fishways with rock weirs

The flow characteristics of pool and weir fishways with rock weirs were studied through physical modelling. Detailed flow measurements were obtained using an acoustic Doppler velocimeter to understand how weir geometry, discharge, and bed slope affect flow patterns, velocity, turbulence kinetic energy, turbulence intensity, and Reynolds shear stresses in the fishway. The weir geometries used in this study are similar to those typically used for river restoration projects. The use of a V‐shaped rock weir was found to reduce the mean streamwise velocity in the pools by about 20% but more than double the maximum velocity magnitude. Two stage–discharge relationships were developed using the standard weir equation and a modified discharge coefficient to account for both flow over the weir and orifice flow through the base of the weir. The use of V‐shaped rock weirs has the potential to offer significant advantages in assisting multispecies fish migration. The results of this study can be applied to the hydrotechnical design of pool and weir fishways with rock weirs and for river restoration projects.     

Hydraulic and turbulence structure of triangular labyrinth weir‐pool fishways

Detailed laboratory experiments were conducted to analyze and evaluate a new weir‐pool fishway design. The new design consisted of a series of one‐cycle, triangular labyrinth weirs that formed a weir‐pool fish passage. Hydraulic characteristics of flow over the proposed fishway were examined for three pool lengths and a wide range of discharges. It was found that the new design had superior discharge capacity over classical weir‐pool fishways in plunging flow regime. Spatial and point analyses of measured velocity data were carried out to understand turbulence structure and distribution of turbulent flow. The power dissipation per unit volume was calculated for different tests, and it varied nonlinearly with discharge. Based on the limiting criteria for energy dissipation rates of different fish species, the maximum operating discharge for different slopes was extracted for the proposed design. The model‐to‐prototype scaling analysis was performed based on the recommended scaling factor of three for prototype. It was found that the approach velocity of prototype increased by 12%, whereas the total discharge increased by more than five times. The contour plots of time‐averaged velocity indicated that the proposed fishways offered diversified flow fields without exceeding the maximum velocity above the standards recommended for weir‐pool fishways. To study the size, direction, and periodicity of turbulent eddies, magnitude of the most energetic eddy and dominant frequencies were extracted using power spectrum analysis. Quadrant analysis consistently showed that Reynolds shear stresses in ejection and sweep events became weaker as the pool length increased. The small region of strong ejection and sweep events evidenced a good resting place for fish migration, whereas the generated turbulence was large enough to attract fish species to use the passage.     

环形波纹钢管涵洞式鱼道水力特性数值模拟

环形波纹钢管涵洞式鱼道内波纹的粗糙度可以使边界附近产生足够低的流速,鱼类可以由此游向上游。对3种流量0.05,0.07,0.09 m3/s,3种埋深0D,0.1D,0.2D,坡度0.4%工况下,环形波纹钢管涵洞式鱼道内水面线、流速场和紊流场分布分别进行了数值模拟研究。结果表明环形波纹钢管涵洞中,高流速区（无量纲流速大于0.9）位于涵洞过水断面中心区域,高紊流区（紊流强度大于0.2）位于水面中心附近。在涵洞底部边壁附近较大区域内,由于流速较小,紊流强度也较低（紊流强度小于0.1）,鱼类可以由此顺利完成上溯。相比无埋深式涵洞,嵌入式涵洞内平均流速较小,紊流强度变化较为平缓,更有利于鱼类的洄游。     

An assessment of the effectiveness of a vertical‐slot fishway for non‐salmonid fish at a tidal barrier on a large tropical/subtropical river

Fishways for salmon in temperate rivers have often been successful, but salmonid‐type fishways for non‐salmonid species in tropical and subtropical rivers have frequently failed. This study assessed the effectiveness of modifying a salmonid‐type pool‐and‐weir fishway into a vertical‐slot design on a tidal barrage on the subtropical Fitzroy River, in Queensland, north‐eastern Australia. In 38 paired samples of the top and bottom of the fishway, over 16 months, 29 fish species and over 23 000 fish were collected at a maximum rate of 3400 per day. This study shows much greater potential for success with a vertical‐slot fishway as relatively few fish negotiated the original pool‐and‐weir design. Common species using the vertical‐slot fishway included blue‐catfish (Arius graeffei [Ariidae]), bony herring (Nematalosa erebi [Clupeidae]), striped mullet (Mugil cephalus [Mugilidae]), barramundi (Lates calcarifer [Centropomidae]), and long‐finned eels (Anguilla reinhardtii [Anguillidae]). Freshwater shrimp (Macrobrachium australiense [Palaemonidae]), juvenile crabs (Varuna litterata [Grapsidae]) and long‐finned elvers did not ascend the full length of the fishway and specific fishways for these species are recommended. Fish between 25 and 640 mm in length ascended the fishway, although the passage of smaller size classes of immature fish was restricted and this may be important for the sustainability of these migratory populations. The barramundi (200–640 mm) which ascended the fishway were all immature fish. However, during a period of low river flows enlarging the width of the vertical‐slot from 0.15 to 0.45 m only encouraged a small number of larger fish (890 mm maximum length) to enter. The strong diel movement patterns of many species will need to be considered in future fishway design. Blue‐catfish could ascend the fishway in 2 h, but many fish remained in the fishway and this behaviour may cause crowding and a reduction in fishway capacity. Further work is needed to assess the proportion of fish finding the fishway entrance. However, the findings suggest that vertical‐slot fishways with lower water velocities and turbulence than salmonid fishways have great potential to pass the diverse migratory fish fauna of subtropical and tropical rivers. Copyright © 1999 John Wiley & Sons, Ltd.     

Numerical study of the effect of a V-shaped weir on turbulence characteristics and velocity in V-weir fishways

Fishways are used to allow fish to migrate around water infrastructure, whether movements are in the upstream or downstream direction. Hydrodynamic conditions within various fishways, including turbulence levels, are important for successful fish passage. A numerical hydrodynamic study was conducted for V-weir fishways, which assist species migrating upstream. The variables investigated included, fishway slopes of 4%, 7%, and 10%, relative spacing between weirs of 1.3, 2.6, and 4 (D/L, ratio of distance between weirs to pool width), and weir angles of 22.5°, 40°, and 60°. Turbulence characteristics, including turbulent kinetic energy (TKE), Reynolds shear stress (RSS), turbulent intensity (TI), turbulent dissipation (TD), as well as maximum water velocity, were examined by CFD (computational fluid dynamics) simulation using a re-normalized group or RNG turbulence model. The CFD was calibrated with flow measurements made in a physical model of the V-weir fishway in laboratory control experiments. Based on inferences from fish passage literature, the results showed that, in the range of parameters studied, a weir angle of 22.5^°, a slope of 10% and relative spacing between weirs of 1.3 and 2.6 were assessed as offering the best potential performance for several species and sizes of fish, while the latter has lower cost as it requires fewer weirs. The V-weir fishway may be adaptable for smaller fish.     

小长宽比鱼道池室水力学试验研究

鱼道水流条件是影响其过鱼效果的重要因素。在分析鱼道类型及其特点的基础上,针对应用最为广泛的竖缝隔板式鱼道,通过1∶4的大比尺局部物理模型试验,研究了各级水池长宽比小于1.0条件下的隔板布置及竖缝宽度,对比了3种布置方案,分析评价了竖缝流速指标以及池室流速分布、流态和消能特性,提出了适合小长宽比池室条件下的鱼道隔板布置型式。通过1∶12.5的鱼道整体水力学模型试验,对运行水力指标进行了验证分析,确立了减小隔板前局部水位壅高及提高竖缝流速沿程均匀性的设计原则;为适应鱼道进、出口水深的变化,从生态明渠引水补充鱼道流量,最小补水流量为0.22 m~3/s。试验结果表明,这种鱼道布置型式可推广应用到其他类似鱼道工程中。     

鱼道进口水流对草鱼幼鱼上溯行为的影响研究

为使鱼类能够快速发现和顺利进入鱼道进口并成功过坝,设计了鱼道进口概化模型。以草鱼幼鱼为研究对象,在18±1℃的条件下研究了鱼道进口流速对鱼类上溯行为的影响。研究发现:鱼道进口水流存在一个最佳流速,在该流速下,鱼类进入鱼道进口的效率最高。利用诱鱼流道补水有助于进一步提高鱼道进鱼效率,诱鱼流道水流与鱼道进口水流之间存在一个最优流速比。针对草鱼幼鱼的鱼道进口最佳流速约为0.3 m/s,诱鱼流道水流与鱼道进口水流的最佳流速比约为2.3。通过对洄游区鱼类游泳轨迹以及流场耦合,可知草鱼幼鱼上溯的喜好流速范围是0.20~0.30 m/s。研究成果对于鱼道进口水力设计具有重要意义。     

齐口裂腹鱼幼鱼在竖缝式鱼道模型中的上溯行为研究

为了解齐口裂腹鱼在鱼道中的上溯情况,在大比尺竖缝式鱼道物理模型中开展了以齐口裂腹鱼幼鱼为过鱼对象的过鱼试验研究。试验中对通过时间、通过率和上溯轨迹进行了记录,并运用Spearman秩相关分析对齐口裂腹鱼的上溯轨迹和池室结构的水力因子(流速、紊动能、总水力应变)进行了分析。研究发现,试验用鱼通过时间平均值为132.7s,多数鱼倾向于快速通过鱼道完成上溯。试验鱼道通过率为71.9%,过鱼效果良好。多数齐口裂腹鱼上溯过程中会避开高流速区、高紊动能区和高水力应变区,在池室内齐口裂腹鱼上溯轨迹主要分布于上述参数较低的右侧回流区和隔板背水面,竖缝断面处多数齐口裂腹鱼选择上述参数相对较低的隔板侧区域通过。研究结果可为相关竖缝式鱼道设计和实践提供参考。     

仿自然鱼道的一般布置原则及数值模拟研究

拟建的阁山水库会阻断鱼类的洄游通道,为解决鱼类上溯问题,将同时布置仿自然鱼道。基于 仿自然鱼道的一般布置原则,建立了适合研究仿自然鱼道数值模拟的ＣＦＤ模型,并通过物理模型试验研 究成果进行了模型验证和率定。在此基础上对鱼道不同的障碍物布置尺寸和间距开展了优化比较,通 过研究鱼道内的流速分布及流量等水力参数,确定了较合理的障碍物布置形式。研究表明,增大障碍物 的尺寸和减小障碍物的间距均可以增强对水流的阻碍作用。综合分析后推荐本鱼道工程障碍物布置的 较合理形式为:高2．0ｍ,长4．0ｍ,宽2．5ｍ,间距10ｍ。此布置形式在设计工况下,鱼道内的流速范围 为0．3ｍ／ｓ～1．2ｍ／ｓ,主流明确,能够满足各种鱼类的上溯要求。