异齿裂腹鱼通过鱼道内流速障碍能力及行为

鱼类通过流速障碍能力是鱼道设计的主要生态指标,目前国内外主要使用封闭游泳水槽进行鱼类各种游泳速度指标及游泳行为研究,其水流流态及鱼类游泳行为与鱼类通过鱼道的实际状态有较大的差距,有必要结合鱼类游泳速度指标来探索能够更加准确量化鱼类通过鱼道流场的游泳能力测试方法。首先,在封闭游泳水槽中通过速度递增法测得异齿裂腹鱼临界游泳速度(101.01±20.86 cm/s)和突进游泳速度(196.94±21.80 cm/s);然后,以临界游泳速度和藏木水电站鱼道竖缝流速(110.00 cm/s)为参考,通过在开放游泳水槽内加不同束窄梯形体,形成类竖缝式鱼道的鱼类自主游泳能力测试水槽,开展两种底坡条件下4级短竖缝(工况1和工况2竖缝流速为101.55±14.87 cm/s、114.63±24.28 cm/s,竖缝顺水流长度均为40 cm)和单级长竖缝(工况3竖缝流速为137.45±17.63 cm/s、竖缝顺水流长度为160 cm)下试验鱼通过流速障碍能力和行为研究。试验结果表明:工况1、工况2下试验鱼通过4级竖缝成功率分别为82.05%、84.62%,通过流速大于临界游泳速度的竖缝时,持续爆发游泳时间为0.52±0.34 s;工况3下93.33%试验鱼以209.43±21.76 cm/s游泳速度成功通过单级长竖缝;3种工况下试验鱼通过流速大于临界游泳速度的竖缝时,以与突进游泳速度无显著性差异(P0.05)的恒定游泳速度(214.01±30.64 cm/s)上溯。鱼类游泳轨迹与流场耦合分析表明:鱼类上溯所需时间及路径长度与其选择的游泳路径密切相关,试验鱼通过借助回流区同向水流推动,增加上溯效率。本文研究方法及研究结论可为鱼道设计、改造、评价提供依据。     

Effect of head swing motion on hydrodynamic performance of fishlike robot propulsion

This paper studies the effect of the head swing motion on the fishlike robot swimming performance numerically.Two critical parameters are employed in describing the kinematics of the head swing: the leading edge amplitude of the head and the trailing edge amplitude of the head.Three-dimensional Navier-Stokes equations are used to compute the viscous flow over the robot.The user-defined functions and the dynamic mesh technology are used to simulate the fishlike swimming with the head swing motion.The results reveal that it is of great benefit for the fish to improve the thrust and also the propulsive efficiency by increasing the two amplitudes properly.Superior hydrodynamic performance can be achieved at the leading edge amplitudes of 0.05L( L is the fish length) and the trailing edge amplitudes of 0.08 L.The unsteady flow fields clearly indicate the evolution process of the flow structures along the swimming fish.Thrust-indicative flow structures with two pairs of pressure cores in a uniform mode are generated in the superior performance case with an appropriate head swing,rather than with one pair of pressure cores in the case of no head swing.The findings suggest that the swimming biological device design may improve its hydrodynamic performance through the head swing motion.     

Numerical and experimental studies of hydrodynamics of flapping foils

The flapping foil based on bionics is a sort of simplified models which imitate the motion of wings or fins of fish or birds. In this paper, a universal kinematic model with three degrees of freedom is adopted and the motion parallel to the flow direction is considered. The force coefficients, the torque coefficient, and the flow field characteristics are extracted and analyzed. Then the propulsive efficiency is calculated. The influence of the motion parameters on the hydrodynamic performance of the bionic foil is studied. The results show that the motion parameters play important roles in the hydrodynamic performance of the flapping foil. To validate the reliability of the numerical method used in this paper, an experiment platform is designed and verification experiments are carried out. Through the comparison, it is found that the numerical results compare well with the experimental results, to show that the adopted numerical method is reliable. The results of this paper provide a theoretical reference for the design of underwater vehicles based on the flapping propulsion.     

三鱼群游流动干扰及其减阻机理的数值研究

观察研究发现,在鱼类的群游中,鱼体可以有效利用相互之间有益的干扰,减少游动阻力,增强自己的推力和游动效率。文中作者基于以往建立的动态混合网格生成方法以及不可压缩流非定常计算方法,对三鱼呈“三角”阵型排列的群游进行了数值模拟,通过对不同横向间距、不同流向间距、不同相位差等游动状态下的流场结构、力学特性的比较,分析了鱼体之间的横向干扰和流向干扰,研究了流动干扰减阻的机理。     

斑马鱼在Cu~(2+)胁迫下运动行为变化研究及其应用

以斑马鱼为指示生物,系统研究了斑马鱼在Cu2+的胁迫下其运动行为变化规律,发现斑马鱼的游动速度、群体分布特征、分布区域与游动姿态均会发生明显改变。具体表现为:短期内斑马鱼的游动速度与游动距离,群体平均间距与紧凑度,平均短轴与平均长轴长度均会出现快速增加,在不同区域出现的概率差异缩小;随着时间延长,斑马鱼加速后的游动速度与游动距离,群体平均间距与紧凑度,平均短轴与平均长轴长度又会出现快速下降,在不同区域出现的概率又重新分化。随着毒害的进一步加深,斑马鱼的运动能力会进一步下降,表现为各运动参数的变幅收窄。分析斑马鱼的这些运动特征,可以判断水体中Cu2+的浓度。对6种典型毒物的测试结果表明,与传统采用鱼类死亡作为判断终点的毒性测试方法相比,利用鱼类行为变化的测试方法能显著缩短测试时间,提高测试灵敏度。     

永庆水库仿自然过鱼通道水力学特性研

调查了永庆水库库区珍惜保护鱼类，给出了该水库过鱼设施流动指标。通过交错石块式仿自然过鱼通道局部水工模型试验，研究了交错石块式仿自然过鱼通道内的水力学特性，总结分析了模型试验结果。分析论证表明：该交错石块式仿自然通道可满足永庆水库目标鱼类的洄游需求，为仿自然过鱼通道的设计和研究提供了依据。     

Diversity and Community Structure of Fishes in the Regulated Versus Unregulated Tributaries of the Mekong River

Diversity and community structure of fishes were studied in three neighbouring tributaries of the Mekong River in Thailand, namely the Mun, Songkhram and Gam Rivers. The rivers are located in the same ecoregion but have contrasting levels of both hydrological regulations and mitigation measures; the Mun River has a hydropower dam with a fish ladder and sluice gates that are opened during the wet season each year, the Gam River has several irrigation dams with a fish ladder at each dam site, and the Songkhram River has no dams along its river course. A total of 124 freshwater fish species were sampled in these rivers from August 2009 to June 2010. Overall species richness was highest in the Songkhram River (112), followed by the Mun (97) and Gam (54) Rivers. Average per site species richness was also significantly different among rivers but not among sampling months. Abundance–biomass comparison plots revealed considerably overlapping distributions of these two metrics from the dry to early rainy seasons in the Songkhram River and, to a lesser extent, in the Mun River. Fish assemblage data were classified into six clusters with similar community structure. Fish assemblages in the Gam River constituted a single cluster, while those in the other two rivers formed multiple clusters depending on the sampling season. The results of the cluster analysis are discussed in relation to the dominance of the three migration guilds (white, black, and grey fishes) of the Mekong River fishes. The effectiveness of the mitigation measures was determined to be limited in alleviating adverse impacts of dams in these tributaries of the Mekong River. Copyright © 2014 John Wiley & Sons, Ltd.     

天然河道中鱼类对水深、流速选择特性的初步观测——以长江江口至涴市段为例

将长江江口至涴市天然河道的鱼类水声学调查数据和水文学观测数据相结合,在对流速和水深空间插值基础上,提取不同鱼类规格和密度对应水深和流速的特征值,从而研究鱼类对天然河道中水层平均流速、水深2个环境因子的选择特性。研究结果表明：①不同规格的鱼对流速和水深的选择存在差异,规格小的鱼选择了较低的流速和较宽的流速范围,规格大的鱼选择了较高的流速和较窄的流速范围;规格小的鱼选择的水深明显高于规格大的鱼,喜好的水深范围也宽于规格大的鱼。②鱼类密度对流速的选择性不明显,但对水深的选择性明显,即深水区鱼类密度较高。③研究江段范围内江口镇附近江心洲两侧流速变幅范围较其上、下游江段宽,并且江心洲两侧鱼类的分布密度也高于其邻近上、下游段鱼类密度。可见,江心洲的存在提供了流速多样性格局,丰富了鱼类生境的多样性。本研究方法可为评价河流栖息地适宜性及生态功能提供借鉴。     

ECOLOGICAL FUNCTIONS OF FISH BYPASS CHANNELS IN STREAMS: MIGRATION CORRIDOR AND HABITAT FOR RHEOPHILIC SPECIES

The introduction of weirs into stream ecosystems resulted in modifications of serial continuity and in the decline of riverine fish species. Successful river restoration requires information on the ecological functionality of fish bypass channels that are considered an ecological improvement according to the European Water Framework Directive. In this study, we compared the functionality of three nature‐oriented fish passes as compensatory habitats and migration corridors for fishes. Fish passes differed significantly from upstream and downstream reaches of the weirs, revealing higher current speed, lower water depth, smaller channel width and greater habitat variability. Following these structural differences, they provided key habitats for juvenile, small and rheophilic fishes that are typically underrepresented in highly modified water bodies. All fish passes were used as migration corridors, with increased fish movements during high discharge and at spawning periods. Because river stretches with high variability of current speed and water depth are scarce in highly modified water bodies, fish passes can play an important role as compensatory habitats and should thus be considered more intensively in habitat assessments and river restoration. Ideally, fish bypasses should mirror the natural discharge dynamics and consider all occurring fish species and sizes. Copyright © 2011 John Wiley & Sons, Ltd.     

Propulsive performance of a passively flapping plate in a uniform flow

Propulsive performance of a passively flapping plate in a uniform viscous flow has been studied numerically by means of a multiblock lattice Boltzmann method. The passively flapping plate is modeled by a rigid plate with a torsion spring acting about the pivot at the leading-edge of the plate, which is called a lumped-torsional-flexibility model. When the leading-edge is forced to take a vertical oscillation, the plate pitches passively due to the fluid-plate interaction. Based on our numerical simulations, various fundamental mechanisms dictating the propulsive performance, including the forces on the plate, power consumption, propulsive efficiency and vortical structures, have been studied. It is found that the torsional flexibility of the passively pitching plate can improve the propulsive performance. The results obtained in this study provide some physical insights into the understanding of the propulsive behaviors of swimming and flying animals.     

Long‐term Dynamics of Large‐bodied Fishes Assessed from Spatially Intensive Monitoring of a Managed Desert River

Imperilment of native fishes worldwide, and particularly in the American Southwest, has prompted management actions to protect and recover threatened populations. Implementation of management activities, however, often proceeds without clear understandings of ecological interactions between native fishes and other biotic and physical components of the environment. Using data obtained in a 19‐year, intensive monitoring effort across 288 km of the San Juan River in NM and UT, USA, we quantified relationships among large‐bodied fishes and longitudinal environmental gradients, tested for faunal breaks of fishes and habitat structure along the river's course, and assessed the response of fishes to mechanical removal of non‐native fishes and stocking of endangered fishes. Mesohabitat variation was not strongly linked to densities of large‐bodied fishes, but we found strong and temporally consistent longitudinal patterns of native and non‐native fishes: Native fish densities were highest upstream while non‐native fish densities where highest downstream, potentially driven by differential responses to temperature regimes. Two breaks in the longitudinal structure of large‐bodied fishes were identified and were associated with a man‐made barrier and changes in the width of the river's floodplain. While densities of common native fishes were relatively constant during the study, non‐native fish removal apparently reduced densities of one of two targeted species and densities of two endangered fishes increased as a result of stocking hatchery‐reared fish. Results of this study suggest that large‐bodied fishes of the San Juan River are responding to large‐scale longitudinal gradients rather than small‐scale habitat variation and management activities have altered densities of target species with limited responses by other fishes in the system. Copyright © 2014 John Wiley & Sons, Ltd.     

三体船耐波性的模型试验研究

通过三体船模型的耐波性试验,包括横摇试验、规则波中的迎浪试验,研究了三体船的耐波性能以及侧体纵向位置对三体船耐波性的影响。试验结果表明,航速对三体船耐波性能的影响与对单体船的影响类似,而侧体纵向位置对于三体船耐波性能的影响是比较大的。     

PROPULSIVE PERFORMANCE AND VORTEX SHEDDING OF A FOIL IN FLAPPING MOTION

1 .　INTRODUCTIONInsectsandfishhaveexperiencedabillions yearprocessofevolutionwithnaturalselectionfortheirsurvivalandhavedevelopedtheirsuperiorandcomplete performanceofflightandswim ming .Usually ,aflappingmotionisabasicmodeoflocomotionforinsects ,birds ,andfish .Thrustandliftaregeneratedwhentheflappingwingsortailsinteractwiththesurroundingfluids .Becauseofthehighlyunsteadynatureofviscousflowaroundaflappingwing ,itisfarfromsatisfactorytounderstandthephysicalmechanismandvortexsheddinginuns…     

基于物理栖息地模拟的长江中游生态流量研究

将Delft3D水力学模型和栖息地模型组成物理栖息地模拟模型以研究鱼类的生态环境。以长江中游宜昌至枝江河段为研究区域,以长江的重要经济鱼类四大家鱼为目标物种,结合流速及水深两个栖息地限制因子计算研究区域内不同流量下四大家鱼4个产卵场的栖息地面积,得到了流量与栖息地面积关系曲线。分析该曲线,结果表明：长江中游四大家鱼4—6月份产卵期间的最小生态流量为4 570m3/s,适宜生态流量范围为12 000~15 500m3/s。计算结果在传统水文学法界定的生态流量范围之内,分析认为该计算结果更加合理,可为四大家鱼的保护和三峡及葛洲坝工程的生态调度提供参考建议。     

A NUMERICAL STUDY ON A SIMPLIFIED TAIL MODEL FOR TURNING FISH IN C-START

1. INTRODUCTION Fishes have experienced a long evolution processwith natural selection, and exhibit a large variety of swimming gaits, relevant to their body shapes and surrounding environments[1,2]. Usually, pelagic fishes are experts in long-distance cr…     

A COMPARISON OF TWO ELECTROFISHING PROGRAMMES USED TO MONITOR FISH ON THE ILLINOIS RIVER,ILLINOIS, USA

The Illinois River Biological Station monitors fish communities in the Illinois River using two different electrofishing programmes, one using three‐phase alternating current [AC; The Long Term Illinois Fish Population Monitoring Program or long‐term electrofishing (LTEF)] and the other pulsed direct current [DC; The Long Term Resource Monitoring Program (LTRMP)]. In 2001, we replicated three‐phase AC sampling sites with pulsed‐DC electrofishing gear to test for differences between the two collection methods and programmes. Electrofishing runs at each site were standardized by length and time, with 48 samples collected for each gear. Our objective was to test for differences in fish catch rates using total catch, species richness, fish size ranges, and sample composition and structure. Total catch was significantly greater for LTRMP electrofishing (4368 total fish, mean = 91.0 fish per sample) compared with LTEF electrofishing (1423 total fish, mean = 29.6 fish per sample). Species richness also was significantly greater for LTRMP electrofishing (50 total species, mean = 12.9 species per site) compared with LTEF electrofishing (38 total species, mean = 7.9 species per site). Size ranges of fishes, composed of 100‐mm‐length groups, showed higher total catches for the LTRMP within all length groups. Although our analyses suggest that collections from the LTRMP were significantly greater in most instances, a consistent pattern of species composition between the two programmes was not evident. Our results suggest that caution must be taken when attempting to compare fish community composition and structure information between these programmes. Copyright © 2011 John Wiley & Sons, Ltd.     

竖缝式鱼道水力特性与鱼类运动特性相关性分析

竖缝式鱼道(Vertical Slot Fishway,VSF)作为一种协助上溯性鱼类恢复其洄游通道的生态补偿措施,受到广泛关注。其过鱼效果与VSF的水力特性和鱼类的游泳运动能力密切相关。因而,良好的VSF设计应保证池室内的水力特性与过鱼对象的游泳运动能力相适宜。本文选取上溯性鱼类鳙鱼和草鱼为研究对象,将VSF池室内水力因子空间分布与鱼类运动轨迹相叠加,定量分析了鳙鱼和草鱼在上溯过程中的运动特性、水力偏好以及鱼类运动轨迹与特定水力因子的相关程度。试验结果表明:在流量为0.135 m3/s的VSF池室内,两种鱼喜好在紊动能为0.02~0.035 m2/s2、流速为0.16~0.4 m/s、紊动耗散率为0.02~0.04 m2/s3、应变率为2~3.5 s-1的范围内运动。鳙鱼和草鱼在不同水力区域内的上溯时间与紊动能、流速相关性较大;水流流速矢量体现鱼的趋流特性,决定了鱼的上溯方向,而对于局部空间内鱼的游泳运动行为,紊动能可能是影响更直接的水力因子。     

Self-propulsion of a three-dimensional flapping flexible plate

The self-propulsion of a 3-D flapping flexible plate in a stationary fluid is numerically studied by an immersed boundarylattice Boltzmann method for the fluid flow and a finite element method for the plate motion. When the leading-edge of the plate is forced to heave sinusoidally, the entire plate starts to move freely as a result of the fluid-structure interaction. Based on our simulation and analysis on the dynamical behaviors of the flapping flexible plate, we have found that the effect of plate aspect ratio on its propulsive properties can be divided into three typical regimes which are related to the plate flexibility, i.e. stiff, medium flexible, and more flexible regime. It is also identified that a suitable structure flexibility, corresponding to the medium flexible regime, can improve the propulsive speed and efficiency. The wake behind the flapping plate is investigated for several aspect ratios to demonstrate some typical vortical structures. The results obtained in this study can provide some physical insights into the understanding of the propulsive mechanisms in the flapping-based locomotion.     

Impoundments affect fish reproduction regardless of reproductive strategy

Major changes to local river habitats, after impoundment, are expected to restrict the reproductive activity of fishes with migratory strategies, although the changes are not expected to have relevant effects on fishes with other strategies. The reproductive activity of fishes with different reproductive strategies was evaluated along a longitudinal gradient before, and after, the formation of a reservoir on the Tocantins River (Tocantins State, Brazil). Samples were collected at six sites distributed along 80‐km stretch of the reservoir (R1 to R6 in the upstream–downstream direction) before and after the impoundment. The highest mean values of the reproductive activity index (RAI), considering all species in the river phase, were recorded for the intermediate segments (R4). The reproductive activity was classified as intense at the two sites located further upstream (R2 and R1). The highest mean RAI value after impoundment was observed for the site further upstream (R1). The reproductive activity was classified as intense, however, at every site, except for R6. Regardless of the reproductive strategy, mean RAI values were higher in this phase at site R1, particularly for long‐distance migratory species (LDM). The most lacustrine area (R6) was only relevant for the group of species with parental care. For non‐long‐distance migratory species, without parental care, the reproductive activity was intense at every site, except for R6. Overall, after the impoundment, the fish species tended to seek more lotic environments to spawn, including the riverine zone of the reservoir and side tributaries, regardless of the reproductive strategy. The results of this study provide evidence that impoundments affect the reproduction of the fish, independent of the reproductive strategy, although the intensity of the effect is different for each group.