Vertical Slot Fishway Research Articles

Analytical Models for Determining the Propagation of Rectangular Surface Jets for Fishway Attraction Flow

The present paper evaluates suitability of two analytical models to determine the propagation of rectangular surface jets as a tool to design fishway attraction flow. It focuses on rectangular orifices of vertical slot fishways with aspect ratios (width-to-height) for W/H < 1. Both models were rewritten to match boundary conditions for fishways because they were initially derived for horizontal orifices. As the basis for the evaluation, the output of the analytical models to RANS simulations for 12 geometries 1/16 <= W/H <= 4 is compared. Applied analytical equations for half-lengths for cases W/H >= 4 are within 5 % of RANS modeling results for all cases. The location of centerline transition locations from analytical models also agree reasonably well with RANS modeling. The findings support efficient design of optimum attraction flow propagation using simple, rapid analytical approaches.

OpenFOAM vs FLOW-3D: A comparative study of vertical slot fishway modelling

The objective of this study is to make a comparison between two 3D CFD platforms: OpenFOAM (free and open-source CFD software) and FLOW-3D (closed source commercial CFD software), focusing on vertical slot fishways, one of the most widespread solutions to facilitate the fish migration through transversal obstacles in rivers. Considering previous comparative studies, our initial hypothesis is that both OpenFOAMs' multiphase solver and FLOW-3D provide good comparable results. In this study, in contrast to previous comparative studies, turbulence was addressed using LES approach and the volume of fluid method was used to model the multiphase interface (air-water). Mesh independency was assessed through LES IQ index and the numerical models' accuracies were evaluated comparing representative hydraulic variables (velocity, its components, and turbulence kinetic energy) with ADV experimental data and discussing results in previous studies. Both platform codes reproduced the scenario under study, concurred with experimental data and offered a superior performance on flow structure velocity simulation than turbulent kinetic energy. Results validate the use of the free and open platform OpenFOAM as a viable alternative to commercial ones in the domain of fishway design and assessment. While OpenFOAM provides a reliable free alternative, FLOW-3D has a faster setup and makes the simulating experience apt for beginners.

Numerical Investigation of Hydraulics in a Vertical Slot Fishway with Upgraded Configurations

The implementation of vertical slot fishway (VSF) has been demonstrated to be an effective mitigation measure to alleviate extensive river fragmentation by artificial hydraulic structures such as weirs and dams. However, non-suitable flow velocity and turbulent kinetic energy significantly affect fish swimming behavior and, as a result, hinder such facilities’ performance. Therefore, this study’s main objective is to propose a new configuration of VSF that can allow the passage of different fish species under frequent variations of flow discharge. To achieve that objective several novel configurations of VSF were numerically investigated using the FLOW-3D® model. Namely, five variants of angles between baffles, four different pool widths, and another upgraded version of VSF by introducing cylindrical elements positioned after the opening behind the baffles were tested. Results show that smaller angles between baffles increase the Vmax and decrease the maximum turbulent kinetic energy (TKEmax); the opposite result was obtained when increasing angles between baffles. Namely, the Vmax was increased up to 17.9% for α = 0° and decreased up to 20.37% for α = 37°; in contrast, TKEmax decreased up to −20% for α = 0° and increased up to 26.5% for α = 37°. Narrowing the pool width increased the Vmax linearly; nevertheless, it did not significantly affect the TKEmax as the maximum difference was only +3.5%. Using cylinders with a large diameter decreased the Vmax and increased TKEmax; in contrast, using cylinders with smaller diameters further reduced the Vmax velocity inside the pool while increasing the TKEmax. However, in the case of cylinders, the dimension of the recirculation depended on the configuration and arrangement of the cylinder within the pool. Overall, the maximum velocity was reached at near 77% of the water depth in all cases. Finally, solution-oriented findings resulted from this study would help water engineers to design cost-effective VSF fishways to support the sustainable development of hydraulic structures while preserving aquatic biodiversity.

Experimental Investigation of the Reynolds Shear Stress Exceedance Rate for the Injury and Disorientation Biocriteria Boundary in the Pool-Orifice and Vertical Slot Type Fishways

Fragmentation of rivers has a negative impact on river’s ecological status which can be improved by the construction of fishways next to obstacles in rivers that prevent a free migration. Flow field characteristics are key factors in the design process of hydraulically efficient fishways—flow and turbulence patterns in a functional fishway allow fish to enter, progress through and exit with minimum time/energy expenditure. The aim of this paper is an experimental study of the flow field characteristics measured in the physical fishway model with the goal of providing information on the Reynold’s shear stress distribution that would facilitate their design in accordance with the environmental requirements. The focus of the research was on the nominally hydraulically efficient con-figuration pool-type fishways—pool-orifice and vertical slot. Fishway geometry was varied for bottom slope (7.5%, 10% and 12.5%), pool length (45 cm, 60 cm and 90 cm) and orifice size (8 × 8 cm, 10 × 10 cm and 12 × 12 cm) in a model scaled 1:3 to the prototype. Since Reynold’s shear stress has been identified as the main turbulent parameter affecting fish swimming performance and behavior, it is used as the basis for the analyses. The velocity data were collected with Vectrino ADV and processed in all three planes—streamwise, horizontal and vertical. Reynold’s shear stress data were analyzed according to the injury (>50 N/m2) and disorientation (>30 N/m2) biocriteria boundaries defined in the literature. The percentage of the flow field exceeding the boundaries were analyzed depending on the fishway geometry. The results obtained in this research suggest that the critical design parameter is the orifice size for the pool-orifice fishways and the pool length for the VS fishway. The Reynold’s shear stress is generally the highest in the bottom layer for pool-orifice fishways and the surface layer for vertical slot fishways.

Application of recent SPH formulations to simulate free-surface flow in a vertical slot fishway

Application of recent SPH formulations to simulate free-surface flow in a vertical slot fishway

Relationship between Upstream Swimming Behaviors of Juvenile Grass Carp and Characteristic Hydraulic Conditions of a Vertical Slot Fishway

The successful fish upstream movement through a dam/gate is closely associated with the hydraulic conditions of a fishway. To improve the passage efficiency, this study investigated the upstream swimming behaviors of juvenile grass carp, a representative fish of four major Chinese carps, under characteristic hydraulic conditions of a designed vertical slot fishway model. The impacts of different discharges and baffle lead angles on the successful movement of test fish were analyzed, and the selection of the movement trajectory was studied through overlay of their upstream swimming trajectories on the water flow field resulting from numerical modeling. We found that under the same discharge, the percentage of successful test fish movement with a lead angle of 45° was higher than 60° and 30°. Within a fixed lead angle, the higher the discharge, the lower the percentage of successful movement. During upstream movement, the test fish had a preferred water velocity of 0.01–0.45 m/s in the pool, and avoided areas where the turbulence kinetic energy (TKE) was greater than 0.012 m2/s2. These results provide a basis for the hydraulic design of vertical slot fishways and a reference for studying swimming behaviors of other fish species.

Izbor oblika riblje staze s vertikalnim otvorima na temelju primjene ABM modela

Physical and 3D numerical hydrodynamic flow models and an agent-based model are developed with the principal objective of analysing fish behaviour in two vertical slot fishway configurations. Fish energy consumption due to swimming represents a crucial criterion for selecting an appropriate fishway configuration. The modelled fish detects ambient flow conditions, makes decisions based on its sensing and cognitive abilities, adapts to the changes in its environment, and moves toward the regions of less turbulent kinetic energy. The results show that fishways with longer pools enable passage of fish at a lower energy consumption.

Hydraulic design criteria of the modified meander C-type fishway using the combined experimental and CFD models

Fishways' structure has been developed to mitigate the harmful effects of human-made structures such as dams and weirs on the migratory fish process as an essential part of the environmental cycle. In this study, a Modified Meander C-type Fishway (MMCF) was designed and analyzed based on a fish species movement capability. The proposed fishways' structural design follows the key features of the vertical slot fishways (VSF) structure and consists of eleven successive cylindrical pools connected through vertical slots. In the present study, physical and computational fluid dynamics were used to investigate the flow characteristics inside the cylindrical pools with designed radius (R) and vertical slots as the system's connectors. Different geometry scenarios were applied to the model, such as the slots' various dimensionless opening ratios (s/R = 0.1, 0.2, 0.3) with varying bed slope scenarios (5%, 10%, and 20%). The obtained results illustrated the dimensionless hydraulic design diagrams based on the dimensionless discharge parameter (Q⁎) as a critical parameter for designing and operating the fishways. Horizontal and vertical flow velocity distribution graphs were presented, which could be used to estimate a potential low-velocity field for each specific fish species. As a geometrical improvement scenario, the pool's average-depth parameter (d) was increased for each scenario using the designed vertical baffles adjusted at the pools' opening gate with different vertical slot's height scenarios (hb/R = 0, 0.1, 0.2). Studying the radial and tangential fluctuations of the turbulent flow inside the proposed fishway demonstrated the structure's performance to make a more stable swimming path for the fishes toward the upstream movement.

Numerical Analysis on the Effect of Slot Width on the Design of Vertical Slot Fishways

An accurately designed fishway plays an important role in dimensioning migration issues of fish and assists in allowing fish to meet their life cycle’s essential necessities. ANSYS FLUENT was used to study the effect of changing slot width on the velocity, turbulence kinetic energy, and head difference (Δh) in water level inside the fishway. The turbulence model was used to predict the local zone turbulence inside the fishway. Using a previously designed model suggested by Zhang in 2017, this study investigated the influence of the change of the slot width for five values, 0.2, 0.25,0.3,0.4, and 0.5 m. The velocity value obtained for 0.2 m slot width (bo), which represented 10% from pool width (B), was 1.57 m/s. While, for a slot width of 0.5 m which represented 25% from pool width, the velocity value was 1.59 m/s with high turbulence regions inside the pools due to the increase in the velocity of the flow. The best flow velocity obtained was 1.23 m/s. This value was obtained when using a 0.3 m value for the slot width. The turbulence kinetic energy for this value of the slot width was 0.08 m 2;/s 2;. Therefore, the value of 0.3 m of the slot width was considered as the optimum value for the examined vertical slot fishway design. The optimum ratio of the slot width to the pool width (bo/B) was 15%.

Multislot Fishway Improves Entrance Performance and Fish Transit Time over Vertical Slots

Pool-type fishways have been increasingly tested to improve fish passage performance and minimize migration delays. Designing cost-effective fishways is essential for a trade-off between water uses and successful longitudinal connectivity restoration. The multislot fishway (MSF) concept, which operates with 30–50% lower discharge than a vertical slot fishway (VSF), was recently developed. This study assessed and compared the entrance performance (entrance time; entry efficiency) and transit times of two cyprinids for VSFs and MSFs. Four configurations, with the same structural characteristics (slope; water depth; head drop; pool width and depth), operating with different discharges (Q), were tested (VSF 1: Q = 112 L·s−1; VSF 2: Q = 80 L·s−1; MSF 1: Q = 58 L·s−1; MSF 2: Q = 37 L·s−1). Hydrodynamics characterization was performed using a numerical model. Results showed that entry efficiency was higher in MSFs than in VSFs, while entrance time and transit time were overall lower. Numerical modelling revealed that velocities were around 30% lower in MSFs, and turbulence could reach a difference of around 70% in Reynolds shear stress and 50% in turbulent kinetic energy. Overall, MSFs can be considered as a cost-effective fishway solution that can balance the trade-offs between divergent interests in water uses.

A novel ensemble model for predicting the performance of a novel vertical slot fishway

We investigate the performance of a novel vertical slot fishway by employing finite volume and surrogate models. Multiple linear regression, multiple log equation regression, gene expression programming, and combinations of these models are employed to predict the maximum turbulence, maximum velocity, resting area, and water depth of the middle pool in the fishway. The statistical parameters and error terms, including the coefficient of determination, root mean square error, normalized square error, maximum positive and negative errors, and mean absolute percentage error were employed to evaluate and compare the accuracy of the models. We also conducted a parametric study. The independent variables include the opening between baffles (OBB), the ratio of the length of the large and small baffles, the volume flow rate, and the angle of the large baffle. The results show that the key parameters of the maximum turbulence and velocity are the volume flow rate and OBB.

Mathematical modeling of flow in vertical slot fishways

River dams interrupt essential migration routes of fish and other aquatic organisms. One of the most important mitigation measures that enable aquatic fauna to migrate, especially during spawning, are fishways. The paper presents all the main results of the numerical model PCFLOW2D, which proved to be a useful tool in designing a vertical slot fishway (VSF). The presented analysis includes the quantification of the effect of various numerical and geometrical parameters. Extensive field measurements of flow characteristics in the operating fishway at the hydro power plant Arto-Blanca, which are employed for the model's validation, are discussed as well. The results of simulations for various longitudinal slopes of the VSF are presented. In addition to maximum flow velocities and discharge, other important hydraulic parameters affecting fishway efficiency were analyzed, such as velocity field and distribution of turbulent kinetic energy dissipation.

Model-based ecological optimization of vertical slot fishways using macroinvertebrates and multispecies fish indicators

Fishway research has long focused on post-establishment assessments to optimize fish passage efficiency. Model-based optimization with the use of hydrodynamic-habitat models (HHMs) has rarely been employed to investigate passage suitability based on key hydraulic variables. In this study, a vertical slot fishway was designed, the hydraulic properties of twelve types that varied by slope, slot width and pool size were simulated using a two-dimensional HHM, and the suitability of macroinvertebrates and of seven fish groups, encompassing various guilds and size classes, was assessed for each fishway type at seven discharge scenarios, ranging from 0.1 m3/s to 1.3 m3/s. Suitability was primarily influenced by water depth. At optimal depths, suitability was fine-tuned by flow velocity to different optima per biotic group based on fixed interplays between discharge, slope and slot width: water depths were higher at high discharges, low slopes and narrow slots; flow velocities were higher at high discharges, high slopes and wide slots. Our ecologically optimal, multispecies, vertical slot fishway, had 5% slope and 30-cm wide slots, with discharges shifting between 0.15 m3/s and 0.6 m3/s to balance the needs of all species and life stages studied. Yet, even this optimal fishway could not guarantee 100% suitability for all species. The overall suitability was moderate (approx. 50–60%), higher at the pools and lower at the slots, and critically influenced by the type of substrate. We conclude that technical fishways cannot be simultaneously ideal for all species and life stages of a river reach/basin, due to the often-contrasting habitat preferences that need to be adapted to fixed interplays of hydraulic conditions. Within these limitations, however, model-based ecological pre-optimization is crucial for optimizing and deploying fishways that will guarantee suitable passage routes for a wide range of species and life stages, ultimately restoring the hydromorphological and ecological connectivity of dammed rivers.

Schizothorax prenanti swimming behavior in response to different flow patterns in vertical slot fishways with different slot positions

Fish swimming behavior is a critical parameter for the design of vertical slot fishways. Although Schizothorax prenanti is a significant reproductive potamodromous migratory fish species in the upper reaches of the rivers in Southwest China, its swimming behavior has not been extensively researched. Therefore, in this study, a comparative experiment was conducted in vertical slot fishways to analyze the behavior of Schizothorax prenanti in response to different flow patterns, with respect to different slot positions. The experimental model was designed with a length scale of 1:4, and a method for selecting the appropriate fish size in the scaled physical model was proposed. Based on these experiments, it was found that the typical upstream trajectories of Schizothorax prenanti are traceable to the sidewall of the pool, which are characterized by low velocity and turbulent kinetic energy (TKE). The hydraulic variables exhibited an asymmetric distribution within the vertical slot, and the fish were found to pass through the area with the lowest velocity and TKE. A flow pattern with a guide wall length-to-pool width ratio of P/B = 0.25, in which Schizothorax prenanti can immediately find the sidewall, is suitable for fish migration. Therefore, this is the recommended value for the construction of effective vertical-slot fishway structures.

Role of Transient Characteristics in Fish Trajectory Modeling

In this experiment, we analyzed live fish (silver carp) trajectories recorded in an experimental vertical-slot fishway. Combined with a numerical simulation, we demonstrated that randomness shown in fish trajectories might not merely be attributed to the fish’s random choices in its swimming, but could also be a consequence of adaption to the bulk unsteady turbulent flow structures. Simple superposition of a fish trajectory on the time-averaged flow field obtained either by interpolating on discrete point measurements or numerical simulation data is not an ideal method for description of fish movement. How to model the fish paths in transient flow and the necessity of simultaneous recording of the flow field and the fish locomotion are challenging topics. We also discussed the possible integration of currently existing methods to promote the development of fish trajectory modeling.

Effect of body length on swimming capability and vertical slot fishway design

A dam will be built in the upper Han River, China, disrupting fish migration and gene exchange, and a vertical slot fishway will be constructed to mitigate the impacts. Of the forty-two local species identified, eight were selected as target species, based on migration, habitat suitability, protection class, economic value and historical status. Fish swimming capability and the effect of body length on swimming ability were assessed by measuring induced flow velocity (Uind), critical swimming speed (Ucrit), and burst speed (Uburst) by stepped velocity tests in a modified Brett-type swimming respirometer. The research led to two primary findings: (1) The absolute values (m/s) of Uind, Ucrit and Uburst tended to increase with body length, while relative values (bl/s) tended to decrease. (2) The effective flow velocity for 90% of the tested fish (EF90) was used to set engineering design criteria for flow velocity; Uind-EF90 = 0.17 m/s, Ucrit-EF90 = 0.59 m/s, and Uburst-EF90 = 0.94 m/s. According the three EF90 values, literature references, fishway guidelines and design codes in China, the recommended velocity criteria for the vertical slot fishway are as follows: entrance velocity, 0.35–0.47 m/s (0.6–0.8 Ucrit-EF90); pool velocity, 0.17–0.59 m/s (from Uind-EF90 to Ucrit-EF90); vertical slot velocity, 0.86–0.94 m/s (from lowest Uburst to Uburst-EF90); exit velocity, > 0.17 m/s (Uind-EF90). The results of this study add to existing knowledge on the effect of body length on swimming ability and improve vertical slot fishway design.

Evaluation of the drag coefficient of a fully submerged body using SPH

The open-source software DualSPHysics was used so set up a three-dimensional model of a free-surface water flow in a narrow horizontal open channel with a rectangular cross section, and to determine the forces acting on various submerged fixed objects. Simulations included a sphere, a cube, and a composite capsule-like object made out of three basic bodies. Objects were located in the channel's central axis at various distances from the channel bed, and were exposed to various flow velocities. Calculating the hydrodynamic forces acting upon the objects resulted in longitudinal forces increasing with the square of the velocity, transverse forces equal to zero, and constant vertical forces. The calibrated and validated model was used to evaluate the drag coefficient of the submerged composite capsule-like object. This research reveals certain limitations of DualSPHysics and facilitates future improvements of the code and the upgrade of studies related to vertical slot fishways.

Quantitative assessment of fish passage efficiency at a vertical-slot fishway on the Daduhe River in Southwest China

Fish passage facilities are constructed to enable fish to pass anthropogenic barriers such as dams though their efficiency varies across species and location. There are a number of studies that assess the efficiency of fish passage facilities, yet rarely have such assessments been conducted in Asia. We conducted one of the first quantitative assessments of the efficiency of a vertical-slot fishway in Asia on the Daduhe River in Southwest China. Quantitative assessment of fish passage efficiency was conducted using a combination of methods, including fish sampling, video recordings and a Passive Integrated Transponder (PIT) system for tracking individually-tagged fish (N = 69 of 6 species). Fish sampling revealed 40 species assembled downstream of the dam. Fish captured closer to the fishway tended to be larger than fish caught more distant from the fishway. Half of the fish species observed downstream of the fishway were also observed at the entrance to the fishway (i.e. 153 individuals across 20 species). Video records revealed that overall passage rates were 71.2% based on the number of fish observed at the exit of the viewing chamber relative to that observed passing the entrance viewing chamber. Most fish passed the fishway at night with peak passage occurring in June. PIT technology results revealed that passage efficiency among the six tagged species ranged from 0% to 60% (four species successfully ascended the fishway). Transit time from the fishway entrance to exit was variable both among and within species that successfully ascended the fishway (i.e. 17.9–20.3 h for Schizothorax davidi, 6.4–88.8 h for Schizothorax preuanti, 46.4 h for Silurus meridionalis, 22.1–53.9 h Semilabeo prochilus). Fishway performance varied by species such that there is evidence that the fishway may be useful for maintaining river connectivity for some species. However, passage was often restricted during periods when there was sufficient flow in the fishway. Additional research is needed to put these findings in an ecological context given the overall low number of fish that passed the dam.

A Numerical Study of Fluid Flow in a Vertical Slot Fishway with the Smoothed Particle Hydrodynamics Method

Fishways have a great ecological importance as they help mitigate the interruptions of fish migration routes. In the present work, the novel DualSPHysics v4.4 solver, based on the smoothed particle hydrodynamics method (SPH), has been applied to perform three-dimensional (3-D) simulations of water flow in a vertical slot fishway (VSF). The model has been successfully calibrated against published field data of flow velocities that were measured with acoustic Doppler velocity probes. A state-of-the-art algorithm for the treatment of open boundary conditions using buffer layers has been applied to accurately reproduce discharges, water elevations, and average velocity profiles (longitudinal and transverse velocities) within the observed pool of the VSF. Results herein indicate that DualSPHysics can be an accurate tool for modeling turbulent subcritical free surface flows similar to those that occur in VSF. A novel relation between the number of fluid particles and the artificial viscosity coefficient has been formulated with a simple logarithmic fit.

Observations of American Shad Alosa sapidissima Approaching and Using a Vertical Slot Fishway at the Head‐of‐Tide Brunswick Dam on the Androscoggin River, Maine

AbstractAmerican Shad Alosa sapidissima have historically supported an important fishery along the Atlantic coastal waters of North America. However, the construction of dams reduced populations and restricted landings. Fishways are intended to mitigate obstacles to anadromous fish migrations, but a thorough evaluation of their efficiency is warranted. We analyzed data collected from video recordings, hydropower turbine operations, and telemetry conducted by the Maine Department of Marine Resources to evaluate American Shad behavior while approaching and using a vertical slot fishway at the head‐of‐tide Brunswick Dam on the Androscoggin River in Maine. American Shad passage at the dam has been poor, ranging from 0 to 1,100 fish per year, relative to passage at other facilities in the region. Additionally, our observations indicate that there are relatively high numbers of American Shad present downstream in the river (averaging 50,000) compared with the entrance of the fishway or its pools (<8,000). On average, the rates of observed American Shad on the side of the river near the fishway entrance were significantly higher (6.5–8.6 individuals/min) when the turbine closest to the entrance of the fishway was not operating compared with when it was operating (4.1 individuals/min). Most of the radio‐tagged American Shad remained in the river below the dam or went undetected. Eleven of 57 tagged fish were detected at the fishway entrance and of those only five were detected in the lower fishway. Individuals that were detected were observed making multiple attempts at entering the fishway, but movements were restricted to the lower pools. Our results suggest that this fishway is not conducive to the passage of American Shad. Examining the relationship between hydropower operations and other environmental variables on the behavior and passage of migrating anadromous fish remain an area for further study.