Simulação numérica 3D do escoamento em escadas para peixes com ranhura vertical : validação do modelo e caracterização do escoamento

Vertical slot fishways allow energy dissipation as a function of the pool, longitudinal slope, baffle and vertical slot design. The mean and turbulent flow patterns in these structures must be compatible with the fish target. The design of these structures is commonly based on previous successful fishways as well as simplified theoretical equations and empirical relationships. To aid in the design of these structures, a three-dimensional hydrodynamic model was used to simulate the flow, and experimental studies were used to validate the model. The mean velocities, pressures and parameters indicative of turbulence were analyzed. The maximum flow velocities were up to 32% higher than the values obtained using a simplified theoretical equation. The evaluation of the volumetric dissipated power indicated that the mean value for the pool was lower than 150 W/m3; however, analysis of the spatial distribution showed that in some areas, the values can exceed 1000 W/m3. The results indicate that the numerical simulation was able to adequately represent the flow considering the computational cost involved. Accordingly, it can be used as a complementary tool for the design of new fishways and for the analysis of modifications in existing ones.As escadas para peixes com ranhuras verticais permitem que ocorra a dissipação da energia do escoamento em função da forma da bacia, dos defletores, da declividade longitudinal e da largura da ranhura vertical. Estas estruturas devem apresentar padrões médios e turbulentos do escoamento compatíveis com os peixes que irão transpô-la. Tipicamente a concepção das escadas para peixes é baseada na utilização de geometrias empregadas com sucesso em situações anteriores e a estimativa das características do escoamento através de equações teóricas simplificadas e relações empíricas. Para contribuir na concepção dessas estruturas, foi utilizado um modelo hidrodinâmico tridimensional para simular o escoamento e estudos experimentais para validar o modelo. Velocidades médias, pressões e parâmetros indicativos da turbulência foram analisados. As velocidades máximas do escoamento foram até 32% superiores aos valores obtidos utilizando uma equação teórica simplificada. A avaliação da potência dissipada por unidade de volume indica que o valor médio para o tanque é inferior a 150 W/m3, no entanto, a análise da distribuição espacial desta grandeza no tanque, mostra que valores pontuais podem ultrapassar 1000 W/m3. Os resultados indicam que a simulação numérica foi capaz de representar de forma adequada o escoamento, considerando o custo computacional envolvido e pode ser utilizada como uma ferramenta complementar para o projeto de novas escadas para peixes e para a análise de modificações em estruturas existentes

Turning pools in stepped fishways: Biological assessment via fish response and CFD models

Producción CientíficaWith the aim of building more compact fishways and adapting them to field conditions to improve their location by fish, it is common to use turning pools, reducing the longitudinal development of the construction. However, depending on their design, turning pools may affect the hydraulic performance of the fishway and consequently the fish passage. To study these phenomena, turning pools in a vertical slot and in different configurations of submerged notches with bottom orifice fishway types were assessed. Both types of fishways were studied using numerical 3D models via OpenFOAM, a computational fluid dynamics software, in combination with fish responses, assessed with PIT (Passive Integrated Transponder) tag telemetry for three different species of potamodromous cyprinids in several fishways. Results show differences between the hydrodynamics of straight and turning pools, with lower values in the hydrodynamic variables in turning pools. Regarding fish behavior, the ascent was slower in turning pools but with no effect on passage success and without being a problem for fish migration. This information validates the use of turning pools as a key design component for fishways for studied species.Ayudas Torres Quevedo - (grants PTQ2018-010162 and PTQ2016-08494)Unión Europea H2020 - (grant 727830

Mathematical modeling of the flow field in fish-passes

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Υπολογιστική Μηχανική

Modelización hidráulica de pasos para peces ante diferentes escenarios hidrodinámicos

Los pasos para peces son estructuras que permiten la libre circulación de los peces en los obstáculos transversales de los ríos (e.g. presas, azudes, estaciones de aforo, etc.). A pesar de que se tratan de una solución atractiva y bastante eficaz para recuperar el libre movimiento de los peces, son muy sensibles a las variaciones de caudal que se producen en los ríos, y su funcionamiento puede verse fácilmente alterado, especialmente marcadas en regiones mediterráneas. Esta tesis se centra en el estudio hidráulico de pasos para peces, estableciendo un método general que permite su modelización hidráulica ante los diferentes escenarios hidrodinámicos que se pueden der en los ríos. Con ello se logrará diseñar pasos para peces que funcionen en un periodo temporal mayor y así asegurar la migración de los peces a lo largo del todo el ciclo hidrológico de los ríos.Departamento de Ingeniería Agrícola y ForestalDoctorado en Conservación y Uso Sostenible de Sistemas Forestale

Hybrid Investigation on the Hydraulic Performance of a New Trapezoidal Fishway

The current study presents a new type of vertical slot pass. The main difference of this trapezoidal fish pass compared to the standard design of a vertical slot pass remains in the separation of the pools into two zones: the migration corridor and the energy dissipation zone. The structure is first investigated in a physical model to optimize the training walls and slot geometry in order to avoid recirculation of the flow. Velocity and flow depth data from experimental flow measurements is later compared to the three-dimensional numerical model which provides a deeper insight into the flow field. The proposed design is found to avoid large vortexes within the migration corridor. Moreover, uniform flow conditions are also found in the energy dissipation zone, thus providing an alternative corridor for fish passage

Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot

This article belongs to the Special Issue "Fish Passage at Hydropower Dams". Further information available online: https://www.mdpi.com/journal/water/special_issues/fish_passage_hydropower_da

Interdisciplinary design of a fish ramp using migration routes analysis

The study presents several steps of a fish ramp geometry optimization performed with a 3D numerical model DualSPHysics, which is based on the smoothed particle hydrodynamics (SPH) method. The optimization process led to the design of a bottom ramp that is capable of providing suitable conditions for the migration of target fish species (Salmo truta, Phoxinus phoxinus, Cottus gobio, and Eudontomyzon vladykovi). Migration routes were determined as complex 3D volumes of fluid according to the simulated velocity field in various steady flow conditions. Including three categories of potential migration zones (rest, effort, and limit zones), migration routes were quantified in high detail in terms of the size and position of each zone, and in terms of the distance from a given fluid part to the nearest rest zone. The interdisciplinary approach of this study also led to the development of new tools for the DualSPHysics model, specifically suited to improve functionality in eco-hydraulics research. Fishway Ramp River restoration Smoothed particle hydrodynamics DualSPHysicspublishedVersio

Modelling nature-like fishway flow around unsubmerged obstacles using a 2D shallow water model

n the scope to create efficient nature like fish ramps using large-scale roughness elements, the present study is an audit of modelling such complex 3D free surface flows using an industrial 2D code solving shallow water equations. Validation procedure is based upon the comparison between numerous experimental measurements and numerical runs around large-scale roughness patterns disposed on the flume bottom in order to determine what 2D reliable numerical results can be expected. In this paper, we focused on cases of unsubmerged obstacles. The results demonstrate that 2D shallow water modelling using an industrial code such as TELEMAC-2D can be a convenient way for the hydraulic engineer to help design a nature-like fishway. This article emphasizes the limitations due to 2D depth integration of velocities and turbulence modelling and gives the domain of validity of the method

Flow, force, behaviour: assessment of a prototype hydraulic barrier for invasive fish

Migration barriers being selective for invasive species could protect pristine upstream areas. We designed and tested a prototype protective barrier in a vertical slot fish pass. Based on the individuals’ swimming responses to the barrier flow field, we assumed this barrier would block the ascension of the invasive round goby, but allow comparable native species (gudgeon and bullhead) to ascend. The barrier was tested in three steps: flow description, quantification of forces experienced by preserved fish in the flow field, and tracking the swimming trajectories of ca. 43 live fish per trial and species. The flow and the forces were homogenous over the barrier, though gudgeon experienced significantly smaller forces than round goby or bullhead. The swimming trajectories were distinct enough to predict the fish species with a random forest machine learning approach (92.16% accuracy for gudgeon and 85.24% for round goby). The trajectories revealed round goby and gudgeon exhibited increased, but varied, swimming speeds and straighter paths at higher water discharge. These results suggest that passage of round goby was prevented at 130 L/s water discharge, whereas gudgeon and bullhead could pass the barrier. Our findings open a new avenue of research on hydraulic constructions for species conservation