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

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

Modelling of mercury transport and transformations in the water compartment of the Mediterranean Sea

The Mediterranean Basin is highly heterogeneous with regard to its climatic and oceanographic properties. The appropriate approach for simulating the transport and transformations of Hg in the water compartment requires the use of a hydrodynamic model with additional modules for transport-dispersion and biogeochemistry. In this work, the PCFLOW3D model was upgraded with a biogeochemical module and used for simulation of mercury transport and transformation processes in the Mediterranean. The circulation for the four seasons due to wind, thermohaline forcing and inflow momentum of the main rivers and through the straits was calculated. The results were compared with measurements and the results of another model (POM - Princeton Ocean Model). An acceptable agreement was achieved. The seasonally averaged velocity fields obtained were used to simulate transport and dispersion of mercury. A new biogeochemical module dealing with the different mercury species: gaseous elemental (Hg0), divalent (Hg2+), and mono-methyl mercury (MMHg) in dissolved form and bound to particulate matter and plankton was introduced. Exchange of mercury at the boundaries (bottom sediment/water and water/atmosphere) and transformation processes such as methylation, demethylation, reduction and oxidation were taken into account. The transformation rates between the mercury species were described using simple equations, and thus the time and space variable reaction coefficients should be determined from in-situ measurements. Instead, machine-learning tools and classical statistical methods were used to connect the measured sets of geophysical/environmental parameters and concentrations of different Hg species. The provisional annual Hg mass balance established for the Mediterranean showed that exchange with the atmosphere is the most important source/sink of mercury for the water compartment. Therefore, the model was further upgraded with a gas exchange module for Hg0. To improve the results of the simulations the PCFLOW3D aquatic model was further linked to the RAMS-Hg atmospheric model which provided real-time meteorological data, deposition and concentrations of mercury in the atmosphere. Simulations with the integrated modelling tool were performed and the results were compared to the measurements. Acceptable agreement of the average concentrations down the water column for both total mercury (HgT) and elemental mercury (Hg0) was achieved. Agreement of Hg0 concentrations near the surface was good; thus exchange with the atmosphere can be simulated with relatively high reliability. Agreement of simulated MMHg concentrations with measurements was not satisfactory, which is probably due to poor understanding of the processes of MMHg formation and its dependence on environmental factors, which have, so far, not been taken into account in the modelling. In view of the satisfactory modelling results obtained for HgT and Hg0, a simulation of management scenarios, particularly the policy target (PoT) scenarios for 2010 and 2020, was performed. The results of these simulations were further used to establish the mass balance of HgT in the Mediterranean Sea. © 2007 Elsevier B.V. All rights reserved

3-D numerical study of a bottom ramp fish passage using smoothed particle hydrodynamics

Worldwide, the overwhelming number of man-made barriers in fluvial systems has been identified as one of the major causes of the reported staggering average declines of migratory fish. Fish passages have been shown to help mitigate such problems. Close-to-nature types of fish passages, such as bottom ramps, bypass channels, and fish ramps can be used to minimize the impact of artificial steep drops (e.g., weirs) on the migration of aquatic fauna, especially in cases of low-head barriers. This study focuses on the characterization of the flow pattern in a bottom ramp. A 3-D numerical model based on the meshless smoothed particle hydrodynamics (SPH) method was successfully validated and then employed for the simulation of turbulent free-surface flow in a straight channel with complex geometry. The effects of bed roughness, channel slope, and flow rate were quantified in terms of flow depth, velocity fields, and area velocity ratios. During the study, several new tools were developed, leading to new functionalities in pre-processing, solver, and post-processing which increase the applicability of DualSPHysics in the field of eco-hydraulics