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Hydrodynamic and ethohydraulic analysis of a water vortex power plant for assessment of fish passability
Published in Wim Uijttewaal, Mário J. Franca, Daniel Valero, Victor Chavarrias, Clàudia Ylla Arbós, Ralph Schielen, Alessandra Crosato, River Flow 2020, 2020
J. Stamm, N. Müller, Ch. Jähnel, F. Wagner, P. Warth
After the use of biomass, hydropower contributes the largest share of renewable energies worldwide. In the small hydropower sector, the potential for expansion is recognized particularly in the modernisation and reactivation of existing plants, with special attention being paid to nature conservation and water ecology. The transverse structures required for dam construction basically act as obstacles to the passage of fish and sediments. The water vortex power plant, a hydropower plant patented for the first time by Brown (1968) has a rotating flow regime (Rankine vortex) with a vertical-axis, slowly rotating Francis-type turbine positioned in the vortex core. Field surveys at facilities in Switzerland and Austria describe the WVPP may cause significant constraints onto fish migrating upstream (Kirchhofer and Breitenstein 2016; Kirchhofer et al. 2017), whereas investigations at a WVPP at the river Wesenitz in Saxony, Germany (Zinn 2014; Zuchowski 2015), state that the plant can be passed upstream by some fish species. As part of a BMBF-funded research project, it had to be clarified to what extent this type of facility enables fish to pass through, what damage rate can be expected in the passage and to what extent the fish would avoid this facility. To this end, hypotheses were postulated (see 1.2) and quantified statements were formulated based on scientific experiments. Since there is currently no design information available in the technical literature for fish ladders with rotating elements, the flow conditions should be evaluated according to DWA M-509 (2014) (DWA - German Association for Water, Wastewater and Waste).
The bio-hill chart of a Kaplan turbine
Published in Journal of Ecohydraulics, 2022
P. Romero-Gomez, M. Lang, S. Weissenberger
Hill charts can be calculated during the design process from flow simulations of the machine (Liu et al. 2009; Vu et al. 2011), from performance runs in physical models in test rigs (Aggidis and Židonis 2014) and from field data collected in prototypes (Gordon 2001; Cote and Cloutier 2010). They are used for defining cavitation-free operating zones, documenting shifts in efficiency after years of operation and estimating optimal turbine refurbishment times, to list only a few applications. Regarding the present work, a hill chart sets the stage over which the biological performance assessment (BioPA) of the turbine can be surveyed and realistically observed for increasing fish survival rates by means of operation. Previous studies have conducted simultaneous evaluations of hydraulic performance and biological effects, e.g., for correlating fish survival with turbine efficiency in a prototype Francis turbine (Cramer and Oligher 1964), for developing the “fish handling performance” for fish collisions in a pump design (Van Esch and Spierts 2014), for assessing fish-related flow characteristics of a vortex power plant (Müller et al. 2018), and for evaluating mortality rates of adult European eel through a bulb-type turbine (Klopries and Schüttrumpf 2020). This work undertook a simultaneous, integrated evaluation of hydraulic and biological performance of a Kaplan unit over the entire range of operations.
Numerical Investigation of Natural Convection and Irreversibilities between Two Inclined Concentric Cylinders in Presence of Uniform Magnetic Field and Radiation
Published in Heat Transfer Engineering, 2022
Ahmad Hajatzadeh Pordanjani, Saeed Aghakhani
Figure 10(a)–(c) shows Num, Stot, and the Be for at different Ha and Ra. The buoyant force increases in the enclosure by increasing the Ra. The increased buoyant force amplifies the NF flow and vortices, resulting in increased heat transfer and average Nu. Consequently, the higher the Ra are (e.g., 106), the higher the Nu are, and the lower the Ra are (e.g., 103), the lower the Nu are. On the other hand, as the Ha increases, the Lorentz force increases that in turn leads to weakening NF flow, reduced buoyancy force, and reduced vortex power; as a result, the heat transfer decreases by increasing Ha. The changes in Ha are significant at higher Ra because it can reduce the buoyancy force considerably. While it has little effect in lower Ra for which the heat transfer is high, while increasing Ha decreases it. Moreover, in the enclosure rises as the Ra rises, and an increase in the Ra significantly rises the velocity and temperature variations, ultimately leading to a rise of As the Ha raises, however, the decreases due to a decline in the temperature and velocity gradients. The effect of Ha on the flow pattern is the same as the temperature and . Although raising the Ra decreases the Be, a rise in the Ha differently impacts the Be at various Ra, but mostly increases the Be.
Numerical analysis of the compromise between power output and fish-friendliness in a vortex power plant
Published in Journal of Ecohydraulics, 2018
Stephanie Müller, Olivier Cleynen, Stefan Hoerner, Nils Lichtenberg, Dominique Thévenin
In principle, the “Fish-Friendly Weir” is a vortex power plant (VPP), installed as a by-pass system to a dam or classical weir, and which is intended to permit two-way fish migration. It consists of a vortex pool where a strong free-surface vortex develops, in the centre of which a Francis-like turbine is located. The water leaves the pool through an orifice at the bottom, and flows back into the river through an outlet channel. The turbine geometry, rotation speed, and clearance, are all chosen with fish migration in mind, taking into account the characteristics of the local fish species.