Ljubljana, Slovenia
Ljubljana, Slovenia

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Bombac M.,Institute for Hydraulic Research | Novak G.,Institute for Hydraulic Research | Mlacnik J.,Institute for Hydraulic Research | Cetina M.,University of Ljubljana
Ecological Engineering | Year: 2015

Fishways are of great ecological importance and have been the focus of numerous studies. However, many fishways remain operating at an unsatisfactory level. Furthermore, field measurements of flow properties in effective fishways remain surprisingly rare compared to the number of various numerical and physical hydraulic models. The purpose of the research was to conduct extensive field measurements of the flow in an effectively operating vertical slot fishway (VSF), and to use the findings to calibrate and verify the depth-averaged two-dimensional (2D) numerical hydraulic model PCFLOW2D. Flow velocities were measured using a reliable 3D acoustic probe. Measured velocities were up to 50% larger than values calculated from an equation proposed in recent literature, but in accordance with results of our simulations. PCFLOW2D proved to be a useful tool for modeling fishway flow and could be used in similar hydro-environmental problems. © 2015 Elsevier B.V.

Bombac M.,Institute for Hydraulic Research | Novak G.,Institute for Hydraulic Research | Rodic P.,Institute for Hydraulic Research | Cetina M.,University of Ljubljana
Journal of Hydrology and Hydromechanics | Year: 2014

This paper presents the results of an experimental and numerical study of a vertical slot fishway (VSF). A 2-D depth-averaged shallow water numerical model PCFLOW2D coupled with three different turbulent models (constant eddy viscosity, Smagorinsky and k-ε) was used. A detailed analysis of numerical parameters needed for a correct simulation of the phenomenon was carried out. Besides the velocity field, attention was paid to important hydraulic parameters such as maximum velocity in the slot region and energy dissipation rate ε in order to evaluate the performance of VSF. A scaled physical hydraulic model was built to ensure reliable experimental data for the validation of the numerical model. Simulations of variant configurations of VSF showed that even small changes in geometry can produce more fishfriendly flow characteristics in pools. The present study indicates that the PCFLOW2D program is an appropriate tool to meet the main demands of the VSF design.

Muller M.,DHD Ltd | Novak G.,Institute for Hydraulic Research | Steinman F.,University of Ljubljana | Rak G.,University of Ljubljana | Bajcar T.,University of Ljubljana
Strojniski Vestnik/Journal of Mechanical Engineering | Year: 2015

Bottom-hinged flap gates on side weirs are often used for the regulation of flow diversion in case of water abstraction for a variety of needs. In this study, a new equation for the discharge coefficient of a bottom-hinged flap gate on a side weir was proposed on the basis of discharge measurements. The equation was divided into two parts. The first part covers the impact of the sharp-crested side weir and the second the influence of the position and the width of the flap gate. In this manner, the discharge coefficient can be calculated with other authors' equations for a sharp-crested side weir, which then must be multiplied by the new proposed coefficient. Very good agreement was found between the obtained discharge coefficients and the one calculated with the proposed equation. Furthermore, the results were compared with the equations of other authors for the discharge coefficients of sharp- And broad crested side weirs. The agreement was found to be very good. Additionally, measurements of water levels along the edge of the flap gate and measurements of the velocity field were carried out with a computer-aided visualization method. From these measurements, it was possible to show that the contraction of the water jet varies with the gate-opening angle. It was also found that the side weir with a flap gate has the most favorable hydrodynamic shape around the gate-opening angle of 33°, where the discharge coefficient reaches its maximum. © 2015 Journal of Mechanical Engineering. All rights reserved.

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