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Hydraulic Calculations of a Slotted Separator Using the SSIIM Program
Analysis of the results of the hydraulic calculations of a slotted separator, allowed for changes in the separator design taking into account the reduction of flow turbulence, ensuring the continuity of water flow and sediments as well as optimal location of the slots. The separator is an important element of the installation for hydromechanical removal of sediments from the bottom of a water reservoir. Tests were carried out on the physical and mathematical model. Hydraulic calculations and numerical simulations were carried out using the SSIIM (Simulation of sediment movements in water intakes with multiblock option) program. The program enables three-dimensional analysis of flows and transport of sediments in rivers and canals by solving the Navier-Stokes equation and the turbulent model k-. A number of numerical experiments of the separator work were carried out for various design solutions regarding the geometry of the inlet and outlet channels and their connection with the chambers as well as slots system. The numerical simulations and conducted research on a physical model, allowed to develop an optimal solution.
Wpływ zbiornika retencyjnego Jeziorsko na układ dna i transport rumowiska na odcinku od zapory czołowej do Uniejowa
The Influence of Temperature on Rheological Parameters and Energy Efficiency of Digestate in a Fermenter of an Agricultural Biogas Plant
This investigation specifically aims to enhance the understanding of digestate flow and mixing behavior across typical temperatures in bioreactors in agricultural biogas plants, facilitating energy-efficient mixing. Experimental tests confirmed that digestate exhibits non-Newtonian characteristics, allowing its flow behavior to be captured by rheological models. This study validated that digestate rheology significantly varies with temperature, which influences flow resistance, mixing efficiency and overall energy requirements. Two rheological models—the Bingham and Ostwald models—were applied to characterize digestate behavior, with the Ostwald model emerging as the most effective for Computational Fluid Dynamic (CFD) simulations, given its balance between predictive accuracy and computational efficiency. Specifically, results suggest that, while three-parameter models, like the Herschel–Bulkley model, offer high precision, their computational intensity is less suitable for large-scale modeling where efficiency is paramount. The small increase in the accuracy of the shearing process description does not compensate for the significant increase in CFD calculation time. Higher temperatures were found to reduce flow resistance, which in turn enables increased flow rates and more extensive mixing zones. This enhanced mass transfer and mixing potential at elevated temperatures are especially pronounced in peripheral areas of the bioreactor, farthest from the agitators. By contributing a model for rheological behavior under realistic bioreactor conditions, this study supports the optimization of energy use in biogas production. These findings emphasize that temperature adjustments within bioreactors could serve as a reliable control strategy to maintain optimal production conditions while minimizing operational costs.
Application of Multi-Criteria Analytic Methods in the Assessment of the Technical Conditions of Small Hydraulic Structures
Increasing water demand, combined with unfavourable climate change, creates a need for well-thought-out water management. Such goals are realised thanks to appropriate hydrotechnical infrastructure, the efficiency and functionality of which depend on its technical condition. In the literature, there is no method for the assessment of the technical condition of small damming structures, including sluice gates. The aim of this article was to present the possibility of using the multi-criteria AHP decision support method to assess the technical condition of small damming structures. The assessment included both concrete elements (spillways, abutments, and apron) and steel elements (gates and hoisting equipment). The analyses considered the effects of growing vegetation, the condition of concrete surfaces (e.g., cracks, cavities, exposed rebar) and steel elements (corrosion, deterioration). A hybrid method was used to study the assessment of the technical condition of water structures. It consisted of a modified Zawadzki’s method and weights which were determined by different groups of respondents with industry backgrounds (university students and experts) using the AHP method. The obtained results show that the factors related to the holes and corrosion of the gate elements had the highest value of the matrix solution vector. The last level of the tree structure indicated that the condition of the spillway and gate is the most important factor in the technical condition assessment. As the assessment considers commonly available parameters, the proposed method is universal and can be used in the assessment of other structures of this type in different regions of the world, which is important in terms of their functioning, planned repairs, and optimal use in water resource management.
Application of Physical and Numerical Modeling for Determination of Waterway Safety under the Bridge in Kaunas City, Lithuania
The main problem presented in this paper is the safety inlet navigation of the waterway below the bridge in the city of Kaunas in Lithuania. The analyzed reach is located in the Nemunas river downstream of the Kaunas dam. It is a part of the waterway E–41 leading to the Klaipeda harbor on the southern coast of the Baltic Sea. The work was initiated by the Lithuanian company UAB “Inžinerinis projektavimas” with funds from the project called European Union Trans-European Transport Network (EU TEN-T). The main requirement imposed along this reach is to keep sufficient depth even in the range of the lowest flows. The depth is sufficient if it is not lower than 1.15 m for minimum flows such as Q95% and Q95% with ice. The hydraulic conditions for maximum flow Q50%, Q5%, and Q1% are also taken into account for control because the threat of hydraulic jump generation was also noticed. The research is based on georeferenced data from public and non-public sources. The hydrologic data were received from the Lithuanian Hydrometeorological Service. The physical model was created in the Water Laboratory of the Department of Hydraulic and Sanitary Engineering at Poznan University of Life Sciences, Poland. The preprocessing of spatial data in ArcGIS 10.8.2 and rules of hydraulic similarity were implemented in the process of physical model preparation. Three experiments were conducted in the laboratory with scaled values of Q95%, Q5%, and Q1%. The measurements of the water surface and evaluations of the average velocity were used to validate the 2D numerical model prepared in HEC-RAS 6.3.1. The basic layers of the HEC-RAS model were preprocessed in ArcGIS 10.8.2 by ESRI company. The numerical model was implemented to test different values of unknown roughness of the channel bottom. The simulations were conducted for the real values of Q95% and Q95% with ice and Q50%. The results of the simulations were depth and Froude number maps. These maps were classified into zones of no risk, middle risk, and high risk. ArcGIS in the post-processing phase was applied to identify the locations of the hazards. The magnitude of risk was expressed in terms of minimum depth achieved, maximum Froude number, as well as the length of the reaches with high risk related to these two factors. The threat of hydraulic jump formation below the bridge was also noticed. Conducted results confirmed that the combination of hydrodynamic simulations and geoprocessing in the pre- and post-processing stages could be a powerful tool in hydraulic engineering analyses. Additionally, it is worth noting that numerical modeling enables a wider analysis of potential conditions than could be possible with a physical model only.
Urządzenie do hydromechanicznego oczyszczania i usuwania osadów dennych ze zbiorników zaporowych
Preparation of Samples for the Study of Rheological Parameters of Digested Pulps in a Bioreactor of an Agricultural Biogas Plant
The studies of the rheology of digested pulp from agricultural biogas plants have often been fragmentary and non-standardised due to their complexity and time-consuming nature. As a result of measurements, it was possible to develop a procedure and range of measurements for the correct determination of the parameters of the carrier substance. The applicability of the coaxial cylinder measurement system was demonstrated for assessing the rheological parameters of digested pulp from a fermenter that utilises agricultural biomass. To determine the characteristics of solid particles, the Zingg diagram was used, inter alia, allowing the comparison of particles from each fraction. The analysis of the shape and size of solid particles may help to describe the onset of motion of this phase, flow type, or sedimentation type. The authors propose a completely new research approach to obtain an appropriate, repeatable test conditions of medium, which is the carrier liquid from the biogas plant reactor. The proposed methodology and the scenario of the entire study make it possible to achieve scalable and comparable test results in any laboratory. The proposed solution eliminates the influence of most external factors on the sample and rheological measurements, and the effectiveness of the presented procedure was confirmed in tests.