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Trash-racks provide protection for hydraulic turbines by blocking entrance of large debris that could damage turbine parts. Trash-racks also help reduce fish injuries and mortality caused with fish entrapment in turbine. Installation of trash-racks is necessary, but causes inevitable head losses that decrease water turbine energy production. With increasing ecological concerns different bar-rack configurations are examined to provide better fish protection, mostly not considering head losses. Experimental results of head losses caused by trash-racks found in literature are conducted on scaled models due to experiment facility limitations while number of investigated configurations is limited with cost of production. Most head loss equations derived from experimental results are valid only in specific range of parameters. Considering these limitations, numerical simulations would enable investigation of a large number of trash-rack combinations, where simulations can be conducted for turbine intake geometries made in full scale. In this work numerical simulation results will be compared with experimental results from literature. Geometry, mesh and simulation parameters will be investigated, considering influence on simulation results agreement with experiment. Guidelines for numerical simulation setup will be provided for future work where investigation of trash-rack configurations that are not yet covered in literature can be conducted. [ABSTRACT FROM AUTHOR]

Water quality control is of great importance. Since water is being distributed through large complex pipe networks both hydraulic and water quality analysis of these systems are conducted with computer engineering programs. Pipe networks consist of various elements that influence fluid flow and it is important to understand their impact on complex phenomena like mixing. Computer programs simplify mixing effects at junctions and they lack data to fully describe the nature of mixing. Experimental methods are used to provide additional parameters that would improve the results of computer simulations that would provide more accurate prediction of water and pollution transport through pipe systems. In this work, an experimental methodology is presented which could be used to observe the influence of distances between two tee-junctions and different inflow rates on mixing. Also, data gathered from experiment can provide more accurate mixing parameters for improvement of computer simulations. [ABSTRACT FROM AUTHOR]

A study of groundwater quality at a particular well field near Varaždin, the north-western part of Croatia is presented in this paper. Experimental date are collected for the period of 11 years and nitrate concentration annual average for each well and piezometer are calculated. The Varaždin well field is out of production for decades because of the high nitrate pollution levels in groundwater. The well field is surrounded by agricultural fields and urban area. In order to determine a spatial nitrate concentration change, eight arbitrary starting points are set and distance to each of the wells is determined. Eight directions of the nitrate pollution gradient are analysed and principal direction is detected pointing to the area where probable pollution source is to be found. The results show a decrease in nitrate concentration in the southwest - east direction at the wellfield area. The principal nitrate concentration gradient is compared to the groundwater flow direction in the area. The possible area of continuous contamination, possibly by agricultural reasons is determined as a first step to remedy this public health problem of the highest priority. [ABSTRACT FROM AUTHOR]