The information about geometric properties of scour hole around a bridge pier is necessary to decide better the type and placement practice of scour countermeasures and prevent waste of economic resources. The scour hole formation and extension in uniform and non-uniform sediments are quite different. The present study aims to evaluate the effects of different sediment beds made up of mixtures of sand and gravel on the characteristics of scour holes around a single cylindrical pier for different flow shallowness. Eight laboratory tests were conducted until the quasi-equilibrium state under clear water conditions. An accurate bed surface topographic map was provided at the end of each experiment. The results showed significant surface topographic variability, and significant differences in maximum scour depths and their locations in non-uniform sediments relative to uniform sediments in the same hydrodynamic conditions. In addition, corresponding results are suitable for validating numerical models importantly with non-uniform sediments.

In regard to wide piers, the pile group rather than single pile is used frequently to bear the loading of the structure in a particular arrangement; piles group composed of only one column of piles in the flow direction has a great effect on supporting the bridge deck. In this study, local scour at a single column arrangement of the piles group made up of four rows of piles characterized by different piles spacing was studied for clear-water conditions with two flow discharges of 20 and 35 l/s (the effect of increasing the flow depth with the same flow intensity). The results indicated that an increase in the flow depth not only greatly enhanced the scour depth and the width of the scour hole. Besides, the investigation of the relative flow depth on scour extent showed the need for revision in deep water conditions, as reported in the literature. The results of the pile group experiments revealed the noticeable impacts of piles spacing on the local scour. The bigger pile spacing caused a feeble interaction of wake-horseshoe vortices, leading to a decrease of the scour depth; the separate view of the scour holes was generated at individual piles. Finally, the results were compared with commonly used comprehensive models. The findings of this study can be applied for the appropriate selection and positioning for the countermeasure of the scour at bridge piers.

The use of renewable energies including hydropower energy is growing throughout the world. Among the existing hydropower technologies, small-scale hydropower technologies are popular due to easy accessibility and availability in different locations. Recently, Archimedes Screw Turbines (ASTs) as a new technology have been considered. The main objective of this research is the structural optimization of an AST for substituting in irrigation canals instead of existing check structures. For this purpose, the AST performance model was numerically developed for screw performance optimization in MATLAB 2013a environment. The developed model was validated using experimental data. Different structural parameters were optimized to design an appropriate AST for replacing instead of check drop-1 in the east Aghili canal in Khuzestan province (Iran). The canal was simulated using the ICSS hydrodynamic model. The results of the developed model showed a good agreement with reported experimental data. The highest efficiency was obtained 90.83% for the screw length of 6m, the inclination angle of 20 degrees, and the flight number of 1 at the design flow rate. Based on the findings, the suggested system can be used instead of the canal structures without considerable change in the hydraulic and performance of the canal. (c) 2019 Elsevier Ltd. All rights reserved.

In this research, an energy harvesting system was developed for power generation using a combination of an Archimedes Screw Turbine (AST) and a solar Organic Rankine Cycle (ORC) system. An AST was numerically used and optimized for producing mechanical power as an energy harvesting technique. Different structural parameters including the screw inclination angle, number of flights and the screw length were considered. A parabolic trough concentrator was numerically modeled as a heat source of the ORC system. Two different types of absorber were considered using a smooth and corrugated tube. Different ORC working fluids were investigated in the solar ORC system including R134a, R245ca, R245fa, R152a, R113, R11, and R114b. The results of numerical modeling were validated with experimental results and good agreement was found. The results revealed that R113 at the saturated condition at turbine inlet gave the highest ORC net power, ORC efficiency, and total efficiency compared to the other investigated working fluids. The solar PTC system with the corrugated tube showed the higher ORC net power, and overall efficiency compared to the smooth tube as the PTC receiver. The highest efficiency resulted in the screw length of 1.5 m was 58.24% with inclination angle of 25 degrees and flight number of 1. Finally, the optimized characteristics of power generation system including a solar ORC system and a screw turbine (hybrid system) were presented to harvest energy. Application of the presented hybrid system is an acceptable way for increasing and optimizing the ORC power generation.

Experimental and numerical study of scouring pattern on the direct and polo-shaped groynes have been investigated in this paper. In this study, direct and polo-shaped groynes models with a length of 0.12 meter have been used in discharges of 10.5, 15, 20 liters per second in a direct flume. The results showed that the maximum scour depth formed around the groyne head of direct and polo-shaped types has increased with augmentation of flow discharge, which was 0.095 and 0.104 meter in the case of 20 L/s discharge respectively. Also, the width of scour hole was 2.25 and 2 times of effective length of the groyne in direct and polo-shaped groynes respectively. In this regards, maximum scour depth around the head of groyne was seen 0.87 and 0.79 times of the effective length of the groyne. Sand form located at downstream of the direct groyne at the distance of 0.09 and 0.15 meters from the side wall of direct groyne was stretched and extended to about 1.3 times of the channel width as well. While the length of the sand form for direct groyne was 1.15 times of the channel width. Overall, the dimensions of the scour hole around the polo-shaped groyne, was less than the direct groyne. In addition to understanding the hydraulic behaviour around the groyne, Flow3D software was used. Statistical survey of the results obtained by experimental and numerical models attested that the relative error of the numerical model could be about 20%, which shows an appropriate performance of using Flow3D for predicting the maximum scour depth.