Simulation of the Hydraulic Performance of Parallel Pivot Weirs with Different Angles

Pivot weirs are one of the most important structures for regulating the water level in rivers and canals. These weirs are constructed with one or more gates in a row in the waterways. Changing the angle of each gate is done individually with an independent system. Based on available information, the hydraulic performance of this type of weirs (especially in several gates and different angles) in different operational conditions has not been investigated. In present study, pivot weirs with two gates are simulated using Ansys CFX software with the angles of 27.8 to 90 degree and the discharges between 40 to 130 L/s. Further, the importance of the open space between the two adjacent weirs with different angles (lack of retail wall) and its hydraulic behavior have been studied. The model was calibrated based on valid laboratory data and using the K-ϵ turbulence model.  Therefore, the weirs with equal angles were studied in the first step. In this case, the effective discharge angle coefficient was studied and its maximum value compared to the vertical angle was obtained 1.076 for the angle of 52°. Furthermore, relationships for discharge coefficient versus upstream water depth were developed. In the next step, the effective length of the crest was found to be increases by 30% under unequal angles operation and the discharge coefficient raised by 1.3 to 2.4 times. Also, it was recognized that, in case of two weirs with unequal angles, about 26% to 69% of the flow passes through the distance between the two weirs. Therefore, the performance of unequal angles operation seems to be more effective in controlling the water level and discharge in different conditions and especially in flood events

Performance Assessment of Shockwaves of Chute Spillways in Large Dams

Spillways are the most important structures of large dams that are responsible for releasing the excessive flood discharge from the reservoir. Although many studies have been performed to determine the flow characteristics over these structures, however, the available information on the shockwaves’ characteristics for spillways’ design is limited. The supercritical flow below the chute piers generates an aerated flow known as shockwaves. Due to the flow interaction with the chute piers, three kinds of standing waves just downstream of the pier, in the middle of the chute, and on the sidewalls are generated. This phenomenon affects the flow domain and its hydraulic characteristics along the chute spillway. The height of the waves increases downstream, where they hit the chute walls and reflect again into the flow to interact together again. The process repeated and intensified downstream in a lozenge shape. The height of these waves can be more than twice the depth flow and thus run over the sidewalls. This is important for the design of chute walls in chute spillways with control gates. In this study, the experimental formation of the shockwaves and their behavior along the chute and their reduction measures are presented. Experiments were conducted on a scaled physical model (1/50) of Kheirabad Dam, Water Research Institute, Iran. It was realized that apart from the geometry of piers and chute spillway, Froude number of flow and gate opening are the main effective parameters on the hydraulic performance of shockwaves’ formation and their development on gated spillways

A new species and new distribution records of Zercon C. L. Koch from Iran (Acari: Zerconidae)

A new species of the family Zerconidae, Zercon persicus sp. n., is described based on female and male morphological characters. It was collected in West Azarbaijan province (northwestern Iran). Idiosomal chaetotaxy, poroidotaxy and related notations are illustrated. The similarities and differences between the related species within the genus are discussed. Records of some other Zercon species from the province are given for the first time. http://www.zoobank.org/urn:lsid:zoobank.org:pub:3D1122C7-2B86-40D2-974E-EE69035A2413. © 2018, © 2018 Taylor & Francis

The impacts of dumping sites on the marine environment: a system dynamics approach

Abstract The various forms of anthropogenic pollution of seas and oceans have been extensively studied in recent decades. The most significant factors are the destructive environmental impacts of marine dumping sites. These sites put soil and coastline, water quality, mangroves and coral reefs, marine animals, food chains and plankton, and fishery at serious risk and alter the surrounding economic, social, and cultural conditions. The destruction of marine ecosystems by dumping sites causes severe environmental damage. With the ever-increasing anthropogenic environmental pollution of the seas and the drastic reduction in the self-purification mechanism of marine ecosystems, it is necessary to charter practical solutions with a holistic perspective and implement novel designs using system dynamics. System thinking and system analysis are essential tools in analyzing and solving important economic and management issues. System analysis investigates and evaluates the system complexities, determines the relationship between all factors, and then presents appropriate solutions to the problem. The increasing severity of the problems caused by marine dumping in recent years and the existing research gap in this area have highlighted the need for effective, comprehensive, and integrated solutions. The process of findings such solutions is critical and challenging. This study explores the most significant factors that directly and indirectly impact marine life using system dynamics

Hydrodynamic Performance and Cavitation Analysis in Bottom Outlets of Dam Using CFD Modelling

Bottom outlets are significant structures of dams, which are responsible for controlling the flow rate, operation, or removal of reservoir sedimentation. The service gate controls the outlet flow rate, and whenever this gate is out of order, the emergency gate which is located at upstream is utilized. The cavitation phenomenon is one of the common bottom outlets’ problems due to the rapid flow transfer. The present research is a numerical study of the flow pattern in a dam’s bottom outlet for different gate openings by the use of Flow-3D software and RNG k-ε turbulence model. The investigation is carried out on the Sardab Dam, an earth dam in Isfahan (Iran). The maximum velocity for 100% opening of the gate and Howell Bunger valve is about 18 m/s in the section below the gate, and the maximum velocity for 40% opening of the gate is equal to 23.1 m/s. For 50% opening of the service and emergency gate in the valve’s upstream areas, the desired pressure values are reduced. Moreover, in the areas between the two emergency and service gates, the pressure values are reduced. The possibility of cavitation in this area can be reduced by installing aerators. The flow pattern in Sardab Dam’s bottom outlet has relatively stable and proper conditions, and there are no troublesome hydraulic phenomena such as local vortices, undesirable variations in pressure, and velocity in the tunnel, and there is no flow separation in the critical area of flow entering into the branch