### فهرست مطالب

• Volume:4 Issue: 1, 2018
• تاریخ انتشار: 1397/04/20
• تعداد عناوین: 6
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• Hossein Nikroy Motlagh, Hossein M.V. Samani *, Hossein Hassanpour Darvishi Pages 1-7
One of the common concrete channels in irrigation networks is the semielliptical prefabricated channels. Manning formula is usually used to design these channels. The cross-sectional area and the wetted perimeter are required to be calculated in Manning formula. There are no analytical solutions to directly compute these parameters. Thus, numerical integration methods are inevitably used. In this paper, a wide number of various semielliptical channels are regarded and their cross-sectional areas and wetted perimeters for different depths were computed numerically to produce databases for three-dimensional curve fitting. Direct relationships for the cross-sectional area and the wetted perimeter in terms of the channels size and the hydraulic parameters were developed. These relationships were used in the design of the semielliptical concrete channels and the results were compared with the numerical ones. The results were quite close to each other which indicates that the developed direct relationships are appropriate for design purposes of semielliptical prefabricated channels.
Keywords: semielliptical, Manning formula, Numerical method, correlation coefficient
• Iraj Saeedpanah *, Arash Adib Pages 8-18
This research includes of the numerical modeling of fluids in two-dimensional cavity. The cavity flow is an important theoretical problem. In this research, modeling was carried out based on an alternating direction implicit via Vorticity-Stream function formulation. It evaluates different Reynolds numbers and grid sizes. Therefore, for the flow field analysis and prove of the ability of the scheme, the numerical solution was carried out for different values of the Reynolds numbers. Also, the behavior of the vortex flow in cavity was predicted. This research compares results of applied numerical model with the results of Chia et al. [1] and Chen & Pletcher [2]. Comparing the results with those of the benchmarks show that alternating direction implicit is an effective and suitable formulation for the solution of the NavierStokes equations.
Keywords: Alternating direction implicit (ADI), Unsteady 2, D incompressible N, S equations, Two, dimensional, Cavity, Vortex flow
• Hanifeh Imanian *, Morteza Kolahdoozan, Amir Reza Zarrati Pages 19-35
Moving Particle Semi-implicit (MPS) which is a meshless and full Lagrangian method is employed to simulate nonlinear hydrodynamic behavior in a wide variety of engineering application including free surface water waves. In the present study, a numerical particle-based model is developed by the authors using MPS method to simulate different wave problems in the coastal waters. In this model fluid and solid are treated as separate phases and governing equations of momentum and continuity are solved for them concurrently. For simulations of turbulent wavy flows, constant eddy viscosity, Prandtls mixing length theory and k-ε models were considered. In addition, higher order of MPS operators was applied to suppress numerical oscillation in comparison with previous studies. The developed method was applied to some cases, including still water reservoir, solitary wave propagation in a tank, tsunami run-up on an inclined wall and wave generation due to the landslide. Evaluation of the developed model results, in compare with data cited in the literature showed enhancement in the accuracy of the developed numerical model especially in compare with existing inviscid models. Besides, the numerical tests results have shown that applying k-ε turbulence model, have equipped MPS model with a useful, powerful and reliable tool for simulating water free surface in wave motion, wave impact and the breaking process.
Keywords: numerical modeling, Lagrangian approach, Moving Particle Semi, implicit (MPS) method, turbulence modeling, wave evolution
• Morteza Jedari Attari, Seyed Abbas Haghshenas *, Arash Bakhtiari, Mohammad Hossein Nemati Pages 36-54
The Makran Coast (Iranian Coastline of the Oman Sea on the Northern Indian Ocean) plays an important role in countrys future navigation and trade due to its accessibility. In 2014, the Iranian Makran coastline was selected by the PMO to be studied as the Phase 6 in the series of Monitoring and Modelling Studies of Iranian Coasts with all disciplines being in investigated including currents. All previously measured current data (in 2006, 2007 and 2008) along the Makran coastline showed an oscillating (reversing) alongshore currents with no detectable dominant frequency. The oscillation period of these currents varies approximately from 3 days to a week. The most significant objective of this study was to simulate the oscillating behaviour of the Makran coastal currents. In this regard, the global oceanic current pattern over the Northern Indian Ocean was simulated using a 3-dimensional non-structured model and comparisons with the data from several global resources have been made. The model was calibrated using the available vertical current profile data along the coastline.
Keywords: Ocean Currents, Circulation Patterns, Numerical Modelling, The Oman Sea
• Chonoor Abdi Chooplou, Mohammad Vaghefi *, Syyed Hamed Meraji Pages 55-74
In this paper, submerged vanes were placed at the upstream area of a bridge pier located at the 90 degree angle. Then, using the laboratory equipment, a study of flow pattern was conducted throughout the bend, specifically around the pier and submerged vanes. ADV velocimeter was incorporated in order to help measure 3D velocity components. Submerged vanes were installed at distances of 40 and 60% of the channel width from the inner bank at the upstream area of the bridge; while the distance between the vanes and the pier (5 times the pier diameter) and the distance between the vanes themselves (3 times the pier diameter) were held constant during the experiments. The results demonstrated that moving the submerged vanes towards the outer bank created a vortex at a distance of 5 times the pier diameter from the center of the pier in upstream direction at a distance of 33% of the channel width from the inner bank at a height of 6.9 cm, equal to 30 times the flow depth from the bed.
Keywords: Flow Pattern, Bridge Pier, Submerged Vanes, Velocity Contours, 180 Degree Sharp Bend
• Mohammad Mehdi Riyahi *, Mostafa Rahmanshahi, Mohammad Hadi Ranginkaman Pages 75-90
The transient flow analyzing by the frequency domain method (FDM) is computationally much faster than the method of characteristic (MOC) in the time domain. FDM needs no discretization in time and space, but requires the linearization of governing equations and boundary conditions. Hence, the FDM is only valid for small perturbations in which the systems hydraulics is almost linear. In this study, the linearization errors of the FDM applied to a reservoir-pipe-valve system (RPV) are discussed and by using the Genetic Programming (GP), some correction coefficients are defined to reduce them. By applying the correction coefficient at the opening size of the valve, the first frequency of the frequency domain method is modified. Moreover, the responses at higher-order frequencies are evaluated by some new correction factors obtained by the GP. Solving an illustrative example shows that the error of the system can be significantly reduced by using the applied correction factors.
Keywords: Frequency domain, Transient flow, Method of characteristics, Genetic programming