The Urmia Lake has distinctive nature, hydrodynamic and environmental properties that single out that from the other lakes in the world. Construction of Shahid Kalantari causeway can cause significant effects on natural regime of the lake. It may affect on environmental biology, hydraulic, water circulation regime and … . This paper deals with hydrodynamics of the lake. Two-dimensional surface simulation has been done with MIKE21 program. Flow regime and relative effects of parameters influencing that has been investigated. Results from this model when simulating normal condition, has been found to present a good correlation with field data as level fluctuations and velocity range. For that it seems that using 2D model for hydrodynamic is suitable but calibration with field data is needed for its approval. This model shows that the wind input as the main environmental parameter influencing the flow regime in the Lake and for that it is important object for defining design parameters.

In this paper, the local scour process around pipelines due to steady currents has been investigated from different points of view using the numerical and physical models. In order to calculate the maximum scour depth under the pipe, a mathematical model based on the two-dimensional Laplace equation has been developed and the scour process on the 2D x-z vertical plane has been simulated, with the finite volume method being used to discretize the governing equation. In the developed numerical model, an equivalent boundary calculated using the Newton-Raphson iteration method, has been used to determine the deformed bed profile due to scour resulting from the subjected forces on the sediment particles on sea bed. In the physical models, emphasis has been focused on the effects of different parameters such as pipe diameter, water depth, velocity of flow and the interaction of the parallel pipes on local scour process. Finally, the numerical model results have been compared with the results obtained from the physical model and the other experimental data.

In this paper, the flow pattern around the perpendicular and inclined groynes were simulated in three-dimensional using the Fluent software, which solves the flow equations using the finite volume method and cell-center scheme. The prismatic grids were used to descretize the computational domain. The perpendicular groyne was first investigated to verify the model results and the inclined groyne with to the flow direction was then considered. From the available turbulence models in the software, the two equation turbulence model was used in this research study. In order to include the free surface effect, the rigid-lid and volume of fluid schemes were used. The result of the latter scheme showed good agreement with the experimental results.

The estimation of wave loads on very large flouting structure is usually done by an empirical or a computational approach. The computational approach usually assumes two types. Some use the Laplace equation or potential flow and some take the Navier-Stokes equation or viscous flow analysis. In this study, the interaction between wave and elastic plate is investigated by using viscous flow assumption. It is coupled with the elastic plate equation. Numerical solution is carried out with finite difference method in form of upwind scheme. The displacement of elastic plate is simulated numerically. Numerical results are compared with the numerical results of Basirat Tabrizi and Kouchaki Motlaq for potential flow and with the numerical results of Ohkusu and Namba and experimental results of Kashiwagi for viscous flow. The results show that viscous flows have more damping effect on displacement of elastic plate than non-viscous flows.

Investigation of the flow pattern around bridge piers is of utmost importance because of its great effect on destruction of the piers. Despite the hydrodynamical and structural values of designing sections causing minimum turbulence against the flow passing the bridge pier, a review of the literature shows that investigation of the flow pattern around bridge piers with varying section has not been studied by the researchers. In this research study, a three-dimensional numerical model has been used to study the flow field around a cylindrical and four conical piers of different slopes. The computational domains were first discretized using GAMBIT and then analyzed by FLUENT. Finally, the flow pattern and bed shear stress around the piers have been investigated and the relevant comparisons have been made. Numerical model results show that increment of the pier’s slope has a great effect on reducing turbulence of the passing flow and thus lessening the bed shear stress around the pier.

Wave diffraction is a very important phenomenon in marine engineering and several models have been developed for its simulation. The new version of SWAN, a third generation spectral model, includes an approximation to wave diffraction. The approximation is based on the mild-slope equation for refraction and diffraction, omitting phase information. The objective this paper is to evaluate the performance of a numerical model. To do so, the propagation of unidirectional and multi-directional irregular waves through a breakwater gap is simulated to validate the model. It is desired to evaluate the dependence of the diffraction coefficient (Kd) and incident wave parameters. Wave parameters are directional spreading parameter (S) and peak enhancement factor (γ) of JONSWAP wave spectrum and direction of incident wave. The model is also tested using two different lengths of breakwater gap. A laboratory data set is used for the evaluation of SWAN. The comparison shows a good agreement between the model outputs and the experimental data. The average scatter index is about 5% for Kd and The average of Bias parameter is about -0.05. This shows that the model, in most cases slightly under estimates the diffracted wave height. It is also found that the wave directional spreading parameter is more effective compared to the peak enhancement factor on the wave diffraction. The calculated results indicate that, this numerical model is applicable to the real engineering problems.

A number of experiments have been carried out in the current paper to investigate the effect of adding a longitudinal impermeable blade beneath the offshore pipelines on decreasing the scour around them. The main aim of this study was to reduce the hydraulics gradient beneath the pipe so that its magnitude recedes from the critical hydraulics gradient and therefore delays the onset of scour phenomenon or stops its process at all. Three pipes of different diameters were selected for the physical models of this study. Each pipe was tested using six blades with different relative widths. Also, a series of numerical simulations have been done using Flow3D software in which the similar boundary conditions as used for the physical models were applied. In both experimental and numerical investigations the reference sample that was an unprotected pipeline was first tested. Then blades with different relative widths (e.g, 0.05, 0.10, 0.15, 0.20, 0.25, 0.50) were added to the beneath of the pipeline and their performances were tested and analyzed against scour. The experimental and numerical results were in good agreement and they indicate a remarkable reduction in scour depth when a blade with the distinctive relative width was sticked to the pipeline.

The aim of this study was to design and develop a three-dimensional numerical baroclinic model with the ability to accept complex bottom topography and variable wind in space and time to investigation wind-induced current at 10 layers in the south Caspian Sea. The finite difference method Was used for numerical solution of the primitive equation in spherical Sigma pressure coordinate system on staggered modified Arakawa C grid. The wind data available from ECMWF ERA 15 data sets and the bathymetric data obtained from the JEBCO data sets with spatial resolutions of 0.125^o were utilized in the model. The result shows there are found a cyclonic eddy in middle of the basin and an anticyclonic current in close of the western coast that continued over the year. In addition, the circulation in the extensive continental shelve near the eastern coast is especially sensitive to wind direction and speed Also the maximum of surface current always take place in this area.