Journal of the Persian Gulf (Marine Science)
Volume:3 Issue: 10, Winter 2012

Bulk carriers have an important role in international maritime transport. In this paper, we carried out a numerical study on a model of bulk carrier vessel and calculated total resistance of the model. A model of a bulk carrier vessel with length of 2.76 m, breadth of 0.403 m and draught of 0.173 m was selected for numerical modeling. Numerical work was done by commercial CFD software ANSYS FLUENT 13 based on finite volume method (FVM). Applying VOF model, FLUENT solved RANS equations and accordingly, free surface waves around vessel and total resistance were calculated. A fully structured mesh was used which generated in GAMBIT pre-processing software. Numerical solution was done for 5 different speeds from 0.2 to 0.95 m/s. Also, mesh dependency was studied by using four mesh sizes and finally, a mesh with 755,000 hexahedral cells was selected for all speeds. For verification of numerical results, experimental data from test of bulk carrier model were used. Model tests were carried out in towing tank of Galati University in Romania. Moreover, free surface waves from numerical study were compared with waves captured from model tests. The results showed that CFD results had an error up to 12 % relative to model test results and wave patterns around vessel were very similar to that of model test.

The commonly used linear k-ε turbulence model is shown to be incapable of accurate prediction of turbulent flows, where non-isotropy is dominant. Two examples of non-isotropic flows, which have a wide range of applications in marine waters, are saline water flow and the stratified flows due to temperature gradients. These relate to stratification and consequently, variation of density through vertical layers. In this paper, a nonlinear k-ε turbulence model, firstly presented by Speziale (1987) and was implemented in the existing hydrodynamic model. The energy equation has been also added and solved in the hydrodynamic model. The hydrodynamic model solves the fully nonlinear Navier-Stokes equations based on an ALE (Arbitrary Lagrangian Eulerian) description. The model is an extension to WISE (Width Integrated Stratified Environments) 2DV numerical model, originally developed by Hejazi (2002). The simulated values have been compared with the experimental data and have shown acceptable agreements. The predictions are also compared with the results of the original model employing a standard buoyant k-ε turbulence model, which showed the advantage of the new turbulence model in prediction of non-isotropic flows.

Non-breaking tsunami waves run-up on steep slopes can cause severe damages to coastal structures. The estimation of the wave run-up rate caused by tsunami waves are important to understand the performance and safety issues of the breakwater in practice. In this paper, an Incompressible Smoothed Particle Hydrodynamics method (ISPH) method was utilized for the 2DV numerical modeling of nonlinear wave run-up on steep slopes. SPH is a meshless method based on particles, which is capable of high accurate modeling of free surface flows with large deformations. In developed model, mass and momentum conservation equations were solved in a Lagrangian form using a two-step fractional method. In the first step, Navier-Stokes equations were solved to compute velocity components by omitting pressure term and in the absence of incompressible condition. In the second step, the continuity constraint was satisfied and the resulting Poisson equation was solved to calculate pressure terms. Velocity values were then corrected and surface positions were computed. In the present model, a new technique was applied to allocate density to the particles for the calculations. By employing this technique, ISPH model was stablized. The developed ISPH model was first validated by the solitary wave propagation on the constant water depth and the corresponding results showed good agreement with analytical results. The convergence of the method and the sensitivity of relevant model parameters were discussed. Then, validated model was used to study the run-up of solitary waves on steep slopes by considering a coastal breakwater for various wall steepnesses (i.e. 1:1, 2:1, 4:1, 8:1 and vertical wall).

The present research was conducted to evaluate the quality of training services in maritime training centers of Khuzestan province (including DARYAYE DOOR, SERAJ DARYA and DARYA PEIMAYE GENAVE). For this purpose, SURVQUAL model was used. The research is of descriptive-field study type for which 110 trainees of maritime training centers of Khuzestan province were selected via stratified random sampling method in 2011. The standard SURVQUAL questionnaire, including two parts of personal specifications and the quintuple dimensions of quality of training services, was applied to collect the required data. There were quality gaps in all dimensions of training services. The highest mean of quality gap was observed in the responsiveness dimension (-1.23) after which the reliability (-1.98), physical (-1.05), and sympathy (-0.98) dimensions were placed, respectively. The least mean of gap belonged to the assurance dimension (-0.88). The trainees’ expectations were beyond their perceptions of the existing situation and none of their expected dimensions of services were met.

This study was undertaken to survey impacts of bottom trawling on distribution and diversity of gastropods of the Bahrakan Fishing Area (BFA), of the northwestern coasts of the Persian Gulf. Gastropod samples were collected from depths of 6m and 10m at 18 randomly selected stations in three occasions, right before the opening of shrimp trawling seasonand two weeks and 3 months after the fishing season ended. Majority of sediments displayed silt-clay texture. Abundance, diversity, richness and evenness indices of gastropods decreased but conversely, Simpson dominant index increased in all post–season samplings compared to pre-season samplings in both depths (P<0.05). Biomass of gastropods declinedafter trawling and no recovery occurred after three months.However, the abundance of smaller gastropods increased after trawling. In both depths, Acteocina involuta was found abundantly in two weeks after trawling.Impacts of trawling were higher in shallow areas (6m depth) than that in the deeper areas (10m depth).

Caspian Sea coastline in the Mazandaran province has been altered as a result of activities of developers attracted to aesthetic and coastal recreational aspects of forest ecosystems. Advances in GIS and RS techniques, has made it possible to study the coastal areas for better management. Hence, the present study was undertaken to determine land cover changes via applying cross classification and tabulation analysis. Landsat satellite images of 1988, 2001, 2006 and 2010 were evaluated pixel by pixel. Results showed 33487 ha of forest areas had decreased and about 21367 and 13155 ha of agricultural and residential lands had increased, respectively. The greatest change in forest areas were pertaining to agricultural and residential lands (30424 and 1265 ha, respectively). In addition, 10984 ha of agricultural lands were transformed to residential areas. Extensive land use changes, inevitably contributed to increasing of soil erosion and sedimentation in the Caspian Sea watersheds, decreasing of water quality and limiting access to clean water for recreation, fishing and industry. Results of this research could be applied to better land use managing of the Caspian Sea coastline and its watersheds, impact assessment of development projects, identifying of vulnerable areas and monitoring Reducing Emissions from Deforestation and Forest Degradation (REDD).

Scombermorus commerson is one of the most important and commercial species in the Persian Gulf and Oman Sea. In order to adopt the responsible fishing patterns, it was necessary to estimate population dynamic parameters. Samples were collected randomly from five major traditional fish-landing sites in Chabahar, Jask, Bandar Abbas, Bandar Lengeh and Parsian in the north of the Persian Gulf and Oman Sea from October 2005 to September 2007. The average length of fork was 79.20 ±26.05 cm. The growth parameters of L∞ and K were 175.26 (cm) and 0.45 (1/ year), respectively. Growth performance index (ǿ) was 4.1. Total mortality, natural mortality, fishing mortality and exploitation rate were 1.98, 0.5, 1.48 (1/year) and 0.74, respectively