فصلنامه علوم و فناوری دریا
سال سیزدهم شماره 49 (بهار 1388)

Interceptors are used as a new means to control trim and equilibrium of high speed vessels. This device is placed vertically at stern towards vessel bottom and despite of its small size is efficient and useful. Its effect on the pressure distribution in the vessel bottom causes coincidence of mass and pressure center and then controlling the trim. In this study hydrodynamic performance of a flat plate with and without interceptor is calculated according to CFD methods. The results contain flow distribution of vessel bottom, pressure distribution and calculation of lift and drag.

Study of coastal landforms of Hormozgan province can be effective in integrated coastal zone management. Recognition of coastal landforms in Hormozgan province shoreline is necessary, because of their importance and extent. Correct planning in coastal zones, can prevent from detriment that is reached to natural resources and it is a way to access sustainable development. This present research is proceeding to relation between coastal landforms, coastal types and living beings. Because of this species is adaptive to particles size and particular landform in coasts, it is possible to determine the environmental sensitivity of coastal landforms. In this research, Used from satellite data (IRS-PAN) and then classified of coastal landforms to spit, tombolo, lagoon, creek, estuary, barrier island and etc. on the basis of the findings of this research, about 33.56 percent of the study length has been identified as sandy beach, 23.99 percent as tidal flat, 10.18 percent as mixed beach, 4.78 percent as barrier island, 0.96 percent as tidal island, 2.04 percent as bay, 0.85 percent as cliff, 0.22 percent as cove, 1.93 percent as creek, 4.16 percent as delta, 0.17 percent as estuary, 0.19 percent as estuary-creek, 0.51 percent as headland, 0.15 percent as lagoon, 0.07 percent as spit and 15 percent as mixed use. The results showed that about 59 percent of the study area is tidal mud flat. Little penetration of the substrate by oil occurs because the sediment is usually waterlogged but oil can persist on the surface over long periods. So that environmental sensitivity of coastal landforms put on this type of coast are increased.

We use ROPME sea area cruise data in summer 2001 and wind velocity and direction data on august 2001 in different stations in northern part of Persian Gulf for surveying and research. Sound velocity analysis and wind driven current vector plots are drawn by MATLAB version 7.1. Wind driven currents and underwater sound transmission interaction are surveyed with these graphs and Ekman theory. Results show that current intensity and sound speed decreases with increasing in mixed layer depth and a shallow channel engender between surface and bottom in northern part of Persian Gulf. If current and line which connects source and receiver are in a same direction then sound signal invigorates in other word sound intensity increases. If current direction be in opposite direction then sound signal attenuate and sound intensity decreases.

This paper proposes a high accuracy numerical method to model oil spill trajectories using a particle-tracking algorithm. The Euler method, used to calculate oil trajectories, can give adequate solutions in most open ocean applications. However, this method may not predict accurate particle trajectories in certain highly non-uniform velocity fields near coastal zones or in river problems. Simple numerical experiments show that the Euler method may also introduce artificial numerical dispersion that could lead to overestimation of spill areas. This article proposes a fourth-order Runge-Kutta method with fourth-order velocity interpolation to calculate oil trajectories that minimize these problems. The algorithem is implemented in the OilTrack model to predict oil trajectories following the "Nissos Amorgos" oil spill accident that occurred in the Gulf of Venezuela in 1997. Despite lack of adequate field information, model results compare well with observations in the impacted area.

The main objective of this paper is to assess the rate and trend of investment in middle-eastern container ports as well as the performance and growth of container shipping companies in the region. In addition, the paper evaluates the development of container related logistic activities in the region. Consequently, based on the result of the above assessment, a prediction of containerization development and growth in middle-east, as compared to global growth forecast, will be presented. In particular, the paper attempts to depict the contribution of Iranian seaports and shipping companies in promoting regional containerization in past and present, and future.

Potential flow around the marine structures based on Green's Theorem has been developed in ocean engineering problems. The main goal of surface wave parameters definition around body is calculation of wave making resistance and hydrodynamic coefficients. As body moves in deep water, fluid particles can move around hull freely but when it enters shallow water the particles movement is restricted and therefore wave pattern around body changes significantly. Changes mentioned can be considered as an interesting purpose in present study. Laplace equation in irrotational, inviscid, incompressible control volume of fluid is released as governing equation. The three-dimensional Boundary Element method is accomplished to calculate potential function at any point of computational field. To satisfy Neumann boundary conditions, the image method is employed. The Green function consists three parts. First part relates to the location of the singularity in the domain and its images with respect to the bottom. In The Second part, the free surface disturbance due to the singularity and its images is affected. Radiation condition is applied in third part. Numerical computations are applied to free surface waves generated by Wigley hull and moving pressure disturbance for the steady problem. The characteristic of wash wave such as the wave pattern on the free surface for different depth froude numbers and speed coefficients for pressure point in shallow water are reasonably predicted.

This paper discusses about some effects of the major parameters that contribute to the formation of residual stresses in the welding process and provides some methods to reduce this stresses. It should be mentioned that the proper understanding of these effects help in establishing better models or optimization of different proposed models. In general, one can optimize the residual stresses of welding process in two ways: first optimizing the temperature calculation methods and residual stresses to obtain more exact solutions; and second optimizing the welding methods to reduce the residual stresses. The first part considers the effect of some coefficients such as diffusion coefficient, thermal efficiency and conductivity, and the effects of cooling rate, temperature distribution, hardening and yield stress as well as two- or three- dimensional determination of the thermal model. However, the second part, discusses about the effects of preheating, heat treatment after welding or the effect of secondary heat resources moving around the welding heat resource on temperature distribution, residual stresses distribution, and distortions distribution.