فصلنامه علوم و فناوری دریا
سال پانزدهم شماره 60 (زمستان 1390)

Nowadays, there is a great emphasis on utilizing technologies related to hiding in design of modern naval ships. These technology reduce energy reflectors from ship’s hulls so that the body radiations led to at least. Providing the appropriate solutions for reduction of the radiations, radar, infrared, audio visual and so on are basic tasks for designers of modern ships. The first step to achieve this goals is identifying the parameters affecting the body radiation and finding appropriate computational approaches for their calculations. In this paper, the emphasis is on the invisible infrared heat radiation from the body of a these ships. in addition to presenting and analyzing the infrared thermal parameters, a computational approach is presented for calculating and estimating the amount of radiation from a naval ship’s hull is presented.

In the present study to validate satellite data in the waters south of Iran, a comparison between the current level of wind from field data and satellite data from NOAA in the coastal area in 2008 is used. Tidal currents in the field data are filtered and the share of wind-induced surface currents is determined. Basis for the tidal harmonic analysis based on the tidal components. The Origin program and the method of Fourier transform (FFT) is used for filtering of tidal stream. The distribution of surface wind speed streams in the study area and also the correlation between measured data and satellite data has been determined.

Nowadays increase in earth population leads to the increase in energy consumption which is mainly has fossil resources. This in turn causes a reduction in oil and gas reservoirs, increase in their prices and creating greenhouse gases and air pollution. These problems draw the attention of scientists for use of clean energy resources. One of these resources is ocean wave energy. There are different plans for ocean wave energy absorption in the world. However most of them are in study stages and have not been approved for bulk production. In this paper the feasibility of absorbing sea wave energy by oscillating water column (OWC) system in the southern coast of Iran is studied. For this purpose wave interaction with this device is numerically modeled. Then four probable waves in Persian Gulf with different heights have been selected as input to the model. The results showed that if the input wave height to the system increases by 10%, the power of the device can be increased by 40%.

During the last decades, researchers took active interest in the dynamic behaviour of stiffened shells, because of their practical applications. In this investigation, conventional and super finite elements method are used for linear vibration analysis of these structures. Mindlin plate and Timoshenko beam theory are utilized to formulate plate and stiffeners, respectively. Stiffeners are not limited to be placed on nodal lines, and eccentricity of stiffeners is considered. The accuracy of the formulation is verified, by comparing some of the author's results of specific problems with those available in the literature. Effects of various parameters such as the boundary conditions of plate, along with orientation, type (eccentric, concentric), dimensions and number of stiffeners on free vibration characteristics are studied.

From historical point of view, equations that have the capability of modeling the dispersion and nonlinearity characteristics of waves were first used by Peregrine in 1967 to analyze the experimental results of solitary waves. In year 1972, Peregrine, based on the equations that he had developed in year 1967, derived a new system of equations for modeling the waves in shallow waters. These equations later became the foundations for derivation of shallow water system of equations like that of Madsen-Sorensen in 1992. In the present article, an effort has been made to offer a suitable finite element method for numerical solution of Peregrine system of equations (1972) which would have the capability of solving other shallow water system of equations that would be derived based on the Peregrine system of equations.

When the vessel moves in narrow channel it face with many challenges. as we know narrow channel lines have the large role in the country roads and have the special place in the economy, so safe passage of vessels and hydrodynamic parameters is very important. In this article it was attempted by using physical modeling and data analysis process of shipping channels design discussed and appropriate solution for safe passage of vessels be presented in narrow channels. suction and Cushion effect of Banks is very important so that if the vessel fails to maintain its channels on the central route consecutive, patients will be diverted and sometimes collide with the Banks will cause this deviation. Ships passing in the shipping channels and narrow navigable waterways, flow between the hull and the vessel Bank is created this makes the hydrodynamic interaction between the hull and the vessel Bank. this deviation is caused between the two floats that are moving. Accurate prediction of hydrodynamic parameters for operational ships in shallow water are essential to avoid accidents.

Reducing generated hydrodynamic noise by a submarine is very important in increasing its invisibility. In this paper, 2-dimensional shape of a submarine (vessel) is optimized to achieve least value of hydrodynamic noise. First, by defining velocity’s potential function and using Richardson’s separation method, velocity’s flow around vessel is computed. Then, standard deviation of velocity’s flow is considered as a cost function that will be minimized. Moreover, an iteration algorithm that is able to change shape’s boundaries is designed and vessel’s boundaries are determined in a way that cost function is minimized. So, vessel’s optimized shape with a minimized generated noise is achieved.