فصلنامه علوم و فناوری دریا
سال سیزدهم شماره 50 (تابستان 1388)

Details of a numerical model for predicting free water surface in severe gradient, presents in this paper.In this model, concerning to use non-hydrostatic pressure in seas and rivers for two-dimensional modeling, a new method named step method has been used. In fact this model is conflated of step method and sigma coordinate system.Finally, the results of this model are compared with results of a model with sigma coordinate regarding hydrostatic pressure and water surface profiles and pressures analyze and compare in different times.

The application and design of concrete block mattresses for stabilization and protection of onshore pipelines utilized for seawater intake structures has been studied in this paper. The Geosynthetic products have been exploited in wide variety of applications in civil engineering such as bed erosion and pipeline stability. Mostly the combination of Geosynthetics with other materials such as concrete blocks results in better performance in adverse environmental conditions. The combination of Geosynthetic and concrete blocks which is known as concrete block mattress has received a great attention in marine purposes in the recent years due to their resistance against wave and current forces. In this study is using semi empirical relations the proper thickness of concrete blocks such that it can withstand the wave and current attacks is determine. The study revealed that the thickness should be determined based on the critical condition which is the wave breaking point.

Nowadays naval architects, marine environment experts and officials Ports and Shipping Organization focused in problems associated with surface waves caused by movement of various vessels in coastal waters. The surface waves can affect safety of service operations of other vessels those are navigating in coastal waters and have destructive effects on coastal and offshore structures. Recently, extensive researches have been made to understand the nature of these waves and reduce their destructive effects on the environment and to find appropriate and practical solutions to reduce the intensity of vessels induced surface waves and developing appropriate criteria, in terms of vessel speed and distance from the coastal regions, to provide safe navigation in coastal waters. In this study, a surface wave caused by movement of a submerged source in deep, shallow and enclosed waters has been considered. On this basis, to analyze the wave pattern in order to achieve the desired field potential for calculation of wave elevation, a program prepared and the distribution of these disturbances has been calculated and analyzed. It is worth to mention that wave reflection from channel walls is considered to check the accuracy of results, and it can be investigated in far field. The effect of channel width and depth on wave pattern and height are thoroughly discussed. Ship speed and shallow water depth are also considered as main parameters affecting generated wave qualities.

Study of the hydrodynamic characteristics of an underwater body requires a good knowledge about hydrodynamic coefficients of the body. The fluid forces acting on an underwater body and their effects on the flow field are depended to the body geometry, motion speed, body maneuvering, the fluid properties and the flow regimes on body surfaces. Thereafter knowing the hydrodynamic coefficients, one can predicts the body motions in Six degree of freedoms (6 DOF) by considering the vehicle as a rigid body and using of the second Newton’s law. At this paper, in order to determine more important coefficients affecting the vehicle motion and its stability, all of the hydrodynamic coefficients for conventional torpedo bodies are analyzed. Then the corresponding experimental scenarios for measuring the important coefficients are discussed in details. These analyses show that only twelve coefficients are more important and necessary for hydrodynamic studies of these bodies. It must be noted that the emphasis of this paper is not on the numerical solution of these hydrodynamic equations.

With the advent of high speed computers, significant progress has been made in predicting flow characteristics around any given hull form(such as underwater vehicles). This paper presents finite volume method based on Reynolds-averaged Navier-Stokes (RANS) equations for computation of submarine drags with free surface effect. Computations are performed with CFX software, on bare submarine hull DREA and with free surface effect and also in different deep. k-ε model has been used to simulate turbulent flow past bodies. Finally, computed results are compared measurements and found satisfactory.

Physical parameters such as “Temperature, Salinity, Density” and dynamic of water are researched in the Strait of Hormuz in this investigation. Physical parameters once in 29. Nov. 2006 by CTD at 6 stations (2 transect) from Bandar-Abbas to Qeshm-Island & Larak Island measured. In this region picnocline and thermocline werent seen and physical parameters showed minimal changes to the depth, that entire mix was observable up to 5-meter depth. Also correlation coefficiency between density and salinity in the range of 0.967 to 0.999 attained with shows the direct dependency of density to salinity, and also correlation coefficiency between temperature and density in the range of -0.987 to -0.900 attained, which indicate reverse dependency of density to temperature. It could be noted that sketching regression between density-salinity confirms the direct dependency of density to salinity.Also measuring correlation coefficient in all station varied between 0.967 and 0.999 as well as sketching regression support the direct functionality of density to salinity.

Human irregular interferences with the purpose of exploitation from natural resources continue to increases which have detrimental effects on environment, particularly, on aquatic ecosystems. Some pollutants like Nickel, Vanadium, and Cobalt, namely three important indicators of oil pollution, have negative impacts on aquatic organisms` metabolism through marine exploitation, oil products transportation or industrial/power plants-related waste waters. These impacts generate in the manner of bioaccumulation. For example, Vanadium affects on genetic and evolutionary level of aquatic organisms. Nickel develops in aquatic organisms especially in gonads and Cobalt influences on enzyme-related activities, negatively.This paper tries to investigate entry ways of these elements into aquatic environments and study their mechanisms and effects on aquatic organisms. Results show that factors like pH, temperature, and amount of Oxygen are effective on heavy metals (like Ni, V, and Co) entry and accumulation in aquatic organisms as they cause tension and disturbance in enzyme system as well as DNA of these creatures.