sara allahyaribeik; madjid abbaspour; amir hossein javid
Volume 4, Issue 1 , February 2014, Pages 1-6
Abstract
The use of acoustic waves in researches related to sea water is of most importance among scientists recently. Since these waves are the only waves, transmitted in water with lowest attenuation and high speed, they can be used in many scientific fields. The main goal of this research is to better understand ...
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The use of acoustic waves in researches related to sea water is of most importance among scientists recently. Since these waves are the only waves, transmitted in water with lowest attenuation and high speed, they can be used in many scientific fields. The main goal of this research is to better understand the physics and mechanisms of sound-seabed interaction, including acoustic penetration, propagation, attenuation and scattering in marine sediments using a laboratory study approach. Sound backscattering from water sediments at central frequencies 1,2.25,5,10 and 15 MHz was studied in controlled laboratory conditions. Six kinds of sediments, from very coarse sands to fine sands, were degassed, and their surface was flattened. In these conditions, the sediment granular structure can be considered as the only controlling mechanism of backscattering. Comparison of frequency dependencies of backscatter for the six sediments with different mean grain sizes shows that in which frequencies we have the maximum backscattering sensitivity to the sediment mean grain diameter, and frequency-dependent attenuation will be shown.
vahid niksima; kamran lari; masoud torabiazad
Volume 4, Issue 1 , February 2014, Pages 7-14
Abstract
Nowadays, in consideration of environmental issues and limitation of fossil fuels, there is a particular consideration of renewable energy including Ocean Energy, that can extracted going through various methods such as Wave Energy, Tidal Energy, Salinity Gradient, OTEC: Ocean Thermal Energy Conversion.Herein ...
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Nowadays, in consideration of environmental issues and limitation of fossil fuels, there is a particular consideration of renewable energy including Ocean Energy, that can extracted going through various methods such as Wave Energy, Tidal Energy, Salinity Gradient, OTEC: Ocean Thermal Energy Conversion.Herein this research, operation of OTEC Method in Southern Caspian Sea has been discussed. For this purpose Sea Surface Temperature (SST) Data and Thermocline diagram with respect to 25 stations from east to west coastal area, measured in 1995 in various seasons, have been used. Considering the researches conducted, in order to use OTEC, there must be a difference in temperature between the surface and depth for at least 20 Degrees Centigrade. If such difference in temperature occurs in less depth, closer to the coast, such energy extraction will be more cost-effective.According to investigations conducted, there is a difference in temperature for about 20 Degrees Centigrade in the depth of about 200 m in the Caspian Sea during hot seasons of the year. In summer and early autumn when Thermocline achieves its complete growth, energy extraction from OTEC has a desirable yield. During winter and spring when there is decay in Thermocline, the yield is so low that using this method is not justifiable. Thus, this method can only be used in hot seasons of the year. Finally, hydrographic and temperature investigations have revealed that southeastern coasts especially those of Bandar Neka and Babolsar achieve the desirable difference in temperature, closer to the coast due to high SST and coastal slope, compared to other areas and eventually, using OTECT is cost-effective.
mohammad javad ketabdari; m. BarzegarPaiinlamouki
Volume 4, Issue 1 , February 2014, Pages 15-24
Abstract
Submerged breakwaters are one of the shore protective structures. Any discontinuity in these breakwaters causes changes on current parameters including speed and water surface profile. In this paper, discontinuous submerged breakwaters were modelled to investigate the changes in the wave and flow pattern.To ...
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Submerged breakwaters are one of the shore protective structures. Any discontinuity in these breakwaters causes changes on current parameters including speed and water surface profile. In this paper, discontinuous submerged breakwaters were modelled to investigate the changes in the wave and flow pattern.To investigate the phenomenon, three models including a shore with constant slope, a shore with continuous submerged breakwater and a shore with discontinuous breakwater were used. Extended Boussinesq Equations were used for wave generation. The results of the models showed that in the shore without breakwaters transient rip currents are produced across the shore. By addition of the breakwater, the wave breaking happens on the crest of breakwater which leads to dissipation of their energy. This in turn creates calm shore currents. However, constructing a gap in the center of breakwater causes some changes in the system of shore currents. This phenomenon generates a pair of flow vortices and a powerful return current called rip current. Rip currents not only threaten the life of swimmers, but also play an important role on the sediment transportation and erosion of the sea bed around the breakwater gap and may lead to destruction of the whole breakwater.
m. a. Nezammahalleh; m. yamani; sh soltani; a. maldar badeli; a. rastegar
Volume 4, Issue 1 , February 2014, Pages 25-36
Abstract
In coastal areas, hydrodynamic factors make changes in shorelines geomorphology. This can affect coastal facilities and cause hazards to human societies in the areas. This study has investigated the influence of wave and tide properties on Khamir Port, Hormoz Strait in coast of Persian Gulf. The purpose ...
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In coastal areas, hydrodynamic factors make changes in shorelines geomorphology. This can affect coastal facilities and cause hazards to human societies in the areas. This study has investigated the influence of wave and tide properties on Khamir Port, Hormoz Strait in coast of Persian Gulf. The purpose of the study is to make a mathematical regional and local modeling of water level fluctuations and flow velocity by MIKE21 application. These models provide some maps to show tide and wave effects on shoreline changes. The maps have been created as the results to reveal the maximum advance of water onto the coast in high tide and low tide patterns. Time series of water level variations in two months and the flow velocity have been examined in some randomly selected points in the study area. This can be argued that these water level fluctuations may undermine coastal structures and alter shoreline geomorphology. These maps resulted from the modeling can be used for safety planning in constructional projects, tourism, and insurance management.
madjid ghodsi hassanabad; ajang fardad
Volume 4, Issue 1 , February 2014, Pages 37-46
Abstract
The complete 3D nonlinear dynamic problem of extensible, flexible risers conveying fluid is considered. For describing the dynamics of the system, the Newtonian derivation procedure is followed. The velocity field inside the pipe formulated using hydrostatic and Bernoulli equations. The hydrodynamic ...
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The complete 3D nonlinear dynamic problem of extensible, flexible risers conveying fluid is considered. For describing the dynamics of the system, the Newtonian derivation procedure is followed. The velocity field inside the pipe formulated using hydrostatic and Bernoulli equations. The hydrodynamic effects of external fluids are taken into consideration through the nonlinear drag forces in various time steps and the added inertia due to the hydrodynamic mass. Following the Newtonian derivation, the dynamics of the pipes element with effects of internal fluid are considered separately and the final governing set is derived by combining the equations of inertia equilibrium. The study focuses specifically on the effect of the inner flow to the global dynamics of the riser. This task is accomplished using time domain teachings and the Finite Element method is used as a powerful numerical method. Moreover the Euler-Bernoulli beam theory is used response to model the dynamic behavior of the flexible risers.
a bazzi
Volume 4, Issue 1 , February 2014, Pages 47-56
Abstract
Levels of the heavy metals Copper (Cu), Zinc (Zn), Lead (Pb), Cadmium (Cd), Chromium (Cr), Nickel (Ni), Iron (Fe) and Manganese (Mn) were determined by graphite furnace atomic absorption spectrophotometer (Model 67OG) in coastal water, sediments and soft tissues of the Saccostrea cucullata, from the ...
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Levels of the heavy metals Copper (Cu), Zinc (Zn), Lead (Pb), Cadmium (Cd), Chromium (Cr), Nickel (Ni), Iron (Fe) and Manganese (Mn) were determined by graphite furnace atomic absorption spectrophotometer (Model 67OG) in coastal water, sediments and soft tissues of the Saccostrea cucullata, from the intertidal zone at five stations in the Gulf of Chabahar on the Iranian coasts along the Oman Sea.The concentrations of heavy metals in water ranged between 3.37–5.74, 18.01–22.62, 4.24–4.52, 0.15–0.19, 20.16–21.46, 16.42–17.14, 15.43–24.76 μg L-1and 7.06–8.67 μg L-1 for Cu, Zn, Pb, Cd, Cr, Ni, Mn and Fe, respectively. The corresponding concentration values in the sediments were 46.79–54.76, 40.14–43.12, 25.63–28.23, 0.53–0.63, 47.16–51.43, 26.45–28.68, 52.13–53.46 and 84.42–89.14 μg g-1for Cu, Zn, Pb, Cd, Cr, Ni, Fe and Mn, respectively. The highest accumulated metals were Zn, Cu and Mn in S. cucullata while the lowest one was Cd. The highest concentrations of all metals in water, sediments and Oyster were recorded at Tiss harbour eastern parts of the Gulf, while the lowest concentrations were recorded at Damagheh. Based on this research, land based activities; shipping activity and the sewage disposal from vesseles and residential area close to these harbors are the main source of metal pollution in the Gulf of Chabahar.