HYDROPHYSICS
Year:2018 | Volume:4 | Issue:1 |Papers Count:10

A three dimensional numerical model namely ROMS (Regional Ocean Modeling System) and observational data are used to study the thermohaline front of Persian Gulf Outflow in the Oman Sea. The simulation results show the formation of a thermohaline front at 80m depth in the direction of the north-east-southwest at the mouth of the Oman Sea. The seasonal thermohaline front variability was also identified, during winter a heat and salty tongue stretches from the Strait of Hormuz to the continental shelf along the south Oman coast. During summer, it shows a current departing from the coast moving forward to the middle of the Oman Sea. Thermohaline front is observed throughout the year, in summer as unified and patchy in winter. Intrusion of warm and salty water of Persian Gulf into the Gulf of Oman displays a local increase in salinity in the middle layers in 150-450m and 100-400m depths in winter and summer respectively which expresses two boundaries in the upper and lower layers. Diffusive convection and salt fingering can be seen in both the upper and lower boundaries respectively. The complex ocean flow patterns are result of monsoons in the Oman sea area. During the winter monsoon, a single cyclonic gyre is often observed near 58◦ E and during the Southwest monsoon in summer, a dipolar eddy near Ras al Hamra and an anticyclone’ s gyre in 25° N are detected.

In the present study, the MITgcm model was used to simulate the surface front of the Oman Sea. The area under study is part of the Strait of Hormuz and the Oman Sea (22. 5-27. 3° N, 56. 2-61. 7° E). The initial data fed to the model are temperature, salinity, wind, net heat flux, evaporation and precipitation. The model was run for 15 years to reach a stability. Comparison of model outputs with measurement data (measurement data as well as satellite data) shows a good agreement. The results of the model indicate the presence of the Ras al Hadd front on the southern shores of the Oman Sea, the width and breadth of which changed spatially and temporally, being wider in winter due to northwest wind, and being less wider in summer and autumn. The existence of cyclones with more radius in winter and spring is observable on the Oman Sea surface. In summer and autumn, with increasing instability, anticyclones on the surface is seen which is in agreement with previous modeling and observation results. The density in the center of these cyclones reaches 1026 kg/m3. The maximum density difference between northern and southern Oman Sea in winter is calculated as (1-3 kg/m3) and the minimum density difference in autumn as (0. 55 kg/m3). Increasing the horizontal gradient along the front leads to an increase in vertical velocity and baroclinic instability. The depth of the front in winter was to the maximum of 80m, in spring to the minimum of 55m, and in summer and autumn was 60m. The buoyancy frequency was equal to 0. 007 s-1 in winter, 0. 023 s-1 in spring and, 0. 022 s-1 in summer and autumn. And the ratio of the wavelength that has the highest growth to Rossby radius deformation d in winter was equal to 1. 5, in spring 0. 65 and in summer and autumn 0. 61. The calculated value in winter is closer to experimental value.

Due to the forthcoming crisis for the extraction of energy as well as environmental pollution, floating offshore wind turbines (FOWT) can be the most practical and economic way to extract offshore wind energy resources in the deep waters of intermediate depth. FOWTs are a complex system that are under simultaneous effect of movements resulting from wind and sea waves. Coupled dynamic structures and motion response equations of these turbines show geometric non-linearities between relative forces and speeds. Floating wind turbine is a compound Aero-Hydro-Servo-Elastic system, for which coupled nonlinear motion equations must be designed taking into consideration movement forces and nonlinear damping involving all effects of wind and waves on time lapse. In the present study motion response for operation conditions in translational and rotational motions were analyzed to investigate functionality and structural stability of floating offshore wind turbine under buoyancy and Hydrodynamics forces. For this, a numerical model was developed in MATLAB software. Before dynamic simulation of the FOWT under study, present modules in the model were verified. Finally the obtained results were presented in time domain. The extracted results show that in translational motions, the maximum and minimum of buoyancy forces are in length and width directions respectively and maximum and minimum of Hydrodynamic forces values are in surge and sway directions respectively. Also, in rotational motions maximum and minimum of Buoyancy forces are in length and vertical directions respectively and maximum and minimum of the Hydrodynamic forces are in vertical and width directions respectively.

Rip currents are the most visible features of surf zone that extend from the shoreline to the sea and are classified based on the mechanism of the controlling forces governing the surf zone. In this research, at first a pattern is presented to show the quality of the Channel rips mobility using the Mike21/3 software. In the next step, the presented pattern is verified and confirmed using the CERC equation. The results of the model are then compared with field observations of other researchers by examining the mean rip mobility rate (V) and alongshore current velocity (vl), which shows a very good agreement. The main finding of this study indicates that the longshore mobility of Channel rips depends on the bed slope and depth of the channels. In addition, it was found that the intermediate beaches are conducive to the formation of this particular type of rip currents.

The present study aims to measure the offshore wind energy at different atmosphere levels, from the surface up to the level of 200 meters, examining the wind regime for the three northern, middle and southern basins of the Caspian Sea. In this regard, the data of wind speed components of ECMWF base at a height of 10m above the sea level with a spatial resolution of 0. 125 and time step of 6-hours, collected for the years 2005 to 2014, then, using Pyferret software, the monthly and yearly average of wind speed and energy for the three Caspian basins was investigated; Afterwards, the potential of this renewable resource was evaluated for some of the most important fields in each basin. The findings indicate that the middle and northern basins with an average annual energy of 1. 4 and 1. 6 MWh⁄ m^2, respectively, at an indicator height of 10m are suitable for providing part of the electrical energy of the offshore oil and gas platforms in terms of benefiting from the maximum wind energy so that this amount of energy increases as the sea level boosts. The results of the comparison of the Siemens SWT-4. 0-120 wind turbine output for four offshore oil and gas fields showed that the Kashgan field located in the Northern Basin has the highest output power with an average of 484. 88 MWh⁄ month while the Guneshli, Sardar-e-Jangal and Inky-e-mor fields with an output power of 336. 6. 155. 6 and 119. 4 are placed in the next ranks, respectively.

The aim of this research is studying the possibility of upwelling occurrence in the Iranian coastal area of Oman Sea. The occurrence of such a unique phenomenon near the coastal area of Jask made it a suitable subject to the study. To achieve this aim ArcGIS and MIKE3 softwares were employed. Year 2016 was considered for this research. Using ArcGIS techniques the patterns of prevailed wind, sea surface temperature, and concentrated chlorophyll-a using satellite remote measurement data for the area under investigation were taken into consideration. These plots confirm the probability of occurrence of upwelling in the area. For the simulation with MKE3, irregular mesh was designated as horizontal grids. In the vertical direction sigma layer stratification with 10 layers were chosen. After calibrating the model, results derived from the simulation were analyzed around Jask headland. The results indicate the existence of an upwelling during transition period of monsoon (October and November). This was simultaneous with the prevailed wind in the southwestern coast of Oman Sea.

One way of detecting ships or submarines is the observation of magnetic field signature around the object. Ships or submarines can be assumed as a collection of closed circuit of electrical currents. The electrical current of each close circuit must be properly regulated. The main purpose is production of a magnetic field equal to the magnetic field around the ship but with the opposite direction. By using this method, the magnetic field can be effectively reduced. This simulator is designed in C# language and it was named General Magnetic Compensation. The inputs of this software are geometry, location and magnetic field and the output is electrical currents of each closed loop, thus making the magnetic field reduced around the submarine. Accuracy and validity of the new software was investigated by analytical relation of magnetic field for proper geometry. Then a submarine was simulated in COMSOL and data of this simulation were used in General Magnetic Compensation software. The results were in great agreement with the results of the COMSOL software and could predict the magnetic field well.

This Paper Investigates and estimates the variations of sea surface salinity (SSS) in the Persian Gulf using moderate resolution imaging spectro-radiometer (MODIS) data on the Aqua satellite and the advanced microwave sounding Unit-B (AMSU-B) sensor on the NOAA-16 satellite in order to use remote sensing science for a more efficient and with more time distribution of salinity in the Persian Gulf. In this research a multiple-linear regression model in R software was developed using the data of MODIS and AMSU-B sensors. The data were obtained during a period of one year and fed to the R software. After processing the data in the R software, the correlation coefficient (R2) for salinity was calculated between field data and MODIS and AMSU-B sensors data. The correlation coefficients for MODIS and AMSU-B sensors were 0. 86 and 0. 85, respectively. Also, root mean square error (RMSE) between satellite data and in Situ data for salinity using MODIS and AMSU-B sensors were 0. 62 Psu and 0. 07 Psu respectively. The results show the accuracy of sensors for determining the sea surface salinity pattern in this study.

Water, as one of the most valuable natural heritage, requires constant monitoring, because the health of all living beings depends on the quality of water. Since the electromagnetic spectrum returned from the surface of the water indicates its nature, satellite imagery can be used to assess water quality and map the distribution of different parameters of water quality which are useful for decision makings by environmental and water resource managers. The general purpose of this study is to extract a practical algorithm for obtaining Golabar dam water quality parameters using Landsat 8 satellite data. The water quality parameters selected are electrical conductivity (EC) and pH, which are the main parameters for determination of water quality. Regression analysis was performed between the measured values of the parameters at the three sampling stations and the reflectance values of the water surface obtained from the OLI Landsat 8 spectral bands. Regression models were used to obtain the values of both parameters in the dam area. Finally, by applying a regression model on the satellite image of the area, the zonation map of the parameters in the Golabar Dam was obtained for 12 months. Also, using the time series, prediction of the quality parameters of the last two months of the year was performed based on the parameters of the past ten months and the results were compared to the previously produced maps, which were the results of the regression analysis. It was observed that similar results were achieved in most zones. The zonation maps of both parameters showed that the water in the middle section of the dam has better quality than the margin areas and the values of parameters in hot summer months in some parts are out of range.

The sound waves caused by the engine's operation and the rest of the floating interior equipment, if passed through a composite body, are detected by floating sea mines, especially acoustic mines. As a result, controlling and reducing the amount of sound transmitted from the floating body in operating parts is critical. In this study, due to the importance of passing the acoustic waves from the body of the particular vessels, the acoustic waves of different composite materials with layered and sandwich structures in water were evaluated and compared theoretically and experimentally. Five composite sheets were made to perform the tests. After placing them in water, the transmittance of acoustic waves per page was measured separately in two different frequency ranges. The first example is a sandwich panel with a plating foam core and glass and carbon fiber sheaths; the second specimen has a layered structure consisting of several layers of glass fiber, a third specimen like a second but with more layers, a fourth sample of sandwich panels with white wood core and shells. The fiberglass and final specimen are selected as a fourth sample but with a doped foam core. In the end, the results of the pages are presented in the form of a diagram and the necessary and applied comparisons between the experimental results and the theoretical calculations were made. The first and last samples are more absorbent than other specimens, even the first carbon-fiber sample is slightly better than the last one. It should be noted that the obtained results play an important role in the selection of composite materials and the design of a floating composite fuselage.