HYDROPHYSICS
Year:2016 | Volume:2 | Issue:1 |Papers Count:6

The main goal of this paper is to calculate the reflectivity index and scattering index of incident acoustic plate waves from a sound absorbent tile. The simulations are performed using Comsol software and obtained results are plotted as a function of the frequency of incident wave. It should be noted that the acoustic absorbent tile consists of an array of close-packed cones which are placed on a simple plate. Additionally, the acoustic absorbent tile is made of metal loaded butyl rubber. The butyl rubber is loaded with aluminum and lead. By comparing obtained results with analytical and experimental reported results one can deduce that performed simulations with Comsol software are as reliable as expected. Moreover, it is shown that the absolute values of the scattering index and reflectivity index of tile which is made of aluminum loaded butyl rubber are larger and hence this tile should be applied in experimental fabrication.

The goal of this study is a qualitative comparison of wind data in estimation of wave parameters from wind data at the mouth of Hormuz Strait, in Faror area. For this purpose, wind and wave data recorded over a period of one year were selected. Wave height and wave period were predicted separately using wind data through experimental methods SMB, SPM and CEM. The predicted wave height and wave period were compared with observational data. Also, a new wind data set from the ECMWF (European Center for Medium Range Weather Forecast) relating the same time period and the same area was obtained and analysis was also conducted again based on ECMWF wind data using experimental methods, SMB, SPM and CEM, and the new predicted wave height and wave period were compared with measured data. Results show that the quality of measured wind data in estimation of wave height through experimental method (SMB) and wave period through (SPM) method are higher than that of forced by the ECMWF data. So the predicted values are closer to the actual data. As a general conclusion measured data are more suitable in estimation of electrical energy from the waves. Maximum wave height before breaking point and breaking depth were obtained 0.71 m and 0.91m respectively.

In this study, the structure of thermocline layer in the Middle Caspian Sea (MCS) and Southern Caspian Sea (SCS) for 2004 was investigated using the three-dimensional ocean model COHERENS. The simulation results for three transects (along South-North, in Southern Caspian Sea "along 38.91N", in Middle Caspian Sea "along 42.45N" show that, in winter, season thermocline is almost eliminated and the temperature is uniform up to a depth of 100 m. After the erosion of surface thermocline in winter, this layer is recreated in spring. The results show the formation of a strong thermocline in summer and in the beginning of autumn, the thickness of the thermocline is reduced. In general, seasonal variability of water temperature is confined to the upper 120m layers. Also transects of Southern and Middle Caspian Sea show some special regions in which thermocline layer structure is stronger. Thus thermocline layer is created at a depth less than 25m from the sea surface water in eastern coast of SCS and at a depth less than 20m from the sea surface water in western coast of MCS during the summer.

The water crisis is one of the most important problems of the world, especially in Iran. Thus in this study, spectral behavioral features of Saltwater (The Oman sea) was compared with fresh water by using satellite images of Landsat. For evaluation, the optimum index factor (OIF) technique and statistical values such as correlation and standard deviation are used. Based on the results obtained from OIF, the highest value of OIF is 61.35906 with the first rank which is recorded in the band combination of 5-4-1 (correlation coefficient 2.280219and standard deviation 139.9121). Thus, this combination has the highest amount of information with least amount of duplication. Optimum index factor on qualitative technique scan is the best virtual color image to provide targeted area.

In the ocean, surface flow has an important role in heat transfer and climate change. The Sea flow prediction is of great importance in oceanography. In this study, neural network and wavelet techniques were used to predict the Strait of Hormuz surface flows. The data recorded in this area from November 1992 to December 2014 with time interval of 5 days prepared from NASA and Decomposed up to 10 sub-series using wavelet mother transform such as Rbio, Coif, Bior, dmey, Db, Sym, haar and then were used as input of neural network model. By applying wavelet and neural network weighting coefficients of each of the wavelet transformations were determined. Results showed that the wavelet generated by coif (5) has the most accurate prediction. In order to evaluate the effectiveness of favorable results in the training, validation and testing, multi-layer network with a number of different neurons in the hidden layer was used. The results show that the 6 subseries wavelet d1, d2, ..., d6 with R=0.891 and RMSE=0.025 in the test is the most appropriate number to predict the surface flow in the Strait of Hormuz.

In this research, the circulation of Gulf of Oman and the Persian Gulf dense water outflow front to the Gulf of Oman have been modeled using MITgcm which is a nonlinear 3D numerical model. The main domain is between and and was discretized by a non-uniform orthogonal grid of 480*342 points. Spatial resolution along the longitudinal axis ranges between 500m (near the sill region) to 1000 m and along the latitudinal axis is 1000m. The model has 32 z levels with the thickness of layers increasing from the surface to the bottom. In this investigation the Massachusetts Institute of Technology general circulation model (MITgcm) has been used. This model solves the fully nonlinear, non-hydrostatic Navier-Stokes equations under the Boussinesq approximation for an incompressible fluid with a spatial finite volume discretization on an orthogonal computational grid. The model formulation includes implicit free surface and partial step topography. The MITgcm formulation has been addressed in detail by Marshal et al. (1997a, 1997b) and its source code and documentation are available at the MITgcm group Website. The selected advection scheme for this study is a third-order direct space-time flux limited scheme (Hundsdorfer et al., 1995), which is unconditionally stable. Topographic data has been obtained from Iranian National Cartographic Center (NCC) with the high resolution bathymetry chart. No-slip conditions were imposed at the bottom and lateral solid boundaries. Initial conditions for temperature and salinity were obtained from the World Ocean Database (WOD) and World Ocean Atlas (WOA) Series [WOD group, 2013] for the month of June. The monthly averages of Sea Surface Temperature (SST) and Sea Surface Salinity (SSS) were derived from the WOA Database and the climatological data (wind and heat budget components) were derived from the NOAA Database [Noaa, 2013]. This data was prescribed in the model for all 12 months of the year. The model domain has two open boundaries at west and east sides. The west open boundary condition imposed by hourly observational data of salinity, temperature and current profiles from the surface to the bottom layer with 10 m interval and the east open boundary forced by hourly observational data of Sea Surface Height (SSH) predicted data of salinity, temperature and current profiles. This data was prescribed in the open boundary condition section of the model. To validate the MITgcm model, the monthly averages of temperature and salinity profiles for January obtained from WOA program are compared to MITgcm simulation results. Some of beneficial results of this modeling are achievement of the Persian Gulf outflow pattern and Gulf of Oman fronts. The modeling results show a clockwise circulation in the surface layer of Gulf of Oman. Also, two small counterclockwise gyres have been formed in the west of this clockwise gyre. One gyre, situated in the southwestern corner runs from surface to bottom. In depths of more than 500 meters the circulation is counterclockwise which is opposing of surface circulation. The results of this modeling also show the two layer exchange between the Persian Gulf and the Gulf of Oman.