جستجوی مقالات مرتبط با کلیدواژه « Shallow water » در نشریات گروه « مهندسی دریا »

In this paper, a two dimensional simulation of acoustic wave propagation was evaluated to assess the dispersion of sound wave fronts in shallow waters. This simulation was used to survey three dimensional sound propagation effects in shallow water in Hormoz Strait. Sound wave propagation simulation is appropriate for wide range of modeling methods with different accuracy degrees. One of these methods which is based on finite difference method, is useful for describing seismic wave propagation in shallow waters. This paper focused on assessing the use of finite difference method in time domain propagation modeling and imaging wave frontpropagation using Matlab and FORTRAN. The results of this simulation showed that due to the vertical velocity change of the sound velocity, the waves were divided into two branches and ultimately the vortex generated the sound waves and the regions with high noise could be highlighted.

For many years, surface wave high frequency radar is used for remote sensing of surface currents in deep water sea and also for measurement of wave velocity and height. The formula and methods are extracted for deep water and, therefore, may be inappropriate to use in shallow water. The Persian Gulf is the shallowest water region that has big area that is suitable for over the horizon radars. Theoretical and experimental analysis of surface waves in shallow water in the presence of the surface current has been done in the past, but in a few papers high frequency radar backscattering in shallow water was considered. In this paper, formulas for water wave velocity when the sea floor interacts with ocean waves were extracted. Also, formulas of Bragg frequency for surface wave high frequency radar when the water has a shear current in shallow water were evaluated. In some cases, the Bragg frequencies will be changed unequally for positive and negative frequencies. Spectrum of echo at surface wave high frequency radar has two resonated frequencies where one is negative and the other is positive according to sea waves travelling away from or toward the high frequency radar, respectively.

In this study, the default wave breaking term in the SWAN numerical model and the depth-induced breaking term presented by Thornton and Guza (1983) were investigated. It was shown that by modifying the coefficients in the Thornton and Guza pattern, the simulation of waves in shallow water can be improved. To evaluate the model performance, several waves were generated in 3 depths, periods and heights in the laboratory. The corresponding condition were simulated by the SWAN numerical model, and the wave heights generated in the laboratory were compared with the model results. Two main calibration parameters in the Thornton and Guza model were tuned in different scenarios, and the improvement of SWAN in simulating the waves was assessed in each scenario. Finally, some formula for calibration parameters were proposed to be implemented in the SWAN numerical model, which resulted in a significant improvement in the calculation of depth-induced breaking of random waves.

The most striking feature of underwater wireless sensor networks is energy constraints and the need to control energy consumption for each node and network.
limited energy of Nodes supplied by the batteries and almost recharge of them is impossible.
Given the importance of energy in these networks, study of parameters influencing the energy consumption of nodes and controling them is useful.
In this paper, the characteristics of acoustic in water is introduced, then by propagation modeling and using the obtained formulas, energy consumption in deep and shallow water in single and multi hopping transmission is compared.

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.