مهندسی دریا
Saeid Khaksari Nezhad; Nima Shahni Karam Zadeh; Nassim Ale Ali
Abstract
The power absorption capability of a floating oscillating body depends on the proper wave-structure interaction. A wave energy converter (WEC) device would capture the wave power as the system radiates waves in the opposite direction (phase) to the incoming waves. Hence, in order to evaluate the initial ...
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The power absorption capability of a floating oscillating body depends on the proper wave-structure interaction. A wave energy converter (WEC) device would capture the wave power as the system radiates waves in the opposite direction (phase) to the incoming waves. Hence, in order to evaluate the initial performance of a point absorber wave energy converter, determination of radiation force is crucial to design and optimal control of wave energy absorption. In this paper, once the hydrodynamic parameters are obtained for a heaving vertical-cylinder buoy, the equation of motion for the system has been considered upon the Cummins integro-differential equation. Numerical analysis of this type of equation could be computationally demanding due to the presence of a convolution term. Therefore, a program was written using the high-level language in MATLAB and the expression for the radiation force in the equation of motion has been substituted with a linear state-space model. The results of the frequency domain analysis in the range of 1-2 radians per second are implemented into the model which corresponds to the predominant wave conditions of the offshore region in Persian Gulf. The proposed open source model compared to direct calculation of the convolution integral in the equation of the motion provides highly accurate prediction and maintains system stability. The model would also be computationally cost effective for higher degrees of freedom since other codes are practically not available.
مهندسی دریا
Leila Jozaee; Sahar Damiri; Nassim Ale Ali; Etemadeddin Rabei
Abstract
In this paper, free vibration of the ship with Timoshenko beam model is investigated and natural frequencies and mode shapes are obtained. Since the frequency equations of Timoshenko beam are nonlinear, for obtaining the frequencies and mode shapes, numerical method, differential quadrature method with ...
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In this paper, free vibration of the ship with Timoshenko beam model is investigated and natural frequencies and mode shapes are obtained. Since the frequency equations of Timoshenko beam are nonlinear, for obtaining the frequencies and mode shapes, numerical method, differential quadrature method with discretization is used. Frequencies of some vessels with different geometers such as length, height and width are obtained and versus length, height and width are compared and effect of these parameters on the frequencies are investigated. These investigations show that by increasing these parameters the frequencies are decreased and for the vessels that have a large ratio of height to length, the Timoshenko beam model should be used for vibration investigation that the shear effect is considered.
مهندسی دریا
m b; m b; Nassim Ale Ali; m s
Abstract
Nowadays demand for renewable and reliable energy sources due to the global warming, environment pollution and global energy crisis is of utmost importance in offshore engineering. As a result of recent developments in wind industries extracting energy from offshore wind resources has a growth. A number ...
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Nowadays demand for renewable and reliable energy sources due to the global warming, environment pollution and global energy crisis is of utmost importance in offshore engineering. As a result of recent developments in wind industries extracting energy from offshore wind resources has a growth. A number of researches are carried out in the field of land based wind turbines but investigations about floating wind turbines as a consequent of their dynamic behavior complexity are still limited and further more detailed surveys are required. This paper presents an open source and public simulation code for the analysis and design of floating offshore wind turbines. The dynamic behavior due to environmental and inertial loads is obtained using a fully coupled comprehensive numerical tool implemented in MATLAB. blade element momentum theory used to determination of aerodynamic loads on wind turbine as well as Panel method and Morison's equation to calculate the hydrodynamic loads considering the instantaneous position of wind turbine system. The results show the domination of aerodynamic loads on wind turbine dynamic behavior as well as stability of structure due to the great difference between values of dominate aerodynamic excitation frequency and system natural frequencies.