مهندسی دریا
Hamid reza Karimi; Etemad odin Rabei Gholami; Nima Shahni Karam Zadeh
Abstract
Development of industrial activities in the offshore areas has led to the importance of safety of helicopters. Understanding the behavior of the wind around Helideck, especially on take-off, approach and landing are essential to enhance the safe operation of helicopters. In this regard, legislators have ...
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Development of industrial activities in the offshore areas has led to the importance of safety of helicopters. Understanding the behavior of the wind around Helideck, especially on take-off, approach and landing are essential to enhance the safe operation of helicopters. In this regard, legislators have imposed restrictions on the operation of helicopters under varying conditions of disturbance through the standards and rules. In this paper based on the Reynolds-averaged Naviere-Stokes theory, the wind current on the SPD19-A offshore platform from the 19th phase of south pars gas field complex in the CFD environment is modeled, taking into account all the effective equipment. Considering variables such as wind direction, the horizontal and vertical direction of the crane boom, 42 scenarios considered to an appropriate insight of turbulence conditions been provided. The Norsok standard has been used to select the assessment criteria and the two criteria "Horizontal velocity deviation" and "Turbulence energy" has been evaluated, also the stream lines from numerical and experimental modeling have been compared. The results indicate that in the East-West wind direction, the increase in the vertical angle of the boom improves the turbulence conditions in the center of the Helideck. In the direction of the northeast-southwest, the increase in the vertical angle of the boom causes the turbulence conditions in the helideck center to become more complicated. Also, based on the turbulence kinetic energy index, the increase of the vertical angle of the boom for both wind directions makes turbulence conditions more complicated.
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.
niam shehni karamzadeh; seied habib mosavi jahromi; mohammad mahmodian shoshtari; mahmod shafaie bajestan
Abstract
One of the most important topics in river engineering is protection of banks. Because of change in flow characeristics the banks of rivers will be remove that it is very sever. Use of spur dikes is one of the common methods for protection of banks but there is a problem in this field that is protection ...
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One of the most important topics in river engineering is protection of banks. Because of change in flow characeristics the banks of rivers will be remove that it is very sever. Use of spur dikes is one of the common methods for protection of banks but there is a problem in this field that is protection of spur dikes which there isnt many reserch about its. Because the spur dikes are very useful in the bends therefore this research carried out in the 90 degree bends. In this resech the goal is investigation of the of spurdikes angel on stability if riprap. For achievement of this goal use three length of nose of spur dike ( 50%,75% and 100% of body length of spur dike) and three diameter of rip rap(1.51cm,1.12cm,0.72cm). the results showed that in all of the experiments increase in angel of nose cause decrese in froude number of flow, densimetric froud number of sediment in failure of riprap and then decrese of riprap stability.