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
Mohsen Shojaie; Mostafa Jafarzadeh Khatibani; Etemad ODin Rabei Gholami
Abstract
Estimating the required propulsive power of a vessel at early stage of design is important from two aspects, which are estimating the weight of the machinery as a function of required power and estimating the amount of fuel needed to determine the initial capacity of the vessel. This approximation can ...
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Estimating the required propulsive power of a vessel at early stage of design is important from two aspects, which are estimating the weight of the machinery as a function of required power and estimating the amount of fuel needed to determine the initial capacity of the vessel. This approximation can be based on empirical formulas, data of similar ships or diagrams deduced from statistical data for various types and sizes of ships. Current empirical formulas for estimating ship power are only limited to very few general equations and are inaccurate for specific type of vessels. In this study, by using 90 container ship data and multiple linear regression method, several statistical models were prepared and statistically analyzed considering the influence of the main parameters of the vessels on the required amount of power, and finally a suitable formula extracted. Evaluation of the extracted formula indicates acceptable accuracy for the container ships which can be used to estimate the required power of container ships within the range of this formula.
مهندسی دریا
Mahboobeh Golaghapoor Kami; Mostafa Jafarzadeh Khatibani; Etemadaldin Rabei Gholami
Abstract
For all new ships sea trials should be carried out as a part of the delivery from the yard to the ship owner. An important part of the delivery sea trial is to determine the speed capability of the ship in the contractual condition, which is traditionally deep, calm water and no wind, at some specified ...
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For all new ships sea trials should be carried out as a part of the delivery from the yard to the ship owner. An important part of the delivery sea trial is to determine the speed capability of the ship in the contractual condition, which is traditionally deep, calm water and no wind, at some specified loading condition. However, it is seldom possible to perform this particular test under such conditions, and when the test is done in other conditions, the result is corrected back to the contractual condition. The correction can be of a significant magnitude. The correction procedure can be influenced by different parameters such as wind resistance, shallow water effect, sea currents and added resistance due to diffraction. There are different experimental methods for correction of measured speed. Since the latter parameter is the most important between others, In this article added resistance due to diffraction has been calculated for three ships using existing methods and comparisoned with the speed correction result of shipbuilder company (Hyundai Heavy Industries). The results show considerable deviation between HHI sea trial speed correction method and other methods. So HHI added resistance calculation method needs to be revised.