S.A. Amid; S. Allahyaribeik
Volume 5, Issue 2 , June 2015, Pages 55-64
Abstract
Steel-structured jacket or template platforms have been extensively installed in Persian Gulf offshore oil & gas fields. For the jackets in the water depth range of 40 meters in this region, utilizing the self-upending concept has been investigated. It has been concluded that designing the light ...
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Steel-structured jacket or template platforms have been extensively installed in Persian Gulf offshore oil & gas fields. For the jackets in the water depth range of 40 meters in this region, utilizing the self-upending concept has been investigated. It has been concluded that designing the light weight jackets, implementing the self-upending process for their installation operations, are economically and practically more convenient than the usual crane-assisted up-ending methods. Two methods of self-upending for light weight jackets have been presented in this paper .in first method self-upending is implemented without using ballast systems and in second model self-upending is implemented with ballast systems .Considering the required number of new installations for the “new” as well as “brown-bag” projects, and considering the existing problems and difficulties for the available marine spread, especially ready-to-work heavy floating cranes, utilizing this concept in the offshore industry for light weight jackets seems to be a considerable break-through
M. Soltaninejad; F. Azarsina; A.H. Javid
Volume 5, Issue 2 , June 2015, Pages 65-75
Abstract
Many existing phenomena in nature are considered new design ideas in various fields of industry. Bionics is the application of biological methods and systems found in nature to the study and design of engineering systems and modern technology. By performing bionic review, the researchers found the penguins ...
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Many existing phenomena in nature are considered new design ideas in various fields of industry. Bionics is the application of biological methods and systems found in nature to the study and design of engineering systems and modern technology. By performing bionic review, the researchers found the penguins by delivering air locked under their wings and creating air bubbles, the drag significantly reduces. This motivates to study this factor in the marine industry by researchers and scientists. The overall drag of a marine vessel is directly proportional to the frictional drag. The reduction of frictional drag can be achieved by creating an air layer between vessel`s hull and flow around it. Creation of a cavity and cross channel of air can be easily just in order to reduce hull drag, while the air from a hole is injecting, the drag reduction up to 20 percent might be achieved. Experiments indicate that the pattern of wave drag reduces due to the air using and changes in pressure fields. In this research, by the use of theoretical relationships and the results of experiments, frictional drag reduction with different methods of air injection was investigated and then by the use of numerical software simulation (ANSYS-fluid flow), air injection on the floating model. The achieved results for drag reduction with decrease of wetted surface area at speeds of 4, 6 and 8 m/s are presented. By comparing the results of experiments(Harley high speed craft model) with software analysis and software simulation was validated. Due to high cost of manufacturing a model with air injection accessories and towing tank tests, with the acceptable precision results of this research, numerical software simulation (ANSYS-Fluid Flow) is more quick and efficient.
SH. Entezam; S. Kazemi
Volume 5, Issue 2 , June 2015, Pages 77-86
Abstract
Wave run-up is one of the most important and effective parameters in designing semi-submersible platforms. Besides unforeseen effects on the movements and response of the platform, wave run up can also cause slamming forces to be exerted on the lower deck of the platform. Therefore, at the first stages ...
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Wave run-up is one of the most important and effective parameters in designing semi-submersible platforms. Besides unforeseen effects on the movements and response of the platform, wave run up can also cause slamming forces to be exerted on the lower deck of the platform. Therefore, at the first stages of this plan, before running tests on the model of the platform, numerical methods are usually utilized for estimating the appropriate height of semi-submersible platforms’ deck in order to prevent any damage on it In this paper, in order to verify the validity of simulation and also the efficiency of "Flow3D" on predicting the wave run-up and also the effect of wave impact under various steepness on a semi-submersible platform, results derived from the simulation by "Flow3D" compared to the results of both WAMIT tool and the experimental model. The results show that "Flow3D" has great capability to estimate the amount of wave run-up when investigating the waves with the steepness of up to about 4 percent. But, by increasing the steepness of striking wave in front of the aft columns, the results obtained from the software are not in good agreement with the experimental and WAMIT results.
A. Ebrahimi
Volume 5, Issue 2 , June 2015, Pages 87-92
Abstract
The advantage of additive manufacturing (AM) (e.g. reasonable time and expense in prototyping, and reliable product) has triggered the idea of using this method in manufacturing of marine vessels components. The current article tries to introduce basic concepts of AM method and its application in marine ...
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The advantage of additive manufacturing (AM) (e.g. reasonable time and expense in prototyping, and reliable product) has triggered the idea of using this method in manufacturing of marine vessels components. The current article tries to introduce basic concepts of AM method and its application in marine industry; have a glance at additive-manufactured parts microstructure; elaborate the challenges in investigation of mechanical properties of AM products; in order to makes this technology more known to domestic industry.
M. Heydari; S. Allahyaribeik
Volume 5, Issue 2 , June 2015, Pages 93-98
Abstract
The process of erosion and desertification affects social communities, agricultural lands and natural resources in coastal areas. The rapid coastline changes would cause social and economic issues in the coastal areas. In this study, Miankaleh coasts and the eastern coastlines of Amirabad port have been ...
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The process of erosion and desertification affects social communities, agricultural lands and natural resources in coastal areas. The rapid coastline changes would cause social and economic issues in the coastal areas. In this study, Miankaleh coasts and the eastern coastlines of Amirabad port have been surveyed due to existing benchmarks since June 2013 until December 2015 in order to analyze the coastline changes in Amirabad port. Then the surveyed lines were compared with sea levels at the time of surveying. The sea level data has been used (to calculate the beach slope) in order to monitor the sedimentation and erosion processes in the coastlines movements. The results of this comparison show that coastline changes are irregular and they may not follow the seal level changes. Therefore the coastline changes in these areas are influenced by erosion and sedimentation units.
S.M. Sajadi; F. Azarsina
Volume 5, Issue 2 , June 2015, Pages 99-113
Abstract
Given the worldwide industry progress in the construction of massive concrete structures, it would be a good idea to use concrete gravity base structures (GBS).In this regard, better understanding of thesestructuresregardingtheiradvantages and disadvantages in offshore areas seems necessary.The present ...
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Given the worldwide industry progress in the construction of massive concrete structures, it would be a good idea to use concrete gravity base structures (GBS).In this regard, better understanding of thesestructuresregardingtheiradvantages and disadvantages in offshore areas seems necessary.The present study employed MacCammy-Fuchs method, which is based on the size of the structure to the wavelength and the range of Keulegan-Carpenter number; in this method, diffraction theory and Bessel functions are used to compute the velocity potential function and consequently compute the hydrodynamic pressure on the components of the structure.The results of this study with regard to the harmonic dynamic response of the rocking motion of the platform under wave loads revealed that (i) the computed torque value converges to a definite value by decreasing the size of elements,and (ii) Bessel functions can be represented by amplitude and phase functions which have identical performance.The time-history response of the gravitybase structure, and the amplitudechanges of rocking motion relative to frequency and the height of the waves are other results obtained in this study. Finally, the stability index of the GBS shows that the platform is within safe limits.