مهندسی دریا
Abdolhossein Mohammadrahimi; Mohammadreza Negahdari; Seyed Amin Hosseini; Ehsan Parsaei
Abstract
Extensive studies on cavitation have been conducted for years as an undesirable phenomenon in marine engineering. The cavitation phenomenon causes severe damage to the body of torpedoes, ship's propellers, pump impellers and turbines. It also increases the frictional drag of submarine vessels and ...
Read More
Extensive studies on cavitation have been conducted for years as an undesirable phenomenon in marine engineering. The cavitation phenomenon causes severe damage to the body of torpedoes, ship's propellers, pump impellers and turbines. It also increases the frictional drag of submarine vessels and imposes many limitations on their design and construction. With increasing speed in submarines and increasing of the cavitation, supercavitation occurs which can be used to create a large bubble around the vessel. Because of drag in the water is mostly due to the friction of the body, by the supercavitation, the contact of water with the torpedo is reduced and as a result the friction drag is greatly reduced and the torpedo speed will increase significantly. In this regard, by artificially injecting air into the body in the state of cavitation, the process of creating supercavitation and reaching this stage can be accelerated.In this study, in order to investigate the effect of torpedo nose shape on supercavitation, different types of torpedo bodies have been modeled and studied different nose shapes. After modeling, meshing is performed with ANSYS Fluent software and the analysis of the model in cavitation numbers (0.2, 0.3 and 0.4) will be examined. Finally, the model will be analyzed in air injection mode (artificial supercavitation) with ANSYS CFX software and the results will be presented.
مهندسی دریا
A. Mohammad Rahimi; Mohammad Khedmati
Abstract
Grillages consisting of intersecting beams are supporting shell structures of the ships in different places such as bottom, deck and sides. Different methods available for strength analysis of plated grillages are studied from the viewpoints of characteristics and limitations. Finally, the way to assess ...
Read More
Grillages consisting of intersecting beams are supporting shell structures of the ships in different places such as bottom, deck and sides. Different methods available for strength analysis of plated grillages are studied from the viewpoints of characteristics and limitations. Finally, the way to assess the strength of such structural elements is investigated. This study is based on preparation of a soft-ware for analysing the grillages. Using the software, it is possible to analyse grillages used in the ships’ structures for any type of boundary and loading conditions that are simply selectable by users. Getting the required input data from the user, elastic deflections and stresses induced as a result of applying concentrated or distributed loads are calculated at the intersections of the longitudinal and transverse members, relieving the need to complicated numerical calculations.