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
Mohammadreza Negahdari; Ruhollah Karimpuor; Iman Khatami; Babak Ahmadpoor
Abstract
Motion control may be effective by reducing the heave and pitch of a high speed vessel especially in planing hull. In order to decrease these motions, the foil was effective technique rather than other methods. High speed crafts are known to have rough water problem is essentially one of compromise between ...
Read More
Motion control may be effective by reducing the heave and pitch of a high speed vessel especially in planing hull. In order to decrease these motions, the foil was effective technique rather than other methods. High speed crafts are known to have rough water problem is essentially one of compromise between speed and seakeeping performance. The objective of this research is to predict the performance of the planing craft M Hull in term of seakeeping before and after incorporating with stern foil. Prototypes of the hull have been modeled in 3D using Rhino and is running at the head sea of the regular wave and its responses are obtained by unsteady RANS simulations using StarCCM+ software. The obtained results of RAO heave and pitch motions are presented at various Speed Cofficient. Basically, there are advantages by incorporating the stern foil at aft of the vessel to achieve the planing mode which it gives significant effect to motion reduction by increase of speed in special region. For example, at speed 40 knots by adapting with Stern foil the heave & pitch RAO trim down by 19.31% and 26.44% respectively.