مهندسی دریا
Ali Asghar Moghaddas Ahangari; Seysd Mojtaba Alavijam
Abstract
One of the important goals of designing of planing boats is to achieve higher speeds, one of the major obstacles to this issue is longitudinal instability.In this research, a new method is proposed to solve the longitudinal instability of steped planing boats. In this method, using the transverse curvature ...
Read More
One of the important goals of designing of planing boats is to achieve higher speeds, one of the major obstacles to this issue is longitudinal instability.In this research, a new method is proposed to solve the longitudinal instability of steped planing boats. In this method, using the transverse curvature or variable deadrise angle of the body, the instability of boat has been corrected. Two bodies, called Nimala1 and Nimala2, were tested in National Iranian Marine Laboratory. The main difference between the two transverse curvature bodies is that Nimala1 has a constant deadrise angle and nimala2 has a variable deadrise angle in a section. To determine the effect of the variable deadrise angle on the longitudinal instability, each of the models has been tested up to longitudinal instability. Due to the equipment installed during the test of the model in the towing tank, it was not possible to measure the movement and therefore numerical analysis is used as a complement to the exprimental test. The results show that the variation in cross-curvature has a significant effect on longitudinal instability. By shifting the center of pressure to Aft, the delay of the porpoising was changed from 5.89 volumetric Fn in the fixed deadrise angle model, to 8.34 volumetric Fn in Variable deadrise angle model. Also, the resistance of this body is not significantly different from that of a body with constant transverse curvature, especially at high speeds.
مهندسی دریا
AliAsghar Moghaddas Ahangari; Hamid zeraatgar; seyed khalil shariati
Abstract
In designing of a marine vehicle, derivation of hydrodynamic coefficients of the equations of motion is very important. For derivation of these hydrodynamic coefficient's various methods such as analytical-experimental methods, Computational Fluid Dynamic (CFD) method and model test can be used. Among ...
Read More
In designing of a marine vehicle, derivation of hydrodynamic coefficients of the equations of motion is very important. For derivation of these hydrodynamic coefficient's various methods such as analytical-experimental methods, Computational Fluid Dynamic (CFD) method and model test can be used. Among These methods, due to the limitations of analytical-experimental methods and computational fluid dynamic method, the most accurate method is model testing.Empirically derived coefficients, which obtain in the marine laboratory, use to simulate the behavior of a marine vessel in the International Maritime Organization (IMO) maneuver test and determine the vessel's maneuverability.Due to differences in the marine laboratory equipment and test methods and to ensure the accuracy of results, standard models are tested and the results are compared against the results provided by the International Towing Tank Conference (ITTC).Accordingly, this article describes the process of model testing and derivation of the coefficients for the Esso Osaka benchmark vessel, using static and dynamic testing with Horizontal Planar Motion Mechanism (HPMM) in Shohada-e-Khalij-e-Fars national marine laboratory and compare the results with the results provided by the international towing tank conference.