نشریه مهندسی شناورهای تندرو
پیاپی 59 (پاییز و زمستان 1400)

One of the main problems in SWATH ship is the excessive increase of the wet surface due to the presence of the hulls below. Increasing the wet surface increases the resistance force and as a result the use of powerful engines in this type of ship. The purpose of this paper is to investigate the effect of spiraling the lower bodies and its effect on reducing the resistance force in a completely submerged state. In this paper, first, the effect of spiraling the lower bodies using a numerical method is compared. After proving the effectiveness of the proposed method, various parameters of the spiral body such as spiral depth, spiral length and rotation angle were examined. By integrating the optimized state of each of the parameters, a new spiral body was presented in which the resistance force was significantly reduced compared to the initial state.By reducing fuel consumption by spiraling submerged hulls, a new step will be taken to optimize Swath vessels.

Noise is unwanted sound in the ocean, since it generally, interferes with the operation of sonar or other underwater sound registration equipment. The principal sources of radiated sound from ships are (1) the propulsion system; (2) the propeller; (3) the auxiliary machinery; (4) the hydrodynamic effects and (5) the hull movements. One of the sources of artificial noise in the sea environment is the noise from the machines inside the vessels. This noise is caused by the inherent vibration of mechanical systems. The presence of small instabilities along with the forces and torques that produce the work creates vibrations that are eventually transmitted to the radiation surfaces and are therefore a source of noise. This type of noise is caused by the following 5 factors: mechanical unbalances, electromagnetic force fluctuations, impact sounds, piston sound in reciprocating machines and bearing noise. In this article, we only examine the noise generated by a floating machine and describe the frequency range as well as the noise level produced.

In this study, effect of eccentricity of a circle along the x-axis on the transformation of symmetric hydrofoil has been investigated using Zhukovsky mapping. The circle under study has a radius of 2 units, which is located at the origin of coordinates in the first case. In the first case, where the center of circle corresponds to origin of coordinates, the circle becomes a line and an ellipse and by moving the circle along the x-axis, a hydrofoil is obtained. The eccentricity of 0.4,0.2, 0.6, 1 and 1.5 have been studied and symmetric hydrofoils are calculated based on this mapping. The results indicate that as the eccentricity of the circle increases, the length of the hydrofoil decreases and the hydrofoil thickness increases. Up to eccentricity of a circle of 0.5, the maximum thickness occurs at a corresponding angle of 45 degrees and after this value occurs at the angle of 90 degrees.

Detection of small targets is usually done using infrared equipment and thermal detectors, so calculating the range of these systems is of particular importance, so Johnson's expression is the most important goal of this project. Also, in order to get acquainted with various strategies for hiding targets, familiarity with infrared waves is of special importance and plays an important role in categorizing and selecting the appropriate tools to achieve the overall goal of the project, namely the detection of small bird targets. The implementation of visible and infrared concealment methods has made it even more difficult to identify these targets, so we will examine these methods and provide methods to overcome these difficulties.Detection of small targets is usually done using infrared equipment and thermal detectors, so calculating the range of these systems is of particular importance, so Johnson's expression is the most important goal of this project. Also, in order to get acquainted with various strategies for hiding targets, familiarity with infrared waves is of special importance and plays an important role in categorizing and selecting the appropriate tools to achieve the overall goal of the project, namely the detection of small bird targets. The implementation of visible and infrared concealment methods has made it even more difficult to identify these targets, so we will examine these methods and provide methods to overcome these difficulties.

In this paper, the basic formulas of a three-phase induction motor are extracted and by Park_ Transfer Matrix are converted to dq space, then in m_file MATLAB software, are modeled and simulated. The aforementioned three-phase induction motor using cascade control and by A battery is set up and operated and controlled at different speeds. In the end, different diagrams of three-phase induction motor are presented in different working conditions. After carefully examining of the diagrams of three-phase induction motorو proves the accuracy of the proposed control method and its simulations. performance diagrams show that using the proposed control method, the motor can easily follow the reference speeds in the fastest possible time, which proves the accuracy of the modeling and simulations performed. By controlling the speed of induction motors, application of Direct Current motors in Navy of the Islamic Republic of Iran vessels, which are very expensive to maintain, can be eliminated.

This article was written after the construction of the first series of 113,000 ton Aframax tankers (out of four) in the Sadra Company, which is the result of the experiences of Sadra managers and experts. The purpose of this article is to exploit and use in ongoing and future shipbuilding projects .In this article, briefly discussed about the implementation process of this project and the problems along the way. It is hoped that while solving these problems, the way to develop the giant shipbuilding industry, which is undoubtedly one of the ways to reduce unemployment and create jobs.The issue of shipbuilding in Iran has long been a great aspiration of builders and one of them is domestic users, so that in recent years, domestic companies related to shipping and transfer of ships by ordering shipbuilding to domestic builders , A long hand was made to support them, but this did not happen, and the work reached a point where domestic sailing ships, instead of buying from inside, thought about their needs from foreign manufacturers. This made shipbuilders in Iran reasonable. However, there is experience in building small vessels in Iran and domestic manufacturers have a long history of building this type of vessel. This was the reason why domestic builders thought of building large ships in any way.

This paper discusses the design and development of a control system for the internal loop subsystem of an AUV. Using the multi-input multi-output (MIMO) nonlinear system state space approach, the linearized equation is obtained, and the desired conversion function is extracted from the corresponding linear equation. Then first examine the conversion function exposed to PID controller and then to PID_fuzzy type 2 controller, then using multi-objective genetic algorithm, fuzzy controller parameters including rules, input and output membership functions and optimal output gain Turns. And the results obtained in this method will be compared with similar previous worksThe proposed method in this research will be able to significantly improve the control parameters of the maximum value of the metamorphosis and the settling time of the system state variables. Of course, the proposed method will have a high volume of calculations in the nonlinear model and the slowness of the simulation process compared to previous works, which will also provide solutions to solve it.

SWATH Ship with two bodies under water have a very high transverse balance in the waves, but these ship have a higher wet surface due to the presence of the same hulls, and therefore their resistance force is higher than single-hull and catamaran ship. The aim of the present study was to investigate the effect of spiraling the lower bodies and its effect on reducing the strength of the resistor. In order to verify the claim, a pair of simple and spiral hulls were made and installed on the float. Tensile testing was performed in the laboratory in three modes of floating with a simple body, with a spiral body and floating without bodies for speeds between 0 and 6 meters per second. The results showed that the resistance force in a ship with a spiral body at all speeds is less than the other two states. By reducing fuel consumption by spiraling submerged hulls, a new step will be taken to optimize Swath vessels.