فهرست مطالب

مهندسی شناورهای تندرو - پیاپی 47 (پاییز و زمستان 1394)

نشریه مهندسی شناورهای تندرو
پیاپی 47 (پاییز و زمستان 1394)

  • تاریخ انتشار: 1394/12/25
  • تعداد عناوین: 10
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  • Mojtaba Pakian *, Abdorrahim Keshtkar, Muhammad Saadatabadi Page 4
    Depending on the type of mission high speed craft, reducing engine noise is essential. To reduce noise, amuffler system is used, that is installed in the exhaust outlet. Sample Study to reduce noise, is MTU 183 AA diesel. Due to natural aspirated system, it has a lot of sound and noise. Analysis of computational fluid method and software FLUENT is used. In this study, to reduce engine noise, back pressure has been noted that not out of range. The results show that the use of perforated tube in passive reflection silencer, noise reduction is acceptable. The passive reflection silencer was designed to reduce the noise to an acceptable level and the back pressure does not rise. The numerical results obtained from CFD compared with experimental results are satisfactory.
    Keywords: High speed craft, diesel generator, exhaust silencer, Resistive element Reactive element
  • Hasan Rezapour Kourandeh, Mehdi Mohammad Beigi, Mojtaba Bahraini Page 14
    Laser is the most important invention of the first half of the twentieth century with many applications in communications, industry and medicine. This invention has been used from the late of 1980-1990 decade as an identifying weapon besides radar. In 1990-2000 decade the design and production of high power guided energy weapons was started and used as an anti-missile and nuclear weapons for world big power armies. In this paper, after a complete introduction about Laser, guided energy weapons and expressing their merits and weaknesses, based on absorbtion, scattering and reflection phenomanas of Laser beam, we present our available scientific methods to defense high speed crafts and other navy targets against these modern Laser weapons.
    Keywords: Electromagnetic, Laser, High power Laser weapons, Laser defence, free electron, High speed craft
  • Abbas Dashtimanesh*, Mohammad Gholizad Page 28
    Stepped planning hulls are one of the main innovations in the field of hull hydrodynamics which lead to wetted surface reduction and performance improvement. Nowadays, many of boat building industries such as Madera use stepped hulls design. However, there is no simple method for performance prediction of such hulls. Therefore, the main aim of the current study is development of a mathematical model for trim and resistance prediction of two stepped hulls. The basic of mathematical model is similar to Savitsky64. Presented mathematical model divides the two stepped hull to three parts and by assuming linear flow separation from steps, wetted surfaces are recognized. Finally, using an iterative solution, trim and resistance of two stepped hull are obtained. For validation, the obtained results using mathematical model are compared against experimental data of Southampton series model C2. Comparisons prove the capability of presented mathematical model for appropriate performance evaluation of two stepped hulls at conceptual design phase.
    Keywords: Planning craft, Mathematical model, two stepped hull, Resistance, Trim
  • Alireza Marzban*, Mojtaba Nematzadeh, Ali Ebrahimpour Page 36
    Yamaha 250 four stroke petrol engine thrust is removed from its original form and is so deformed after a time period of performance. Regarding the importance of this engine in combat operations, the need to investigate the causes of the failure of this piece gets more imperative. In this study, simulation and element finite analysis of the tension on the thrust in crisis mode using ABAQUS software will be taken into account after examining and identifying common type of steel used in bearings. Analysis in three modes is calculated: without friction, friction and when thrust is exposed to abrasion. The first mode is assumed that the coefficient of friction interface between thrust and shaft is small so that we can assume that without friction in the definition of the contact between two levels in the software. The second mode, the analysis will be discussed assuming that the coefficient of friction between the thrust and shaft has been calculated. And in the third mode, regarding the wear of thrust during engine operation, we will actually analyze and discuss it. Finally, the discussed results and suggestions in order to improve performance will be presented.
    Keywords: Thrust, Yamaha 250 four stroke petrol engine, ABAQUS, simulation
  • Mehdi Rishehri, Mohammad Mehdi Mobasheri Zafarabadi, Ali Dehghanian Page 50
    According to the Freight Investor Services Institute, A $0.5 increase in crude oil prices lead to Fuel price increases to three dollars per ton. Over the past five years, Fuel prices have more than doubled. So Ship owner's profit maybe is very little. If crude oil prices increased 10%, Ships fuel price increases 10 at the same day. The advantages of fuel reduction methods as the methods to save of ships fuel consumption are reduce in air pollution, the consumption of oil products, transport subsidies, increasing safety and other economic resources. So even the smallest change in ship's hull drag reduction and fuel consumption reduction has important effects in financial economics. Also the speed of marine vehicle especially high speed crafts is a problem that even the smallest improve is attractive for many of researchers and military research centers. The most important factor in crafts fuel consumption is hull resistance. Also the most important parameter in hull resistance is skin friction resistance. According to wet surface area and kind of environment flow it is changeable. There are different techniques to increase of full speed at the constant power (or reduce of power at constant ship speed). In this paper present review of published paper to introduce the method of air injection in wet surfaced of ships to reducing hull drag, fuel consumption and increasing ship speed.
    Keywords: Friction drag reduction, Air injection, Fuel consumption reduction, Air cavity ships
  • Musa Safarpour, Abbas Yazdani *, Seyyed Mahdi Sajedi Page 68
    In this paper, using aluminum in the body of high speed craft , the performance of each of the structural elements have been examined individually. we have also examined failures and arbitrary floating structures by showing realistic images of various parts of the structure, to make the reader more aware and familiar. In addition, in this study, the behavior of an element of structure in residual stress caused by heat of fusion joining process has been taken into consideration. Finally, we have tried to simulate the way of giving response in the software by analyzing its behavior in different parts of the structure in different conditions.It should be noted that the use of aluminum for its light weight and resistance to corrosion is widely growing in the world. However, it will lose its required strength easily and lack necessary performanc (efficiency) due to inadequate heat of fusion joints. Therefore, there is no proper place or position to use of these materials in shipbuilding industries.
    Keywords: HSCstructure of AL Residual stress(tension), welding joint
  • Aliasgharmoghaddas Ahangari, Seyed Khalil Shariati, Esmaeil Heydari, Taghi Aliakbari Page 78
    Measurement of resistance force acting on the underwater vehicles has some methods such as numerical method. Because of economical and equipmental reasons the numerical methods has more users than other methods. When this methods has insurance that the result has been validated by experimental results. In this paper, resistance force of spheral body in STAR CCM software has calculated and compare with experimental results that measured by towing tank tests. According to the sphere size and test speed, the flow is in laminar regime, so The result of the CFD Analysis ant towing tank test has validated in this regime.
    Keywords: resistance test, sphere, Star CCM
  • Saeed Jaamei, Alireza Heydarian*, Alireza Kazemipour Page 84
    In recent years, ship transportation has been become in the interests, as well as land and air transportation. There has been an attempt so as to reduce the drag which exerts on vessels. Surely, if drag is considered to be on a downward trajectory it will be significant to have series of examinations. In this essay, nature is taken into consideration as a model in order to achieve the aforesaid purpose. By studying the high speed aquatic animals such as sharks and dolphins, and also their skin, the idea of utilizing riblet on the hull of vessels has ushered in maritime science. Among various methods of skin friction drag reduction, the use of riblet. For this reason there is an interest for construction and optimization of riblet as efficient and economical way. In this research, for first time the shark’s skin was modeled on ANSYS CFX by using numerical simulation and Computational Fluid Dynamics, and then the effects of riblet on a submerged flat plate were analyzed. Different types of riblet based on height and space between micro channels were studied, and later on comparison between a ribletcovered plate and a smooth plate in various velocities were done. In the final, it is declared that by selecting the most appropriate type of riblet, 11% drag reduction is attained. Then, by comparing different types of riblets, selected the best choice for drag reduction. Furthermore, the obtained results were compared with the experimental ones.
    Keywords: Drag reduction, Shark, Flat plate, Riblet, CFD analysis, ANSYS CFX, Micro channels