فهرست مطالب

مهندسی شناورهای تندرو - پیاپی 42 (بهار و تابستان 1392)

نشریه مهندسی شناورهای تندرو
پیاپی 42 (بهار و تابستان 1392)

  • تاریخ انتشار: 1392/04/15
  • تعداد عناوین: 8
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  • S. H.Hossini, M. H.Karimi, A.Rahbarranji Page 4
    Design and construction of floating structures requires understanding the behavior of these structures in various environmental conditions. The dynamic response of structures to various environmental stimuli such as force caused by waves, wind and sea currents can be very helpful in achieving this goal. Slamming Phenomenon Increase the speed of threshing process, the parameters of which are now in the design of modern vessels, especially vessels Extremist is highly regarded. In this paper a number of methods to predict hydrodynamic loads from waves and shock loads in the design are discussed A unique feature of this theory is summarized.
    Keywords: Slamming, High Speed Boat, Waves shock loads, Time history prediction
  • A. R.Kohansal, H.Ghasemi Page 16
    The planingstatus on the planing crafts is important regarding to hydrodynamic view point. When the craft is moving from low speed to the high speed, the physical condition of the crafts changes and hydrodynamic forces applied to the hull are different at these two speeds. In the high speed, the craft is planing and rise-up, so the dynamic pressure is much dominant relative to static pressure. Planning crafts are designed at high speed where the flow is very complex around. Spray is produced in the fore part and flow separation created in the aft part (transom). Therefore, free surface is non-linear due to spray and transom flow separation. In this paper, geometrical and hydrodynamical characteristics are studied using potentialbased boundary element method. The method is described and some numerical results of the pressure distribution and hydrodynamics forces are presented.
    Keywords: planing crafts, hull form, pressure distribution, drag, lift
  • M.Mazinani Page 28
    In this article, we have studied the High speed semi-submersible vehicle with wings using the test results of some specific models and analyzed the hydrodynamic parameters and wave making resistance. The vehicle is called HSV (High speed Semi-submersible Vehicle with wings) here, is consisting of a main hull, main wings and a strut. The HSV floats at a certain draft like a conventional ship while it is still, and it submerged when it moves forward due to a downward lift force induced by the main wings. The lift force by the main wings at the various submergence depths remarkably reduces the wave making resistance. The wings contribute to reduce the wave making resistance by making the hall submerged and also through the cancellation of the waves generated by the hull. The hydrodynamics viewpoint, the estimation of the effective horsepower using the empirical methods and available equations for these vehicles is still not actually acceptable. However, it can be expected that the wave making resistance is still more reduced by the modification of the hull and wing forms. On the other hand, a half the estimated horsepower was frictional resistance component and an innovative means must be necessary for the frictional resistance to be reduced.
    Keywords: semi, submersible vehicle, wave making resistance, wing, strut
  • E.Nikravan Page 38
    Sea minefields obstructing naval missions have to be breached with minimum effort and acceptable risk. With the advent of autonomous mapping, it is feasible to have high quality information of obstructing sea minefields and their environment before moving into them. The challenge remains to use this knowledge optimally to minimize risk, time and effort in crossing the sea minefield. To achieve this, two interlinked processes are required, consisting of finding the shortest route with acceptable risk or route with minimum risk through the sea minefield This paper describes the use of Dijkstra’s algorithm to achieve practical strategies and a method in which two optimization techniques interact to provide a safe route considering the risk of both the sea mine and the environment and making it applicable to sea mine avoidance. This methodology may readily be applied to general ship routing in risk areas and may be expanded to routing through any area where no known routes exist.
    Keywords: Routing, route finding, mapped sea minefield, Dijkstra's algorithm, Optimization
  • A.Asadzade, S.Aliakbari Page 46
    In this article, we study the position of sonar and the possibility of using it in small high speed boats. First, the subject is studied from different aspects and the problem of sonar designing in these boats are stated. Then, two designs were proposed that it is possible to beapplicable. Finally, by the primary calculations, the optimization of 37.7 decibel in sonar equation is proved between the first and second design. Also, for the proposed design to be applicable, hydrodynamic calculations were presented, too.
    Keywords: sonar, absorption coefficient, active, passive, roll, pitch, hydrodynamics, diffusion loss, noise level, favorite array coefficient
  • J.Abbasi, E.Faghih Page 54
    Given the importance of energy in the world today on the one hand and speed in the shipping and marine operation on the other, decreasing the hydrodynamic resistance of vessels to obtain a higher speed and decreasing the fuel consumption are the preferences of ship designers. In this regard, using the hydrofoil in small vessels because of the ratio of lift to high drag has particular importance. In this article it was tried after introducing a short history of accomplished tasks in the field of equipping common catamarans / Hiscot to hydrofoil, different kinds of resistance against the movement of these vessels will be studied depending on the resistance to affect the hydrofoil performance installed in catamaran tunnel. Then, through computational fluid dynamics, it was tried to calculate the dynamic coefficients for a hydrofoil number of Naka series.
    Keywords: hydrofoil, catamaran, turbulence model, lift, drag force