IJE TRANSACTIONS A: Basics Vol. 32, No. 4 (April 2019) 602-607    Article in Press

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H. Nourghassemi, H. R. Taghva, D. Molyneux and H. Ghassemi
( Received: May 03, 2018 – Accepted: March 07, 2019 )

Abstract    One of the most efficient methods of reducing drag on planing craft is the use of transverse step on the bottom of a hull. Applying steps on the hull reduces the contact area with water and as a result, it reduces drag of the craft. Planing craft are able to have one or two transverse steps. In this paper, numerical hydrodynamic performance of the stepped planing craft and its step height effect is investigated by making use of finite volume method (FVM). The Reynolds-Averaged Navier-Stokes (RANS) equations are coupled with the standard k- ε turbulence model and volume of fluid equations are solved to simulate transient turbulent free surface flow surrounding the hull by ANSYS-CFX. In order to predict the motion of the craft, equations of two degrees of freedom for rigid body are coupled with governing equations of fluid flow. In order to validate the numerical model presented in this paper, the obtained numerical results are compared with the available experimental data. The numerical results obtained for drag, dynamic trim, rising of center of mass and the pressure distribution on the body at different speeds and different heights of the steps are presented and discussed.


Keywords    Stepped Planing Craft; Transverse Step Height; Pressure Distribution; Lift and Drag



یکی از روشهای موثرو کارآمد برای کاهش درگ در شناورهای اسکی استفاده از پله های عرضی در کف شناور است. استفاده از پله باعث کاهش سطح خیس شده بدنه و در نتیجه موجب کاهش درگ می شود. شناورهای اسکی می توانند یک یا دو پله عرضی داشته باشند. در این مقاله با روش عددی عمکرد هیدرودینامیکی شناور اسکی پله دار و تاثیرارتفاع پله با روش حجم محدود مورد بررسی قرار گرفته است. معادلات ناویر استوکس به روش میانگین گیری رینولدز با مدل آشفتگی استاندارد k- ε برای شبیه سازی جریانهای سطح آزاد در اطراف بدنه شناور به کمک نرم افزار انسیس CFX حل شده است. بمنظور پیشگویی حرکت شناور، معادلات حرکت دو درجه آزادی با معادلات حاکم کوپل شده اند. جهت معتبرسازی، محاسبات نتایج عددی بدست آمده با نتایج تجربی مقایسه شده است. نتایج عددی بدست آمده شامل درگ، تریم دینامیکی، بالا امدن مرکز جرم، توزیع فشار روی بدنه در سرعتهای مختلف و در چند ارتفاع پله ارائه و بحث شده است.


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