نوع مقاله: مقاله پژوهشی

نویسندگان

1 استاد دانشکده مهندسی دریا دانشگاه صنعتی امیرکبیر

2 کارشناس ارشد هیدرومکانیک کشتی دانشکده مهندسی دریا دانشگاه صنعتی امیرکبیر

چکیده

یکی از روش‌های موثر برای کاهش درگ در شناورهای پروازی استفاده از پله در کف بدنه شناور است. پله سبب کاهش سطح تماس بدنه شناور با آب شده و به تبع آن کاهش درگ شناور را بهمراه خواهد داشت. در این مقاله، اثر استفاده از دو پله‌ی عرضی بر روی عملکرد هیدرودینامیکی یک شناور پروازی چاین‌دار به روش عددی حجم محدود مورد بررسی قرار می‌گیرد. معادلات متوسط زمانی ناویراستوکس همراه با مدل اغتشاشی استاندارد k-ɛ کوپل‌شده با معادلات تسخیر حجمی سطح آزاد برای شبیه‌سازی جریان آشفته در اطراف بدنه شناور به کمک نرم افزار انسیس سی‌اف‌ایکس حل می‌شوند. به منظور اعتبارسنجی مدل عددی ارائه شده در این مقاله، ابتدا نتایج عددی محاسبه شده با نتایج آزمایشگاهی تانتون و همکاران مقایسه می‌شوند. سپس نتایج عددی بدست آمده برای نیروی درگ، توزیع فشار روی بدنه، سطح خیس‌شده، اسپری آب از چاین و الگوی موج اطراف بدنه‌ شناور در سرعت‌های مختلف ارائه و مورد تحلیل و بررسی قرار می‌گیرند. شناور پروازی دوپله مورد بررسی در مقایسه با مدل تک‌پله و بدون پله دارای مقاومت کمتری بوده که ناشی از جدایش جریان از پله و همچنین کاهش سطح خیس‌شده کف شناور می‌باشد. این پارامتر، به خودی خود باعث کاهش مؤلفه مقاومت اصطکاکی می‌شود. از طرفی دیگر، برخی اثرات منفی بر روی عملکرد هیدرودینامیکی در آب آرام مشاهده میشود که می‌توان به بزرگتر شدن ارتفاع سطح آزاد در پشت شناور و افزایش فشار هیدرودینامیکی در قسمت سینه، اشاره نمود. در عین حال، لازم به ذکر است که شناور دو‌پله دارای بازه تغییرات کوچکتری از زاویه تریم بوده و در مقایسه با حالت تک‌پله و بدون پله، کنترل رفتار طولی شناور را به طرز قابل توجهی، بهبود می‌بخشد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Numerical simulation of flow around a two-stepped planing hull in calm water

نویسندگان [English]

  • P Ghadimi 1
  • S Panahi 2

2 Amirkabir University of Technology Dept. of Maritime Engineering

چکیده [English]

One of the most effective methods for reducing the drag force on planning hulls is the use of steps at the bottom of the ship. A step reduces the wetted surface area and consequently decreases the drag. In this article, the effect of using two transverse steps on the hydrodynamic performance of a hard-chined planning craft is considered with finite element based finite volume method. Navier stokes average time equations are solved with standard k-ɛ turbulence model coupled with volume of fluid equations for simulation of free surface turbulent flow around the hull using the Ansys-CFX software. In order to validate the proposed numerical model in this article, the obtained numerical results are compared against experimental results of Taunton et al. Subsequently, the results pertinent to the drag force, pressure distribution on the hull, the wetted surface, the water spray from the chine and wave pattern around the considered hull are presented and analyzed. Double-stepped planing hulls are found to have smaller drag, since flow separates from the steps and lead to reduction of the wetted surface which itself leads to significant reduction of frictional resistance. Meanwhile, they indicate some negative effects in their hydrodynamic performance in calm water like larger free water elevation behind the transom and larger hydrodynamic pressure in their bow section. It should be mentioned that two-stepped planing hulls have a small variable trim angle in comparison with one-stepped and non-stepped hulls and also improve the control of longitudinal running attitude.

کلیدواژه‌ها [English]

  • Stepped-planing hulls
  • Steady motion
  • Calm Water
  • Drag force
  • Flow pattern

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