تاثیر آب روی عرشه بر دوشاخگی رول شناورها تحت موج های تصادفی

نوع مقاله : مقاله مکانیک

نویسنده

دانشگاه شیراز

چکیده

پایداری حرکت رول شناورها به دلیل تاثیرهای بزرگی که بر روی ایمنی، راحتی سفر، عملکرد کلی و واژگونی احتمالی سیستم دارد از اهمیت خاصی برخوردار است. مطالعه این حرکت و بررسی پایداری دینامیکی آن که دارای معادلات غیرخطی و بسیار حساس به شرایط جوی، بارهای نامتقارن و وجود آب بر روی عرشه شناور است از اهمیت ویژه ای برخوردار است. در این تحقیق تلاش شده است تا پایداری این حرکت در شرایط ذکر شده و تحت موجهای تصادفی نویز سفید بصورت کاملا تحلیلی مطالعه شود. به این منظور تابع چگالی احتمال پاسخ با بکارگیری روش فوکر پلانک کولموگروف و حل ایستای معادله دیفرانسیل پاره ای متناظر بصورت تحلیلی بدست آمد و سپس تاثیر وجود آب بر روی شناور، ممان انحراف ناشی از بار نامتقارن یا باد عرضی، مقدار میرایی و شدت ممان تصادفی بر پایداری بررسی شد. روابط بصورت بدون بعد استخراج شد تا امکان اعمال آن بر طیف وسیعی از شناورها وجود داشته باشد. نتایج بدست آمده، همانطور که انتظار میرفت، از تغییر ماهوی و دوشاخگی رفتار در حالت وجود آب بر روی عرشه حکایت دارد. وضعیت پایداری 3 گونه از شناورها بررسی و مشخص شد که در حالت وجود آب بر روی عرشه، ناپایداری کاملا متاثر از گونه شناور است.

کلیدواژه‌ها


عنوان مقاله [English]

The Effect of Water on Deck on the Roll Bifurcation of Crafts under Random Waves

نویسنده [English]

  • asnafi asnafi
shiraz university
چکیده [English]

The stability of the roll motion of crafts is of great importance because of its significant impact on safety, ease of travel, overall performance and potential capsizing of the system. It is important to study this motion and to investigate its dynamic stability, which is completely nonlinear and highly sensitive to atmospheric conditions, asymmetric loads and the presence of water on the deck. In this research, it was tried to study the stability of the roll motion under the pointed conditions and random white-noise waves analytically. To do this, the probability density function of response was obtained using the Fokker Planck Kolmogorov (FPK) method and the stationary solution of the corresponding partial differential equation. Then, the effect of water on the deck, deviation moment due to the asymmetric load or crossing winds, the damping coefficient and the intensity of the random wave was investigated. Introducing non-dimensional parameters, the equation of roll motion was derived so that it could be applied to a wide range types of crafts. The results, as expected, indicate a significant qualitative change i.e. a bifurcation in the behavior when we have water on the deck. The stability of three types of the crafts is also studied and it is shown that in the presence of water on the deck, the type of craft can completely effect on instability phenomenon.

کلیدواژه‌ها [English]

  • Dynamic stability
  • Roll stability
  • FPK Equation
  • Bifurcation
  • Stochastic analysis
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