نویسندگان
دانشکده مهندسی مکانیک، دانشگاه یزد
چکیده
مطالعه حاضر، تحلیل عددی پدیده فروریزش ستون‌های مواد دانه‌ای را به‌کمک روش هیدرودینامیک ذرات هموار و یک رابطه ساختاری محلی پیشنهاد شده توسط ژوپ و همکاران، ارائه می‌دهد. این روابط ساختاری بر پایه ماهیت متراکم جریان توده دانه‌ای به‌عنوان یک جریان ویسکوپلاستیک بیان می‌شود که ویسکوزیته را به‌اندازه نرخ کرنش محلی و میدان فشار محلی مرتبط می‌کند. پارامترهای رئولوژی از طریق نتایج تجربی تعیین شده است. یک روش ساده برای منظم‌سازی مقدار ویسکوزیته پیشنهاد شد تا شرایط توقف و سطح آزاد جریان گرانشی که فشار آن صفر است را فراهم سازد. نوسانات فشار به‌عنوان اشکال اصلی در روش "هیدرودینامیک ذرات هموار تراکم‌پذیر ضعیف" منجر به توزیع نامناسب فشار می‌شود. در این مقاله، یک الگوریتم جدید برای حذف نوسانات غیرفیزیکی با مرتبط کردن دیورژانس سرعت به لاپلاسین فشار پیشنهاد شده است. شبیه‌سازی‌های صورت گرفته برپایه الگوریتم پیشنهادی به‌خوبی دینامیک جریان دانه‌ای مشاهده شده در نتایج تجربی را نشان می‌دهد. ضخامت بیشینه جریان دانه‌ای روی سطح شیب‌دار بر اساس مدل رئولوژی محلی و مقادیر تجربی تعیین شد و با نتایج عددی مقایسه شد. فاصله پیشروی نهایی و شیب نشست به‌دست آمده از شبیه‌سازی‌ها با مقادیر تعیین شده از آزمایش‌های تجربی کاملاً سازگاری داشت. نتایج نشان می‌دهد که نسبت ستون اولیه نقش مهمی در پخش توده دانه‌ای و شکل نشست نهایی ستون ایفا می‌کند.
کلیدواژه‌ها
عنوان مقاله [English]
Numerical Simulation of Granular Column Collapses with Pressure-Dependent Viscoplastic Model using the Smoothed Particle Hydrodynamic Method
نویسندگان [English]
- A. M. Salehizadeh
- A. Shafiei
چکیده [English]
This paper presents a numerical analysis of granular column collapse phenomenon using a two-dimensional smoothed particle hydrodynamics model and a local constitutive law proposed by Jop et al. This constitutive law, which is based on the viscoplastic behaviour of dense granular material flows, is characterized by an apparent viscosity depending both on the local strain rate and the local pressure. The rheological parameters are directly derived from the experiments. A simple proposed regularization method used in the viscosity relation to reproduce the stopping condition and the free surface of a granular flow where the pressure is disappeared. Pressure oscillation, as the main disadvantage of the weakly compressible SPH method, leads to an inaccurate pressure distribution. In this research, a new algorithm is proposed to remove the nonphysical oscillations by relating the divergence of velocity to the Laplacian of pressure. The simulations based on the proposed SPH algorithm satisfactorily capture the dynamics of gravity-driven granular flows observed in the experiments. The maximum thickness of a granular flowing on a rough inclined plane is obtained based on the local rheology model and compared with the experimental results. The run-out distances and the slopes of the deposits in the simulations showed a good agreement with the values found in the experiments. The results of the simulation proved that the initial column ratio played an important role in spreading the granular mass
کلیدواژه‌ها [English]
- Dense Granular Material
- Smoothed Particle Hydrodynamics
- Pressure Dependent Visco-Plastic
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