بررسی تجربی اثر زاویه برخورد طوفان فرو وزشی بر سازه‌ مکعب شکل- قسمت دوم: مشاهدات طوفان فرو وزشی کوچک متحرک

نوع مقاله : علمی پژوهشی

نویسندگان

1 استادیار، دانشکده فنی مهندسی، مرکز تحقیقات هوافضا و تبدیل انرژی، واحد نجف آباد، دانشگاه آزاد اسلامی، نجف آباد، ایران

2 دانشجوی کارشناسی ارشد، دانشکده عمران،‌ واحد نجف آباد، دانشگاه آزاد اسلامی، نجف آباد، ایران

3 استادیار، دانشکده عمران،‌ واحد نجف آباد، دانشگاه آزاد اسلامی، نجف آباد، ایران

چکیده

 طوفان های فرو وزشی با ایجاد جریان های ناپایای ریزشی قوی، باعث تخریب های شدید می شوند. از طرفی با توجه به تفاوت ساختار آنها با طوفان های لایه مرزی اتمسفری، بررسی و شناخت‌ این جریانات در شرایط مختلف اهمیت دارد. لذا در این تحقیق به بررسی تأثیرات برخورد طوفان فرو وزشی در زوایا و راستاهای متفاوت در حالت دینامیکی بر روی مدل مکعب شکل پرداخته شده است. این مدل، در چهار زاویه  قرارگیری مختلف نسبت به راستای ریزش جریان(θ)، دو راستای برخورد جریان سطحی(α) و در محدوده شعاعی 5/1±X/D= قرار گرفته است. همچنین نسبت سرعت انتقالی افقی این طوفان(VR)، 06/0 و 12/0 در نظر گرفته شده است. نتایج نشان می دهد که افزایش θ و VR، باعث شده تا ضریب فشار بیشینه، از نقطه مرکزی فرود جریان(۰X/D=) به سمت پایین دست جریان متمایل شود. همچنین افزایش زاویه α باعث کاهش بازه تغییرات فشار و نیرو در حدود 25٪ بر مدل شده است. به علاوه مشخص شد که طوفان های فرو‌وزشی در حالت دینامیکی ضربات قوی تری بر سازه وارد نموده و عمومأ قویترین ضربات،‌ بلافاصله بعد از عبور طوفان از روی سازه رخ داده است.
 

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