تاثیر فینلت های کاهش دهنده نوفه بر میدان جریان آشفته در محدوده لبه فرار صفحه تخت

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی هوافضا، دانشگاه علوم و فنون هوایی شهید ستاری، ایران

2 پروفسور، دانشکده مهندسی مکانیک، دانشگاه یزد، یزد، ایران

3 گروه پیش‌برنده. دانشکده مهندسی هوافضا. دانشگاه علوم و فنون هوایی شهید ستاری. تهران. ایران

4 دانشکده مهندسی هوافضا، دانشگاه علوم و فنون هوایی شهید ستاری، تهران، ایران

چکیده

مطالعه نوفه لبه‌فرار لایه مرزی آشفته، موضوعی بنیادی در طراحی و تولید وسایل پرنده با حداقل نوفه است. در طول دهه‌های گذشته، روش‌های غیرفعال مختلفی برای کاهش نوفه لبه‌فرار پیشنهاد شده و جدیدترین راهبرد، استفاده از فینلت‌های کاهش‌دهنده نوفه است. در مطالعه حاضر، به منظور بررسی نحوه تاثیر فینلت‌های کاهش‌دهنده نوفه بر میدان جریان آشفته در محدوده لبه فرار مدل، یک صفحه تخت مجهز به سنسورهای اندازه‌گیری فشار ناپایای سطح، طراحی و ساخته شده است. سپس با نصب مجموعه‌ای از فینلت‌ها با فواصل عرضی مختلف روی صفحه تخت، اثرات حضور آن‌ها روی میدان جریان در پایین‌دست فینلت‌ها به صورت تجربی مورد بررسی قرار گرفته است. نتایج نشان داد که رفتار جریان در پایین دست فینلت‌ها، به شدت وابسته به فاصله عرضی بین فینلت‌هاست. در حالی‌که استفاده از فینلت‌های درشت، منجر به کاهش سرعت متوسط، شدت آشفتگی و محتویات انرژی ساختارهای آشفته فرکانس پایین در نقاط نزدیک به سطح مدل در پایین‌دست فینلت‌ها می‌گردد، رفتار جریان در پایین-دست فینلت‌های ریز تا حدودی مشابه جریان در پایین‌دست پله رو‌به‌عقب است. برای فینلت‌های ریز، محتویات انرژی ساختارهای آشفته جریان در نواحی نزدیک به سطح در تمامی محدوده فرکانسی، کاهش قابل توجهی یافته است. نتایج همبستگی متقابل و تابع همدوسی بین نوسانات فشار سطح و میدان سرعت نیز نشان داد که در حالی که مهمترین مکانیزم موثر بر نوسانات فشار سطح برای فینلت‌های درشت، جریان کم مومنتوم خروجی از بین فینلت‌هاست، برای فینلت‌های ریز، ساختارهای گردابه‌ای تشکیل شده بواسطه جدایش جریان سهم موثری بر نوسانات فشار سطح در پایین دست فینلت‌ها دارد.

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