حل سه بعدی ارتعاشات آکوستیکی یک پوسته‌ استوانه‌ای در مجاورت یک جریان فروصوت

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری / مهندسی مکانیک، دانشگاه علم و صنعت ایران

2 دانشجوی کارشناسی ارشد / مهندسی فناوری ماهواره، دانشگاه علم و صنعت ایران

3 عضو هیات علمی / مهندسی مکانیک، دانشگاه علم و صنعت ایران

چکیده

در این مقاله افت انتقال صوت از یک پوسته استوانه­ای جدار نازک با طول بی‌نهایت با استفاده از تئوری سه بعدی الاستیسیته مورد تجزیه و تحلیل قرار می‌گیرد. پوسته بوسیله یک موج صوتی صفحه­ای تحریک می­شود درحالیکه در مجاورت یک جریان خارجی قرار دارد. درگام نخست معادلات حرکت استوانه در سه راستا بدست آمده است. با استفاده از تجزیه هلمهوتز، معادله حرکت را به دو معادله موج مجزا تجزیه کرده و با حل جداگانه هرکدام از این معادلات می­توان میدان جابجایی و تنش را بدست آورد. این روش رفتار ارتعاشی پوسته ها را نسبت به دیگر تئوری­ها از جمله تئوری کلاسیک و مرتبه اول و سوم برشی، به دلیل در نظر گرفتن از اثرات چرخش و برش، دقیق تر توصیف می کند.  به منظور صحت سنجی، نتایج مطالعه حاضر با نتایج تئوری­ کلاسیک مقایسه شده است. قابل مشاهده است که نتایج این تحقیق و تئوری­ کلاسیک با یکدیگر همخوانی خوبی دارند. همچنین تئوری کلاسیک به علت چشم پوشی از اثرات چرخش و برش در فرکانس­های بالا از دقت خوبی برخوردار نیست. نتایج نشان می­دهد که با افزایش ضخامت پوسته، به دلیل افزایش سفتی خمشی پوسته افت انتقال صوت افزایش یافته است. عدد ماخ به علت ایجاد سفتی منفی باعث کاهش افت انتقال صوت در ناحیه سفتی کنترل می­شود و بالعکس به­علت ایجاد دمپینگ در سازه باعث افزایش افت انتقال صوت در ناحیه جرم کنترل می شود . علاوه براین افزایش عدد ماخ منجر به افزایش فرکانس­های بحرانی و انطباقی می­گردد. 

کلیدواژه‌ها


عنوان مقاله [English]

Three-dimensional elasticity solution for vibro-acoustic behavior of cylinder in the presence of subsonic flow

نویسندگان [English]

  • Ali Tarkashvand 1
  • Mohamad Bolhasani 2
  • Kamran Daneshjo 3
  • Roohollah Talebitooti 3
1 Ph.D. Student, Mechanical Engineering Department, Iran University of Science & Technology
2 M.Sc.Student, School of Advanced Technologies, Iran University of Science & Technology
3 Professor, Mechanical Engineering Department, Iran University of Science & Technology
چکیده [English]

In this paper, the Three-dimensional (3-D) theory of elasticity has been used for sound transmission loss (TL) of a thin-walled cylindrical shell with infinite length. This structure is excited by an obliquely plane wave. Governing equations of the thin shell have been derived in radial, axial, and circumferential directions. Then, Helmholtz decomposition is applied to solve the equations. Therefore, the displacement field is considered in terms of Lame potential functions This method describes the vibrational behavior of the shells more accurately than other theories, including the classical theory and the first and third order of shear, due to the consideration of the effects of rotation and shear. A comparison of the present method results with those obtained from classical shell theory (CST) indicates an excellent agreement. However, at the high frequencies the classical encounter insufficient accuracies as a result of increasing the rotational terms as well as shear wave effects. The results show that with increasing shell thickness, due to increased flexural stiffness of the shell, the sound transmission loss has increased. By increasing the Mach number, due to the negative stiffness, reduces the sound transmission loss in the stiffness-controlled region and conversely increases the sound transmission loss in the mass-controlled region due to damping in the structure. Finally, it is shown that the critical and coincidence frequencies increase with the growing up Mach number.

کلیدواژه‌ها [English]

  • three dimensional theory of elasticity
  • Sound transmission loss
  • audio screen wave
  • Helmholtz decomposition
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