بررسی اثر تغییر نیم موج‌های محیطی بر فرکانس‌های طبیعی پوسته‌های استوانه‌ای در ارتعاشات زیر آب به‌صورت تجربی و عددی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی مکانیک، دانشکده فنی و مهندسی، دانشگاه جامع امام حسین (ع)، تهران، ایران

2 گروه مهندسی مکانیک، دانشگاه جامع امام حسین (ع)

3 دانشکده فنی و مهندسی، دانشگاه جامع امام حسین(علیه السلام)، تهران، ایران،

4 دانشکده فنی و مهندسی، دانشگاه جامع امام حسین(علیه السلام)، تهران، ایران

چکیده

در پژوهش حاضر، اثر تغییر نیم موج‌های محیطی بر فرکانس‌های طبیعی پوسته‌های استوانه‌ای به‌صورت تجربی و عددی بررسی شده ‌است. سه پوسته استوانه‌ای با نسبت قطر به طول متفاوت مورد بررسی قرار گرفتند. حالت‌های مختلف تماس با آب هم با روش شبیه‌سازی عددی و هم آزمون‌های تجربی مورد مقایسه واقع شدند. اثرات عمق غوطه‌وری، نسبت قطر به طول، روند تغییرات فرکانس طبیعی در نیم موج‌های محیطی مختلف مورد ارزیابی قرار گرفت. بررسی‌ها نشان داد که کاهش فرکانس‌های طبیعی پوسته استوانه‌ای برای نیم موج‌های محیطی مربوط به فرکانس کمینه، اندک و برای قبل و بعد این نیم موج محیطی، بیشتر است و در آغاز غوطه‌وری و در غوطه‌وری کامل، کاهش فرکانسی به‌صورت ناگهانی است. همچنین با کاهش نسبت قطر به طول پوسته، فرکانس‌های مربوط به نیم موج‌های محیطی پایین کاهش یافته و کمترین مقدار فرکانس طبیعی به سمت نیم موج‌های محیطی کمتر متمایل می‌شود. در نیم موج‌های محیطی پایین، فرکانس‌های طبیعی، اختلاف قابلتوجهی دارند و با افزایش شماره n، این اختلاف کاهش یافته و به یکدیگر هم‌گرا می‌شوند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation effect of circumferential mode number on natural frequencies of under-water vibrations of cylindrical shells numerically and experimentally

نویسندگان [English]

  • Mohammad Reza Najafi 1
  • Saeed Mahjoub Moghadas 2
  • Seyyed Mohammad Mortazavi 3
  • Mahmoud Salari 4
1 Mechanical Engineering Department, Imam Hossein comprehensive University
2 Department of Mechanical Engineering, Imam Hosein comprehensive university, Tehran, Iran
3 Department of Mechanical Engineering, Imam Hosein comprehensive university, Tehran, Iran
4 Department of Mechanical Engineering, Imam Hosein comprehensive university, Tehran, Iran
چکیده [English]

In the present study, the effect of circumferential mode number on natural frequencies of cylindrical shells was investigated numerically and experimentally. Three cylindrical shells with different diameter to length ratios were examined. Different contact type with water were compared using both numerical simulation and experimental tests. The effects of immersion depth, diameter to length ratio, variations of natural frequency with different circumferential mode number were investigated. The reduction of the natural frequencies of the cylindrical shell for the minimum frequency of different circumferential mode number is low, but it increases for higher and lower frequencies, and at the beginning of immersion and at full immersion, the frequency decreases suddenly. Also, as the ratio of diameter to shell length decreases, the frequencies of the low circumferential mode number decrease and the lower value of the natural frequency tends to lower circumferential mode number. At low circumferential mode number, the natural frequencies differ considerably, and with increase of n number, the difference decreases and converges.

کلیدواژه‌ها [English]

  • Circumferential mode number
  • Fluid-solid interaction
  • Under-water vibrations
  • natural frequency
  • mode shape
Rao, Singiresu S., “Vibration of continuous systems”, Vol.464, New York, Wiley, 2007.
[2] Senjanović, Ivo, Marko Tomić, Nikola Vladimir, and Neven Hadžić, "An analytical solution to free rectangular plate natural vibrations by beam modes–ordinary and missing plate modes", Transactions of FAMENA, 2016, Vol.40, no.3, pp.1-18.
[3] Blevins, Robert D., “Formulas for dynamics, acoustics and vibration”, John Wiley & Sons, 2015.
[4] Frymoyer, Edward Morris, “Vibration and Wave Propagation in Cylindrical Shells”, Pennsylvania State Univ University Park Ordnance Research Lab, 1967.
[5] Alujević, Neven, Nuria Campillo-Davo, Peter Kindt, Wim Desmet, Bert Pluymers, and Stijn Vercammen, "Analytical solution for free vibrations of rotating cylindrical shells having free boundary conditions", Engineering structures, 2017, Vol.132, pp.152-171.
[6] Clary, R. R., and J. D. Watkins, "Vibrational characteristics of some thin-walled cylindrical and conical frustum shells", 1965.
[7] Palacios Gomez, Oscar F., "Vibrations of preloaded cylindrical shells", PhD diss.University of Leicester, 1970.
[8] Ugural, Ansel, “Stresses in plates and shells”, McGraw-Hill, 1999.
[9] Soedel, Werner, and Mohamad S. Qatu, "Vibrations of shells and plates", 2005, pp.1683-1683.
[10] Goncalves, P. B., and R. C. Batista, "Frequency response of cylindrical shells partially submerged or filled with liquid", Journal of Sound and Vibration, 1987, Vol.113, no.1, pp.59-70.
[11] Senjanović, Ivo, Marko Tomić, Nikola Vladimir, and Neven Hadžić, "An analytical solution to free rectangular plate natural vibrations by beam modes–ordinary and missing plate modes", Transactions of FAMENA, 2016, Vol.40, no.3, pp.1-18.
[12] Missaoui, J., Li Cheng, and M. J. Richard, "Free and forced vibration of a cylindrical shell with a floor partition", Journal of Sound and Vibration, 1996, Vol.190, no.1, pp.21-40.
[13] Lakis, A. A., and S. Neagu, "Free surface effects on the dynamics of cylindrical shells partially filled with liquid", Journal of Sound and Vibration, 1997, Vol.207, no.2, pp.175-205.
[14] Jeong, Kyeong-Hoon, and Kwi-Ja Kim, "Free vibration of a circular cylindrical shell filled with bounded compressible fluid", Journal of Sound and Vibration, 1998, Vol.217, no.2, pp.197-221.
[15] Ergin, A., and P. Temarel, "Free vibration of a partially liquid-filled and submerged, horizontal cylindrical shell," Journal of Sound and vibration, 2002, Vol.254, no.5, pp.951-965.
[16] Zhang, G. J., T. Y. Li, X. Zhu, J. Yang, and Y. Y. Miao, "Free and forced vibration characteristics of submerged finite elliptic cylindrical shell", Ocean Engineering, 2017, Vol.129, pp.92-106.
[17] Askari, Ehsan, and Kyeong-Hoon Jeong, "Hydroelastic vibration of a cantilever cylindrical shell partially submerged in a liquid", Ocean Engineering, 2010, Vol.37, no.11-12, pp.1027-1035.
[18] Paak, M., M. P. Paidoussis, and A. K. Misra, "Nonlinear vibrations of cantilevered circular cylindrical shells in contact with quiescent fluid", Journal of Fluids and Structures, 2014, Vol.49, pp.283-302.
[19] Naumova, Natalia, Denis Ivanov, Tatiana Voloshinova, and Boris Ershov, "Mathematical modelling of cylindrical shell vibrations under internal pressure of fluid flow", In 2015 International Conference on Mechanics-Seventh Polyakhov's Reading, pp.1-3, IEEE, 2015.
[20] Bochkarev, S. A., S. V. Lekomtsev, and V. P. Matveenko, "Natural vibrations of loaded noncircular cylindrical shells containing a quiescent fluid", Thin-Walled Structures, 2015, Vol.90, pp.12-22.
[21] Rahmanian, M., R. D. Firouz-Abadi, and E. Cigeroglu, "Dynamics and stability of conical/cylindrical shells conveying subsonic compressible fluid flows with general boundary conditions", International Journal of Mechanical Sciences, 2017, Vol.120, pp.42-61.
[22] Guo, Wenjie, Tianyun Li, Xiang Zhu, Yuyue Miao, and Guanjun Zhang, "Vibration and acoustic radiation of a finite cylindrical shell submerged at finite depth from the free surface", Journal of sound and vibration, 2017, Vol.393, pp.338-352.
[23] Wang, Peng, Tianyun Li, and Xiang Zhu, "Free flexural vibration of a cylindrical shell horizontally immersed in shallow water using the wave propagation approach", Ocean Engineering, 2017, Vol.142, pp.280-291.
[24] Guo, Wenjie, Tianyun Li, Xiang Zhu, and Yuyue Miao, "Sound-structure interaction analysis of an infinite-long cylindrical shell submerged in a quarter water domain and subject to a line-distributed harmonic excitation", Journal of Sound and Vibration, 2018, Vol.422, pp.48-61.
[25] Shariati, Seyed Khalil, and Saeed Mahjob Mogadas, "Vibration analysis of submerged submarine pressure hull", Journal of vibration and acoustics, 2011, Vol.133, no.1.
[26] Zienkiewicz, O. C., "Coupled vibrations of a structure submerged in a compressible fluid", In Proc. of Symposium on Finite Element Techniques Held at the University of Stuttgart, 1969.
[27] Zienkiewicz, O. C., and R. L. Taylor, "The finite element method, Butterworth Heinemann", 2000.
[28] Paidoussis, Michael P., “Fluid-structure interactions: slender structures and axial flow”, Vol.1, Academic press, 1998.
[29] شریعتی، خ.،" تحلیل ارتعاشات آزاد پوسته‌های استوانه‌ای تقویت شده مغروق با استفاده از نرم‌افزار انسیس"، 1385، پایان نامه کارشناسی ارشد، دانشگاه جامع امام حسین (علیه السلام).