Low-frequency vibrations of a cylindrical shell rotating on rollers

2018 ◽  
Author(s):  
S. B. Filippov
Keyword(s):  
Cylindrical Shell ◽  
Low Frequency

scholarly journals Simulation and analysis on low-frequency scattering characteristics of the finite cylindrical shell in shallow water

2019 ◽  
Vol 283 ◽  
pp. 03007
Author(s):  
Jinyu Li ◽  
Dejiang Shang ◽  
Yan Xiao
Keyword(s):  
Cylindrical Shell ◽  
Free Space ◽  
Acoustic Scattering ◽  
Low Frequency ◽  
Target Strength ◽  
Wave Direction ◽  
Scattering Field ◽  
Simulation Results ◽  
Finite Cylindrical Shell ◽  
Target Locations

Low-frequency acoustic scatterings from a finite cylindrical shell are numerically analyzed by FEM. The simulation results show that the acoustic-scattering field in waveguide has lots of frequency-related sidelobes, while no sidelobes exist in free space at low frequencies. The simulation also indicates that the module value in waveguide can be almost 20 dB larger than that in free space at low frequency, which is caused by the ocean boundaries. We also demonstrate that when the incident wave direction is normal to the target at low frequency, the target strength will be maximum and the distribution of the acoustic-scattering field is axisymmetric about the incident waving direction. Meanwhile, the acoustic-scattering field is also related to the impedance of the seabed, and the change of the impedance makes just a little contribution to the scattering field. Finally, the influence of different target locations is analyzed, including the targets near the sea surface, seabed and the middle region of the ocean waveguide, respectively. From simulation results, it is evident that the distribution of the acoustic-scattering field at low frequency has a little difference, which is smaller than 0.5 dB with various target locations, and the change is frequency and boundary-related.

scholarly journals Acoustic radiation of a submerged cylindrical shell in low frequency

2013 ◽  
Vol 133 (1) ◽  
pp. EL26-EL32 ◽  
Author(s):  
Julien Van de Loock ◽  
Dominique Décultot ◽  
Fernand Léon ◽  
Farid Chati ◽  
Gérard Maze ◽  
...  
Keyword(s):  
Cylindrical Shell ◽  
Acoustic Radiation ◽  
Low Frequency

Investigation on Vibro-Acoustic Characteristics from Submerged Cylindrical Shell with Double Damping Layers

2013 ◽  
Vol 345 ◽  
pp. 94-98
Author(s):  
Chao Zhang ◽  
De Jiang Shang ◽  
Qi Li
Keyword(s):  
Cylindrical Shell ◽  
Low Frequency ◽  
Acoustic Characteristics ◽  
Radiated Power ◽  
Shell Models ◽  
Antiresonance Frequency ◽  
Shell Motion ◽  
Vibration And Sound Radiation ◽  
Thin Shell Theory ◽  
Large Frequency

The vibration and sound radiation from submerged cylindrical shell with double damping layers are presented. The cylindrical shell motion was described with classical thin shell theory. The double damping layers motion was described with the Navier viscoelasticity theory. For different Youngs modulus parameters of double damping layers, the sound radiated power and the radial quadratic velocity of cylindrical shell models were calculated and analyzed. The results show that the sound radiated power and radial quadratic velocity are reduced to varying degrees due to double damping layers in a large frequency domain except low frequency. The double damping layer with soft inner layer and hard outer layer can make the sound radiated peaks move to high frequency, can help to reduce the radial quadratic velocity on outer surface of damping layer, and can help to reduce the vibration of model at antiresonance frequency.

scholarly journals Prediction of Sound Radiation from Submerged Cylindrical Shell Based on Dominant Modes

2020 ◽  
Vol 10 (9) ◽  
pp. 3073 ◽  
Author(s):  
Chao Zhang ◽  
Sihui Li ◽  
Dejiang Shang ◽  
Yuyuan Han ◽  
Yuyang Shang
Keyword(s):  
Cylindrical Shell ◽  
Radiation Power ◽  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Frequency Sound ◽  
Comparison Results ◽  
Sound Radiation Efficiency ◽  
Sound Radiation Power

A sound radiation calculation method by using dominant modes is proposed to predict the sound radiation from a cylindrical shell. This method can provide an effective way to quickly predict the sound radiation of the structure by using as few displacement monitoring points as possible on the structure surface. In this paper, modal analyses of a submerged cylindrical shell are carried out by taking the vibration mode of a cylindrical shell in a vacuum, as a set of orthogonal bases. The modal sound radiation efficiency and modal contributions to sound radiation power are presented, and comparison results show that a few modes dominantly contribute to the sound radiation power at low frequencies. These modes, called dominantly radiated structural modes in this paper, are applied to predict the sound radiation power of submerged cylindrical shells by obtaining the modal participant coefficients and sound radiation efficiency of these dominant modes. Aside from the orthogonal decomposition method, a method of solving displacement modal superposition equations is proposed to extract the modal participant coefficients, because few modes contribute to the vibration displacement near the resonant frequencies. Some simulations of cylindrical shells with different boundaries are conducted, and the number of measuring points required are examined. Results show that this method, based on dominant modes, can well predict the low-frequency sound radiation power of submerged cylindrical shells. In addition, compared with the boundary element method, this method can better reduce the number of required measuring points significantly. The data of these important modes can be saved, which can help to predict the low-frequency sound radiation of the same structure faster in the future.

Bandgap analysis of cylindrical shells of generalized phononic crystals by transfer matrix method

2015 ◽  
Vol 29 (24) ◽  
pp. 1550176 ◽  
Author(s):  
Hai-Sheng Shu ◽  
Xing-Guo Wang ◽  
Ru Liu ◽  
Xiao-Gang Li ◽  
Xiao-Na Shi ◽  
...  
Keyword(s):  
Cylindrical Shell ◽  
Transfer Matrix ◽  
State Vector ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Bragg Scattering ◽  
Mechanical State ◽  
Material Parameters ◽  
Scattering Effect ◽  
Torsional Shear

Based on the concept of generalized phononic crystals (GPCs), a type of 1D cylindrical shell of generalized phononic crystals (CS-GPCs) where two kinds of homogeneous materials are arranged periodically along radial direction was proposed in this paper. On the basis of radial, torsional shear and axial shear vibrational equations of cylindrical shell, the total transfer matrix of mechanical state vector were set up respectively, and the bandgap phenomena of these three type waves were disclosed by using the method of transfer matrix eigenvalue of mechanical state vector instead of the previous localized factor analyses and Bloch theorem. The characteristics and forming mechanism of these bandgaps of CS-GPCs, together with the influences of several important structure and material parameters on them were investigated and discussed in detail. Our results showed that, similar to the plane wave bandgaps, 1D CS-GPCs can also possess radial, torsional shear and axial shear wave bandgaps within high frequency region that conforms to the Bragg scattering effect; moreover, the radial vibration of CS-GPCs can generate low frequency bandgap (the start frequency near 0 Hz), as a result of the double effects of wavefront expansion and Bragg scattering effect, wherein the wavefront effect can be the main factor and directly determine the existence of the low frequency bandgaps, while the Bragg scattering effect has obvious enhancement effect to the attenuation. Additionally, the geometrical and material parameters of units have significant influences on the wave bandgaps of CS-GPCs.

scholarly journals An Analytical Solution for the Vibration and Far-Field Sound Radiation Analysis of Finite, Semisubmerged Cylindrical Shells

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Wenjie Guo ◽  
Zhou Yang ◽  
Yueyang Han
Keyword(s):  
Cylindrical Shell ◽  
Free Surface ◽  
Present Method ◽  
Sound Pressure ◽  
Low Frequency ◽  
Sound Radiation ◽  
Far Field ◽  
Vibration Responses ◽  
Frequency Excitation ◽  
Field Sound

The vibration response and far-field sound radiation of a semisubmerged, finite cylindrical shell with low-frequency excitation are studied. The solution to this problem can be divided into two steps. The first step is to apply the wave propagation approach to determine the vibration response of the cylindrical shell. In the cylindrical coordinate system, the Flügge shell equations and Laplace equation are used to describe the cylindrical shell and surrounding fluid so that the vibration responses of the shell can be addressed analytically. The fluid free surface effect is taken into account by applying the sine series to force the velocity potential on the free surface to be zero. Furthermore, compared with the FEM (the finite element method), the present method is not only reliable but also effective. In the second step, the far-field sound radiation is solved by the Fourier transform technique and the stationary phase method in accordance with the vibration responses of the shell from the previous step. The boundary element method is applied to validate the reliability of the acoustical radiation calculation. The circumferential directivity of far-field sound pressure is discussed, and it is found that the maximum value of the sound pressure always appears directly under the structure when the driving frequencies are relatively low. Besides, in consideration of simplicity and less computation effort, the present method can be used for the rapid prediction of the vibration and far-field sound pressure of a semisubmerged cylindrical shell with low-frequency excitation.

LOW FREQUENCY VIBRATIONS OF A THIN CYLINDRICAL SHELL JOINED WITH AN ANNULAR THIN PLATE

2003 ◽  
Vol 27 (3) ◽  
pp. 183-192 ◽  
Author(s):  
Sergei B. Filippov ◽  
Eliza M. Haseganu
Keyword(s):  
Finite Element ◽  
Cylindrical Shell ◽  
Thin Plate ◽  
Low Frequency ◽  
Vibration Modes ◽  
Thin Cylindrical Shell ◽  
Asymptotic Results ◽  
Low Frequencies ◽  
Circular Beam ◽  
Good Agreement

The low frequencies and vibration modes of a thin cylindrical shell joined with an annular thin plate are obtained in this paper by means of asymptotic and numerical methods. If the annulus is wide then the low-frequency vibrations are axisymmetric. For this case a new approximate approach is developed for the evaluation of the low frequencies. If the annulus is narrow, the low-frequency vibrations are non-axisymmetric, the narrow annulus is considered as a circular beam. The equations describing the vibrations of the cylindrical shell stiffened by a circular beam are solved with the help of asymptotic techniques. The asymptotic results are in good agreement with the numerical results obtained by sweep and finite element methods.

scholarly journals Faster Calculation of the Low-Frequency Radiated Sound Power of Underwater Slender Cylindrical Shells

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Rui Tang ◽  
He Tian ◽  
Dajing Shang
Keyword(s):  
Cylindrical Shell ◽  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Power ◽  
Radiation Characteristics ◽  
Calculation Process ◽  
Radiated Sound ◽  
Stiffened Cylindrical Shells ◽  
Radiated Sound Power

Based on the fact that beam-type modes play the main role in determining the sound radiation from an underwater thin slender (length-to-radius ratio L/a>20) elastic cylindrical shell, an equivalent-beam method is proposed for calculating the low-frequency radiated sound power of underwater thin slender unstiffened and stiffened cylindrical shells. The natural bending frequencies of the cylindrical shell are calculated by analytical and numerical methods and used to solve equivalent Young’s modulus of the equivalent beam. This approach simplifies the vibration problem of the three-dimensional cylindrical shell into that of a two-dimensional beam, which can be used to simplify the calculation process of radiated sound power. Added mass is used to approximate the fluid-structure coupling, further simplifying the calculation process. Calculation examples of underwater simply supported unstiffened and stiffened cylindrical shells verify the proposed method by comparison with analytical and numerical results. Finally, the effects of the size and spacing of the stiffeners on the sound radiation characteristics of underwater free-free stiffened cylindrical shells are discussed. The proposed method can be extended to the rapid calculation of the sound radiation characteristics of underwater slender complex cylindrical shells in the low-frequency range.

Sign in / Sign up

Export Citation Format

Share Document