Dynamic Modeling and Vibration Characteristics Analysis of Submerged Stiffened Combined Shells

The influence of roof on the natural frequencies and the modes of fixed roof, ground supported, liquid storage tanks is presented in this paper. Attention is given to partially filled tanks with the same heights of 12.19 m and the aspect ratios ( H / R ) of 2, 1.52, and 1.33. The bottom of tanks is considered to be anchored to the foundation. The effect of the roof, along with the liquid height, on dynamic properties is investigated. For this purpose, each tank is modeled in 4 liquid levels, equal to 1.80, 4.80, 8.50, and 10.90 m and in two various roof conditions: with roof (WR) and open top (OT). The finite element package ANSYS is used to model the tank–liquid systems. Tank roof and wall are meshed by shell elements and the liquid is modeled using fluid finite elements. The fluid–structure interaction is taken into account by coupling the nodes at the interface of the fluid and the shell in the radial direction. Results of ambient vibration tests are used to verify the numerical procedure in which good agreement is observed between the numerical and the experimental modal parameters. It is found that the influence of roof on natural frequencies of axial and vertical modes is negligible whereas its effect on the natural frequencies of circumferential modes is significant. It is also concluded that at low liquid levels, equal to 1.80 and 4.80 m, the tank roof does affect the axial modes of the tallest and medium height tanks while, at all of the considered liquid heights and aspect ratios, the tank roof affects the circumferential mode shapes; this confirms the idea that the roof does restrain the tank top against radial deformations.

Influence of roof on dynamic characteristics of dome roof tanks partially filled with liquid

This article investigates the free vibration response of a conical system supported by an intermediate solid ring. The ingredients of the shell are considered a polymer reinforced with graphene platelets (GPLs). The distribution of GPLs is assumed to be uniform, and their orientation is considered random in each layer of the composite. The variation of GPL weight fraction within layers is based on the functionally graded patterns. Effective material properties are calculated utilizing the Halpin–Tsai homogenization procedure. The fundamental formulation of the shell is founded by the first-order shear deformation theory and Donnell’s kinematic assumptions. The motion equations and associated boundary and compatibility conditions are derived by Hamilton’s principle. Solving the governing equations due to the existence of a solid frequency control ring is not possible using conventional numerical methods. For this reason, a new type of GDQ method is applied, which is a combination of this technique with a finite element procedure (GDQE). By combining this method with the method of trigonometric expansion (TE) analysis, the equations of motion of the structure are solved. After illustrating the validation studies, parametric examples are given to investigate the effect of material properties, boundary conditions, and ring position on the shell frequencies. 

TE-GDQE implementation to investigate the vibration of FG composite conical shells considering a frequency controller solid ring

The linear three-dimensional piezoelasticity theory in conjunction with the versatile transfer matrix approach is employed to investigate the steady-state nonaxisymmetric fluid–structure-coupled vibrations of an arbitrarily thick bilaminate simply supported hollow cylinder of finite length, composed of an inner layer of orthotropic functionally graded material perfectly bonded to an outer layer of radially/axially/circumferentially polarized functionally graded piezoceramic material. The cylinder is filled with a compressible nonviscous fluid and may be subjected to arbitrary time-harmonic on-surface mechanical drives. The analytical results are illustrated with numerical examples in which water-filled homogeneous PZT4–steel composite cylinders are driven by harmonic external concentrated or distributed radial surface loads. When the outer piezoelectric layer is operating in the receiving (sensing) mode, the frequency spectrums of the induced voltage, stress components, and on-axis acoustic pressure are c...

Vibroacoustic response and active control of a fluid-filled functionally graded piezoelectric material composite cylinder

Abstract This paper presents an analysis of low-frequency liquid vibrations in rigid partially filled containers with baffles. The liquid is supposed to be an ideal and incompressible one and its flow is irrotational. A compound shell of revolution is considered as the container model. For evaluating the velocity potential the system of singular boundary integral equations has been obtained. The single-domain and multi-domain reduced boundary element methods have been used for its numerical solution. The numerical simulation is performed to validate the proposed method and to estimate the sloshing frequencies and modes of fluid-filled cylindrical shells with baffles in the forms of circular plates and truncated cones. Both axisymmetric and non-axisymmetric modes of liquid vibrations in baffled and un-baffled tanks have been considered. The proposed method makes it possible to determine a suitable place with a proper height for installing baffles in tanks by using the numerical experiment.

/pdf/low-frequency-sloshing-analysis-of-cylindrical-containers-1l7u6gcste.pdf

Low Frequency Sloshing Analysis of Cylindrical Containers with Flat and Conical Baffles

This paper describes the method of determining the normal modes of vibrations and natural frequencies of elastic shells of revolution with an arbitrary meridian, partially filled with a fluid. The modes of vibration of the shells with fluids are determined as a linear combination of the natural modes of vibration in vacuum. The solution of the problem of hydroelastic vibrations has been obtained using the methods of the boundary element (BEM) and the finite element (FEM). Numerical investigations of vibrations of hemi-spherical shells conveying fluid have been conducted and analyzed. Illustrative examples are provided to demonstrate the accuracy and efficiency of the developed numerical procedure.

Free vibrations of shells of revolution filled with a fluid

The coupled problem of free and forced vibration of shells of revolution interacting with the liquid is under consideration. The problem was reduced to singular integral equations. The main objective of this paper is to present a detailed study of free and forced vibrations of a shell of revolution with an arbitrary meridian. For solving the boundary value problem of determining the fluid pressure on the shell, the boundary element method (BEM) is used. This method substantially reduces the computer time for the analysis and reveals new qualitative possibilities in modeling the dynamic behavior of shells. Numerical investigations of natural frequencies and mode shapes of the cylindrical tank with the incompressible fluid have been carried out. The behavior of structures subjected to a dynamic loading and interacting with the fluid is investigated.

/pdf/free-and-forced-vibrations-of-the-shells-of-revolution-2a5xyui76q.pdf

E. Yeseleva

Papers

Free vibrations of shells of revolution filled with a fluid

Free and forced vibrations of the shells of revolution interacting with the liquid