Effect Of Internal Fluid Research Articles

Effect of internal fluid and external shear flow on vortex-induced vibration response of drilling riser

This study introduces a new numerical tool for exploring the impact of various dimensionless parameters on vortex-induced vibration in risers. The tool is based on an innovative coupled model of a riser and a modified wake oscillator, which integrates the effects of internal axial flow and external cross flow. The dynamic equations are discretized using a second-order finite difference method in both time and space domains. Simulations reveal multi-modal behavior in the riser's vortex-induced vibration response, including lock-in and synchronous vibration. It is demonstrated that increasing internal flow velocity reduces response mode number and periodicity, and the riser becomes unstable when centrifugal force equals axial tension. The study also shows that higher maximum external flow velocities increase the frequency components of the riser's response and vortex shedding frequency range. A quarter-period phase difference between structural displacement and lift coefficient is observed, while lift coefficient and structural velocity remain synchronous. The lift frequency, as a function of position, jumps between neighboring sections of the riser. This tool provides a foundation for future research, with the cases explored serving as examples of its potential applications in investigating VIV phenomena.

Influence of Boundary Conditions and Internal Fluid Types on Dynamic Characteristics of a Deepwater Riser

Deepwater Steel Catenary Riser (DSCR) is the key structure of oil and gas production system in the ocean. To design an optimized DSCR system, the dynamic characteristics of the DSCR are analyzed by setting some different boundary condi-tions and internal fluid types. The main vibration mode of the DSCR is found orthogonal to both mass and stiffness according to the normalization condition of the main mode, and then the regular mode function and the jth order principal stiffness Kpj are obtained. Under different initial conditions, the transverse responses of DSCR represented by regular coordinates under arbitrary excitation are obtained. Then, a dynamic model in-duced by both axial load and transverse load is reconstructed for comparative study, and the axial load is found to have a great effect on the transverse dynamic characteristics. The effects of internal fluid and boundary conditions on the natural frequency of DSCR are also found at last.

Effects of Internal Fluid on the Dynamic Behaviors of Double Cylindrical Shells Subjected to Underwater Explosion

Abstract Fluid-filled double cylindrical shells were widely used in the marine engineering field and their blast resistance was considerably concerned. In this paper, the dynamic behaviors of fluid-filled double cylindrical shells subjected to underwater explosion were studied through a combination of experimental and numerical methods. First, a series of comparative underwater explosion tests were carried out on the scaled empty and fluid-filled double cylindrical shells. Then, more detailed numerical simulations were developed to give more results, and the model was verified by comparing with the data gathered from tests. Based on the experimental and numerical results, the effects of internal fluid on the shock wave propagation process, deformation modes, dynamic response, and energy characteristics of structures were analyzed. It is shown that the internal fluid is helpful to resist the structural deformation of outer shell and significantly decreased the axial strains of inner shell. Meanwhile, the dynamic response of the inner shell of fluid-filled shells was more violent. Besides, the internal and kinetic energy of outer shell decreased markedly. Above results would provide a reference for the protection of fluid-filled structures.

Nonlinear vibration of a pre-stressed water-filled single-walled carbon nanotube using Shell Model.

This paper is an attempt to study the nonlinear vibration of a pre-stressed single-walled carbon nanotube (SWCNT) with water-filled and simply supported ends. A new analytical formula is obtained for the nonlinear model based on the simplified Donnell’s shell theory. The effects of internal fluid on the coupling vibration of the SWCNT–water system are discussed in detail. Furthermore, the influence of the different nanotube thicknesses and radiuses on the nonlinear vibration frequencies is investigated according to the shell theory. Numerical calculations are done to show the effectiveness of the proposed schemes. The results show that the nonlinear frequency grew with the increasing nonlinear parameters (radius and thickness of nanotube). In addition, it is shown that the influence of the nonlinear parameters is greater at the lower mode in comparison with the higher mode for the same nanotube thickness and radius.

Nonlinear vibrations and multiple resonances of fluid filled arbitrary laminated circular cylindrical shells

Nonlinear forced vibrations of water-filled, laminated circular cylindrical shells are studied by using the Amabili–Reddy nonlinear higher-order shear deformation theory and energy approach in the Lagrangian description. The fluid is modeled by potential flow. It is assumed that the shell is subjected to a steady harmonic concentrated force acting in the radial direction. Pseudo arc-length continuation and collocation technique is used to carry out bifurcation analysis and to obtain nonlinear frequency–amplitude responses. Direct time integration of the equations of motion has also been performed by using Gear’s backward differentiation formula (BDF) to obtain time histories, phase space diagrams and Poincaré maps. The effect of internal fluid and lamination angle on the frequency–amplitude response in the neighborhood of the resonance frequency, traveling wave solution and internal resonances of simply supported shells are investigated. It is shown that water-filled composite shells may exhibit complex nonlinear dynamics including a rare and intricate 1:1:1:1 internal resonance.

부분 탄성지지된 유체 저장 원통셸의 자유진동

The free vibration characteristics of fluid-filled cylindrical shells on partial elastic foundations are investigated by an analytical method. The cylindrical shell is fully or partially surrounded by the elastic foundations, these are represented by the Winkler or Pasternak model. The motion of shell is represented by the first order shear deformation theory to account for rotary inertia and transverse shear strains. The steady flow of fluid is described by the classical potential flow theory. The fluid-structure interaction is considered in the analysis. The effect of internal fluid can be considered by imposing a relation between the fluid pressure and the radial displacement of the structure at the interface. To validate the present method, the numerical example is presented and compared with the available existing results.

중간 지지된 유체 유동 외팔형 원통셸의 임계유속

The critical fluid velocity of cantilevered cylindrical shells subjected to internal fluid flow is investigated in this study. The fluid-structure interaction is considered in the analysis. The cantilevered cylindrical shell is supported intermediately at an arbitrary axial position. The intermediate support is simulated by two types of artificial springs: translational and rotational spring. It is assumed that the artificial springs are placed continuously and uniformly on the middle surface of an intermediate support along the circumferential direction. The steady flow of fluid is described by the classical potential flow theory. The motion of shell is represented by the first order shear deformation theory (FSDT) to account for rotary inertia and transverse shear strains. The effect of internal fluid can be considered by imposing a relation between the fluid pressure and the radial displacement of the structure at the interface. Numerical examples are presented and compared with existing results.

DYNAMICAL BEHAVIORS OF FLUID-FILLED MULTI-WALLED CARBON NANOTUBES

This paper is concerned with the free vibration of the fluid-filled multi-walled carbon nanotubes (MWCNTs) with simply supported ends. Based on Donnell's cylindrical shell model and potential flow theory, the effects of internal fluid and the different radii on the coupling vibration of the MWCNT-fluid system are discussed in detail. The results show that the fluid has only a little influence on the natural resonant frequency (frequency of the innermost tube) and the associated amplitude ratio in MWCNTs, while it plays a significant role in the intertube resonant frequency and the associated amplitude ratio. For the natural resonant frequency, the vibrational mode is almost coaxial, i.e., the MWCNTs vibrate like a single-layer shell, however, for the intertube resonant frequency, the system shows complex noncoaxial vibration, which plays a critical role in electronic and transport properties of carbon nanotubes (CNTs). Simultaneously, the effect of the innermost radius on the frequencies of MWCNTs is also examined and the conclusions accord well with those of another paper.

유체 유동을 고려한 경사기능재료 원통셸의 연성진동

The coupled fluid-structure interaction problem is analyzed using the theoretical method to investigate the coupled vibration characteristics of functionally graded material(FGM) cylindrical shells conveying an incompressible, inviscid fluid. Material properties are assumed to vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The steady flow of fluid is described by the classical potential flow theory. The motion of shell represented by the first order shear deformation theory(FSDT) to account for rotary inertia and transverse shear strains. The effect of internal fluid can be taken into consideration by imposing a relation between the fluid pressure and the radial displacement of the structure at the interface. Numerical examples are presented and compared with exiting results.

Noncoaxial vibration of fluid-filled multi-walled carbon nanotubes

This paper is concerned with the free vibration of the fluid-filled multi-walled carbon nanotubes (MWCNTs) with simply supported ends. Based on simplified Donnell’s cylindrical shell model and potential flow theory, the effect of internal fluid on the coupling vibration of the MWCNTs-fluid system is discussed in detail. The results show that the resonant frequencies are decreased due to the effect of the fluid, and the fluid has only a little influence on the associated amplitude ratio in MWCNTs corresponding to the natural resonant frequency (frequency of the innermost tube), while plays a significant role in the associated amplitude ratios corresponding to the intertube resonant frequency. For the natural resonant frequency, the vibration mode is coaxial. However, for the intertube resonant frequency, the system shows complex noncoaxial vibration, which plays a critical role in electronic and transport properties of carbon nanotubes (CNTs).

3D free vibration analysis of a functionally graded piezoelectric hollow cylinder filled with compressible fluid

The free vibration of an arbitrarily thick orthotropic piezoelectric hollow cylinder with a functionally graded property along the thickness direction and filled with a non-viscous compressible fluid medium is investigated. The analysis is directly based on the three-dimensional exact equations of piezoelasticity using the so-called state space formulations. The original functionally graded shell is approximated by a laminate model, of which the solution will gradually approach the exact one when the number of layers increases. The effect of internal fluid can be taken into consideration by imposing a relation between the fluid pressure and the radial displacement at the interface. Analytical frequency equations are derived for different electrical boundary conditions at two cylindrical surfaces. As particular cases, free vibration of multi-layered piezoelectric hollow cylinder and wave propagation in infinite homogeneous cylinder are studied. Numerical comparison with available results is made and dispersion curves predicted from the present three-dimensional analysis are given. Numerical examples are further performed to investigate the effects of various parameters on the natural frequencies.

Nonlinear Vibrations and Multiple Resonances of Fluid-Filled, Circular Shells, Part 1: Equations of Motion and Numerical Results

The response-frequency relationship in the vicinity of a resonant frequency, the occurrence of travelling wave response and the presence of internal resonances are investigated for simply supported, circular cylindrical shells. Donnell’s nonlinear shallow-shell theory is used. The boundary conditions on radial displacement and the continuity of circumferential displacement are exactly satisfied. The problem is reduced to a system of four ordinary differential equations by means of the Galerkin method. The radial deflection of the shell is expanded by using a basis of four linear modes. The effect of internal fluid is also investigated. The equations of motion are studied by using a code based on the Collocation Method. The present model is validated by comparison of some results with others available. A water-filled shell presenting the phenomenon of 1:1:1:2 internal resonances is investigated for the first time; it shows intricate and interesting dynamics. [S0739-3717(00)01204-6]

A Solution of Free Lateral Vibrations of a Pipe String Designed for Mining Manganese Nodules

A mathematical description of free lateral vibrations of a pipe string, which is designed for mining manganese nodules in the deep ocean, leads to an eigenvalue problem containing a small parameter multiplying the highest derivative of its differential operator. This problem is analyzed by an asymptotic theory, de Groen's method, and natural frequencies and modes are evaluated. furthermore, The effects of internal fluid on the motion of the pipe string are investigated. It is shown that the algorithm developed is an effective one, providing highly accurate solutions even if only the zero approximation is used.

Response of Anisotropic Cylindrical Shells due to Local Acoustic Pressure

The dynamic equation of motion for anisotropic shells is first formulated with the effects of internal fluid, internal pressure, and viscous damping taken into account. For practical purposes, the system is reduced to a Donnell-type equation with the radial displacement as the single dependent variable. The response of the shell due to local acoustic pressure of discrete frequency is then analyzed by using the normal-mode solution. The calculation is facilitated by first plotting the free vibration spectra of the cylinder. Based on the spectra, the resonant modes for a given forcing frequency are isolated and the response can be accurately calculated by considering only the components of the pressure identical to those modes. Since the Fourier-series expansion for a local load usually involves thousands of modes, the process proposed here greatly simplifies the response calculation. Numerical results obtained herein are presented in charts.