Liu Yongshou

Transient response analysis of multi-span pipe conveying fluid

The method of reverberation-ray matrix proposed by Pao et al. is applied to analyze the transient response of a multi-span pipe conveying fluid. The pipe under transverse vibration is considered as Timoshenko beam conveying axial flow. In the process of analysis, fast Fourier transform is used to convert the partial differential equation into ordinary differential equation. The support points of the pipe are chosen as the elements’ nodes. The transient wave motions at each node are divided into incident and reflected wave. By virtue of continuity and balance condition, the scattering relation is established between the above wave motions. The transient response is obtained by inverse fast Fourier transform. In the examples, the natural frequencies are calculated for single- and multi-span pipe conveying fluid with different fluid velocity, and great agreement is shown with the published literature. And then the transient responses, such as deformation, velocity, shear force and bending moment are obtained for a two-span pipe conveying fluid under different fluid velocity.

The method of gray model control for the vibration of rotor system

The theory and method of the gray model control with removed residuals is used first for the study of active vibration control of a rotor system. For the symmetric rotor bearing system having a single disk, a scheme of gray model control with removed residuals about the rotor vibration is designed in this paper. The results of simulated calculation showed that this control scheme not only has good effectiveness, but also can be realized easily.

Dynamical strength and design optimization of pipe-joint system under pressure impact load

This article is focused on the dynamical strength analysis and design optimization of a pipe-joint system. A three-dimensional model of a fuel pipe-joint system is established and the strength and dynamic analysis of the system under the pressure impact load is analysed. In order to avoid dangerous forced vibrations or resonance, and to lower vibration level, the clamps’ numbers and locations are optimized. The results show that: (a) under the pressure impact load, near the T-branch pipe, clamps and elbows, the pipe system’s failure can easily occur; and (2) the numbers and locations of clamps of pipe-joint system can be optimized and the optimized pipe-joint system has better anti-vibration ability.

Two parameters affecting the dynamics characteristics of a uniform-conical assembled pipe conveying fluid

A modified Galerkin approach is employed to calculate the dynamic characteristics of a complex non-uniform fluid-conveying pipe assembled by a uniform and a conical segment. The effects of two geometric parameters (length ratio of the uniform part and conical truncation factor) on the dynamic stability are studied. Results prove that for the assembled fluid-conveying pipe 1) when fluid enters the pipe from the thinner end, the natural frequencies are higher than those when it enters from the wider end; 2) the critical flow velocity increases linearly with the increase of the uniform part ratio, while it decreases squarely with the increase of the conical truncation factor in a limited range and 3) the clamp-pined non-uniform pipe has a higher dimensionless critical velocity than the pin-clamped pipe when fluid enters from the wider end.