Bending Vibration Suppression of a Flexible Multispan Shaft Using Smart Spring Support

Because the flexible multispan shaft in large machines often rotates at supercritical speed, it is desirable to find ways to suppress the resulting bending vibration. In this paper, a novel type of support structure is proposed and investigated, which can suppress the bending vibration using dry friction. This approach is called Smart Spring support (SMSS). A dynamic model for the multispan shaft with SMSS is developed. The relationship between the vibration suppression effect and the control parameters of the SMSS is obtained through a numerical example involving a helicopter tail drive shaft. A structure of the SMSS is designed and examined with a rotor test. The results demonstrate that the SMSS has a significant effect on bending vibration suppression of flexible multispan shafts. The vibration-reduction ratio of the peak amplitude reaches 57.2% in the numerical example and 45.2% in the rotor test.

The Calculation of Ship Wave in Shallow Water by Finite Difference Method

Based on the shallow water wave potential flow theory and slender ship assumption, the mathematical model is established for calculating wave caused by ship moving at supercritical speed. The wave pattern caused by ship moving at supercritical speed in shallow water was calculated by using the finite difference method. The effects of channel wall were analyzed. The computed results were compared with the ones calculated by Fourier integral transform method and experiment. A good agreement exists between the calculated with experimental results. The mathematical model and the calculation method were validated.

Research on Wash Wave in Shallow Water Caused by Ship Moving at High Speed

Based on the theory of shallow-water wave, the theoretical model was established for calculating wash wave caused by ship moving at subcritical and supercritical speed. Wave elevation and pressure variation were obtained by numerical simulation, and their features were analyzed. A measuring system of wash wave and pressure variation was developed, and wave elevation and pressure variation induced by a towed ship model were measured. A good agreement existed between the calculated with experimental results.

Numerical Analysis and Simulation of Vibration Characteristics of the Rotation Shaft with Mechanical Seal System

This paper make the rigid support Jeffcott shaft-mechanical seal system as the research object. Firstly, it establishes the equivalent stiffness matrix and damping matrix of the rotation shaft with mechanical seal in the fixed-coordinate system, then derives the motion equation of the shaft with mechanical seal and applies the numerical simulation method to analyze and gain the vibration characteristics of the rotation shaft with mechanical seal system. Numerical simulation results show that: when the rotation shaft works at the speed of the subcritical speed, the trajectory of centre will change with the speed of the shaft. When the shaft works at the speed of the second supercritical speed, the trajectory of centre will be a limit circle. When the shaft works at the speed of the subcritical speed, the vibration response appear 1X, 2X, 3X and so on component of the vibration, and when Ω is 1/2, 1/3 and so on, 2X, 3X and so on component of vibration is biggest; when the shaft works at the speed of the second supercritical speed, 2X and 2X above component of the vibration is very small, even to zero, and then the trajectory of the centre is a limit circle. Whenhminis different, amplitude-frequency diagram of the X direction of the rotation shaft is different. Whenhminis bigger ,1X, 2X, 3X component of the vibration is bigger.

Three-dimensional nonlinear solitary waves in shallow water generated by an advancing disturbance

The nonlinear long waves generated by a disturbance moving at subcritical, critical and supercritical speed in unbounded shallow water are investigated. The problem is formulated by a new modified generalized Boussinesq equation and solved numerically by an implicit finite-difference algorithm. Three-dimensional upstream solitary waves with significant amplitude are generated with a periodicity by a pressure distribution or slender strut advancing on the free surface. The crestlines of these solitons are almost perfect parabolas with decreasing curvature with respect to time. Behind the disturbance, a complicated, divergent Kelvin-like wave pattern is formed. It is found that, unlike the wave breaking phenomena in a narrow channel at Fh [ges ] 1.2, the three- dimensional upstream solitons form several parabolic water humps and are blocked ahead of the disturbance at supercritical speed in an unbounded domain for large time.