Analysis Of Fluid-Filled Pipe Dynamic Modeling And Vibration Characteristic

The fluid-filled pipes are widely applied in industrial engineering and our daily life, and have great importance to national economy. But, vibration and noise of the pipe may damage the machines and equipments, and bring inconvenience to people's life. This paper concentrates on the vibration characteristic study taking the Fluid-Structure Interaction (FSI) into account. It is carried out the more specifically work in four aspects:1. The fluid-structure coupling vibration equation of the pipe is established by following the Hamilton principle and using finite element method. Based on theory of finite element analysis of straight pipe and continuity equation and momentum equation, elbow pipe modal is transferred into short straight pipes modal which the axial, lateral, torsion vibration are taken into account. Calculate the modal frequency and shape of a elbow pipe. The results indicate that the modal frequency of the pipe will decrease while fluid speed increase and pressure decrease.2. Equation of fluid transmission dynamics is established to get wave velocity. Compared to circuit components, the relationship between pressure and flow rate is obtained by establishing the basic equations of fluid pressure transmission. Based on the basic equations of fluid pressure transmission, the characteristics of the fluid pressure transmission is obtained, which provide a theoretical basis to reduce fluid pressure pulse. From example calculation, conclusion that two force direction at ends of a straight pipe should be opposite. Specific measures include: straight pipe length between two adjacent elbow angles has better be multiple of wave length, installing capacity in the pipe and so on.3. From the finite element equation, the force and displacement response can be solved. From which, power flow and energy distribution of the pipeline will be obtained. Then, pipeline vibration degree will be assessed from energy in quantity. For the purpose to reduce the pipeline vibration, assess the vibration by the energy distribution of average length. Compare results with that concluded by the displacement, and come to the conclusion that assessing the vibration by energy is more precise than by displacement. Besides, The energy flow calculation equations of the axial and transversal vibration. The cross-power-spectral method is derived based on the finite difference theory and the beam modal.4. Air-filled and water-filled pipes in free state and supported by simply support are calculated by using both beam model and shell model. Three natural frequencies and modal shapes are got. The results are basically same as the experimental results, that indicates beam model is accurate. And fluid-structure interaction decreases the natural frequencies but have less effects on modal shapes. The results of modal tests have also proved that distance between two supports does not affect accuracy of beam model. The energy flow experiment shows that low frequencies vibration have more effect on pipe.