Active Control Of Vibrational Power Flow In A Fluid-Filled Shell

The fluid-filled pipelines system is widely used in the power, petroleum, petrochemical industry various industrial installations and in vessels, aircraft and so on. The liquid pressure pulsation and vibration in the wall of the structure can cause vibration and noise pollution, it worse is the pipe system or machinery was damaged. There are many vibration waves in fluid-filled pipelines, they will be coupled each other, the vibration mechanism is very complicated. So it needs to reveal the fluid-filled pipe vibration characteristics, understand liquid pressure pulsation and vibration production and dissemination mechanism in the pipe wall systems to ensure reliability in the design stage and forecast the vibration-sound energy flow and achieve the purpose to control the pipeline vibration. The loss caused by the Pipeline vibration and noise is enormous. A Canadian expert estimates that the loss caused by the Pipeline vibration was about 100 million dollars in advanced industrial countries. Therefore, the study of the input power flow in the cylindrical shell, propagation power flow as well as sound radiation mechanism has the widespread project significance and the economical significance to control the noise dissemination link from noise source to radiation sound field, thus to reduce the pipeline noise to reaches higher authorities in the whole remarkably, to enhance the pipeline security.In this paper we use periodic structure theory and vibration power flow method, investigate the active control method of input power flow of the fluid-loaded cylindrical shells. By using mobility function, the vibration response of the cylindrical shell stimulated by the primary and secondary forces is studies. The total input power flow is expressed in an equation of Hermitian quadratic form as the objective function. The optimum set of secondary force is obtained and several important parameters which influence the control effect are analyzed.The vibration and noise in the structure will propagate to a far location by means of waves, the essence of which is the propagation of power flow, and the radiated sound power is equal to the residual of loss energy caused by damping deducted from the input power flow. The actual length of the pipeline is bounded; in this paper we use an unbounded structure to replace it. The basis is the response of unbounded structure is approximately equal to the average of that of bounded structure at low frequency, and the responses of two kinds of structures drive to coincidence with the increasing of frequency. In the statistical energy analysis, calculating the modal density, the internal coupling loss factor and the input energy flow by a driving force, generally applied to this conclusion.