Abstract
Prevention of piping vibrations during design stage has attracted attention recent years. Though the piping vibration occurs due to various mechanisms, the vibration due to fluid turbulence is one of a major topic discussed. The pressure fluctuation due to fluid turbulence occurs around flow discontinuities such as branches, elbows, flow expansions and valves, and the fluctuation can cause the piping vibration and both shell mode and beam mode vibration can occur. Guideline published by Energy Institute UK[1] (EI-AVIFF) shows a method to check the possibility of piping vibration due to flow induced turbulence and it gives some information on recommended piping span. The method is quite useful for screening purpose to select the piping system with potential vibration risks. However, it is known that the guideline is based on very conservative assumptions, as 90-degree miter bend, and it results in overdesign of piping systems, so more detailed vibration assessment approach succeeding the screening is demanded.
In this paper, the method of detailed beam-mode piping vibration assessment using finite element dynamic structural analysis and Large Eddy Simulation (LES) based CFD are discussed. As an example, LES based CFD analyses were conducted on 90 degrees single miter bend, long and short elbow. The resultant pressure fluctuations are compared to past published report and good agreement was confirmed. The CFD results were reorganized and piping dynamic analysis were conducted. Based on these analysis results, the detailed piping vibration risk assessment method using CFD and dynamic structural analysis are proposed.
