Case Study on Beam-mode Flow Induced Vibration against Random Force Fluctuation due to Turbulent Flow at Bend

摘要

The flow induced vibration is the important phenomena when designing piping system and rigorous analysis method without excessive conservatism is highly demanded. Recently guidelines published by Energy Institute is often applied in design phase of piping system to consider the vibration risk in design; however, the safety factor for the method is not fully investigated, especially, for example, the effect of the piping layout, flexibility factor of bend, extrapolation to large bore headers, etc .... In previous paper, Authors investigated the forcing function due to turbulence flow at the bend by using LES-CFD analysis and quantified the random force fluctuation at the 90 degrees miter bend and two smooth bends and showed that random vibration analysis with these forcing functions can be used to assess the risk of piping vibration. In this paper, the authors conducted a series of random vibration analysis on the beam mode vibration of typical piping systems. The design variable, such as piping diameter, diameter to thickness ratio, number of flow direction change in each span, and support span were varied as a parameter of the design and evaluated the magnitude of stress and vibration level. The results were compared with the LOF score provided by Energy Institute Guidelines and clarified the difference in design margin of the methods. In conclusions, provides some guidance to reasonably apply the screening method in the design phase of the piping system.