High Frequency Statistical Energy Analysis Applied to Fluid Filled Pipe Systems

In pipe systems, carrying gas with high velocities, broadband turbulent pulsations can be generated causing strong vibrations and fatigue failure, called Acoustic Fatigue. This occurs at valves with high pressure differences (i.e. chokes), relief valves and obstructions in the flow, such as sharp bends and T-branches. Characteristic for the turbulent sources is the strong and broadband excitation caused by turbulent flow, complex acoustic response and vibrations. The traditional approach to calculate the response per resonance frequency. This brute force method is too (computational) time consuming and perhaps even not feasible. As an alternative probabilistic methods can be used. The Statistical Energy Analysis (SEA) is such a method, which only assumes statistical knowledge. The method is particularly suited for modeling multi-modal structural-acoustic systems, excited at frequencies well above their fundamental natural frequencies. To validate the SEA approach for fluid filled pipe systems, in this paper first a well-defined laboratory setup is presented: SEA results, structural-acoustic coupled FEM results and experimental results are compared. After that the SEA approach is used to assess the mechanic integrity of a complex subsea installation, from which also a very elaborate structural-acoustic FE model is available.