Fsi Analysis of Liquid-Filled Pipes

Abstract

Most reported work on transient fluid/structure interaction (FSI) in liquid-filled pipes has been carried out in the time domain. When needed, information in the frequency domain (e.g., frequency responses) has been deduced by discrete Fourier transforms. In this paper, the analysis is undertaken directly in the frequency domain and has the advantage of enabling (linear) dispersive terms to be included in a fully coupled manner. In principle, time-domain results (e.g., pressure histories) can be obtained by numerical inverse Laplace transforms. In both domains, the mathematical model has one pair of equations for each mode of wave propagation—e.g., pressure waves in the liquid, flexural waves in the pipe. Axial FSI coupling exists in the equations and also in boundary conditions. The development used herein highlights common features between analysis in the frequency domain and analysis by the method of characteristics (MOC) in the time domain. A general formulation, not restricted to pipe systems, is presented. The method is validated by comparison with an alternative exact analytical solution, with results obtained by discrete Fourier transform from an MOC analysis and by comparison with measured data from a laboratory apparatus.