Vibroacoustical analysis of flow in pipe system.

The present study is devoted to fluid-structure interaction (FSI) within a straight pipe. A non dimensional transfer matrix (dimension 4X4) is defined and links state vectors in two cross-sections of pipe. That matrix formulation, in the frequency domain, has been used as basis for a four transducers intensimetry technique. That method allows for a more accurate determination of a state vector in a given cross section of a straight pipe. All calculations have been done with a control of the conditioning of matrices. A new method is proposed : that one uses pressure, flow velocity, axial displacement and axial strain as variables. The choice leads to a proposal of a non intrusive experimental procedure, which can be useful for the experimental determination of hydroacoustic transfer matrices of complex part of an hydraulic circuit in the low frequencies range. So drilling holes in pipes to insert pressure transducers, for example, will, in many situations, be undesirable or even impossible.