Prediction of flow-induced excitation in a pipe conveying fluid

Abstract

Experimentally it is evident that the nature of the flow-induced excitation in a pipe conveying fluid is a broadband frequency excitation. It is also observed that the amplitude of excitation decreases with increase in frequency. However, there is no method to estimate such forces. The measurement of excitation force all along the length of a pipe using the pressure transducers may be difficult or perhaps impossible. Another possibility is to measure the structural responses using vibration transducers all along the pipe length and then estimate the flow-induced excitation forces (both amplitude and phase) using a finite element (FE) model of the pipe. However, the measured degree of freedoms (dofs) are always much smaller than the dofs in FE model, hence a method has been developed that uses non-linear optimization method involving the limited measured responses together with FE model to predict the excitation forces (both amplitude and phase) acting all along the pipe conveying fluid. The predicted excitation forces can then be used to perform safety related study by assessing the pipe responses at any location whether accessible or not. The theory of the proposed method and its validation has been presented in the paper through a long straight pipe conveying fluid. Typical applications of the proposed method are also discussed.