Non Linear Vibrations of Loosely Supported Tubes Excited by Fluidelastic and Turbulence Forces

Abstract

For predictive analysis of flow-induced vibration and wear of heat exchanger tubes, non linear computation of tube dynamics may be performed using adequate modelisation of the fluid forces. This paper presents computations of the response of loosely supported tube to fluidelastic forces and turbulence. Computations are performed using the time-domain dynamic equations, which are projected on the modal basis of the tube (Axisa et al, 1988, de Langre et al, 1992). The fluidelastic forces are modeled as reduced velocity dependent fluid-stiffness and fluid-damping coefficients obtained with the Price and Païdoussis model. Random turbulence forces are estimated as function of flow rate from the experimentally measured power spectral density function (Axisa et al, 1990). A corrective methodology is proposed to account for the frequency dependence associated with fluid-stiffness and fluid-damping coefficients. Good agreement is obtained with computations using direct time dependent fluidelastic forces of the model.