Development of a time delay formulation for fluidelastic instability model

Tube arrays in industrial components such as heat exchangers and steam generators are susceptible to damage due to fluidelastic instability (FEI). In the present work a new time delay formulation for the quasi-steady FEI model is derived in the frequency domain in the form of an equivalent Theodorsen function. Unsteady and quasi-static fluid forces were measured to determine the time delay formulation. The effect of Reynolds number on the static force coefficients was also investigated. The time delay function was found to be also dependent on the Reynolds number. Comparison to other time delay functions proposed in the quasi-steady and quasi-unsteady models is made. Using the new function, a stability analysis was carried out to predict the critical velocity for a range of mass-damping parameters and compared with other theoretical models. The results show a significant improvement over the constant time delay quasi-steady model and the quasi-unsteady model.