Fluid-elastic instability of heat exchanger tube arrays in potential cross-flow

Possibly occurring instabilities may be classified into buckling instability (divergence) and dynamical instability (flutter). Calculations revealed only instabilities of the divergence type, whenever a phase lagging angle equal to zero between the tube and fluid motion was used. The associated critical flow velocity appeared to be strongly dependent on the system geometry, thus on the number of tubes and their mutual distance. In order to account for the influence of a phase lagging effect between the motions of the tubes and the fluid sources, a modification of the model was performed by introducing a phase lag angle eta. Dynamical (flutter) instability was found to occur for specific configurations of tubes whenever a non-zero phase lagging effect was incorporated in the calculations. For a specific configuration critical velocities were compared with the results obtained by Paidoussis, dealing with a similar approach. Although agreement was found for the critical buckling velocities using eta = 0/sup o/, discrepancies occurred for the critical futter velocities, using eta = 10/sup o/ and eta = 30/sup o/ possibly due to the different way of incorporating the phase lag effect in the equations of motion. Although the present model predicts that the reduced critical velocity depends on the square root of the mass-damping parameter mδrhoD2 in a similar way as found by Connors, the actual values are larger than the experimental values from literature