An analytical model was developed for the prediction of fluidelastic instability in cross flow multi-span heat exchanger tube arrays. The model is based on concepts developed by Lever and Weaver, as well as Yetisir and Weaver, but is modified and extended to include other important factors. Rather than the nonlinear function previously used, a linear area perturbation decay function is introduced to account for the decay of disturbances away from an oscillating tube. Thus, an analytical solution can be obtained. Flexible tubes directly two rows upstream and downstream of a central tube, neglected in the earlier work, are included in the present model. Improved agreement with experimental data is obtained for parallel triangular tube arrays. In contrast, little improvement is achieved for the other tube patterns due to the reduced influence of the upstream tube wake. The velocity distribution and mode shape along the tube span are also introduced into the model. This is made possible because of the explicit stability equation. Therefore, the present model can be used to calculate the fluidelastic instability for the multi-span tube arrays. Comparison between theory and experimental data shows good agreement.

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