Application of Arbitrary Lagrange Euler Formulations to Flow-Induced Vibration Problems

Most classical fluid force identification methods rely on mechanical structure response measurements associated with convenient data processes providing turbulent and fluid-elastic forces responsible for possible vibrations and damage [2][7]. These techniques provide good results; however they often involve high costs as they rely on specific modellings fitted with experimental data. Owing to recent improvements in Computational Fluid Dynamics, numerical simulation of flow-induced structure vibration problems is now practicable for industrial purposes. As far as flow structure interactions are concerned, the main difficulty consists in estimating numerically fluid-elastic forces acting on mechanical components submitted to turbulent flows. The point is to take into account both fluid effects on structure motion and conversely dynamic motion effects on local flow patterns. This requires a code coupling to solve fluid and structure problems in the same time. This ability is out of limit of most classical fluid dynamics codes. That is the reason why recently an improved numerical approach has been developed and applied to the fully numerical prediction of a flexible tube dynamic response belonging to a fixed tube bundle submitted to cross flows. The methodology consists in simulating at the same time thermo-hydraulics and mechanics problems by using an Arbitrary Lagrange Euler (ALE) formulation for the fluid computation. Numerical results turn out to be consistent with available experimental data and calculations tend to show that it is now possible to simulate numerically tube bundle vibrations in presence of cross flows. Thus a new possible application for ALE methods is the prediction of flow-induced vibration problems. The full computational process is described in the first section. Classical and improved ALE formulations are presented in the second part. Main numerical results are compared to available experimental data in section 3. Code performances are pointed out in terms of mesh generation process and code coupling method.