FSI—vibrations of immersed cylinders. Simulations with the engineering open-source code TrioCFD. Test cases and experimental comparisons

Abstract

In this paper, we assess the capabilities of the Arbitrary Lagrangian–Eulerian (ALE) method implemented in the open-source code TrioCFD to tackle down two fluid–structure interaction problems involving moving boundaries. To test the code, we first consider the bi-dimensional case of two coaxial cylinders moving in a viscous fluid. We show that the two fluid forces acting on the cylinders are in phase opposition, with amplitude and phase that only depend on the Stokes number, the dimensionless separation distance and the Keulegan–Carpenter number. Throughout a detailed parametric study, we show that the self (resp. cross) added mass and damping coefficients decrease (resp. increase) with the Stokes number and the separation distance. Our numerical results are in perfect agreement with the theoretical predictions of the literature, thereby validating the robustness of the ALE method implemented in TrioCFD. Then, we challenge the code by considering the case of a vibrating cylinder located in the central position of a square tube bundle. In parallel to the numerical investigations, we also present a new experimental setup for the measurement of the added coefficient, using the direct method introduced by Tanaka. The numerical predictions for the self-added coefficients are shown to be in very good agreement with a theoretical estimation used as a reference by engineers. A good agreement with the experimental results is also obtained for moderate and large Stokes numbers, whereas an important deviation due to parasitic frequencies in the experimental setup appears for low Stokes number. Still, this study clearly confirms that the ALE method implemented in TrioCFD is particularly efficient in solving fluid–structure interaction problems. As an open-source code, and given its ease of use and its flexibility, we believe that TrioCFD is thus perfectly adapted to engineers who need simple numerical tools to tackle down complex industrial problems.

Keywords

• TrioCFD
• Vibration
• Fluid–structure interaction
• Added mass
• Added damping
• Stokes number
• ALE method
• TrioCFD