Large-eddy simulations of the vortex-induced vibration of a low mass ratio two-degree-of-freedom circular cylinder at subcritical Reynolds numbers

• Published in: Computers & fluids 2018-09, Vol.173, p.118-132
• Main Authors: Pastrana, D., Cajas, J.C., Lehmkuhl, O., Rodríguez, I., Houzeaux, G.
• Format: Article
• Language: English
• Subjects: Amplitudes; Circular cylinders; Computational fluid dynamics; Computer simulation; Cross flow; Degrees of freedom; Eddies; Eddy viscosity; Enginyeria mecànica; Finite element method; Flow equations; Fluid flow; Fluid-structure interaction; Fluid-structure interactions; Incompressible flow; Large eddy simulation; Low mass ratio; Mathematical analysis; Mathematical models; Mecànica de fluids; Remolins (Mecànica de fluids); Reynolds number; Scale models; Simulació per ordinador; Simulation; Simulation methods; Turbulent flow; Two-degree-of-freedom system; Vibration analysis; Vortex induced vibration; Vortex shedding; Vortex-induced vibrations; Vortex-motion; Vortices; Vorticitat; Àrees temàtiques de la UPC
• ISSN: 0045-7930; 1879-0747
• DOI: 10.1016/j.compfluid.2018.03.016

•High-fidelity (LES) study of a 2dof VIV of a low mass ratio circular cylinder is presented.•A low-dissipative spatial and temporal discretization has been used.•Numerical results are extensibly compared with available experimental and numerical data.•Significant improvements respect to previous high-fidelity numerical simulations are done.•Transition between SU branch and L branch is explored. The vortex induced vibration phenomenon of a low mass ratio (m*=2.6) two-degree-of-freedom circular cylinder at subcritical Reynolds numbers (Re=3900, 5300, 11,000) has been investigated by means of large-eddy simulations. A low-dissipative spatial and time discretisation finite element schemes have been implemented and combined with the Wall-Adapting Local-Eddy viscosity (WALE) subgrid-scale model to solve the filtered incompressible flow equations. Several values of the reduced velocity in the range 3 ⩽ U* ⩽ 12 have been considered. The numerical results are extensively compared with available experimental and numerical data. Particular interest has been placed in the region of maximum cross-flow amplitudes, the super-upper branch, where previous high-fidelity numerical simulations have underestimated the peak amplitudes compared with experimental results. The transition between the super-upper and lower branches is also shown and described. The numerical simulations successfully reproduce the three-branch response maximum oscillation amplitudes and associated vortex formation modes. The 2T vortex formation mode, i.e. two triplets of vortices per oscillation period, has been observed to occur in the super-upper branch, for the three different values of the Reynolds number investigated. These results contradict the claim made in previous works [27] that the vortex formation mode in the super-upper branch is Reynolds number dependent. Beats are observed to appear prior the transition from the super-upper to the lower branch. It is argued that they may be related with the coherence and strength of the third vortex shed at the shoulder of the cylinder each half-cycle, which is finally suppressed in the transition to the lower branch.