Abstract:

The complex behavior of an unsteady flow around two circular cylinders in tandem is of interest for many civil engineering applications across a wide range of aerospace, mechanical and marine applications. The present paper analyses Vortex-Induced Vibration (VIV) for flow around two circular cylinders. VIV of a circular cylinder has been shown to have the potential to generate clean energy. The efficiency of VIV power obtained from a downstream elastically mounted cylinder in the wake of an upstream cylinder is compared for different arrangements of cylinders. The upstream cylinder is stationary while the downstream one is mounted elastically with one degree of freedom normal to the mean flow direction. Scale- Adaptive Simulation (SAS) and Shear Stress Transport (SST) CFD models are utilized to analyze the validity of the SAS turbulence model. For this purpose, the spacing between the cylinders was varied whilst the Reynolds number is kept constant. The numerical simulation is validated against the mean pressure coefficients, lift and drag coefficients and Strouhal number experimentally measured on cylinders. The results indicate that both turbulence models predict the flow characteristics around the cylinders with reasonable precision; however, the predictions from SAS were more accurate compared to SST. Based on this comparison a SAS model was chosen as a tool to analyze the VIV power which can be captured by the downstream cylinder. To obtain the optimum efficiency of VIV power, the location of downstream cylinder has been altered in the wake of upstream one. The findings reveal that the arrangement of cylinders can significantly change the efficiency of VIV power. Cylinders offset from one another show a higher efficiency compared to aligned cylinders.