CFD Evaluation and Experimental Comparison on Flow around Fixed Multi-column Configurations

The flow-induced motion (FIM) of platforms is an important issue to be investigated and require further investigation of captive models. On this matter, it is worth examining the vortex detachments, the source for the oscillatory lift, drag force and the interference of the upstream cylinders wake on the downstream ones. CFD calculations of the flow around a stationary array of one, three and four cylinders with low aspect-ratio, AR=1.5, are going to be presented in this paper. Three different shapes of the cylinder's section will be tested: circular, square and diamond. For the multi-cylinder cases, the spacing between center to center of each column was S/L = 4 where L is the characteristic length of the cylinder. The Reynolds number tested was 160,000. The calculations were performed with the flow solver StarCCM+; it solves the multi-phase unsteady incompressible URANS equations. For this work, simulations were carried out with Improved Delayed Detached Eddy Simulation, IDDES, turbulence model, which estimate the small turbulence scales with RANS turbulence model and the large scales with LES. For the VoF an interface-capturing approach was used. For the multi-column arrays, no regular vortex shedding pattern was observed. The cases with three and four columns showed a similar behavior: good agreement for the circular and square cases and a significant deviation for the diamond cases, which need to be further investigated. This work is a result of a collaborative program between the University of São Paulo and the University of Tokyo and supported by JASNAOE.