CFD Investigation of Flow Interactions of Four Fixed Columns With Free Ends in Square Configuration
- Jiawei He (Shanghai Jiao Tong University) | Weiwen Zhao (Shanghai Jiao Tong University) | Decheng Wan (Shanghai Jiao Tong University)
- Document ID
- International Society of Offshore and Polar Engineers
- The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan
- Publication Date
- Document Type
- Conference Paper
- 2018. International Society of Offshore and Polar Engineers
- Flow around fixed columns, naoe-FOAM-SJTU solver, CFD, SST-DDES
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- 26 since 2007
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Numerical simulations are carried out by the in-house naoe-FOAM-SJTU solver based on the OpenFOAM framework. Delayed Detached-Eddy Simulation (DDES) method based on the Shear-Stress Transport (SST) model is used to simulate the large separated flow in high Reynolds numbers, Re = 50,000. CFD simulations are carried out for three different column geometries, namely circular, square and diamond. To further illustrate the vortex shedding characteristics of interaction between wakes in the array of cylinders, the results of mean drag and RMS lift force coefficients are analyzed for each column. The mean drag and RMS lift force coefficients of each column are in generally good agreement with experimental results. The instantaneous vortex shedding structures of three different column geometries are also presented. A tip vortex is observed around the free end of upstream columns, while it is not obvious around the free end of downstream columns. Results show that the effect of column section geometries to the mean drag force coefficients and wake flows of upstream columns is very significant.
A floating body in a flow experiences periodic motion and this motion is called vortex-induced motion (VIM). VIM is induced by vortex associated with the separation of boundary layer at the body surface. The analysis of vortex-induced motions (VIM) is of great importance during the design process of a floating offshore platform since the unsteady VIM phenomenon has significant influences on the fatigue life of mooring and riser systems. Most of the semi-submersibles and TLP offshore platforms consist of four columns. Investigating the flow interaction between each column can reveal some physics behind the VIM. What's more, the flow field around the multi-column platforms is more complex than the single cylindrical structures due to the mutual interfere between cylinders which generates complex wake-structure interaction process in vortex-shedding. Hence, a pre-research work is conducted here to lay a foundation for the future study of semi-submersibles offshore platform's VIM phenomenon.
|File Size||4 MB||Number of Pages||8|