Experimental and Numerical Study on Flow Past Four Rectangular Columns in Diamond Configuration

Abstract

Vortex-Induced-Motions (VIM) is a cyclic rigid body motion that is induced by vortex shedding of a large sized floating structure (Spar, Semi-Submersible and Tension-Leg Platform) in deep water. Since the potential impact of VIM on fatigue life of mooring and riser systems can be critical, the study of the VIM phenomenon has drawn considerable attention among offshore engineering community. Despite the effort, there is still lack of understanding the complex fluid-structure interaction phenomenon. To date, it is very much relying on the simplified empirical approach in practical design. Most of the Semi-Submersibles consist of four rounded-cornered rectangular columns. To investigate the flow interaction between each columns can reveal some physics behind the VIM. In this study, flow past four stationary rounded-corner rectangular columns are tested in the circulating channel and numerically simulated by the Star-CCM+ CFD package. Forces on the columns and the flow characteristics behind the structures are present in this study. A 2-D particle imaging velocimetry (PIV) technic has been adopted in present study to obtain the flow characteristics. The aim of this study is to investigate the interactions between four square columns.

Hydrodynamics Around a Deep-Draft Semi-Submersible With Various Corner Shapes

“…Three different corner shapes (sharp, chamfered and rounded) of a typical deep-draft semi-submersible under 45 degree flow incidence have been numerically investigated after present and previous rigorous validations [21][22][23] against the experimental data. The hydrodynamic loads on different members of the structure, such as four columns and pontoons, are compared in order to quantify the corner shape effects.…”

“…For all of the simulations, a 9B L × 6B L × 3B T sized computational domain was used in the present simulations (where B L is the overall width of the structure and B T is the draft of the structure). Zou, Lin and Lam [18] In the earlier study [21], a computational domain size of 9.5B L × 6.3B L × 3B T was employed. Compared with aforementioned computational domain sizes, a 9B L × 6B L × 3B T domain (see Figure 3) was considered to be sufficiently large to eliminate both the far field effects from the boundaries and the three-dimensional effects from a spanwise cross flow direction.…”

Vortex shedding characteristics of multi-column structure with or without horizontal connections

“…Koop et al [24], however, chose a 10B L × 6B T cylindrical domain for simulating flow with their numerical models. In our earlier study [18], a computational domain size of 9.5B L × 6.3B L × 3B T was employed. Compared with aforementioned computational domain sizes, a 9B L × 6B L × 3B T domain was considered to be sufficiently large to eliminate the far field effects from the boundaries and the three-dimensional effects from a spanwise cross flow direction.…”

“…However, for the case of cross-flow around a group of cylinders each with free end, there is still a lack of understanding on this complex interaction. Liang et al [18] conducted a preliminary study on flow past four free end rectangular section columns by both experimental and numerical routines. In this study, the cross-flow around four free end rectangular columns with and without pontoons in a diamond configuration, i.e.…”