Abstract
The three-dimensional free surface characteristics of flow around two equal diameter cylinders in a side-by-side arrangement were studied numerically. The flow fields were simulated with a three-dimensional finite volume method based on the RNG k-ɛ model for Reynolds number Re = 1.0 × 104. The volume-of-fluid method was applied to track air–water interfaces. Computations were performed for gap ratios of 1.25, 1.5, and 1.75 to examine the influence of the gap between two cylinders, and for distance to diameter ratios of 8.0 and 1.0 to study the wall proximity effects. The model was verified by comparing it with the other numerical and experimental results. The results indicated that the evolution of the free surface was periodic in time scale. A weak hydraulic jump occurs in the wake flow. Moreover, a significant difference between upstream and downstream free surface elevations exists in the vicinity of the cylinder. A runup in front of the cylinder and a ‘depression’ around the side edge were also observed. Computational results showed that the flow near the two cylinders was pushed outwards, and the flow between the cylinder and the wall was deflected inwards by the wall. The vortex structures on and near the free surface were closely correlated with the free surface. The shedding vortex far from the free surface was not affected.
Highlights
The flow around an isolated or group of cylinders is a classical fluid mechanics phenomenon and has great engineering significance
A deeper understanding of the characteristics of the free surface and the computational method was proven through a comparison with other experimental data and numerical results
Of the free surface and the computational method was proven through a comparison with other experimental data and numerical results
Summary
The flow around an isolated or group of cylinders is a classical fluid mechanics phenomenon and has great engineering significance. Reichl et al [7] numerically investigated two-dimensional flow around a cylinder close to a free surface at a Reynolds number (Re) of 180 for Froude numbers between 0.0 and 0.7 and gap ratios between 0.1 and 5.0. These simulations revealed that the surface deformation was minimal at low Froude numbers of 0.0–0.3 and became substantial at Froude numbers in excess of 0.3–0.4. James et al [12] simulated the flow around the tandem cylinders at Re = 200 when the gap ratio between the moving wall and the cylinder was 0.5 They observed a parallel double-row of vortices during early transition from reattachment to co-shedding, which was caused by wake interference and wall proximity effects.
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