| Summary: | 碩士 === 國立臺灣大學 === 生物環境系統工程學研究所 === 101 === In this study, flows through porous cylinders are simulated by three-dimensional computational fluid dynamics software FLUENT and their acting forces in different water depths are discussed. The standard k-ε turbulent model and the volume fluid method (VOF) are adopted to describe the turbulent flows with free surface. To reflect the blockage effect of flows through porous cylinders, a porous media theory is introduced herein. The simulated results against the experimental data show good agreement.
The resistant forces on a single cylinder with various porosities in various water depths are investigated. It is found that the resistant force increases as the water depth increases in non-submerged flows while the resistant force decreases as the water depth increases in submerged flows. In the cases of multi-row cylinders, four scenarios such as Scenario A: non-staggered porous cylinders in submerged flows, Scenario B: non-staggered solid cylinders in submerged flows, Scenario C: staggered porous cylinders in submerged flows and Scenario D: non-staggered porous cylinders in non-submerged flows are performed. To summary, from Scenarios A and B, the reduction rates in average force are respectively 17% and 11% for porous and solid cylinders. It means that the interacting effect between two rows of porous cylinders is more significant. To compare Scenarios A and C, the reduction rate in average force as 25% in staggered arrangements is larger than that as 17% in non-staggered arrangements. It can be found that the reduction rate in average force is 27% in non-submerged flows while that is 17% in submerged flows in Scenarios A and D.
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