Flow around circular cylinders with very low aspect ratio

Gonçalves, Rodolfo T.; Franzini, Guilherme Rosa; Rosetti, Guilherme F.; Meneghini, Júlio Romano; Fujarra, André Luís Condino

doi:10.1016/j.jfluidstructs.2014.11.003

Cited by 73 publications

(27 citation statements)

References 38 publications

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“…The differences between work by Goncalves et al (2014) and the present study indicate that load results are not universal, but rather that they depend greatly on the F r and Re numbers. Future work will seek to understand this discrepancy in results, whether the difference is due to the F r or Re, or a combination of the two.…”

Section: Accepted Manuscriptcontrasting

confidence: 81%

“…Visualizations of the flow around cylinders at a variety of aspect ratios were provided, showing the effects of a free end. The experimental data provided by Goncalves et al (2014), complements the present work which presents numerical and experimental results up to AR = 19 with measurements at very small aspect A C C E P T E D M A N U S C R I P T ratios. Furthermore, this present work adds to the existing data by providing results at different Re and F r.…”

Section: Surface-piercing Cylinders With Free Endssupporting

confidence: 72%

“…In the present work, the hard surface of the floor is replaced with a deformable water-air fluid interface. Finally, experimental and numerical results from the present work are compared against numerical results by Rosetti et al (2013) and experimental work by Goncalves et al (2014), shown in Figure 10.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Furthermore, the study was limited to a single aspect ratio. Goncalves et al (2014), et al, presented thorough experimental results for varying aspect ratios up to 2 over a range of Re and Fr. The authors noted both a decrease in C d and St with decreasing aspect ratio.…”

Section: Surface-piercing Cylinders With Free Endsmentioning

confidence: 99%

“…Previous to this work, insight about the combined effect of these factors has been presented by a very small number of studies including Hay (1947), Goncalves et al (2014) and Rosetti et al (2013) The present work uses both experimental and numerical results to extend the range of studies to include a wider range of aspect ratios than has previously been presented, and also provides insight about the critical aspect ratio when a free surface is also present. Furthermore, the combination of the two factors is investigated, including which one, if any, is dominant across a range of aspect ratios.…”

Section: Introductionmentioning

confidence: 96%

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CFD simulations and experimental measurements of flow past free-surface piercing, finite length cylinders with varying aspect ratios

et al. 2016

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Highlights• We simulate (with CFD) and experimentally measure loads on surface-piercing cylinders with freeends of varying aspect ratios • A wider range of aspect ratios than has previously been investigated is covered • Drag coefficients and the presence of vortex shedding diminish greatly with decreasing aspect ratio • Furthermore, loads along the length of a cylinder are investigated• The free-surface and free-end affect the load behavior, with ramifications to offshore structural engineering 1 AbstractIn this work, the flow past surface-piercing cylinders with free lower ends is studied numerically with computational fluid dynamics (CFD) at varying aspect ratios (AR = H/D) from around 1 to 19, and compared against experimental measurement across the same range. Numerical and experimental work is carried out at Re = 2900 and Fr = 0.65. The aspect ratio of the cylinder is varied by raising and lowering the cylinder into the water. The resulting flow field and loads on the cylinder as a result of changing the cylinder's depth of submergence are investigated in terms of drag, lift and frequency content. First, the effects of changing the aspect ratio are examined. CFD simulations demonstrate a reduced drag coefficient, consistent with the experimental measurements, as compared to a fully-submerged, infinite cylinder at the same Reynolds number. A significant reduction in the drag coefficient is observed at an aspect ratio of 2. For aspect ratios 3 and below, Karman vortex shedding is completely suppressed due to the dominance of free surface effects. With increasing aspect ratio the Strouhal number is found to approach 0.2. Second, the flow regime is investigated as a function of cylinder length for a cylinder with aspect ratio of 12. Different regions of vortex shedding are observed along the length of the cylinder, as demonstrated by lift forces, Strouhal numbers and CFD flow visualizations. Strouhal numbers below 0.2 were observed for regions near the free surface. Additionally, the drag coefficient was found to decrease near the free surface. This study over a wide range of aspect ratios exhibits the effects of a free surface, free end and also the length of the cylinder on both the flow regime and loading.

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Section: Accepted Manuscriptcontrasting

confidence: 81%

Section: Surface-piercing Cylinders With Free Endssupporting

confidence: 72%