The effect of air–water interface on the vortex shedding from a vertical circular cylinder

Suh, Jungsoo; Yang, Jianming; Stern, Frederick

doi:10.1016/j.jfluidstructs.2010.09.001

Cited by 52 publications

(47 citation statements)

References 32 publications

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“…However, near the free surface the drag coefficient decreases rapidly, a trend that is consistent with previous studies found in the literature, e.g. Chaplin and Teigen (2003), Kawamura et al (2002), Yu et al (2008), Suh et al (2011). Additionally, an increase in the drag coefficient can be seen at the bottom of the cylinder where the flow is altered due to the tip vortices from the free end.…”

Section: Sectional Forcessupporting

confidence: 90%

“…Numerical work on the drag coefficients of surface-piercing cylinders has been carried out by Kawamura et al (2002), Yu et al (2008) and Suh et al (2011). In each of the papers, the drag coefficient for the cylinder in the presence of a free surface was found to be smaller than the subcritical constant value of 1.2 at Reynolds numbers below 1.4 × 10 5 for a fully submerged cylinder.…”

Section: Surface-piercing Cylindersmentioning

confidence: 99%

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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: Sectional Forcessupporting

confidence: 90%

Section: Surface-piercing Cylindersmentioning

confidence: 99%

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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“…14 are similar to those from experiment and CFD simulation for a vertical cylinder in steady current [19]. For present case, however, Kevin wave pattern behind the cylinder is less clear and diffraction from the cylinder spreads further toward upstream, which is attributed to high Re and low Fr compared to Re = 2.7 × 10 4 and Fr = 0.8 in [19].…”

Section: Wave Diffraction Analysissupporting

confidence: 81%

High-fidelity CFD simulation of wave run-up for single/multiple surface-piercing cylinders in regular head waves

Yoon

Kim

Sadat-Hosseini

et al. 2016

Applied Ocean Research

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a b s t r a c tThe capabilities of CFDShip-Iowa V4.5 and V6.2 simulations for wave run-up for single/multiple surface-piercing cylinders in regular waves are assessed in conjunction with the ITTC OEC Workshop on VIV and Wave Run-up held in Nantes, France October 17-18, 2013. Statistical convergence and grid/domain/turbulence model sensitivity studies show uncertainty U I values are less than 1% for both the experiment/simulation data and grid/domain/turbulence model sensitivities are less than the facility bias U FB . Simulations are qualitatively validated using U FB and error E between experiment and simulation. Errors for single/four cylinder(s) are comparable with U FB and average errorĒ for the other CFD data of the workshop participants. Results from both V4.5 and V6.2 agree well with experiment and also show capabilities to apply for complex/large-scale problem and to describe detailed wave breaking/spraying for V4.5 and V6.2, respectively. Study on run-up profile shows mean wave elevations are similar to free surface elevations for a cylinder in a steady current. For wave steepness/wave length effect, 2nd to 1st harmonic ratio on the cylinder weather face decreases with steepness for short wave, but increases for long wave. Wave diffraction analysis shows that 2nd/3rd to 1st harmonic ratio in diffracted wave contour reach up to 18-41%/9-16% respectively. Due to interaction between cylinders, crest/trough heights increase 5-17%/4-10% for 4C, respectively. Study on vortex shedding shows short wave has insufficient time to develop periodic vortex shedding compared to long wave.

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“…The CFDShip-Iowa V6.2 [22] is an orthogonal curvilinear grid solver, which is extended from the sharp interface Cartesian grid solver (Version 6.1) for incompressible two-phase viscous flows recently developed at the University of Iowa [23]. In this solver, the interface is tracked by a new volume-of-fluid (VOF) method [24].…”

Section: Cfdship-iowa V62mentioning

confidence: 99%

URANS studies of hydrodynamic performance and slamming loads on high-speed planing hulls in calm water and waves for deep and shallow conditions

Mousaviraad

Wang

Stern

2015

Applied Ocean Research

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a b s t r a c t URANS capability for hydrodynamic performance and slamming of high speed planing crafts are assessed, using metrics specified for naval applications. Wedge drop validation studies using two different solvers, one single-phase and the other two-phase, shows good agreement with experimental data for time history of pressure gauges. Planing hull validation studies are carried out using the historical benchmark experiments of Fridsma. Simulation conditions include calm water in deep and shallow conditions with fixed and free to sinkage and trim motions, as well as regular and irregular head waves in deep water free to heave and pitch motions. For simulations in calm deep water free to sinkage and trim, grid studies show that refined grid density on the hull, especially over the spray root area, chines, and transom stern are necessary for accurate solutions. Detailed verification and validation studies are carried out with satisfactory results since monotonic convergence and validation are achieved for most of the variables. Additional assessment metrics are studied including wave rise, hull pressure distribution, surface streamlines, existence of porpoising, and main spray trajectory. The results are compared with empirical expressions with reasonably good agreement except for main spray trajectory. Resolving the details of the spray flow is beyond the scope of the current work since finer grid resolution and/or more advanced free surface modeling is required. For simulations in calm deep water with fixed sinkage and trim, the assessment metrics include drag and lift forces, pitch moment, drag-lift ratio, and center of pressure. The results agree well with empirical expressions. For simulations in shallow water, similar studies are carried out and reasonable comparison results are obtained. Seakeeping simulations in regular head waves are carried out and validated with experimental data for response amplitudes and phases, with good agreement. Simulations in irregular head waves are carried out for two different weight configurations and validated against experiments for mean and amplitudes of resistance, heave, pitch, and acceleration. Slamming load analysis is carried out, where both emerging and re-entering slams are detected, although the current experimental data lack slamming pressures for validation. More recent research provides additional studies for calm water motions, slamming pressures, and spray flow trajectory that supports current results.

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The effect of air–water interface on the vortex shedding from a vertical circular cylinder

Cited by 52 publications

References 32 publications

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

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

High-fidelity CFD simulation of wave run-up for single/multiple surface-piercing cylinders in regular head waves

URANS studies of hydrodynamic performance and slamming loads on high-speed planing hulls in calm water and waves for deep and shallow conditions

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