scholarly journals Triggering mechanics for transverse vibrations of a circular cylinder in a shear flow: Wall-proximity effects

2022 ◽  
Vol 108 ◽  
pp. 103423
Author(s):  
Jun Liu ◽  
Fu-Ping Gao
Keyword(s):  
Circular Cylinder ◽  
Shear Flow ◽  
Proximity Effects ◽  
Transverse Vibrations ◽  
Wall Proximity

Two-Dimensional Numerical Simulations of Wall Proximity Effect on Cylinders

2015 ◽  
Author(s):  
Zhong Li ◽  
Rajeev K. Jaiman ◽  
Mun Yew Daniel Tham ◽  
Boo Cheong Khoo
Keyword(s):  
Circular Cylinder ◽  
Proximity Effects ◽  
Displacement Amplitude ◽  
Plane Boundary ◽  
Transverse Displacement ◽  
Two Dimensional ◽  
Immersed Interface Method ◽  
The Mean ◽  
Wall Proximity ◽  
Near Wall

In the oil and offshore industry, it is a common phenomenon that subsea pipelines placed on or in the proximity of the seabed are exposed to underwater waves and currents. Free spanning in sections along the length of pipeline frequently results from the erosion of sediments or the irregular terrain. This scenario can be modelled by a much more simplified set-up, where a circular cylinder situated near a plane wall is subjected to the oncoming flows. In this case, unlike the well-studied isolated cylinder, the hydrodynamic forces exerting on the near-wall cylinder will depend largely upon on the gap between the wall and the cylinder itself. In this work, flows around a stationary and a freely vibrating two-dimensional circular cylinder near a plane boundary are numerically simulated using the Immersed Interface Method (IIM) and Finite Element Method (FEM) with Arbitrary Lagrangian-Eulerian (ALE) approach, respectively. In the case of a stationary cylinder, instead of a fixed wall, a moving wall with no-slip boundary is considered in order to avoid the complex involvement of the boundary layer and to focus only on the shear-free wall proximity effects in evaluating the lift and drag forces in the low Reynolds number regime (Re ≤ 200), with the aim of validating our IIM solver since it is the first time to apply IIM in solving flows past a near-wall cylinder. The gap ratio e/D is typically taken from 0.1 to 2.0 in this part of studies, where e denotes the gap between the cylinder and the wall and D denotes the diameter of the cylinder. The key findings are that the mean drag coefficient increases and peaks at e/D = 0.5 with the increase of e/D and keeps decreasing from e/D = 0.5 to e/D = 2.0, while the mean lift coefficient decreases monotonically with the increase of e/D. In the case of the freely vibrating cylinder in both transverse and in-line directions, the fixed wall is used to include the shear-layer effect from the bottom wall in considering the near-wall vortex-induced vibration (VIV) by using FEM with ALE approach. It can be concluded from our observations that when the cylinder is brought closer to the wall from e/D = 10.0 to e/D = 0.75, the peak transverse displacement amplitude decreases, while the peak in-line displacement amplitude increases, by greater than 20 times that of an isolated cylinder.

Vortex shedding from a circular cylinder in moderate-Reynolds-number shear flow

1980 ◽  
Vol 101 (4) ◽  
pp. 721-735 ◽  
Author(s):  
Masaru Kiya ◽  
Hisataka Tamura ◽  
Mikio Arie
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Shear Flow ◽  
Vortex Shedding ◽  
Transverse Velocity ◽  
Number Range ◽  
Uniform Shear ◽  
Reynolds Number Range ◽  
Moderate Reynolds Number ◽  
Shear Parameter

The frequency of vortex shedding from a circular cylinder in a uniform shear flow and the flow patterns around it were experimentally investigated. The Reynolds number Re, which was defined in terms of the cylinder diameter and the approaching velocity at its centre, ranged from 35 to 1500. The shear parameter, which is the transverse velocity gradient of the shear flow non-dimensionalized by the above two quantities, was varied from 0 to 0·25. The critical Reynolds number beyond which vortex shedding from the cylinder occurred was found to be higher than that for a uniform stream and increased approximately linearly with increasing shear parameter when it was larger than about 0·06. In the Reynolds-number range 43 < Re < 220, the vortex shedding disappeared for sufficiently large shear parameters. Moreover, in the Reynolds-number range 100 < Re < 1000, the Strouhal number increased as the shear parameter increased beyond about 0·1.

Investigation of Wedge Probe Wall Proximity Effects: Part 2—Numerical and Analytical Modeling

1997 ◽  
Vol 119 (3) ◽  
pp. 605-611 ◽  
Author(s):  
P. D. Smout ◽  
P. C. Ivey
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Outer Wall ◽  
Aerodynamic Characteristics ◽  
Proximity Effects ◽  
Wake Flow ◽  
Scale Model ◽  
Flow Structures ◽  
Flow Features ◽  
Wall Proximity

An experimental study of wedge probe wall proximity effects is described in Part 1 of this paper. Actual size and large-scale model probes were tested to understand the mechanisms responsible for this effect, by which free-stream pressure near the outer wall of a turbomachine may be overindicated by up to 20 percent dynamic head. CFD calculations of the flow over two-dimensional wedge shapes and a three-dimensional wedge probe were made in support of the experiments, and are reported in this paper. Key flow structures in the probe wake were identified that control the pressures indicated by the probe in a given environment. It is shown that probe aerodynamic characteristics will change if the wake flow structures are modified, for example by traversing close to the wall, or by calibrating the probe in an open jet rather than in a closed section wind tunnel. A simple analytical model of the probe local flows was derived from the CFD results. It is shown by comparison with experiment that this model captures the dominant flow features.

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