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TECHNICAL PAPERS

Three-Dimensional Numerical Simulations of Circular Cylinders Undergoing Two Degree-of-Freedom Vortex-Induced Vibrations

[+] Author and Article Information
Juan P. Pontaza

Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843

Hamn-Ching Chen

Department of Civil Engineering, Ocean Engineering Program, Texas A&M University, College Station, Texas 77843

J. Offshore Mech. Arct. Eng 129(3), 158-164 (Nov 12, 2006) (7 pages) doi:10.1115/1.2746396 History: Received April 17, 2006; Revised November 12, 2006

Abstract

In an effort to gain a better understanding of vortex-induced vibrations (VIV), we present three-dimensional numerical simulations of VIV of circular cylinders. We consider operating conditions that correspond to a Reynolds number of $105$, low structural mass and damping ($m*=1.0$, $ζ*=0.005$), a reduced velocity of $U*=6.0$, and allow for two degree-of-freedom ($X$ and $Y$) motion. The numerical implementation makes use of overset (Chimera) grids, in a multiple block environment where the workload associated with the blocks is distributed among multiple processors working in parallel. The three-dimensional grid around the cylinder is allowed to undergo arbitrary motions with respect to fixed background grids, eliminating the need for grid regeneration as the structure moves on the fluid mesh.

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Figures

Figure 1

A “Z-slice” of the computational domain showing the multiple-block structure of the Chimera grid in the XY plane

Figure 2

Spanwise cut along Y=0.0 showing the grid distribution on the spanwise direction. Blocks in the vicinity of the cylinder have higher spanwise resolution.

Figure 3

(a) Instantaneous spanwise velocity contours for the flow past a fixed cylinder. Contour range [−0.2,0.2]. (b) Instantaneous cross-flow vorticity contours for the flow past a fixed cylinder. Contour range [−2,2]. (c) Instantaneous streamwise vorticity isosurfaces for the flow past a fixed cylinder. Isosurfaces +0.5 and −0.5. (d) Instantaneous spanwise vorticity isosurfaces for flow past a fixed cylinder. Isosurfaces range [−4,4].

Figure 4

Power spectra of streamwise and cross-flow velocities in the near wake of the cylinder

Figure 5

XY trajectory swept by the cylinder due to VIV. The response is a “figure-of-eight” pattern of body motion.

Figure 6

Spanwise vorticity contours on the XY plane Z=1.5, showing the 2S mode of vortex shedding

Figure 7

Instantaneous spanwise vorticity isosurfaces for two-degree-of-freedom VIV of a circular cylinder. Isosurfaces range [−4,4].

Figure 8

Time histories of transverse (cross-stream) displacement and lift coefficient. The corresponding phase plot is also shown.

Figure 9

Power spectrum of the time history of the lift coefficient, showing a strong 3× harmonic

Figure 10

Phase plot of the drag and lift coefficients. Average and fluctuating values can be obtained from the plot.

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