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Numerical Investigation of the Influence of Span-wise Force Variation in Circular Cylinders Undergoing Vortex Induced Vibrations at High Reynolds Number

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Murrin, D and Militzer, J and Bose, N and Campregher, R (2007) Numerical Investigation of the Influence of Span-wise Force Variation in Circular Cylinders Undergoing Vortex Induced Vibrations at High Reynolds Number. In: On the Edge of Tomorrow -MTS/IEEE Oceans 2007, Vancouver.

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Abstract

The focus of this research is on the development
of a new approach for simulating vortex induced vibrations on
marine risers at high Reynolds numbers. This method considers
the span-wise variation of the lift and drag forces, and determines
the moment acting on the cylinder. The predicted motion then
consists of a rotational component to accompany the traditional
cross-stream and stream-wise translations normally associated
with vortex induced vibrations. This was accomplished by describing
the motion of the cylinder using a set of springs and
dampers. A moment acting on the cylinder causes the springs on
one end to compress, and stretch on the other, thus rotating the
cylinder.
A Large Eddy Simulation (LES) computational fluid dynamics
code running on 16 3Ghz processors was used to calculate the
unsteady flow and at each time step the hydrodynamic forces
acting on the cylinder were calculated in a separate routine based
on the pressure distribution around the cylinder. This information
was then used to solve two second-order ordinary differential
equations, which gave the velocity and displacement of the
cylinder in cross-flow and rotational planes. This information was
transferred back to the code where the cylinder was displaced
and another cycle of calculations was started.
The simulated results showed that the correlation length was
higher for a cylinder subject to pure translation compared to a
cylinder free to translate and rotate in the cross-stream direction.
This has implications for current numerical and experimental
techniques since it has been traditionally assumed that the
flow around a circular cylinder becomes two-dimensional during
vortex induced vibrations. Consequently, empirical,numerical
and experimental models have generally only considered cross
stream and/or stream-wise translation. The extent to which the
experimental apparatus or harmonic model may have influenced
the behavior of the riser by eliminating span-wise amplitude
variation is important information that should be considered for
future riser designs.

Item Type: Conference or Workshop Item (Paper)
Keywords: marine riser, VIV, CFD, numerical wind tunnel
Date Deposited: 04 Mar 2008 01:03
Last Modified: 18 Nov 2014 03:30
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