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DISCUSSION

J.M.R.Graham

Imperial College, United Kingdom

The three-dimensional simulations have produced some very interesting results. In the case of the traveling wave, locking-on of vortex shedding should be similar to locking of two-dimensional vortex shedding by oscillation of the cylinder, with constant amplitude and phase along the span. In the case of the standing waves there are two opposite effects. The oscillation tends to control and possibly strengthen non-oblique vortex shedding, when locked on, but the three-dimensional effect of the phase variation limits this to finite length spanwise cells of alternating sign which might be expected to weaken the vortex shedding. Can any observations be made from your three-dimensional results about the lock-in boundaries (oscillation amplitude vs. frequency ratio) for these two cases (traveling and standing wave), as a function of spanwise wavelength?

AUTHORS' REPLY

The current paper deals with the question of modeling the coupled motions of cable and wake using low-dimensional constructs. It does not deal directly with the lock-in boundaries that Professor Graham addresses. From ongoing work, however, we have concluded that the same dynamics encountered in simply dynamical systems and in the two-dimensional case is also present in the cable system. We have not yet determined the exact boundaries of the lock-in for the standing and traveling wave response on which we will report in a future publication.



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