A direct numerical simulation study of flow past a freely vibrating cable

We present simulation results of flow-induced vibrations of an infinitely long flexible cable at Reynolds numbers Re = 100 and Re = 200, corresponding to laminar and early transitional flow states, respectively. The question as to what cable motions and flow patterns prevail is investigated in detail. Both standing wave and travelling wave responses are realized but in general the travelling wave is the preferred response. A standing wave cable response produces an interwoven pattern of vorticity, while a travelling wave cable response produces oblique vortex shedding. A sheared inflow produces a mixed standing wave/travelling wave cable response and chevron-like patterns with vortex dislocations in the wake. The lift force on the cable as well as its motion amplitudes are larger for the standing wave response. At Re = 200, the cable and wake response are no longer periodic, and the maximum amplitude of the cable is about one cylinder diameter, in agreement with experimental results.