A DIRECT NUMERICAL-SIMULATION STUDY OF FLOW PAST A FREELY VIBRATING CABLE

We present simulation results of flow-induced vibrations of an infinit ely long flexible cable at Reynolds numbers Re = 100 and Re = 200, cor responding to laminar and early transitional flow states, respectively . The question as to what cable motions and flow patterns prevail is i nvestigated in detail. Both standing wave and travelling wave response s are realized but in general the travelling wave is the preferred res ponse. A standing wave cable response produces an interwoven pattern o f vorticity, while a travelling wave cable response produces oblique v ortex shedding. A sheared inflow produces a mixed standing wave/travel ling wave cable response and chevron-like patterns with vortex disloca tions in the wake. The lift force on the cable as well as its motion a mplitudes are larger for the standing wave response. At Re = 200, the cable and wake response are no longer periodic, and the maximum amplit ude of the cable is about one cylinder diameter, in agreement with exp erimental results.