Measurements are made of vortex-induced vibration of an elastically supported circular cylinder in water with reduced velocity (U/fnD) from 2 to 12, damping factors (ζ) from 0.2% to 40% of critical damping, mass ratios (m/ρD2) from π/2 to π/17, and transverse, inline, and combined inline and transverse motions at Reynolds numbers up to 150,000. Effects of mass, damping, Reynolds number, and strakes on vortex-induced vibration amplitude, frequency, entrainment, and drag are reported.
Significant riser oscillations were observed during deep-water drilling operations. The riser vibrated at frequencies from below to above the rotation speed of the drill pipe. Laboratory tests of a riser section have been conducted for these riser drilling-induced vibrations. The first test consisted of measuring the fluid forces between the rotating drill pipe and the riser. In the second test, the riser was elastically supported. The riser self-excited about the rotating drill pipe. An analytical model is developed for predicting these drilling-induced riser oscillations. The results show that fluid-coupled riser vibrations can result from the fluid forces generated in the annular fluid between the rotating drill pipe and the riser. NOMENCLATURE D d = drill pipe outside diameter D o = riser outside diameter D r = riser inside diameter r = distance from center of riser to center of drill pipe
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