Forces on Vibrating Cylinder Near Wall in Current and Waves

Forces on a vibrating pipeline have been measured by measuring the instantaneous pressure in eight pressure cells around a vibrating cylinder. The cylinder can only vibrate in the cross‐flow direction. The vibrations are forced. The waves are introduced by the carriage technique. For the current‐alone case it turns out that the drag and the lift increase significantly with increasing amplitude of vibration. The influence is most pronounced at small values of the reduced velocity, where the increase can be up to a factor 3–4 for a free cylinder. Closer to the wall the influence is smaller for the drag, but very large for the lift. In the wave case, the drag, the inertia force, and the lift increase when the pipe is vibrating; the increase in drag is most pronounced for small KC‐numbers while the opposite is the case with respect to the inertia coefficient. The increase in the drag coefficient for a free cylinder is 50–200% for KC about 10 and nearly negligible for KC larger than 60. The similar (opposite) variation is smaller concerning the inertia coefficient where the increase can be up to 30%. Regarding the lift force, an increase up to 200% is observed. Increase in the force coefficients becomes similar to the current‐alone case; smaller increase with decreasing gap, however.