Transverse VIV response of piggyback pipelines with various configurations in ocean current

Transverse vortex-induced vibration of piggyback pipelines under the steady current was physically modeled in a water flume with a hydroelastic system. In each test, the reduced velocity was gradually increased from 0 to about 16, which covers the typical range of the reduced velocity for pipelines in the field condition. The effects of configuration parameters, including the spacing between the piggyback and the main pipe (G/D), the position angle of the piggyback to the main pipe (θ) and the mass ratio (m*) on the vibration amplitude and frequency are investigated. The critical reduced velocity for onset of VIV is also examined.