Hydrodynamic Forces on a Large Pipeline and a Small Pipeline in Piggyback Configuration under Wave Action

Experiments on a large pipeline and a small pipeline in a piggyback configuration under regular and irregular waves are carried out. A comparison of the wave forces on the large pipeline and the small pipeline is made. The nondimensional force coefficients for the drag, inertia, and lift are obtained based on theMorison equation. The effects of the Keulegan-Carpenter (KC) number and the spacing ratio between the two pipelines on the force coefficients for the large pipeline, small pipeline, and piggyback pipeline system are investigated. The experimental results indicate that the variation tendencies of the drag coefficients and inertia coefficients with the KC number or the spacing ratio for the large pipeline, small pipeline, and piggyback pipeline system are similar. The variation tendency of the lift coefficient with the spacing ratio for the large pipeline is opposite to that for the small one. DOI: 10.1061/(ASCE)WW.1943-5460.0000144. (C) 2012 American Society of Civil Engineers.