In Lazy S system, the riser is similar to free-hanging catenary but has support provided at about Mid-Water by an arch structure. One of the main functions for the introduction of a Mid-Water Arch (MWA) into a riser system is to provide a filter to stop the direct transfer of dynamic tension amplitude to the Touch-down Point (TDP) on seabed that occurs with the free-hanging configuration. By using the Morison equation to calculate the wave loads on a MWA, the difficulty is to determine correct hydrodynamic coefficients. Analysis was performed by using Orcaflex to investigate the effect of hydrodynamic coefficients on the MWA loadings. Dynamic analysis was run under Airy wave with different drag force and added mass coefficients. The effect of drag moment of area was considered as well. Base on the comparison among the simulation results, some conclusions and discussion were presented.
