Experimental study of characteristics of sidewall green water event for a ship-type FPSO under irregular wave conditions

This study conducted an experimental investigation into the characteristics of the sidewall green water problem of a ship-type floating production storage and offloading (FPSO) under irregular waves. The study applied three different irregular waves and two different heading angles. Relative wave elevations were measured using 12 wave probes on the deck and side of the FPSO model, along with the forces acting on pillars during the green water event. The process of the sidewall green water event was studied, investigating variations in relative wave elevations and forces acting on the pillars based on the heading angle. The experimental results examined correlations between the vertical motions of the FPSO model and relative wave elevations. Bow green water events at heading angles of 165° and 150° were mainly affected by the pitch and roll motions of the FPSO model, respectively. Additionally, it was found that the side green water event is affected by the heave motion of the FPSO model. •In order to investigate the characteristics of bow and sidewall green water phenomena under irregular wave conditions, the experiments were conducted using the FPSO of ship-type with 12 wave probes and 2-components loadcells.•Regular waves were generated to investigate the phenomena of sidewall green water, and the phenomena of sidewall green water were as following. (i) The wave propagated along the FPSO sidewall, while the bow green water passed on the deck of the FPSO; (ii) during the wave propagation, the wave was progressing higher on the sidewall of FPSO. (iii) The relative wave elevation rised and exceeded the freeboard of the FPSO when the wave arrived near the midship of the FPSO.•In the irregular wave test, the roll motion of FPSO in heading = 165° was relatively smaller than that of heading = 150°. So, the forces on Pillars for heading = 150° gradually increased from Pillar#1 to Pillar#3. For heading = 165°, relatively small green water loads occurred on Pillar#2, and there were relatively large bow side and sidewall green water loads on Pillar#1 and Pillar#3, respectively.•From the irregular wave tests, correlations between the relative wave elevations and vertical motions attributable to the bow and sidewall green water events were investigated. Bow green water events mainly occurred by the pitch and roll motions for heading conditions of 165° and 150°, respectively. Side wall green water events could occur by not only the developed wave on the sidewall of FP