The occurrence of marine disasters tends to increase in recent years. In many cases, a large quantity of crude oil spilled into the sea from shipwreched tankers in addition to the damage of ship hull. These accidents strongly remind us the necessity of marine environment protection. Based on this experience, we started a project to develop a new technology to recover spilled oil effectively in the open sea. We investigated the barge type Oil Recovery Vessel(length 70m, width 24m, water depth 2.5m), which is generally operated as a multipurpose work vessel for an offshore construction, sea surface cleaning and so on. In order to provide calm water surface in a moon-pool inside a barge type Oil Recovery Vessel, the motion characteristics of the vessel and water surface elevation in the moon-pool in following and head wave have been examined with a 1 / 20 scale model ship of the Oil Recovery Vessel. The model ship consists of 3 parts ; intake, waterway, and moon-pool. In this paper, we compared the effects on the water surface elevation without or with some different kinds of attachments to provide calm water surface in the moon-pool inside the model ship. From these results, we obtained the following concluding remarks. It has been found that the rate of relative motion of water surface in the moon-pool to the incident wave height becomes 0.3〜0.4 and 0.1〜0.2 on the following wave and head wave condition respectively by equipping the Oil Recovery Vessel with these attachments.
