FIELD OBSERVATION OF SEAWATER SPRAY DROPLETS IMPINGING ON THE UPPER DECK OF AN ICEBREAKER

摘要

Seawater spray icing is a major problem faced not only by fishing vessels and trawlers but also by commercial vessels. Marine disasters caused by ice accretion occur frequently in cold regions. However, even today, deicing continues to be a manual operation that usually involves the use of a hammer. To address icing on the ship, sea spray generation, spray delivery, and heat transfer for ice accretion are important. In this study, we developed a seawater droplet counter for measuring the droplets impinging on ships. The field observation was made on the upper deck of the CCGS Louis S. St-Laurent during the voyage to the Northwest Passage and the Canada Basin. Because the observation period was late July and August of 2012, the purpose of this observation was to obtain the relationship between pitching and rolling of the ship and seawater spray generation. The weather conditions, acceleration of the ship, and size and number of seawater droplets were measured. The marine condition and spray generation were recorded by using a monitoring system set up on the upper deck of the ship. Droplet size distributions were obtained in rough weather. Preliminary result shows that long-period swells did not contribute to the increase in the amount of seawater spray, although the pitching angle of the ship increased with swell. The seawater droplet counter recorded large numbers of particles during a storm. The time series of the droplet counter suggested that the particles were caused by raindrops, because droplets were detected continuously.