Study of ballast water exchange by pumping-through method

The authors present results of experiments and numerical calculation of the ballast water exchange from a 2D model tank using pumping through method. In recent years discharged ballast water from the ships has been identified as a potential threat to the marine environment. Many kinds of species are included in the discharged ballast water and these are transferred from one port to another. Breed species have some potential that cause severe adverse impact on ecology including expulsion of native organisms. It probably effects the human society as well. In view of this problem the IMO (International Maritime Organization) was adopted "Regulations for the control and management of ship's ballast water and sediments" in 2004. It is mandatory that all the ships should comply with "Ballast Water Performance Standard" by 2016. It was suggested that ballast water exchange is made using the pumping-through (flow-through) method until 2016. By using this method, it is assumed that 95% of the ballast water exchange is possible if seawater of 3 times of ballast tank capacity is overflowed. However there are only few studies on the verification of the volume of ballast water discharge using this method. Thus it is necessary to check the efficiency of this procedure. The experiments results show that the pumping-through method can dilute about 95% of ballast water if the volume of 3 times the capacity of the model tank is overflow. In this experiment we used a 2D square tank model of 1 m on all sides and measured the dilution rate of the inside fluid with an optical method. Also we analyzed the motion of fluid inside the tank using the MPS method as a numerical calculation and compared with the experiment results.