A CFD study on the performance of a passive ocean plastic collector under rough sea conditions

In this study, a commercial CFD code, STARCCM+, is used to analyze the performance of a passive ocean plastic collector under rough sea conditions. The CFD code was first validated by comparing with data from a scaled model experiment conducted in the towing water tank in National Cheng Kung University, and it was proven to return accurate catch rate. Then thirty-eight test cases were setup to investigate the effects of four different parameters, namely, ocean current speed, wave height, wave length, and plastic density, on the plastic collector's catch rate, which is the percentage of incoming plastic debris intercepted by the plastic collector. It was found that the parameters of wave length and plastic density posed very little effect on catch rate. In contrast, the effects of the other two parameters were significant. Two important thresholds were found, and they were ocean current speed of 2.5 ms−1 and wave height of 0.4 m. The catch rate remained at high level until these thresholds were reached. The information found in this study is invaluable for the design of a practical passive ocean plastic collector.