Reply To: Comments thru ISOPE

Jingchao Hu

Dear Professor Chung,

Thank you for your questions and we are honored to have your interest in our research point.

For the mechanical collection, actually, we have not tested that method before. According to the results of sea test conducted by OMI, the conclusion that the hydraulic collection method has a higher nodule pick-up efficiency and better adaptability to variations of seabed than mechanical collection was proposed. In our future studies, a quantitative comparative study between the mechanical collection and hydraulic collection will be investigated. And then, we may give more opinions on this issue.

For the question of how to reduce sediments during the nodule collection, we think understanding the mechanism of the hydraulic collection is a critical step. Because the local velocity distribution (or local pressure distribution) near the collector is the essential cause of the nodule pick-up efficiency and the sediment diffusion. We try to reveal the flow field characteristics of the nodule collection flow for different kinds of collectors, then to explain their performances on nodules collection and environmental disturbances. We are dedicated to design the new kind of nodule collector with the flow characteristics like this: the velocity is larger near the top part of nodules and smaller near the bottom. Such nodule collection flow is considered to be beneficial for achieving a larger lift force as well as smaller disturbance to the seabed. Follow-up studies considering the sediments are still needed for us to validate the design of nodule collector, the ratio in collection of nodules and sediments is a matter of great concern to us.

We appreciate your constructive questions.

Jingchao Hu