Water jetting arm optimal design consideration for a ROV trencher

ROV trencher is a kind of ROV which trench the sea floor using specifically designed water jetting tool. For this trencher, maximization of trenching depth and trenching speed (or progress rate) are two of key performance, both of which directly depend on the proper design of jetting arm system. In this paper, we discuss some of optimal design considerations for water jetting arm system through laboratory experiments using sandy soil. First, we carry out jetting angle tests to investigate the relationships between jetting angle, traverse rate¹, and trenching depth. And then, with fixed jetting angle, we carry out additional tests to investigate the relationship of jetting power vs. traverse rate vs. trenching depth, from which we can roughly assess the prototype trenching performance using Froude similarity. CFD simulation is also carried out to demonstrate the experiment results. In the case of cohesive clay soil, we assess the prototype trenching performance using existing jet trenching model [1],[2].