A towed ground effect vehicle for sea floor mapping and fish survey

Abstract

Ireland's coastal and marine environments hold significant sand and gravel resources. A 1989 Geological Survey of Ireland (GSI) Report noted that sand and gravel is a valuable but depleting resource. The extraction of sands and gravels from near shore waters can have implications for the management of coasts, tourism and the fishing industry. Available underwater vehicles are controlled in three dimensions using directional wing and variable buoyancy. This study shows that a ballast solution is not suitable to control a close-ground towed vehicle able to avoid obstacles. It also shows that a directional wing solution, using the angle of attack to create a lift is more realistic than the ballast system. However, this design would need to be driven by a close loop control system which induce a high manufacturing, maintaining and running cost for the only driving function of the vehicle. None of the existing submarine products are using ground effect to fly over the sea bed. The objective is to develop a towed underwater vehicle, able to fly at constant distance from the sea bed, cheap to produce, maintain and run. This device would optimise the efficiency and cost of continental shelf survey. The aim of this study is to establish the feasibility of such a vehicle, and propose a conceptual design of a wing able to fly at a constant distance from the sea bed. This work present a Computational Fluid Dynamics (CFD) analysis performed on different wing designs, the towing tank and wing models build to conduct experimental tests, and a conceptual design of the vehicle. In conclusion from the CFD analysis and the experimental tests, the concept of ground effect, which has never really been studied for underwater applications, is realistic solution to optimise the efficiency and cost of continental shelf survey.