Experimental investigation of sediment erosion generated by a coandă-effect-based polymetallic-nodule collector

Conference paper (2022)

Authors

S.M.S. Alhaddad Offshore and Dredging Engineering - Mechanical, Maritime and Materials Engineering
R.L.J. Helmons Offshore and Dredging Engineering - Mechanical, Maritime and Materials Engineering , Norwegian University of Science and Technology (NTNU)
Research Group
Offshore and Dredging Engineering (Mechanical, Maritime and Materials Engineering) (TU Delft)
Copyright: © 2022 S.M.S. Alhaddad, R.L.J. Helmons
Deep sea mining Polymetallic nodules Coandă effect Hydraulic collector Sediment erosion
More Info
expand_more

Published Date

2022

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Faculty

Mechanical, Maritime and Materials Engineering

Department

Marine and Transport Technology

Research Group

Offshore and Dredging Engineering

Abstract

Owing to the absence of direct contact between hydraulic polymetallic-nodule collectors and seabed, hydraulic collection is deemed, from an environmental point of view, the most preferred technique in nodule mining. To design a hydraulic collector that results in minimum sediment disturbance, it is crucial to develop a solid understanding of the interaction between the collector and the sea bed. To this end, we performed a series of small-scale experiments where several operational conditions were tested, yielding the first quantitative data for sediment erosion resulting from the movement of a hydraulic collector over a sand bed. This paper presents and discusses the experimental results and observations. It is found that the collector’s forward velocity is inversely proportional to the bed-sediment erosion depth, since the bed is exposed to the flow for a longer time when the collector drives slower and vice versa. Contrarily, an increased jet velocity leads to a larger erosion depth. Furthermore, when the collector underside is nearer to the bed, a larger sediment layer is exposed to the water flow, resulting in a larger erosion depth. Finally, the experimental results show that a larger amount of water entrained into the collection duct results in a smaller erosion depth, implying that the flow velocities under the collector are lower in this case.