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

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

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.
Original languageEnglish
Title of host publicationProceedings of the World Dredging Conference, WODCON XXIII
Subtitle of host publicationDredging is Changing
PublisherWODA
Number of pages8
Publication statusPublished - 2022
EventWODCON XXIII - Tivoli Hotel, Copenhagen, Denmark
Duration: 16 May 202220 May 2022

Conference

ConferenceWODCON XXIII
Country/TerritoryDenmark
CityCopenhagen
Period16/05/2220/05/22

Keywords

  • deep sea mining
  • sediment erosion
  • polymetallic nodules
  • hydraulic collector
  • Coandă effect

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