Experimental Investigation on Characteristics of Flow Field in ‘Suck-up-based’ and ‘Coandă-Effectbased’ nodule pick-up devices

摘要

Being one of the most challenging technologies in deep sea miningsystem, nodules collecting process near seabed is paid great attentionbecause it will directly influence the collecting efficiency and seafloordisturbance. Two models of nodule pick-up devices, namely suck-upbasedmodel and Coandă-effect-based model are investigated with focuson the nodules collecting flow field with and without the sphere. Theflow field information near the nodule pick-up device is measured byusing particle image velocimetry (PIV) system. Velocity vectors,streamlines, and velocity distributions are measured and analyzed toinvestigate the similarities and differences in collecting flow fieldsbetween the two different nodule pick-up devices. The results show that:for suck-up-based model, flow velocity v increases exponentially withthe distance to the bottom h in vertical direction in a certain area; forCoandă-effect-based model, three regions can be divided to describe thechanges of velocity along the horizontal direction according to theaverage value and amplitude of variation. For both models, the velocityvalue near the bottom is relatively small and this will be beneficial inminimizing the sediment disruptions. This study is expected to be usefulfor further understanding the mechanism of nodules collecting based on‘suck-up’ and ‘Coandă-effect’ and provide references for the assessmentof the impact on the seafloor environment and optimal design of nodulepick-up devices.