Physical Modelling of Blue Mussel Dropper Lines for the Development of Surrogates and Hydrodynamic Coefficients

Abstract

In this work, laboratory tests with live bivalves as well as the conceptual design of additively manufactured surrogate models are presented. The overall task of this work is to develop a surrogate best fitting to the live mussels tested in accordance to the identified surface descriptor, i.e., the Abbott–Firestone Curve, and to the hydrodynamic behaviour by means of drag and inertia coefficients. To date, very few investigations have focused on loads from currents as well as waves. Therefore, tests with a towing carriage were carried out in a wave flume. A custom-made rack using mounting clamps was built to facilitate carriage-run tests with minimal delays. Blue mussels (Mytilus edulis) extracted from a site in Germany, which were kept in aerated seawater to ensure their survival for the test duration, were used. A set of preliminary results showed drag and inertia coefficients C D and C M ranging from 1.16–3.03 and 0.25 to 1.25. To derive geometrical models of the mussel dropper lines, 3-D point clouds were prepared by means of 3-D laser scanning to obtain a realistic surface model. Centered on the 3-D point cloud, a suitable descriptor for the mass distribution over the surface was identified and three 3-D printed surrogates of the blue mussel were developed for further testing. These were evaluated regarding their fit to the original 3-D point cloud of the live blue mussels via the chosen surface descriptor.

Large-Scale Laboratory Experiments on Mussel Dropper Lines in Ocean Surface Waves

“…Mussels harvested on several materials in the Jade estuary reached a mean length of 4.61 cm, mean width of 5.08 cm and mean height of 1.67 cm after 16 months [66]. Mean length and mean width of mussels grown on a dropper line at the Baltic Sea near Kiel are 4.7 and 2.2 cm, respectively [54].…”

“…Reference [54] gives a detailed description of the creation of three mussel dropper lines surrogates based on a 3D-Scan of an adult blue mussel line encrusted with newly seeded spat from the same aquaculture farm as the lines tested in this work. The authors used the surface descriptor Abbott-Firestone Curve [72] to develop surrogate model geometries with similar characteristics regarding the weighed arithmetic average material distribution.…”

“…Reference [53] were the first to conduct extensive towing and wave tests with live blue mussel dropper lines for experimentally verified force coefficients for offshore bivalve farm design. In light of the large difficulties with live shellfish in freshwater-based laboratory wave tanks, the quality of a dropper line surrogate for wave tests [54], as a strategy of substituting live shellfish testing, was additionally yielding a mean drag coefficient of C D = 2.3 for the live line and C D = 2.4 for the surrogate, as well as mean inertia coefficient of C M = 2.1 for the live line and C M = 2.3 of the surrogate.…”

Extending New Zealand’s Marine Shellfish Aquaculture Into Exposed Environments – Adapting to Modern Anthropogenic Challenges

“…The best designs were modeled and scaled for testing in a wave basin. Designs included research on the drag coefficients of mussels (Landmann et al, 2019) and were scaled for realistic data gathering in the wave basin.…”

Selected Papers from Coastlab18 Conference

“…This book gathers 16 selected papers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] from the conference, attempting to cover, as completely as possible, all the topics presented during Coastalb18. The papers have been accepted after a peer-review process based on their full text.…”