| 1 | Comparative Study of Two Approaches to Model the Offshore Fish Cages显示文摘The goal of this paper is to provide a comparative analysis of two commonly used approaches to discretize offshore fish cages: the lumped-mass approach and the finite element technique. Two case studies are chosen to compare predictions of the LMA(lumped-mass approach) and FEA(finite element analysis) based numerical modeling techniques. In both case studies, we consider several loading conditions consisting of different uniform currents and monochromatic waves. We investigate motion of the cage, its deformation, and the resultant tension in the mooring lines. Both model predictions are sufficient close to the experimental data, but for the first experiment, the DUT-Flex Sim predictions are slightly more accurate than the ones provided by Aqua-FETM. According to the comparisons, both models can be successfully utilized to the design and analysis of the offshore fish cages provided that an appropriate safety factor is chosen. | 赵云鹏 王欣欣 Jud DECEW Igor TSUKROV 白晓东 毕春伟 | 2015 | China Ocean Engineering2015，29，3： | 5 |
| 2 | Drag on Hydroid-Fouled Nets – An Experimental Approach显示文摘The present study investigated the drag increase on aquaculture nets due to biofouling of the colonial hydroid Ectopleura larynx. It had two main parts: firstly the growth characteristics of E. larynx were investigated by use of field tests at a Norwegian aquaculture site; secondly the hydrodynamic drag on the fouled twines was studied in a towing tank by using fabricated models of net twines with artificial hydroid fouling. In the field tests, the growth of the hydroids was first measured after three weeks of immersion and then again after six weeks. During this interval, the density of hydroids and the thickness of the hydroid stem were almost constant(1.4 hydroids/mm and 0.29 mm, respectively), while the average length of the hydroids increased from 6.4 to 11.2 mm. The hydroid length followed a Rayleigh distribution, while the thickness was normal(Gaussian) distributed. Replicas of twines with three different levels of hydroid growth were made(1.5 hydroids/mm twine, hydroid length 9 mm, 16 mm and 20 mm), and the drag on these twines was measured at different towing velocities(0.1 to 1.4 m/s) and with different twine configurations. For the twine with the shortest hydroids(9 mm), the drag was from 1.5 times(Re=4000) to 2.2 times(Re=1000) the drag on a clean twine. For the longest hydroids(21 mm), the drag was 2 times and 3.8 times, respectively. | Pl LADER David W. FREDRIKSSON Jana GUENTHER Zsolt VOLENT Nina BLOCHER David KRISTIANSEN Lars GANSEL Jud DECEW | 2015 | China Ocean Engineering2015，29，3： | 1 |
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