Numerical modeling of interaction between steady flow and pile-net structures using a one-way coupling model

Abstract

Increasing demand for seafood drives the aquaculture industry to new-generation offshore aquaculture systems with high production efficiency. As a healthy, sustainable and ecological aquaculture pattern, the pile-net enclosure has been widely applied in the aquaculture industry in China. The flow field distribution and hydrodynamic characteristics are of great importance for the welfare of farmed fish and the structure safety. This paper proposes a one-way fluid-structure coupling model to examine the flow interaction with the pile-net structures. A series of physical experiments are conducted to verify the accuracy of the numerical model. Then, different configurations, pile-net at different locations and distance between upstream and downstream pile-nets are selected to estimate their influence on the flow field and hydrodynamic characteristics of pile-net structures. Results show that the net intensifies the velocity attenuation and reduces the velocity in front of the structure. The variation of vortices is affected by the downstream pile-net and the distance between twines and piles. The wake width behind the pile is barely affected by intersection angles between pile-net and flow, but the wake width behind the net increases slightly with the increase of intersection angles between pile-net and flow. Increasing the intersection angles between pile-net and flow aggravates the attenuation of downstream velocity. The computed force decreases with decreasing intersection angles between pile-net and flow. Double rows of the pile-net intensify the upstream and downstream velocity attenuation. The distance between pile-nets has little influence on downstream flow velocity. The interaction between upstream and downstream pile-net structures weakens with the increase of the distance between upstream and downstream pile-nets. With this understanding, the proposed model can be further used to assess the hydrodynamic performance of the pile-net enclosure and the large offshore aquaculture platform under steady flows, oscillating flows and waves.