双层网底鲆鲽网箱耐流特性的数值模拟

摘要

The bottom frame of flounder fish cages with double bottom floors would incline and rotate in current. To ensure the cage bottom structure safety, it is necessary to carry out dynamic analysis for the anti-current characteristics of the cages. Herein, based on the finite element method, a numerical model of the double-bottom cage deformation in current force is developed and then the maximum displacement and pitch of the double bottom are studied. In addition, the calculated results of double-bottom cage are compared with those of single-bottom cage. The simulation results show that the pitches of the upper and lower bottom floors increase along with the increase of flow velocity, and the dip directions of the two bottom floors are just opposite. It is found that when the flow velocity exceeds 93 cm/s in sea, the upper and lower bottom floors of the cage would collide with each other and affect the safety of the cage bottom. Moreover, the displacement of the lower bottom of double-bottom cage is larger than the bottom displacement of the single bottom cage, but the pitch of lower bottom is smaller than the bottom pitch of the single bottom cage, which might be related to the design of the upper bottom of the cage.%双层网底鲆鲽网箱的网底结构在水流作用下会发生倾斜与转动。为确保网底结构的安全，需对其耐流特性进行动力分析。为此，根据有限元法建立了流场中双层网底网箱受力的数学模型，通过计算机数值模拟对双层网底的最大位移与倾角进行研究，并将双层网底的计算结果与单层网底进行对比分析。模拟结果显示，随着流速的增大，上层网底与下层网底的倾角逐渐增加，并且两层网底的倾斜方向恰好相反。研究发现，当实际海区流速超过93 cm／s时，双层网底网箱的上、下两层网底会发生接触碰撞，从而影响网底的稳定。此外，双层网底网箱的下层网底位移要大于单层网底网箱，但其倾角却小于后者，这可能与双层网底网箱的上层网底设计有关。