规模化透水性人工鱼礁阻流效应的数值模拟

为在大尺度海洋模型中合理体现透水性人工鱼礁组合，基于海洋数值模式FVCOM（finite volume community ocean model）模拟了大陈岛拟建人工鱼礁区的水动力情况，比较了阻滞力法、实心礁法和附加底摩擦法在投礁前后的垂向流速、礁顶平面流速、水体向上输运通量和背涡流体积的差异，并根据投礁前后的流速差异，应用经验公式预测了投礁一年后底床泥沙冲淤情况。数值模拟结果表明，礁体组合迎流面产生上升流，礁体背流面流速减小，涨急时刻所形成缓流区长度在礁体组合长度20倍以上，年底床淤积厚度约0.05 m。阻滞力法以减少来流的动态功率密度来模拟礁体对水流的阻滞作用，可有效合理地实现对透水性人工鱼礁流场效应的模拟，避免了实心礁法在透水性鱼礁模拟中过高估计流场效应的问题，也没有附加底摩擦法只适用于低矮礁体的缺陷。阻滞力法可根据透水性礁体的造型、迎流面积、组合个数、布放方式和所处水层而设置各向和各水层的阻流参数，不仅适用于置底型透水性鱼礁，也适用于浮鱼礁。阻滞力法的建立、完善和应用对于今后的人工鱼礁水动力学和生态动力学研究具有重要意义。

Numerical simulation of the flow retarding effect of large-scale permeable artificial reefs

Artificial reefs can be regarded as artificial structures in the sea. There are three methods to reflect bottom structures in large scale ocean models: method of water depth modified treats artificial reefs as impermeable solids and reflects reefs by changing the water depth, which is applicable to impermeable reef mountains; method of bottom friction increased reflects the obstruction of water flow by structures on the seabed by increasing the bottom friction of the model, which is applicable to the simulation of submarine mussel beds and low oyster reefs; method of retarding force simulates the obstruction of water flow in different water layers by adding a retarding force term to the model momentum equation. In order to reasonably represent the permeable artificial reef assemblage in the large-scale ocean model, the hydrodynamic conditions of the proposed artificial reef area on Dachen Island were simulated based on the numerical ocean model FVCOM (finite volume community ocean model), and the differences of vertical flow velocity, reef top plane flow velocity, upward transport flux and back eddy volume before and after reefing were compared among the method of water depth modified, method of bottom friction increased and method of retarding force. Based on the difference of flow velocity before and after reef casting, the empirical formula was applied to predict the bottom bed sediment flushing and siltation one year after reef casting. The numerical simulation results show that the upward flow of the reef combination on the headwater side, the flow velocity of the reef on the backwater side decreases, the length of the slow flow area formed at the time of the rise is more than 20 times the length of the reef combination, and the siltation thickness of the bottom bed at the end of the year is about 0.05 m. The method of retarding force can effectively and reasonably simulate the effect of the flow field of the permeable artificial reef by reducing the dynamic power density of the incoming flow, and avoiding the problem of over-estimating the flow field effect in the simulation of permeable reefs by the method of water depth modified. There is also no defect of the method of bottom friction increased which only applicable to low height reefs. The method of retarding force can set the flow resistance parameters in each direction and water layer according to the shape of the permeable reefs, the area facing the flow, the number of combinations and the deployment method and water layer, which is not only applicable to the bottom-set permeable reefs but also to the floating reefs. The establishment, refinement and application of the method of retarding force are of great significance for future research on the hydrodynamics and ecodynamics of artificial reefs.