摘要
为研究方型人工鱼礁体开口比的变化对其水动力特性的影响,利用Fluent软件模拟了边长为3m、开口比为0～0.6之间7种不同方型鱼礁体周围水流场,通过分析水流场变化规律得到了礁体流场效应、阻力系数随开口比的变化情况;基于Morison方程计算了礁体在波流作用下的受力及其抗滑移、抗倾覆安全系数。研究结果表明:当礁体开口比小于0.2时,背涡区范围较大,流场效应明显;随着开口比的增大,礁体产生的上升流范围及竖直向最大速度分量逐渐减小;对于方形开口礁体,阻力系数与开口比的关系式为Cd=0.875φ+1.088(R2=0.963,P<0.01);随着开口比的增大,礁体所受最大波流作用力、抗滑移及抗倾覆安全系数逐渐减小,但礁体不会发生滑移和倾覆,可为实际礁体结构的设计提供参考。
With the improvement of the living standard and the decline of offshore marine fishery resources,the restoring of the ecological environment of the offshore waters,the protection of fishery resources and maintenances of the sustainable development of marine fishery are becoming the urgent tasks at present.Therefore,some scholars proposed the idea of constructing artificial reefs a few decades ago.An artificial reef is one or more objects of natural or human origin deployed purposefully on the seafloor to influence physical,biological,or socioeconomic processes related to living marine resources,and it is the important component of the construction of marine ranching engineering.For the present,the artificial reef is becoming a new increasing point of marine fishery and develops rapidly in the world.Just like other ocean engineering structures,artificial reefs on sea bottom are withstood by the hydrological environment effects responded by the current conditions,and then the perspective of flow field effect and forces stood are nearly correlated with theirs hydrodynamic capability under the ocean field conditions.In order to investigate the change rule of hydrodynamic characteristic of artificial reefs with different opening ratios,the three-dimensional CFD simulation software-FLUENT is applied to study the flow fields of artificial reefs with different opening ratios(0～0.6),whose edges length are all 3 m.Finite Volume Method(FVM)and the SIMPLE Consistent(SIMPLEC)algorithm are used to simulate flow fields of artificial reefs.In this paper,unstructured grid is employed and the grid is refined near the surfaces of reefs.The variation of the drag coefficients and flow field effect of reefs with different opening ratios are obtained through analyzing the variation laws of the flow fields.In addition,the wave-current forces acting on the artificial reefs are calculated based on Morison Equation and the stability of reefs is checked.The following results are then obtained from the simulation:(1)The hydrodynamic characteristics presented significant differences with the different opening ratios and there are a few differences in the stability of artificial reefs with different opening ratios.(2)It has large range of wake vortices region and strong effects of flow field for the reef whose opening ratio is less than 0.2,the wake vortices region behind the reefs aren't obvious when the opening ratio is 0.3～0.6;when the opening ratio is less than 0.6,the range of upwelling current flow as well as the vertical velocity component reduce with the increase of opening ratio.(3)The formula for the drag coefficient of the cubic reef which has openings is:Cd=0.875φ+1.088(R2=0.963,P<0.01).(4)The value of the maximum wave-current force and force moment imposed on reefs,safety factor against slippage and the safety factor against overturning all reduce with the increase of opening ratio,but the reefs won't slip and overturn.The obtained results of this paper have some engineering application values and can provide reference for the design and construction of practical reefs.
引文
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