Study On Numerical Simulation Of Flow Field Effect Of Artificial Fish Reef

Artificial reef possess the effect of bait and the aggregation of fishes,are depleted,it could effectively mitigate the effect of the situation of the depleted resources of the Offshore Marine fishery.The effects of bait and the aggregation of fishes of artificial reef are implemented through the effect of flow field and ecology.Now the studies of artificial reef are mainly focus on the characteristic distribution of the effect of flow field around reef and the effect of reefs' flow field effected by the different materials and structural properties of monomer fish reefs and double combined fish reefs.There are few studies of flow field around artificial reefs and hydrodynamic characteristics of the combination of more reefs.The characteristics of upwelling current and wake vortex current of combination reefs still didn't get good analytical explanation.Through computational fluid dynamics(CFD)technology,under the function of unsteady flow,the artificial fish reef three-dimensional fluid fields layout which are composed by cube type,trapezoid platform and triangular prism porous hollow monomer fish reefs and combined fish reefs were respectively simulated and obtained.The penetration rate of the three kinds of artificial reef is 20%,six inflow velocities respectively are 0.1?0.2?0.3?0.4?0.6?0.8m/s.The layout of cube type,trapezoid platform and triangular prism porous hollow monomer fish reefs respectively adopt three angles of 30°?45°?90°(0°).The three kinds of spacing for reef layout of combination reefs respectively are 0.5L?1.0L?1.5L.The simulated calculation results showed that the water flow will be elevated when encountering the upstream face of the reef to form upwelling current.Upwelling current promote the water exchange of ocean,the transport effect of nutritive salt and the ocean primary productivity.Under identical simulated condition,the scales and strengths of upwelling and wake vortex region formed when the porous hollow artificial reefs of the same type were placed at 90 degrees reached the maximum,while took second place when the reefs were placed at 30 degrees,the scales and strengths of upwelling and wake vortex region become the minimum.The flow field effect generated by cube type fish reefs in case of monomer fish reef is optimal.The analysis of difference in flow fields of Nine-reef Combination of under different kinds of spacing of reef suggested that,the scale and strength of upwelling increased at first then decreased with the increasing spacing,the reef combination at one time of reef spacing can produce better flow field regulating effect,and binary vortices occurred on the reverse sides of the first group of reefs of cube type and triangular prism reef combinations,while only one vortex occurred in trapezoid platform reef combination.The texture of binary vortices is stabilized,it promotes the water exchange of ocean and the transport effect of nutritive salt,this will benefit the aggregation of fish bait which fishes needed,and promote the scale of shoal of fish.Under identical working condition,cube type and triangular prism reef combinations can give better play to the fish collection and bait effects as well as the environmental remediation function of the reefs.Under different working condition,the scales and strengths of upwelling and wake vortex around Nine-Reef Combination of cube type as to the flow speed increases.Vortex occurred in the interior and back zone of the Nine-Reef Combination when the flow speed is 0.1m/s,the speed of vortex is low and the texture of vortex is instability,this not helpful to the aggregation of fishes.As to the increase of flow velocity,vortex fully developed,the texture of vortex becomes stabilized,and this is more helpful to the aggregation of fishes.