Numerical Simulation Study On The Flow Field Character And Stability Of Artificial Reefs

Marine fishery resources are great wealth to the human society, while the decline of fishery resources and the imbalance of marine ecological environment have gradually become global problems. Oceanic ranch has become new means of developing marine fishery resources, and artificial reefs are one of the important components of oceanic ranch. Artificial reefs change the local flow field, producing upwelling and vortex flow. Upwelling affects the distribution of nutrients and vortex flow provides fish with habitats full of vortex. Artificial reefs gather the fish, with breeding site.This paper reviewed the study of the effect of reefs on flow field and reefs stability under the current and wave and so on. Most of the studies take the height of upwelling and the length of vortex flow as indices. But researches of 3-D effects of reefs on flow field are lacking. And there is rare study on the influence of wave on the stability of reefs.Based on the CFD software, a numerical channel was built to simulate the flow field around the artificial reef. The simulation results were compared with experiments, which proved the numerical channel’s effectiveness. A wave tank was built to simulate the spread process of linear regular wave, the wave’s spread and transformation process over a submerged breakwater terrain and the force on the cylinder. The simulation results were compared with the experiments, which proved the effectiveness of numerical wave tank.The effects of several factors, these are open-cut ratio, the inlet velocity, the angle and the height-space ratio, on flow field and stability of reefs are studied by using the numerical channel and numerical tank. The results show that:(a) When the open-cut ratio increases, the effect of flow field decreases and the stability declines.(b) When the velocity increases, the upwelling volume increases while vortex volume decreases a little, and the stability declines.(c) When the angle changes, the effect of flow field increases and the anti-slip stability declines.(d) When the height-space ratio decreases, the effect of flow field increases and the stability declines.Taking the artificial reef construction in Tianjin Dashentang waters as background, the tidal numerical model was used to simulate the tidal field of Bohai Bay and the tide characteristics of the artificial construction area were obtained. The flow field effect and stability of three types of reefs under the current of 0.5m/s were studied. The result shows that the car-blade reef has the best flow field effect and stability, which provides advice to the artificial reef construction.Based on the wave tank, the paper researched the flow field and stability of reefs under the wave and concluded the change rule of wave surface, flow field and wave force around the reef within a period. The results also show that:(a) When the wave height increases, the velocity and vortex around the reef increase, and the stability declines.(b) When the wave period increases, the velocity and vortex around the reef increase, and the stability declines.