Numerical simulation of effects of artificial reef on hydrodynamics and water exchange in Xiaoyao Bay
Artificial reefs can change the characteristics of tide currents in surrounding waters and provide an ideal living environment for marine organisms.It is necessary to study the effect of artificial reefs on flow field and water exchange capacity after the construction.Xiaoyao Bay is a semi-enclosed bay in the Yellow Sea with regular semi-diurnal tide type.In recent years,site selection and planning layout of artificial reefs have been actively carried out in Xiaoyao Bay.This study used MIKE3 estuarine and coastal model to investigate the effects of artificial reef construction on the hydrodynamic characteristics and water exchange capacity in Xiaoyao Bay.This model used the unstructured triangular mesh and finite volume method.We carried out a series of numerical simulation scenarios in the study area before and after artificial reef construction.The simulated results were in good agreement with the measured data,indicating that the present model was reasonable and reliable.The study results showed that:Firstly,after the construction of artificial reefs the current velocities above the region of artificial reefs increased because of the decrease of water depth,and the current velocities changed slightly in areas far from artificial reefs.The upwelling was generated in inflow area of artificial reefs,and the downwelling was generated in downstream area of artificial reefs respectively,where the upwelling effect in bottom layer was more significant than that in surface layer.Secondly,from the horizontal scale,the construction of artificial reefs caused significant changes of flow field in the local areas,the velocities in inflow and downstream areas near artificial reefs decreased,and the velocities of two sides of the mainstream axis increased due to the block of artificial reefs,and the alternately slow and fast distribution for flow velocities occurred around reef stacks.During fast flood tide,the maximum increase of surface velocity was 0.14 m·s-1 and the maximum increase of bottom velocity was 0.049 m·s-1,while the velocity changes for surface and bottom layers were similar.The velocity changes for surface and bottom layers caused by the construction of artificial reefs were mainly distributed within the domain of 2 km near the reef placement area,and the flow velocity changed slightly in sea areas far away from the artificial reef area.Thirdly,the water half-exchange periods in the top and middle parts of Xiaoyao Bay were shortened after artificial reef construction,the sea water exchange capacity changed slightly near the mouth of the bay,and the overall sea water exchange capacity was slightly enhanced,indicating that artificial reef construction had less impact on water exchange capacity in Xiaoyao Bay.The study results can provide theoretical guidance for the reasonable layout and construction of artificial reef engineering.In generally,the construction of artificial reefs will not only affect the tidal motion and water exchange characteristics in the coastal waters,but also affect the process of sediment transport,and change the state of siltation of seabed on the bottom of artificial reefs,or even the evolution of the seabed geomorphology and offshore topography.Therefore,sediment erosion and deposition near the artificial reefs should be studied in future work to ensure the stable state of artificial reef after its construction in Xiaoyao Bay.
万方数据
维普
