Simulation Of Artificial Reef Sediment Erosion And Silting Based On FLOW-3D

Artificial reef(AR),as a man-made permeable structure,has been widely used in biodiversity conservation and coastal habitat restoration in marine ranching engineering.After the settlement of ARs,the original seabed topography is changed,and the complex hydrodynamic conditions are formed in a certain range around ARs.However,under the constant scour of ocean currents,the sediment around the ARs will undergo suspension,settlement and transport due to the change of the flow field.Artificial reefs will settle and overturn,thus losing their functional characteristics and having a profound impact on the sediment distribution.At present,there are few studies on sediment scouring and silting of artificial reef.The flume experiment is limited by the model scale,flume conditions,sediment properties and other conditions.And the numerical simulation method is rarely able to fully simulate the settling and overturning process of the reef,which to a large extent limits the in-depth study of sediment scouring patterns and scour characteristics around ARs.Therefore,based on FLOW-3D,this study established a three-dimensional numerical model of artificial reef scour process under unidirectional flow conditions.A comparative simulation study was carried out with reference to the indoor scouring test of artificial reef in Pukyong National University,Korea.The feasibility and applicability of the numerical simulation method in this study were verified.At the same time,on the basis of the simulation method,the scouring numerical simulation of artificial reef was carried out on the influence factors such as particle size,flow velocity and the angle of inflow.The influence of the above three factors on the scouring depth,volume,process and suspended sediment concentration around artificial reef was analyzed.The main results were as follows:1)The local scour of artificial reef went through four stages.The scouring depth and scouring morphology in physical experiments were basically consistent with the numerical simulation results,which verified the accuracy of numerical model calculation and the reliability of the scour model condition parameters.2)Within the specific scouring time,the maximum scouring depth of sediment near artificial reef gradually increased with time,and finally tend to be stable.The variation trend was distributed as a quadratic function.3)From the perspective of the local scour effect,among the three influencing factors,the flow velocity had the greatest influence on the scouring volume and depth,followed by the sediment particle size.Compared with other angles,the anti-overturning effect was the best.Compared with other angles of inflow,0° had the best anti-overturning effect.4)In terms of scour characteristics,there was a clear location relationship between the AR and the deepest scour pit.The scour pits around the AR were mainly concentrated at the corners on both sides of the AR bottom.The width of the scour pit was about 0.5 times the width of the reef,and the suspended sediment settled at about 1 times the width of the reef behind the reef,forming accumulation areas like a long tail finally.5)In the combined layout of ARs,the longitudinal spacing of ARs was more than one time the width of reef,which could effectively avoid reef settling and overturning.