Structural And Layout Optimization Study Of Functional Artificial Reefs

The construction of the accelerated period of the Gulf type,offshore deep-water type,mudflat type modern marine pasture has covered the Yellow and Bohai Seas and other four major sea areas.Among the mudflat type and the integration of space for the characteristics of the "marine ranch and offshore wind power integration development" demonstration area for the innovation-driven modernization of marine ranching has injected inexhaustible power.Coastal mudflats type of marine pasture to shallow water depth,by the wind,waves and currents plus storm surges and other adverse weather effects,the substrate is often more serious scouring and siltation;design of the mudflat substrate scouring,wave performance,good fish collection effect of the wave elimination type artificial reef is particularly important.Offshore wind farms + marine pasture integration ",that is,the core problem of offshore " wind-pastoral integration " is the " spatial integration "," structural integration " and " functional integration " of the components." and "functional integration".The actual construction of offshore structures and artificial reefs not only needs to consider the flow field effect and wave dissipation characteristics,but also the substrate of the sea area where the structures are placed is an important factor.In this paper,the 3D numerical wave tank established by FLOW-3D software is used to test the wave dissipation performance of single row of wave dissipating and deflecting artificial reefs,and the reefs with better wave dissipation performance are equipped with additional flow blockers to investigate the flow field effect of artificial reefs under different flow blocker conditions.In this paper,we propose the design concept of wave-dissipating reefs,which can reduce the impact on coastal currents and sediment siltation,and at the same time,the reefs can play the role of wave dissipation and wave breaking,and have the biological conservation and proliferation functions of ordinary artificial reefs.In order to investigate the effects of different number of reefs,different reef distance per unit and different opening ratios on the wave dissipation performance of wave-deflecting artificial reefs.In this paper,we use computational fluid dynamics(CFD)method and large eddy simulation(LES)to numerically simulate the 3D waves of different reef combinations,and analyze the wave dissipation performance of the reef combinations in terms of wave transmission coefficient,wave reflection coefficient and wave energy dissipation rate,etc.The reef type with better wave dissipation effect is selected and equipped with additional structures such as internal flow barrier,and the upwelling volume and back eddy volume are used to evaluate the flow field effect of the reef alone.The results show that the reefs can be used as a reef.The results show that the wave creation with FLOW-3D software has good stability and continuity.As the number of reefs increases,the relative wavelength multiplier of the reef area increases,and the wave transmission coefficient shows a trend of rapid decrease and then slow decrease,among which the Kt of A4 reef combination is 0.33,and the wave dissipation effect is good.With the increase of unit reef spacing,the wave transmission coefficient shows a trend of increasing and then decreasing until it is stable.As the opening ratio increases,the wave transmission coefficient gradually increases;and for the baffle opening,the permeability of the reef in the wave propagation direction has a significant effect on the change of the wave transmission coefficient.The study shows that the increase of the number of reefs and the decrease of the spacing per unit reef have a significant effect on improving the wave dissipation effect of the reef combination,followed by the baffle opening and the smallest top plate opening.Due to the good stability of the reefs and the performance of the wave dissipation and deflection,the wave dissipation and deflection artificial reefs can adapt to the extreme sea conditions near the shore.In the investigation of the functional integration of "offshore wind farm + marine pasture",the design concept of bottom-proliferating artificial reef is proposed,using a combination of flume experiments and numerical simulations to simulate and compare the changes in sediment flushing and siltation characteristics of two different test groups of wind turbine foundation alone and wind turbine foundation combined with artificial reef.Using the Froude similarity criterion and geometric similarity criterion,the numerical model and the experiment are scaled according to a 100:1 ratio,and the comparison finds that the scouring topography distribution characteristics of the experiment have good similarity with the numerical simulation,among which,in simulating the local topography scouring and siltation changes of the fan foundation alone,it is found that the study shows that: the unidirectional flow under the same hydrological conditions takes longer to reach the scouring and siltation equilibrium compared with the reciprocal flow,and the substrate particle size For the local siltation of the fan foundation,the change is significant,which shows that the scour depth on both sides of the foundation becomes deeper and the siltation height before and after the foundation becomes higher as the particle size decreases.For different flow velocities,the siltation intensity is smaller when the flow velocity is 0.62m/s.The larger the flow velocity is,the longer it takes for the "dynamic bed scouring" to reach the siltation equilibrium,so when actually placing the bottom-propagation artificial reef,it is necessary to consider the substrate size and hydrology of the wind farm area to reasonably lay the bottom-propagation artificial reef.The reefs are placed in different combinations.It is found that the absolute value of scour pit depth around 8 reefs,6reefs and 4 reefs is significantly reduced compared with the absolute value of scour on both sides of the wind turbine foundation alone,and 6 reefs have good adaptability and anti-scour function compared with 8 reefs and 4 reefs.The scouring intensity around the fan foundation is reduced and the scouring area is increased accordingly by the deployment of the reef combination.Comparing the flow velocity clouds of different sections,it can be found that the reef combination has an obvious effect on increasing the back eddy area around the wind turbine foundation,and this study can provide theoretical guidance for the research of "wind-pastoral integration" in the sea.