| In recent years,with the attention of the country to the Marine cause,the construction scale of the Marine ranch has gradually expanded.As an important part of Marine pasture construction,artificial reef plays a direct role in Marine pasture construction.Flow field effect and stability are the main evaluation criteria for artificial reef.According to the existing research,there are many factors that affect the flow field effect of artificial fish reef,including the shape and structure of reef body,the current environment,and silt scouring and silting.In the past for the evaluation of the effect of the flow field of artificial reefs,with parameters such as volume,flux measuring upwelling and back vortex strength,but for the different structure and flow Angle of attack reefs less actual stress analysis results in every direction,thus calculate the stress of the different reefs,drag coefficient are calculated and the reef body stability safety coefficient.In order to explore the relationship between stress,flow resistance coefficient,reef opening ratio,flow attack Angle and arrangement of single and combined artificial reef,the flow field effects of square artificial reef with different structures were numerically simulated respectively.The flow field effects were compared by analyzing upwelling and backswirl parameters.The surface integral method and power loss method are used to calculate the resistance and flow resistance coefficient of reef body respectively.By comparing the results of the two methods,it is found that the error of the two methods is about 5.8%,and the verification result is good.For artificial reef monomer,when the opening ratio increases,the resistance of the reef decreases.When the flow is approaching 0°,there is a significant correlation between the opening ratio of the reef and the resistance and flow resistance coefficient,which decrease approximately linearly with the increase of the opening ratio,and the fitting formula of the resistance and resistance coefficient with the opening ratio can be obtained: F=-853.41K-2603.45,Cd=-0.255K-1.311(P<0.05);However,at 15°,30°and 45°,the resistance coefficient of reef increases linearly with the increase of opening ratio,and Cd(30°)>Cd(45°)>Cd(15°);For the artificial reef combination,both the spacing and the Angle of flow attack will affect the flow resistance effect of the reef body.When the Angle of flow attack increases,the distribution of the flow resistance coefficient of the combined reef body and the single reef shows the same law,the maximum flow resistance coefficient is about 1.3 at 0°,and the flow resistance coefficient is about 1.0 at other flow attack angles.If the spacing is too small,the resistance of the reef will be weakened.When the spacing is larger,the resistance of the combined reef will increase.When the spacing is about 1.3L,the resistance coefficient of the combined reef is similar to that of the single reef.For the force of unit reef body inside the combined reef,it is mainly related to the unsheltered area of the reef body.The resistance and flow resistance coefficient of the reef body in front of the reef are close to that of the single reef,while the force of the rear reef is small due to the shielding effect in front.Secondly,the eight-prism artificial reef is taken as the research object,and the resistance and lift force of each reef body under different flow rates are calculated by numerical simulation results,and the relationship between reef force and reef structure and flow attack Angle is analyzed.The results show that in the two kinds of single-layer side-plate artificial reefs,the effect of flow blocking of single-layer side-plate artificial reef is better than that of single-layer side-plate artificial reef.Anti-slip type A <B type,anti-overturning type A >B type;In the two kinds of double-layer side-plate artificial reefs,the effect of flow resistance of the upper vertical side plate type is better than that of the upper inclined side plate type,but the stability(anti-slippage and anti-overturning)is worse than that of the upper inclined side plate type artificial reef.The difference between the two flow rates is less than0.05,the maximum value of type A is 1.8025,and the minimum value of type C is1.5542.C-shaped reef has the best flow resistance at 45° and the largest resistance coefficient at 30°.The stability is best at 0° upflow.D-shaped reef has the best flow resistance at 30°,the largest resistance coefficient at 0°,and the best stability at 0°.Is obtained by the third chapter of square reef body force,the reefs are calculated separately,and the coefficient of stability(resistance to sliding and resistive overturning safety factor),the reef itself structure and flow Angle of attack for the effect on the stability of the rock body,but the actual in the sea,the reef body stability is not only affected by the state of the reef body itself,is receiving more external conditions,Such as tidal current dynamics,sediment erosion and other factors.Therefore,numerical simulation and flume scour test were combined to calculate the scour state of reef with different structures under different flow rates and different substrate particle sizes,and to analyze the influence of reef structure,flow rate and substrate particle size on local scour of reef.The results show that the difference between numerical simulation results and flume scour test results is less than 0.05,which proves that numerical simulation method can be used to simulate local scour of reef.The results show that with the increase of inflow velocity,the maximum depth and width of local scour increase,and the maximum depth of the scour pit at the edge of the reef is larger than that at the center of the reef,and there is sedimentation behind the reef in the center plane. |
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