勾头角度与长度对透水丁坝周围水流结构影响的研究OA

Objective The selection of the hook-head permeable spur dike's structural design and body parameters is of great importance for reducing river flow velocity and promoting siltation.Compared to conventional dike designs,the permeable design exhibits enhanced coordination and stability.It effectively overcomes the constraints of solid dike design in complex engineering applications.In addition,it enhances the flow structure sur-rounding the dike,mitigates scouring and siltation,and increases the navigability and flood control capacity of the river.However,research on the effects of body parameters on water flow structure remains limited.This study presents an in-depth investigation of the influence of hook-head angle and length modifications on water flow structure around the dike.The objective is twofold:to provide a theoretical foundation for optimiz-ing body parameter design of the hook-head permeable spur dike in practical projects and to raise the adoption and advancement of this dike type. Methods The research utilized a physical model test with a hook-head permeable spur dike.An ADV was employed to accurately measure the three-dimensional instantaneous flow velocity around the dike under different hook-head angles and lengths.The test apparatus consisted of a lin-ear open channel,in which the permeable holes of the spur dike model were arranged in a double-layer rectangular configuration,characterized by a controlled permeability of 20%.The measurement sections,which numbered five in total,were positioned circumferentially around the spur dike,with 22 measurement points established at each section.Each measurement point underwent continuous measurement for 30 seconds.The collected data underwent processing,during which the theoretical calculation methods were applied to calculate the slow flow rate,flow field uni-formity,turbulence intensity,and turbulence energy around the spur dike.The dimensionless processing was conducted to enhance the intuition of the data.The study further analyzed the specific effects of different body parameters on the flow velocity,slow flow rate,flow field uniformity,turbulence intensity,and the change rule of turbulence energy. Results and Discussions The findings of the research indicated that the hook-angle and length of the permeable spur dike had a substantial im-pact on the flow structure downstream of the dike when integrated with the hook head design.It was observed that as the hook-angle increased,the flow velocity downstream of the dike decreased,while the turbulence intensity and turbulence energy increased.Specifically,when the hook-angle was set at 60°,rather than 30° and 45°,the flow velocity downstream of the dike body decreased by 2.87%and 1.61%,respectively.Simul-taneously,the retardation rate increased by 6.79%and 3.69%,the turbulence intensity increased by 18.95%and 7.58%,and the turbulence energy increased by 27.39%and 5.93%,respectively.Increases in hook-length resulted in decreases in downstream flow velocity and turbulence inten-sity of the dike body.At hook-length D/2,the flow velocity downstream of the dike body decreased by 8.75%and 3.11%,and the turbulence in-tensity decreased by 3.86%and 1.97%,compared to D/4 and D/3.In the downstream reflux zone and transition zone,the flow velocity fluctuation was characterized by an"M"type distribution.The turbulence intensity fluctuation was most intense in the downstream reflux zone,and the varia-tion in the transition zone reached a maximum,which was about 1.7 to 2.3 times that in the reflux zone.The turbulence energy was influenced by the hook-angle,with a maximum observed in the area between the permeable hole and the outer part of the dike head.As the hook-angle in-creased,the peak value gradually deflected toward the right bank.In addition,compared to the conventional permeable straight dike,the average flow velocity in the downstream near-dike area of the hook-head permeable dyke dike decreased by approximately 17%,which substantiated the effectiveness of the hook-head permeable dyke dike in reducing flow velocity. Conclusions The study demonstrated a negative correlation between the downstream flow velocity of the dike and the hook-angle and length.As the hook-angle and length increase,the slowing effect of the spur dike on the water flow becomes more pronounced.In contrast,the flow velocity in the downstream main stream area exhibited an upward trend,indicating that increasing hook-angle and length can enhance river navigability and improve the flow environment.In addition,the turbulence intensity downstream of the dike was found to be positively correlated with the hook-angle and negatively correlated with the hook-length.Therefore,an increase in hook-angle aggravates the disturbance of the water flow by the spur dike,resulting in higher turbulence intensity.An appropriate extension of the hook-length can weaken the turbulence intensity of the wa-ter flow and raise its movement toward a more stable state.