| Spillway,as a necessary water release structure for river water conservancy,plays a role in releasing excess water storage of the reservoir.With the gradual complexity of the topography of the construction site of the water conservancy project,most of the water release structures are not suitable for setting,while the side channel spillway is widely used because of its relatively low requirements for excavation volume and its relatively adaptability to such topography.For the side channel spillway,the water overflowing from the reservoir first deflects 90 ° through the side channel control section and then flows down to the discharge chute,forming a transverse spiral flow with strong turbulence in the side channel section.To eliminate its influence,an adjustment section is often set at the downstream side of the side channel section to smooth the flow.However,if the adjustment section does not completely eliminate the transverse spiral flow of the side channel,the effect of the residual spiral flow on the downstream flow field can not be ignored.If a turning section needs to be arranged in the discharge channel due to terrain reasons,the residual spiral flow generated by the turning section of the discharge channel will increase the possibility of pulsation in the discharge water flow,resulting in adverse effects on discharge safety.Numerical simulation is carried out according to the layout direction(forward and reverse),bend angle(0 °,± 5 °,± 10 °,± 14.505 °,± represents the different bend direction),bottom slope of side channel(i=1/250,i=1/50,i=1/25)and slope of the downstream chute turning section in the side channel spillway(select the included angle with the horizontal line: 0 °,5 °,10 °),and so on,and the impact of different chute curves on the spiral flow in the side channel of the spillway is analyzed.The research results are as follows:When the turning section of the discharge channel is arranged in a positive direction,the circulation generated by the bend is consistent with the direction of the incoming horizontal spiral flow,resulting in an increase in the intensity of the annular flow and an increase in turbulence inside the bend.As the turning angle of the bend increases(5 ° →14.505 °),the uniformity of the transverse water surface decreases.The transverse flow velocity at the exit of the bend increases by 36.6% compared to the inlet,and the transverse water surface elevation difference increases by 49.6%;For the reverse layout of the discharge channel turning section,the circulation generated by the bend is opposite to the direction of the incoming horizontal spiral flow.At a small angle(5 °),it is basically an offset situation,and the flow velocity in the bend decreases along the way,approaching 0at the outlet section value;As the turning angle of the bend increases(5 ° → 14.505 °),there is a circulation in the opposite direction to the spiral flow in the side groove inside the bend.The lateral flow velocity at the exit of the bend also increases in the opposite direction(from-0.19m/s to-1.74m/s),and the horizontal water surface uniformity decreases(from 0.948 to 0.863),resulting in a relatively unfavorable flow pattern.In order to avoid the influence of the adjustment section on the horizontal spiral flow discharge intensity of the side groove,the model is adjusted so that there is no adjustment section at the outlet of the side groove section,and it is directly connected to the turning section of the discharge groove.At this time: according to different side channel bottom slopes,reflected from streamline and velocity vector,with the improvement of side channel bottom slope(i=1/250 → i=1/25),the water surface elevation difference on both banks decreases,the water surface of side channel spillway shows a downward trend,and the turbulent energy of each section is significantly strengthened;When the bottom slope of the side channel is raised(i=1/250 → i=1/25),the transverse velocity of each section in the spillway rises by a numerical value(the maximum rise of the outlet section of the side channel is 0.4m/s,the maximum rise of the top section of the curve is 0.32m/s,and the maximum rise of the top section of the curve is 0.35m/s).For different bend slopes,as the bottom slope of the bend increases(0 ° → 10 °),the height difference between the left and right bank water surface lines of the water flow section increases significantly.The horizontal flow velocity of each section changes more strongly along the water depth direction,and the change in horizontal flow velocity gradually weakens along the water flow direction.When the bend slope is 10 °,the average change in horizontal flow velocity of the top section of the bend is 3.47m/s,and the average change in outlet section of the bend is 2.01m/s.When the slope of the bend is 0 °,the average variation of the top section of the bend is 3.54m/s,and the average variation of the exit section of the bend is 2.61m/s.The flow velocity in other directions increases with the increase of the bend slope.The results show that when the circulation generated by the bend is opposite to the direction of the incoming horizontal spiral flow,it can improve the turbulence of the side groove spiral flow,while when it is consistent,it intensifies the turbulence;When the bottom slope of the side groove rises and the slope of the bend becomes gentle,the lateral flow velocity of each section changes sharply,while on the contrary,the lateral flow velocity changes smoothly.In summary,it can be concluded that the turbulent situation of the spiral flow in the side groove can be improved or avoided through the layout of the discharge channel bend. |
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