Research On Flow Field Characteristics Of Internal-energy Dissipater

The internal energy dissipater is a new type of internal flow dissipater with sudden expansion and contraction.This paper is based on the preliminary study of the “Study on hydraulic characteristics of internal energy dissipaters in tooth piers” project of the Natural Science Foundation of Shanxi Province.The use of high-precision intelligent pressure sensors and ultrasonic Doppler flow meter for the number of piers 4,area shrinkage ratio 0.5,the tooth pier internal energy dissipater of the five schemes with different tooth heights and spread angles was used to measure the pressure and flow rate at different flow rates(3L/s~18L/s).The numerical simulation method was used to calculate the flow characteristics of the five schemes under high flow rates(20L/s~40L/s).The axial and radial mean flow velocities,axial and radial pulsation intensities of the five kinds of internal pierced energy dissipaters,and the effects of flow parameters on the mean flow velocity and pulsation strength were analyzed and compared.The main research contents and conclusions are as follows:(1)Check the relevant data,analyze the previous research results,select the experimental research program,and carry out model processing and installation and commissioning of test equipment.(2)By comparing the flow velocity distribution in the inlet section with the uniform flow measurement,the measurement results of the flow meter are verified.The integrated error is within ±5%,which can meet the test accuracy requirements.(3)The velocity distribution of the water flow in the test section is relatively clear and is roughly divided into five stages along the longitudinal direction: In the uniform flow section,the velocity distribution is consistent with the theoretical analysis and is an exponential distribution;Before the pier segments,the axial average flow velocity increases sharply at about 0.3D from the inlet of the pier,and the radial average flow velocity also increases correspondingly and points to the axis of the tube;After the water enters the pier segment,the flow rate reaches the maximum value,and the maximum value is about 2.2 times the average flow velocity of the section;Flow through the pier segment,and in the range of 1.2D from the pier section outlet,the axial flow velocity of the central axis is not significantly reduced,and there will be backflow directly behind the pier;In the recovery section,the flow velocity will gradually decrease and return to near uniform flow.(4)With the energy dissipation type of the same pier,with the increase of the flow,the influence of the pier on the water flow is greater;The range of the recirculation zone behind the piers and the reverse flow velocity both increased.When the flow rate was 15 L/s,the average recirculation zone length of each scenario was 0.7 D,and the average maximum reverse flow velocity was 304.4 mm/s.(5)Under the same flow conditions,the piers of different schemes have a certain influence on the flow,in which the impact of a pair of flows on the scheme is greater and the backflow area is stronger.When the flow rate reaches 15L/s,the length of the recirculation zone behind the tooth pier is about 0.9D,and the maximum reverse flow velocity is 320.18mm/s.The impact of the three schemes on the incoming flow is small.When the flow rate reaches 15L/s,the length of the recirculation zone behind the tooth pier is about 0.72 D,and the maximum value of the reverse flow velocity is 282.24mm/s.(6)The fluctuating intensity of the water flow changes strongly in the affected section of the pier.The pulsation strength of the radial axis of the pipeline is less than the pulsation strength of both sides;The pulsation intensity at the position about 0.3D from the entrance to the pier began to increase,and the increase in the pulsation strength near the tube wall in the region where the change of the pier was significant was large,but the increase in the pulsation intensity near the centerline was not significant;The pulsation strength of the exit of the tooth pier,which is the area where the recirculation zone is located,appears obvious fluctuations on each section.The area where the pulsation strength fluctuates greatly is located between the height of the pier and the wall of the tube.The pulsation intensity near the central axis is relatively stable and there is no significant fluctuation along the longitudinal direction.(7)With the same energy dissipation type of piers,the distribution of the pulsation strength of the flow of the flow through the piers is basically the same;However,with the increase of the flow rate,the pulsation strength was strengthened.The pulsation strength on both sides of the tube wall increased greatly,and the center of the tube was not obvious.The maximum value of pulsation strength appeared at the junction of the back flow of the pier and the mainstream.(8)Under the same flow conditions,the pulsation strengths of different tooth piers are different.Among them,the pulsation strength of scheme 1 is smaller,and the pulsation strength of scheme 3 is larger;the areas with larger pulsation strength of each scheme appear at the top edge of the respective piers.(9)On this basis,the flow range was extended to 40 L/s,and numerical calculations and related data analysis and analysis were performed to verify the numerical simulation results by calculating the 15 L/s flow pipe and comparing it with the test.The deviation is within ±4%,and the obtained flow characteristics are basically consistent.(10)In this paper,the measurement and analysis of the flow field of the five kinds of tooth pier internal energy dissipater are the basis of future analysis of the energy dissipation mechanism,and it has a high academic value.