【作者】 李伟；

【导师】 张新燕；

【作者基本信息】 西北农林科技大学 ， 工程硕士（专业学位）， 2022， 硕士

【摘要】 针对我国灌区现状,基于水下潜艇外形设计一种流线型量水槽-仿舵型量水槽,使其具有测量精准、适用度高、过流阻力小等特点。通过精确数学表达式和离散外形坐标形值给出的回转体进行线形拟合的方法拟合选取6条流线型曲线,采用数值模拟的方法对构造的不同线型量水槽过槽水流特性参数进行研究,深入了解过槽水流的水力特性,比选确定出量水槽最优体形,构造设计出仿舵型量水槽;在此基础上,对不同收缩比、不同流量下的仿舵型量水槽的水力性能进行实验研究,获得量水槽水力特性;同时基于量纲分析法建立了仿舵型量水槽的流量公式,并进行了流量公式精度分析。主要研究结论如下:(1)研究了量水槽上游收缩段和下游扩散段对量水槽过流水力特性的影响。收缩段对槽内喉口断面产生的临界水深和槽前上游渠道壅水高度具有显著影响,收缩段曲率半径越小,临界水深越大,壅水高度越小;下游扩散段主要影响量水槽下游流态及水头损失,扩散段曲率半径越大,水头损失越小。(2)基于线性拟合选取的流线型曲线设计构造出6种型体量水槽,即EE型、EP型、EA型、NST型、KKS型和CBD型量水槽,模拟研究了量水槽在矩形渠道中的过流特征。试验流量范围内上游弗汝德数均小于0.5,形成平稳缓流;壅水高度均不大于4cm,水头损失低于3.5cm,满足既成渠道的应用要求;计算流量与模拟流量平均误差为2.51%,模拟流量精度较高。综合比较分析试验流量条件下各体形量水槽水力特性发现,KKS仿舵型量水槽在试验流量条件下,流速分布均匀,流态稳定,计算流量与模拟流量平均误差仅为1.73%,模拟流量精度最高;最大水头损失仅为3cm,综合水力性能最优,可作为构造仿舵型量水槽的基本体形。(3)基于最优体形构建喉口收缩比ε为0.45～0.67的仿舵型量水槽,对其水力性能进行研究。结果表明仿舵型量水槽在试验流量和收缩比条件下水流平稳,过流顺畅,上游水流弗汝德数均小于0.5,符合测流规范;槽前壅水高度均值4.2cm,最大值8.7cm,满足规范要求;临界淹没度均值0.83,最大值0.92,表明该槽具有较大的自由出流范围。仿舵型量水槽在试验流量范围内水头损失不超过8cm,且随流量增大而增大,随收缩比增大而减小。收缩比ε为0.45时,水头损失为2.5cm～7.9cm;收缩比ε为0.5～0.67时,水头损失为0.9cm～6cm。通过临界流公式计算流量与实测流量误差分析,在试验条件下其最大误差为4.98%,最小误差为0.36%,平均误差为3.1%,测流精度较高。通过综合分析收缩比对仿舵型量水槽各水力特性产生的影响,发现当收缩比范围为0.5到0.67之间时,仿舵型量水槽的测流精度较高,壅水高度和水头损失较小,水力性能较好。(4)通过量纲分析法建立了仿舵型量水槽流量公式,该公式满足量纲和谐性,与实测流量相比较最大相对误差仅为4.90%,平均误差为2.25%,具有较高的精度,且形式简单,方便使用,可作为仿舵型量水槽流量计算基本公式。更多还原

【Abstract】 In view of the current situation of irrigation area in China,a streamlined measuring flume-rudder-like measuring flume is designed based on the shape of underwater submarine,which has the characteristics of accurate measurement,high applicability and small flow resistance.Six streamline curves were selected by the linear fitting method of the rotary body given by the accurate mathematical expression and the discrete shape coordinate shape value,and the flow characteristic parameters of the constructed different linear flumes were studied by the numerical simulation method,so as to understand the hydraulic characteristics of the flow through the flume in depth,determine the optimal shape of the flume by comparison,and construct and design the rudder-like flume.On this basis,the hydraulic performance of rudder-like flume with different contraction ratios and flow rates was experimentally studied to obtain the hydraulic characteristics of flume.At the same time,the flow formula of rudder-like flume is established based on dimensional analysis method,and the accuracy of the flow formula is analyzed.The main conclusions are as follows :(1)The influence of upstream contraction section and downstream diffusion section on the flow hydraulic characteristics of the flume was studied.The contraction section has obvious influence on the critical depth of throat section and the backwater height of upstream channel.The smaller the curvature radius of contraction section,the larger the critical depth and the smaller the backwater height.The downstream diffusion section mainly affects the downstream flow pattern and head loss of the flume.The larger the curvature radius of the diffusion section,the smaller the head loss.(2)Based on the streamline curve selected by linear fitting,six types of volumetric flume are designed and constructed,namely EE type,EP type,EA type,NST type,KKS type and CBD type.The flow characteristics of the flume in rectangular channel are simulated and studied.The upstream Froude number is less than 0.5 in the test flow range,forming a stable slow flow;backwater height is not more than 4 cm,head loss is less than 3.5 cm,to meet the application requirements of existing channels;the average error between calculated flow and simulated flow is 2.51 %,and the accuracy of simulated flow is high.The hydraulic characteristics of the KKS rudder-like flume under the test flow condition were compared and analyzed.It was found that the velocity distribution of the KKS rudder-like flume was uniform and the flow pattern was stable.The average error between the calculated flow and the simulated flow was only 1.73%,and the accuracy of the simulated flow was the highest.The maximum head loss is only 3 cm,and the comprehensive hydraulic performance is the best,which can be used as the basic shape for constructing rudder-like flume.(3)Based on the optimal shape,a rudder-like flume with throat contraction ratio ε of0.45～0.67 was constructed to study its hydraulic performance.The results show that the flow in the rudder-like flume is stable and smooth under the conditions of test flow rate and contraction ratio,and the Froude number of upstream flow is less than 0.5,which meets the flow measurement standard.the mean backwater height before the trough was 4.2 cm,and the maximum was 8.7 cm,which met the specification requirements;the mean value of critical submergence is 0.83,and the maximum value is 0.92,indicating that the groove has a large free outflow range.The head loss of rudder-like flume is not more than 8 cm within the test flow range,and increases with the increase of flow rate and decreases with the increase of contraction ratio.When the contraction ratio ε is 0.45,the head loss is 2.5cm～7.9cm;when the contraction ratio ε is 0.5～0.67,the head loss is 0.9cm～6cm.The error analysis between the calculated flow rate and the measured flow rate by the critical flow formula shows that under the experimental conditions,the maximum error is 4.98%,the minimum error is 0.36%,and the average error is 3.1%,with high flow measurement accuracy.By comprehensively analyzing the influence of contraction ratio on the hydraulic characteristics of the rudder-like measuring flume,it is found that when the contraction ratio is between 0.5 and 0.67,the flow measurement accuracy of the rudder-like measuring flume is higher,the backwater height and head loss are smaller,and the hydraulic performance is better.(4)The flow formula of rudder-like flume is established by dimensional analysis method.The formula meets the dimensional harmony.Compared with the measured flow,the maximum relative error is only 4.90%,and the average error is 2.25%.It has high accuracy,simple form and convenient use,and can be used as the basic formula for the flow calculation of rudder-like flume.更多还原