弧底梯形渠道无喉道量水槽水位流量关系数值模拟

Numerical Simulation on Discharge Relation of Arc-Based Trapezoidal Canal and Cut-throat Flow Measurement Flume

目前为适应我国多数渠道断面方式和灌区管理方式,开发研制新型量水配套设施对灌区节水起着至关重要的作用。利用Fluent 6.3大型流体力学数值仿真软件,结合有限体积法、RNG k-ε湍流模型和VOF模型,在不同渠道底坡上对不同量水槽水位流量进行数值模拟试验研究。结果表明:(1)量水槽流态上游水面平稳属于缓流,量水槽槽内水流为急流,可知由缓流过度到急流必然会发生临界流,量水槽沿程弗劳德数可知量水槽喉口附近扩散段内产生临界流;(2)弧底梯形渠道无喉道量水槽具有较好的水位流量关系,渠道收缩比ε与渠道比降i对形成单值稳定的水位流量关系有较大的影响,随着渠道尺寸增大同时收缩比ε减小,量水槽水位流量逐渐在较大的底坡范围内形成统一的水位流量关系。(3)流量系数与量水槽宽和收缩比具有较好的线性关系,同时流量系数随R,H、ε的增大而变大,回归分析建立的量水槽流量公式,测流公式平均误差值小于5%,说明弧底梯形渠道无喉道量水槽测流是可行的,满足明渠测流要求。研究成果对灌区渠道量水槽的设计优化提供了一定的参考和建议。

To adapt to the irrigation management methods and section form of most channels, developing new facilities plays a vital role in wate-saving irrigation. According to finite volume method, RNG k e turbulence model and VOF model, we make the amount of three-dimensional numerical simulation experimental study on arc based trapezoidal cut-throat flow measurement flume by Fluent 6.3. By comparing the simulation results with the theoreti cal value, the result is well matched. This proofs that the fluent software for numerical simulation methods of free surface turbulence characteristics is reliable. On this basis, we carry out the amount of comprehensive simulation experimental Study on water level and discharge in different open channel bottom slopes. The re suits show that ： （1） the upstream of the flow measurement flume is slow steady stream and the internal flow is jet stream, so the critical flow is bound to happen, Froude numbers along the flow measurement flume show that the critical flow can generate near the diffusing section of the throat; （2） the relationship between upstream water level and discharge is significant, the contraction ratio and bottom slope have great impact on forming the stable relationship between water level and discharge, the contraction ratio decreases with the increases of e, channel size R, H, flow measurement flumes gradually form the unified water level and discharge relationship in the larger scope of the bottom slope; （3） the results have shown that the flow coefficient has a linear relationship with flume width and contraction ratio, and the flow coefficient increases with an increa ses of R, H and ε. The flow equations established by regression analysis show the average error value formu la for measuring flow within 5 %, which explains that arc-based trapezoidal canal and cut lhroat flow meas urement flume meets the requirements of open channel flow measurement. The results will provide some references and recommendations for the application of the irrigation branch canals.