UPVC斜三通阻力损失及流动特征数值模拟

Numerical Simulation of Resistance Loss and Flow Characteristics on UPVC Slope Tee Pipes

为探讨灌溉管网中斜三通管的水流变化阻力规律,揭示产生阻力损失的诱因,基于标准k-ε湍流模型对DN75等径UPVC斜三通管的阻力损失及流动特征进行了数值模拟研究,并通过文献中的试验结果对标准k-ε模型在分岔流中的模拟效果进行验证。结果表明:标准k-ε模型对分岔流的计算具有较高的精度,与试验结果相比阻力系数最大相对偏差为14.3%;斜三通管主管至斜管、主管至直管的局部阻力系数均与分流比呈较好的二次抛物线关系;流动特征分析表明主管至斜管的阻力损失主要是由离心力作用产生的旋涡和流量变化引起的,在分流比较小时旋涡起主导作用,在分流比较大时流量变化起主导作用;而主管至直管的阻力损失主要由水流发生偏转引起的。

In order to discuss flow resistance of slope tee pipes in irrigation network and reveal the inducement of the loss resistance,based on the standard k-ε turbulence model,the resistance loss and flow characteristics of DN75 UPVC slope tee pipes are simulated and the effectiveness of standard k-ε turbulence model which is used to simulate bifurcating flow is verified.The results show that the calculation of standard k-ε turbulence model on bifurcating flow has higher accuracy and the maximum relative deviation of resistance coefficient is 14.3%.The local resistance coefficient of main branch to slope branch and main branch to straight branch are correlated with the flow ratio by second-order parabola relations.The flow characteristics analysis shows that the resistance loss of main branch to slope branch is mainly caused by the vortex generated by centrifugal force and flow variation,where cortex plays a leading role when the flow ratio is small and flow variation plays a leading role when the flow ration is large.The resistance loss of main branch to straight branch is mainly caused by flow deflection.