双向对冲流灌水器模拟精度综合评价指标

为了评价数值模拟方法对双向对冲流灌水器的计算精度和适用性,设计3种灌水器样机,以试验测得的流量值与PIV测得的流速值为依据,提出评价模拟精度的宏观流量评价指标和微观流速评价指标.从宏观和微观2个角度评价15种数值模拟组合方案与试验结果的吻合程度,并建立综合评价指标模型,采用变异系数法计算2个评价指标的权重系数.结果表明,采用宏观评价指标得到增强壁面函数和RNG k-ε模型的流量偏差率最小,其宏观评价指标值为1.592%;采用微观评价指标得到增强壁面函数和SST k-ω模型的流速偏差率最小,其微观评价指标值为2.095%,2个指标的权重系数分别为0.6和0.4;对其进行综合评价,其中增强壁面函数和SST k-ω模型的综合评价指标值最小,为2.031%;对综合评价模型进一步验证,其验证样机的模拟值与实测值的综合评价指标值为1.307%,证明了灌水器模拟精度综合评价指标的准确性.综合评价指标的建立旨在提供一种分析数值模拟精度的思路.

Comprehensive evaluation indicator of simulation accuracy for two-ways mixed flow emitter

In order to evaluate the calculation accuracy and applicability of the numerical simulation method for two-ways mixed flow emitter, 3 kinds of emitter prototypes were designed. Based on the testing of flow rate and fluid velocity by experiment and Particle Image Velocimetry(PIV)technology, the values of flow rate and fluid velocity were obtained under different pressures. The macroscopic flow rate evaluation indicator and microscopic fluid velocity evaluation indicator were proposed. From the angles of macroscopic and microscopic respectively, the precision about 15 kinds of numerical simulation combination schemes in numerical simulation software was contrasted and analyzed. And the comprehensive evaluation indicator model of different evaluation items was established, the weight coefficients of two evaluation indicators could be calculated by using variation coefficient method from a point of view of objective weighing. The analysis results showed that numerical simulation accuracy of the enhanced wall function was higher and better. Firstly, on the basis of macroscopic evaluation indicator, the numerical simulation value of the enhanced wall function and RNG k-ε physical model could more accurately reflect the real flow rate of emitter, and the value of macroscopic evaluation indicator was 1.592%, which is minimal with the flow rate deviation ratio. Secondly, on the basis of the microscopic evaluation indicator, the fluid velocity deviation ratio using the enhanced wall function and SST k-ω physical model was minimal, and the value of microscopic evaluation indicator was 2.095%. Thirdly, the weight coefficients of macroscopic evaluation indicator and microscopic evaluation indicator were 0.6 and 0.4, respectively. Evaluating two indicators comprehensively, the value of comprehensive evaluation indicator of enhanced wall function and SST k-ω physical model was minimal, which was 2.031%. Further verifying the precision of the comprehensive evaluation indicator model, the comprehensive evaluation indicator between the measure value and numerical simulation value was 1.307%, which proved the accuracy and reliability of the comprehensive evaluation method about numerical si-mulation for two-ways mixed flow emitter. Using macroscopic evaluation indicator and microscopic evaluation indicator, and establishing comprehensive evaluation indicator method can provide an idea for analyzing the numerical simulation accuracy for two-ways mixed flow emitter.