农业工程学报
農業工程學報
농업공정학보
2014年
20期
65-71
,共7页
田济扬%白丹%于福亮%王新端%郭霖
田濟颺%白丹%于福亮%王新耑%郭霖
전제양%백단%우복량%왕신단%곽림
滴灌%数值方法%湍流%灌水器%双向流流道%水力性能
滴灌%數值方法%湍流%灌水器%雙嚮流流道%水力性能
적관%수치방법%단류%관수기%쌍향류류도%수력성능
irrigation%numerical methods%turbulence%emitter%bidirectional flow channel%hydraulic performance
开展滴灌双向流流道数值模拟研究,对提高灌水器研发效率,降低研发成本,分析流道消能机理具有重要意义。通过Fluent软件计算的数值模拟结果和试验数据的对比,重点研究了网格划分和湍流模型选取对模拟精度的影响,以及流道的消能机理。结果表明:当网格划分为0.2 mm,分别采用Realizablek-ε模型与标准k-ω模型模拟时,模拟值与实测值的相关系数均高于0.998,数值模拟精度和计算效率较高;且流道的进口压力越大,反向水流与正向水流的比值越大,流态指数越小,水力性能越好,特别是在灌水器压力低于0.10 MPa区间,流态指数低于迷宫式流道;从流道的速度矢量图可以明显的看出正向水流与反向水流的分布与混掺过程;分析流道压力分布图,发现流道内压力在正、反向水流混掺后大幅度下降,进一步验证了双向流流道的消能机理与消能效果。
開展滴灌雙嚮流流道數值模擬研究,對提高灌水器研髮效率,降低研髮成本,分析流道消能機理具有重要意義。通過Fluent軟件計算的數值模擬結果和試驗數據的對比,重點研究瞭網格劃分和湍流模型選取對模擬精度的影響,以及流道的消能機理。結果錶明:噹網格劃分為0.2 mm,分彆採用Realizablek-ε模型與標準k-ω模型模擬時,模擬值與實測值的相關繫數均高于0.998,數值模擬精度和計算效率較高;且流道的進口壓力越大,反嚮水流與正嚮水流的比值越大,流態指數越小,水力性能越好,特彆是在灌水器壓力低于0.10 MPa區間,流態指數低于迷宮式流道;從流道的速度矢量圖可以明顯的看齣正嚮水流與反嚮水流的分佈與混摻過程;分析流道壓力分佈圖,髮現流道內壓力在正、反嚮水流混摻後大幅度下降,進一步驗證瞭雙嚮流流道的消能機理與消能效果。
개전적관쌍향류류도수치모의연구,대제고관수기연발효솔,강저연발성본,분석류도소능궤리구유중요의의。통과Fluent연건계산적수치모의결과화시험수거적대비,중점연구료망격화분화단류모형선취대모의정도적영향,이급류도적소능궤리。결과표명:당망격화분위0.2 mm,분별채용Realizablek-ε모형여표준k-ω모형모의시,모의치여실측치적상관계수균고우0.998,수치모의정도화계산효솔교고;차류도적진구압력월대,반향수류여정향수류적비치월대,류태지수월소,수력성능월호,특별시재관수기압력저우0.10 MPa구간,류태지수저우미궁식류도;종류도적속도시량도가이명현적간출정향수류여반향수류적분포여혼참과정;분석류도압력분포도,발현류도내압력재정、반향수류혼참후대폭도하강,진일보험증료쌍향류류도적소능궤리여소능효과。
The hydraulic performance of bidirectional flow channel is better than the hydraulic performance of labyrinth-channel, especially in 0.05-0.10 MPa. So bidirectional flow emitter can save more energy and the drip irrigation tube can be thinner, it can reduce investment cost and has good application in irrigation. In this study, numerical simulation method was used to accurately and efficiently design various kinds of channels of drip irrigation emitters. In order to improve the efficiency of research and reduce the cost of development, Fluent was used to simulate the bidirectional flow channel and analyze the mechanism of energy dissipation. A channel was designed within a reasonable range of structural parameters to study the grid partition and model selection. The results showed that unstructured grid was suitable for numerical simulation of bidirectional flow channel. Mesh cell sizes of 0.1 mm, 0.2 mm and 0.5 mm were chosen to calculate the flux of the channel under different pressures. Mesh cell size 0.2 mm under the numerical simulation was more accurate and efficient than the ones of 0.1 mm and 0.5 mm. In this paper, five turbulence models including standardk-ε, RNGk-ε, realizablek-ε, standardk-ω and SSTk-ω were compared. The simulating results of realizablek-ε and standardk-ω were better than that from other models. The correlation coefficients between the test results and the simulation values of these two models were 0.998 and 0.998, respectively, in 0.05-0.30 MPa. In 0.10-0.25 MPa, the simulation values were much closer to the test results. So Fluent can be used to simulate the water flow of the bidirectional flow channel and the simulation results had high precision. In addition, by orthogonal design method, we chose three key factors from the structural parameters and arranged nine experimental schemes to study the hydraulic performance and mechanism of energy dissipation. According to the main principle of the bidirectional flow channel, the flux of the backward flow to the flux of the forward flow ratio has important influence on hydraulic performance. For the different kind of channels, when the field angles of V-shape walls were the same, the higher the ratio, the better the hydraulic performance. For the same kind of channel, the higher the pressure was, the higher the ratio and the better the hydraulic performance. The flow index of the third experimental scheme was the smallest among the nine experimental schemes. The velocity vector distribution of the third experimental scheme showed flow conditions in bidirectional flow channel including high velocity area, low velocity area and mixing area of the forward flow and the backward flow. The pressure profile of the third experimental scheme showed the change of pressure in bidirectional flow channel, which further validated the mechanism of energy dissipation and the effect of energy dissipation. When the inlet pressure was 0.05 MPa, the pressure changed from about 0.042 MPa to 0.026 MPa at the mixing area of the forward flow and the backward flow, pressure drop was quite obvious. These conclusions can be directly used to improve the structure of bidirectional flow channel and promote the effect of energy dissipation.