双向流滴灌灌水器消能机理PIV试验研究
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摘要
滴灌灌水器流道内部水流运动特性与其水力性能密切相关。该文以双向流滴灌灌水器为研究对象,利用粒子成像测速技术(PIV, particle image velocimetry),分别在30 kPa和130 kPa进口压力条件下,观测灌水器流道内部水流运动特征,获取水流流速和湍流强度等水流运动的分布特性,据此分析了流道的消能机理。结果表明:流道内正向和反向水流形成了双S型主流流动及漩涡流动,水流流动呈现为紊流状态;灌水器进口压力的增加并未显著改变流道水流运动特征及漩涡的分布位置;在流道分流处、转角处及混掺处水流流速变化较为剧烈,为流道主要消能位置;随着进口压力升高,正向和反向水流在混掺前与混掺后的流速差均显著增加,有利于提高流道对冲、混掺消能效果;反向水流在混掺前与混掺后的流速差均高于正向水流,且随着压力升高,两者的差距显著增加,说明反向水流在混掺消能过程中的作用大于正向水流;流道湍流强度大部分在0.1-0.4之间,紊流程度较高,有利于在流道中消除多余能量,以确保灌水器出流量稳定。研究结果从微观角度揭示了双向流滴灌灌水器在不同进口压力下的消能机理,可与宏观试验及数值模拟相结合,为进一步优化流道结构及提高双向流滴灌灌水器水力性能奠定理论基础。
The hydraulic performance of drip irrigation emitter is closely related to fluid field characteristics. Hence, to design emitters with high hydraulic performance, it is necessary to have a comprehensive understanding of the flow regime within the flow channel. Base on this, the PIV system had been built to realize the visual observation of fluid field in this paper.Some micro-characteristics, such as the flow velocity distribution an d turbulence intensity distribution, were measured under 30 kPa and 130 kPa. The results showed that the flow in the bidirectio nal flow channel moved along a double S-shaped path, with some whirlpool regions. During this process, the flow velocity chang ed very rapidly and energy exchanges continuously occurred to dissipate the pressured energy. Especially, a strong mixing phenom enon occurred at the mixing area, which resulted in a large loss of the local pressure. This was the main different form compare d to labyrinth emitter with respect to energy dissipation. The mixing extent increased significantly as a function of pressure increa sing. The backward flow played a more important role than the forward flow in mixing process. Therefore, much more attention s hould be paid to the flow velocity of forward flow in order to enhance the mixing extent of flow channel. It was also observed th at the turbulence intensity of the bidirectional flow channel mostly ranged from 0.1 to 0.4. Higher turbulence intensity indicated more energy consumption in the flow channel. The findings can provide a theoretical foundation for optimizing the structure and promote the hydraulic performance of the bidirectional flow channel emitter.
The hydraulic performance of drip irrigation emitter is closely related to fluid field characteristics. Hence, to design emitters with high hydraulic performance, it is necessary to have a comprehensive understanding of the flow regime within the flow channel. Base on this, the PIV system had been built to realize the visual observation of fluid field in this paper.Some micro-characteristics, such as the flow velocity distribution an d turbulence intensity distribution, were measured under 30 kPa and 130 kPa. The results showed that the flow in the bidirectio nal flow channel moved along a double S-shaped path, with some whirlpool regions. During this process, the flow velocity chang ed very rapidly and energy exchanges continuously occurred to dissipate the pressured energy. Especially, a strong mixing phenom enon occurred at the mixing area, which resulted in a large loss of the local pressure. This was the main different form compare d to labyrinth emitter with respect to energy dissipation. The mixing extent increased significantly as a function of pressure increa sing. The backward flow played a more important role than the forward flow in mixing process. Therefore, much more attention s hould be paid to the flow velocity of forward flow in order to enhance the mixing extent of flow channel. It was also observed th at the turbulence intensity of the bidirectional flow channel mostly ranged from 0.1 to 0.4. Higher turbulence intensity indicated more energy consumption in the flow channel. The findings can provide a theoretical foundation for optimizing the structure and promote the hydraulic performance of the bidirectional flow channel emitter.
引文
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[9]喻黎明,谭弘,邹小艳,等.基于CFD-DEM耦合的迷宫流道水沙运动数值模拟[J].农业机械学报,2016,47(8):65-71.YU Li-ming,TAN Hong,ZOU Xiao-yan,et al.Numerical simulation of water and sediment flow in labyrinth channel based on CFD-DEM[J].Transactions of the Chinese Socity for Agricultural Machinery,2016,47(8):65-71.
[10]魏正英,唐一平,温聚英,等.灌水器微细流道水沙两相流分析和微PIV及抗堵实验研究[J].农业工程学报,2008,24(6):1-9.WEI Zheng-ying,TANG Yi-ping,WEN Ju-ying,et al.Two-phase flow analysis and experimental investigation of micro-PIV and anti-clogging for micro-channels of emitter[J].Transactions of the Chinese Society of Agricultural Engineering,2008,24(6):1-9.
[11]魏正英,赵万华,唐一平,等.滴灌灌水器迷宫流道主航道抗堵设计方法研究[J].农业工程学报,2005,21(6):1-7.WEI Zheng-ying,ZHAO Wan-hua,TANG Yi-ping,et al.Anti-clogging design method for the labyrinth path of drip irrigation emitters[J].Transactions of the Chinese Society of Agricultural Engineering,2005,21(6):1-7.
[12]GONCALO S,NUNO L,VIRIATO S.Micro-PIV and CFD characterization of flows in a micro-channel:Velocity profiles,surface roughness and Poiseuille numbers[J].International Journal of Heat and Fluid Flow,2008,29:1211-1220.
[13]喻黎明,梅其勇.迷宫流道灌水器抗堵塞设计与PIV试验[J].农业机械学报,2014,45(9):155-160.YU Li-ming,MEI Qi-yong.Anti-clogging design and experimental investigation of PIV for labyrinth-channel emitters of drip irrigation emitters[J].Transactions of the Chinese Society for Agricultural Machinery,2014,45(9):155-160.
[14]金文,张鸿雁.灌水器内流道流场Micro-PIV试验分析[J].农业工程学报,2010,26(2):12-17.JIN Wen,ZHANG Hong-yan.Micro-PIV analysis of flow fields in flow channel of emitter[J].Transactions of the Chinese Society of Agricultural Engineering,2010,26(2):12-17.
[15]郭霖,白丹,王新端,等.双向对冲流滴灌灌水器水力性能与消能效果[J].农业工程学报,2016,32(17):77-82.GUO Lin,BAI Dan,WANG Xin-duan,et al.Hydraulic performance and energy dissipation effect of two-ways mixed flow emitter in drip irrigation[J].Transactions of the Chinese Society of Agricultural Engineering,2016,32(17):77-82.
[16]郭霖,白丹,王新端,等.双向对冲流灌水器水力性能和消能机理模拟与验证[J].农业工程学报,2017,33(14):100-107.GUO Lin,BAI Dan,WANG Xin-duan,et al.Numerical simulation and verification of hydraulic performance and energy dissipation mechanism of two-ways mixed flow emitter[J].Transactions of the Chinese Society of Agricultural Engineering,2017,33(14):100-107.
[17]李云开,刘世荣,杨培岭,等.滴头锯齿型迷宫流道消能特性的流体动力学分析[J].农业机械学报,2007,38(12):49-52.LI Yun-kai,LIU Shi-rong,YANG Pei-ling,et al.Hydrokinetics analysis on the pressure losses in sawtooth-labyrinth path drip irrigation emitters[J].Transactions of the Chinese Society for Agricultural Machinery,2007,38(12):49-52.
[18]王文娥,王福军.迷宫滴头水力特性非定常数值模拟研究[J].水利学报,2010,41(3):332-337.WANG Wen-e,WANG Fu-jun.Numerical simulation of unsteady flow in labyrinth emitters of drip irrigation system[J].Journal of Hydraulic Engineering,2010,41(3):332-337.
[19]胡江,王兴奎,杨胜发,等.不同工作原理的PIV在紊流测量中的适应性分析[J].水力发电学报,2013,32(1):181-186.HU Jiang,WANG Xing-kui,YANG Sheng-fa,et al.Adaptability of PIV based on different working principle to turbulence measurements[J].Journal of Hydroelectric Engineering,2013,32(1):181-186.
[2]郑超,吴普特,张林,等.动态水压下迷宫流道水流运动特性研究[J].农业机械学报,2015,46(9):167-172.ZHENG Chao,WU Pu-te,ZHANG Lin,et al.Flow characteristics in labyrinth channel under dynamic water pressure[J].Transactions of the Chinese Society of Agricultural Machinery,2015,46(9):167-172.
[3]魏青松,史玉升,芦刚,等.内镶式滴灌带绕流流道水力性能研究[J].农业工程学报,2006,22(10):83-87.WEI Qing-song,SHI Yu-sheng,LU Gang,et al.Hydraulic performances of the round-flow channel in an in-line drip-tape[J].Transactions of the Chinese Society of Agricultural Engineering,2006,22(10):83-87.
[4]MADRAMOOTOO C A,MORRISON J.Advances and challenges with micro-irrigation[J].Irrigation and Drainage,2013,62(3):255-261.
[5]苑伟静,魏正英,楚华丽,等.分流式灌水器结构优化设计与试验[J].农业工程学报,2014,30(17):117-124.YUAN Wei-jing,WEI Zheng-ying,CHU Hua-li,et al.Optimal design and experiment for divided-flow emitter in drip irrigation[J].Transactions of the Chinese Society of Agricultural Engineering,2014,30(17):117-124.
[6]田济扬,白丹,于福亮,等.基于Fluent软件的滴灌双向流道灌水器水力性能数值模拟[J].农业工程学报,2014,30(20):65-71.TIAN Ji-yang,BAI Dan,YU Fu-liang,et al.Numerical simulation of hydraulic performance on bidirectional flow channel of drip irrigation emitter using Fluent[J].Transactions of the Chinese Society of Agricultural Engineering,2014,30(20):65-71.
[7]WEI Q S,SHI Y S,DONG W C,et al.Study on hydraulic performance of drip emitters by computational fluid dynamics[J].Agricultural Water Management,2006,84(1):130-136.
[8]FENG J,LI Y K,WANG W N,et al.Effect of optimization forms of flow path on emitter hydraulic and anti-clogging performance in drip irrigation system[J].Irrigation Science,2018,36(1):37-47.
[9]喻黎明,谭弘,邹小艳,等.基于CFD-DEM耦合的迷宫流道水沙运动数值模拟[J].农业机械学报,2016,47(8):65-71.YU Li-ming,TAN Hong,ZOU Xiao-yan,et al.Numerical simulation of water and sediment flow in labyrinth channel based on CFD-DEM[J].Transactions of the Chinese Socity for Agricultural Machinery,2016,47(8):65-71.
[10]魏正英,唐一平,温聚英,等.灌水器微细流道水沙两相流分析和微PIV及抗堵实验研究[J].农业工程学报,2008,24(6):1-9.WEI Zheng-ying,TANG Yi-ping,WEN Ju-ying,et al.Two-phase flow analysis and experimental investigation of micro-PIV and anti-clogging for micro-channels of emitter[J].Transactions of the Chinese Society of Agricultural Engineering,2008,24(6):1-9.
[11]魏正英,赵万华,唐一平,等.滴灌灌水器迷宫流道主航道抗堵设计方法研究[J].农业工程学报,2005,21(6):1-7.WEI Zheng-ying,ZHAO Wan-hua,TANG Yi-ping,et al.Anti-clogging design method for the labyrinth path of drip irrigation emitters[J].Transactions of the Chinese Society of Agricultural Engineering,2005,21(6):1-7.
[12]GONCALO S,NUNO L,VIRIATO S.Micro-PIV and CFD characterization of flows in a micro-channel:Velocity profiles,surface roughness and Poiseuille numbers[J].International Journal of Heat and Fluid Flow,2008,29:1211-1220.
[13]喻黎明,梅其勇.迷宫流道灌水器抗堵塞设计与PIV试验[J].农业机械学报,2014,45(9):155-160.YU Li-ming,MEI Qi-yong.Anti-clogging design and experimental investigation of PIV for labyrinth-channel emitters of drip irrigation emitters[J].Transactions of the Chinese Society for Agricultural Machinery,2014,45(9):155-160.
[14]金文,张鸿雁.灌水器内流道流场Micro-PIV试验分析[J].农业工程学报,2010,26(2):12-17.JIN Wen,ZHANG Hong-yan.Micro-PIV analysis of flow fields in flow channel of emitter[J].Transactions of the Chinese Society of Agricultural Engineering,2010,26(2):12-17.
[15]郭霖,白丹,王新端,等.双向对冲流滴灌灌水器水力性能与消能效果[J].农业工程学报,2016,32(17):77-82.GUO Lin,BAI Dan,WANG Xin-duan,et al.Hydraulic performance and energy dissipation effect of two-ways mixed flow emitter in drip irrigation[J].Transactions of the Chinese Society of Agricultural Engineering,2016,32(17):77-82.
[16]郭霖,白丹,王新端,等.双向对冲流灌水器水力性能和消能机理模拟与验证[J].农业工程学报,2017,33(14):100-107.GUO Lin,BAI Dan,WANG Xin-duan,et al.Numerical simulation and verification of hydraulic performance and energy dissipation mechanism of two-ways mixed flow emitter[J].Transactions of the Chinese Society of Agricultural Engineering,2017,33(14):100-107.
[17]李云开,刘世荣,杨培岭,等.滴头锯齿型迷宫流道消能特性的流体动力学分析[J].农业机械学报,2007,38(12):49-52.LI Yun-kai,LIU Shi-rong,YANG Pei-ling,et al.Hydrokinetics analysis on the pressure losses in sawtooth-labyrinth path drip irrigation emitters[J].Transactions of the Chinese Society for Agricultural Machinery,2007,38(12):49-52.
[18]王文娥,王福军.迷宫滴头水力特性非定常数值模拟研究[J].水利学报,2010,41(3):332-337.WANG Wen-e,WANG Fu-jun.Numerical simulation of unsteady flow in labyrinth emitters of drip irrigation system[J].Journal of Hydraulic Engineering,2010,41(3):332-337.
[19]胡江,王兴奎,杨胜发,等.不同工作原理的PIV在紊流测量中的适应性分析[J].水力发电学报,2013,32(1):181-186.HU Jiang,WANG Xing-kui,YANG Sheng-fa,et al.Adaptability of PIV based on different working principle to turbulence measurements[J].Journal of Hydroelectric Engineering,2013,32(1):181-186.