基于粒子成像瞬态测量技术的雨滴微物理特性及降雨动能研究
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摘要
雨滴微物理特性及降雨动能是揭示降雨物理本质的重要特征量,亦是开展侵蚀定量分析与建立侵蚀量预报模型的基础。采用粒子成像瞬态测量可视化技术观测自然降雨雨滴,结合计算机视觉识别技术解算雨滴微物理特性参数,同时采用虹吸式自记雨量计记录自然降雨降雨强度。研究表明:该次降雨雨滴以中等粒子为主,雨滴直径均值为1.52 mm,降落末速度均值为3.47 m/s,其中直径在1.00~3.00 mm范围内的雨滴占样本总数的87.21%。雨滴直径和降落末速度呈显著的对数关系。基于实测的雨滴微物理特性和降雨强度估算降雨动能,该结果与传统的经验模型估算结果相对误差均值为7.28%。该方法得到的降雨动能较以往的经验模型能更真实的反应雨滴降落过程中的做功大小,为准确计算降雨过程中雨滴所造成的溅蚀量奠定基础。
Microphysical features of raindrop and rainfall energy are the key parameters for study of rainfall physics,which also have great significance in quantitative analysis of soil erosion and in soil erosion prediction model.The existing measurement methods include splash method,immersion method and so on,but most of them have many disadvantages,such as,labor and time consuming,poor real-time response,low precision and so on.Therefore,a new method should be developed urgently.In order to obtain physical properties of raindrops,in this study,the particle imaging transient visual measurement technology,light field and imaging system were designed,image identification,extraction and measurement were investigated,and finally the particle imaging transient visual measurement technology and computer vision identification technology were used to obtain the microphysical features of natural raindrop.The principle of the system could be described as below:a Fresnel lens was installed in the front of the light source.When the lights were passing through the Fresnel lens,the lights from point source would become parallel lights,which would shine on a projecting screen,and then the raindrop would project on the screen during its falling.Specifically,the system consisted of three parts:projection system,image capture system,and image control system.In the image capture system,two cameras were used to capture the raindrop image,one with a fast speed to obtain static image,and the other worked slowly to capture the tailed image.Based on the two images,we calculate the diameter and the fall velocity of raindrops.In order to obtain a clear raindrop image,we must remove the noise in the images.Basically,the image noise removal involved four steps.First,it was statistical filtering; second,the rolling filtering; third,the smooth filtering,and finally,it was the image binarization.Based on the static image and the corresponding tailed image mentioned above,geometric mean value algorithm and outer contour algorithm were used to calculate the diameter and fall velocity of raindrop.In our previous research,we found that the measurement technology had small relative error and it was suitable for the measurement of microphysical features of raindrop.Meanwhile,rainfall intensity was recorded by siphonic pluviograph.The results showed that medium-sized particles were the predominant contributor in the single rainfall.Raindrop diameter and fall velocity in our study were,on average,1.52 mm and 3.47 m/s,respectively.Specifically,the proportion of raindrops with diameter ranged from 1.00 to 3.00 mm was up to 87.21%.Fall velocity was strong logarithmically related to raindrop diameter,and more precisely,fall velocity grew rapidly with an increase in rainfall diameter when the diameter was below 1.5 mm.As the raindrops fatten,the growth rate of fall velocity was reduced.Moreover,rainfall energy calculated in the present study was compared with the classic statistical model,and the relative error was averaged as 7.28%.In all,microphysical features of raindrop and rainfall energy can be measured precisely by the technique in this study,which sets the basis of estimating rainfall splash erosion.
Microphysical features of raindrop and rainfall energy are the key parameters for study of rainfall physics,which also have great significance in quantitative analysis of soil erosion and in soil erosion prediction model.The existing measurement methods include splash method,immersion method and so on,but most of them have many disadvantages,such as,labor and time consuming,poor real-time response,low precision and so on.Therefore,a new method should be developed urgently.In order to obtain physical properties of raindrops,in this study,the particle imaging transient visual measurement technology,light field and imaging system were designed,image identification,extraction and measurement were investigated,and finally the particle imaging transient visual measurement technology and computer vision identification technology were used to obtain the microphysical features of natural raindrop.The principle of the system could be described as below:a Fresnel lens was installed in the front of the light source.When the lights were passing through the Fresnel lens,the lights from point source would become parallel lights,which would shine on a projecting screen,and then the raindrop would project on the screen during its falling.Specifically,the system consisted of three parts:projection system,image capture system,and image control system.In the image capture system,two cameras were used to capture the raindrop image,one with a fast speed to obtain static image,and the other worked slowly to capture the tailed image.Based on the two images,we calculate the diameter and the fall velocity of raindrops.In order to obtain a clear raindrop image,we must remove the noise in the images.Basically,the image noise removal involved four steps.First,it was statistical filtering; second,the rolling filtering; third,the smooth filtering,and finally,it was the image binarization.Based on the static image and the corresponding tailed image mentioned above,geometric mean value algorithm and outer contour algorithm were used to calculate the diameter and fall velocity of raindrop.In our previous research,we found that the measurement technology had small relative error and it was suitable for the measurement of microphysical features of raindrop.Meanwhile,rainfall intensity was recorded by siphonic pluviograph.The results showed that medium-sized particles were the predominant contributor in the single rainfall.Raindrop diameter and fall velocity in our study were,on average,1.52 mm and 3.47 m/s,respectively.Specifically,the proportion of raindrops with diameter ranged from 1.00 to 3.00 mm was up to 87.21%.Fall velocity was strong logarithmically related to raindrop diameter,and more precisely,fall velocity grew rapidly with an increase in rainfall diameter when the diameter was below 1.5 mm.As the raindrops fatten,the growth rate of fall velocity was reduced.Moreover,rainfall energy calculated in the present study was compared with the classic statistical model,and the relative error was averaged as 7.28%.In all,microphysical features of raindrop and rainfall energy can be measured precisely by the technique in this study,which sets the basis of estimating rainfall splash erosion.
引文
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[23]朱磊,曹治国,肖阳,等.基于图像自动识别技术的雨滴谱测量方法[J].计算机应用研究,2015,32(9):2866-2869,2873.Zhu Lei,Cao Zhiguo,Xiao Yang,et al.Automatic measurement method of raindrop size distribution based on computer vision[J].Application Research of Computers,2015,32(9):2866-2869,2873.(in Chinese with English abstract)
[24]伦向敏,侯一民.运用迭代最大熵算法选取最佳图像分割阈值[J].计算机工程与设计,2015,36(5):1265-1268,1289.Lun Xiangmin,Hou Yimin.Optical threshold slection for image segmentation utilizing entropy-max algorithm[J].Computer Engineering and Design,2015,36(5):1265-1268,1289.(in Chinese with English abstract)
[25]郭明航,展小云,赵军,等.雨滴物理特性的粒子成像测量技术研究[J].农业机械学报,2015,46(9):144-150.Guo Minghang,Zhan Xiaoyun,Zhao Jun,et al.Measurement of raindrop physical properties with particle imaging measurement technology[J].Transactions of the Chinese Society for Agricultural Machinery,2015,46(9):144-150.(in Chinese with English abstract)
[26]Marshall J S,Palmer W M.The distribution of raindrops with size[J].Journal of Meteorology,1948(5):165-166.
[27]Hall R L,Calder I R.Drop size modification by forest canopies-measurements using a disdrometer[J].Journal of Geophysical Research-Atmospheres,1993,98(D10):18465-18470.
[28]刘雅君.雨滴下落的收尾速度[J].大学物理,2001,19(4):45-46.Liu Yajun.Terminal velocity of the falling raindrops[J].College Physics,2001,19(4):45-46.(in Chinese with English abstract)
[29]Best A C.Empirical formulate for the terminal velocity of water drops falling through the atmosphere[J].Quarterly Journal of the Royal Meteorologyical Society,1950,76:302-311.
[30]Atlas D,Srivastava R C,Sekhon R S.Doppler radar characteristics of precipitation at vertical incidence[J].Reviews of Geophysics,1973,11(1):1-35.
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[2]巩兴晖,朱德兰,张林,等.基于2DVD的非旋转折射式喷头水滴直径分布规律[J].农业机械学报,2014,45(8):128-148.Gong Xinghui,Zhu Delan,Zhang Lin,et al.Drop size distribution of fixed spray-plate sprinklers with two-dimensional video disdrometer[J].Transactions of the Chinese Society for Agricultural Machinery,2014,45(8):128-148.(in Chinese with English abstract)
[3]Mark W S,Timothy R G,James C A.Tillage effects on soil hydraulic properties in space and time:State of the science[J].Soil and Tillage Research,2008,99(1):4-48.
[4]朱亚乔,刘元波.地面雨滴谱观测技术及特征研究进展[J].地球科学进展,2013,28(6):685-694.Zhu Yaqiao,Liu Yuanbo.Advances in measurement techniques and statistics features of surface raindrop size distribution[J].Advances in Earth Science,2013,28(6):685-694.(in Chinese with English abstract)
[5]付玉,李光录,郑腾辉,等.雨滴击溅对耕作层土壤团聚体粒径分布的影响[J].农业工程学报,2017,33(3):155-160.Fu Yu,Li Guanglu,Zheng Tenghui,et al.Effects of raindrop splash on aggregate particle size distribution of soil plough layer[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2017,33(3):155-160.(in Chinese with English abstract)
[6]赵龙山,梁心蓝,张青峰,等.裸地雨滴溅蚀对坡面微地形的影响与变化特征[J].农业工程学报,2012,28(19):71-77.Zhao Longshan,Liang Xinlan,Zhang Qingfeng,et al.Variation characteristics and effects of splash erosion on slope micro-relief in bare fields[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2012,28(19):71-77.(in Chinese with English abstract)
[7]刘西川,高太长,刘磊,等.雨滴微物理特征研究及测量技术进展[J].地球科学进展,2013,28(11):1217-1226.Liu Xichuan,Gao Taichang,Liu Lei,et al.Advances in microphysical features and measurement techniques of raindrops[J].Advances in Earth Science,2013,28(11):1217-1226.(in Chinese with English abstract)
[8]刘西川,高太长,刘磊,等.基于粒子成像测速技术的雨滴微物理特性研究[J].物理学报,2014,63(2):469-475.Liu Xichuan,Gao Taichang,Liu Lei,et al.Research on microphysical property of raindrops based on particle imaging velocimetry technology[J].Acta Physica Sinica,2014,63(2):469-475.(in Chinese with English abstract)
[9]Szakall M,Diehl K,Mitra S K,et al.A wind tunnel study on the shape,oscillation,and internal circulation of large raindrops with sizes between 2.5 and 7.5 mm[J].Journal of Atmospheric Sciences,2009,66(3):755-765.
[10]刘红燕,雷恒池.基于地面雨滴谱资料分析层状云和对流云降水的特征[J].大气科学,2006(4):693-702.Liu Hongyan,Lei Hengchi.Characteristics of rain from stratiform versus convective cloud based on the surface raindrop data[J].Chinese Journal of Atmospheric Sciences,2006(4):693-702.(in Chinese with English abstract)
[11]Martinez-Mena M,Castillo V,Albaladejo J.Relations between interrill erosion processes and sediment particle size distribution in a semiarid Mediterranean area of SE of Spain[J].Geomorphology,2002,45(3):261-275.
[12]Warrington D N,Mamedov A I,Bhardwag A K,et al.Primary particle size distribution of eroded material affected by degree of aggregate slaking and seal development[J].European Journal of Soil Science,2009,60(1):84-93.
[13]Bentley W A.Studies of raindrops and raindrop phenomena[J].Monthly Weather Review,1904,32:450-456.
[14]李红,任志远,袁寿其,等.高度对色斑法测量雨滴粒径影响的试验研究[J].中国农村水利水电,2006(1):16-17.Li Hong,Ren Zhiyuan,Yuan Shouqi,et al.Experimental study on the height effect on raindrop size in splash method[J].China Rural Water and Hydropower,2006(1):16-17.(in Chinese with English abstract)
[15]舒若杰,高建恩,吴普特,等.基于Corel DRAW软件的小流域模型雨滴测量试验研究[J].农业工程学报,2006,22(11):44-46.Shu Ruojie,Gao Jian’en,Wu Pute,et al.Measurement of raindrop distribution of watershed model using Corel DRAW[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2006,22(11):44-46.(in Chinese with English abstract)
[16]倪际梁,何进,李洪文,等.便携式人工模拟降雨装置的设计与率定[J].农业工程学报,2012,28(24):78-84.Ni Jiliang,He Jin,Li Hongwen,et al.Design and calibration of portable rainfall equipment of artificial simulation[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2012,28(24):78-84.(in Chinese with English abstract)
[17]Clardy D E,Tolberrt C W.Electronic disdrometer[J].Review of Scientific Instruments.1961,32(8):916-920.
[18]Kinnellp I A.Some observations on the Joss-Waldvogel rainfall disdrometer[J].Journal of Applied Meteorology,1976,15(5):499-502.
[19]Sheppardb E,Joe P I.Comparison of raindrop size distribution measurements by a Joss-Waldvogel Disdrometer,a PMS 2DGSpectrometer,and a POSS Doppler Radar[J].Journal of Atmospheric and Oceanic Technology,1994,11:874-887.
[20]Wolff D B,Wolff K R.Rain gauge and disdromrter measurements during the Keys Area Microphysics Project(KAMP)[J].Journal of Atmospheric and Oceanic Technology,2003,20:1460-1477.
[21]万和跃,濮江平,刘思瑶.雨滴谱探测技术发展及应用概述[J].科技创新导报,2015,31:166-167.
[22]韩文霆,曹培,刘文帅.人工模拟降雨系统喷头喷洒雨滴特性测试[J].农业机械学报,2014,45(2):56-61.Han Wenting,Cao Pei,Liu Wenshuai.Raindrop characteristics of sprinklers for artificial rainfall system[J].Transactions of the Chinese Society for Agricultural Machinery,2014,45(12):56-61.(in Chinese with English abstract)
[23]朱磊,曹治国,肖阳,等.基于图像自动识别技术的雨滴谱测量方法[J].计算机应用研究,2015,32(9):2866-2869,2873.Zhu Lei,Cao Zhiguo,Xiao Yang,et al.Automatic measurement method of raindrop size distribution based on computer vision[J].Application Research of Computers,2015,32(9):2866-2869,2873.(in Chinese with English abstract)
[24]伦向敏,侯一民.运用迭代最大熵算法选取最佳图像分割阈值[J].计算机工程与设计,2015,36(5):1265-1268,1289.Lun Xiangmin,Hou Yimin.Optical threshold slection for image segmentation utilizing entropy-max algorithm[J].Computer Engineering and Design,2015,36(5):1265-1268,1289.(in Chinese with English abstract)
[25]郭明航,展小云,赵军,等.雨滴物理特性的粒子成像测量技术研究[J].农业机械学报,2015,46(9):144-150.Guo Minghang,Zhan Xiaoyun,Zhao Jun,et al.Measurement of raindrop physical properties with particle imaging measurement technology[J].Transactions of the Chinese Society for Agricultural Machinery,2015,46(9):144-150.(in Chinese with English abstract)
[26]Marshall J S,Palmer W M.The distribution of raindrops with size[J].Journal of Meteorology,1948(5):165-166.
[27]Hall R L,Calder I R.Drop size modification by forest canopies-measurements using a disdrometer[J].Journal of Geophysical Research-Atmospheres,1993,98(D10):18465-18470.
[28]刘雅君.雨滴下落的收尾速度[J].大学物理,2001,19(4):45-46.Liu Yajun.Terminal velocity of the falling raindrops[J].College Physics,2001,19(4):45-46.(in Chinese with English abstract)
[29]Best A C.Empirical formulate for the terminal velocity of water drops falling through the atmosphere[J].Quarterly Journal of the Royal Meteorologyical Society,1950,76:302-311.
[30]Atlas D,Srivastava R C,Sekhon R S.Doppler radar characteristics of precipitation at vertical incidence[J].Reviews of Geophysics,1973,11(1):1-35.
[31]Uplinger W G.A new formula for raindrop terminal velocity[C]∥20th Radar Meteorology Conference.Boston:American Meteorological Scoiety,1977:389-391.
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