Calculation of Optical Properties of Water Droplets with Equal Volume and Different Aspect Ratios
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摘要: 不同重力场环境中水滴粒子的形状会偏离球形,为了研究水滴粒子非球形化程度对其光学特性的影响,本文计算了不同方向取向下,等体积不同纵横比水滴粒子在3.0~5.0 μm波段的光学特性。研究发现虽然不同纵横比水滴粒子的光学特性在3.0~5.0 μm波段的变化趋势相似,但具体数值仍然明显依赖于水滴粒子的空间取向和偏离球形程度。总体而言,水滴粒子的吸收截面只在方位角θ较小和波长较短时随其纵横比显著变化;而散射截面、不对称因子和散射相函数则在任意方位角和波长下都对水滴粒子的纵横比有较明显的依赖。因此,由于光学特性对水滴粒子的纵横比有较强的依赖性,由水滴粒子所组成的水雾的辐射传输特性会强烈依赖于水滴粒子的形状。
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关键词:
- 水滴粒子 /
- 离散偶极子近似法(discrete-dipole approximation, DDA) /
- 光学特性 /
- 旋转椭球体 /
- 纵横比
Abstract: To study the influence of the asphericity degree on droplet particles optical properties in different gravity fields, the optical properties of water droplet with equal volume and different aspect ratios in the wavelength between 3.0 μm and 5.0 μm were calculated. It was found that although the changing trend of the optical properties of the water droplets with wavelength is very similar, their specific values significantly depend on the spatial orientation and the asphericity degree of water droplets. In general, the absorption cross section of water droplets strongly depends on its aspect ratio only when the azimuth angle θ is small and the wavelength is short. In contrast, the scattering cross section, asymmetry factor, and scattering phase function depend on the aspect ratio of water droplets at any azimuth angle and wavelength. Therefore, because the optical properties are strongly dependent on the aspect ratio of the droplet particles, the radiation transmission properties of fog composed of water droplets should exhibit different results in different gravitational fields.-
Key words:
- water droplet /
- DDA method /
- optical property /
- spheroid /
- aspect ratio
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表 1 粒子模型参数
Table 1. Particle model parameters
ε 2a/d 2b/d 2c/d 1 53.460 53.460 53.460 0.9 57.350 51.615 51.615 0.8 62.035 49.628 49.628 0.7 67.810 47.467 47.467 0.6 75.150 45.090 45.090 0.5 84.864 42.431 42.431 0.4 98.475 39.390 39.390 表 2 水滴的复折射率
Table 2. Refractive index of water droplets
λ/μm n k 3.0 1.371 0.27200 3.2 1.478 0.09240 3.4 1.420 0.01950 3.6 1.385 0.00515 3.8 1.364 0.00340 4.0 1.351 0.00460 4.2 1.342 0.00688 4.4 1.334 0.01030 4.6 1.330 0.01470 4.8 1.330 0.01500 5.0 1.325 0.01240 注:n是复折射率的实部,k是复折射率的虚部
Note: n is the real part of the refractive index, k is the imaginary part of the refractive index -
[1] 陈希庆, 张卫平, 解文彬. 人工喷雾红外遮障技术研究[J]. 红外技术, 2006, 28(13): 606-608. doi: 10.3969/j.issn.1001-8891.2006.10.012CHEN Xiqing, ZHANG Weiping, XIE Wenbin. The research on the technique of artificial fog in camouflage infrared screen[J]. Infrared Technology, 2006, 28(10): 606-608. doi: 10.3969/j.issn.1001-8891.2006.10.012 [2] 杨辉, 刘文清, 杨玉林. 便携式边界层气溶胶监测激光雷达[J]. 红外与激光工程, 2008, 37(1): 64-68. doi: 10.3969/j.issn.1007-2276.2008.01.014YANG Hui, LIU Wenqing, YANG Yulin. Portable PBL aerosol monitoring lidar[J]. Infrared and Laser Engineering, 2008, 37(1): 64-68. doi: 10.3969/j.issn.1007-2276.2008.01.014 [3] 韩永, 饶瑞中, 王英俭. 基于散射法原理的能见度及气溶胶消光特性测量分析[J]. 红外与激光工程, 2008, 37(4): 663-666. doi: 10.3969/j.issn.1007-2276.2008.04.024HAN Yong, RAO Ruizhong, WANG Yinjian. Measurement and analysis of atmospheric visibility and aerosol extinction characteristics based on scattering statistical[J]. Infrared and Laser Engineering, 2008, 37 (4): 663-666. doi: 10.3969/j.issn.1007-2276.2008.04.024 [4] 熊晓伟, 刘上乾. 红外气溶胶烟幕干扰效果的定量评估[J]. 系统工程与电子技术, 2001, 23(2): 39-41. doi: 10.3321/j.issn:1001-506X.2001.02.013XIONG Xiaowei, LIU Shangqian. Effect evaluation on infrared aerosol screening smoke[J]. Systems Engineering and Electronics, 2001, 23(2): 39-41. doi: 10.3321/j.issn:1001-506X.2001.02.013 [5] 耿蕊, 陈芳芳, 吕勇. 激光大气传输透过率影响因素研究[J]. 激光杂志, 2016, 37(12): 13-17. https://www.cnki.com.cn/Article/CJFDTOTAL-JGZZ201612005.htmGENG Rui, CHEN Fangfang, LV Yong. Research on influencing factors of transmittance for laser transmission in atmosphere[J]. Laser Journal, 2016, 37(12): 13-17. https://www.cnki.com.cn/Article/CJFDTOTAL-JGZZ201612005.htm [6] 王玄玉, 殷耀敏, 赵远, 等. 人造水雾粒度测试及红外消光因子计算分析[J]. 中国粉体技术, 2011, 17 (3): 5-7. doi: 10.3969/j.issn.1008-5548.2011.03.002WANG Xuanyu, YIN Yaomin, ZHAO Yun, et al. Testing of granularity of artificial water fog particles and calculation for infrared extinction factors[J]. China Powder Science and Technology, 2011, 17(3): 5-7. doi: 10.3969/j.issn.1008-5548.2011.03.002 [7] 王希影, 齐宏, 王青青, 等. 基于MDA法计算水雾粒子红外隐身粒径[J]. 工程热物理学报, 2011, 32(8): 1389-1392. https://www.cnki.com.cn/Article/CJFDTOTAL-GCRB201108035.htmWANG Xiyin, QI Hong, WANG Qinqin, et al. Numerical simulation of infrared stealth diameter of water fog particles based on the MDA method[J]. Journal of Engineering Thermophysics, 2011, 32(8): 1389-1392. https://www.cnki.com.cn/Article/CJFDTOTAL-GCRB201108035.htm [8] 张学海, 魏合理, 戴聪明, 等. 取向比对椭球气溶胶粒子散射特性的影响[J]. 物理学报, 2015, 64(22): 156-166. https://www.cnki.com.cn/Article/CJFDTOTAL-WLXB201522020.htmZHANG Xuehai, WEI Heli, DAI Congming, et al. Influence of orientation ratio on scattering characteristics of ellipsoid aerosol particles[J]. Acta Physica Sinica, 2015, 64(22): 156-166. https://www.cnki.com.cn/Article/CJFDTOTAL-WLXB201522020.htm [9] BI L, YANG P. High-frequency extinction efficiencies of spheroids: rigorous T-matrix solutions and semi-empirical approximations[J]. Opt. Express, 2014, 22(9): 10270-10293. doi: 10.1364/OE.22.010270 [10] 杜永成, 杨立, 张文勇. 动态细水雾的最佳热辐射消光粒径[J]. 强激光与粒子束, 2013, 25(9): 2413-2417. https://www.cnki.com.cn/Article/CJFDTOTAL-QJGY201309049.htmDU Yongcheng, YANG Li, ZHANG Wenyong. Optimal heat radiation extinction diameter of dynamical fine water sprays[J]. High Power Laser and Particle Beams, 2013, 25(9): 2413-2417. https://www.cnki.com.cn/Article/CJFDTOTAL-QJGY201309049.htm [11] Draine B T. The discrete -dipole approximation and its application to interstellar graphite grains[J]. The Astrophysical Journal, 1988, 333: 848-872. doi: 10.1086/166795 [12] 黄朝军, 刘亚锋, 吴振森. 烟尘簇团粒子光学截面和散射矩阵的数值计算[J]. 物理学报, 2007, 56(7): 4068-4074. doi: 10.3321/j.issn:1000-3290.2007.07.070HUANG Chaojun, LIU Yafeng, WU Zhensen. Numerical calculation of optical cross section and scattering matrix for soot aggregation particles [J]. Acta Physica Sinica, 2007, 56(7): 4068-4074. doi: 10.3321/j.issn:1000-3290.2007.07.070 [13] Yurkin M A, Hoekstra A G. The discrete -dipole-approximation code ADDA: Capabilities and known limitations[J]. Journal of Quantitative Spectroscopy and Radiative Transfer, 2011, 112(13): 2234-2247. doi: 10.1016/j.jqsrt.2011.01.031 [14] Draine B T, Flatau P J. The discrete dipole approximation for periodic targets: I. theory and tests[J]. Journal of the Optical Society of America A, 2008, 28(11): 2693-703. http://www.ncbi.nlm.nih.gov/pubmed/18978846 [15] Draine B T, Flatau P J. Fast near field calculations in the discrete dipole approximation for regular rectilinear grids[J]. Opt Express, 2012, 20(2): 1247-1252. doi: 10.1364/OE.20.001247 [16] Draine B T, Flatau P J. User guide for the discrete dipole approximation code DDSCAT 7.2[J/OL][2012-02-12]. https://arxiv.org/abs/1202.3424. [17] 黄朝军. 烟尘和雾霾气溶胶凝聚粒子光散射及传输特性研究[D]. 西安: 西安电子科技大学, 2018.HUANG Chaojun. Study on Light Scattering and Transmission Characteristics of Soot and Haze Aerosols Aggregation Particles[D]. Xi'an: Xidian University, 2018. [18] Purcell E M, Pennypacker C R. Scattering and absorption of light by nonspherical dielectric grains[J]. Astrophysical Journal, 1973, 186: 705-714. doi: 10.1086/152538 [19] 阮立明, 齐宏, 王圣刚. 采用DDA方法分析非球形粒子辐射特性[J]. 哈尔滨工业大学学报, 2008, 40 (3): 413-418. doi: 10.3321/j.issn:0367-6234.2008.03.018RUAN Liming, QI Hong, WANG Shengang. Analysis of the radiative properties of non-spherical particles by discrete dipole approximation method[J]. Journal of Harbin Institute of Technology, 2008, 40(3): 413-418. doi: 10.3321/j.issn:0367-6234.2008.03.018 [20] Hale G M, Querry M R. Optical constants of water in the 200-nm to 200-μm wavelength region[J]. Applied Optics, 1973, 12(3): 555-563. http://ps.oxfordjournals.org/external-ref?access_num=10.1364/AO.12.000555&link_type=DOI