A method for calculating IR emissivity of ship turbulent trailing wake
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摘要: 红外发射率的准确计算是舰船湍流尾迹红外仿真与特性分析的基础。文中以湍流尾迹对Cox-Munk海面坡度概率密度分布的调制模型为基础，结合海面双向反射分布函数，研究了典型环境下舰船湍流尾迹海面红外发射率的计算方法；研究了机载小天顶角、船载大天顶角观测时，舰船湍流尾迹长波8~9 m红外发射率的分布规律，得到了湍流尾迹与海面背景发射率的差别随观测天顶角的增大而增大的结论；仿真计算得到了秋季阴天船载式探测条件下，典型舰船湍流尾迹的红外辐射亮度，并与海上试验数据进行了对比，结果表明湍流尾迹的自发辐射亮度低于海面背景，表现为冷尾迹的特征。Abstract: The accurate calculation of IR emissivity is the basis of modeling and analyzing the ship turbulent trailing wake in IR. Based on Cox-Munk probability distribution function(PDF) of slopes model, and corresponding to bi-directional reflectance distribution(BRDF) function of sea surface, a method for calculating IR emissivity of ship turbulent trailing wake in typical ocean environment was formulated. According to calculation, the emissivity distribution of typical ship turbulent trailing wake in 8-9 m long-IR band for both small zenith angle of airborne detection and big zenith angle of shipborne detection were studied. The results show that the difference of emissivity between turbulent trailing wake and sea background is increased along with the detecting zenith angle. What's more, the radiance of turbulent trailing wake of typical ship is calculated in cloudy autumn shipborne detection condition, which is compared with the sea trial data. The results show that in typical ocean condition, the radiance of turbulent trailing wake is lower than sea background, presenting the characteristic of cold trailing wake.
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Key words:
- turbulent trailing wake /
- infrared emissivity /
- radiance /
- infrared simulation
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