基于随机数据元扩张的大气湍流相位屏数值模拟

准确模拟大气湍流相位屏是建立大气湍流数值模型的核心问题。从大气湍流的统计学特性入手,利用大气湍流波前相位结构函数建立了一种新的大气湍流相位屏数值模拟方法,通过随机数据元扩张对大气湍流波前畸变相位分布的尺度随机性和高频分量随机性进行了模拟,并以此为基础通过相位屏近似构建了满足Kolmogorov统计规律的大气湍流数值模型。计算结果表明,随机数据元扩张法生成的相位屏在统计特性上与理论值基本吻合,在低频部分相对于功率谱反演法有明显的提升。同时,随着相位屏网格数的增加,计算结果的高频特性逐渐呈现并逼近理论值。对于由相位屏构建的大气湍流数值模型,在此通过光强闪烁率作为判据进行了验证,结果表明对于弱湍流和中等强度的湍流,模拟结果与理论计算基本相同;对于强湍流则误差较为明显,相对误差最大可达40%。

Atmospheric Turbulence Phase Screen Simulation Based on Random Unit Expansion

Accurately generating the phase screen (PS) is a key step to numerical simulation of the atmospheric turbulence. According to the statistical characteristics of turbulence, a new method called random unit expansion mainly focusing on the scale distribution randomness and small scale phase fluctuation of turbulence is induced by use of the phase structure function (PSF). Based on the PS generated, Kolmogorov atmospheric turbulence model is obtained. Expansion result shows that the phase structure function derived from the simulation is very close to the ideal one. Compared with power spectrum method, performance in low-frequency part is better. Meanwhile, as the grid number of PS increases, characteristic in high frequency part appears obviously and gradually closer to the ideal function. To evaluate the accuracy of the atmospheric turbulence numerical model, scintillation ratio is computed. In the condition of weak and moderate turbulence, the simulated result agrees with theoretical one, while to the strong turbulence, max relative error will be about 40%.