【作者】 陈艳；

【导师】 普小云；

【作者基本信息】 云南大学 ， 光学， 2019， 硕士

【摘要】 液相扩散系数是研究传质过程(传质速率)的重要基础数据,在化工、物理、生物、医学及环保等领域都有着广泛应用。由于理论分析的困难,通常采用实验方法测量液相扩散系数。本文基于液芯柱透镜的焦平面成像原理,用等折射率薄层移动法对室温(25℃)下不同浓度的二甘醇和甘氨酸水溶液的扩散系数进行了实验测量。通过对测量结果的分析,提出了折射率薄层的选取原则。基于光线追迹原理,本论文还对扩散过程进行了数值模拟仿真。论文的主要内容和结果如下:1、基于等折射率薄层移动法,测量了室温下不同浓度的二甘醇水溶液以及不同浓度的甘氨酸水溶液的扩散系数,分析了液体折射率薄层选取对扩散系数测量结果造成的影响。结果表明:只有当选取的液体折射率薄层与所测量的目标溶液折射率相接近时,浓度梯度较小,依据误差函数解得到的扩散系数才稳定(标准偏差σ≤0.03×10-5cm2/s)和准确(相对误差≤3%)。2、基于光线追迹原理,将扩散系数视为常数,用Matlab对不同浓度的二甘醇水溶液以及不同浓度的甘氨酸水溶液扩散过程进行数值仿真。仿真结果表明,只有当选取的折射率薄层接近目标溶液折射率时,浓度梯度较小,仿真图像的“腰”与实验图像的“腰”随时间漂移速率一致。但当折射率薄层偏离目标溶液折射率时,随着浓度梯度的增大,仿真图像与实验图像“腰”随时间漂移速率不再一致,且仿真图像失真。仿真结果进一步证实了用等折射率薄层移动法测量液相扩散系数时折射率薄层的选取原则。3、基于二甘醇和甘氨酸水溶液随浓度变化的实验扩散系数,通过拟合分析分别得到各自的扩散系数随浓度变化的经验公式。采用光线追迹法,对溶液扩散过程进行数值仿真。仿真结果表明,无论选取的折射率薄层接近还是偏离目标溶液折射率,“腰”的漂移速率都与实验一致,仿真图像轮廓也与实验图像较为接近。这一结果再次说明了扩散系数随浓度变化,仅有在浓度梯度小时,扩散系数才能视为常数进行计算。同时也对实验扩散图像的数值仿真提出了一种较为可行的方法。更多还原

【Abstract】 Liquid diffusion coefficient(D)is a fundamental parameter in the study of mass-transfer process,the calculation of mass-transfer rate,which is uesd widely in chemical,physical,biological,medicine,environmental protection and other scientific fields.Experimental method is usually used to measure liquid diffusion coefficient because of the difficulty of theoretical analysis.Based on the focal plane imaging principle of a liquid cylindrical lens,the method of the shift of equivalent refractive index(RI)slice(SERIS)has been used to measure the diffusion coefficients D of diethylene glycol and glycine aqueous solution for different concentrations at room temperature(25℃).By analyzing the measurement results,the selection principle of RI slice is put forward.Based on the ray tracing principle,the diffusion process is simulated.The main research contents and results are as follows:First of all,the diffusion coefficients D of diethylene glycol and glycine aqueous solution for different concentrations were measured at room temperature by the SERIS.At the same time,the influence of selection of RI slice on diffusion coefficient measurement is studied.The measurement results show that concentration gradient is small when the RI slice is close to the RI of the target solution,and the diffusion coefficient is stable(standard deviation σ≤0.03×10-5 cm2/s)and accurate(relative error≤3%)according to the error function solution which regards the diffusion coefficient as a constant.Secondly,based on the ray tracing principle,the diffusion coefficient is regarded as a constant,the diffusion process of diethylene glycol aqueous solution and glycine aqueous solution with different concentrations is simulated numerically by Matlab.Simulation result shows that the"waist"shift of simulation images over time are well consistent with the experimental images when the RI slice is close to the RI of the target solution,which means the concentration gradient is small.However,when the RI slice deviates from the target solution,the"waist"shift of simulation images over time are inconsistent with the experimental images,and the images are distorted with the increase of the concentration gradient.The simulation results further confirm the selection principle of RI slice when the diffusion coefficient is measured by the SERIS.Finally,based on the experimental diffusion coefficients of diethylene glycol and glycine aqueous solution with concentration,the empirical formulas of the diffusion coefficients with concentration is obtained by fitting analysis,the diffusion process is simulated numerically by the ray tracing method.The simulation result shows that the drift rate of the"waist"is consistent with the experiment whether the selected RI slice closes or deviates from the target solution RI,and the contour of simulation image is also close to the experimental image.This result again shows that diffusion coefficient changes with the concentration,only when the concentration gradient is small,the diffusion coefficient can be calculated as a constant.At the same time,a feasible method for numerical simulation of experimental diffusion image is proposed.更多还原