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激光作用下半透明介质光热信息模拟及反问题研究

Photothermal Signal Simulation Forlaser-irradiated Semi-transparent Media and Its Inverse Problems

【作者】 张彪

【导师】 阮立明; 齐宏;

【作者基本信息】 哈尔滨工业大学 , 工程热物理, 2014, 博士

【摘要】 半透明材料被广泛应用于各个领域,对其光学和红外特性的研究受到了国内外学者们的共同关注。典型的半透明介质有:水、冰、空气、玻璃、树脂、陶瓷、生物组织、多孔介质、弥散粒子系等,在激光与半透明介质的光热作用中,需要考虑介质中的热辐射影响。本文从激光作用下半透明介质光热信号模拟的正、反问题两个方面出发,对稳态辐射传输问题、瞬态时域辐射传输问题、频域辐射传输问题、辐射导热耦合换热问题、辐射相变耦合换热问题以及辐射反问题等进行了研究,具体包括以下五个方面的工作:1.综述了目前群体智能优化算法的发展,总结了群体智能优化算法的共同特征,介绍了几种常见群体智能优化算法的各自特点,重点阐述了微粒群算法和蚁群算法的思想和实现,并分别对量子微粒群算法、基于网格划分策略蚁群算法和基于概率密度策略蚁群算法提出了改进,通过标准测试函数说明了改进算法在反演精度、计算效率和算法稳定性等方面性能的提升。2.在有限体积法的基础上结合了源项多流法的思想,求解了一维、二维、三维半透明介质在漫射界面下的任意方向辐射强度,利用源项多流法的思想对有限体积法进行了两个方面的改进,即提出了一种更高精度的关联格式和一种不需要进行角度插值来处理多层镜射界面的有限体积法。3.对于辐射导热耦合换热问题,分别基于有效导热系数和辐射源项进行解耦处理,提出了一种求解多孔介质有效导热系数的方法,将基于网格划分的蚁群算法引入到辐射导热耦合换热反问题当中,通过测量边界上的温度和辐射热流反演了辐射导热耦合换热问题的散射系数、吸收系数分布、不均匀介质的界面位置;对于辐射相变耦合换热问题利用有限体积法分别求解了基于焓法能量方程和辐射传递方程,对有限体积法模型进行了对比验证,对控制方程进行了无量纲化处理,反演了斯蒂芬数和导热辐射参数。4.对于瞬态辐射传输问题,分别利用了有限体积法求解了时域和频域的辐射传递方程,将计算结果与蒙特卡洛法和间断有限元法进行了对比,分别将基于网格划分策略的蚁群算法和基于概率密度策略的蚁群算法引入到瞬态辐射反问题当中,通过测量边界上的透、反射信号反演了半透明介质的衰减系数、散射反照率、散射不对称因子等物性参数。5.基于时间相关单光子计数技术,搭建了脉冲激光作用下半透明介质透、反射信号测量的实验平台,并对测量系统进行了标定,通过制作已知物性的固态仿体,分析了本测量系统的误差来源与可靠性,最后利用该实验台对生物组织分别进行了离体测量和在体测量,利用实测的透反射信号反演了半透明介质的吸收和约化散射系数。

【Abstract】 Semi-transparent material has been widely used in various fields. Research on the optical and infrared properties of semi-transparent materials received a common concern by domestic and foreign scholars. Typical semi-transparent media are: water, ice, air, glass, resin, ceramic, biological tissue, porous media, dispersed particles, and so on. The effects of radiative heat transfer always need to be considered in the study of photothermal interaction between laser and semi-transparent media. From the direct and inverse problem of photothermal signal simulation for laser-irradiated semi-transparent media, the present dissertation focuses on steady radiative heat transfer, transient radiative transfer, frequency-domain radiative transfer, coupled radiative and conductive heat transfer, coupled radiative and phase-change heat transfer and inverse radiative heat transfer. The specific work of this thesis includes the following five aspects:1. The current development of Swarm Intelligence optimization algorithms was reviewed in this thesis, in which the common features of swarm intelligence optimization algorithm were also summarized. Moreover, the characteristics of several common algorithms were introduced, respectively. Particle Swarm Optimization (PSO) and Ant Colony Optimization (ACO) were discussed on the theory and realization. Meanwhile, the improvement of Quantum-behaved Particle Swarm Optimization (QPSO), Grid-based Ant Colony Optimization (GACO) and PDF-based Ant Colony Optimization (PACO) were given here. Through several standard test functions, the performances in accuracy, efficiency and stability of the improved algorithms were proved to have obvious enhancement.2. On the basis of the Finite Volume Method (FVM), combining with the idea of the Multi-Flux Method (MFM), arbitrary directional radiative intensity of multi-dimensional semi-transparent media were solved under diffused boundary condition. Moreover, the FVM was modified from two aspects using the idea of MFM, namely proposing a more precision associated format and putting forward an improved FVM which does not require angle interpolation to handle multi-layer media containing Fresnel interface.3. For the coupled radiative and conductive heat transfer problem, the effective thermal conductivity and radiative source term were used to decouple process. A new method for solving the effective thermal conductivity of porous media was proposed. Then the GACO was introduced to solve the inverse problem of coupled radiative and conductive heat transfer by measuring the temperatures and radiative heat flux on the boundaries. The scattering coefficient, absorption coefficient distribution and interface position were retrieved accurately. For the coupled radiative and phase-change heat transfer, the radiative transfer equation and enthalpy energy equation were both solved by FVM which was verified by results in reference. The control equations were nondimensionalized, and then the Stephen number and conduction to radiation parameter were retrieved successfully at last.4. For transient radiative transfer problem, the time-and frequency-domain transient radiative transfer equation were respectively solved by FVM. The simulated results were compared with those of Monte Carlo Method and Discontinuous Finite Element Method, respectively. The GACO and PACO were introduced to solve inverse problems of time-and frequency-domain transient radiative transfer. Then the physical properties of semi-transparent media such as optical thickness, scattering albedo, absorption coefficient, scattering coefficient and scattering asymmetry factor were retrieved by measuring the transmittance and reflectance on the boundaries.5. Based on Time-Correlated Single Photon Counting (TCSPC) technique, an experimental platform was built to measure the transmittance and reflectance of the semi-transparent media under pulsed laser irradiation. The equipment was calibrated and the experimental system was verified by standard solid imitations whose physical properties were known. Then the error sources and reliability of the measurement system were analyzed. Finally, the reflectance and transmittance of some biological tissues were measured in vitro and vivo. Then the absorption and reduced scattering coefficients were retrieved by utilizing the measured signals.

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