共查询到20条相似文献,搜索用时 31 毫秒
1.
求解介质内热辐射传递的双向统计蒙特卡罗法 总被引:2,自引:0,他引:2
基于热辐射传输的光路可逆性原理,提出了求解介质内热辐射传递的双向统计蒙特卡罗法(BSMC法)。该方法采用等温等权抽样,利用能束传输路径的可逆关系进行辐射传递的双向统计计算,充分利用了能束跟踪的计算信息。以二维矩形区域内吸收性介质的热辐射传递为例,介绍了BSMC的求解过程,分析了其计算误差。通过数值模拟,从辐射传递因子计算结果的倒易性满足程度与辐射平衡温度场两方面,将BSMC法与传统的蒙特卡罗法(TMC法)进行了比较。结果表明,在相同的计算量下,BSMC法比TMC有更高的模拟精度。 相似文献
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A method is presented for computing the cross-spectral density of a special class of partially coherent fields in which the coherent modes obey an eikonal equation. This method allows for statistical analysis of optical systems based on simple ray tracing. 相似文献
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本文应用分层模型处理较高浓度的弥散体产生的相关散射。计算各层满足单散射条件时的相函数,求得散射几率函数,利用它再计算前向散射的光能分布;对于较大微粒,按衍射理论计算,建立多重散射模型,应用迭代法计算多重散射的光能量分布;测量了不同浓度的玻璃微珠产生的散射光能量功率谱,将其与模拟计算值作比较,并以上限公布函数作有约束的优化处理,计算了D_(32)。文中用图像分析系统对样品作出二值化图,把统计数据与测量结果作了比较。 相似文献
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高功率激光装置中鬼像的模拟-应用实际光线追迹法 总被引:4,自引:0,他引:4
高功率固体激光装置中正常光束的残余反射将形成能量较大的鬼点,它们极易对元器件造成损害,因此对一阶及多阶鬼点的位置作定量分析对高功率激光系统设计是非常必要的。采用将近轴分析与实际光线追迹相结合的分析方法,对神光Ⅲ原型装置进行了一套完整的杂散光分析。首先在近轴条件下对系统中可能产生的一阶至多阶鬼点进行了全面的计算和定位,列出其来源和鬼点较集中的区域,如普克尔盒一个窗口的前表面附近鬼点能量比较集中,然后通过大量的实际光线追迹对这些元件进行重点考察,模拟其表面的能量分布,为如何减小鬼点数目,从而避免鬼点能量造成的损伤提供了详尽的数据参考。 相似文献
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界面声反射模拟是室内复杂声学现象仿真的关键。针对传统声学仿真方法对于周期散射结构存在条件下声场仿真精度较低的问题,本文发展了一种基于迭代散射模型的室内相干声线跟踪法。此方法以经典的相干声线跟踪法为基础,将室内中常见的周期散射结构进行几何形状上的简化处理,然后依据周期散射定理给出声波在界面上的散射方向及能量,并将原始声线迭代分裂为相应的散射子声线,继续对其跟踪处理,此迭代散射模型对周期散射结构上的界面散射现象进行了准确的模拟。数值验证结果表明,本文方法可以有效地在低频段提高室内声场仿真精度,可为具有复杂散射现象的室内仿真提供新思路。 相似文献
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David J. Chappell Gregor Tanner Stefano Giani 《Journal of computational physics》2012,231(18):6181-6191
Dynamical energy analysis was recently introduced as a new method for determining the distribution of mechanical and acoustic wave energy in complex built up structures. The technique interpolates between standard statistical energy analysis and full ray tracing, containing both of these methods as limiting cases. As such the applicability of the method is wide ranging and additionally includes the numerical modelling of problems in optics and more generally of linear wave problems in electromagnetics. In this work we consider a new approach to the method with enhanced versatility, enabling three-dimensional problems to be handled in a straightforward manner. The main challenge is the high dimensionality of the problem: we determine the wave energy density both as a function of the spatial coordinate and momentum (or direction) space. The momentum variables are expressed in separable (polar) coordinates facilitating the use of products of univariate basis expansions. However this is not the case for the spatial argument and so we propose to make use of automated mesh generating routines to both localise the approximation, allowing quadrature costs to be kept moderate, and give versatility in the code for different geometric configurations. 相似文献
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Jens Forssén Stefan Tober Ata Can Corakci Anders Frid Wolfgang Kropp 《Applied Acoustics》2012,73(4):307-311
The sound field in train compartments, treated as a series of connected air cavities, is modelled using statistical energy analysis, SEA. For the case under study, with five cavities in series and the source in the second cavity, a closed-form solution is obtained. An adjusted SEA model is used to predict the rate of spatial decay within a cavity. The SEA model is validated using results from a ray tracing method and from scale model measurements. For the octave bands 500–4000 Hz, good agreement is shown between the results from measurements, the ray tracing and the SEA model, for the two saloons closest to the source cavity (a vestibule). The SEA model was shown to slightly underestimate the rate of spatial decay within a cavity. It is concluded that a reasonable cause is the additional diffusion due to the seating. 相似文献
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A method for ray deflection mapping, moiré deflectometry, which is fully compatible with interferometry, is described and demonstrated by numerous examples, including testing of optical components, visualization of flow, study of transient phenomena, and modulation transfer function analysis. Unlike interferometry, moiré deflectometry is a pure ray tracing technique and, therefore, the analysis of three- dimensional objects is greatly simplified. Although the ray tracing approach to optical systems is much older than wave theory, moiré deflectometry seems to be the first attempt to apply ray tracing methods systematically to optical metrology. Moiré deflectometry is fully quantitative, interferometry-compatible in accuracy and has the additional advantage of tunable sensitivity. 相似文献
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Johann单色器是一种广泛应用的X光单色器,对其能量分辨率已有若干工作进行过分析.对此问题进行了进一步的分析,改进了已有的工作.将计算结果和已有公式的计算结果同时与SHADOW追迹结果进行比较,理论计算与追迹结果有更好地吻合,同时适用范围更大. 相似文献
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Stray light formed by the reflection of photons on inner wall from a bright divertor region can be a serious issue in spectroscopic measurement systems in ITER. In this study, we propose a method to mitigate the influence of stray light using a ray tracing analysis. Usually, a ray tracing simulation requires a time consuming runs. We constructed transfer matrices based on the ray tracing simulation results and used them to demonstrate the influence of stray light. It is shown that the transfer matrix can be used to reconstruct the emission profile by considering the influence of the stray light without any additional ray tracing runs. Mitigation of the stray light in ITER divertor impurity monitor was demonstrated, and a method of prediction of the stray light level for the scrape off layer spectroscopy from divertor region was proposed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The plenoptic camera is a single lens stereo camera which can retrieve the direction of light rays while detecting their intensity distribution. In this paper, to reveal more truths of plenoptic camera imaging, we present the wavefront analysis for the plenoptic camera imaging from the angle of physical optics but not from the ray tracing model of geometric optics.Specifically, the wavefront imaging model of a plenoptic camera is analyzed and simulated by scalar diffraction theory and the depth estimation is redescribed based on physical optics. We simulate a set of raw plenoptic images of an object scene, thereby validating the analysis and derivations and the difference between the imaging analysis methods based on geometric optics and physical optics are also shown in simulations. 相似文献
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Bin Yang Yulai Gao Changdong Zou Qijie Zhai A. S. Abyzov E. Zhuravlev J. W. P. Schmelzer C. Schick 《Applied Physics A: Materials Science & Processing》2011,105(1):189-196
An energy source produced by a TEA CO2 laser operated at 10.6 μm primarily was considered as a key essential in this paper to describe the energy conversion process
in air-breathing laser propulsion in the round. Some secondary factors were ignored when three independent modules, a ray
transmission module, an energy source term module and a fluid mechanics module, were established by a simultaneous laser radiation
transportation equation and a fluid mechanics equation set-up. The incident laser beam after being reflected by the optical
system or transmitted by it was simulated based on a certain geometrical optics method named ray tracing. Thus, coherent superimposition
could be avoided when describing the laser beam focusing process, and so could the solving process of the laser wave equation
at the non-paraxial condition. The calculated results were in good agreement with those of theoretical analysis and experiments. 相似文献
17.
Nevin Selçuk Nimeti Doner 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(3):184-1212
A three-dimensional radiation code based on method of lines (MOL) solution of discrete ordinates method (DOM) coupled with spectral line-based weighted sum of grey gases (SLW) model for radiative heat transfer in non-grey absorbing-emitting media for use in conjunction with a computational fluid dynamics (CFD) code based on the same approach was developed. The code was applied to three test problems: two containing isothermal homogenous/non-homogenous water vapor and one non-isothermal water vapor/carbon dioxide mixture. Predictive accuracy of the code was evaluated by benchmarking its steady-state predictions against accurate results, calculated by ray tracing method with statistical narrow band model, available in the literature. Comparative testing with solutions of other methods is also provided. Comparisons reveal that MOL solution of DOM with SLW model provides accurate solutions for radiative heat fluxes and source terms and can be used with confidence in conjunction with CFD codes based on MOL. 相似文献
18.
Sanjeevareddy Kolkoori Christian Hoehne Jens Prager Michael Rethmeier Marc Kreutzbruck 《Ultrasonics》2014
Quantitative evaluation of ultrasonic C-scan images in homogeneous and layered anisotropic austenitic materials is of general importance for understanding the influence of anisotropy on wave fields during ultrasonic non-destructive testing and evaluation of these materials. In this contribution, a three dimensional ray tracing method is presented for evaluating ultrasonic C-scan images quantitatively in general homogeneous and layered anisotropic austenitic materials. The directivity of the ultrasonic ray source in general homogeneous columnar grained anisotropic austenitic steel material (including layback orientation) is obtained in three dimensions based on Lamb’s reciprocity theorem. As a prerequisite for ray tracing model, the problem of ultrasonic ray energy reflection and transmission coefficients at an interface between (a) isotropic base material and anisotropic austenitic weld material (including layback orientation), (b) two adjacent anisotropic weld metals and (c) anisotropic weld metal and isotropic base material is solved in three dimensions. The influence of columnar grain orientation and layback orientation on ultrasonic C-scan image is quantitatively analyzed in the context of ultrasonic testing of homogeneous and layered austenitic steel materials. The presented quantitative results provide valuable information during ultrasonic characterization of homogeneous and layered anisotropic austenitic steel materials. 相似文献
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The determination of appropriate sound speed profiles in the modeling of near-ground propagation using a ray tracing method is investigated using a ray tracing model which is capable of performing axisymmetric calculations of the sound field around an isolated source. Eigenrays are traced using an iterative procedure which integrates the trajectory equations for each ray launched from the source at a specific direction. The calculation of sound energy losses is made by introducing appropriate coefficients to the equations representing the effect of ground and atmospheric absorption and the interaction with the atmospheric turbulence. The model is validated against analytical and numerical predictions of other methodologies for simple cases, as well as against measurements for nonrefractive atmospheric environments. A systematic investigation for near-ground propagation in downward and upward refractive atmosphere is made using experimental data. Guidelines for the suitable simulation of the wind velocity profile are derived by correlating predictions with measurements. 相似文献