共查询到17条相似文献,搜索用时 125 毫秒
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用基于蒙特卡洛法(Monte Carlo Method,MCM)的DRESOR法(Distributions of Ratios of Energy Scattered by the medium Or Reflected by the boundary surface)求解入射辐射经过介质散射、壁面反射传递后辐射强度随时间变化的瞬态辐射传递方程(Transient RadiativeTransfer Equation,TRTE)问题。通过在系统内计算一单位瞬态入射辐射对介质的DRESOR数分布,就能计算任意时间内入射辐射在系统内时间响应特性,这样有效提高数值方法处理瞬态辐射问题的通用性。并且能够获得高方向分辨率的辐射强度随时间变化的结果,这是目前大多数数值处理方法比较难做到的,显示出了DRESOR法处理瞬态入射辐射问题的能力. 相似文献
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用基于Monte Carlo法的DRESOR法在平行平板系统内具有吸收、无发射介质中研究不同波形入射、壁面反射、介质散射率、光学厚度、各向异性散射等条件对瞬态辐射传递的影响.任意连续波形入射辐射是目前大多数数值方法很难处理的瞬态辐射问题,而DRESOR法通过在系统内计算一单位入射辐射能对介质的DRESOR数分布,就能计算任意连续波形入射辐射条件下高方向分辨率的瞬态辐射强度结果.DRESOR法和Monte Carlo法计算的结果进行了比较验证,两者吻合较好,证明了DRESOR法处理瞬态入射辐射问题的正确性和有效性. 相似文献
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具有漫反射边界一维灰性平行平板介质中辐射传递方程的求解 总被引:3,自引:0,他引:3
本文提出一种基于蒙特卡洛法(Monte Carlo Method, MCM)的新方法在具有漫反射边界一维灰性平行平板介质中求解辐射传递方程(Radiative Transfer Equation,RTE)。该方法能以较高的方向分辨率精确地计算任意点的辐射强度而不需要辐射能量平衡。验证结果显示了该方法的有效性和正确性。并且这种方法具有的一些特点,例如不同辐射源对辐射强度分布贡献的可加性和自动满足边界条件等,使得用该方法更容易处理复杂的辐射换热并行计算问题和复杂的边界条件问题。 相似文献
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温度分布在线实时测量对于燃烧过程优化和污染物控制具有重要意义, 针对以往非接触三维温度分布重建过程的耗时性问题和忽略壁面辐射的不足, 本文提出了一种新的离散重建模型, 用于三维吸收、 发射和散射性高温燃烧介质以及壁面温度的快速联合非接触测量. 该模型以四个CCD(Charge Coupled Device) 为测量传感器, 通过构建辐射逆问题求解方程, 从CCD输出的辐射投影图像重建温度分布. 介质中不同投影方向内的辐射传递过程通过离散传递法来描述, 介质的散射和壁面反射则通过离散坐标法来近似. 离散后计算局部辐射强度的病态方程通过最小二乘余量法来求解, 论文对其计算速度进行了优化. 通过非对称温度分布测量算例分析了该模型的有效性, 讨论了测量噪音、 介质和壁面辐射特性对重建精度的影响, 并与其他方法对比分析了模型的重建速度. 计算结果表明本文提出的离散模型可以有效地用于大型高温燃烧介质和壁面温度分布的联合非接触测量. 即使在有噪声的情况下, 该模型也能获得准确的测量结果, 与其他计算方法相比, 采用改进的最小二乘余量法, 能有效地提高温度分布的重建计算速度. 相似文献
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DRESOR法对平行入射辐射问题的研究 总被引:2,自引:1,他引:1
本采用一种基于蒙特卡洛法(Monte Carlo Method,MCM)求解辐射传递方程(Radiative Transfer Equation, RTE)的快捷、有效的方法-DRESOR法(Distributions of Ratios of Energy Scattered Or Reflected)在一维充满吸收、各向同性散射介质平行平板中,外部有平行入射条件下,求解计算空间点的辐射强度沿空间方向角的分布,而不需要辐射平衡和在空间位置坐标和方向角度坐标上同时离散辐射传递方程进行迭代求解。 相似文献
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求解辐射传递的非结构混合有限体积/有限元法 总被引:1,自引:0,他引:1
本文给了一种适用于任意非结构网格的有限体积/有限元法的混合算法用于求解多维半透明吸收、发射、散射性灰矩形介质内的辐射传递.该方法使用有限元法进行角度离散,有限体积法进行空间离散.与基于辐射传递离散坐标方程的方法不同的是,该方法在迭代求解的过程中,针对每一个空间体元,所有角度方向的辐射强度同时耦合求出.通过两个算例验证了该解法的正确性. 相似文献
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L. Zhang 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(3):420-432
Because the optical plane defined by the incidence and reflection direction at a cylindrical surface has a complicated relation with the local azimuthal angle and zenith angle in the traditional cylindrical coordinate system, it is difficult to deal with the specular reflective boundary condition in the solution of the traditional radiative transfer equation for cylindrical system. In this paper, a new radiative transfer equation for graded index medium in cylindrical system (RTEGCN) is derived based on a newly defined cylindrical coordinate system. In this new cylindrical coordinate system, the optical plane defined by the incidence and reflection direction is just the isometric plane of the local azimuthal angle, which facilitates the RTEGCN in dealing with cylindrical specular reflective boundaries. A least squares finite element method (LSFEM) is developed for solving radiative transfer in single and multi-layer cylindrical medium based on the discrete ordinates form of the RTEGCN. For multi-layer cylindrical medium, a radial basis function interpolation method is proposed to couple the radiative intensity at the interface between two adjacent layers. Various radiative transfer problems in both single and multi-layer cylindrical medium are tested. The results show that the present finite element approach has good accuracy to predict the radiative heat transfer in multi-layer cylindrical medium with Fresnel surfaces. 相似文献
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Huai-Chun Zhou Qiang Cheng Zhi-Feng Huang Cheng He 《Journal of Quantitative Spectroscopy & Radiative Transfer》2007,104(1):99-115
Even though there have been many ways to treat complex anisotropic scattering problems, in most of the cases only the radiation flux or its dimensionless data were provided, and radiative intensity with high directional resolution could merely be seen. In this paper, a comprehensive formulation for the DRESOR method was proposed to deal with the anisotropic scattering, emitting, absorbing, plane-parallel media with different boundary conditions. The method was validated by the data from literature and the integral formulation of RTE. The DRESOR value plays an important role in the DRESOR method, and how it is determined by the anisotropic scattering was demonstrated by some typical results. The intensities with high directional resolution at any point can be given by the present method. It was found that the scattering phase function has little effect on the intensity for thin optical thickness, for example, 0.1. And there is the largest boundary intensity for the medium with the largest forward scattering capability, and the smallest one with the largest backward scattering capability. An attractive phenomenon was observed that the scattering of the medium makes the intensity at boundary can not reach the blackbody emission capability with the same temperature, even if the optical thickness tends to very large. It was also revealed that the scattering of the medium does not mean it cannot alter the magnitude of the energy; actually, stronger scattering causes the energy to have more chance to be absorbed by the medium, and indirectly changes the energy magnitude in the medium. Finally, it is easy to deduce all the associated quantities such as the radiation flux, the incident radiation and the heat source from the intensity, just as done in literature. 相似文献
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L.M. Ruan H. Qi L.H. Liu H.P. Tan 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,86(4):343-352
In this paper the radiative transfer in one-dimensional and two-dimensional cylindrical medium is simulated by the Monte-Carlo (M-C) method. Our results agree with the previous ones very well. It indicates that our cylindrical M-C model is creditable. In this paper, the partition allocation method of radiative heat transfer in participating cylindrical media is presented, in which every sub-domain is isolated by imaginary black wall at certain equivalent temperature and overlaps each other. The stitched results of all sub-domains can predict the results of a whole zone accurately. The partitioned treatment by overlap regions can achieve reasonable result, save memory efficiently, and compute parallel. 相似文献
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Zhi-feng Huang 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(13):1072-1084
Using the intensity with high directional resolution obtained by the Basic-DRESOR method as an initial guess, which is substituted into the integrated radiative transfer equation (IRTE), an iterative algorithm is proposed, called the Iterative-DRESOR method. This method can reduce the error levels of the intensity from several percent using the Basic-DRESOR method to a level of less than 1.0×10−6 with acceptable computation costs. The method is also validated against the exact heat flux in literature in some cases. It further clarifies some uncertain results for the reflectance in a pure, linearly anisotropic scattering medium with specular-diffuse boundaries. The directional distributions of intensity are obviously influenced by the reflecting modes of the boundary, especially in the zone near the boundary. The reflecting mode of an emitting boundary has little effect on the transmittance or reflectance. The reflecting mode of a non-emitting boundary also has little effect on the transmittance, but it obviously influences the reflectance. The difference between the reflectance for specular and diffuse boundaries increases at first, and then decreases, as the optical thickness of the medium increases. The difference will decrease as the scattering albedo of the medium increases, and it is negligible when the medium is pure scattering. The effect of the scattering phase function of the medium on the difference can also not be ignored. The Iterative-DRESOR method is expected to strengthen the capability of the Monte Carlo method to produce accurate results and to validate the results of other methods to solve RTE. 相似文献
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POSITIVE DEFINITE PROBLEM OF ENERGY DENSITY AND RADIATIVE ENERGY FLUX FOR PULSE CYLINDRICAL GRAVITATIONAL WAVE 总被引:2,自引:0,他引:2 下载免费PDF全文
By using the general expressions of energy momentum pseudo-tensor of the cylin-drical gravitational waves (GW) given by Rosen and Virbhadra in Cartesian coor-dinates, the concrete forms of energy density and radiative energy flux of the pulse cylindrical GW are obtained. Their physical properties, suitable range and asymp-totic behaviour are considered. It is found that: For the region in which space radial coordinates to origin are greater than the pulse width of the pulse cylindrical GW, the energy density and radiative energy flux of the outward travelling pulse cylindrical GW propagating along at light-cone are positive definite. However, for the region in which the space radial coordinates are less than the pulse width, there is no guarantee for the positive definite property of the radiative energy flux of the outward travelling wave. Moreover, we show that the asymptotic behaviour of the energy and energy flux densities of the pulse cylindrical GW and that of the Riemann curvature tensor have good self-consistancy in space like, time like and null infinity regions. 相似文献