Characteristic methods are widely known to be very accurate approaches to the solution of numerical transport problems. These methods are most often used for neutron transport applications (i.e., lattice physics calculations) where spatial cells are of intermediate optical thickness [O(1) to 0(100) mean free paths, depending on the energy group] and materials are not exceptionally highly scattering (scattering ratios < 0.999). There has been interest in using characteristic methods for radiative transfer applications, which often involve very optically thick and diffusive regions. Previous work has involved analyses of families of Cartesian geometry characteristic methods in optically thick and diffusive regions. There is a significant body of work in the Russian literature on curvilinear geometry characteristic methods, but very few analyses of their behavior in thick diffusive regions have been published. In this paper we develop two new members of a family of one-dimensional spherical geometry characteristic methods-the method of tubes. These new methods are similar to traditional slab geometry characteristics methods in that they utilize spatial moments of the transport equation in each cell to generate the data used in the representation of the total source (scattering source plus external source). We present the results of an asymptotic analysis of these methods to predict their behavior in the thick diffusion limit, and we compare these predictions with numerical results from several test problems. This analysis shows that the constant source (step) method behaves very poorly in the diffusion limit, but that the linear source method is accurate in this physical regime.
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机译:万向节密封件-具有细长的球形密封表面,该表面可滑入较厚的外表面,以提供防尘密封等。AB DE4036616A两根轴(1、2)通过万向节连接,一根轴(2)装有一个球面联轴器(3)在第二轴的外球面内移动。第二根轴具有细长的球形密封表面(8),该表面在较厚的外表面内滑动。相互交叉的球形密封表面提供了有限的灰尘等进入的密封。密封唇(8a,9)密封了壳体的作用。优势-改进了对万向接头的保护,将砂砾损坏的风险降至最低。 AN 91194459 TI用于转速测量的脉冲环-倾斜的计数器部分沿环的外围压出,与传感器单元相互作用以确定速度和方向