The spectral nodal method applied to multigroup SN neutron transport problems in One-Dimensional geometry with Fixed–Source

2018 ◽  
Vol 105 ◽  
pp. 106-113 ◽  
Author(s):  
Amaury Muñoz Oliva ◽  
Hermes Alves Filho ◽  
Davi José Martins e Silva ◽  
Carlos Rafael García Hernández
Author(s):  
Abdelouahab Kadem

We present a method for solving the two-dimensional equation of transfer. The method can be extended easily to the general linear transport problem. The used technique allows us to reduce the two-dimensional equation to a system of one-dimensional equations. The idea of using the spectral method for searching for solutions to the multidimensional transport problems leads us to a solution for all values of the independant variables, the proposed method reduces the solution of the multidimensional problems into a set of one-dimensional ones that have well-established deterministic solutions. The procedure is based on the development of the angular flux in truncated series of Chebyshev polynomials which will permit us to transform the two-dimensional problem into a set of one-dimensional problems.


2015 ◽  
Vol 11 (8) ◽  
Author(s):  
Carlos Eduardo Souza Ferreira ◽  
Leonardo Ramos Emmendorfer ◽  
João Francisco Prolo Filho

<div><p class="SPabstract">Neste trabalho, uma formulação nodal é proposta para o tratamento de uma classe de problemas de transporte de nêutrons, em geometria cartesiana bidimensional. Através do processo de integração, equações unidimensionais são obtidas, reescrevendo o modelo em termos de quantidades médias. A resolução das equações integradas é feita através de uma versão do método de Ordenadas Discretas Analítico (ADO), onde também são obtidas soluções explicitas, analíticas em termos das variáveis espaciais, através de um código de fácil implementação. Pode-se destacar também como vantagens desta formulação a versatilidade na escolha da quadratura e o baixo custo computacional, uma vez que esquemas iterativos não são necessários tampouco a subdivisão do domínio em células. Para lidar como os termos do contorno que surgem no processo, propõe-se aqui uma representação por constantes, de forma que as equações nas variáveis x e y são tratadas através de um sistema acoplado. Resultados obtidos por esta formulação são apresentados, bem como alguns perfis de fluxos escalares. </p></div><p><strong>Nodal formulation applied to two-dimensional transport problems in Cartesian geometry.</strong></p><p> In this paper, a nodal formulation is proposed for the treatment of a class of neutron transport problems in two-dimensional Cartesian geometry. By the integration process, one-dimensional equations are obtained, rewriting the model in terms of average quantities. The resolution of the integrated equations is made using a version of the Analytical Discrete Ordinate method (ADO), where also be obtained explicit solutions, analytical in terms of spatial variables, through an easy implementation code. It can also highlight as advantages of this formulation the versatility of the quadrature choice and the low computational cost, since iterative schemes are not needed either subdividing the domain in cells. To deal with the contour terms that arise in the process, is proposed here a representation by constants, so that the equations in the variables x and y are treated through a coupled system. Results obtained by this formulation are presented, as well as some profiles of scalar fluxes. </p>


Author(s):  
В.С. РУБАН ◽  
В.И. АЛЕШИН ◽  
Д.С. БЕЗУГЛЫЙ

Рассмотрены уравнения баланса и концентрационных потоков, базирующихся на моделях, позволяющих анализировать одноименные модели реологии течения в канале шнека блока замеса тестомесильной машины. Анализ процесса транспортировки и замеса на основе одномерной модели выявил необходимость использования сигмоидальной функции коэффициента напоропроводности от давления. Переход от одномерных задач к многомерным задачам переноса связан с преобразованием систем уравнений к симметричному виду. Полученные системы уравнений после использования теоремы Грина могут быть решены методом конечных элементов. The balance equation and concentration flows based on the models which make it possible to analyze the eponymous models of flow rheology in the block screw channel in a dough mixing machine has been considered. The analysis of the transportation and batch process based on one-dimensional model proved the necessity to apply sigmoidal coefficient of pressure function. The transition from one-dimensional problems to multidimensional transport problems is associated with the transformation of systems of equations to a symmetric form. The resulting system of equations after using Green’s theorem can be solved by the finite element method.


Author(s):  
Виктор Сергеевич Суров

Описан многомерный узловой метод характеристик, предназначенный для численного расчета упругопластической деформации твердого тела в рамках модели Прандтля-Рейса с уравнением состояния небаротропного типа. В качестве критерия перехода из упругого в пластическое состояние применялось условие текучести Мизеса. Рассмотренный численный метод базируется на координатном расщеплении исходной системы уравнений на ряд одномерных подсистем с последующим их интегрированием с помощью одномерного узлового метода характеристик. Метод использован для расчета ряда одно- и двумерных модельных задач A multidimensional nodal method of characteristics is described. The method is designed to numerically calculate the elastoplastic deformation of a solid body within the Prandtl-Reis model with the non-barotropic state equation. The Mises flow condition was used as a criterion for the transition from an elastic to a plastic state. The considered numerical method is based on the coordinate splitting of the original system of equations into a number of one-dimensional subsystems. Then the resulting equations were integrated using a one-dimensional nodal method of characteristics. The proposed method allows calculating a number of one- and two-dimensional model problems. The results of calculations that employ the multidimensional node method of characteristics were compared with data calculated using the Godunov hybrid method in the framework of a model that did not take into account the contribution of potential elastic compression energy to the total energy of the medium. There are some discrepancies in the calculation results that occur at high speeds of interaction of the aluminum striker with the barrier, exceeding 500 m/s, which are associated with omission of the potential energy due to the elastic compression of the solid within the original Prandtl-Reis model


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