The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Farzad Rahnema - One of the best experts on this subject based on the ideXlab platform.
-
A Decoupled Finite Element Heterogeneous Coarse Mesh Transport Method.
Transactions of the American Nuclear Society, 2020Co-Authors: Scott W Mosher, Farzad RahnemaAbstract:In a recent paper, an original finite element (FE) method was presented for solving eigenvalue transport problems on a Coarse spatial Mesh. The method employed a surface Green's function expansion of the angular flux trial functions, so that heterogeneous Coarse-Meshes could be treated with relative ease. Numerical problems were solved using the multigroup discrete ordinates approximation in one-dimensional (1-D) slab geometry. Unfortunately, difficulties were encountered in finding solutions to the algebraic finite element equations, which led to sizeable angular flux discontinuities at Coarse-Mesh interfaces and significant errors. For this reason, a nonvariational iterative technique was ultimately favored for converging the angular flux distribution, and was used in conjunction with a Rayleigh quotient for converging the eigenvalue. In this paper, a new derivation of finite element equations is presented, which seems to offer a remedy for at least some of the numerical ills that plagued the previous work. First, the equations are derived in terms of a generalized response function expansion. This allows a more efficient response basis to be employed and vastly reduces the overall computational effort without a substantial loss of accuracy. Second, the tight coupling between Coarse-Meshes in the original equations is effectively broken by assuming that anmore » accurate estimate of the flux distribution entering a given Coarse-Mesh is known. With an additional assumption that an accurate eigenvalue estimate is known, an iterative approach to solving these decoupled finite element (DFE) equations is developed. The DFE method has been applied to both 1- and 2-D heterogeneous Coarse-Mesh problems with a far greater degree of success than the original FE method. However, some numerical difficulties remain to be overcome before the new approach can be considered robust.« less
-
COUPLED PHOTON/ELECTRON Coarse Mesh TRANSPORT METHOD FOR DOSE ANALYSIS IN TISSUES
2020Co-Authors: Dingkang Zhang, Farzad RahnemaAbstract:The Coarse Mesh transport (COMET) method for reactor applications has been recently extended to coupled photon/electron transport in heterogeneous phantoms. The method consists of three numerical steps: response function calculations, iterative calculation of interface currents and construction of global dose distribution. In the first step, local problems are solved to obtain the response functions of each unique Coarse Mesh. In the second step, the outgoing interface currents crossing Meshes are calculated iteratively by generating the solutions to the incoming currents. In the last step, the global dose/energy deposition distribution is constructed as a linear superposition of all individual contributions. The comparisons have shown that the COMET method is at least two orders of magnitude faster than the pure Monte Carlo method while the Coarse Mesh results agree very well with the Monte Carlo reference solutions for both homogeneous and heterogeneous phantoms.
-
the adjoint Coarse Mesh transport comet method and reciprocity relation of response coefficients
Journal of Computational and Theoretical Transport, 2016Co-Authors: Dingkang Zhang, Farzad RahnemaAbstract:ABSTRACTAn efficient response-based adjoint radiation transport method is developed and implemented into the Coarse Mesh transport (COMET) code. The numerical implementation of the adjoint COMET consists of three steps: local calculations to compute adjoint response coefficients for each unique Coarse Mesh, global calculations to converge on the core eigenvalue and adjoint partial current moments crossing Coarse Mesh boundaries, and local construction of the adjoint flux distribution within each Coarse Mesh. The reciprocity relations between forward and adjoint response functions are also derived. This unique property can be used to compute adjoint response coefficients without solving the local adjoint problems directly. As a result, the computational effort to generate adjoint response coefficients is completely avoided. The adjoint COMET is tested for two applications: adjoint whole-core eigenvalue calculations in the 3D C5G7 benchmark problem, and local calculations of adjoint surface-to-volume fissio...
-
a Coarse Mesh coupled neutronics and thermal fluids method for prismatic cores
Nuclear Science and Engineering, 2016Co-Authors: Kevin John Connolly, Farzad Rahnema, Alexander J Huning, Srinivas GarimellaAbstract:AbstractA newly developed coupled neutronic—thermal-hydraulic method for prismatic high-temperature gas reactors (HTGRs) is presented with accompanying results for several prismatic core configurations and numerical sensitivity studies. The principal advantage of the new method is the determination of coupled, whole-core temperature and pin power distributions with reduced computational effort over other available codes. The Coarse-Mesh radiation transport method (COMET), which relies solely on radiation transport, is the component of the new method used to compute neutronic parameters. A three-dimensional unit-cell—based thermal fluids solver is used to compute steady-state thermal-hydraulic parameters. For both component methods, no geometric approximations or averaging schemes are necessary. Convergence of the neutronic and thermal-hydraulic components and the coupled method is discussed, and coupled analyses are presented. The calculation of whole-core solutions allows for unique insights not possible...
-
a method for the adaptive selection of angular flux expansion orders in the Coarse Mesh radiation transport comet method
Nuclear Science and Engineering, 2016Co-Authors: Kyle Remley, Farzad RahnemaAbstract:AbstractThis paper presents a formulation for a method for the adaptive selection of angular flux expansion orders for use in Coarse Mesh radiation Transport (COMET) method solutions to whole-core reactor problems. An important aspect of the COMET method is an assumed angular flux expansion on Mesh interfaces. Previously, this expansion was held constant throughout a problem. However, the adaptive method described in this paper chooses the angular flux expansions automatically and allows them to vary between Meshes. To demonstrate the method, a pressurized water reactor benchmark problem with UO2 and mixed oxide fuel assemblies is solved. Three different configurations for different insertions of control rods were considered. For all configurations, the agreement between the standard and adaptive COMET solutions was excellent, with eigenvalue agreement being 2 pcm or less and average pin fission errors never exceeding 0.1%. Increases in computational efficiency by factors of 2 to 2.6 were observed over st...
Dingkang Zhang - One of the best experts on this subject based on the ideXlab platform.
-
COUPLED PHOTON/ELECTRON Coarse Mesh TRANSPORT METHOD FOR DOSE ANALYSIS IN TISSUES
2020Co-Authors: Dingkang Zhang, Farzad RahnemaAbstract:The Coarse Mesh transport (COMET) method for reactor applications has been recently extended to coupled photon/electron transport in heterogeneous phantoms. The method consists of three numerical steps: response function calculations, iterative calculation of interface currents and construction of global dose distribution. In the first step, local problems are solved to obtain the response functions of each unique Coarse Mesh. In the second step, the outgoing interface currents crossing Meshes are calculated iteratively by generating the solutions to the incoming currents. In the last step, the global dose/energy deposition distribution is constructed as a linear superposition of all individual contributions. The comparisons have shown that the COMET method is at least two orders of magnitude faster than the pure Monte Carlo method while the Coarse Mesh results agree very well with the Monte Carlo reference solutions for both homogeneous and heterogeneous phantoms.
-
the adjoint Coarse Mesh transport comet method and reciprocity relation of response coefficients
Journal of Computational and Theoretical Transport, 2016Co-Authors: Dingkang Zhang, Farzad RahnemaAbstract:ABSTRACTAn efficient response-based adjoint radiation transport method is developed and implemented into the Coarse Mesh transport (COMET) code. The numerical implementation of the adjoint COMET consists of three steps: local calculations to compute adjoint response coefficients for each unique Coarse Mesh, global calculations to converge on the core eigenvalue and adjoint partial current moments crossing Coarse Mesh boundaries, and local construction of the adjoint flux distribution within each Coarse Mesh. The reciprocity relations between forward and adjoint response functions are also derived. This unique property can be used to compute adjoint response coefficients without solving the local adjoint problems directly. As a result, the computational effort to generate adjoint response coefficients is completely avoided. The adjoint COMET is tested for two applications: adjoint whole-core eigenvalue calculations in the 3D C5G7 benchmark problem, and local calculations of adjoint surface-to-volume fissio...
-
a whole core Coarse Mesh neutron transport method in 2d cylindrical r theta geometry
Nuclear Engineering and Design, 2013Co-Authors: Dingkang Zhang, Farzad RahnemaAbstract:Abstract In this paper, the hybrid stochastic deterministic Coarse Mesh radiation transport method COMET is extended to 2D cylindrical geometry for whole-core neutronics calculations. To facilitate the extension new functions in cylindrical geometry were developed for expanding the incident angular flux on the ( r , Θ ) surfaces. The new COMET method is tested in a set of simplified pebble bed reactor cores in 2D ( r , Θ ) geometry, consisting of an inner reflector, an annular fuel region, a controlled outer reflector. The comparisons indicate that COMET achieves an accuracy close to the Monte Carlo method (MCNP), with computational efficiency for core calculations that is at least 3 orders of magnitude faster than that of MCNP when a precomputed response library with a 4th order expansion in space and a 2nd order expansion in the polar and azimuthal angles is used.
-
a Coarse Mesh radiation transport method for 2 d hexagonal geometry
Annals of Nuclear Energy, 2012Co-Authors: Kevin John Connolly, Farzad Rahnema, Dingkang ZhangAbstract:Abstract In this paper, a whole-core stochastic–deterministic hybrid Coarse Mesh transport method is extended to 2-D hexagonal geometry. This method may be used to calculate the eigenvalue and explicit pin fission density profile of hexagonal reactor cores. It models the exact detail within complex heterogeneous cores without homogenizing regions or materials, and neither block-level nor core-level asymmetry poses any limitations to the method. It solves eigenvalue problems by first splitting the core into a set of Coarse Meshes, and then using Monte Carlo methods to create a library of response expansion coefficients, found by expanding the angular current in phase-space distribution using a set of polynomials orthogonal on the angular half-space defined by Mesh boundaries. The Coarse Meshes are coupled by the angular current at their interfaces. A deterministic sweeping procedure is then used to iteratively construct the solution. The method is evaluated using benchmark problems based on a gas-cooled, graphite-moderated high temperature reactor. The method quickly solves problems to any level of detail desired by the user. In this paper, it is used to explicitly calculate the fission density of individual fuel pins and determine the reactivity worth of individual control rods. In every case, results for the core multiplication factor and pin fission density distribution are found within several minutes. Results are highly accurate when compared to direct Monte Carlo reference solutions; errors in the eigenvalue calculations are on the order of 0.02%, and errors in the pin fission density average less than 0.1%.
-
an efficient hybrid stochastic deterministic Coarse Mesh neutron transport method
Annals of Nuclear Energy, 2012Co-Authors: Dingkang Zhang, Farzad RahnemaAbstract:Abstract A new incident flux response expansion method has been developed to significantly improve the accuracy of the hybrid stochastic/deterministic co arse me sh t ransport (COMET) method. Additionally, two acceleration techniques are introduced that significantly increase the computational efficiency of the method by several folds. The new expansion method removes singularities associated with the current method that degrade its accuracy and efficiency and ability to solve realistic problems with complexity and size that are inherent in operating commercial reactors. It also enables (paves the way for) the response method to be imbedded in low order transport methods (e.g., diffusion theory) for improving accuracy without degradation in efficiency. In general, the new expansion method also enables efficient and accurate coupling of different deterministic methods (e.g., characteristic to discrete ordinates and in general high order transport to high or low order transport). The new method improvements enable COMET to perform whole-core neutronics analysis in all light and heavy water operating reactors with Monte Carlo fidelity and efficiency that is several orders of magnitude faster than both direct Monte Carlo and fine Mesh transport methods. A stylized CANDU-6 core benchmark problem with and without adjuster rods was used to test the accuracy and efficiency of the COMET method in whole (full) core configurations at two coolant states. The benchmark problem consisted of 4560 fuel bundles containing a total of 168,720 fuel pins and 21 adjuster rods. The COMET solutions were compared to direct Monte Carlo (MCNP) reference solutions. It was found that the core eigenvalue, bundle averaged and fuel pin power distributions predicated by COMET agree very well with the MCNP reference solution in all cases when the Coarse Mesh incident angular flux expansion in the two spatial and two angular (azimuthal and polar) variables is truncated at 4, 4, 2 and 2, respectively. These comparisons indicate that COMET can achieve accuracy comparable to that of the Monte Carlo method with a computational efficiency that is several orders of magnitude better.
Ricardo C. Barros - One of the best experts on this subject based on the ideXlab platform.
-
ANALYTICAL RECONSTRUCTION SCHEMES FOR Coarse-Mesh SPECTRAL NODAL SOLUTION OF SLAB-GEOMETRY SN TRANSPORT PROBLEMS
2020Co-Authors: Ricardo C. Barros, Hermes Alves Filho, Gustavo Mendes Platt, Bruno S. Oliveira, Damiano S. MilitãoAbstract:Coarse-Mesh numerical methods are very efficient in the sense that they generate accurate results in short computational time, as the number of floating point operations generally decrease, as a result of the reduced number of Mesh points. On the other hand, they generate numerical solutions that do not give detailed information on the problem solution profile, as the grid points can be located considerably away from each other. In this paper we describe two analytical reconstruction schemes for the Coarse-Mesh solution generated by the spectral nodal method for neutral particle discrete ordinates (SN) transport model in slab geometry. The first scheme we describe is based on the analytical reconstruction of the Coarse-Mesh solution within each discretization cell of the spatial grid set up on the slab. The second scheme is based on the angular reconstruction of the discrete ordinates solution between two contiguous ordinates of the angular quadrature set used in the SN model. Numerical results are given so we can illustrate the accuracy of the two reconstruction schemes, as described in this paper.
-
Coarse-Mesh DIFFUSION SYNTHETIC ACCELERATION OF THE SCATTERING SOURCE ITERATIVE SCHEME FOR ONE-SPEED DISCRETE ORDINATES NEUTRON TRANSPORT CALCULATIONS IN SLAB GEOMETRY
2020Co-Authors: Frederico P. Santos, Hermes Alves Filho, Vinicius S. Xavier, Ricardo C. BarrosAbstract:The scattering source iterative (SI) scheme is traditionally applied to converge fine-Mesh numerical solutions to fixed-source one-speed discrete ordinates (SN) neutron transport problems. The SI scheme is very simple to implement under a computational viewpoint. However, the SI scheme may show very slow convergence rate, mainly for diffusive slabs (low absorption) with several mean free paths in extent. In this work we describe an acceleration technique based on an improved initial guess for the scattering source distribution within the slab. In other words, we use as initial guess for the fine-Mesh scattering source, the Coarse-Mesh solution of the neutron diffusion equation with special boundary conditions to account for the classical SN prescribed boundary conditions, including vacuum boundary conditions. Therefore, we first implement a spectral nodal method that generates Coarse-Mesh diffusion solution that is completely free from spatial truncation errors, then we reconstruct this Coarse-Mesh solution within each spatial cell of the discretization grid, to further yield the initial guess for the fine-Mesh scattering source to begin the S N
-
A Coarse-Mesh DIFFUSION SYNTHETIC ACCELERATION OF THE SOURCE ITERATION SCHEME FOR ONE-SPEED DISCRETE ORDINATES TRANSPORT CALCULATIONS IN SLAB GEOMETRY
2020Co-Authors: Frederico P. Santos, Hermes Alves Filho, Vinicius S. Xavier, Ricardo C. BarrosAbstract:The scattering source iterative (SI) scheme is traditionally applied to converge fine-Mesh numerical solutions to fixed-source discrete ordinates ( ) neutron transport problems. The SI scheme is very simple to implement under a computational viewpoint. However, the SI scheme may show very slow convergence rate, mainly for diffusive media (low absorption) with several mean free paths in extent. In this work we describe an acceleration technique based on an improved initial guess for the scattering source distribution within the slab. In other words, we use as initial guess for the fine-Mesh scattering source, the Coarse-Mesh solution of the neutron diffusion equation with special boundary conditions to account for the classical prescribed boundary conditions, including vacuum boundary conditions. Therefore, we first implement a spectral nodal method that generates Coarse-Mesh diffusion solution that is completely free from spatial truncation errors, then we reconstruct this Coarse-Mesh solution within each spatial cell of the discretization grid, to further yield the initial guess for the fine-Mesh scattering source in the first transport sweep (μm > 0 and μm < 0, m = 1:N) across the spatial grid. We consider a number of numerical experiments to illustrate the efficiency of the offered diffusion synthetic acceleration (DSA) technique.
-
Coarse-Mesh diffusion synthetic acceleration of the scattering source iteration scheme for one-speed slab-geometry discrete ordinates problems
2013Co-Authors: Frederico P. Santos, Hermes Alves Filho, Ricardo C. BarrosAbstract:The scattering source iterative (SI) scheme is traditionally applied to converge fine-Mesh numerical solutions to fixed-source discrete ordinates (SN) neutron transport problems. The SI scheme is very simple to implement under a computational viewpoint. However, the SI scheme may show very slow convergence rate, mainly for diffusive media (low absorption) with several mean free paths in extent (low leakage). In this work we describe an acceleration technique based on an improved initial guess for the scattering source distribution within the slab. In other words, we use as initial guess for the fine-Mesh scattering source, the Coarse-Mesh solution of the neutron diffusion equation with special boundary conditions to account for the classical SN prescribed boundary conditions, including vacuum boundary conditions. Therefore, we first implement a spectral nodal method that generates Coarse-Mesh diffusion solution that is completely free from spatial truncation errors, then we reconstruct this Coarse-Mesh so...
-
analytical spatial reconstruction scheme for the Coarse Mesh solutions generated by the constant spectral nodal method for monoenergetic discrete ordinates transport calculations in x y geometry fission chain reacting systems
Annals of Nuclear Energy, 2013Co-Authors: Welton A Menezes, Ricardo C. Barros, Hermes Alves Filho, Caroline S Moraes, Dany S DominguezAbstract:Abstract Nodal methods are widely regarded as forming an accurate class of Coarse-Mesh methods for neutron transport problems in the discrete ordinates (S N ) formulation. They are also viewed as efficient methods, as the number of floating point operations generally decrease, as a result of the reduced number of Mesh points; therefore they generate accurate results in shorter running time. However, the Coarse-Mesh numerical solutions do not yield detailed information on the solution profile, as the grid points can be located considerably apart from each other. In this paper, we describe an analytical spatial reconstruction of Coarse-Mesh solutions of the S N transverse integrated nodal equations with constant approximations for the transverse leakage terms, as generated by the hybrid spectral diamond–spectral Green’s function–constant nodal (SD–SGF–CN) method for monoenergetic S N eigenvalue problems in X,Y geometry for neutron multiplying systems. Numerical results for typical model problems are given and we close with general concluding remarks and suggestions for future work.
Hermes Alves Filho - One of the best experts on this subject based on the ideXlab platform.
-
ANALYTICAL RECONSTRUCTION SCHEMES FOR Coarse-Mesh SPECTRAL NODAL SOLUTION OF SLAB-GEOMETRY SN TRANSPORT PROBLEMS
2020Co-Authors: Ricardo C. Barros, Hermes Alves Filho, Gustavo Mendes Platt, Bruno S. Oliveira, Damiano S. MilitãoAbstract:Coarse-Mesh numerical methods are very efficient in the sense that they generate accurate results in short computational time, as the number of floating point operations generally decrease, as a result of the reduced number of Mesh points. On the other hand, they generate numerical solutions that do not give detailed information on the problem solution profile, as the grid points can be located considerably away from each other. In this paper we describe two analytical reconstruction schemes for the Coarse-Mesh solution generated by the spectral nodal method for neutral particle discrete ordinates (SN) transport model in slab geometry. The first scheme we describe is based on the analytical reconstruction of the Coarse-Mesh solution within each discretization cell of the spatial grid set up on the slab. The second scheme is based on the angular reconstruction of the discrete ordinates solution between two contiguous ordinates of the angular quadrature set used in the SN model. Numerical results are given so we can illustrate the accuracy of the two reconstruction schemes, as described in this paper.
-
Coarse-Mesh DIFFUSION SYNTHETIC ACCELERATION OF THE SCATTERING SOURCE ITERATIVE SCHEME FOR ONE-SPEED DISCRETE ORDINATES NEUTRON TRANSPORT CALCULATIONS IN SLAB GEOMETRY
2020Co-Authors: Frederico P. Santos, Hermes Alves Filho, Vinicius S. Xavier, Ricardo C. BarrosAbstract:The scattering source iterative (SI) scheme is traditionally applied to converge fine-Mesh numerical solutions to fixed-source one-speed discrete ordinates (SN) neutron transport problems. The SI scheme is very simple to implement under a computational viewpoint. However, the SI scheme may show very slow convergence rate, mainly for diffusive slabs (low absorption) with several mean free paths in extent. In this work we describe an acceleration technique based on an improved initial guess for the scattering source distribution within the slab. In other words, we use as initial guess for the fine-Mesh scattering source, the Coarse-Mesh solution of the neutron diffusion equation with special boundary conditions to account for the classical SN prescribed boundary conditions, including vacuum boundary conditions. Therefore, we first implement a spectral nodal method that generates Coarse-Mesh diffusion solution that is completely free from spatial truncation errors, then we reconstruct this Coarse-Mesh solution within each spatial cell of the discretization grid, to further yield the initial guess for the fine-Mesh scattering source to begin the S N
-
A Coarse-Mesh DIFFUSION SYNTHETIC ACCELERATION OF THE SOURCE ITERATION SCHEME FOR ONE-SPEED DISCRETE ORDINATES TRANSPORT CALCULATIONS IN SLAB GEOMETRY
2020Co-Authors: Frederico P. Santos, Hermes Alves Filho, Vinicius S. Xavier, Ricardo C. BarrosAbstract:The scattering source iterative (SI) scheme is traditionally applied to converge fine-Mesh numerical solutions to fixed-source discrete ordinates ( ) neutron transport problems. The SI scheme is very simple to implement under a computational viewpoint. However, the SI scheme may show very slow convergence rate, mainly for diffusive media (low absorption) with several mean free paths in extent. In this work we describe an acceleration technique based on an improved initial guess for the scattering source distribution within the slab. In other words, we use as initial guess for the fine-Mesh scattering source, the Coarse-Mesh solution of the neutron diffusion equation with special boundary conditions to account for the classical prescribed boundary conditions, including vacuum boundary conditions. Therefore, we first implement a spectral nodal method that generates Coarse-Mesh diffusion solution that is completely free from spatial truncation errors, then we reconstruct this Coarse-Mesh solution within each spatial cell of the discretization grid, to further yield the initial guess for the fine-Mesh scattering source in the first transport sweep (μm > 0 and μm < 0, m = 1:N) across the spatial grid. We consider a number of numerical experiments to illustrate the efficiency of the offered diffusion synthetic acceleration (DSA) technique.
-
Coarse-Mesh diffusion synthetic acceleration of the scattering source iteration scheme for one-speed slab-geometry discrete ordinates problems
2013Co-Authors: Frederico P. Santos, Hermes Alves Filho, Ricardo C. BarrosAbstract:The scattering source iterative (SI) scheme is traditionally applied to converge fine-Mesh numerical solutions to fixed-source discrete ordinates (SN) neutron transport problems. The SI scheme is very simple to implement under a computational viewpoint. However, the SI scheme may show very slow convergence rate, mainly for diffusive media (low absorption) with several mean free paths in extent (low leakage). In this work we describe an acceleration technique based on an improved initial guess for the scattering source distribution within the slab. In other words, we use as initial guess for the fine-Mesh scattering source, the Coarse-Mesh solution of the neutron diffusion equation with special boundary conditions to account for the classical SN prescribed boundary conditions, including vacuum boundary conditions. Therefore, we first implement a spectral nodal method that generates Coarse-Mesh diffusion solution that is completely free from spatial truncation errors, then we reconstruct this Coarse-Mesh so...
-
analytical spatial reconstruction scheme for the Coarse Mesh solutions generated by the constant spectral nodal method for monoenergetic discrete ordinates transport calculations in x y geometry fission chain reacting systems
Annals of Nuclear Energy, 2013Co-Authors: Welton A Menezes, Ricardo C. Barros, Hermes Alves Filho, Caroline S Moraes, Dany S DominguezAbstract:Abstract Nodal methods are widely regarded as forming an accurate class of Coarse-Mesh methods for neutron transport problems in the discrete ordinates (S N ) formulation. They are also viewed as efficient methods, as the number of floating point operations generally decrease, as a result of the reduced number of Mesh points; therefore they generate accurate results in shorter running time. However, the Coarse-Mesh numerical solutions do not yield detailed information on the solution profile, as the grid points can be located considerably apart from each other. In this paper, we describe an analytical spatial reconstruction of Coarse-Mesh solutions of the S N transverse integrated nodal equations with constant approximations for the transverse leakage terms, as generated by the hybrid spectral diamond–spectral Green’s function–constant nodal (SD–SGF–CN) method for monoenergetic S N eigenvalue problems in X,Y geometry for neutron multiplying systems. Numerical results for typical model problems are given and we close with general concluding remarks and suggestions for future work.
Emiliano Masiello - One of the best experts on this subject based on the ideXlab platform.
-
on the fly stabilization of the Coarse Mesh finite difference acceleration for multidimensional discrete ordinates transport calculations
Journal of Computational Physics, 2018Co-Authors: Emiliano MasielloAbstract:Abstract In this paper, the Jacobian matrix of the Coarse-Mesh Finite Difference (CMFD) method is analyzed. Both the homogenization and the current preservation effects are studied in heterogeneous multidimensional configurations. Some bounding values of the spectral radius are also given. An analytical stability analysis is carried on an interface slab problem. This analysis leads to the computation of the stability parameter introduced in the Generalized Coarse Mesh Rebalancing method. A dynamical stabilization technique is proposed for multidimensional neutron lattice calculations. Numerical calculations show that the proposed technique dumps the unstable modes, in particular in optically thick configurations, where the classical CMFD method fails to converge.