Cellwise Block Iteration as a Multigrid Smoother for Discrete-Ordinates Radiation-Transport Calculations

2016 ◽  
Vol 46 (1) ◽  
pp. 20-45 ◽  
Author(s):  
Jeffery D. Densmore ◽  
Daniel F. Gill ◽  
Justin M. Pounders
Keyword(s):  
Radiation Transport ◽  
Discrete Ordinates ◽  
Block Iteration

Numerical Investigation of Radiation Effects in Catalytic Combustion

2007 ◽  
Author(s):  
Sandip Mazumder ◽  
Michael Grimm
Keyword(s):  
Carbon Monoxide ◽  
Thermal Radiation ◽  
Catalytic Combustion ◽  
Radiation Effects ◽  
Single Channel ◽  
Radiation Transport ◽  
Catalytic Converter ◽  
Discrete Ordinates ◽  
Flammability Limits ◽  
Carbon Monoxide Combustion

In modeling catalytic combustion in a monolithic catalytic converter, it is generally assumed that the gas within the individual monolith channels does not interfere with thermal radiation. To date, no quantitative study has been undertaken to validate this assumption. Past studies for carbon monoxide combustion also appear to indicate that the emissivity of the washcoat has little effect on the thermal radiation field. In order to investigate these two issues, methane-air combustion on platinum is modeled inside a single channel of a monolith using a detailed surface reaction mechanism comprised of 24 reactions between 19 species. Radiation transport is modeled using the Discrete Ordinates Method and a gray formulation. Planck-mean absorption coefficients of the gases, calculated from the HITEMP and HITRAN databases, are used to investigate participating medium effects. All calculations were performed using the commercial CFD code, CFD-ACE+™, supplemented by user-subroutines for calculating the absorption coefficient of the gas mixture. Results show that the conversion percentages and temperature distributions are unaltered by the inclusion of participating medium radiation effects, verifying the commonly held belief, stated earlier. However, in strong contrast with carbon monoxide combustion, the emissivity of the washcoat was found to significantly affect flammability limits in the case of methane combustion—the flame being hotter and more stable for smaller values of emissivity.

Numerical Investigation of Radiation Effects in Monolithic Catalytic Combustion Reactors

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Sandip Mazumder ◽  
Michael Grimm
Keyword(s):  
Carbon Monoxide ◽  
Thermal Radiation ◽  
Catalytic Combustion ◽  
Radiation Effects ◽  
Single Channel ◽  
Radiation Transport ◽  
Catalytic Converter ◽  
Radiative Properties ◽  
Discrete Ordinates ◽  
Carbon Monoxide Combustion

In modeling catalytic combustion in a monolithic catalytic converter, it is generally assumed that the gas within the individual monolith channels does not interfere with thermal radiation. To date, no quantitative study has been undertaken to validate this assumption. Past studies for carbon monoxide combustion also appear to indicate that the emissivity of the washcoat has little effect on the thermal radiation field. In order to investigate these two issues, methane-air combustion on platinum is modeled inside a single channel of a monolith using a detailed surface reaction mechanism comprised of 24 reactions between 19 species. Radiation transport is modeled using the Discrete Ordinates Method and a gray formulation. Planck-mean absorption coefficients of the gases, calculated from the HITEMP and HITRAN databases, are used to investigate participating medium effects. All calculations were performed using the commercial CFD code, CFD-ACE+™, supplemented by user-subroutines for calculating the radiative properties of the gas mixture. Results show that the conversion percentages and temperature distributions are unaltered by the inclusion of participating medium radiation effects, verifying the commonly held belief, stated earlier. However, in strong contrast with carbon monoxide combustion, the emissivity of the washcoat was found to significantly affect flammability limits in the case of methane combustion—the flame being hotter and more stable for smaller values of emissivity.

Adaptive Partial-Current Discrete Ordinates Radiation Transport with Distribution Iteration: An Alternative to Source Iteration

2009 ◽  
Vol 163 (3) ◽  
pp. 191-214
Author(s):  
Kirk Mathews ◽  
James Dishaw ◽  
Nicholas Wager ◽  
Nicholas Prins
Keyword(s):  
Radiation Transport ◽  
Discrete Ordinates ◽  
Partial Current

scholarly journals A Comparison of Angular Discretization Techniques for the Radiative Transport Equation

2015 ◽  
Author(s):  
John Tencer
Keyword(s):  
Spherical Harmonics ◽  
Radiation Transport ◽  
Radiative Flux ◽  
Benchmark Problems ◽  
Discrete Ordinates ◽  
Flux Divergence ◽  
Discontinuous Boundary ◽  
All Solutions ◽  
Mesh Resolution ◽  
Ray Effects

Two of the most popular deterministic radiation transport methods for treating the angular dependence of the radiative intensity for heat transfer: the discrete ordinates and simplified spherical harmonics approximations are compared. A problem with discontinuous boundary conditions is included to evaluate ray effects for discrete ordinates solutions. Mesh resolution studies are included to ensure adequate convergence and evaluate the effects of the contribution of false scattering. All solutions are generated using finite element spatial discretization. Where applicable, any stabilization used is included in the description of the approximation method or the statement of the governing equations. A previous paper by the author presented results for a set of 2D benchmark problems for the discrete ordinates method using the PN-TN quadrature of orders 4, 6, and 8 as well as the P1, M1, and SP3 approximations. This paper expands that work to include the Lathrop-Carlson level symmetric quadrature of order up to 20 as well as the Lebedev quadrature of order up to 76 and simplified spherical harmonics of odd orders from 1 to 15. Two 3D benchmark problems are considered here. The first is a canonical problem of a cube with a single hot wall. This case is used primarily to demonstrate the potentially unintuitive interaction between mesh resolution, quadrature order, and solution error. The second case is meant to be representative of a pool fire. The temperature and absorption coefficient distributions are defined analytically. In both cases, the relative error in the radiative flux or the radiative flux divergence within a volume is considered as the quantity of interest as these are the terms that enter into the energy equation. The spectral dependence of the optical properties and the intensity is neglected.

scholarly journals Analysis of directly driven ICF targets

1986 ◽  
Vol 4 (3-4) ◽  
pp. 349-392 ◽  
Author(s):  
G. Velarde ◽  
J. M. Aragones ◽  
J. A. Gago ◽  
L. Gamez ◽  
M. C. Gonzalez ◽  
...  
Keyword(s):  
Equations Of State ◽  
Radiation Transport ◽  
Simulation Models ◽  
Computational Procedure ◽  
Particle Beam ◽  
Heavy Ion ◽  
Atomic Data ◽  
Discrete Ordinates ◽  
Particle In Cell ◽  
Charged Particle Transport

In this article the current capabilities at DENIM for the analysis of directly driven targets are presented. These include theoretical, computational and applied physical studies and developments of detailed simulation models for the most relevant processes in ICF. The simulation of directly driven ICF targets is carried out with the one-dimensional NORCLA code developed at DENIM. This code contains two main segments: NORMA and CLARA, able to work fully coupled and in an iterative manner. NORMA solves the hydrodynamic equations in a lagrangian mesh. It has modular programs coupled to it to treat the laser or particle beam interaction with matter. Equations of state, opacities and conductivities are taken from a DENIM atomic data library, generated externally with other codes that will also be explained in this work. CLARA solves the transport equation for neutrons, (Boltzmann), as well as for charged particles, and suprathermal electrons (Fokker-Planck), using discrete ordinates and finite element methods in the computational procedure. Parametric calculations of multilayered single-shell targets driven by heavy ion beams are also analyzed. Finally, conclusions are focused on the ongoing developments in the areas of interest such as: radiation transport, atomic physics, particle in cell method, charged particle transport, two-dimensional calculations and instabilities.

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