Adaptive multigroup radiation diffusion

This thesis describes the development and implementation of an algorithm for dramatically increasing the accuracy and reliability of multigroup radiation diffusion simulations at low group counts. This is achieved by allowing the energy group boundaries to move in energy space as the simulation evolves. This adaption in energy space effectively removes the sensitivity of multigroup diffusion to group boundary placement and makes the technique a viable option for large, computationally expensive computer simulations. Traditional multigroup radiation diffusion solvers break down at small group counts because of the coarse discretization of highly nonlinear material opacity. Small changes in the group boundary energies can lead to wildly different mean opacities and therefore significant changes in simulation output. This sensitivity has rendered the technique unpredictable and it is generally considered to be not worth the added computational expense. Unfortunately, multigroup diffusion is the only method available for adding frequency dependence to the radiation field in a standard diffusion solver. When attempting to model a system that includes a non-equilibrium radiation field, frequency-dependent effects become important.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Nuclear Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Williams, Richard B., Sc. D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Kim Molvig.

• Nuclear Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/34430

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/34430