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APPENDIX 3 : Conference Paper "The Development and Application of Group Solversin the SMARTFIRE Fire Field Model", Ewer J., Galea E., Patel M. and Knight B.,Proceedings of Interflam '99, Edinburgh, UK, 1999, Vol. 2, pp 939-950.THE DEVELOPMENT AND APPLICATION OFGROUP SOLVERS IN THE SMARTFIREFIRE FIELD MODEL.ABSTRACTJ.A.C.Ewer, E.R.Galea, M.K.Patel and B.Knight.Fire Safety Engineering GroupCentre for Numerical Modelling and Process Analysis,University of Greenwich,London SE18 6PF, UKhttp://fseg.gre.ac.uk/This paper describes a new solution technique - known as the “group solver” -currently under development within the SMARTFIRE Computational Fluid Dynamicsenvironment. The group solver is used to obtain numerical solutions to the algebraicequations associated with fire field modelling. The purpose of the technique is to reduce thecomputational overheads associated with traditional numerical solvers typically used in firefield modelling applications. In the example, discussed in this paper, the group solver isshown to provide a 37% saving in computational time over a traditional solver.INTRODUCTIONIn traditional Computational Fluid Dynamics (CFD) based fire models [1], control ofthe numerical solver applies equally over all of the cells throughout the solution domain. Inlarge geometry cases this can create a significant, and at times limiting, computationaloverhead. This is particularly true in cases where the fire occupies a relatively smallproportion of an otherwise large solution domain for part, or all, of the simulation period.An example of this may be the early stages of fire growth within an airport terminal or aroad/rail tunnel. The group solver concept attempts to address this problem algorithmically,by providing optimal processing in regions of the domain where and when it is required.In the group solver concept, the solution domain is split into an arbitrary number of groupsof-cells.A group is defined as a unique collection of cells that can have solver controlparameters independent from any other groups in the solution domain. Group solvers can beactivated independently for each solved variable. Internally, the group solver makes use ofstandard numerical “point-by-point” solution methods such as JOR or SOR.One way in which this may be achieved is by controlling the number of iterations that thesolver performs in the various groups. For instance, the maximum number of iterations in an“Inactive group” will be considerably smaller than the number for an “Active group”. As thesolution develops, cells can migrate to and from groups, thus receiving more or lesscomputational attention. The overall convergence criteria are still configured as forconventional problems so there should be no significant difference in the quality of theconverged solution.Appendix 11.3 Page 143-1 1