Computational aspects of premixing modelling

In the steam explosion research field there is currently considerable effort being devoted to the modelling of premixing. Practically all models are based on the multiphase flow equations that treat the mixture as an interpenetrating continuum. The solution of these equations is non-trivial and a wide range of solution procedures are in use. Some numerical aspects of this problem are addressed here. In particular, the effect of the differencing scheme for the convective terms are examined and the use of hybrid differencing is shown to cause qualitatively wrong solutions in some situations. Calculations are performed for the Oxford tests, the BNL tests, a MAGICO test and to investigate various sensitivities of the solution. In addition, it is shown that the use of a staggered grid can result in a significant error that leads to poor predictions of ʹmeltʹ front motion. A correction is given that leads to excellent convergence to the analytic solution. Finally, the issues facing premixing model developers are discussed and the fact that model validation is hampered more by the complexity of the process than by numerical issues is highlighted. 1999 Elsevier Science S.A. All rights reserved.