Assessment of the IVA3 code for multifield flow simulation
Abstract
This report presents an assessment of the IVA3 computer code for multifield flow simulation, as applied to the premixing phase of a hypothetical steam explosion in a watercooled power reactor. The first section of this report reviews the derivation of the basic partial differential equations of multifield modeling, with reference to standard practices in the multiphase flow literature. Basic underlying assumptions and approximations are highlighted, and comparison is made between IVA3 and other codes in current use. Although Kolev's derivation of these equations is outside the mainstream of the multiphase literature, the basic partial differential equations are in fact nearly equivalent to those in other codes. In the second section, the assumptions and approximations required to pass from generic differential equations to a specific working form are detailed. Some modest improvements to the IVA3 model are suggested. In Section 3, the finite difference approximations to the differential equations are described. The discretization strategy is discussed with reference to numerical stability, accuracy, and the role of various physical phenomena  material convection, sonic propagation, viscous stress, and interfacial exchanges  in the choice of discrete approximations. There is also cause for concern about the approximations of time evolution in some heat transfer terms, which might be adversely affecting numerical accuracy. The fourth section documents the numerical solution method used in IVA3. An explanation for erratic behavior sometimes observed in the first outer iteration is suggested, along with possible remedies. Finally, six recommendations for future assessment and improvement of the IVA3 model and code are made.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 July 1995
 Bibcode:
 1995STIN...9613145S
 Keywords:

 Computer Programs;
 Computerized Simulation;
 Explosions;
 Finite Difference Theory;
 Multiphase Flow;
 Power Reactors;
 Premixing;
 Water Cooled Reactors;
 Heat Transfer;
 Iteration;
 Mathematical Models;
 Numerical Stability;
 Partial Differential Equations;
 Fluid Mechanics and Heat Transfer