Numerical Scheme of the WAHA code
by I. Tiselj, A. Horvat, J. Gale, I. Parzer, Multiphase Science and Technology, 2008, Vol. 20. Issue 3-4, pp. 323-354.
This paper describes the numerical scheme used in the WAHA code that was developed within the WAHALoads project for simulations of fast transients in 1D piping systems. Two-fluid model equations are solved with an operator splitting procedure. A second-order accurate non-conservative characteristic upwind scheme is used to solve the hyperbolic part of the equations with the non-relaxation source terms, while the relaxation source terms are treated in the second step of the operator splitting procedure. The water-vapour properties are calculated with a newly developed set of subroutines that use pre-tabulated water properties. Special models that were developed for the treatment of the abrupt area-changes and branches in the piping systems are described. Various test cases, which were used to test the accuracy of the basic numerical scheme and the accompanying numerical models, are described together with typical results of the simulations.
