RESUMO

A new thermal hydraulic computer code, WAHA, was developed within the WAHALoads project of the European Union Fifth Framework Program. The code's aim is simulation of water hammer transients in piping systems and is based on a one-dimensional, two-fluid, six-equation model of the two-phase flow. The WAHA code can describe two-phase flows in long piping systems (1D geometry) with variable cross section. The code contains correlations for heat, mass, and momentum transfer between the phases and for wall friction in dispersed and horizontally stratified flow regimes. The WAHA code physical model takes into account the elasticity of the pipe through Korteweg's equation; it takes into account water properties and the unsteady wall friction, and contains a set of subroutines for calculation of forces on the piping system. Special models in the WAHA code are implemented for abrupt area changes and branches, for constant pressure (tank), for constant velocity (pump), and for valve closure boundary conditions. The physical model and the main correlations and closure laws, which are applied in the present work, are described and verified with several experiments. The code was successfully applied for simulations of two-phase critical flow, several column-separation types of water hammer, and for condensation-induced water hammer experiments.