This work presents a numerical model for predicting the isothermal transient two-phase flow of liquid-gas homogeneous mixtures in rigid pipelines. The resulting mathematical problem is governed by a system of non-linear hyperbolic partial differential equations which is solved by means of an operator splitting technique, combined with the Glimm’s method. To implement Glimm’s method, it is presented the closed-form analytical solution of the associated Riemann problem. Uniqueness of this solution is demonstrated for a general set of equations of state for the liquid and the gas. Preliminary numerical results are presented in order to illustrated the model performance.

In many engineering applications, compliant piping systems conveying liquids are subjected to inelastic deformations due to severe pressure surges such as plastic tubes in modern water supply transmission lines and metallic pipings in nuclear power plants. In these cases the design of such systems may require an adequate modeling of the interactions between the fluid dynamics and the inelastic structural pipe motions. The reliability of the prediction of fluid-pipe behavior depends mainly on the adequacy of the constitutive equations employed in the analysis. In this paper it is proposed a systematic and general approach to consistently incorporate different kinds of inelastic behaviors of the pipe material in a fluid-structure interaction analysis. The main feature of the constitutive equations considered in this work is that a very simple numerical technique can be used for solving the coupled equations describing the dynamics of the fluid and pipe wall. Numerical examples concerning the analysis of polyethylene and stainless steel pipe networks are presented to illustrate the versatility of the proposed approach