Comparison between the Two-component Pressure Approach and Current Transient Flow Solvers

Some hydraulic applications are characterized by systems originally flowing in free-surface conditions that subsequently undergo flow regime transition into pressurized flow during rapid filling events. Currently, models simulating these flow regime transitions are classified by approaches that either track the location of the pressurized front or use the Preissmann slot concept. While Preissmann slot models are popular for their overall simplicity, they have some limitations, such as the inability to simulate full-pipe flows with piezometric heads below the pipe crown. Recently, a new model named Two-Component Pressure Approach overcame some limitations of current flow regime transition models. However, the performance of this new method has not been tested against existing models. Also, similarly to Preissmann slot models, when shock-capturing methods are used in the computations, postshock numerical oscillations appear in the results. This article presents a comparison between TPA model and three transient flow models. The models are based on the Interface-Tracking approach, the Preissmann slot concept and a standard closed pipe Method of Characteristics code. A procedure to reduce the post-shock oscillation problem is presented. TPA results show good agreement with the results from the models considered in this study.