Modeling of unsteady fluid transients induced by sudden valve closure in flow networks

This study presents a numerical framework to model unsteady fluid transients resulting from rapid valve closure in complex flow networks, with an emphasis on the development and comparative evaluation of the flexible pipe network flow (FPNF) and unsteady friction network flow (UFNF) models. Building on the baseline network flow approach, which utilizes a one-dimensional finite volume method, the FPNF model incorporates pipe flexibility, adjusting wave speed to enhance accuracy in pressure prediction. The UFNF model extends this framework by integrating an instantaneous acceleration-based unsteady friction model, offering a more precise representation of transient behaviors, particularly for capturing oscillations at low Reynolds numbers where unsteady friction significantly impacts system dynamics. Validation through comparisons with the method of characteristics and experimental data highlights the UFNF model's superiority in minimizing errors in pressure oscillation predictions. Energy and error analyses further confirm the effectiveness of the FPNF model in accounting for flexibility effects. However, the UFNF model achieves greater accuracy across a range of Reynolds numbers, making it especially suited for systems requiring detailed and precise predictions of pressure and friction. These findings underscore the UFNF model's potential as a robust tool for fluid transient analysis, with particular relevance to applications demanding comprehensive unsteady friction modeling.