CFD Investigation of Transient Wave-Blockage Interactions in Water Pipelines

In previous studies, analytical and numerical investigations of transient behaviors in a pipeline with blockages in the time domain or frequency domain are commonly based on the one-dimensional (1D) water hammer equations due to their efficiency and convenience for implementation. However, the detailed behaviors and interactions of transient waves with such blockages cannot be well represented and interpreted from the current 1D models and methods. To this end, this paper investigates the transient behavior of a water supply pipeline with blockage under different wave perturbations for transient generations. The 2D Computational Fluid Dynamics (CFD) model is applied for this investigation. Specifically, a water pipeline is modeled in a 2D axisymmetric geometry with refined mesh and the blockage is modeled as a small, constricted section. Both the low and high-frequency waves (LFW and HFW), in terms of radial fundamental wave frequency of a pipeline, ~a/R, with a being acoustic wave speed and R being pipe radius, are injected for the numerical analysis. Based on this 2D CFD model, both the axial and radial transient waves can be obtained and analyzed have been observed for different frequency wave injections (LFW and HFW), which is firstly validated by datasets available from former studies. After validations, the local flow characteristics in the vicinity of blockage during transient wave processes, including before and after transient wavefront passing, are analyzed. Finally, the results and findings of this study are discussed for the underlying physics and mechanism of transient wave-blockage interactions and the development and application of transient-based blockage detection in pipelines.