The Applicability of the Extended 1D Unsteady Friction Model to Water Hammer Scenarios in Pipes within Water Distribution Systems

Abstract Submission: This work aims to assess the validity of the extended one-dimensional (1D) unsteady friction (UF) model, developed by Guerrero et al., to water hammer scenarios. This model utilizes an empirical term to describe the extended turbulence response based on direct numerical simulation (DNS) data. However, Guerrero’s model was derived from single flow change scenarios (e.g., linear and separated velocity changes, such as isolated acceleration or deceleration). In practice, however, the velocity changes are typically non-linear due to the characteristics of flow devices, such as pumps and valves. In addition, velocity variations from unsteady flow or water hammer events generally involve combinations of acceleration and deceleration at pipe sections other than the end sections. Therefore, it is necessary to assess the applicability of the extended 1D UF model for more complex flow scenarios (e.g., non-linear velocity variations and combined conditions of acceleration and deceleration) before applying it to water hammer scenarios. To this end, this work will assess the validity of the extended 1D UF model to water hammer events using detailed computational fluid dynamics (CFD) simulations. The assessment process is undertaken for various unsteady flow cases, such as non-linear accelerations, decelerations, and combinations of both. First, a suitable CFD model for the specific unsteady pipe flow will be selected and validated using DNS data. Then, the assessment will be performed by comparing wall shear stress predictions from the CFD model with those from the extended 1D UF model.
Keywords: Unsteady friction, turbulence, wall shear stress, pipe flows, viscosity, water hammer.

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