Enhancing the Prediction Accuracy of Transient Turbulent Pressurized Pipe Flow Responses: A Comprehensive Q2D Model Incorporating Additional Local Instantaneous Accelerations

Abstract

This paper investigated transient events for unsteady pressurized pipe flow, particularly during water hammer events, to compare the efficiency of the one-dimensional (1D) modified Brunone’s model called the modified instantaneous acceleration-based (MIAB) method and the quasi-two-dimensional (Q2D) method which can even incorporate the time-varying eddy viscosity. Although both dynamic hypotheses can lead to high accuracy in tracing the measurements, instantaneous acceleration-based (IAB) models, which attribute flow damping to instantaneous temporal and convective accelerations at the wavefront, cannot precisely predict the sharp-shaped peaks. Conversely, the Q2D method slightly overpredicts the long-term observations, hypothesizing that the viscous local shear stress is responsible for turbulent kinetic energy dissipation. This research presents a two-dimensional (2D) approximation (neither 1D nor hybrid) by incorporating a modified time-varying turbulence model to consider the total energy dissipation across the pipe area precisely. It simultaneously emphasizes the need for a more robust simulated damping and exact phase shape estimation, such that an additional local shear stress or force produced by assumed local temporal and convective additional accelerations or forces is combined with the local shear friction resulting from the kinematic viscosity. When two decay coefficients were calibrated against the experimental data using a two-stage genetic algorithm optimization, the model significantly improved the fitness function compared with the former models.