Hydraulic Transient Analysis of Sewer Pipe Systems Using a Non-Oscillatory Two-Component Pressure Approach

David Khani,Yeo Howe Lim,Ahmad Malekpour

doi:10.3390/w12102896

David Khani, Yeo Howe Lim + Show 1 more

Open Access

https://doi.org/10.3390/w12102896

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Journal: Water	Publication Date: Oct 16, 2020
Citations: 5	License type: CC BY 4.0

Affiliation: University of North Dakota, Thornhill Medical (Canada)

Abstract

On the basis of the two-component pressure approach, we developed a numerical model to capture mixed transient flows in close conduit systems. To achieve this goal, an innovative Godunov finite-volume numerical scheme is proposed to suppress the spurious numerical oscillations occurring during rapid pipe pressurization. To dissipate the spurious numerical oscillations, we admit artificial numerical viscosity to the numerical scheme through applying a proposed Harten, Lax, and van Leer (HLL) Riemann solver for calculating the numerical fluxes at the computational cell interfaces. The proposed solver controls the magnitude of the numerical viscosity through adjusting the left and right wave velocities. A wave velocity calculator is proposed to optimally distribute the numerical viscosity over several computational cells around the computational cell in which the pressurization front is located. The proposed solver admits significant artificial numerical viscosity when the pipe pressurization is imminent and automatically reduces it in other places; in this way the numerical diffusion and data smearing is minimized. The validity of the proposed model is justified by the aid of several test cases in which the numerical results are compared with both experimental data and the results obtained from analytical methods. The results reveal that the proposed model succeeds in completely removing the spurious numerical oscillations, even when the pipe acoustic speed is over 1000 m/s. The numerical results also show that the model can successfully capture occurrence of negative pressures during the course of transient flow.

Highlights

While responding to a wet flow event, storm water pipe systems experience complex transient flow in which both open channel and pressurized flow regimes may coexist [1]
The results showed that the hybrid flux method can partially suppress the numerical oscillations, but data smearing becomes significant when the numerical viscosity further increases to completely remove the spurious numerical oscillations
The numerical oscillations ware to the fact to that the during pipe pressurization, the wave velocity drastically increases when the attributed theduring fact that the pipe pressurization, the wave velocity drastically increases flow is switched from open channel to pressurized flow; the higher the pipe’s acoustic wave speed, when the flow is switched from open channel to pressurized flow; the higher the pipe’s acoustic the more intensified numerical such cases, the conventional

Summary

Introduction

While responding to a wet flow event, storm water pipe systems experience complex transient flow in which both open channel and pressurized flow regimes may coexist [1]. The resulting transient flows may induce significant positive and negative pressure surges that can be intense enough to compromise the integrity of the system. Model can theoretically replicate the transient flow but it is computationally too expensive and time consuming to be used in the context of the design of such systems that are iterative in nature. Simplified models are usually employed in practice to calculate the transient response of sewer systems in practice. Momentum, and energy is mainly transferred in the longitudinal direction of the pipe, one-dimensional models have shown to be a reliable tool for capturing the main features of the transient flows in pipe systems.

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