Abstract
The major objective of this study was to design a model to optimize sewage flow through pipe-manhole drainage systems using Computational Fluid Dynamics (CFD). Multi-phase flows like two-phase flow in transport pipes is a common occurrence in many industrial applications such as sewage, water, oil, gas transportation and power generation. Accurate prediction of fluid velocity and pressure drop is of utmost importance to ensure effective design and operation of fluid transport systems. Numerical simulations were performed at different pipe inclinations and fluid flow velocities. A two-dimensional pipe of 0.5 m in diameter and 20 m long was used with a Standard k−ε turbulence and the volume of fraction (VOF) free surface model to solve the turbulent mixture flow of air and water. The CFD approach is based on the Navier-Stokes equations. Results show that the flow pattern behaviour and numerical values of liquid velocities and pressure drop compare reasonably well. It is concluded that the most effective way to optimize a sewer network system in order to minimize the overflows through Pipe-manhole drainage system for Mbale Municipality conditions is by considering minimum and maximum sewer velocities in the range 0.67 ms−1 to 5.5 ms−1 respectively, sewer diameters, slope gradients for optimal sewer design and expanding the number of sewer network connections of household, municipal and industries.
Highlights
In urban areas, drainage sewer networks contain a large number of structures
This study presents a Mathematical model for the sewage overflow through pipe-manhole drainage sewer systems using the open source Computational Fluid Dynamics (CFD) software OpenFOAM based on interFoam solver
Some of the sewer lines during rainfall seasons are infiltrated by the stormwater either through unauthorized connections of stormwater channels by the public to the sewer lines or through damaged manholes, this has always led to the increased flow in the system and blockages which causes backflow of sewage overflow through any opening, more so through the manholes
Summary
Municipal Sewage systems were built to rapidly collect rain runoff, wastewater and sewage (Esemu et al, 2020). These network structures consist of pipes, manholes, pumping stations, force mains, and other facilities required to collect and transport wastewater (Esemu et al, 2020; Moeini and Afshar, 2017). Manhole is one of the most common features of an urban drainage sewer system It is usually placed at a drainage network connection where a change in pipe direction, size or gradient is necessary. Some older sewers do not meet the modern requirements for self-cleaning that result in high blockages (Esemu et al, 2020; Swamee and Sharma, 2013)
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