Air entrapment modelling during pipe filling based on SWMM

Abstract

The paper proposes a novel methodology to locate and quantify entrapped air pockets created during pipe-filling events often found in intermittent water supply systems. Different filling conditions were tested in an experimental pipe with a high point. Measurements were taken and video recordings were carried out to assess air pocket volumes for different air release conditions at the downstream end of the pipe. The stochastic nature of air pocket creation resulted in varying air volumes. A new numerical model capable of simulating the air pocket creation, dragging and entrainment has been proposed. The new model, AirSWMM, was implemented as an extension of the Stormwater Management Model (SWMM) with stochasticity of air pocket formation reproduced by simulations with different air entrainment rates. The obtained numerical results show that the proposed model, even though based on a single-phase one-dimensional flow, can accurately locate and approximately quantify the entrapped air pocket volumes.

KEYWORDS:

• Air–water interface interaction
• air pocket entrapment
• flow visualization and imaging
• intermittent water supply
• SWMM
• water pipelines

Additional information

Funding

The authors acknowledge the Portuguese national funding agency, Fundação da Ciência e Tecnologia (FCT), for funding the reported work within grant number SFRH/BD/146709/2019 and for the support through funding UIDB/04625/2020 for the research unit CERIS; Civil Engineering Research and Innovation for Sustainability.