Calculating Head Loss due to Air-Binding in Water and Wastewater Pipelines Using an Innovative Transient Model

To better support the design and operation of water and wastewater systems, a novel numerical model is proposed to calculate the additional head loss due to air-binding (or even air-lock) and the associated capacity reduction. The model solves one-dimensional waterhammer equations with a moving water column interface to replicate liquid filling in empty pipelines while keeping track of the potential to entrap air pockets in the pipeline. Applying the model to an existing pumping system revealed that air entrapment in a few locations caused a capacity reduction of around 15%. A field test was then conducted to justify the numerical results. The test results confirmed the locations of air entrapment identified by the model, although the model slightly underestimated the head losses caused by the air pockets. Despite this limitation, the model demonstrates sufficient accuracy in predicting the location, size, and associated head losses caused by trapped air pockets.