To simulate complex bubbly flows in large diameter vertical pipes

the average bubble number density (ABND）model based on the population balance approach is employed and incorporated into the three-dimensional two-fluid model.To account the interfacial momentum transfer

essential interfacial force models are implemented and coupled with the two-fluid model.Fully mechanistic kernels are also integrated in the ABND model to account the evolution of bubble size due to its coalescence and breakage processes.To assess the performance of the ABND model

numerical studies are carried out to simulate various flow conditions and validate against a high-quality TOPFLOW experiment database with a nominal diameter of 195.3 mm. In comparison to the measurements

predictions from the ABND model appear marginally superior to those using MUSIG model.In addition

close agreement between the predictions and measurements is also achieved for local radial distributions of void fraction

Sauter mean diameter

and gas velocity

which clearly demonstrates the applicability of the bubble number density transport equation for modelling bubbly flow in large diameter pipes.