As we approach the half-century milestone of utilizing mechanistic flow models in the design and operation of multiphase production systems, it becomes evident that these models have undergone significant evolution, paralleling the advancements in the simulators that employ them. In the present day, state-of-the-art models continue to undergo refinement and adaptation to address emerging challenges. This paper examines these models, scrutinizing their performance against both experimental and field data to identify areas of robust confidence and lingering uncertainties. Moreover, we highlight key domains of ongoing research aimed at further enhancing modeling capabilities to meet the demands of the next generation of challenges on the horizon.
