  We perform direct numerical simulations of a kerosene-water mixture in pipe
flow under realistic experimental conditions by solving the
Cahn-Hilliard-Navier-Stokes equations. We compute the linear stability of
core-annular flow of kerosene and water in a vertical pipe and find that it is
highly unstable. By performing DNS initialized with a slightly perturbed
core-annular flow, we show that the system transitions to turbulence and
finally relaxes into a turbulent slug flow regime provided that the pipe is
sufficiently long. This configuration presents mild turbulence and large scale
three-dimensional recirculation patterns inside the slugs. Our work highlights
the need for applying nonlinear-dynamics approaches and carefully selecting the
domain length to investigate the patterns observed in two-phase pipe flows and
demonstrates the capabilities of phase field methods to reliably simulate
experimental conditions.
