Simulation of Interfacial Waves in Core-Annular Pipe Flow With a Turbulent Annulus

Numerical simulations are conducted for the wave initiation, growth, and saturation at the oil–water interface in core-annular flow (CAF). The focus is on conditions with a turbulent water annulus, but the laminar water annulus is also considered. The simulation results are compared with lab measurements. The growth rate for the linear instability of different wavelengths in the case of a turbulent water annulus is obtained from two-dimensional (2D) axisymmetric Reynolds-averaged Navier–Stokes (RANS) simulations with the Launder–Sharma low-Reynolds number k–ε model. The latter simulation results provide the most unstable wavelength for the turbulent water annulus. Our study also shows the following. The maximum wave growth rate for a turbulent water annulus is significantly higher than for a laminar water annulus. The most unstable wavelength in the simulations is about 25% smaller than in the experiments. The wave amplitude for the different wavelengths in the simulations is typically 17% lower than in the experiments.