Gas–liquid slug flow in a horizontal concentric annulus, a comparison of numerical simulations and experimental data

•Pressure gradient and sluq frequency in a horizontal concentric annulus was studied.•Slug frequency matches experiments to within 9% for the 3 and 7 m domains.•The best match for pressure gradient results were achieved in the 3 m domain.•Domain length should be near an integer multiple of the slug to slug distance.