Effect of liquid viscosity on flow patterns of gas–liquid two-phase flow in a horizontal pipe

► We investigate the effect of liquid viscosity on the flow patterns of gas–liquid two phase flow in the horizontal pipe. ► Flow patterns observation is carried out for a horizontal pipe of 20 mm inner diameter. ► Viscosity of water solutions varied from 1 to 11,000 mPa s with Newtonian viscosity. ► The results obtained showed that the flow patterns strongly depend on the liquid viscosity. ► These were not agreement with published theory for the prediction of flow patterns by Taitel and Dukler.