Slug translational velocity, described as the superimposition of the maximum mixture velocity in the
slug body and that of the drift velocity, is a critical parameter for two-phase pipe flow. Accurately
determining it is important for the energy-efficient design of oil and gas pipelines. A survey of the
literature revealed that existing prediction models of this parameter were developed based on observation
from low viscosity liquids (of 1 Pa.s or less). However, its behaviour in pipes transporting higher viscosity
oils is significantly different. In this research work, new data for slug translational velocity in high-
viscosity oil-gas flows are reported. Scaled experiments were carried out using a mixture of air and
Mineral oil of viscosity ranging from 0.7 to 6.0 Pa.s in a 17-m long horizontal pipe of 0.0762 m ID.
Temperature dependence of the oil’s viscosity is given as ? = ?0.0043T 3 + 0.0389T 2 ? 1.4174T +
18.141. The slug translational velocity was measured by means two pairs of two fast-sampling Gamma
Densitometers with a sampling frequency of 250 Hz. For the range of experimental flow conditions
investigated, increase in liquid oil viscosity was observed to strongly influence slug translational velocity.
A new predictive correlation incorporating the effect of viscosity on slug translational velocity was derived
using the current dataset and incorporating those obtained in literature with oil viscosity ranging from
0.189–6.0 Pa.s. for horizontal flow. A comparison by statistical analysis and validation and of the new
closure relationship showed a remarkably improved performance over existing correlations.