Dimensionless oil-water stratified to non-stratified flow pattern transition

In this paper a unified approach for the transition criterion from stratified to non-stratified oil-water flow is explained. The inviscid Kelvin-Helmholtz stability (IKH) analysis for gas-liquid flow was extended for liquid-liquid flow such that it is exactly matching the liquid-liquid stability analysis from literature. The effect of the imposed factor on the IKH is discussed in detailed in this paper. A dimensionless stratified to non-stratifed transition criterion is developed which gives more insight and clear understanding of the real parameters affecting the stratified to non-stratified flow pattern transition. The dimensionless form of the criterion enable sub-classifications of the oil-water stratified flow into the well-known sub-regimes, namely, Stratified (ST), Wavy Stratified (SW) and Stratified with mixing at the interface (ST-MI). A new prediction approach for the transition from ST to ST-MI based on Froude number is proposed and showed an excellent agreement with experimental data from literature for near-horizontal pipe configurations.