An Investigation of the Influence of the Gravity Field on the Interface of Two Immiscible Liquids—A Computational Study Comparing Prediction with Experiment

Abstract

The flow of two immiscible liquids in a tube was investigated using computational fluid dynamics (CFD). This work is a first step towards investigating the influence of a variable gravitational field on the interface between the upper and lower phase of immiscible solvents as used in counter‐current chromatography (CCC). Initially the tube was positioned horizontally with the heavier fluid (lower phase) at the bottom and the lighter fluid (upper phase) on the top. Then the tube was suddenly tilted to a fixed inclination angle α. The flow field was initially exposed to a standard 1g gravity field (case 1). Subsequently, runs for a 2g and 10g gravity vector were performed (cases 2 and 3, respectively). Predictions for case 1 compared favorably with experimental results, although it was noted that there was a slight time slippage. The numerical results for the cases 2 and 3 showed that the higher the gravitational force the sooner distinct waves occur at the interface and the more disturbed the interface becomes in time. The interface surface area becomes minimal more quickly in the high gravity case due to the fluids moving more quickly to their respective ends, hence reducing the time when mass transfer between the phases is possible. However, mass transfer is still likely to have been enhanced due to the better mixing as a result of the highly disturbed interface. These encouraging results indicate that CFD could become a powerful tool in understanding the complex nature of the fluid dynamics in coil planet centrifuges and countercurrent chromatography.

Keywords:

• Computational study
• Interface
• Gravity field
• Numerical model
• CFD
• Experiment
• Visualization
• Two‐phase flow
• Stratified
• Immiscible liquids