Uneven Phase Split in Tee Junctions

Does this look like a typical tee junction?


A careful look reveals an oddity: the vapor fractions coming out of the through-run and the branch don’t match. This is because VMGSim dynamics is now able to model uneven phase splitting in tee junctions.


While it is often easy to assume that a splitter has no effect other than to divide fluids, in reality the liquid will preferentially choose either the branch or the through-run. 

Properly modeling this behavior has many applications. In gas pipeline networks, for example, accumulated liquid will preferentially choose one route over another, leading to specific areas with a larger liquid buildup than others. A video on YouTube discusses this and other related phenomena. 


This image, from the video, shows a predicted liquid path from the beginning of the pipeline network to the terminal location. If the liquid had split evenly at each junction, the liquid would be dispersed across many terminals, rather than being focused in one. Predicting the liquid path is important so that the liquid can be properly handled.


To enable this feature, open the Advanced frame on the splitter form, and select a Phase Split Method.



There are three options:

  • Equal - The default method, where the phases will split evenly.
  • Hart/Wren - The Hart method [1] for horizontal splits, and the Wren method [2] for vertical splits.
  • Kin Energy - Calculates the split based solely on the kinetic energy ratio of the vapor to the liquid in the inlet.

The Vapor and Liquid Split Fractions are the mass fractions of the vapor and liquid leaving in the branch. 

Comparison to Experimental Results

VMG predictions have been overlaid on experimental results [1], and demonstrate remarkable agreement. 


This feature can also be used with impacting (opposing-flow) tees, and accounts for the orientation of the branch.


The ability to predict uneven phase splitting in tee junctions is just one part of VMG’s commitment to developing state-of-the-art tools for upstream analysis and for process simulation in general. This feature is available in VMGSim 9.5 build 66 and later.

For more information please contact your local VMG office.

Kyle Macfarlan, B.S., M.S., Dynamic Simulation Developer


  1. Fortuin, J. M. H., Hart, J. and Hamersma, P. J. (1990), Route selectivity for gas-liquid flow in horizontal T junctions. AIChE J., 36: 805–808.
  2. Wren, Elisabeth Mary Katie (2001) Geometric effects on phase split at a large diameter T-junction. PhD thesis, University of Nottingham.
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