KNOWN ISSUE: Non-drag forces and GGI interfaces (Class 3 Error)
When using some advanced multiphase physics models, especially the virtual mass force, numerical inaccuracies at GGI interfaces may be greater than in other applications. If possible, GGI interfaces should be avoided in such applications. If used, please check the solution close to the GGI interface.
The discretisation of the virtual mass force at GGI interfaces is different from that used in the interior. This conflict can lead to large errors at the GGI interface, which may not be noticed by the user.
Using the expert parameter setting 'virtual mass force option = 0' can avoid the problem at the expense of overall robustness and accuracy.
ANSYS CFX Release 14.0 (by documenting this behaviour).