Theta values not summing to one with cutcell for w momentum

MFiX Bug report
#1

On lines 933 and 937 of cartesian_grid/get_alpha.f, I believe there is a bug. The current lines are:

Theta_W_bn(IJK) = ONE - Theta_W_bn(IJK)

but I think they should be
Theta_W_bn(IJK) = ONE - Theta_W_tn(IJK)

This is causing the _bn and _tn values not to sum to one which is causing problems with the flux calculations and ultimately giving rise to mass imbalance around the surface of a cut cell object (I think). We caught this trying to verify our tensorflow code against mfix. Please let me know if you agree and will correct.

#2

Good catch Dirk! We should be able to squeeze this fix for 19.1

#3

Update:
Gitlab Issue#841
Merged in develop
Closed issue
Fix available in 19.1