Mismatching drag model call


Type of issue
Possible multiple bugs:


  1. There is call for Tang drag model (DRAG_TPKKV) when the case is for Tenneti drag model (TGS) inside des/drag_gp_des.f
     CASE (TGS)
  1. Mismatch in equation for Tenneti drag model (DRAG_TGS) inside drag_gs.f? The code has

F = F + phis**3d0*RE*(0.95D0+0.61D0*phis**(1.0d0/3.0d0)/(1.0-phis)**2)

whereas from Tenneti et al (2011)

The phis**(1.0d0/3.0d0) term should be phis**3.0d0 ?

  1. The correlation of Tenneti et al (2011) reports drag force including average pressure drop due to buoyancy whereas Tang et al, Beetstra et al, etc report drag force without it. However, upon comparing subroutines DRAG_TGS(...) and DRAG_TPKKV(...) (or DRAG_BVK(...)), both are just returning F*F_STOKES. However, ideally F_TGS is equivalent to F_TPKKV/EPg (likewise F_BVK/EPg).

In other words, from Tang et al (2015)

Tenneti reports F_{gs} whereas Tang / BVK etc report Fd.

Thanks for the detailed report. It may take us a little while to review this but we want you to know we appreciate your careful examination of the source code and the literature.

Hi Sathish!
The call to FRAG_TGS was fixed in the 23.1 release. We are trying to figure out if the typo is in the code or the paper.