How to set gravity in porous media "thm_example"?

[zhang-rite]

Hi

Currently the example (modules/porous_flow/examples/thm_example/2D.i) does not consider gravity. I have attempted to set it by setting "gravity = '0 -9.8 0'. However, it seems the gravity effect does not appear--there is no difference in fluid saturation whether I set gravity on or off. I expect the gas phase would move to upper regions.

How can I correct this? Thank you!

Modified file with following modifications:

[Mesh]
type = GeneratedMesh
dim = 2
nx = 50
bias_x = 1.2
xmin = 0.1
xmax = 5000
ny = 50
ymin = 0
ymax = 5000
[]

[GlobalParams]
displacements = 'disp_r disp_z'
PorousFlowDictator = dictator
gravity = '0 -9.8 0'
biot_coefficient = 1.0
[]

[zhang-rite]

Oh, it is just due to I did not notice the setting of permeability field in the original 1D problem.

permeability = '2e-12 0 0 0 0 0 0 0 0'