LIQUID_FLOW: Replace darcy_gravity by specific_body_force
Description
Currently, the LIQUID_FLOW
process takes the gravity into account via setting a positive scalar. Thereby it is assumed that gravity acts in the opposite direction of the one of the coordinate axes.
In line with the other processes the definition of a signed body force should be preferred instead.
Current implementation:
<darcy_gravity>
<!-- axis_id: 0, 1, 2 -->
<axis_id> 0 </axis_id>
<!-- g>=0. g=0: no gravity -->
<g>9.81</g> <!--m/s²-->
</darcy_gravity>
Desired implementation:
<specific_body_force>0 -9.81</specific_body_force>
However, many examples then need to be adapted (automatically). Maybe it's worth it.