2.2.8.2 fix addforce
fix addforce is used to add user-specified force to a certain group of particles.
Syntax:
fix id group-id addforce options-keyword
- id: user assigned name for this fix
- group-id: the fix is applied only to the particles in this group id
- options-keyword: drag_stokes, buoyancy
- drag_stokes μ
- buoyancy dimension ρ g
Examples:
fix drag water addforce drag_stokes 1.0950 fix floating water addforce buoyancy z 0.789 9.81
Description:
If option-keyword drag_stokes is used, the user-defined viscosity (μ) will be used to calculate the drag force
added on particles in the specified group based on Stokes’ law:
where R and v are particle’s radius and velocity, respectively.
If option-keyword buoyancy is used, the buoyancy force will be added to particles in the specified group along x,
y or z “dimension”:
Fb = ρg πR3 | | |
where ρ is the density of the liquid and g stands for the user-defined gravity. A negative value of g will indicate
an opposite direction of standard Cartesian coordinate.