# forceModel_ArchimedesIB command¶

## Syntax¶

Defined in couplingProperties dictionary.

```
forceModels
(
ArchimedesIB
);
ArchimedesIBProps
{
gravityFieldName "gravity";
voidfractionFieldName "voidfraction";
twoDimensional;
treatForceExplicit switch1;
};
```

*gravity*= name of the finite volume gravity field*voidfraction*= name of the finite volume voidfraction field*twoDimensional*= optional keyword for conducting a two dimensional calculation*switch1*= (optional, default true) sub model switch, see*forceSubModel*for details

## Examples¶

```
forceModels
(
ArchimedesIB
);
ArchimedesIBProps
{
gravityFieldName "g";
voidfractionFieldName "voidfractionNext";
}
```

## Description¶

The force model performs the calculation of forces (e.g. fluid-particle interaction forces) acting on each DEM particle. The ArchimedesIB model is a model that calculates the ArchimedesIB’ volumetric lift force stemming from density difference of fluid and particle. This model is especially suited for resolved CFD-DEM simulations where the particle is represented by immersed boundary method.

## Restrictions¶

Only for immersed boundary solvers.