CFD Online Discussion Forums - OpenFOAM representation for a partial equation

Dear Foamers,

I am encountering a problem about how to write openfoam representation for a partial equation.

$\frac{\partial c} {\partial t} + \nabla . ({\vec u - u_s \frac{\vec g} {| g |}}) c$ $=\nabla . ( {\nu_t \nabla c} )$

u_s is the settling velocity for particle, c is the concentration

In general, the second term on the left hand of the equation is written fvm:div(phi, c) if settling velocity is omitted. phi is the flow through the cell face. Since settling velocity exists, i have no idea how to write the openfoam representation for the above equation.

Any help is grateful.

Best