[alisina-s]

Hi everyone
I want to solve the equation ∂ t( ρ )= −div (vκ) + qv beside other equations which in this equation ρ ,q and v are volscalarfields and κ is a volvectorfield,
I was thinking to implement like this
fvm::ddt(rho) = ( A*(-(fvc::div(v,K))) + v*q) ;
but it seems that the div(volscalarfields,volvectorfield) is not defined because I have some errors regarding that.
and also I was thinking to write this equation like
rho =rho+dt( ( A*(-(fvc::div(v,K))) + v*q)) ;
I also like to know the difference of these 2 types,
Does anyone have any experience which can help me?
Thank you guys in advance,