question about phi
 

hello everyone
If my momentum equation is:
ddt(U) + div(UU) = div(tau) - grad(p) + F
then the term
phi = (H/A)_f . S + (F/A)_f . S
or
phi = (H/A)_f . S
Do i need to add the term (F/A)_f . S:confused:
Thank you very much

Regards.

zakir