Changing the default equation in level set model

Hi,

I was exploring Level-set method for 2 phase laminar flow and wondering if I can change the default equations according to my wish. If yes, how can I change the equation in pressure boundary condition

[-pI + µ(∆u+(∆u)T]n = -(pˆo)n
(pˆo)<=po

to

µ(d2v/dx2+ d2v/dy2+ d2v/dz2)=0

Thank you