gravity and boundary condition

Angela

hi everybody I am writing a code(based on FVM and Roe scheme) for steady 2d incompressible flow through a plate.But I have to add the gravity force in to the original equation.That means that the pressure is the total pressure,including dynamic pressure and hydrostatic pressure.

Now for the boudary condition of plate,i give it no slip condition.For gravity force I give nondimensional hydrodtatic force as -rou/fn/fn*volume,and the initial pressure is also the hydrostatic pressure that is rou*(z0-y)/fn/fn.The first calcaultion seems that the residual for the interior points are right.But for the points around plates,I have used ghost points to calculate the velosity,as uc=1.0,ug=-1.0.vc=0,vg=0.and pressure difference is just hydrostatic pressure difference.

There are some residuals for u direction which is not compatible with physical truth.

I am lost.Anybody please give me an answer?Or any reference aboout adding grvity force?

Thank you!