Problem with SIMPLE algorithm
 

I have written finite difference SIMPLE algorithm to solve the Navier Stokes equation in Matlab. My problem is that I don't know how to specify boundary condition for Poisseuille flow. If i specify inlet velocity, the solution tend to blowup. I suspect that somehow I don't specify the pressure boundary correctly.(In the matlab code if I specify the pressure boundary for inlet and outlet but no velocity boundary at the inlet, the solution does not blow up but the problem is that I cannot control the inlet velocity) I managed to solve Couette flow and Driven cavity problem with no problem though..Care to advice me on what I have to do. I attached also the code for the SIMPLE algorithm that I write..

boundary condition
 

You are solving flow in a duct basically. Use velocity inlet and pressure outlet bc. Which grid r u using ? colocated or staggered

I'm using staggered grid..if i set the inlet velocity to v=1 and pressure outlet p=0, how about inlet pressure, do i need to extrapolate it with inner pressure?

yes exactly. p(1).value = p(2).value where p is the pressure and numbers indicate the node location

hmmm..it's that simple? i'll try it..
for anyone who has run my code, do comment on what I have done..thanks in advance.. :D