I am trying to model two cases of the flow of water through a geometry at 1m/s. In the first case I would like the water to be pushed through the geometry and I have set my boundary conditions to a velocity inlet of 1m/s and a pressure outlet at atmospheric, however, in the second case I would like to suck out the water at the same velocity (1m/s). What bounday types should I use? Can I have a velocity inlet of (-1m/s). Or should I use a pressure inlet and outlet in both cases? Any advise?

In your 2nd case you could use outlet as a velocity inlet setting -1 m/s (as u said) or you could set outlet as an outflow... it will give same mass flow rate.

Alamgir

Hi,

If I was to set the outlet to an outflow as suggested... Will that not give me the same conditions as case 1 where the water is being pushed through. Basically I want to see if there is any differences (forces on the walls) if the flow was pumped through or sucked through? Or would they be the same? Any thoughts?

No, it'll not be same as case1, for the boundary condition when u set outflow, it actually mean volume flow rate remain same, as much as water enters thru inlet, same amount of water will pass no matter what is the pressure. Pressure would be different, case1 inlet pressure will be more than atm, this case pressure at outlet will be less than atm. So pressure distribution will be only different.

Alamgir