# Boundary Condition set up for Rotor help!

Question asked by Jason Lee on Dec 12, 2013
Latest reply on Dec 13, 2013 by Jared Conway

Hello,

I was wondering if someone could help me with an issue i've come across concerning the proper set up of boundary conditions for a flow simulation of a rotor/propeller I designed.

I attached an image that shows the scenario I am trying to create for my rotor.

So in this scenario, there are two pistons (striped black boxes) that will contract to the striped red boxes position. When the pistons are expanded, there is 6L of a liquid between the pistons and after it is contracted, there will be 2L of liquid remaining in the space seen in the diagram. In total, there should be 4L of the liquid that should go through the center pipe outlet. The pressure at the pistons expanded state will be 5 mm Hg, the pressure of the contracted state is 90 mm Hg and the pressure at the outlet is 100 mm Hg. What I would like to do is add some type of rotor/propeller rotating at 5,000 rpm and placed at the start of the outlet (as seen in the diagram) that will pump the remaining 2 L during the contracted state towards the outlet so that the total volume that reaches the outlet will be 6 L rather than only 4L. The inlet and outlet regions I defined in the flow simulation are seen in the diagram as well (the blue circles). Also assume that the height of the fluid does not affect pressure.

How should I set up my boundary conditions for this scenario?

Some of the appraoches i have tried are:

1. The inlet lid with a total pressure (environmental pressure) of 90 mm Hg and the outlet lid with a static pressure (environmental pressure) of 100 mm Hg.

2. The inlet lid with a volume flow rate of 4 L/min and the oulet lid with a static pressure of 100 mm Hg.

Some additional questions I have are:

1. Will the 4L volume that is contracted by the piston be affected by the rotor?

2. How can we create head flow curve (HQ curve) for this rotor?

Any help will be much appreciated!

Thank you

Jason