[thrsdy]

Hi!

This is my first post here, I hope someone can give me help in my problem:

I am modelling a rotating cavity in CFX, similar to this, with a superimposed radial inflow. My geometry differs in the following manner;
The left-hand disk extends all the way down to a central shaft.

The inlet is the same as in the schematic. Air enters the central slot at the periphery of the cavity, flows inward radially turns right and is expelled through a annular hole in the center of the right-hand disk (outer radius 36 mm, inner radius 12 mm). This flow is imposed using blowers.

I am having issues posing reasonable boundaries and would like some guidance.

What I know:

1. Total Pressure at inlet
2. Swirl at inlet is 1 (inlet flow tangential velocity is the same as periphery of disks)
3. The mass flow through the cavity is around 9 g/s
4. Angular velocity of disks
5. Geometry of disks

The main issue I'm having is posing a good outlet boundary, as the flow is highly tangential and I get backflow very easily.

What I am using so far is an L-shaped domain in the rotating reference frame. A Total Pressure inlet with the direction set to normal to boundary. At the outlet (extended roughly 7 times the distance of last obstacle) I have a "Radial Equilibrium" average static pressure outlet.

The problem with this is that I have to vary the pressure until I get the desired mass flow, as the pressure here is unknown to me. Needless to say, this is painful

Is my outlet boundary even reasonable (I am not sure I understand the radial equilibrium outlet correctly)?

Any guidance or comments would be very much appreciated!