[EmmTheof84]

Hi All

I am trynig to perform a stady state simulation on a small fan, 90mm nominal diameter.
I have set up 3 fluid domains, one upstream of the fan, one for the rotating region, encompassing the fan impeller, and one downstream of the fan with 12 hydraulic diameters in length.
The fan is rotating clockwise at 13000 rpm
My simulation converges (I still need to refine the boundary layers for y+), however when I go to post processing the pathlines deflect counterclockwise the instance they reach the interface of the rotating region and then again deflect clockwise downstream.
The downstream behaviour is what I would expect, with a swirling motion that will need some time to normalise.

I have set my rotating region to Frame Motion, rotating about the Z axis, and "absolute" in the Relative to cell zone option

I have also set the rotating region wall as a stationary wall

The Impeller has been set up as a wall in the boundary conditions and I have tried having it rotating along the Z axis with an Absolute motion, I have also tried having it as a Stationary Wall relative to the Adjacent Cell Zone and Finally I have tried having it as a rotating wall Relative to the Adjacent Cell Zone. The results in all 3 options are the same when it comes to the pathlines.

I would expect the pathlines to be deflected clockwise and have the same swirling motion in the rotating region as well as in the downstream region.

Inlet is a pressure inlet, outlet is a pressure outlet and due to the close interaction between the blade tip and the wall I have selected the k-w SST turbulence model.

Am I missing something, or doing something wrong?

Pathlines.jpg

[EmmTheof84]

Originally Posted by EmmTheof84

Hi All

Am I missing something, or doing something wrong?

Attachment 81176

It appears I have to plot my results using the Stn frame option for velocity and pressure. Then all is well.

I've lost 2 days thinking I was doing the setup wrong, read countless papers and manuals for Fluent's current and previous versions and it was that simple.