Rotational flow mid-domain
 

I'm looking to try and add a rotational flow in the middle of a domain if possible.

Essentially, I have a CFD model with a turbine in the middle from which I can know the angle of the flow through a specified cross section, however I'm looking to try to have a relatively quick look at the effects of some of the upstream geometry without having to introduce modelling of the blades themselves as an initial study.

I realise I can set rotational properties at a boundary but I'd like to have the boundary a little further away from where the blades would be, ideally.

I'm historically a Fluent user and have only just transitioned to CFX after moving jobs, so any additional info is much appreciated.

Sounds like a momentum source term. You will have to derive the desired thrust and flow rotational components, and you can apply them as a momentum source term on a subdomain.

So it'd be possible to apply the subdomain to just one face? Had a quick look at them and it seems to only let me select whole volumes, rather than one face/plane. Possible I set the geometry up wrong to be honest, as I said I'm pretty new to CFX.

If you are trying to put a device to move the flow in the middle of your domain then you don't want a boundary face there. The momentum source approach is applied to a subdomain inside your domain and does not require boundary faces.

If this is not what you are looking for please post an image of what you want to do so I can understand your application.

I realise that I don't want a boundary in the middle of my domain, I was just hoping to be able to impose a rotation on a plane rather than a volume (which subdomains seem to be) but a volume could work.

I've attempted the subdomain method but am unable to upload images due to a workplace IT policy, unfortunately.

What I notice is that the swirl in flow is only imposed downstream of the impeller volume subdomain, whereas I'm expecting that there should be some kind of entrainment realistically.

I do not understand this comment. The momentum source term approach would not generate swirl downstream of the source term volume, it is generated at the volume. Please post an image of what you are getting to explain it better.


I don't understand that comment either. Can you post an image to explain what you mean?