[FrankS]

Hi All,

I am modelling a machine consisting of a high-speed (Re-independent) rotor enclosed within a vat. The working fluid is water. I have been using the frozen rotor approach to account for rotor rotation. Buoyancy does not affect the flow field so I have not included it yet (it will be important in the next step though and that is why I mention it). I have been tweaking the design of this machine based on a number of flow simulations and I am now quite happy with the flow field.

One of the important functions of this machine is to separate particles suspended in the water. Low density particles float up and high-density particles sink down. Obviously then, I need to include buoyancy if I am to introduce particles to the flow domain. When I include buoyancy, the gravity vector will be perpendicular to the spinning rotor's axis of rotation. This means I can't use the frozen rotor method anymore and now my simulations will go from 2-hours each run to 2-weeks as I must adopt the full transient method.

I only need to inject a small number of small particles into my simulation domain and one-way coupling is plenty good enough. I understand that one way coupling is calculated after the fact as the particles do not influence the flow. Is it possibly to change the gravity vector direction just for the particles in CFD post so that I could use the frozen rotor method to develop the flow? I would even be happy if I could introduce particles into a snapshot of the flow field at a given time and just see where they go based on the static snapshot.

I am looking for a quick way to run simulations so that I can make the final tweaks to my design before I go all in and run a full transient simulation for two to three weeks.

Sorry about the lack of details on the machine itself. It is novel and it should offer a massive performance improvement over existing machines so I am keeping it secret for the moment. Any help is appreciated.

Frank