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 Belete Kiflie June 2, 2006 11:17

Single rotating reference frame

Dear all,

I have a domain which contains a rotating impeller. But the domain consists of non-rotating fluid zones before and after the impeller. I used a rotating reference frame attached to the fluid zone. But in the velocity vector plot of the solution, it appears that the velocity of the elements in the non-rotating part of the fluid have components in all directions. How can I fix this problem?

 myang June 2, 2006 11:21

Re: Single rotating reference frame

I think sliding mesh may be a better choice.

 sam June 2, 2006 15:35

Re: Single rotating reference frame

how u can say this . it depends on need and requirements

 Ben Lamek June 5, 2006 14:55

Re: Single rotating reference frame

she might use multiple reference frame, but usually MRF results are no good because:

If you do 5 or 6 MRF simulations of the same geometry but with the rotating parts fixed in a difference position for each simulation: each 5 simulaiton has different result. Try it you will see!

To avoid this you need to average the 5 (or 6) simulations when post-rpocessing or use sliding grid.

B.L.

 Razvan June 7, 2006 04:29

Re: Single rotating reference frame

If you will plot absolute velocity vectors in front of the impeller you should see only axial direction vectors (if you set such inlet boundary condition!), but after the impeller absolute velocity vectors will not be axial if you don't have a stator blade stage to straighten the flow (the impeller will add a circumferential and a radial component for velocity).

On the other way, if you will plot relative velocity vectors, then pretty much all vectors in the flow domain will have all-direction components. It is perfectly normal.

Try to think more deeply about these concepts: absolute and relative velocity!

Razvan

 Belete Kiflie June 7, 2006 08:19

Re: Single rotating reference frame

Dear all,

Let me put my question in this manner. What will happen if I used a rotating reference frame attached to the fluid to simulate a flow through a pipe. Is it possible to do so in fluent theoretically and yet get meaningful result?

In my domain, there is part of the fluid which is outside the influence of the rotor to get a relatively developed flow condition at the rotor inlet.

Best regards

 sam June 18, 2006 03:38

Re: Single rotating reference frame

r u sure. can u give some reference or any result u have done ur self .

i am will gratful to u

regards sam

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