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-   -   Adiabatic and Rotating wall (Convection problem) (http://www.cfd-online.com/Forums/cfx/23911-adiabatic-rotating-wall-convection-problem.html)

ParodDav April 26, 2007 03:43

Adiabatic and Rotating wall (Convection problem)
 
I'm trying to solve a Thermal and Fluid Dynamic problem where there are the following issues. I have a rotating wall (which is a rotor). This steel rotor has its own thickness (so, I'm solving a conduction problem too). Outside this rotor, I have the cooling flow (air) which has to cool down the rotor wall (so, on this side, I have a convection problem). When I setup the boundary conditions and I consider this rotor rotating wall, I should choose (for the thermal side)one of the following options (but no one is correct for my problem): 1. Adiabatic (my problem is not adiabatic) 2. Heat flux (I don't know it, because for my problem the conduction problem is not mono-directional only; the heat transfer is also present through different stationary parts around the rotor) 3. Temperature (I don't know it, because it is the result I would like to find) 4. Heat transfer coefficient (I cannot setup it, because it is a function of the flow field from the convection point of view).

How might I setup a rotating and non-adiabatic wall (at the same time) as boundary condition? Does anybody can help me, please? I hope so!

Have a good day !!! Davide

Glenn Horrocks April 26, 2007 18:18

Re: Adiabatic and Rotating wall (Convection proble
 
Hi,

The rotor to fluid interface should be an interface, not a boundary condition.

Glenn Horrocks

ParodDav April 27, 2007 03:21

Re: Adiabatic and Rotating wall (Convection proble
 
Dear Glenn, thank you very much. Your suggestion is completely right but, in my case, a problem persists because I don't know if I can define an interface as following: "rotating surface" and "interface between fluid and solid" at the same time. If yes, I don't know how I might do it. Thanks again Have a good day Davide


Stumpy April 27, 2007 09:02

Re: Adiabatic and Rotating wall (Convection proble
 
You shouldn't have a rotating surface. Rotating walls are only valid if the wall velocity is tangent to the wall. In the case of a rotor you have a normal component to the wall velocity - in other words the wall "pushes" the fluid. Therefore you must use a rotating fluid domain around the rotor; the rotor wall will be stationary in the rotating frame. Your shroud can be a counter-rotating wall, since it will not have a normal component to the wall velocity.

ParodDav April 27, 2007 09:28

Re: Adiabatic and Rotating wall (Convection proble
 
I would like to thank you very much for all your suggestions.

I'm asking if I might consider another opportunity I saw...but I'm still investigating on it. I can consider every part of my domains on a stationary frame (this is the way I used for meshing my domains, specifying every single material). I can define a solid-fluid interface between fluid (air) and rotor solid. At this point, the following things happen: 1. Creation of the domains interface (we can see it on the bottom side of the pre-processing window...where also periodicities and GGIs are defined) 2. At the same time, I can see the interfaces effects on each domain. I mean: I see the interface as "boundary condition" on the corresponding domain (with the same name I gave to the interface but with the different side number specified). 3. If I open this "kind of boundary condition", I can specify a wall velocity value on the corresponding wall (my rotor wall but...on the fluid side).

But another problem might persist ! Is it numerically correct? How does the code solve this kind of setup?

I hope you can apologize me for my wild definitions. :)

Thanks Davide


Glenn Horrocks April 29, 2007 19:13

Re: Adiabatic and Rotating wall (Convection proble
 
Hi,

If the domains on both sides of an interface are rotating then doesn't the interface rotate as well?

Glenn Horrocks


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