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October 25, 2005, 18:24 
Can CFX5.7 solve axisymmetric problem in 2D?

#1 
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If it can, how to asign the boundary condition in the axisymmetric plane (zr plane)? I saw that the existing boundary types in CFX5.7 only include inlet, outlet, opening, wall, and symmetric. Obviously, axisymmetric face is different from symmetric face.
Thanks! Xueying 

October 26, 2005, 06:42 
Re: Can CFX5.7 solve axisymmetric problem in 2D?

#2 
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> Obviously, axisymmetric face is different from symmetric face
[list]Why ???? 

October 27, 2005, 06:10 
Re: Can CFX5.7 solve axisymmetric problem in 2D?

#3 
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Hi Rui,
Do you think it is the same: 1. Cilinder 2. Infinite block You said that in both cases one should use symmetric face. But it is well known that the solution, for example, of the heat transfer and temperature profile is different for the cilinder and the block. For cilinder we use log function, while in flat block case  linear. 

October 27, 2005, 08:24 
Re: Can CFX5.7 solve axisymmetric problem in 2D?

#4 
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Periodic interface should be used on axisymmetric face.


October 27, 2005, 09:34 
Re: Can CFX5.7 solve axisymmetric problem in 2D?

#5 
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Hi,
In CFX (where you cannot do a true 2D analysis) to simulate an infinite block you would have two parallel faces where you would apply symmetry BC, while to simulate a cylinder you would have a slice of that cylinder (let's say ~5 degrees) and would apply symmetry BC to the two slice faces (which are not parallel). In a symmetry BC, the normal velocity component is set to zero (Un=0), and the variables gradients normal to the boundary are also set to zero (d_phi/d_n = 0). This is valid for an axissymetric problem. You may also think that a cylinder is made up of 72 slices of 5 degrees, and if the problem is axyssimetric, all the 72 slices will have the same flow, temperature, etc patterns. Thus there is symmetry at each of the slices faces. Take at look at the Documentation, Solver Modelling, Advice on Flow Modelling, Modelling 2D Problems. Take also a look at Tutorial 13 (Reacting Flow in a Mixing Tube), where the tube is modelled as an axisymmetric section. Regards, Rui 

October 27, 2005, 09:52 
Re: Can CFX5.7 solve axisymmetric problem in 2D?

#6 
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Hi,
The Documentation says: "For axisymmetric 2D geometries, apply symmetry conditions to the hightheta and lowtheta planes unless there is swirl anticipated in the flow, in which case 1:1 periodic connections should be applied instead. Do not use GGI periodic connections; doing so will hurt accuracy. The extrusion rotation angle for axisymmetric geometries should be small (eg. 1 to 5 degrees)." 

October 27, 2005, 09:53 
Re: Can CFX5.7 solve axisymmetric problem in 2D?

#7 
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Yes, I agree, if we mesh the 5degrees slice with symmetry on both sides  it is Ok! But it is pity we have no possibility to mesh 2d picture and solve the cilindrical problem.


October 27, 2005, 09:57 
Re: Can CFX5.7 solve axisymmetric problem in 2D?

#8 
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Hi,
CFX "just" has a 3D solver. 

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