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Balaji Viswanadh G

Infinite Box Dependency on Results in Flux 3D

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Hi, 

 

I have come to learn that, in Flux 3D  simulation results vary drastically with change in infinite box size. This, I think may be due to change in mesh. 

Are there any guidelines in terms of what an ideal mesh setting should be and/or what an ideal infinite box size should be for a typical 3D simulation?

In my models,  I have been using 'Mesh Domain' option to mesh the geometry. 

Please advise. 

 

Best Regards

Balaji 

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Hi Balaji!

 

Until recently I used to made the same slip.

When you define the Infinite box I learned that (if I am not mistaken) the influence of the parameters of the defined geometry doesn´t have to collide with the infinite box internal limit.

I, for one, display the isovalues of the magnetic flux density and if the darkest colour is touching the infinite box I consider that it's correctly defined as indicated in the next picture:

(Yes, this is a 2D simulation, but I do the same with the 3D)

 

image.thumb.png.58968862b257c9eae02495eba1ce9b5c.png

 

Best regards, 

Andoni

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Hello Balaji,

In fact, if your values are changing when you change the infinity box size, that means that it is to small for your problem. It can be a meshing problem but, most probably, the reason is that your physics is not well represented with such small infinity box.

As Andoni says, the infinity box limits should be “long enough” your device. In other words, flux should be quite low when reaching the infinity box boundary, otherwise it is too small.

Given fixed rules to decide when a box is “big enough” is not a simple task, and there are not infallible rules, since it depends on device geometry and physics. For example, if you are representing a motor surrounded by a ferromagnetic stator, most of the flux will be confined inside the machine, with very low leakage flux going to the air, in this case you can define a small infinity box. On the contrary, if the device is on air with no ferromagnetic material limiting it, box sized required will be higher.

As a rule of the thumb, we advise to establish the internal size of the infinity box between 1.2 and 2 times the device radius.

Best regards,

Alejandro

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Thank you very much for your kind guidance @Alejandro Rodríguez and @Andoni Garcia. Really appreciate your help. I believe it takes at-least a couple of iterations to get the right size of infinite box for a given geometry. Glad I learnt that.  I have now come to appreciate that infinite box size is entirely dependent on the geometry and physics. Thank you very much for your guidance again. 

 

Have a wonderful day ahead

Balaji

 

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