[aspect-devel] compressibility in 2d

[Jonathan Perry-Houts]

Hey Menno,

I'm pretty sure the reason is that 2d models are supposed to represent a
slice through an infinite-depth 3d model, so the equations do not
change. This bothered me at first too, and that's how I justified it to
myself. Hopefully someone else can confirm or deny that justification.

-JPH

On 02/10/2017 06:04 AM, Menno Fraters wrote:
> Hello all,
> 
> 
> I have been looking at the formulation of the compressibility in aspect
> and in the manual there is a 1/3 in front of the div(u)*1* in equation
> 1. I would expect that this is only valid in 3d, because I think it
> stems from the deviator which is deviator(*epsilon*) = *epsilon* - 1/dim
> * trace(*epsilon*)*1*. So I would expect it to be 1/2 in 2d. But I found
> that in the code it is hardwired as 2/3 (where the 2 comes from I
> understand).
> 
> 
> Can someone explain me why this is 2/3 and not 2/2 = 1?
> 
> 
> Many thanks!
> 
> 
> Cheers,
> 
> 
> Menno**
> 
> 
> 
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