[aspect-devel] ascii data format for "chunk" velocity boundary conditions

[Rene Gassmoeller]

Hi John,


On 07/04/2017 06:40 AM, John Armitage wrote:
> Dear all,
>
> Therefore, does ASPECT expect to read in velocities in Cartesian 
> geometry? Or is velocity_x and velocity_y just a simple convention for 
> perpendicular and tangential? x goes to longitude and y goes to radius 
> or visa-versa...
>
> On a more general point, are the governing equations always solved in 
> Cartesian coordinates, and when we choose a spherical set up gravity 
> simply points to the origin?

Aspect internally solves everything in Cartesian coordinates, and 
spherical geometries are simply expressed in a Cartesian system (i.e. 
depth or gravity points in the direction of the origin).
That being said there are a few exceptions for user input where it is 
more convenient to use spherical coordinates, one of those exceptions is 
the ascii data plugin. In spherical geometries the coordinate columns 
are interpreted as spherical coordinates (radius, longitude, 
colatitude), but the velocity columns are still in cartesian velocities 
(velocity_x velocity_y velocity_z). I agree that this is slightly 
inconsistent, but it seemed the most intuitive to use and implement at 
the time we wrote that functionality.

Hope that helps,
Rene

>
> Merci!
> John
>
> -- 
> John Armitage
> --
> http://sites.google.com/site/drjohnarmitage
> http://sites.google.com/site/anrinterrift
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> Dynamique des Fluides Géologiques
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>
>
>
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-- 
Rene Gassmoeller
http://www.math.colostate.edu/~gassmoel/

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