Pressure at the base in Full Stokes

Extension of Elmer in computational glaciology

Pressure at the base in Full Stokes

Postby Evan » 07 Mar 2016, 06:26

Hi,

I've been looking at the pressure values at the bottom row of nodes when solving full Stokes, and noticed that the values are different (and usually lower) than purely hydrostatic pressure. I figured out that it is because the pressure being output is for the normal-tangential coordinate system, even though I have "Back Rotate N-T Solution = Logical True". Is there a setting to make sure that the pressure is also converted back to the standard Cartesian coordinate system?

Cheers,
Evan
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Re: Pressure at the base in Full Stokes

Postby raback » 07 Mar 2016, 11:33

Hi Evan

Pressure is a scalar field so it needs no back-rotation.

The deviation from the hydrostatic pressure may come from the fact that there is no absolute level for pressure. If you study the pressures at the top and bottom their difference should roughly corresbond to hydrostatic pressure though.

-Peter
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Re: Pressure at the base in Full Stokes

Postby Evan » 08 Mar 2016, 07:54

Hi Peter, thanks for the answer.

I looked into it some more, and it seems that the output I am getting has messed up pressure values in even numbered rows of nodes, while the odd numbered rows have correct values that are close to hydrostatic. This likely indicates there is an integer division error somewhere. This could be within our own code, it will take some time to figure it out.
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