[aspect-devel] boundary velocity function expressions

Payman Janbakhsh payman.janbakhsh at mail.utoronto.ca
Mon Oct 10 19:22:09 PDT 2016

Thank you John,
Actually the continental extension prm file that you sent to Mohamed helped me to figure out the velocity prescription to different boundaries using functions.

However, how can I prescribe velocity to a segment of a boundary and let the rest of that boundary be tangential?
For instance, considering a right boundary, a mantle lithospheric slab having its own westward prescribed velocity, but the rest of that boundary (mantle) be tangential.

Thanks again


From: Aspect-devel [mailto:aspect-devel-bounces at geodynamics.org] On Behalf Of John Naliboff
Sent: October 10, 2016 12:25 PM
To: aspect-devel at geodynamics.org
Subject: Re: [aspect-devel] boundary velocity function expressions

Hi Payman,

Specifying the velocity on the boundaries works a bit differently than what you have outlined below.

In 2D you need to specify velocity components for x and y, which you do via the function.  You can control how the velocity on different boundaries (ex: left & right) by including conditional statements in your functions based on the position (defined by 'x' and 'y' in 2D).

You can also specify that only certain components of the function apply to a certain boundary (i.e. only x velocity from functions is applied to left/right boundary).

If there is a specific setup you are thinking of, can you sent over a basic parameter file that we can look over?



John Naliboff

Assistant Project Scientist, CIG

Earth & Planetary Sciences Dept., UC Davis
On 10/09/2016 03:08 PM, Payman Janbakhsh wrote:
I’m trying to implement the following for a 2D problem:

Set Prescribed velocity boundary indicators = left : function  ,  right : function

But get error when trying to give  Function expressions in:     set Function expression =
I have tried separating 2 velocity components with semicolon and separate function expressions with comma .
                                                            Left boundary function                  right boundary function
Set Function expression =             if(z>=1000 , 1, 0) ; 0           ,           if(z>=1000, -1,0) ; 0

I’ve tried many ways including below but all give errors or nonsensical velocity Glyphs:
Set Function expression =          left:   if(z>=1000 , 1, 0) ; 0           ,     right:      if(z>=1000, -1,0) ; 0
Set Function expression =           left =   if(z>=1000 , 1, 0) ; 0           ,    right=       if(z>=1000, -1,0) ; 0
Set Function expression =           (  if(z>=1000 , 1, 0) ; 0     )      ,       (    if(z>=1000, -1,0) ; 0 )

How can I separate multiple function expressions each for its corresponding boundary indicator ?




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