Contrib/funkySetFields
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1 Short description
This utility sets the value of a scalar or a vector field depending on an expression that can be entered via the command line or a dictionary. It can also be used to set the value of fields on selected patches. It's like the setFields-utility on steroids.
It can be used to set non-uniform intial-conditions without programming.
This utility is provided as-is and is a permanent Beta-Version (but it works fine for me, if it doesn't for you: tell me about it and I'll see what the problem is)
1.1 Words of warning
This utility can save you the work to program your own utility to set initial-conditions, but
- you should be familiar with the C expression syntax
- it makes it easier to 'shoot yourself in the foot' (do stupid things)
- especially for large cases a custom-made utility might be more efficient
(it's like a Swiss Army Knife: useful for a lot of things, but not necessarily the best tool for these tasks)
2 Pre-requisites
To compile this utility at least version 2.1 of Bison has to be installed. Check with
bison -V
on the command line before trying to compile it.
2.1 For those who don't have bison 2.1
It has been brought to my attention that there are a lot of people that still have to live with 1.x bisons. For those there is a script provided that inserts the generated sources. Just go to the source directory and call
./insertGenerated.sh
It copies the generated files to the directory and modifies Make/files
3 Usage
The utility can be used from the command line or with a dictionary. In both forms an option -time is needed to select the time step.
3.1 Basic ommand line usage
This mode is selected if the -field option is used to select a target field. If the target doesn't yet exist the option -create has to be added.
In addition an option -expression is needed with the expression that is to be written to the target field (Syntax see below).
An optional option is -condition: only cells for which this expression evaluates to true are overwritten with the expression. For all other cells the old value is kept.
expression and condition should be enclosed in quotes to keep the shell from interpreting special characters.
An example of the usage would be:
funkySetFields . cavity -field U -expression '(grad(dist())^vector(0,0,-1))*mag(pos()-vector(0.05,0.05,0))/0.05' -time 0
This sets the velocity field to a 'circle' around the center. In the most simple case the velocity field can be set to zero
funkySetFields . cavity -field U -expression 'vector(0,0,0)' -time 0
Same for the pressure field:
funkySetFields . cavity -field p -expression '0' -time 0
The damBreak-tutorial could be initialized with
funkySetFields . damBreak -time 0 -field gamma -expression " pos().x <= 0.1461
