The Message Window in Ansys ICEM CFD is a Tcl/Tk shell with an extended library consisting of Ansys ICEM CFD commands. Most of these commands begin with "ic_" to indicate an Ansys ICEM CFD command. Documentation for Tcl/Tk procedures can be obtained at http://www.tcl.tk.com. Many books have also been written on the subject.

Tcl, which stands for Tool Command Language, is a string-based programming language. This means that, except for inside the expr command, you need not discern between variable types, such as integers, doubles, or strings. Everything is treated as a string. There is also no need to set aside memory (dimension) for variables, and they can be reset to values of any length without re-dimensioning.

Tk stands for Toolkit and contains the add-on Tcl commands that allow graphical interfaces or windows of an application to be made.

Command Syntax

The basic syntax for a Tcl command is:

command arg1 arg2 arg3 ...

Commands are terminated by either a newline character (not usually displayed) or a semicolon, ";".

Spaces are key characters which separate arguments.

Commands can only be continued to the next line with a "\" at the end of the line, or with the beginning of an argument grouping using "{" or ".

Argument Grouping

If a space is to occur inside an argument, then the argument must be grouped as one so that it is not interpreted as separate arguments. For example, the syntax for the puts command is:

puts ?-nonewline? ?channelId? string

The text between question marks, "?...?" includes optional arguments or switches which may or may not be present. Consider the following commands and their return values:

In the first example, note that the grouping brackets, "{...}", were stripped out by the interpreter, but it was treated as a single argument.

In the second example, the arguments, "Hello" and "world" are treated as separate arguments where "Hello" is the channelId. At this point, no channel named "Hello" exists.

There are 3 types of grouping:

Substitution

There are 3 types of substitution:

The following commands can be used to set a value to a variable and then substitute that value for the variable later:

Here, the "\n" is used to ensure that the next text printed to the message window will appear on the next line. Without it, the text will continue on the same line. Also note that the set command will also return the value as well as set the variable to the value.

In the third example, note that no substitution, variable or backslash, was done inside the brackets, "{...}".

Creating a Simple Script

The following examples demonstrate how to load multiple geometry files of varying names and save them all as one new geometry file, without using the Ansys ICEM CFD window (GUI) displayed (GUI stands for Graphical User Interface):

Do the following in the Ansys ICEM CFD window:

You should see the following commands printed:

You may discard all but the first and last commands since you are not interested in any GUI updates, boco settings, or the undo log. This is what remains:

The file name paths start from either the working directory as in this case, or from the top level drive. Since the tetin names can be changed, as well as the working directory, you must use variables. It is safe to specify all names from the top level, so set a variable that is the path of the working directory:

Now, you can use a foreach loop to cycle through multiple tetin files. The simplest syntax for the foreach command is:

foreach varname list body

The foreach loop will step through a list of values assigning each next item in the string to the varname, and evaluating body each time. The list can be a proper Tcl list made using the list command, or by simply grouping text within "..." or {...}. List elements must be separated by spaces. With a foreach loop, the script becomes this:

The example illustrates another important property of grouping arguments with {...} or "..." (but not [...]). The grouping quotes or curly brackets (the "body" argument here) allow an argument to span multiple lines so that the current command is not terminated by the first newline character (which are usually not displayed in the text editor).

Now, you can save this script as script.tcl in the directory D:/user.

Running the Script

There are 4 ways to run the script:

All 4 methods can be used with the GUI displayed, but only the last two can be done in batch mode.

source D:/user/script.tcl can be typed in the message window, or Ansys ICEM CFD can be started in batch mode by adding the -batch argument to the Ansys ICEM CFD startup command (icemcfd -batch). Then you can source the script from the shell.

Using both the -batch and -script arguments (icemcfd -batch -script D:/user/script.tcl) will start Ansys ICEM CFD in batch mode and immediately run the script.

Arrays and Environment Variables

Environment variables are accessed through a reserved global array variable named env.

An array is a variable name followed by another name within parentheses. This is a variable which contains sub-variables, each of which can have a value assigned. The following are array variables of the same array:

You can use the env variable to make the script portable between different installations of Ansys ICEM CFD by using it in the path for any scripting commands that run another executable inside Ansys ICEM CFD.

For example, the following line was printed in the Replay control window when a mesh was written to the CFX5 format:

ic_exec {C:/Program Files/Ansys Inc/v90/icemcfd/5.1-win/icemcfd/output-interfaces/cfx5} -dom D:/user/support/test/tetra_mesh.uns -b D:/user/support/test/family_boco.fbc -ascii -internal_faces D:/user/support/test/cfx5_input

where cfx5 is the executable being run.

The ICEM_ACN environment variable points to the top Ansys ICEM CFD folder, 5.1-win. You can substitute the environment variable for the path leading up to 5.1-win. You can also set a working directory variable as before and substitute that where appropriate using the file join command:

Since argument grouping is always done before substitution, you need not put quotes, "...", around $env(ICEM_ACN). It is seen as one argument in the file join command even though its value contains spaces:

$env(ICEM_ACN) = "C:/Program Files/Ansys Inc/v90/icemcfd/5.1-win"

Note also that the curly brackets ({...}) are removed in the original command in order to do variable substitution within, and the square brackets, [...], will do the grouping.

Creating Your Own Procedures (Functions)

By using the proc command, you can put the earlier script in a procedure and use the file names as the arguments, so different file names can easily be typed in without re-sourcing the file or restarting Ansys ICEM CFD. The syntax for the proc command is:

proc name args body

An example procedure using the earlier script might look like this:

Note the global command inside the procedure. Any variables defined outside of a procedure are global variables. Any variable set or used inside a procedure, including the arguments, are local variables, and will be unset when the procedure is finished executing. wdir is a global variable since it was defined outside a procedure. To access it inside a procedure, it must be declared inside the procedure as global.

After reading the script into Ansys ICEM CFD using any of the 4 methods, the procedure will only be defined. It will not be executed. To execute the procedure, type the following in the Ansys ICEM CFD message window or in the shell (in batch mode):

merge_tetins {tetin1.tin tetin2.tin tetin3.tin} new_tetin.tin

You can re-type this at any time with different argument inputs to re-execute the procedure. If you would like to execute the procedure when the script is read, you can add the call of the procedure to the end of the script. A script can have any number of procedures, and any of the procedures can be called from inside the script.

Mathematical Expressions

Mathematical expressions cannot be evaluated in Tcl simply be typing them. They must be contained within the expr command. For example:

The expr command does its own substitution, so if you use "..." or no grouping at all instead of {...}, it will substitute once before the command is executed, and then once again when it is executed. This may not affect the result, but it will be quicker to execute if you only allow one substitution by using the curly brackets.

The order of evaluation is the same as conventional mathematics. 2/7 is done before 5 is added. The resulting type (floating, integer, etc.) will be integer if all of the operands are integer. If any one operand is a floating point, then the result will be a floating point.