Sunday, 6 December 2009

Gambit and Fluent on 64 bit Ubuntu


It seems that Gambit doesn't include a 64 bit version. However, 32 bit Gambit can be installed and used on a 64 bit Ubuntu (I tried on a Ubuntu 9.10 amd64). When trying to launch it, there will be an error saying the ARCH is not compatible. The solution is exporting a variable "FLUENT_ARCH" before the go.

:/$ export FLUENT_ARCH="lnx86"

Then Gambit will not complain about the uncompatible architecture.

Different from Gambit, Fluent does include a 64 bit version. But remember the variable FLUENT_ARCH has to be switched back before trying to run a 64 bit Fluent; (similarly, if the Fluent used is also a 32 bit version, the variable value "lnx86" has to be kept).

:/$ export FLUENT_ARCH="lnamd64"

To avoid the inconvenience, launch scripts can be written to simplify the procedure.

Besides, another potential problem which could be encountered when trying to launch Fluent within Ubuntu 9.10 is the lack of is complained. This library was actually provided via package libstdc++5, which is however abandoned after Ubuntu 9.10. However, it can still be found from a Debian source, by which I downloaded the package libstdc++5_3.3.6-18_amd64.deb and fixed the error.


A helpful tutorial on Gambit and Fluent can be found from here, although it is using Windows.

UDF (User Defined Functions) is important for extending the flexibility of Fluent. A programming guide of UDF can be found from this pdf file, and this is the complete UDF manual.


An interesting wave tank example was found from a useful post. It is for a solution of the 2D laminar fluid flow in a tank with oscillating motion of a wall by using multi-phase models. More instructions on this example can be found from the Fluent website, from which related mesh files can also be downloaded.

A detailed set up procedure of the example was described in this pdf file as well.


  1. I can't run gambit on my ubuntu 9.10. Could you explain me better what to write on the shell to "export the variable" and, especially, on which path.

  2. Hi,

    If your Ubuntu is 32 bit, you need to do nothing before launching Gambit. I assume yours is 64 bit. "export the variable" means typing the command below on the console command line:

    export FLUENT_ARCH="lnx86"

    It does not matter in which path you are. I try to explain it. export is the command, FLUENT_ARCH is the variable name, and lnx86 is the variable value we want to set.

    Moreover, we can use command echo to check the effect of the export command previously executed. Type the following command on the console, no matter where you are:

    echo $FLUENT_ARCH

    The value shown should be lnx86.

    Hope it helps and don't hesitate to leave a comment if you need more help.

    Best regards,