Hi there!
Usually you can find most software in Trisquel repositories and then the
install is trivial via the package manager (or command line.) This doesn't
seem to be the case now.
Looks like OpenFOAM (and paraview) are free software, so let's see how it
could be done.
Following and adapting the instructions from this page
http://www.openfoam.org/download/ubuntu.php
Installing packages from 3rd party repositories can be risky. The first
command adds such a repository.
sudo sh -c "echo deb http://www.openfoam.org/download/ubuntu Oneiric main >
/etc/apt/sources.list.d/openfoam.list"
sudo apt-get update
sudo apt-get install openfoam211 paraviewopenfoam3120
(You might also be interested in Code Saturne or Gerris Flow Solver programs
which are in the repos and can be installed with
sudo apt-get install code-saturne
or
sudo apt-get install gerris)
