I jsut checked on the Opensuse Build Service.
There are OpenMPI RPMs available for SLES 11 SP2 - but not SLES 11 SP1
http://software.opensuse.org/package/openmpi (then click on Show Other
I have got openmpi installed on my SLES 11 SP1 system, version 1.3.2
Zypper says it is rovided by the System repository - so it should be on the
SLES DVDs you have.
As an aside, installing Openfoam is not trivial - it even packages up its
own version of gcc.