  The project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic
studies) conducted at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) provides a
new platform for a variety of liquid sodium experiments devoted to problems of
geo- and astrophysical magnetohydrodynamics. The most ambitious experiment
within this project is a precession driven dynamo experiment that currently is
under construction. It consists of a cylinder filled with liquid sodium that
simultaneously rotates around two axes. The experiment is motivated by the idea
of a precession-driven flow as a complementary energy source for the geodynamo
or the ancient lunar dynamo.
  In the present study we address numerical and experimental examinations in
order to identify parameter regions where the onset of magnetic field
excitation will be most probable. Both approaches show that in the strongly
nonlinear regime the flow is essentially composed of the directly forced
primary Kelvin mode and higher modes in terms of standing inertial waves that
arise from nonlinear self-interactions. A peculiarity is the resonance-like
emergence of an axisymmetric mode that represents a double roll structure in
the meridional plane, which, however, only occurs in a very limited range of
the precession ratio. This axisymmetric mode turns out to be beneficial for
dynamo action, and kinematic simulations of the magnetic field evolution
induced by the time-averaged flow exhibit magnetic field excitation at critical
magnetic Reynolds numbers around ${\rm{Rm}}^{\rm{c}}\approx 430$, which is well
within the range of the planned liquid sodium experiment.
