  The periodic hills simulation case is a well-established benchmark for
computational fluid dynamics solvers due to its complex features derived from
the separation of a turbulent flow from a curved surface. We study the case
with the open-source implicit large-eddy simulation (ILES) software Lethe.
Lethe solves the incompressible Navier-Stokes equations by applying a
stabilised continuous finite element discretisation. The results are validated
by comparison to experimental and computational data available in the
literature for Re = 5600. We study the effect of the time step, averaging time,
and global mesh refinement. The ILES approach shows good accuracy for average
velocities and Reynolds stresses using less degrees of freedom than the
reference numerical solution. The time step has a greater effect on the
accuracy when using coarser meshes, while for fine meshes the results are
rapidly time-step independent when using an implicit time-stepping approach. A
good prediction of the reattachment point is obtained with several meshes and
this value approaches the experimental benchmark value as the mesh is refined.
We also run simulations at Reynolds equal to 10600 and 37000 and observe
promising results for the ILES approach.
