Quality and reliability of the OpenFOAM software for the simulation of
atmospheric boundary layer flow
Abstract
Large-eddy simulations of atmospheric boundary layer flows have
historically relied on the open-channel flow setup, using mixed
pseudospectral and finite differences methods. Single-domain spectral
solvers are naturally suited for the simulation of homogeneous
turbulence in simply-connected domains. Their quality, however, is
expected to degrade significantly in the presence of complex geometries
or non-periodic flow setups. On the contrary, general-purpose finite
volumes solvers are expected to provide a more consistent performance
across a range of flow configurations. In view of future applications
involving flow over complex terrain, the quality and reliability of a
colocated, unstructured, finite-volume solver (OpenFOAM framework) is
here analyzed for the simulation of a pressure-driven atmospheric
boundary layer flow. A sensitivity analysis on grid resolution, aspect
ratio, and CFL condition is performed, and different numerical schemes
are also considered. First and second order statistics, as well as
velocity spectra and two-point velocity correlations, are compared to
predictions from a “battle-tested” pseudo-spectral solver. The
solution is found to be particularly sensitive to the grid aspect ratio
and to the chosen numerical scheme. First and second order statistics
obtained using a non-dissipative setup compare well between the solvers,
with the finite volume one featuring an overdissipative behavior that
leads to enhanced sub-grid scale stress contributions. When considering
velocity spectra, the finite volume solver features a rapid decay of
energy density within the inertial subrange, irrespectively of the
discretization scheme that is adopted. In addition, a spurious pile up
of energy density at high wave numbers is observed across all of the
considered cases. The cause of this behavior will be discussed and
mitigation strategies proposed.