  Recent numerical work has shown that high-speed confined granular flows down
inclines exhibit a rich variety of flow patterns, including dense
unidirectional flows, flows with longitudinal vortices and supported flows
characterized by a dense core surrounded by a dilute hot granular gas (Brodu et
al, JFM 2015). Here, we revisit the results obtained by Brodu et al. (JFM,
2015) and present new features characterizing these flows. In particular, we
provide vertical and transverse profiles for the packing fraction, velocity and
granular temperature.We also characterize carefully the transition between the
different flow regimes and show that the packing fraction and the vorticity can
be successfully used to describe these transitions. Additionally, we emphasize
that the effective friction at the basal and side walls can be described by a
unique function of a dimensionless number which is the analog of a Froude
number: $Fr=V/\sqrt{gH\cos \theta}$ where $V$ is the particle velocity at the
walls, $\theta$ is the inclination angle and $H$ the particle holdup (defined
as the depth-integrated particle volume fraction). This universal function
bears some similarities with the $\mu(I)$ rheological curve derived for dense
granular flows.
