Fluid mechanical design of the cylinder charge motion is an important part of an
engine development. In the present contribution an intake port geometry is
proposed that can be used as a test case for intake port flow simulations. The
objective is to fill the gap between generic test cases, such as the backward
facing step or the sudden expansion, and simulations of proprietary intake
ports, which are barely accessible in the community. For the intake geometry
measurement data was generated on a flow-through test bench and a wall-modeled
LES-simulation using a hybrid RANS/LES approach for near-wall regions was
conducted. The objective is to generate and analyze a reference flow case. Since
mesh convergence studies are too costly for scale resolving approaches only one
simulation was done, but on a very fine and mostly block-structured numerical
mesh to achieve minimal numerical dissipation. Also a steady-state RANS was done
on the same mesh to identify the significance of the scale-resolving approach.
However, to stabilize the RANS on the fine mesh, low-order schemes were
required.
The results show that, both, the RANS and the LES predicted the integral values
of swirl and mass flow measured on the test bench with decent accuracy. Both
methods slightly differ, where the integral swirl coefficient from the WM-LES
shows a better agreement with the experimental value. With respect to the
turbulence it was found, that the instantaneous swirl number undergoes very
significant fluctuations over, both, time and along the cylinder axis, while the
time averaged value is nearly constant along the cylinder axis in, both, RANS
and LES. The difference in swirl number between RANS and LES is existent already
at the cylinder top and at the same time the flow exiting through the intake
ports is also quite similar. The details of the flow around the valves reveal
that the RANS-results overly damps regions of reversed flow, which seems to be
the core reason for the different results.
