Jean Favre (CSCS) presents at SC12 a video created together with Martin Schmitt and Christos E. Frouzakis ETH Zurich of direct numerical simulation of flow in engine-like geometries.
Internal combustion engine flows are turbulent, unsteady and exhibit high cycle-to-cycle variations. There are multiple turbulence generating mechanisms and their effects overlap in time and space, creating strong challenges for the turbulence models currently used, at least for the in-depth understanding of underlying mechanisms as well as for predictive purposes.
Using the highly scalable, parallel, spectral element flow solver nek5000, multiple cycles of the flow around an open valve induced by a moving piston are computed by solving the incompressible Navier-Stokes equations in the temporally-varying geometry. The visualization of the high resolution simulations reveals cycle-to-cycle fluctuations due to differences in the jet breakup and position, which depend on the turbulence remaining in the cylinder at the top dead center (i.e. the piston position closest to the cylinder head). The fine flow structures generated during the expansion stroke, and their suppression during the compression stroke, are shown in the animations of the volume rendering of the velocity magnitude and the isocontours of the vorticity magnitude of the first two cycles.