SCALE-RESOLVING SIMULATIONS OF THE FLOW IN INTERNAL COMBUSTION ENGINES
This paper presents calculations of engine flows by using the variable resolution method, known as Partially-Averaged Navier-Stokes (PANS) model. This turbulence bridging method, which supports any filter width or scale resolution, is derived from the Reynolds-Averaged Navier-Stokes (RANS) model equations. It inevitably improves results when compared with its corresponding RANS model if more scales of motions are resolved. This is done by varying the unresolved-to-total ratios of kinetic energy and dissipation. This method, which is presently very much in use for non-moving geometries, especially for external car aerodynamics, is here further extended in order to improve its performance for the engine simulations. An efficient use of the PANS method relies on a definition and calculations of resolution parameters. In the standard approach, the integral scale of turbulence is obtained by using resolved turbulence calculated as difference between instantaneous filtered velocity and the averaged velocity field. Such approach is impractical for cases with moving geometries or with transient boundaries and especially for calculations of engines due to a long cycle-to-cycle averaging in order to supply the optimum resolution parameter. This paper deals with an alternative approach which solves the additional resolved kinetic energy equation (modelled scale-supplying equation) that also takes into account a recently proposed model for the dissipation resolution parameter. Simulations of the real engine case including the spray and combustion calculations will be presented.