TOWARD A GRID-FREE SIMULATION OF FLOW IN ENGINES

摘要

A grid-free numerical method based on the Lagrangian randomvortex element and boundary element methods has been developedfor the simulation of unsteady flow in three-dimensional domainswith moving boundaries of the type observed in IC engines. Forthis purpose, the computational domain is decomposed into a thinregion near the boundary and a remaining domain interior. Theevolution of vorticity in the interior is obtained by the Lagrangianvortex element method. The vorticity in the boundary region i sdiscretized using thin vortex tiles, and its evolution is obtained bya Prandtl-like approximation of the governing equations.Simulations using this approach have thus far been limited to flowin simple geometries, because tile-tile interactions were formulatedfor rectangular tiles only. In this paper, we present an extended tilegeneration and evolution mechanism which allows inter-tileinteraction for any polygon shape for the tiles. This developmentsets the stage for obtaining grid-free simulations of flow incomplex engine geometries. We demonstrate the feasibility of thenew formulation using an example problem of intake flow inside acylinder connected to a harmonically driven piston and an offcentered,tilted port at its ends - with and without a valve.