Partially premixed combustion (PPC) can be applied to decrease emissions and increase fuel efficiency in direct injection, compression ignition (DICI) combustion engines. PPC is strongly influenced by how the fuel mixes with oxidizer, which for a given fuel is controlled mainly by (a) the injection, (b) the in-cylinder flow and (c) the geometry and dynamics of the engine. As injection timings can vary over a wide range in PPC combustion deeper knowledge of the in-cylinder flow over the whole compression stroke can improve our understanding of PPC combustion. In computational fluid dynamics (CFD) the in-cylinder flow is sometimes simplified and modeled as a solid body rotation at some time prior to injection in order to produce a realistic flow field at the moment of injection. In real engines the in-cylinder flow motion is governed by the intake manifold, the valve motion and the engine geometry. The deviation of the real in-cylinder flow from a solid body rotation flow field is different at diffuent piston positions. This paper reports an CFD study of the formation and development of a real engine in-cylinder flow field in an optical light duty PPC engine from the opening of the intake valve at -360 CAD ATDC up to 20 CAD ATDC in a motored case (no injection). Particular focus is put on the analysis of the temporal and spatial development of thetumble and swirl flow motion. The resulting flow field of the simulation is compared with PIV measurements in the axial-radial plane of the cylinder close to top dead center (TDC). The adequateness of the solid body rotation assumption as an initial flow is analyzed.