Analysis of In-cylinder Flow Field Anisotropy in IC Engine using Large Eddy Simulation

The objective of the analysis presented in this work is to investigate the distribution of the anisotropy invariants of the in-cylinder flow to examine the characteristics of the turbulence during an engine cycle and its interactions with the in-cylinder coherent structures. For this purpose, both the results of Large Eddy Simulations of the flow in an internal combustion engine under motored conditions and measurements obtained in the same configuration have been employed. Investigations include an analysis of the in-cylinder flow properties in the engine’s cross plane by means of first and second order statistical moments. Additionally, the behaviour of the flows anisotropy tensor has been analysed. It has been observed that during the intake stroke the in-cylinder turbulence shows a rather anisotropic structure, whereas during the compression stroke it tends to be more isotropic. Furthermore, the degree of anisotropy increases again in correspondence of vortex breakdown, during which particularly high velocity fluctuations have been identified also by experimental investigation.