First, a short outlook on the research at IFP Énergies nouvelles (IFPEN) in the domain of piston engine CFD will be given. Research activities range from system simulation to LES, with model development activities addressing all related aspects as aerodynamics, two-phase flows, combustion, polluntant formation and exhaust gas after-treatment.

The main part of the presentation will then concern the development of the LES code AVBP and related models for studying non-cyclic phenomena in piston engines. In the last 10 years, LES has become a key topic for exploring these phenomena hitherto not addressed in CFD. This is for one related to the development of massively parallel computers that made such simulations possible, and a direct consequence of the unique potential LES has to address the impact of local instantaneous flow phenomena on the operation of complex devices as piston engine or gas turbines.

After recalling some key requirements on numerics in relation with LES, the application of LES and the AVBP code to study cyclic variability in spark-ignition engines will be presented. Emphasis will be put on how it allows identifying their sources, and how this knowledge is used at IFPEN to formulate system simulation models able to reproduce them. Then, the development of a LES model for Diesel combustion will be presented, and its application to a Diesel jet studied in the frame of the Engine Combustion Network will be discussed.

Perspectives far LES research and for applying LES to industrial subjects will close the presentation.