Time Dependent Fluid Dynamic Simulations for More Accurate Time Averaged Results

Computational Fluid Dynamics (CFD) has advanced to the point of addressing three dimensional unsteady flows with time dependent boundary conditions and moving parts. Often, such time dependent behavior is important for evaluation of time-averaged performance of fluidic systems. Illustrative examples in the automotive industry include intake and exhaust systems under operating conditions, turbine pumps in which impeller blades interact with the inlet and/or outlet (water pump, fuel pump, turbocharger, etc.), cylinder valves and pistons under motoring conditions, and torque converters in which blades interact when passing closely to each other. This paper discusses software requirements for simulating these systems. Examples are presented showing how time-averaged results of time dependent simulations deviate significantly from those of steady state simulations. In some cases, the differences suggest different design principles to the engineer.