Towards coupling computational fluid dynamics with system dynamic simulation softwares

Following the increasing performances of the computer technology, Computational Fluid Dynamics (CFD) enables nowadays the accuracy/computing time ratio to be acceptable. Whereas stationary approaches using CFD have been applied successfully in order to determine some parameters of required by macroscopic models, only a few approaches have proposed to link local CFD simulation with macroscopic system simulation. Pneumatic system modelling can become very complex, requiring an extensive experimental approach when some phenomenon has to be accurately studied. The purpose of this work is to show the interest of coupling both CFD and system simulation approaches in order to improve the knowledge on the system. We propose here a novel approach, which consists in a weak coupling of transient CFD simulation with macroscopic system simulation. The technique consists in the use of a deforming mesh taking into account the change of geometry according to time during the transient CFD simulation. The difficulties related to this technique are discussed and illustrated. The simulation procedures consist in determining independently the displacement of the moving part from the macroscopic simulation, before introducing it in the transient CFD simulation. Although this is not a real coupling, it enables to observe interesting results concerning the flow behaviour and to determine the magnitude of some phenomena that can be used to correct the macroscopic model. The term of weak coupling procedure is here used since the two simulations are conducted separately.