A penalisation approach to simulate root compressors

The simulation of the unsteady flow field in root compressors requires to deal with several challenges related to the presence of moving parts and complex geometries. In the present work a penalisation approach applied to the compressible Navier-Stokes equations is investigated as a possible technique to perform this kind of simulations. In particular, the compressible Navier-Stokes equations are augmented by source terms which represent the effects of the body on the fluid and then they are integrated in both the fluid and solid domains. The presence of moving bodies is taken into account by a level set function. A validation based on a grid convergence study is performed on the flow around an impulsively started cylinder. A preliminary simulation of the flow field inside a root compressor is performed in order to predict the unsteady mass flow rate through the machine.