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Umberto Zucchelli
The finite-volume CFD code Zephyrus, developed at the Turbomachinery Research Center at the University of Bath, was originally designed to simulate compressible turbomachinery flows with RANS and URANS models. The purpose of this thesis is to investigate the ability of Zephyrus to perform compressible LES simulations without a subgrid model (Implicit LES, or ILES), comparing its accuracy with the open-source OpenFOAM code. Turbulent flow over a bump is a widely used case study, as it reproduces typical characteristics of realistic applications, such as favorable and adverse pressure gradients, non-constant friction along the flow direction, and possibly separations. The results obtained in OpenFOAM have a very good match with DNS data, while Zephyrus shows a tendency to re-laminize. In fact, the turbulent Reynolds decreases from a value Reτ = 200 at the domain entrance to Reτ = 150 downstream of the bump. Contextually, the Cf , turbulent fluctuations and components of the Reynolds stress tensor are attenuated compared to the values obtained with OpenFOAM. This behavior was mainly attributed to the excessive dissipation of the numerical scheme used in Zephyrus.