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The present work deals with the numerical simulation of nasal cavity aerodynamics in patients affected by nasal pathologies. It represents the beginning of a feasibility study of virtual surgery. In particular, it is a first step towards implementing the virtual surgery concept; here we consider a specific case of a patient with a severe septal deviation. The work results from a collaboration with the ENT ward of San Paolo Hospital in Milan. The nasal cavity of the patient as reconstructed form the CT scan is shown in Fig.1
The first part of the work is focused on turbulence modelling. RANS equations are chosen to describe the flow and the transitional kt-kl-omega model is compared to the more classical one, the k-omega SST model. Then attention is given to virtual surgery to investigate the consequences of the operation. The septal deviation is removed through geometry editing and pre- and post-virtual surgery cases are compared. Geometry is reconstructed from CT images, in case of virtual-surgery it has been modified, and, finally the mesh is created with the purpose of simulating the nasal cavity flow. Fig.2 shows a detail of the flow in the vicinity of the septum, and illustrates the improvement in flow behavior after removal of the septal deviation through virtual surgery. The results suggest the kt-kl-omega turbulence model ability of representing the transitional state of the flow. Unfortunately, no in-vivo information is available to ascertain the validity of the previous suggestion. Further studies are required to validate these results; in other words, in-vitro experimental verification and more accurate simulations such as LES or DNS could offer a quantitative basis for comparison.
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Fig.1: Geometry of the nasal cavity flow |
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Fig.2: Comparison (longitudinal velocity) of pre- and post-surgery in the region of the septal deviation |