Flow and Sound Calculation in a Human Nose

Experimental investigations of the air flow through human noses during inhalation and exhalation, as well as effects of sound transport, acoustic resonance and filtering, are hard to realize. High accuracy flow measurements, as applied in technical contexts, are not feasible on live patients. Measurements on deceased, though technically realizable, do not resemble reality due to post-mortem changes in geometry and the surface characteristics of the tissue. Though scanning techniques like computer tomography (CT) can resolve those airways up to a certain accuracy, depending on the CT resolution, the complexity of the nose geometry and the very thin airways complicate experimental model building. DPIV Measurements of experimental models have been carried out with enlarged models and liquids as flow medium (e.g. [5]). Acoustical measurements in this context are even more complex. Modern nasal surgery, however, throws up open questions on how to treat and remodel nasal airways. In fact, presently there is not enough measurement to define standards for shapes of the inner nasal airways, that provide a patient with comfortable breathing, smelling and hearing. Here, the use of numerical approaches might help. It might support measurements, that are presently in use, but might also go beyond: Out of the present clinical scanning techniques, e.g. CT, a patient's nasal geometry can be reconstructed and flow calculations through this geometry can be realized. Investigations of varying geometries seem to be realizable easily. Even a virtual surgery room with the aid of fluid dynamics methods for a proper in-situ judgment of flow characteristics of the nose seems possible (e.g. [3,1]). Within this contribution, exemplary flow calculations will be shown, using a parallelized, compressible Navier-Stokes code. Possibilities and limitations of the performed calculations will be outlined and discussed. Special focus will be laid on the grid generation method and the problems arising for data validation and comparability. Possibilities and limitations of acoustical calculations will be sketched and medical requirements with respect to a future virtual surgery room will be set in relation to presently available methods. This research project is realized on initiation and in cooperation with the University of Halle (HNO-Klinik des Universitätsklinikums Halle, Germany). We thank the Doctores E.-J. Haberland, Knipping, Knörgen and Stock for their kind cooperation and their support.