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Chezy’s Resistance Coefficient in a Round-cornered Rectangle Channel

Loukam Imed, Achour Bachir

Archives of Hydro-Engineering and Environmental Mechanics

2024

Vol. 71, nr 1

89--103

The determination of resistance coefficients, such as Chezy’s or Manning’s coefficients, requires a great deal of sensible thought in order to express these coefficients better and more extensively in free-surface channels and aqueducts. This can be achieved if the expression of the resistance coefficient is well stated and takes into account the maximum number of parameters for governing flows in channels. However, in most practical cases, if these coefficients are not expressed by implicit models, they are generally taken as constant and arbitrary. To this end and in a rational manner, the dimensioning and design of channels requires the expression of the resistance coefficient in an easily and explicit form by adopting numerous flow parameters, namely the roughness of the walls, the aspect ratio, the slope of the channels and essentially the viscosity of the liquid. To achieve this aim, the Chezy’s resistance coefficient C is identified using the rough model method (RMM), which gives the discharge under uniform flow conditions appropriate to a round-cornered rectangle channel.

Accuracy of virtual rhinomanometry

Karbowski Krzysztof, Kopiczak Bartosz, Chrzan Robert, Gawlik Jolanta, Szaleniec Jolanta

Polish Journal of Medical Physics and Engineering

2023

Vol. 29, Iss. 1

59--72

Introduction: This paper describes the results of research aimed at developing a method of otolaryngological diagnosis based on computational fluid dynamics, which has been called Virtual Rhinomanometry. Material and methods: Laboratory studies of airflows through a 3D printed model of nasal cavities based on computed tomography image analysis have been performed. The CFD results have been compared with those of an examination of airflow through nasal cavities (rhinomanometry) of a group of 25 patients. Results: The possibilities of simplifying model geometry for CFD calculations have been described, the impact of CT image segmentation on geometric model accuracy and CFD simulation errors have been analysed, and recommendations for future research have been described. Conclusions: The measurement uncertainty of the nasal cavities’ walls has a significant impact on CFD simulations. The CFD simulations better approximate RMM results of patients after anemization, as the influence of the nasal mucosa on airflow is then reduced. A minor change in the geometry of the nasal cavities (within the range of reconstruction errors by CT image segmentation) has a major impact on the results of CFD simulations.