The article describes a model of energy transfer in human upper respiratory tract, for which we estimate the hydrodynamic drag coefficient. The internal cavity of the nose represents a system of series- and parallel- connected channels. While modeling, we assumed the following points: (1) separation of central flow of inhaled air (hereinafter referred to as a stream filament) into four streams within nasal vestibule; (2) central distribution of stream filaments into communis, superior, medius, and inferior nasal meatus; (3) merging of the stream filaments into one in the choanae; (4) repetition of the pattern of redistribution of stream filaments under the reverse movement of air from choanae to the nasal vestibule. During the modeling of air flows inside the full-scale model of the nose the air flow velocity rate, which is necessary to calculate hydrodynamic drag coefficient, was determined for different parts of the nasal cavities, namely - nasal vestibule, choanae, superior, medius, inferior and communis nasal meatus. Full-scale model of the nose sinus was made of epoxy. For measuring velocity of air flow miniature bead heat-loss anemometers were placed inside the model: in the nasal vestibule, communis, superior, medius and inferior nasal meatus and choanae. The model’s energy transfer is based on the law of conservation for steady incompressible fluid flows (Bernoulli's equation) and Kirchhoff's rules. Solution of the Bernoulli's equation is founded on the following assumptions: (1) mass refers to the volume of a separate stream filament, and, since the density of the air as it moves inside the volume does not change, it can be considered identical in sections 1-1 (nasal vestibule) and 2-2 (choanae); (2) the share of the potential energy was not considered inside the nasal meatus due to the small size of the model; (3) the quantity of heat supplied to a unit mass in each section depends on the temperature of the heated walls, which is constant in the entire nasal cavity, therefore it is assumed that E heat 1= E heat 2 and is not considered in further calculations; (4) air flow velocity is maximum in the center of the flow, hence, due to the location of anemometer in this area, the maximum surface velocity and time velocity would coincide, causing the average surface integral of velocity change within the section can be replaced by time averaging; (5) because the density of the medium is constant, kinetic energy can be taken outside the integral sign; (6) air temperature inside the model can be considered approximately the same and equal to the temperature of the medium, then the values of the internal energy in sections 1-1 and 2-2 can be regarded as the same and not considered in the calculation of the hydrodynamic resistance coefficient; (7) the static pressure in the cross section depends on the air flow velocity, therefore, it as the velocity can be taken as an average value. The simulation results showed that: (1) during an intake of breath, hydrodynamic resistance coefficient was the lowest for the superior and inferior nasal meatus and was maximal in the communis and medius nasal meatus; (2) during exhalation the value of hydrodynamic resistance coefficient decreases because of the air movement in the communis and medius nasal meatus.
aerodinamika dyhatel'nogo cikla, koefficient nosovogo soprotivleniya, koefficient gidrodinamicheskogo soprotivleniya
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