Uncinectomy and middle meatal antrostomy (MMA) in the maxillary sinus surgery mainly affects the airflow pattern in this sinus. The aim of the present work was to analyze the effect of this surgery on the heating and humidifying function of the nose. A series of CT scan images of a healthy male volunteer was used and a computational model for the human nasal airway including nasal cavity and maxillary sinuses was developed. Then, uncinectomy and MMA was performed virtually on the CT images on a single nasal passage and associated maxillary sinus. The continuity, momentum, energy and moisture transport equations were solved numerically. In particular, a thermal model for evaluating the temperature and moisture distribution on the mucus surface covering the walls of the nasal airway was developed. A steady breathing flow rate related to the rest conditions was investigated, where different relative humidity levels for the ambient air were considered. The airflow pattern, temperature and moisture concentration contours for pre- and post-surgery cases were evaluated and their differences were discussed.
In this study, the atomization of an effervescent atomizer with an elliptical and circular orifice was investigated experimentally in the gaseous crossflow. The shadowgraph technique was used to visualize the near field of the spray atomization. To measure the spray penetration height in crossflow, image processing was performed on the shadowgraph images based on two different approaches: (i) a threshold analysis of average spray images and (ii) standard deviation images of spray. By comparing these two approaches, it is found that the penetration heights obtained from the standard deviation images were much higher since these images were able to capture small droplets more accurately. Moreover, based on the standard deviation images of spray, an empirical correlation for the spray penetration height was developed as a function of gas-liquid mass flowrate ratio, liquid-air momentum flux ratio, orifice aspect ratio, and downstream location. The laser diffraction technique was used to analyze the particle size of the aerated elliptical and aerated circular jets in a gaseous crossflow. For each orifice shape, the effect of gas-liquid ratio and downstream location on the Sauter mean diameter (SMD) was studied. The results show that the aerated circular jet penetrates higher into the gaseous crossflow than the aerated elliptical jet. Besides, the aerated circular jet in crossflow mainly generates smaller drop sizes compared to the aerated elliptical jet.
The breakup of a liquid jet by a high-velocity gaseous crossflow has many applications in industry. Penetration height of the liquid jets in crossflows is considered as the main parameter of interest, and several empirical correlations for it have been developed by many researchers. However, recent studies show that significant differences between the predictions of the available correlations exist since the liquid jet in crossflow is a complex process and the penetration height depends on many parameters and variables. In the present study, it is shown that, although developing an accurate explicit equation or model is difficult, an Artificial Neural Network (ANN) is able to estimate the penetration height precisely. To train and test the network, input and output data have been obtained from experiments conducted in a wind tunnel. Overall, 48 different experiments have been performed, and 45 cases have been selected and partitioned into two parts: 80% for training and 20% for testing. Afterward, the remaining three cases have been used independently to test the network performance rigorously. In summary, it is revealed that ANNs enable the accurate prediction of penetration heights and have great potential to be used for more complicated operating conditions.
The spray structure of an effervescent atomizer with an elliptical orifice is studied using the high-speed shadowgraphy technique. The major to minor axis ratio of the ellipse is 3. The effect of gas to liquid ratios (GLR) in the range of 0.55-2.55 % on the spray angle is analyzed. The water flow rate was constant for all the tests, while the airflow rate varied. Two imaging views of minor and major axes were captured for each test condition. This study shows that an increase in the gas flowrate results in an increase in the spray angle from both imaging views. It was shown that the spray angle from the minor view is wider than that of the major view, and the difference magnifies by increasing the GLR.
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