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- ArticleYalnız künye2023Investigation of swirling impinging jet at low nozzle to plate distances
Demir, Fatih; Turgut, Oguz; Calisir, Tamer
Flow field and heat transfer of an impinging swirling jet at low nozzle-to-plate distances have been investigated numerically for three different cases with six different turbulence models. The effects of Reynolds number (2100, 4100, 6100, 8100) and dimensionless nozzle-to-plate distance (H/D = 0.25, 0.5, 0.75, 1) on flow field and heat transfer of the swirling jet are studied parametrically. It is noted that the results of the cases employed exhibit sensitivity to the height of the computational domain defined on the impingement plate, particularly at low nozzle-to-plate distances. It is also seen that one of the cases used is in good agreement with the experimental results by employing Realizable k–ε turbulence model. Parametric analysis results show that the theoretical swirl number decreases with increasing Reynolds number at constant H/D and raises for H/D < 0.75. With the decrease in the Reynolds number from 8100 to 2100, although the H/D loses gradually effect on the heat transfer, H/D = 0.25 continues its effect. It is observed that the pressure peaks and the subatmospheric pressure on the impingement plate change with the nozzle-to-plate distance and Reynolds number.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2023High Incidence of Appendiceal Neoplasms in the Elderly: A Critical Concern for Non-Surgical Treatment
Issin, Gizem; Demir, Fatih; Guvendir Bakkaloglu, Irem; Cagatay, Diren Vuslat; Aktug Simsek, Hasan; Yilmaz, Ismail; Zemheri, Ebru
Objective: Appendiceal neoplasms (ANs) are rare tumors that are often discovered incidentally during histopathological examinations. The increasing incidence of ANs is a critical issue in the non-operative management of acute appendicitis. This study aimed to document the temporal trends over a 12-year period by analyzing the clinical presentation, imaging findings, and histopathological features of ANs. Subjects and Methods: Health records of patients who underwent appendectomy from 2011 to 2022 were examined. Demographic and clinical data, laboratory results, imaging findings, and histopathological features were documented. The characteristics of both ANs and non-neoplastic cases were evaluated. Results: A total of 22,304 cases were identified, of which 330 (1.5%) were diagnosed with ANs. The odds ratio for ANs increased with age, with the highest odds ratio observed in patients aged 70 or older. Receiver Operating Characteristic analysis showed that age and appendiceal diameter were significant predictors of ANs. An optimal age cut-off point of 28.5 years was determined, yielding a sensitivity of 72% and a specificity of 64%. For appendiceal diameter, the optimal cut-off was found to be 9.5 mm, exhibiting a sensitivity of 77% and a specificity of 56%. Conclusion: Although the incidence of ANs remains relatively low, a steady increase has been observed over the past decade. The increasing rate of ANs raises concerns regarding non-surgical management options. The results of this study highlight the importance of considering ANs as a potential diagnosis in older patients and in patients with an appendix diameter greater than 9.5 mm. These findings may have implications for treatment and management.
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