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전향각이 큰 선형터빈 익렬을 통하는 난류유동의 수치해석
이훈구,유정열,윤준원,Lee, Hun-Gu,Yu, Jeong-Yeol,Yun, Jun-Won 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.12
A numerical analysis on three dimensional turbulent incompressible flows through linear cascades of turbine rotor blades with high turning angles has been performed by using a generalized k-.epsilon. model which is a high Reynolds number form and derived by RNG(renormalized group) method to account for the variation of the rate of strain. A second order upwind scheme is used to suppress numerical diffusion in approximating the convective terms. Body-fitted coordinates are adopted to represent the complex blade geometry accurately. For the case without tip clearance, velocity vectors and static pressure contours are shown to be in good agreement with previous experimental results. For the case with tip clearance, the effects of the passage vortex and tip clearance flow on the total pressure loss as well as their interactions are discussed.
이훈구,유정열,Lee, Hun-Gu,Yu, Jeong-Yeol 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.6
Three-dimensional turbulent incompressible flow through the tip clearance of a linear turbine rotor cascade with high turning angle has been analyzed numerically. As a preliminary study to predict the tip clearance loss realistically, a generalized k-.epsilon. model derived by RNG (renormalized group) method is used for the modeling of Reynolds stresses to account for the strain rate of turbulent flow. The effects of the tip clearance flow on the passage vortex, the total pressure loss are considered qualitatively. The existences of vena contract and tip clearance vortex have been confirmed and it has been shown that as the size of the tip clearance increases, the accumulated flow through the tip clearance and the total pressure loss downstream of the cascade increase.
성인 천식 환자에서 체질량지수와 기도과민성 및 폐기능의 연관성
최정은 ( Jung Eun Choi ),신태림 ( Tae Rim Shin ),박상면 ( Sang Myeon Park ),김주희 ( Joo Hee Kim ),신성호 ( Sung Ho Shin ),이현영 ( Hyun Young Lee ),장주아 ( Juah Jang ),이훈구 ( Hun Gu Lee ),김철홍 ( Cheol Hong Kim ),현인규 ( In 대한천식알레르기학회 2014 Allergy Asthma & Respiratory Disease Vol.2 No.1
Purpose: Obesity is commonly regarded as a risk factor for asthma development, poor asthma control, and poor response to asthma therapy. However, its relationships are not always consistent. Gender difference has been reported to influence asthma severity and asthma control. We investigated the contribution of obesity to airway hyperresponsiveness (AHR) and lung function before and after treatment in adult asthmatics. Methods: The medical records of a total of 323 adult asthmatics were analyzed retrospectively. Asthma was diagnosed based on the positive result of methacholine bronchial provocation test (PC20≤25 mg/mL) or bronchodilator test (≥12% and 200-mL improvement in forced expiratory volume in 1 second after inhalation of a bronchodilator). Follow-up spirometry was performed in 113 patients after at least 3 months of asthma treatment with controller medication. Percent change between spirometry before and after treatment was defined as {[(value after treatment.value before treatment)/value before treatment]×100}. Body mass index (BMI, weight [kg]/height [m2]) was categorized into underweight (<18.5), normal weight (18.5.24.9), overweight (25.0.29.9), and obese (>30) according to the world health organization classification. Results: BMI did not show any significant correlation with PC20 value of methacholine provocation test and each lung function parameter before and after treatment. When we divided the study subjects according to gender and age, BMI was negatively correlated with PC20 value only in female adult asthmatics under 65 years old (r=.0.024, P=0.036). Conclusion: Obesity is positively correlated with the intensity of AHR in female adult asthmatics. Gender seems to differentially contribute to the relationship between BMI and AHR. (Allergy Asthma Respir Dis 2014;2:16-22)