초음속 흡입구 주위에서의 저주파수 Buzz 유동의 수치모사

곽인근,이승수 한국항공우주학회 2010 한국항공우주학회 학술발표회 논문집 Vol.2010 No.4

소아 천식 유지요법 실태와 천식이 환자와가정생활에 미치는 영향에 대한 조사

곽인근,임기현,김영호,공도연,편복양,이혜란 대한 소아알레르기 호흡기학회 2005 Allergy Asthma & Respiratory Disease Vol.15 No.4

Purpose:In spite of the development of asthma management guidelines, there are discrepancies between the guidelines and real management. We surveyed the insights and the real management of asthma to assess the current status of its management in Korea. Methods:The objects of the survey were 266 parents with asthmatic children, who attended an educational lecture by the Korean World Asthma Day Project Office(KWADPO). Face to face interviews with questionnaires of 11 questions about understanding of asthma maintenance therapy, actual conditions of taking medicine and the impact of asthma on the family life were undertaken. Results:The Median age of the patients was 5.2 years old and their parents' age ranged from those in their twenties to those in their forties. The number of the patients actually taking asthma maintenance medicine(40.6 percent) was a little bit lower than the level of awareness(53.0 percent). As a controller, patients are using short-acting beta2 inhalers(35.3 percent), steroid inhalers(including combination inhaler)(31.6 percent), leukotriene receptor antagonists(24.8 percent), antihistamines(25.6 percent), theophylline(2.3 percent), etc. Regular visits to hospital or clinic were done in 53.0 percent of the patients. As a controllers, oral medications(69.2 percent) was preferred to inhalers(18.0 percent) due to better compliance and easier dosage adjustment. Conclusion:According to the survey, asthma had negative effects on the life quality of patients and their families. Remarkable discrepancies were noticed between the guidelines and the real-world status of taking medicine in asthmatic children. It is necessary to have patients participate actively in making asthma management plans to raise their efficacy. 목 적 : 천식은 삶의 질에 영향을 미치는 중요한 만성 질환으로서 이를 극복하기 위하여 지난 수 십 년간 새로운 약제와 치료 지침이 개발되어져 왔다. 그러나 이런 노력과 실제 약제사용 실태 사이에는 큰 차이가 있다. 따라서 본 조사에서는 천식 유지요법의 실태를 파악하고, 아울러 환자와 가족의 삶의 질을 측정함으로써 총체적 천식 환자 관리에 기여하고자 본 조사를 시행하였다. 방 법 : 천식 및 알레르기 예방본부에서 시행한 교육 강좌에 참여한 천식 아동의 보호자 266명을 대상으로 일대일 방식으로 설문지 조사를 시행하였다. 설문지는 총 11개 문항으로 천식조절제에 대한 보호자의 인식, 약제 사용 실태, 정기적인 병원 방문 실태, 약제 선호도와 그 이유, 천식 아동과 부모의 사회생활과 감정상태, 염려사항 등으로 구성되어 있다. 결 과 : 조사대상 환아의 중앙나이는 5.2세, 보호자의 연령분포는 20-40대까지 다양하였다. 이환기간은 1년 미만이 25.2%, 1-3년이 43.2%, 3년 이상이 31.6%이었다. 천식조절제에 대한 인식을 가지고 있는 부모는 53.0%이었으나, 실제 유지요법을 시행하고 있는 경우는 40.6%이었다. 조절제로서 속효성 기관지확장제를 사용하는 경우가 35.3%, 흡입제 스테로이드(복합제 포함) 31.6%, 항류코트리엔제 24.8%, 항히스타민제 25.6%, 테오필린계 2.3%이었다. 현재 사용하고 있는 약제에 대해 모르는 경우가 흡입제 16.2%, 경구 약제 27.4%이었다. 정기적으로 병원을 방문하는 경우는 53%이었다. 천식조절제로의 선호도는 흡입제 18.0%, 경구 약제 69.2%이었다. 흡입제를 선호하는 이유는 익숙해져서 37.5%, 효과적이므로 25.0%이었고, 경구 약제를 선호하는 이유는 높은 순응도(50.6%), 쉬운 용량 조절(34.6 %) 등이었다. 천식은 환자의 감정에 부정적인 영향을 미치고 환자와 가족의 사회생활에 지장을 초래하고 있었다. 환자들이 가장 염려하는 것은 친구들과의 놀이에 참여할 수 없는 것이었고, 보호자들의 가장 큰 걱정은 집 밖에서 천식발작이 일어날 수 있는 것에 대한 염려, 장기치료 부작용 등이었다. 결 론:천식 약제 사용실태 조사결과, 유지요법에 대한 인식, 정기적인 의료기관 방문, 유지요법의 사용실태는 모두 미흡한 수준으로 나타났다. 천식은 환자들에게 천식에 대해 부정적인 감정을 일으키고 가족 구성원 전체의 사회생활에도 영향을 미치고 있었다. 결론적으로 천식치료에서는 환자가 치료의 능동적 주체가 되어야 하고, 지속적 유지요법이 강조되어야 하며 이를 위해서는 환자 천식교육과 사회 전체의 참여가 필요하다.

Performance Evaluation of Two-Equation Turbulence Models for 3D Wing-Body Configuration

곽인근,이남훈,이승수,박상일 한국항공우주학회 2012 International Journal of Aeronautical and Space Sc Vol.13 No.3

Numerical simulations of 3D aircraft configurations are performed in order to understand the effects of turbulence models on the prediction of aircraft's aerodynamic characteristics. An in-house CFD code that solves 3D RANS equations and two-equation turbulence model equations are used. The code applies Roe’s approximated Riemann solver and an AF-ADI scheme. Van Leer’s MUSCL extrapolation with van Albada’s limiter is also adopted. Various versions of Menter’s k-ω SST turbulence models as well as Coakley’s q-ω model are incorporated into the CFD code. Menter’s k-ω SST models include the standard model, the 2003model, the model incorporating the vorticity source term, and the model containing controlled decay. Turbulent flows over a wing are simulated in order to validate the turbulence models contained in the CFD code. The results from these simulations are then compared with computational results from the 3rd AIAA CFD Drag Prediction Workshop. Numerical simulations of the DLR-F6 wing-body and wing-body-nacelle-pylon configurations are conducted and compared with computational results of the 2nd AIAA CFD Drag Prediction Workshop. Aerodynamic characteristics as well as flow features are scrutinized with respect to the turbulence models. The results obtained from each simulation incorporating Menter’s k-ω SST turbulence model variations are compared with one another.

외부장착물 분리해석을 위한 Off-line 6-DOF 시뮬레이션 프로그램 개발

곽인근,신재화,이승수,최기영,현재수,김남균 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-

축대칭 초음속 흡입구 주위의 저주파수 및 고주파수 버즈(Buzz)에 대한 수치모사

곽인근(E. Kwak),이남훈(N. Lee),공효준(H. Gong),이승수(S. Lee) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.2

In this paper, numerical simulations of both low- and high-frequency buzz phenomena at the throttle ratios (T.R.) in Nagashimas experiment are performed. The dominant frequencies of the low-and high-frequency buzz in the experiment are about 109 Hz with T.R.=0.97 and 376 Hz with T.R.=0.55, respectively. An axisymmetric solver with the S-A turbulence model is used for the simulations, and DFT(Discrete Fourier Transform) on pressure histories is conducted for the buzz frequency analysis. In the present simulations, the free-stream Mach number and the Reynolds number based on the inlet diameter are 2 and 107, respectively. Both the low- and high-frequency buzz phenomena are accomplished without the changes in the grid topology. The dominant frequency of the simulation is about 125 Hz with T.R.=0.97, while it is 399 Hz with T.R.=0.55.

보정한 Bleed 모델을 이용한 초음속 흡입구 버즈 제어

곽인근(E. Kwak),이승수(S. Lee) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.4

Database of a bleed model has been corrected and numerical simulations have been performed to control buzz using the corrected bleed model. The existing bleed model, which was developed as a part of a boundary condition model for porous bleed walls, underestimates bleed flow rate because flow accelerations near the bleed regions are ignored. Also, it overpredicts the sonic flow coefficient when the bleed plenum pressure ratio is high. To correct these problems, and to enhance the performance of the bleed model, the database has been corrected using CFD simulations to compensate for the flow acceleration near the bleed region. Futhermore, the database of the bleed model is extended with the second order extrapolation. The corrected bleed model is validated with numerical simulations of a shock-boundary layer interaction problem over a solid wall with a bleed region. Using the corrected bleed model, numerical simulations of supersonic inlet buzz are performed to find the deterrent effects of bleed on buzz. The results reveal that bleed is effective to prevent buzz and to enhance the inlet performance.

다공성 벽면(porous-wall)과 거칠기가 있는 벽면(rough-wall)에 관한 경계조건을 이용한 초음속 흐름의 수치모사

곽인근(E.K. Kwak),유일용(I.Y. Yoo),이동훈(D.H. Lee),이승수(S. Lee) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.4

The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Furthermore, numerical simulations for supersonic shock boundary layer interaction with a bleed region were performed and their results were compared with the existing computational results.

CFD를 이용한 bleed 모델의 데이터베이스 보정

곽인근(E. Kwak),공효준(H. Kong),이승수(S. Lee) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.11

Database of a bleed model, which was developed as a part of a boundary condition model for porous bleed wall, has been corrected using CFD simulations to enhance the performance of the bleed model. The existing bleed model underestimates bleed flow rate because flow acceleration near bleed regions is ignored. Also, it overpredicts sonic flow coefficient when the bleed plenum pressure ratio is high. To correct these problems, and to enhance the performance of the bleed model, the database has been corrected using CFD simulations to compensate the flow acceleration near the bleed region. Furthermore, the database of the bleed model is extended with second order extrapolation. Numerical simulations of a shock-boundary layer interaction problem over a solid wall with a bleed region reveal that the modified database gives more accurate results than the existing database.

축대칭 초음속 흡입구 주위의 저주파수 및 고주파수 버즈(Buzz) 에 대한 수치모사

곽인근(E. Kwak),이승수(S. Lee) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.11

In this paper, numerical simulations of both low- and high-frequency buzz phenomena at the throttle ratio (T.R.) found in Nagashimas experiment are performed. The dominant frequencies of low- and high- frequency buzz in the experiment are about 109 Hz with T.R.=0.97 and 376 Hz with T.R,=0.55, respectively. An axisymmetric solver with the S-A turbulence model and the SST turbulence model is used in the simulations and DFT on pressure histories is conducted for the buzz frequency analysis. In the present simulations, the free-stream Mach number and the Reynolds number bases on the inlet diameter are 2 and 10<SUP>7</SUP>, respectively. Both low- and high-frequency buzz phenomena are simulated successfully without changes in the grid topology. The dominant frequency of the simulation is about 125 Hz with T.R.=0.97, while it is 399 Hz with T.R.=0.55.

보존형 형태의 S-A 난류 모델 방정식을 이용한 이차원 유동 해석

곽인근(E. Kwak),백지영(J.Y. Baek),이승수(S. Lee) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5

Numerical simulations of two dimensional flows are performed with a conservative form of S-A turbulence model and the simulation results are compared to those of the standard form and the compressible form. The conservative form is derived, from the standard form, which is in non-conservative form, using the continuity equation. The model constant of the conservative form is corrected to compensate for the differences between the conservative and the non-conservative discretizations. For verification of the conservative form of the equation, flows over a flat plate at various flow conditions are computed and the results are compared to those of the other forms as well as other computational results and theories. For subsonic flows, little difference is observed between the results of three forms. For supersonic and hypersonic flows, however, skin frictions of the compressible form and the conservative form are slightly larger than that of the standard form. Furthermore, numerical simulations of a transonic flow around an airfoil are performed with three forms and usefulness of the conservative form is confirmed by obtaining reasonable results.