수정 Sonic Arc 익형의 저속 공력특성

이장창 한국항공우주학회 2010 한국항공우주학회 학술발표회 논문집 Vol.2010 No.11

익형 주위의 압축성 습공기 유동에 대한 수칙해석

이장창 국립7개대학공동논문집간행위원회 2002 공업기술연구 Vol.2 No.-

Latent heat is generated when the phase of water vapor in humid air is changed. This changes the properties of compressible flows around airfoils and is investigated by numerical simulations. The computations are based on a recent small-disturbance approach by Rusak and Lee [1]. This approach describes the heat release by the nonequilibrium and homogeneous condensation process using the classical nucleation and droplet growth models. The nonlinear interaction between the heat transfer by the condensation, the kinetic energy of the compressible flow, and the thermal properties of the flow is explored and the similarity parameters which govern the problem are presented. The results of the calculations show good agreement with available simulations using the Euler equations. The similarity rules are used to suggest various flow cases which have a sufficiently close behavior of both the flow dynamics and the condensation properties. It is shown that compressible flows of humid air may be applied to augment the aerodynamic performance of airfoils used in fluid machinery.

Low Speed Thrust Characteristics of a Modified Sonic Arc Airfoil Rotor through Spin Test Measurement

이장창 한국항공우주학회 2012 International Journal of Aeronautical and Space Sc Vol.13 No.3

The low speed aerodynamic characteristics for a modified sonic arc airfoil which is designed by using the nose shape function of sonic arc, the shape function of NACA four-digit wing sections, and Maple are experimentally investigated. The small rotor blades of a modified sonic arc and NACA0012 airfoil are precisely fabricated with a commercially available light aluminum(Al 6061-T6) and are spin tested over a low speed range (3000rpm-5000rpm). In a consuming power comparison, the consuming powers of NACA0012 are higher than that of modified sonic arcs at each pitch angle. The measured rotor thrust for each pitch angle is used to estimate the rotor thrust coefficient according to momentum theory in the hover state. The value of thrust coefficients for both two airfoils at each pitch angle show almost constant values over the low Mach number range. However,the rotor thrust coefficient of NACA0012 is higher than that of the modified sonic arc at each pitch angle. In conclusion, the aerodynamic performance of NACA0012 is better than that of modified sonic arcs in the low speed regime. This test model will provide a convenient platform for improving the aerodynamic performance of small scale airfoils and for performing design optimization studies.

고차항 특이치 분포방법을 이용한 포텐셜 유동의 해석

이장창,유홍선 한국항공우주학회 1990 한국항공우주학회 학술발표회 논문집 Vol.- No.-

Accurate calculation of the pressure and temperature of water, steam, and ice: Formulation for CFD

이장창,Meng-Sing Liou 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.11

An accurate approach is proposed for calculating the thermodynamic properties of water in three states: liquid, steam and ice, and the transitional states among them. The formulation is expressed in terms of quantities that are naturally used in Computational Fluid Dynamics (CFD), namely the specific volume ( v ) and specific internal energy ( u ), through the use of Gibbs free energy. The Gibbs free energy formula proposed by IAPWS, formulated as a function of pressure and temperature, is used as a basis in our calculations. The Jacobian matrix resulting from the transformation between sets of variables ( p,T ) and (v,u ) are derived for each phase; the Newton-Raphson method is used to iteratively solve the nonlinear equations. Numerical calculations have been carried out for the entire phase diagram covering all three phases. The numerical results are compared with the original data of IAPWS and the associated errors are analyzed. It is confirmed that the pressure and temperature are accurately calculated, with largest relative error on the order of 10−7 in the ice phase. Hence, other thermodynamic properties are also obtained within the same level of accuracy. The method proposed in this paper for calculating pressure and temperature, variables needed in CFD, is reliable and can be applied to the numerical simulation of multiphase flows, including phase changes.

수정 Sonic Arc 익형의 공력성능

이장창(Jang-Chang Lee) 한국항공우주학회 2007 한국항공우주학회지 Vol.35 No.7

TSD 이론으로 구해진 sonic arc 익형의 형상을 새로운 익형 형상으로 수정하고 천음속 유동에서의 공력 성능을 조사하였다. Euler solver를 이용하여 수정 sonic arc 익형에 대한 수치계산을 수행하고 그 결과를 NACA0012 익형의 공력 성능과 초임계 익형의 공력 성능 그리고 NACA64A210 익형의 공력성능과 비교하였다. 천음속 유동의 같은 자유 유통 마하수에서 수정 some arc 익형의 압력 항력은 NACA0012 익형의 압력 항력보다 더 작게 나타났으며 수정 some arc 익형의 양항비는 NACA0012 익형의 양항비보다 훨씬 크게 나타났다. 천음속 유동에서의 항력 발산 마하수 비교에서는 수정 some arc 익형의 항력 발산 마하수가 NACA64A210 익형의 항력 발산 마하수보다는 크게 나타났지만 초임계 익형의 항력 발산 마하수 보다는 작게 나타났다. Sonic arc airfoil derived from the TSD theory is modified to new airfoil shape and its aerodynamic performance in transonic flow is investigated. The numerical simulation using Euler equations for the modified sonic arc airfoil is performed. The numerical results are compared with the aerodynamic performance of NACA0012 airfoil, of supercritical airfoil, and of NACA64A210 airfoil. In the same free stream Mach number of transonic flow, the pressure drag of the modified sonic arc airfoil is smaller than that of NACA0012 airfoil and the lift-drag ratio of the modified sonic arc airfoil is much larger than that of NACA0012 airfoil. In the comparison of the drag-divergence Mach number of transonic flow, the drag-divergence Mach number of the modified sonic arc airfoil is larger than that of NACA64A210 airfoil but is smaller than that of supercritical airfoil.

채널형상과 마하수가 천음속 연소에 미치는 영향에 대한 수치해석적 연구

이장창(Jang-Chang Lee) 한국항공우주학회 2005 한국항공우주학회지 Vol.33 No.11

??천음속 미교란 모델과 1단계 1차 Arrhenius 화학반응식을 이용하여 반응유체의 압축성 유동에 대하여 연구하였다. 유체 유동은 적은 열방출을 수반하는 희박 예혼합 반응에 국한시켰다. 천음속 연소에 끼치는 채널형상과 채널입구 마하수의 영향 등을 수치해석을 이용하여 조사하였다. 수치결과에서 채널확대는 주어진 채널길이 내에서 화학반응을 증가시키고 있음에 반하여 채널수축은 출구 근처에서 화학반응을 억제시키고 있음을 보여주고 있다. 확대형 채널 내에서 입구유동 마하수 증가는 고정된 반응속도에서 유동을 가속시켰으며 불활성 유체 경우에는 나타나지 않는 약한 충격파가 나타났다. 또한 확대형 채널 출구 근처의 압력과 온도를 증가시키고 주어진 채널길이 내에서 반응체의 소비를 도와준다. The compressible flow of reactive fluid is investigated by using the transonic small-disturbance (TSD) model and the one-step first-order Arrhenuis chemical reaction. The fluid flow is restricted to dilute premixed reactions with small heat release. The effects of channel shape and Mach number on transonic combustion are studied by numerical analysis. The results show that the channel divergence increases the chemical reaction within the given channel length whereas the channel convergence inhibits the chemical reaction near the outlet and that increasing the inlet flow Mach number at a fixed reaction rate causes the flow acceleration in a diverging channel and the appearance of weak shock waves which do not show in the inert flow case. It also helps to increase the pressure and temperature near the diverging channel outlet and to consume the reactant within the given channel length.

물, 증기, 얼음의 압력과 온도에 대한 정밀계산 : CFD를 위한 공식

이장창(Jang-Chang Lee),Meng-Sing Liou 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

An accurate approach is proposed for calculating the thermodynamic properties of water in three states: liquid, steam and ice, and the transitional states among them. The formulation is expressed in terms of quantities that are naturally used in Computational Fluid Dynamics (CFD), namely the specific volume (υ) and specific internal energy (υ), through the use of Gibbs free energy. The Gibbs free energy formula proposed by IAPWS, formulated as a function of pressure and temperature, is used as a basis in our calculations. The Jacobian matrix resulting from the transformation between sets of variables (p, T) and (υ, u) are derived for each phase; the Newton-Raphson method is used to iteratively solve the nonlinear equations. Numerical calculations have been carried out for the entire phase diagram covering all three phases. The numerical results are compared with the original data of IAPWS and the associated errors are analyzed. It is confirmed that the pressure and temperature are accurately calculated, with largest relative error on the order of 10?? in the ice phase. Hence, other thermodynamic properties are also obtained within the same level of accuracy. The method proposed in this paper for calculating pressure and temperature, variables needed in CFD, is reliable and can be applied to the numerical simulation of multiphase flows, including phase changes.

미교란 모델을 이용한 포화 습공기 천음속 2상 유동에서의 응축현상

이장창(Jang-Chang Lee),Zvi Rusak 한국항공우주학회 2003 한국항공우주학회지 Vol.31 No.6

잠열 전달이 일어나는 얇은 익형주위의 천음속 습공기 유동에서의 마하수와 익형 두께비의 영향

이장창(J.C. Lee) 한국전산유체공학회 2012 한국전산유체공학회지 Vol.17 No.4

Once the condensation of water vapor in moist air around a thin airfoil occurs, liquid droplets nucleate. The condensation process releases heat to the surrounding gaseous components of moist air and significantly affects their thermodynamic and flow properties. As a results, variations in the aerodynamic performance of airfoils can be found. In the present work, the effects of upstream Mach number and thickness ratio of airfoil on the transonic flow of moist air around a thin airfoil are investigated by numerical analysis. The results shows that a significant condensation occurs as the upstream Mach number is increased at the fixed thickness ratio of airfoil(ε=0.12) and as the thickness ratio of airfoil is increased at the fixed upstream Mach number(M<SUB>∞</SUB>=0.80). The condensate mass fraction is also increased and dispersed widely around an airfoil as the upstream Mach number and thickness ratio of airfoil are increased. The position of shock wave for moist air flow move toward the leading edge of airfoil when it is compared with the position of shock wave for dry air.