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김영철(Y.C. Kim),최종욱(J.W. Choi),김성초(S.C. Kim) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.1
Thermal-fluid analysis is performed numerically to figure out the characteristics of heat transfer in a thermosyphon varying with the aspect ratio of geometry and the filling ratio of working fluid. The computational results are reasonable compared with the experimental data and visualized. The thermal resistance and the convective heat transfer coefficients are evaluated with the aspect ratio of thermosyphon and the filling ratio of working fluid, respectively. In conclusion, the thermal resistance decreases as the length of evaporator increases. However, the variation of a condenser length is nearly independent on the thermal resistance. In order to raise the performance of thermosyphon, the working fluid needs to be filled over 75%. In addition, Nusselt numbers in the evaporator and the condenser show 275 and 304, respectively.
김양균(Y.K. Kim),김성초(S.C. Kim),최종욱(J.W. Choi),김정수(J.S. Kim) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.4
This research computes the viscous flow field and aerodynamics around the model of a commercial passenger airplane, Boeing 747-400, which cruises in transonic speed. The configuration was realized through the reverse engineering based on the photo scanning measurement. In results, the pressure coefficients at the several wing section on the wing surface of the airplane was described and discussed to obtain the physical meaning. The lift coefficient increased almost linearly up to 17°. Here the maximum lift occurred at 18° according to the angle of attack And the minimum drag is expected at -2°. The maximum lift coefficient occurred at the Mach number 0.89, and the drag coefficient rapidly increased after the Mach number of 0.92. Also shear-stress transport model predicts slightly lower aerodynamic coefficients than other models and Chen’s model shows the highest aerodynamic values. The aerodynamic performance of the airplane elements was presented.
진동형 히트 파이프에서 튜브의 지름과 개수에 따른 전산 열유동해석
한성현(S.H. Han),최종욱(J.W. Choi),김성초(S.C. Kim) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.1
In this paper, heat transfer characteristics of pulsating heat pipes are investigated with the diameter and the number of tubes through the computational analysis of thermal flow. The numerical simulation includes the phase change precess with VOF model using OpenFOAM software. The numerical code is modified for the phase change to occur with saturation temperature. The numerical results are compared with the previous ones to validate the present code. The resonable results have been obtained based on the mass transfer time relaxation parameter considering the density ratio. When the ratio of length to diameter and the number of tubes are on the decrease, the thermal resistances also tends to decrease in the pulsating heat pipes. These numerical results will supply the base line data to design and to manufacture the pulsating heat pipe.
윤용현(Y.H Yoon),김성초(S.C. Kim),조환기(H.K Cho),이상현(S.H. Lee) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.4
New design configurations were developed based on the closed ventilation type igloo nozzle in contrast to the conventional open distribution type. To validate the enhanced performance, the prediction of the exhaust flow patterns of the igloo diffuser was carried out by both experimental and computational simulations. CFD provided detailed parametric studies that significantly reduced the amount of experimentation necessary to alter the design of existing the F-15K igloo exhaust diffuser.
공개 소스코드를 이용한 진동형 히트파이프에 대한 수치해석
최종욱(J.W. Choi),김성초(S.C. Kim) 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.3
The phase change and the thermal fluid flow were simulated in a pulsating heat pipe using OpenFOAM source code. The interPhaseChangeFoam was chosen as a solver, which could compute the phase change of water and vapor. The mass transfer parameters were used to keep the mass balance of the evaporation and the condensation in the phase change process. The pressure equation was modified and the temperature equation was added in the interPhaseChangeFoam to circulate the working fluids. The volume fractions of water and vapor were visualized in the pulsating heat pipe. In order to verify the results of the numerical analysis, the thermal resistances of the pulsating heat pipe were calculated with input power and compared with the previous research data. As a result, the thermal resistances decreased with input power and the trend was similar to that of the previous results.
유영현(Y.H. Yoo),최종욱(J.W. Choi),김성초(S.C. Kim),김정수(J.S. Kim) 한국전산유체공학회 2008 한국전산유체공학회 학술대회논문집 Vol.2008 No.-
The changing process from hovering mode to transition one is of importance to determine a stability of tilt-rotor aircraft, which is utilized in UAV(Unmaned Aerial Vehicle). The analysis on fluid flows and aerodynamic characteristics according to variation of tilting angle of rotor is essential step in development of tilt-rotor. In the present study, the computation domain is divided into the rotating and stationary regions in order to consider the rotating blades. For the convenient realization of various tilting angle as well as application of boundary condition, the whole computation region is constructed into sphere domain. The near farfield boundary condition is adopted. The airfoil used in computation is NACA 0012. The computation results for the hovering mode are validated by comparing with previously conducted experimental results. From the results, the flow fields around rotor blade and the aerodynamic characteristics in transition mode are observed. The computational result will provide the basis for development and performance evaluation of tilt-type aircraft.