• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1998년도 춘계 학술대회논문집
• /
• pp.168-173
• /
• 1998

A numerical analysis of axisymetric backward facing step main nozzle flow in air jet loom has been accomplished. To obtain basic design data for an optimum main nozzle for an air-jet loom and to predict the transonic/supersonic flow, a characteristic based upwind flux difference splitting compressible Navier-Stokes method has been used. The wall static pressure of the main nozzle and the flow velocity changes in the nozzle tube were analyzed by changing air tank pressures and acceleration tube lengths. The flow inside the nozzle experiences double choking one at the needle tip and the other at the acceleration tube exit at tank pressures over $4kg_f/cm^2$. The tank pressure $P_t$ leading to the critical condition depends on the acceleration tube length; i.e, $P_t$ is higher for longer acceleration tubes. The $P_t$ value required to bring the acceleration tube exit to the critical condition is nearly constant regardless of acceleration tube length. The round needle tip shape might lead to less total pressure loss when compared with step shape.

• 대한기계학회논문집B
• /
• 제21권12호
• /
• pp.1624-1634
• /
• 1997

A numerical study on two-dimensional unsteady transonic cascade flow has been performed by adopting dual time stepping and the k-.omega. turbulence model. An explicit 4 stage Runge-Kutta scheme for the compressible Navier-Stokes equations and an implicit Gauss-Seidel iteration scheme for the k-.omega. turbulence model are proposed for fictitious time stepping. This mixed time stepping scheme ensures the stability of numerical computation and exhibits a good convergence property with less computation time. Typical steady-state convergence accelerating schemes such as local time stepping, residual smoothing and multigrid combined with dual time stepping shows good convergence properties. Numerical results are presented for unsteady laminar flow past a cylinder and turbulent shock buffeting problem for bicircular arc cascade flow is discussed.

• 대한기계학회논문집
• /
• 제14권5호
• /
• pp.1244-1253
• /
• 1990

본 연구에서는 Denton이 제시한 개선된 시간진행법을 이용하여 2차원 직선 정 지 익렬의 유동해석 프로그램의 개발을 목적으로 하고 있으며 기존 프로그램의 안정성 과 수렴의 개선에 역점을 두고 진행하였다. 수치계산 결과는 타당성을 입증하기 위 하여 실험결과 및 Braembussche의 특이점법 수치계산 결과와 비교 검토 하였으며 충격 파가 존재하는 천이음속의 유동에 대하여 수치계산을 실시하였다.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 12th Asian Congress of Fluid Mechanics
• /
• pp.51.1-51.1
• /
• 2008

• 한국항공우주학회지
• /
• 제34권5호
• /
• pp.12-18
• /
• 2006

고속 항공기의 천음속 버펫 발단을 예측할 수 있는 새로운 정상 접근 방법을 개발하였다. 본 논문에서는 버펫 발단까지 정상 유동장으로 가정하였다. 본 연구는 다양한 정적 공력 변수들의 급격한 변화 분석을 포함하고 있다. 이러한 급격한 변화는 천음속 버펫의 발단을 지시한다. 본 연구에서 고려된 다양한 공력 변수 가운데 압력 중심점 변화가 가장 명확한 천음속 충격파 버펫 발단 지시자임을 보여준다. 이러한 새로운 정상 접근 방법은 박리기포를 수반하는 익형이나 큰 후퇴각과 작은 종횡비를 갖는 날개의 천음속 버펫 발단 예측에 적용할 수 있다. 버펫 시험결과와 비교하여 좋은 일치를 얻었다. 새로운 정적 접근 방법 결과를 기초로, 압력 중심점 변화 곡선의 급격한 기울기 변화는 항공기 전 기체 형상에 대한 정상 시험 방법 버펫 발단 지시자로 새롭게 제시할 수 있다.

• 한국항공우주학회지
• /
• 제46권6호
• /
• pp.445-451
• /
• 2018

본 논문에서는 현재 한국항공우주학회 공기역학부문위원회에서 주관하고 있는 EFD-CFD 비교 워크숍의 여러 과제 중 CASE 4 삼각날개(Delta Wing)의 천음속영역의 유동해석 결과를 작성하였다. 풍동실험은 추후에 진행될 예정이며, -5~20도 받음각 영역에서의 CFD 해석을 수행하였다. 해석을 수행한 마하수는 0.7, 0.85, 1.2이다. 삼각날개의 적합한 해석조건을 찾기 위해서 기준격자 크기를 조절하여 격자의존성 해석을 수행하였고, 선택한 격자로 받음각 변화에 따라 양력계수와 항력계수의 경향을 파악하였다.

• 한국유체기계학회 논문집
• /
• 제14권6호
• /
• pp.96-101
• /
• 2011

Korea Aerospace Research Institute is performing 3 stage transonic axial compressor development program. This paper introduces design step of the compressor, the performance test results and its analysis. In the fore part of the paper, aerodynamic process of the 3 stage axial compressor is presented. To satisfy both of the mass flow and pressure rise, the compressor should rotate at a high rotational speed. Therefore the transonic flow field forms in the rotor stages and it is designed with a relatively high pressure rise per stage to satisfy its design target. The compressor stage consists of 3 stages, and the bulk pressure ratio is 2.5. The first stage is burdened with the highest pressure ratio and less pressure rises occur in the following stages. Also it is designed that tip Mach number of the first rotor row does not exceed 1.3, while the maximum relative Mach number in the rotor stage is between 1.3~1.4 to increase the compressor flow coefficient. The final design has been confirmed by iterating three dimensional CFD calculations to verify design target and some design intentions. In the latter part of the paper, its performance test processes and results are presented. The performance test result shows that the overall compressor performance targets; pressure ratio and efficiency are well achieved. The stator static pressure distributions show that the blade loading is gradually increasing from the downstream of the compressor.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2008년도 추계학술대회논문집
• /
• pp.167-174
• /
• 2008

In this study, flutter analyses for supercritical airfoil have been conducted in transonic region. Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate detailed static and dynamic responses of supercritical airfoil. Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras (S-A) and SST ${\kappa}-{\omega}$ turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of cascades for fluid-structure interaction (FSI) problems. Also, flow-induced vibration (FIV) analyses for various supercritical airfoil models have been conducted. Detailed flutter responses for supercritical are presented to show the physical performance and vibration characteristics in various angle of attack.

• 한국항공운항학회지
• /
• 제17권2호
• /
• pp.8-17
• /
• 2009

In this study, flutter analyses for supercritical airfoil have been conducted in transonic region. Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate detailed static and dynamic responses of supercritical airfoil. Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras (S-A) and SST ${\kappa}-{\omega}$ turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of cascades for fluid-structure interaction (FSI) problems. Also, flow-induced vibration (FIV) analyses for various supercritical airfoil models have been conducted. Detailed flutter responses for supercritical are presented to show the physical performance and vibration characteristics in various angle of attack.

• 한국전산유체공학회지
• /
• 제13권4호
• /
• pp.66-71
• /
• 2008

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 $17^{\circ}$. Here the maximum lift occurred at $18^{\circ}$ according to the angle of attack. And the minimum drag is expected at $-2^{\circ}$. 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.