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2-방정식 난류모델을 이용한 스포일러 천이적 공력특성의 파라메트릭 연구
최성욱(S. W. Choi),장근식(K. S. Chang),옥호남(H. N. Ok) 한국전산유체공학회 2000 한국전산유체공학회 학술대회논문집 Vol.2000 No.10
The transient response of an airfoil to a rapidly deploying spoiler is numerically investigated using the turbulent compressible Navier-Stokes equations in two dimensions. Algebraic Baldwin-Lomax model, Wilcox k- ω model, and SST k- ω turbulence model are used to calculate the unsteady separated flow due to the rapid spoiler deployment. The spoiler motion relative to a stationary airfoil is treated by an overset grid bounded by a Dynamic Domain-Dividing Line which has been devised by the authors. The adverse effects of the spoiler influenced by the spoiler location and the hinge gap are expounded. The numerical results are in reasonably good agreement with the existing experimental data.
기체 흐름에 고체입자가 섞인 파이프 내의 이상유동에 대한 수치해석
박순일(S. I. Pak),장근식(K. S. Chang) 한국전산유체공학회 2002 한국전산유체공학회 학술대회논문집 Vol.2002 No.-
A numerical simulation was made to determine the motion of particles in the fluid. The simulation is based on the Eulerian-Lagrangian method. The fluid motion was solved using a PISO-based finite-element method and a k-ε model of turbulence. In the Lagrangian method for the solid phase, the trajectories of particles are calculated by integrating the equations of motion of a single particle, and the collision between particles are taken into account. The influence of particles on the fluid phase is taken into account by introducing source terms in the Eulerian equations govering the fluid flow. It is known as the particle-source-in-cell (PSIC) method. Also, the turbulent effect in the particles and fluid motion is considered. The numerical results were compared with the experiment for a two-phase flow in a vertical pipe.
다중 블록 격자를 이용한 원뿔 직관 모양의 벌류트 유동의 수치해석
배황(H. Bae),강현구(H.G. Kang),윤주식(J.S. Yoon),박기철(K.C. Park),장근식(K.S. Chang) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.1
Numerical investigation of a centrifugal compressor volute having a modified straight conical duct has been made. Three-dimensional Reynolds-Averaged Navier-Stokes equations with k-ε turbulence equation are solved To avoid coordinate singularity at the central axis of the duct, multi-block H-type grid is generated on the circular cross-sections of the volute and stretched toward the solid wall boundary. We obtained numerical results with three different mass flow rates at the volute inlet, namely, with the inlet conditions that give small, medium and large mass flow rates at the outlet of the conical duct. Agreement with the experimental results is observed.
장세명(S.M. Chang),정연규(Y.G. Jung),김사지(S.J. Kim),송찬이(C.Y. Song),장근식(K.S. Chang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Extracorporeal Shock Wave Therapy (ESWT) is known a very effective clinical treatment against persistent musculo-skeletal pains that do not respond with the conservative medical therapy. In the hydroelctric type ESWT, shock waves are generated by the electric sparks between two electrodes a few milimeters apart charged in tens of thousand volts, immersed in water and located at the first focal point of an ellipsoidal reflector. Then the shock is focused at the second focal point of the reflector for clinical use. The shock wave is bombarded thousand of times on the target area positioned at the second focal point. In this medical equipment, there is lots of obscurity in the physical and biological effect. We first make CFD analysis to expound the shock focusing process of this pressure device.
액적이 있는 비점성 공기유동 모델을 이용한 구름속의 천음속 에어포일 수치해석
염금수(G.S. Yeom),장근식(K.S. Chang),백승욱(S.W. Baek) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
In this paper, the problem of transonic aerodynamic characteristics of a NACA0012 airfoil is numerically investigated in the inviscid gas-droplet two-phase flow with the compressible two-fluid model. In the present study, the airfoil flight in the cloud is simulated by taking account of the viscous drag of the droplets, the heat transfer, the phase change, and the droplet fragmentation. The two-fluid equation system is solved by the fractional-step method and the WAF-HLL scheme. The effects of size and volume fraction of the droplets on the flow characteristics of the airfoil in the cloud are elaborated and discussed.
Eulerian-Lagrangian 방법에서 입자 및 유동 격자계 분리를 통한 2상 유동의 효율적 계산
박순일(S.I. Pak),이진규(J.K. Lee),장근식(K.S. Chang) 한국전산유체공학회 2003 한국전산유체공학회 학술대회논문집 Vol.2003 No.-
When the Eulerian-Lagrangian method is used to analyze the particle laden two-phase flow, a large number of particles should be used to obtain statistically meaningful solutions. Then it takes too much time to track the particles and to average the particle properties in the numerical analysis of two-phase flow. The purpose of this paper is to reduce the computation time by means of a set of particle gird separate to the flow grid. Particle motion equation here is the simplified B-B-O equation, which is integrated to get the particle trajectories. Panicle turbulent dispersion, wall collision, and wall roughness effects are considered but the two-way coupling effects between gas and particles are neglected. Particle laden 2-D channel flow is solved and it is shown that the computational efficiency is indeed improved by using the current method