• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2003.05a
• /
• pp.45-48
• /
• 2003

The plume interference is a complex phenomenon, consisting of plume-induced boundary layer separation, separated shear layer, multiple shock waves, and their interactions. The base knowledge of plume interference effect on powered missiles and flight vehicles is not yet adequate to get an overall insight of the flow physics in plume-freestream flow field. Computational studies are performed to better understand the flow physics of the plume-induced shock and separation for Simple, Rounded, Porous-extension test model configurations. The present study simulates highly underexpanded exhaust plume effect on missile body at the transoni $c^ersonic speeds. In order to investigate the plume-induced separation phenomenon, Simple, Rounded and Porous-extension plate are attacked to the missile afterbody. The computational result shows that the rounded afterbody and the porous-extension wall attached at the missile base can alleviate the plume-induced shock wave and separation phenomenon and improve the control of the missile body.dy.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.7 no.4
• /
• pp.33-38
• /
• 2003

The Physics of the Plume-induced shock and separation Particularly at a high Plume to exit pressure ratio and supersonic speeds up to Mach 3.0 with and without a passive control method, porous extension, were studied using computational techniques. Mass-averaged Navier-Stokes equations with the RNG $\kappa$-$\varepsilon$ turbulence model were solved using a fully implicit finite volume scheme and a 4-stage Runge-Kutta method. The control methodology for plume-afterbody interactions is to use a perforated wall attached at either the nozzle exit or the edge of the missile base. The Effect of porous wall length on plume interference is also investigated The computational results show the main effect of the porous extension on plume-afterbody interactions is to restrain the plume from strongly underexpanding during a change in flight conditions. With control, a change in porous extension length has no significant effect rut plume interference.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.8 no.1
• /
• pp.8-15
• /
• 2004

Supersonic jets impinging on $60^{\cire}$ wedge were investigated to obtain fundamental design data for jet deflector It was of interest to study flow phenomena such as shock interaction and separation induced by shear layer. Experiments using supersonic cold flow system were conducted for Schlieren flow visualization and measurement of surface pressure. Numerical results were compared with the experimental results. The major parameters are underexpansion ratio, distance from nozzle to apex and design Mach number. Flow conditions were obtained for the wedge shock to attach on or detach from the wedge. The dominant feature of flow-field is shock pattern induced by the Interaction between the wedge shock and the barrel shock.

• 한국가시화정보학회:학술대회논문집
• /
• 2002.11a
• /
• pp.117-120
• /
• 2002

An experimental research has been carried out for flow control of the shock wave/turbulent boundary-layer interaction utilizing aeroelastic mesoflaps. Various shapes and thicknesses of the mesoflap are tested to achieve different deflections of the flap, and ail the results are compared to the solid-wall reference case without flow-control mechanism. Quantitative variation of skin friction has been measured downstream of the interactions using the laser interferometer skin friction meter, and qualitative skin friction distribution has been obtained by observing the interference fringe pattern on the oil-film surface. A strong spanwise variation in the fringe patterns with a narrow region of separation near the centerline is noticed to form behind the shock structure, which phenomenon is presumed partially related to three-dimensional flow structures associated with both the sidewalls and the bottom test surface. The effect of the shape of the cavity is also observed and it is noticed that the shape of the cavity is not negligible.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2010.10a
• /
• pp.125-127
• /
• 2010

예부선 운항시 부선의 전방에 위치한 예선에 의한 유동 변화가 부선에 작용하는 동유체력 변화에 미치는 영향을 회류수조 모형시험을 통하여 분석하였다. 이를 위하여 예선에 의한 간섭영향계수를 예부선의 상태변수와 간격 거리 등의 함수로 모델링하고, 모형시험 조건을 도출하였다. 회류수조 모형시험을 수행하여 예부선 상태에 따른 간섭력 계측, 파형 변화 현상 해석, 예선 간섭 유체력 분석을 수행하였다.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.5
• /
• pp.14-18
• /
• 2004

스페클 간섭계는 빛을 이용하는 측정 방법이므로 비접촉/원격 측정 방법이며, 빛의 파장의 수십-수백 분의 1 정도의 정밀도로 측정이 가능하고, 레이저가 조사되는 영역 전체의 동시 측정이 가능하다는 장점을 가지고 있다 특히 최근에는 전자, 영상, 컴퓨터 기술의 발달에 힘입어 ESPI(Electronic Speckle Pattern interferometer; 전자 스페클 상관 간섭계) 장치가 많은 발전을 이루었고, 이에 따라 산업 현장에서의 활용도 계속 늘고 있다. (중략)

• Journal of Internet Computing and Services
• /
• v.23 no.5
• /
• pp.25-31
• /
• 2022

In ultra dense networks (UDNs), macro user equipments (MUEs) have significant interference from small-cell access points (SAPs) since a number of SAPs are deployed in the coverage of macro base stations of 5G mobile communication systems. In this paper, we propose a dynamic channel assignment scheme to increase the performance of MUEs for the uplink of UDNs even though the number of SAPs is increased. The target of the proposed dynamic channel assignment scheme is that the signal-to-interference and noise ratio (SINR) of MUEs is above a given SINR threshold assigning different subchannels to SUEs from those of MUEs. Simulation results show that the proposed dynamic channel assignment scheme outperforms others in terms of the mean MUE capacity even though the mean SUE capacity is decreased a little lower.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.42 no.3
• /
• pp.213-220
• /
• 2014

A program that predicts trajectories of projectiles influenced by the interference flow field of helicopters is developed. The interference flow field are computed using a compressible inviscid solver in conjunction with an actuator disc model. The trajectories are predicted using 6-DOF (Degree of Freedom) equations as well as an alternative form of modified point mass equations of motion. The method for the interference flow field prediction method are validated with ROBIN(ROtor Body INteraction) model. A Sierra international bullet and a 105mm projectile are used to validate the trajectory method. Trajectories of a Sierra International bullet and a HYDRA 70 rocket firing from a helicopter are predicted.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.5 no.3
• /
• pp.25-32
• /
• 2001

A passive control method of the interaction between a weak normal shock-wave and a turbulent boundary-layer was simulated using two-dimensional Navier-Stokes computations. The inflow Mach number just upstream of the normal shock wave was 1.33. A porous plate wall having a cavity underneath was used to control the shock-wave/turbulent boundary-layer interaction. The flows through the porous holes and inside the cavity were investigated to get a better understanding of the flow physics involved in this kind of passive control method. The present computations were validated by some recent wind tunnel tests. The results showed that downstream of the rear leg of the $\lambda$-shock wave the main stream inflows into the cavity, but upstream of the rear leg of the $\lambda$-shock wave the flow proceeds from the cavity toward to the main stream. The flow through the porous holes did not choke fur the present shock/boundary layer interaction.

• 한국전산유체공학회:학술대회논문집
• /
• 1995.10a
• /
• pp.213-218
• /
• 1995

마하수 4일때 초음속 풍동의 벽면과 모델지지부의 간섭에 관해 연구하였다. 특히 모델지지부 주위에서의 충격파 형성과 sting, strut 그리고 second throat에서의 반사 충격파의 상호 작용에 연구의 촛점을 두었다. 수치 기법은 내재적 플럭스 차분 분할기법 (implicit flux-difference splitting technique)을 사용하였다. 2차원과 3차원 유동해석 결과로부터 모델지지부 후류의 유동에 미치는 diffuser 출구 경계조건의 영향을 알아보았다.