• Proceedings of the KSME Conference
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• 2003.11a
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• pp.580-585
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• 2003

The present study addresses experimental results to investigate the details of the near field flow structures produced in the under-expanded, dual, coaxial, swirling, jet. The sonic/supersonic swirling jets are emitted from the sonic inner nozzle and the outer annular nozzle produce the co-swirling and counter swirling against the primary swirling jet, respectively. The interactions between both the secondary annular swirling and primary inner supersonic swirling jets are quantified by the pitot impact and static pressure measurements and visualized by using the Schliern optical method. The experiment is performed for different swirl intensity and pressure ratio. The results obtained show that the secondary co-swirling jet significantly changes the inner under-expanded swirling jet, such as the recirculation zone, pressure distribution, through strong interactions between both the swirling jets and the effects of the secondary counter-swirling jet is similar to the secondary co-swirl jet case.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.3
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• pp.10-18
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• 2001

In this paper, Supersonic jets impinging on a wedge were investigated in order to acquire fundamental design data for jet deflectors. Surface pressure distributions and pressure contours were obtained using a cold flow tester producing Mach 2 supersonic jets. Schlieren system was used to visualize the flow structure on the wedge surface. Numerical computations were performed and compared with the experimental results. Both results were in good agreement. The results showed that underexpansion ratio did not affect on the surface pressure distribution when the wedge is located at the nozzle exit. With increasing underexpansion ratio, pressure recovery decreased as the wedge is located farther from the nozzle exit. In the pressure contour, it was possible to locate the region where the peak pressure on the wedge surface was occurred.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.10-20
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• 2019

Recently, fluidic thrust vector control has become a core technique to control multifarious air vehicles, such as supersonic aircraft and modern rockets. Fluidic thrust vector control using the shock vector concept has many advantages for achieving great vectoring performance, such as fast vectoring response, simple structure, and low weight. In this paper, computational fluid dynamics methods are used to study a three-dimensional rectangular supersonic nozzle with a slot injector. To evaluate the reliability and stability of computational methodology, the numerical results were validated with experimental data. The pressure distributions along the upper and lower nozzle walls in the symmetry plane showed an excellent match with the test results. Several numerical simulations were performed based on the shear stress transport(SST) $k-{\omega}$ turbulence model. The effect of the momentum flux ratio was investigated thoroughly, and the performance variations have been clearly illustrated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.1-8
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• 2019

An experimental study is performed to observe the characteristics of the thrust vectoring control (TVC) of the supersonic jet using proportional control valves. It is observed that three different TVC characteristics exist as the nozzle pressure ratio varies. Strong hysteresis phenomena are also observed during the valve control for a certain range of the nozzle pressure ratio. It is also noticed that the secondary chamber pressure is one of the influencing parameters for the TVC. Therefore, a control algorithm utilizing the secondary chamber pressure coefficient as a predictor is applied to achieve the stable TVC avoiding the hysteresis. Consequently, the stable TVC with the maximum deflection angle of about 20-degree has been realized using the proportional control valves.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.1
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• pp.91-96
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• 2014

The aim of this work is to determine supersonic nozzle profiles that are used in propulsion, for launchers or embarked with satellites. This design has the role of firstly, providing important propulsion, i.e. with uniform and parallel flow at exit; and secondly, to find short length profiles, without modification of the flow in the nozzle. The first elaborate program is used to determine the profile of the divergent, by using the characteristics method for an axisymmetric flow. The second program is conceived by using the finite volume method, to determine and test the profile found connected to a convergent.

• Journal of the Korean Mathematical Society
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• v.54 no.1
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• pp.141-175
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• 2017

We present a high-resolution van Leer-type numerical scheme for the isentropic model of fluid flows in a nozzle with variable cross-section. Basically, the scheme is an improvement of the Godunov-type scheme. The scheme is shown to be well-balanced, as it can capture exactly equilibrium states. Numerical tests are conducted which include comparisons between the van Leer-type scheme and the Godunov-type scheme. It is shown that the van Leer-type scheme achieves a very good accuracy for initial data belong to both supersonic and supersonic regions, and the exact solution eventually possesses a resonant phenomenon.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.491-496
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• 2000

The physics of the flow field surrounding an engine nacelle afterbody is very complex. A high pressure jet from the nozzle interacts with the external flow and causes upstream influence on the afterbody surface field. At certain conditions, the nozzle boundary layer can separate, either by shock wave interaction or by adverse pressure gradient effect, resulting in a severe drag penalty. Furthermore, a finite afterbody base implies a recirculating flow region. A flow modeling method has been developed to analyze the flow in the annular base(rear-facing surface) of a circular engine nacelle flying at subsonic speed but with a supersonic exhause jet. Real values of exhaust gas properties and temperature are included.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.71-77
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• 2000

An axisymmetric supersonic jet is simulated at a Mach number of 1.5 and a Reynolds number of $10^5$ to identify the mechanism of sound radiation from the jet. The present simulation is performed based on the high-order accuracy and high-resolution ENO(Essentially Non-Oscillatory) schemes to capture the time-dependent flow structure representing the sound source. In this simulation, optimum expansion jet is selected as a target, where the pressure at nozzle exit is equal to that of the ambient pressure, to see pure shear layer growth without effect of change in jet cross section due to expansion or shock wave generated at nozzle exit. Shock waves are generated near vortex rings, and discernible pressure waves called Mach wave are radiated in the downstream direction with an angle from the jet axis, which is characteristic of high speed jet noise. Furthermore, vortex roll-up phenomena are observed through the visualization of vorticity contours.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.547-550
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• 2008

A solid rocket motor has quite complex physical condition such exothermal chemical reaction in subsonic area and supersonic ex pansion in a converging-diverging nozzle. To introduce a simulation tool for compressible flow in supersonic range as well as incompressible chemical reaction zone in a whole rocket nozzle is a essential demand. Since the flow vary subsonic to super sonic, the convergence in computation becomes very low and unstable in a whole domain of rocket motor. This paper reports the 2-D Axisymmetric and simple 3-D solid propellant combustion and flow of gases in rocket motor by using a precondi tioning, shear stress turbulence modeling, AUSM(p). To simulate the simplified combustion process, Double base solid propellant is used to calculate reaction of solid propellant.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.337-342
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• 2013

이번 연구에서는 de Laval nozzle를 이용하여 다양한 유체해석 모델과 프로그램을 비교하여 그 성능을 파악하였다. de Laval nozzle은 eigenvalue에 의해 eigenvector값이 '-'와 '+'값을 동시에 갖는 물리현상을 내포하고 있으며, 압력조건에 따라 내부에서 Normal shock이 발생하게 된다. 이러한 non-linearity를 현재 우리가 주로 사용하고 있는 상용프로그램(cfx, fluent)과 EDISON, 직접 코딩한 프로그램(Matlab이용)이 얼마나 잘 표현하는지 알아보았다. 그 결과 Van Leer Vector Splitting을 이용할 경우 물리현상을 제일 잘 표현 하였다. 또한 난류 유동(Turbulence flow)을 고려하게 될 경우, Mesh가 Boundary layer를 표현할 정도로 정밀하지 못하다면 제대로 된 해석 결과를 얻을 수 없었으며, Wall 근처에서 Non-slip condition에 의해 Vortex가 형성되고, 이 Vortex가 Back flow를 유도하여 해가 수렴하는데 방해를 하게 됨을 알 수 있었다. 이를 방지하기 위해서는 유동이 잘 표현될 수 있도록 적절한 Computational environment를 형성해 주는 것이 매우 중요하다.