• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.1-7
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• 2002

In the modern propulsion systems, requited thrust is obtained using a nozzle. Sometimes shock and induced boundary layer separation is generated in an over-expanded convergent-divergent supersonic nozzle. It occurs because the nozzle expansion ratio is too large for a given nozzle pressure ratio (NPR). This phenomenon can be explained that it redefines effective nozzle geometry, shorer nozzle geometry and lower pressure ratio, in a given pressure ratio. Numerical studies were conducted about a fixed geometry 2D nozzle in overexpanded condition and compared with Hunter's experimental result. For the numerical simulation of the supersonic nozzle, Navier-Stokes equations are considered and as a turbulent model, $\kappa$-$\varepsilon$ /$\kappa$-$\omega$ blended SST two equation turbulent model is used. The characteristics of $\lambda$-shape shock systems due to the interaction of shock and boundary layer was investigated in a low NPR. And the result of comparison of thrust value shows that a fixed geometry nozzle can cover required flight mission.

• Journal of Navigation and Port Research
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• v.31 no.1 s.117
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• pp.29-33
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• 2007

An OWC-type Wave Energy Conversion passes through 3 steps energy conversion process. This paper deal with the internal oscillating flow and effect of shape of air chamber and duct at setting place of turbine by numerical analysis using commercial CFD code, FLUENT. Air chamber and duct in OWC-type wave energy conversion are adopting sudden expanded and contracted form for high-efficiency. So, whole oscillating flow from OWC-type chamber to outlet duct through duct was solved by steady and unsteady analysis in order that flow efficiency of air chamber and duct was made better.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.10
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• pp.892-897
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• 2017

As the weapon system SW development and management manual of the DAPA, which is the regulation for the overall weapon system SW development, is revised, the level and scope of SW reliability test are upgraded to improve the reliability and quality of SW. It is a big burden for SW developers. In particular, the dynamic test requires a schedule and manpower required to implement the weapon system SW, and should be performed every time the source code changes, not just one time. In this paper, we propose a regression test automation program(VectorCast Environment Manager) that performs a dynamic test using VectorCast, a dynamic test tool, and then performs a regression test automatically by minimizing human intervention in the regression test of dynamic test due to the change of the source code.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.6
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• pp.530-536
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• 2010

In-flight icing is a critical technical issue for aircraft safety and, in particular, ice accretions on aircraft surfaces can drastically impair aerodynamic performances and control authority. In order to investigate icing effects on the aerodynamic characteristics of KC-100 aircraft, a state-of-the-art CFD code, FENSAP-ICE, was used. A main wing section and full configuration of KC-100 aircraft were considered for the icing analysis. Also, shapes of iced area were calculated for the design of anti-/de-icing devices. The iced areas around leading edge of main wing and horizontal tail wing were observed maximum 7.07% and 11.2% of the chord length of wing section, respectively. In case of wind shield, 16.7% of its area turned out to be covered by ice. The lift of KC-100 aircraft were decreased to 64.3%, while the drag was increased to 55.2%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.9
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• pp.605-612
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• 2016

In this study, numerical simulations were conducted for conjugate heat transfer around ice balls in an encapsulated ice thermal storage system. Four shapes of ice balls were modeled; the default one was a sphere, and the other three shapes were designed to enhance convective heat transfer through the ball surface. The flow around the ball was laminar, for which the Reynolds number was 300, and both forced and natural convections inside and outside the balls were considered. The simulations revealed that the magnitude of convective heat transfer for the different shapes decreased in the following order: bone, dimple, hole, and sphere. For the entire simulation, the maximum difference in the average temperatures of water inside the capsules was found to be $0.9^{\circ}C$. Therefore, it can be said that the effect of ice-ball shape on the performance of the ice thermal storage system is significant, considering that more than 0.3 million balls are used in this system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.10
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• pp.877-886
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• 2016

A validation study is conducted for the conceptual design and performance analysis of UH-60A Black Hawk in order to establish the conceptual design and performance analysis techniques for conventional helicopters using a single main rotor and a tail rotor. As a tool for conceptual design and analysis, NDARC(NASA Design and Analysis of Rotorcraft) is used for the present study. The conceptual design for UH-60A is successfully validated as compared with the target values. Then, various performance analyses in hover and forward flight are conducted for the UH-60A model obtained from the present design work, and they are compared well with the wind tunnel test, flight test, and previous analyses using various analysis tools. Through this validation work, the conceptual design and performance analysis techniques for the conventional helicopter are appropriately established.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.3
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• pp.204-212
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• 2015

The infrared lock-on range of target aircraft plays a critical role in determining the aircraft survivability. In this investigation, the effects of various UAV engine nozzle configurations on the aircraft lock-on range were theoretically analyzed. A virtual subsonic aircraft was proposed first, based on the mission requirement and the engine performance analysis, and convergent-type nozzles were then designed. After determining thermal flow field and nozzle surface temperature distribution with the CFD code, an additional analysis was conducted to predict the IR signature. Also, atmospheric transmissivity for various latitude and seasons was calculated, using the LOWTRAN code. Finally, the lock-on and lethal envelopes were calculated for different nozzle configurations, assuming the sensor threshold of the given IR guided missile. It was shown that the maximum 55.3% reduction in lock-on range is possible for deformed nozzles with the high aspect ratio.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.1-10
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• 2006

An optimization study on a small turbopump impeller operating at the low specific speed is conducted to obtain high output head at the impeller exit. Its specific speed in SI unit (RPM, m3/sec, m) is 4.0, and the outer diameter is 56mm. On the optimization, the outer diameter of the impeller is maintained constant to restrict the pump size, and an objective function of pressure head is maximized with eight design variables, which are related with designing an impeller shape. The response surface method is used to the optimization scheme, and the commercial code CFX-10 is applied for numerical analysis. The pressure head of the objective function obtained with an optimized impeller is increased by 9.7% compared with that obtained on an impeller designed with typically recommended design parameters. This increment is caused by reducing the recirculation region within the impeller passage.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.39-44
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• 2006

An OWC-type Wave Energy Conversion passes through 3 steps energy conversion process. This paper deal with the internal oscillating flow and effect of shape of air chamber and duct at setting place of turbine by numerical analysis using commercial CFD code, FLUENT. Air chamber and duct in OWC-type wave energy conversion are adopting sudden expanded and contracted form for high-efficiency. So, whole oscillating flow from OWC-type chamber to outlet duct through duct was solved by steady and unsteady analysis in order that flow efficiency of air chamber and duct was made better.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1065-1072
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• 2014

The shape of an impeller splitter for a dual-inlet centrifugal blower was optimized to enhance the blower performance. Two design variable, the normalized chord and pitch of a splitter, were used to evaluate the blower performance and internal flow fields based on the three-dimensional flow analysis. The blower performance obtained using this numerical simulation had a maximum error of 4 percent compared to that in an experiment at the design flow condition. The shape optimization of the splitter successfully increased the blower efficiency and pressure by 3.65 and 1.14 percent compared to the reference values. The blower performance was increased by reducing the flow separation near the blade suction surface by optimizing the shape of the splitter, which produced a pressure increase at the outlet of the volute casing.