• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.5
• /
• pp.35-43
• /
• 2022

Precise modeling and analysis of closed bomb test(CBT) combustion using solid propellants was performed. The fluid structure interaction(FSI) method was implemented to analyze the gas and solid phases at the same time. The Eulerian analysis method was applied for the gas phase and grain combustion, and the Lagrangian analysis method was implemented for the grain movement. The interaction between the solid phase grains and the combustion gas was fully coupled through the source term. The volume of fluid(VOF) method was used to simulate the burning distance of the grain and the movement of the combustion surface. The force acting on the grain was comprised of the pressure and gravity acting on the grain burning surface, and the grain burning rate and grain movement speed were considered in the velocity term of the VOF. The combustion analysis was performed for both one and three grains, and fairly compared with the experiments. The acoustic field during grain combustion due to pressure fluctuations was also analyzed.

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.1
• /
• pp.92-101
• /
• 2009

The purpose of this paper is to gain a greater understanding of the performance of practical wind turbine generating systems with differing output power controllers and controlling means for wind turbine speed. Subjected wind turbines, both equipped with an asynchronous power generator, are located at two sites and are defined as wind turbine A and wind turbine B in this study, respectively. Their performance differences are examined by measuring wind speed and electric parameters. The study suggests that both wind turbines have a clear linkage between current and output power fluctuations. Comparison of the fluctuations to wind speed fluctuation, although they are triggered primarily by wind speed fluctuation, clearly indicates the specific behaviors inherent to the respective turbine control mechanisms.

• The KSFM Journal of Fluid Machinery
• /
• v.12 no.3
• /
• pp.19-25
• /
• 2009

InThe purpose of this work is to analyze the flow characteristics and aerodynamic noise generated from a shroud fan at a constant 2,100 rpm using LES and FW-H noise model provided in the commercial code, FLUENT. Velocity distributions around the shroud fan obtained by using FLUENT code show good agreement with experimental results. The sound pressure level is decreased by about 6 dB as the distance from the fan increases twice. The directivity at 1st BPF shows a tendency of increasing SPL toward the axis of rotation.

• Journal of KSNVE
• /
• v.7 no.4
• /
• pp.579-588
• /
• 1997

When a membrane couples with compressive fluid, waves on the membrane follow a typical dispersion relations. One of characteristics of this relations is that evanscent waves occur below cutoff frequency. We have attempt to use this spatially decaying characteristics as a low frequency sound absorber. Theoretical development has required to solve membrane-fluid coupled linear differential. The solution has been successfully obtained by using eigenfunctions. To assure the obtained solution, experiment was also performed. The comparison was quite satisfactory. We conclude, based on these theoretical as well as experimental evidences, that it is very likely possible to use a membrane as a low frquency sound control element.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.04a
• /
• pp.215-215
• /
• 2014

현재 가장 많이 사용되고 있는 스프링식 안전밸브는 스프링과 설정치 드리프트, 누설 취약성, 채터링에 의한 시트 파손등의 문제점을 지니고 있다. 안전밸브 디스크에서 발생하는 유체 누설은 안전밸브 설정압력 개방에 영향을 주며, 시트(Seat)면의 이물질 삽입, 균열 및 유체에 의한 침식(Erosion) 등에 의해 밸브 핵심 부품이 쉽게 손상되어 기기 성능 저하를 초래하게 된다. 따라서 유체 누설을 조기에 탐지하고 정량화하여 해당 기기의 상태정보 제공을 통한 누설 감지 기법 연구가 요구된다. 원자력 발전소의 경우 밸브에서 유체가 누설되면 밸브의 오작동 및 운전 안정성 저해 요인이 된다. 따라서 본 연구에서는 음향방출법을 이용하여 안전밸브의 유체 누설을 평가하고, 안전밸브의 음향신호 측정 위치 선정 및 누설량에 따른 음향신호를 분석하고자 한다.

• Structural Engineering and Mechanics
• /
• v.51 no.6
• /
• pp.1005-1016
• /
• 2014

Roles of reactor internals are to support nuclear fuel, provide insertion and withdrawal channels of nuclear fuel control rods, and carry out core cooling. In case of functional loss of the reactor internals, it may lead to severe accidents caused by damage of nuclear fuel assembly and deterioration of reactor vessel due to attack of fallen out parts. The present study is to examine fluid flows in reactor internals subjected to hydrodynamic loads. In this context, an integrated model was developed and applied to two kinds of numerical analyses; one is to analyze periodic loading effect caused by pump pulsation and the other is to analyze random loading effect employing different turbulent models. Acoustic pressure distributions and flow velocity as well as pressure and temperature fields were calculated and compared to establish appropriate analysis techniques.

• Journal of the Korean Society of Combustion
• /
• v.16 no.1
• /
• pp.30-35
• /
• 2011

This study has been mainly motivated to numerically investigate the transient flame response to pressure oscillations in the gaseous hydrogen - liquid oxygen flames at supercritical pressures. The present analysis is based on the real-fluid transient flamlet model and the flame field is acoustically perturbed only by the sinewave oscillations in the frequency range from 1,000 Hz to 5,000 Hz. Based on numerical results, the detailed discussions are made for the flame response characteristics and the transient flamelet response associated with the high-frequency combustion instability in the liquid propellant rocket engines.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.3
• /
• pp.241-262
• /
• 2012

Some applications require structural health monitoring in inaccessible components. This paper presents a technique useful for Structural Health Monitoring of double wall structures, such as double wall steam pipes and double wall pressure vessels separated from an ultrasonic transducer by three layers. Detection has been demonstrated at distances in excess of one meter for a fixed transducer. The case presented here is for one of the layers, the middle layer, being a fluid. For certain transducer configurations the wave propagating in the fluid is a wave with low velocity and attenuation. The paper presents a model based on wave theory and finite element simulation; the experimental set-up and observations, and comparison between theory and experiment. The results provide a description of the technique, understanding of the phenomenon and its possible applications in Structural Health Monitoring.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.04a
• /
• pp.662-668
• /
• 1997

Since the structural impedance is much greater than that of medium in the most cases, we often assume that the structure is rigid and that the structural vibration is independent of medium, i.e. we usually calculate the vibration of the structure first, and then obtain the radiation sound from it. This assumption is no longer satisfied when the structural stiffness is small or the fluid impedance is comparable to it. This situation often happens in underwater acoustics. Although many researchers have studied about structural-fluid coupling, we have difficulties in solving the problem analytically. Therefore the numerical method using powerful computation leads us to obtain the various coupling problem. To understand the physical coupling phenomena, visualization of sound field by a geometrically simple system(plate-cavity coupled system) is performed experimentally. Acoustic holographic method is used to estimate sound field.

• Journal of the Korea Safety Management & Science
• /
• v.19 no.1
• /
• pp.245-255
• /
• 2017

This paper is a study to estimate the noise generated by fluid around each machine in the basement and basement facilities that accept major noise factor, pump fluid mechanical equipment installed to evaluate the impact on the real working environment. In particular, the review of the reliability of complementary information and reliability predict the natural frequency for generating a maximum strain when the vibration analysis, and intended to ensure that the design to avoid a natural frequency of the structure, on the basis of the this analysis result to the subject a real building.