• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2014년도 춘계학술대회
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• pp.244-245
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• 2014

Recently, the studies on submerged breakwater are increased due to needs considering the quality of water and the scenic view. In this paper, waves coming to permeable submerged breakwater coming with oblique angle are computed numerically by using wave pressure function. The wave pressure function throughout the analytical region including the fluid and submerged breakwaters is used. An unknown quantity expressed by the wave pressure function is simulated by boundary element method. The maximum reflection coefficient shows the tendency of decrease with the increase of oblique angle and The reflection coefficient shows the tendency of increase with the increase of the values of the linear dissipation coefficient and the added mass coefficient. It is means that the reflection coefficients are strongly dependent on the oblique angle and resistance coefficients.

• 유공압시스템학회논문집
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• 제3권2호
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• pp.21-26
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• 2006

With the increasing concerns on noise and vibration in hydraulic fluid power systems, it is important to find better way to reduce noise and vibration. In this study, the authors survey former researches on hose(viscoelastic tube) modeling in advance. And a summary of several existing methods for measuring the speed of sound in the fluid in pipes is presented. Their basic principles, advantages and limitations are compared. And The authors suggest a far simple identification procedure to obtain wave speed in hose by just using an experimental pressure data for the object tube with hose. In the new procedure, flow in hose is basically modeled by transfer matrix method, and wave speed in hose is obtained as data in frequency series. The wave speed in hose as data in frequency series will be used to compute the pressure pulsation attenuation in hydraulic pipe systems. The computed results are compared with the experimental ones, and the validity of the new procedure to obtain wave speed in hose is confirmed

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권3호
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• pp.329-347
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• 2018

The Smoothed Particle Hydrodynamics (SPH) method has proved to have great potentials in dealing with the wave-structure interactions. Compared with the Weakly Compressible SPH (WCSPH) method, the ISPH approach solves the pressure by using the pressure Poisson equation rather than the equation of state. This could provide a more stable and accurate pressure field that is important in the study of wave-structure interactions. This paper improves the solid boundary treatment of ISPH by using a high accuracy Simplified Finite Difference Interpolation (SFDI) scheme for the 2D wave-structure coupling problems, especially for free-moving structure. The proposed method is referred as the ISPH_BS. The model improvement is demonstrated by the documented benchmark tests and laboratory experiment covering various wave-structure interaction applications.

• 대한기계학회논문집B
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• 제23권1호
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• pp.58-68
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• 1999

The entry compression wave, which forms at the entrance of a high-speed railway tunnel, is closely related to the pressure transients in the train/tunnel systems as well as an impulsive noise appearing at the exit of the tunnel. In order to alleviate such undesirable phenomena, some control strategies have been applied to the compression wave propagating inside the tunnel. The objective of the current work is to investigate the effect of tunnel entrance hoods on the entry compression wave at the vicinity of the tunnel entrance. Three types of entrance hoods were tested by the numerical method using the characteristics of method for a wide range of train speeds. The results show that the maximum pressure gradient of compression wave can be considerably reduced by the tunnel entrance hood. Optimum hood shape necessary to reduce the pressure transients and impulsive noise was found to be of an abrupt type hood with its cross-sectional area 2.5 times the tunnel area. It is believed that the current results are highly useful in predicting the effects of entrance hoods and in choosing the shape of proper hood.

• 한국해양공학회지
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• 제24권2호
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• pp.1-9
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• 2010

Oscillating Water Column is one of the most widely used converting systems all over the world. The operating performance is influenced by the efficiencies of the two converting stages in the OWC chamber-turbine integrated system. In order to study the effects of the pressure drop induced by the air turbine, the experiments using the impulse turbine and the orifice device are carried out in the wave simulator test rig. The numerical simulation utilizing the orifice and porous media modules is calculated and validated by the corresponding experimental data. The numerical wave tank based on the two-phase VOF model embedded with the above modules is employed to investigate the wave elevation, pressure variation inside the chamber and the air flow velocity in the duct. The effects of the air turbine on the integrated system and interaction among the wave elevation, pressure and air flow velocities variations are investigated, which demonstrates that the present numerical model are more accurate to be employed.

• Journal of Mechanical Science and Technology
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• 제20권4호
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• pp.482-493
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• 2006

The carbody structure of a high speed train passing through a tunnel is subjected to pressure fluctuation. Fatigue strength of the carbody structure against the fluctuating pressure loading should be proved in the design stage for safety. In this study, to get the useful information on the pressure fluctuation in the tunnel, measurement has been conducted during test running of KHST on the high speed line for two years. The measured results were analyzed and arranged to be used for carbody design. A prediction method for the magnitude and frequency of pressure change was proposed and the propagating characteristics of pressure wave was investigated. By statistical analysis for the measured results, a pressure loading spectrum for the high speed train was given. The proposed method can also be used to estimate the pressure loading spectrum for new high speed line at design stage combined with the results of train performance simulation.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.152-160
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• 2004

Studies to investigate the influence on hydraulic acoustic wave were conducted using pressure swirl atomizer under making frequency range from 0 to 60Hz using water as a propellant. Pressure oscillation from hydraulic sources gives a strong influences on atomization and mixing processes. The ability to drive these low frequency pressure oscillations makes spray characteristics changeable. The effect of pressure perturbation and its spray characteristics showed that low injector pressure with pressure pulsation gives more significantly than high injector pressure with pressure perturbation in SMD, spray cone angle, breakup length. Moreover, this data could be used for prediction of low combustion instability getting G factor.

• 설비공학논문집
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• 제18권1호
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• pp.17-23
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• 2006

This study is to investigate the pressure wave characteristics and the maximum pressure rise generated by instantaneous valve closure at the end of the straightening polybutylene piping system. Experiments were conducted under the following conditions: initial pressure $1\~5$ bar, flow velocity $\~0.5-3.0m/s$ and water temperature $25^{\circ}C$. Results indicated that the peak pressure generated by quick valve closure reached Joukowsky's value. We also found that the maximum pressure rise and the pressure history depended on not only initial steady pressure but also flow velocity.

• 한국해안·해양공학회논문집
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• 제23권1호
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• pp.79-92
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• 2011

본 연구에서는 투과성구조물에서 우수한 파랑제어기능을 발휘하는 것으로 잘 알려져 있는 슬리트케이슨제 중에 기본형인 연직벽형 횡슬리트케이슨제가 불투과성지반 및 투과성지반상에 설치된 조건하에 구조물에 작용하는 단주기파랑 및 지진해일파에 의한 파압의 특성을 논의한다. 투과성지반의 해석에서는 공극율을 편의상 0.4로 가정하여 2차원 및 3차원수치해석을 수행하고, 불투과성의 경우와 그의 차이를 비교 검토한다. 이 때, 입사파랑의 조건으로는 설계파랑으로 일반적으로 고려되는 단주기파랑과 그의 진폭과 동일한 크기로 내습하는 지진해일파(고립파 혹은 단파)를 고려하며, 슬리트케이슨제의 전면유공부 및 유수실 내부의 불투과벽체에 작용하는 파압을 대상으로 한다. 해석에서는 기체와 액체의 혼상동적현상을 하나의 지배방정식으로 해석하는 이상류(二相流) 모델에 기초한 2차원 및 3차원수치파동수로를 각각 적용한다. 얻어진 수치해석결과에 의하면, 슬리트케이슨제의 전면유공부에서는 단주기 파랑에 비해 지진해일파의 작용파압이 약 3~5배 높은 값을 나타내고, 유수실 내부벽에서는 약 2~4배 높은 값을 각각 나타낸다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1643-1648
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• 2004

When a shock wave propagates into a Helmholtz resonator, very complicated wave phenomena are formed both inside and outside the resonator tube. Shock wave reflection, shock focusing phenomena and shock-vortex interactions cause strong pressure fluctuations inside the resonator, consequently leading to powerful sound emission. In the present study, the wave phenomena inside and outside the Helmholtz resonator are, in detail, investigated with a help of CFD. The Mach number of the incident shock wave is varied below 2.0 and several types of resonators are tested to investigate the influence of resonator geometry on the wave phenomena. A TVD scheme is employed to solve the axisymmetric, compressible, Euler equations. The results obtained show that the configuration of the Helmholtz resonator significantly affects the peak pressure of shock wave focusing, its location, the amplitude of the discharged wave and resonance frequency.