• 한국자동차공학회논문집
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• 제12권2호
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• pp.109-116
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• 2004

Bent-axis piston pump have been commonly used in hydraulic systems because of high pressure level, best efficiency, low shear force on pistons and low operating costs. The other side, they have a few demerits like that they have the relatively high number of moving parts and more discharge pressure ripples. Especially, the discharge pressure ripples bring about vibrations and noises in hydraulic system components such as connecting pipes and control valves, so that these deteriorate the stability and accuracy of the systems. Therefore, the hydraulic systems having the bent-axis piston pump require the methods to reduce the discharge pressure ripples. So, the purpose of this paper is to reduce the discharge pressure ripples by the phase interference of pressure wave and to develope the analysis model of the pumps to predict the discharge pressure ripples. In this paper, the analysis model of the bent-axis piston pump was developed using the AMESim software, and the reliability of that was verified by the comparison with the experimental results. The hydraulic pipeline with a parallel line was used as the method to generate the phase interference of pressure wave. the dynamics characteristics of the hydraulic pipeline with a parallel line were analyzed by a transfer matrix method. the usefulness of the phase interference of pressure wave was investigated through the experiment and simulation. The results from the experiment and simulation said that the phase interference of pressure wave by the hydraulic pipeline with a parallel line could reduce the discharge pressure wave of the pump well. The analysis model of the bent-axis piston pump developed in this paper and the method of the phase interference by the hydraulic pipeline with a parallel line are expected to be helpful to achieve the design of the pump and to reduce the discharge pressure wave of the pump effectively.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1674-1680
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• 2011

As the speed of train increases, the effects of the pressure wave generated by the train are becoming more important. To calculate characteristics of the pressure wave generated by a high-speed train passing through a tunnel, several methods are simulated. The pressure waves give rise to large pressure transients which impose the fluctuating loads on the train. It is highly that the pressure transients should be predicted to design the tunnel size and to improve the comfortableness of passengers. In this study, the pressure transients were numerically simulated for a wide range of train speed and compared with the previous verified paper. The simulation results were agreed with the paper, and the characteristics of pressure wave made clear.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2005년도 춘계학술대회 논문집
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• pp.149-153
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• 2005

In the cardiovascular system, the waveform of the pulsatory blood pressure appears variously due to the cardiac impulse and compliance of blood vessels and arm tissue. We have constructed a blood pressure simulator to investigate effects of mechanical properties of artery walls and tissue on blood pressure measurements. The blood pressure simulator is designed to reproduce wave forms of blood pressure in human arteries. To minimize tracking error, we use a linear control valve, and adapt a hybrid control scheme which consists of a feedback controller and a feedforward controller. Any form of the pressure wave can be reproduced, changing function of the wave form in the computer connected to the simulator for control. From experiments, it has been shown that the simulator reproduces wave forms very well, and that the hybrid scheme adapted is superior to the feedback controller.

• 한국해안·해양공학회논문집
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• 제25권6호
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• pp.422-432
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• 2013

해수면과 해저파압을 연계하는 모수 모형을 개발하기 위한 시스템 식별법을 제시하였다. 비선형 고정변수를 포함한 선형 시불변 모형 구조를 가정하고 추가적인 입력자료를 갖는 자기회귀모형 (ARX)을 이용하여 해저파압 시계열자료로부터 해수면 시계열자료를 또는 해수면 시계열자료로부터 해저파압 시계열자료를 추출하는 방법을 제시하였다. 임의로 선정된 해수면과 해저 파압 자료를 이용하여 모형을 검증하였으며, 유사한 해저수심의 파압자료와 다른 해상 기상조건으로 생성된 해수면 스펙트럼 자료를 통해 재검증하였다. 시스템 식별법을 이용한 방법이 전통적인 선형파 이론을 이용한 선형전송함수(LTF) 방법보다 전반적으로 더 정확하게 수행됨을 확인하였다. 또한 본 논문에서 제시된 방법으로 추정된 해저 파압 시계열모의는 수정 선형전송함수(corrected LTF)에 의한 결과와 유사함을 확인하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.579-584
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• 2009

Arrangement of the facilities for improving harbor functions depends on sea and land conditions such as the ship's arrival and departure conditions, waves and tide. And the plan and the size of the facilities depend much on harbor and marine environment condition such as cargo quantity, ship size, ship traffic and seawater circulation. Among these, waves have so much effect on a breakwater design that it is the most important to understand their characteristics and to apply them to breakwater design. Therefore, to analyze the effect of waves characteristics over a rubble mound breakwater, we have calculated wave pressure by using numerical analysis at each tide level and have analyzed the effect of wave pressure on structure stability by conducting the stability analysis with the wave pressure. As a result, it is found that during low and mean tide level time the biggest wave pressure is estimated near calm water level. But during high tide time, the biggest wave pressure is estimated in front of capping. And the stability analysis indicates also that a structure is most unstable when low tide time wave pressure is acting on. After reviewing the stability of a structure by applying vertical and horizon wave forces, it is concluded that safety factor is lower than ordinary time(max. about 15%), is also reviewed when designing a rubble mound breakwater.

• 한국해안·해양공학회논문집
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• 제33권6호
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• pp.321-332
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• 2021

경사식방파제 상치콘크리트에는 경제적인 이유와 월파의 효과적인 저감을 위해 파라펫이 설치되기도 하지만, 파라펫 설치로 인해 상치콘크리트에는 증가된 파압이 작용하게 된다. 일반적으로 상치콘크리트에 작용하는 파압은 수리실험을 통해 검토되며, 상치콘크리트 설계를 위해서는 파압이 산정되어야 하지만 여전히 불명확한 부분이 있다. 본 연구에서는 상치콘크리트에 작용하는 수평파압 산정을 위해 경사식구조물 형상과 다양한 파랑조건을 적용한 수리실험을 수행하였다. 실험결과를 이용하여 Goda(1974, 2010)의 파압산정식에 적용되는 파압저감계수를 제안하였으며, 테트라포드가 피복된 경사식방파제 상치콘크리트 설계에 실무적으로 적용 가능 할 것으로 기대된다.

• 한국해양공학회지
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• 제28권4호
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• pp.331-337
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• 2014

We analyzed the 3-D characteristics of the dynamic response of seabed around a submerged breakwater due to wave loading using a 3-D numerical scheme (LES-WASS-3D). Using our model, which considers the wave-structure-sandy seabed interactions in a 3-D wave field, we were able to investigate the 3-D characteristics of the pore-water pressure in the seabed around the submerged breakwater under various incident wave conditions. To verify the 3-D numerical analysis method suggested in this study, we compared the numerical results with the existing experimental results and found good agreement between them. The numerical analysis reveals that high pore-water pressure in the seabed is generated below a large wave height at the front slope of the submerged breakwater. It was also shown that the non-dimensional pore-water pressure in the seabed increases as the wave period increases because the wave energy dissipation decreases on the submerged breakwater and seabed as the wave period increases.

• 대한토목학회논문집
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• 제33권6호
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• pp.2317-2328
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• 2013

이 연구에서는 수리모형실험을 통해 유수실 상부 덮개가 유공 케이슨 방파제 전면벽 및 후면벽에서의 파압에 미치는 영향을 고찰하였다. 수리모형실험은 유공 케이슨의 유수실 상부 덮개가 있는 경우 및 없는 경우에 대해서 전면벽 유공률을 변화시키면서 이루어졌다. 유수실 상부가 덮개로 막혀 있을 때에는 모든 실험 조건에서 유의미하게 더 큰 파압이 취득되었으며 따라서 유수실 상부 덮개 존재에 따른 두 벽에서의 계측 파압 차이는 매우 뚜렷하게 나타났다. 그 결과 계측 파압을 적분하여 계산된 전파력의 크기 역시 상부 덮개가 있는 케이슨 방파제의 경우가 더 컸으며, 이 경우 잘 알려진 Takahashi의 파압식에 근거한 파력값을 상회하였다. 한편, 전면벽 유공률에 따라서는 방파제 전면벽 및 후면벽에서 모두 유공률이 클수록 더 큰 파압이 계측되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.373-379
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• 2001

When a train runs into a tunnel at high-speed, aerodynamic drag suddenly increases and the booming noise is generated at the exit of tunnel. The noise shape is very important to reduce the aerodynamic drag in tunnel as well as on open ground, and the micro-pressure wave that is a source of booming noise is dependent on nose shape, especially on area distribution. In this study, the nose shape has been optimized employing the response surface methodology and the axi-symmetric compressible Navier-Stokes equations. The optimal designs have been executed imposing various conditions of the aerodynamic drag and the micro-pressure wave on object functions. The results show that the multi-objective design was successful to decrease micro-pressure wave and aerodynamic drag of trains.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1023-1028
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• 2004

A micro-pressure wave is generated by the high-speed train which enters a tunnel, and it causes explosive noise and vibration at the exit. It is known that train speed, train-tunnel area ratio, nose slenderness and nose shape mainly influence on generating micro-pressure wave. So it is required to minimize it by searching optimal values of such train shape factors and tunnel condition. In this study, response surface model, one of approximation models, is used to perform optimization effectively and analyze sensitivity of design variables. Owen's randomized orthogonal array and D-optimal Design are used to construct response surface model. In order to increase accuracy of model, stepwise regression is selected. Finally SQP(Sequential Quadratic Programming) optimization algorithm is used to minimize the maximum micro-pressure wave by using built approximation model.