• 제목/요약/키워드: Wedge drop

검색결과 11건 처리시간 0.017초

Experimental study on the effects of stern bulb arrangement on the slamming load

  • Park, Jongyeol;Choi, Ju Hyuck;Lee, Hyun-ho;Rhee, Shin Hyung
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제12권1호
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    • pp.518-530
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    • 2020
  • The present study concerns the stern slamming load of container carriers, with stern bulb arrangement variation. First, a series of wedge drop tests were conducted using simple wedge models with fixed deadrise angles, and tests with the cross-section models of practical container carrier sterns were followed. The deadrise angle of the simple wedge ranged from 0° to 10°. The pressure measurement results of the simple wedge drop tests were distributed between empirical formula and analytic solution, so the experimental setup was validated. In the cases of practical hull cross-sections, the water entry of the bulb prior to that of the transom resulted in characteristic water film generation and delayed pressure peak appearance. The trapped air between the bulbs damped the pressure in the twin skeg hull case, reducing the pressure peak and causing the pressure oscillation during water entry.

유체-구조 상호 간섭을 고려한 쐐기 슬래밍에 대한 실험적 연구 (Experimental Study on Wedge Slamming Considering Fluid-Structure Interaction)

  • 안강수;권순홍
    • 한국해양공학회지
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    • 제31권1호
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    • pp.22-27
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    • 2017
  • This paper presents the results of an experimental study on the wedge slamming impact problem, including the fluid-structure interaction. A free drop test was performed to estimate the hydroelasticity. Three wedges were fabricated of 5 mm thick steel plate. The deadrise angles were $15^{\circ}$, $20^{\circ}$, and $25^{\circ}$. Plate thicknesses of 2 mm and 3 mm were used to determine the effect of the structural rigidity. The drop heights were 25 cm, 50 cm, 75 cm, and 100 cm. The pressure on a rigid part of the wedge and strain of the elastic plate were measured at four different locations. The pressure was compared using the Wagner theory and generalized Wagner theory.

대칭 및 비대칭 2차원 쐐기의 입수 충격에 관한 실험적 연구 (Experimental Study of Water Impact Loads on Symmetric and Asymmetric Wedges)

  • 김경환;이동엽;홍사영;김영식;김병완
    • 한국해양공학회지
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    • 제28권3호
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    • pp.209-217
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    • 2014
  • In the present study, the water impact loads on two-dimensional symmetric and asymmetric wedges were mainly studied. The impact pressure and force were measured during a vertical drop of the symmetric and asymmetric wedges. The measured pressure was compared with analytic solutions. The measured force at a local area of the wedge was compared with the integrated pressures and analytic solutions. Some findings on symmetric and asymmetrical wedge drops are presented, and the reliability of the force sensor used for the measurement of the local impact force is discussed.

쐐기형 요철이 설치된 사각덕트에서의 열전달 및 압력강하 특성 (Heat/Mass Transfer and Pressure Drop of Square Duct with V-shape Ribs)

  • 최청;이동호;조형희
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집B
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    • pp.280-287
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    • 2001
  • The present study investigates convective heat/mass transfer and flow characteristics inside the rib-roughened cooling passage of the gas turbine blades. A square duct with rectangular ribs is used and $\wedge-$ and V-shape ribs with $60^{\circ}$ attack angle are installed on the test plate surfaces. Naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wall and the vortices near the side-wall. The local heat transfer and the secondary flow in the duct are changed largely according to the rib orientation. A square duct with $\wedge$ and V-shape ribs has two pairs of secondary flow because of the rib arrangement. So, the duct has complex heat/mass transfer distribution. The average heat/mass transfer coefficient and pressure drop of $\wedge-$ and V-shape ribs are higher than those with $90^{\circ}$ and $60^{\circ}$ attack angles. The average heat/mass transfer coefficient on the $\wedge-shape$ ribs is higher than that on the V-shape ribs. Also, the uniformity of heat/mass transfer coefficient on discrete ribs is higher than that on continuous rib.

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쐐기 슬래밍에 관한 실험적 연구 (Experimental Investigation of Wedge Slamming Impact)

  • 임지;안강수;권순홍
    • 한국해양공학회지
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    • 제29권2호
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    • pp.163-168
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    • 2015
  • This paper presents the results of experimental work on the wedge slamming impact problem. An experiment was done with a wedge model. The deadrise angle of the wedge was $4^{\circ}$. The model was made in two parts: the outside part was made of a 5-mm-thick steel plate that could be assumed to be a rigid body, and the inside part was made of a thin SUS plate that could be assumed to be an elastic body. Thin SUS plate thicknesses of 2 mm and 3 mm were used to determine the effect of plate rigidity. The drop height was varied from 0.25 m to 1 m to determine the effect of a large deformation.

Experimental and Numerical Study on Slamming Impact

  • Kwon, Sun Hong;Yang, Young Jun;Lee, Hee Sung
    • 한국해양공학회지
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    • 제27권1호
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    • pp.1-8
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    • 2013
  • This paper presents the results of experimental and numerical research on the slamming phenomenon. Two experimental techniques were proposed in this study. The traditional free drop tests were carried out. However, the free drop tests done in this study using an LM guide showed excellent repeatability, unlike those of other researchers. The coefficients of variation for the drop test done in this experiment were less than 0.1. The other experimental technique proposed in this study was a novel concept that used a pneumatic cylinder. The pneumatic cylinder could accelerate the specimen over a very short distance from the free surface. As a result, high rates of repeatability were achieved. In the numerical study, the development of in-house code and utilization of commercial code were carried out. The in-house code developed was based on the boundary element method. It is a potential code. This was mostly applied to the computation of the wedge entry problem. The commercial code utilized was FLUENT. Most of the previous slamming research was done under the assumption of a constant body velocity all through the impact process, which is not realistic at all. However, the interaction of a fluid and body were taken into account by employing a user-defined function in this study. The experimental and numerical results were compared. The in-house code based on BEM showed better agreement than that of the FLUENT computation when it cames to the wedge computation. However, the FLUENT proved that it could deal with a very complex geometry while BEM could not. The proposed experimental and numerical procedures were shown to be very promising tools for dealing with slamming problems.

A study on accumulated damage of steel wedges with dead-rise 10° due to slamming loads

  • Seo, Byoungcheon;Truong, Dac Dung;Cho, Sangrai;Kim, Dongju;Park, Sookeun;Shin, Hyunkyoung
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제10권4호
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    • pp.520-528
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    • 2018
  • This paper presents the results of experimental investigation on the elastic-plastic response of steel unstiffened wedges with dead-rise $10^{\circ}$ subjected to repeated impulsive pressure loadings. Repeated drop tests were performed with both wedge thickness and drop height varied. The pressure and histories were recorded during the tests and the permanent deflections were measured after every drop. Using the recorded test result, the effects of flexibility of wedges and repetition have been investigated. From the pressure history obtained from the tests the characteristics of the impulses were identified. Numerical simulations of the tests were made using the measured pressure history and the permanent deflection predictions were compared with those of the experiments.

경사 그루브를 갖는 평판 실의 압력 강하 및 누설 성능 (Pressure Drop and Leakage Performances of Flat Seals with Inclined Grooves)

  • 정진우;정권종;황성호;김태호;김어진
    • Tribology and Lubricants
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    • 제38권5호
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    • pp.213-221
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    • 2022
  • This paper presents performance measurements of pressure drop and leakage flow rate of test flat seals with asymmetric inclined grooves. This study aims to reveal the influence of groove shapes, often machined in radial film riding-face seals, in forming a hydrodynamic wedge on leakage performance. A test facility was developed, and test seals were manufactured to study the effects of the inlet pressure level, ratio of inlet to outlet pressure, seal groove length, and seal groove height on the steady-state pressure drop and leakage performance. A series of tests were conducted, and the test data were compared to the predictions from a simple and efficient mathematical model using a one-dimensional Reynolds equation. The test results revealed that an increase in the inlet pressure increased the pressure drop through the test seals. The leakage flow rate increased significantly as the inlet pressure and ratio of the inlet to outlet pressure increased. The groove shape also affects seal performance. An increase in the groove length and height resulted in an evident increase in the leakage flow rate. The simple model predictions underestimated the leakage flow rates but showed good agreement with the trend in the measurements for all test operating conditions and changes in the groove shape.

좌초시 선저보강판의 손상에 관한 연구(제2보 : 손상추정식) (On the Grounding Damage of Ship Bottom Stiffened Platings(Part II : Damage Prediction Formula))

  • 백점기;이탁기
    • 대한조선학회논문집
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    • 제31권4호
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    • pp.119-129
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    • 1994
  • 본 연구의 목적은 좌초시 선저 보강판 부재를 대상으로 강체 웨지가 종방향으로 보강된 판으로 진입할 때의 흡수에너지-찢김길이 관계를 나타내는 실험식을 도출하는 것이다. 본 연구는 제1보에서 수행한 시리즈 실험 결과 및 찢김응답에 관한 주요 인자들의 중요도 조사 결과를 바탕으로 하고 있다. 준정적 하중상태에서 수행된 실험 결과를 바탕으로 무차원 해석을 수행하여 찢김이 진행되는 동안의 판부재의 흡수에너지를 찢김길이, 항복응력, 등가판두께, 웨지각도의 함수로 정식화하였다. 또한, 이식을 충격하중 작용시에도 적용할 수 있도록 동적 효과를 고려하였다. 특히, 본 연구에서는 동적 마찰 효과를 고려하기 위하여 동적 마찰 감소 계수의 개념을 도입하였다. 본 제안식의 유용성을 확인하기 위하여 기존의 제안식 및 충격 실험에 의해 얻어진 결과와 본 제안식의 결과를 비교하였다.

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직교격자계 기반의 수치계산법을 이용한 슬래밍 충격압력의 연구 (A Study on Slamming Impact Pressure by a Numerical Method based on the Cartesian-grid System)

  • 김기용;이영길;하윤진;강의하;박정호;이선규;이창진
    • 대한조선학회논문집
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    • 제56권4호
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    • pp.308-315
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    • 2019
  • In this study, numerical simulations of slamming impact pressure acting on the flat plate and wedge type models using the cartesian-grid system and Modified Marker-Density Method (MMD method) were performed and the results were examined. The flat plate and wedge type models were selected as target objects, the turbulence characteristics were considered by applying the Sub-Grid Scale (SGS) turbulence model. Through this study, how the pressure acting on the target objects according to the incident angle influences the slamming impact pressure was examined and the results were compared with the flow characteristics of other experimental results. Also, the degree of slamming impact pressure is evaluated with respect to the cartesian-grid system and MMD method, which is easy to use and has a high degree of calculation for free surface.