• Title/Summary/Keyword: Stem angle

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Numerical and Experimental Investigations of the Effects of Stem Angle on the Resistance of an Icebreaking Cargo Vessel in Pack Ice Conditions

  • Shin, Yong Jin;Kim, Moon Chan;Kim, Beom Jun
    • Journal of Advanced Research in Ocean Engineering
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    • v.2 no.2
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    • pp.67-80
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    • 2016
  • The resistance performance of an icebreaking cargo vessel with varied stem angles is investigated numerically and experimentally. Ship-ice interaction loads are numerically calculated based on the fluid structure interaction (FSI) method using the commercial FE package LS-DYNA. Test results obtained from model testing with synthetic ice at the Pusan National University towing tank and with refrigerated ice at the National Research Council's (NRC) ice tank are used to validate and benchmark the numerical simulations. The designed icebreaking cargo vessel with three stem angles ($20^{\circ}$, $25^{\circ}$, and $30^{\circ}$) is used as the target ship for three concentrations (90%, 80%, and 60%) of pack ice conditions. The comparisons between numerical and experimental results are shown and our main conclusions are given.

Study on Resistance Performance of Icebreaking Cargo Vessel in Pack Ice Condition according to Variation of Synthetic Ice Thickness and Hull Form Characteristics (합성얼음의 두께변화와 선형변화에 따른 Pack ice 상태에서의 쇄빙상선의 저항특성 연구)

  • Lee, Seung-Ho;Kim, Moon-Chan;Chun, Ho-Hwan;Cho, Jun-Cheol;Shin, Byung-Chul;Jung, Un-Hwa
    • Journal of the Society of Naval Architects of Korea
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    • v.46 no.5
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    • pp.471-478
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    • 2009
  • The present paper deals with characteristics of resistance performance according to the variation of synthetic ice thickness and hull form. The resistance test has been conducted with pack ice condition in Pusan National University towing tank. Stem angle has been chosen as main parameters for the variation of hull form characteristics, which is the most important factor especially in icebreaking cargo vessel. The serial comparisons of resistance test have been done with the variation of hull form parameter as well as with the different thickness of synthetic ice. The different trend of resistance performances with increasing of stem angle has been shown at each synthetic ice thickness. The present test results is expected to be confirmed by comparing the test results in ice tank in the near future.

Development of the ice resistance series chart for icebreaking ships

  • Lee, Chun-Ju;Joung, Tae-Hwan;Lew, Jae-Moon
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.6
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    • pp.794-802
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    • 2018
  • The ice resistance series charts for icebreaking ships were developed through a series of systematic model tests in the ice tank of the Korean Research Institute of Ship and Ocean Engineering (KRISO). Spencer's (1992) component-based scaling system for ship-ice model tests was applied to extend the model ship correlations. Beam to draft ratio (B/T), length to beam ratio (L/B), block coefficient ($C_B$) and stem angle (${\alpha}$) were selected as geometric parameters for hull form development. The basic hull form (S1) of twin pod type with B/T of 3.0, L/B of 6.0, $C_B$ of 0.75 and stem angle of $25^{\circ}$ was generated with a modern hull design concept. A total of 13 hulls were designed varying the geometric parameters; B/T of 2.5 and 3.5, L/B of 5.0 and 7.0, $C_B$ from 0.65 to 0.85 in intervals of 0.05, and 5 stem angles from $15^{\circ}$ to $35^{\circ}$. Ice resistance tests were first carried out with the basic hull form in level ice with suitable speed. Four more tests for $C_B$ variations from 0.65 to 0.85 were conducted and two more for beam to draft and length to beam ratios were also performed to study the effect of the geometric parameters on ice resistance. Ice resistance tests were summarized using the volumetric coefficient, $C_V$ ($={\nabla}/L^3$), instead of L/B and $C_B$ variations. Additional model tests were also carried out to account for the effect of the stem angle, ice thickness and ice strength on ice resistance. In order to develop the ice resistance series charts with a minimum number of experiments, the trends of the ice resistance obtained from the experiments were assumed to be similar for other model ship with different geometric parameters. A total of 18 sheets composed of combinations of three different beam to draft ratios and six block coefficients were developed as a parameter of $C_V$ in the low speed regions. Three correction charts were also developed for stem angles, ice thickness and ice strength respectively. The charts were applied to estimate ice resistance for existing icebreaking ships including ARAON, and the results were satisfactory with reasonable accuracy.

Comparative Study on Resistance Performance of Icebreaking Cargo Vessel according to Hull Form Variation by using Synthetic Ice and Refrigerated Ice (합성얼음과 냉동얼음을 이용한 선형을 변화시킨 쇄빙상선의 저항특성 연구)

  • Lee, Seung-Ho;Kim, Moon-Chan;Chun, Ho-Hwan;Shin, Byung-Chul
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.3
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    • pp.350-358
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    • 2010
  • The present paper deals with the comparative study of resistance performance with refrigerated ice and synthetic ice according to the variation of hull form characteristics. The resistance test has been conducted in pack ice condition in each concentration condition. Stem angle has been chosen as main parameters for the variation of hull form characteristics. The correlation of performance between with the refrigerated ice and with the synthetic ice has been shown according to the variation for stem angles. The present study show the possibility of ice test in general towing tank with synthetic ice for the time-consuming research such as hull form optimization although that is confined in pack ice condition. The more parametric study for the properties of synthetic ice is expected to be conducted to have more close correspondence for the test results of refrigerated ice in near future.

A Study on Bow Hull Form and Icebreaking Capability of Icebreaking Vessels (빙해항행선박의 선수부 형상과 쇄빙능력에 관한 연구)

  • K. Choi;C.B. Son;E.G. Paeng
    • Journal of the Society of Naval Architects of Korea
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    • v.29 no.4
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    • pp.87-97
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    • 1992
  • Of various design factors affecting icebreaking capability of an icebreaker, the stem angle(i.e., angle between bow stem and ice sheet) is the most important one under continuous icebreaking operation. This study focuses on the relationship between the bow stem angle of an icebreaker and its icebreaking capability. Considering relatively high loading-rate conditions with typical advancing speed of 3 to 4 knots, the material properties and deformation characteristics of sea ice are regarded as entirely elastic and brittle. In this paper the interaction process of icebreaker with level ice is simplified as a beam of finite length supported by Winkler-type elastic foundation simulating water buoyancy. The wedge type ice beam is loaded by the vertical impact forces due to the inclined bow stem of icebreaking vessels. The numerical model provides locations of maximum bending moment where extreme tensile stress arises and also possible fracture occurs. The model can predict a characteristic length of broken ice sheet upon the given environmental and design parameters.

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Prediction of Design Ice Load on Icebreaking Vessels under Normal Operating Conditions (정상운항 상태에서 쇄빙선박에 작용하는 설계 빙하중 추정)

  • Choi, Kyung-Sik;Jeong, Seong-Yeob;Nam, Jong-Ho
    • Journal of the Society of Naval Architects of Korea
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    • v.46 no.6
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    • pp.603-610
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    • 2009
  • Ice load is one of the important design parameters for the construction of icebreaking vessels. In this paper, the design ice load prediction for the icebreaking vessels under normal operating condition in ice-covered sea is discussed. The ice loads under normal operating condition are expected from sea trials in moderate ice conditions. In this sense the extreme ice loads during heavy ramming or accidental collision are not considered. Current study describes the global ice load on the hull of the icebreaking vessels. Available ice load data from full-scale sea trials are collected and analyzed according to various ship-ice interaction parameters including displacement, stem angle, speed of a ship and flexural strength and thickness of sea ice. The ice load prediction formula is compared with the collected full-scale sea trials data and it shows a good agreement.

Effect of Light Transmittance Control on the Growth Status of Aerial Parts during the Growing Season of Panax ginseng (생육시기별 광량조절이 인삼의 지상부 생육에 미치는 영향)

  • Cheon, Seong-Ki;Lee, Tae-Su;Yoon, Jong-Hyuk;Lee, Sung-Sik
    • Journal of Ginseng Research
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    • v.27 no.4
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    • pp.202-206
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    • 2003
  • This study was conducted to compare the growth status of aerial parts, photosynthesis and microclimate between fixing light transmittance (Control) and changing light transmittance (C.L.T.) during ginseng growing seasons. Control showed 8% light transmittance rate during growing seasons. But C.L.T. showed 18% light transmittance rate during early (April-June) and late growth stage (September-October) and 6% light transmittance rate middle growth stage(July-August). Air temperature, leaking water rate and soil water content of C.L.T. was higher than those of control during early and late growth stage. But Air temperature, leaking water rate and soil water content of C.L.T was lower than those of control during middle growth stage C.L.T. exhibited superiority in survival ratio, stem diameter, stem length, L.A.I. and stem angle compared to control. Chlorophyll content of C.L.T. was lower than that of control but S.L.W., stomatal opening and photosynthetic rates of C.L.T. was higher than those of control. Also Alternaria blight disease and defoliation of C.L.T. was lower than those of control.

Vessel Collision Analysis of an Underwater Soil Slope using Coupled Eulerian-Lagrangian Scheme 2: Parametric Study (Coupled Eulerian-Lagrangian 기법을 이용한 선박의 수중사면 충돌해석 2 : 매개변수연구)

  • Lee, Gyehee
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.33 no.1
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    • pp.25-33
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    • 2020
  • In this study, parametric analyses are performed using the coupled Eulerian-Lagrangian scheme for the collision behaviors of a vessel and an underwater slope that constitutes part of an artificial protective island. The vessel parameters considered in the analysis are bow angle, stem angle, draft, and impact velocity. The gradient of the slope, the friction coefficient between the bow and the slope, and soil strength are considered as parameters of the slope. For each parameter, the dissipated collision energy and the collision force are estimated from the behavior of the vessel, and the energy dissipation mechanism is identified in terms of the ground deformation. The collision force is assumed as an exponential function, and the effects of the parameters are estimated. As a result, only two parameters, the gradient of the slope and the friction coefficient between the vessel and the soil, can affect the exponential coefficient of the function. The dissipated energy by the soil can thus be estimated adequately. The relationship between the volume of the soil pushed out by the bow and the dissipated collision energy is estimated as a linear function. This relationship is independent of the magnitude of the collision energy, and affected more by the friction coefficient and the soil strength than by the parameters of the vessel.

Effect of Ortet Age and Types of Cuttings on Rooting, Cyclophysis and Topophysis of Rooted Cuttings in Taxus cuspidata S. et Z (주목삽수(揷穗)의 모수령(母樹齡) 및 아조형태(芽條形態)가 발근(發根)과 묘형(苗型)에 미치는 영향(影響))

  • Goo, Gwan Hyo;Lee, Kang Young;Youn, Ki Sik;Kwon, Yeong Han
    • Journal of Korean Society of Forest Science
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    • v.79 no.4
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    • pp.359-366
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    • 1990
  • This study was carried out to investigate rooting rate, plagiotrophic growth and root-promoting effect of IBA in Taxus cuspidata S, et Z. cuttings. The results obtained were summarized as follows ; 1. As the ortet ages of cuttings were increased in 5, 10, to 20 years, the rooting rates were decreased in order of 85.7%, 81.7% and 62.4%, and the number of primary roots were also decreased in 5.3, 3.7 and 2.9, respectively. 2. Rooting rate by cutting types of lateral shoot were higher than those of main shoot type, significant at the 1% level. 3. IBA(l00ppm) treatment promoted the rooting rates and the number of primary roots. 4. As the ortet ages were increased in 5, 10 to 20 years, angles of central shoot of rooted cuttings which mesured cyclophysis were decreased in order of $75.9^{\circ}$, $68.5^{\circ}$ and $59.6^{\circ}$, respectively, significant at the 1% level. 5. Average angles showed $77.0^{\circ}$ for main shoot cutting, $65.9^{\circ}$ for upper lateral shoot and $61.7^{\circ}$ for lower lateral, which was significant at 1% level, and lateral shoot cutting showed more topophysis than main shoot cutting. 6. Shoot length of rooted cuttings from main shoot cutting was longer than that from lateral shoot significant at the 1% level. 7. Relationship between some characteristics showed highly positive correlation.

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