• Title/Summary/Keyword: Low order panel method

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Theoretical investigation about the hydrodynamic performance of propeller in oblique flow

  • Hou, Lixun;Hu, Ankang
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.11 no.1
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    • pp.119-130
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    • 2019
  • This paper establishes an iterative calculation model for the hydrodynamic performance of propeller in oblique flow based on low order potential based surface panel method. The hydrodynamic performance of propeller is calculated through panel method which is also used to calculate the induced velocity. The slipstream of propeller is adjusted according to the inflow velocity and the induced velocity. The oblique flow is defined by the axial inflow velocity and the incident angle. The calculation results of an instance show that the thrust and torque of propeller decrease with the increase of axial inflow velocity but increase with the incident angle. The unsteadiness of loads on the propeller blade surface gets more intensified with the increases of axial inflow velocity and incident angle. However, comparing with the effect of axial inflow velocity on the unsteadiness of the hydrodynamic performance of propeller, the effect of the incident angle is more remarkable.

High Performance AC-PDP Sustain Driver with Low switching Loss (낮은 스위칭 손실을 가지는 고성능 AC-PDP 구동 회로에 관한 연구)

  • Kang, Feel-Soon;Park, Sung-Jun;Park, Han-Woong;Kim, Cheul-U
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.05a
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    • pp.50-56
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    • 2002
  • When the plasma panel is used as a display, frequent discharging are made to occur by alternatively charging each side of the panel to a critical voltage, which causes repeated gas discharges to occur. In this paper, an efficient sustain driver is proposed to achieve a faster rise-time in order to be suitable to widely used ADS driving method. The proposed circuit increases an operational margin up to 20 % compared with conventional approaches improving the recovery efficiency regardless of the variation of panel capacitance. Thanks to the increased operational margin, the brightness decrease problem can be solved without a limitation to sustain pulse width. The principle of operation, and features are illustrated, and verified on a 7.5 inch diagonal panel at 200 kHz operating frequency - based on experimental prototype.

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A Study on the Improvement of Multi-Layer Coating Method on Concrete Base (성형 콘크리트 복층마감도장 공법 개선에 관한 연구)

  • Kim, Chong-Weon;Choi, In-Sung
    • Journal of the Korea Institute of Building Construction
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    • v.3 no.1
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    • pp.93-105
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    • 2003
  • The Precast Concrete(PC) method was developed for a large production of a structure in Europe. Afterwards, this PC method has been applied to a structure and an outside Coating of buildings extensively. The outside Coating of the building applied this PC method is a method to put tiles or stones to base concrete. And there is a method to use paints for, so the expression of various patterns is possible. The Multi-Layer Coating is one of the methods to use paints. This Multi-Layer Coating method can show various designs of external appearance with Foam when it is made with the PC panel. Also, the paint film of the PC panel enables a splendid appearance, and a protective function of concrete is possible, too. Therefore, it makes good durability of the PC. Besides, maintenance is easy to manage because it is free from pollution when it uses metallic materials, stones, or any other materials. You might have no trouble in applying the Multi-Layer Coating method in order to save a merit of an outside Coating on the PC panel. However, the Multi-Layer Coating method used as a current outside Coating method has pollution and bad working environment because Oil Epoxy Resins have toxicity and flammability. Therefore, a lot of warnings are required for coating work in order to have appropriate quality because working hours are short, and production efficiency is low too. These reasons make the cost of construction of the Multi-Layer Coating method increase. And employers or designers may have problems in selecting this Multi-Layer Coating method. Therefore, the purpose of this study is to get activation of the Multi-Layer Coating method by offering improvement measures about the problems of the existing Multi-Layer Coating method.

Potential How Analysis for a Hull with the Transom Stern (트랜섬 선미를 가지는 선형의 포텐셜 유동해석)

  • 최희종;전호환
    • Journal of Ocean Engineering and Technology
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    • v.15 no.1
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    • pp.1-6
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    • 2001
  • This study focuses on the potential flow analysis for a hull with the transom stern. The method is based on a low order panel method. The Kelvin type free-surface boundary condition which is known to better fit experimental data for a high speed is applied. To treat a dry transom stern effect a special treatment for the free-surface boundary condition is adopted at the free-surface region after the transom stern. Trim and sinkage, which are important in high speed ships, are considered by an iterative method. Pressure and momentum approaches are used to calculate the wave resistance. Numerical calculations are performed for Athena hull and these results are compared with the experimental data and also other computational results.

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Geometrically nonlinear analysis of sandwich beams under low velocity impact: analytical and experimental investigation

  • Salami, Sattar Jedari;Dariushi, Soheil
    • Steel and Composite Structures
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    • v.27 no.3
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    • pp.273-283
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    • 2018
  • Nonlinear low velocity impact response of sandwich beam with laminated composite face sheets and soft core is studied based on Extended High Order Sandwich Panel Theory (EHSAPT). The face sheets follow the Third order shear deformation beam theory (TSDT) that has hitherto not reported in conventional EHSAPT. Besides, the two dimensional elasticity is used for the core. The nonlinear Von Karman type relations for strains of face sheets and the core are adopted. Contact force between the impactor and the beam is obtained using the modified Hertz law. The field equations are derived via the Ritz based applied to the total energy of the system. The solution is obtained in the time domain by implementing the well-known Runge-Kutta method. The effects of boundary conditions, core-to-face sheet thickness ratio, initial velocity of the impactor, the impactor mass and position of the impactor are studied in detail. It is found that each of these parameters have significant effect on the impact characteristics which should be considered. Finally, some low velocity impact tests have been carried out by Drop Hammer Testing Machine. The contact force histories predicted by EHSAPT are in good agreement with that obtained by experimental results.

Steady/Unsteady Analysis of Ducted Propellers by Using a Surface Panel Method (정상 및 비정상 유동중 덕트 프로펠러의 성능해석)

  • Kim, Kwang;Pyo, Sang-Woo;Suh, Jung-Chun
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.1
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    • pp.30-36
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    • 1999
  • A surface panel method for the analysis of ducted propellers in both uniform and non-uniform onset inflow is developed. A low order, perturbation potential based panel method with an efficient numerical Kutta condition is used. The boundary surface is discretized with hyperboloidal panels and the boundary condition is applied at the panel centroids. The unsteady analysis is based on a time-step algorithm in time domain. Numerical implementation is employed into both steady and unsteady problems. The results with the resent method are shown to have good convergence on the circumferential distribution of circulation on the duct. The effect of the propeller tip clearance on the circumferential circulation on the duct is also presented Numerical results on forces and moments of the propeller and the duct are compared with other numerical results and experimental data.

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Analysis of Manoeuvrability of a Ship in Waves by 3-Dimensional Panel Method (3차원 파넬방법에 의한 파중 선박의 조종성능 해석)

  • S.P. Ann;K.P. Rhee
    • Journal of the Society of Naval Architects of Korea
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    • v.31 no.4
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    • pp.82-98
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    • 1994
  • A mathematical model for the hydrodynamic forces acting on the ship manoeuvring in waves is formulated and a numerical method for the problem is developed. The motion of a ship, which manoeuvres in waves, may be thought to have two components; one is a high frequency component due to encounter waves, and the other is a low frequency component due to manoeuvring motion. So the method of two time scale expansion is used to divide linear boundary value problem. For the effects of waves on the manoeuvring motion of a ship, only the second order drift forces are considered. The integral equation for the velocity potential is solved by 3 dimensional panel method and hydrodynamic forces are calculated by direct integral method.

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New Sustain Electrode Structure for High Luminous Efficiency in AC PDP (AC PDP의 새로운 고효율 전극구조)

  • 박차수;최준영;최윤창;허정은;이영권;박정후
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.53 no.9
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    • pp.475-480
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    • 2004
  • One of the most important issues in AC PDP is the improvement of luminous efficiency. One possible method is to develop new sustain electrode shape showing high luminous efficiency. In this study, a new electrode shapehas a bridge is proposed in order to solve this problem. The experimental results show that the test panel with the suggested new electrode shape shows high luminance efficiency by 35.35% and low sustain voltage by 17V compared with the conventional structure.

Analysis on the Flow Field Around a Hydrofoil with Surface Blowing (표면 유체분출 수중날개의 유동해석)

  • Sang-Woo Pyo;Jung-Chun Suh;Hyo-Chul Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.4
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    • pp.21-27
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    • 1999
  • A low order panel method based on the perturbation potential is applied for prediction of performance of blown-flap rudders. In order to improve the solution behavior at the large angle of attacks, the geometry of the trailing wake sheet is computed by aligning freely with the local flow. The effect of the wake sheet roll-up is also included with use of a high order panel method. The flow in the gap between the main component and the flap of the rudder is modeled as Couette flow. The effects of the gap and the flow jet are included in application of a kinematic and a dynamic boundary condition on the inlet and the outlet of the gap as well as on the flap and the wake. The results with the present method are compared with existing experimental data. The method is shown to be capable of determining accurately the flow characteristics even for large flap angles.

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Calculation of the Wave Resistance of SWATH Ships using Rankine Source Panel Methods (Rankine 소오스 패널법을 이용한 소수선면 쌍동선의 조파저항계산)

  • Chun, H.H.;Lee, M.H.;Joo, Y.R.;Jang, H.S.
    • Journal of the Society of Naval Architects of Korea
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    • v.34 no.2
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    • pp.27-38
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    • 1997
  • This paper is concerned with the calculation of the wave resistance for SWATH ships based on a low order Rankine source panel method. Two types of free surface boundary conditions, Dawson type (double model approximation) and Kelvin type (free stream approximation) are used. For the free surface boundary calculation, an analytic differentiation is employed instead of implementing a finite difference scheme. Then, the radiation condition is satisfied by, so called, the panel shift method. The numerical results using the above two methods are compared with those using the thin ship/modified slender body approximation and also with the experimental results. The SWATH models considered are a single strut SWATH and a twin strut SWATH together with the variations of two demihull separation distance. In order to prove the validity of the program developed, the numerical calculations for a Wigley mono hull and Wigley twin hulls are compared with the available experimental results.

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