• Title/Summary/Keyword: Marching plane

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3D Mesh Model Exterior Salient Part Segmentation Using Prominent Feature Points and Marching Plane

  • Hong, Yiyu;Kim, Jongweon
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.3
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    • pp.1418-1433
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    • 2019
  • In computer graphics, 3D mesh segmentation is a challenging research field. This paper presents a 3D mesh model segmentation algorithm that focuses on removing exterior salient parts from the original 3D mesh model based on prominent feature points and marching plane. To begin with, the proposed approach uses multi-dimensional scaling to extract prominent feature points that reside on the tips of each exterior salient part of a given mesh. Subsequently, a set of planes intersect the 3D mesh; one is the marching plane, which start marching from prominent feature points. Through the marching process, local cross sections between marching plane and 3D mesh are extracted, subsequently, its corresponding area are calculated to represent local volumes of the 3D mesh model. As the boundary region of an exterior salient part generally lies on the location at which the local volume suddenly changes greatly, we can simply cut this location with the marching plane to separate this part from the mesh. We evaluated our algorithm on the Princeton Segmentation Benchmark, and the evaluation results show that our algorithm works well for some categories.

NUMERICAL SIMULATIONS FOR THE CONTRACTION FLOW USING GRID GENERATION

  • Salem, S.A.
    • Journal of applied mathematics & informatics
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    • v.16 no.1_2
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    • pp.383-405
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    • 2004
  • We study the incomprssible Navier Stokes equations for the flow inside contraction geometry. The governing equations are expressed in the vorticity-stream function formulations. A rectangular computational domain is arised by elliptic grid generation technique. The numerical solution is based on a technique of automatic numerical generation of acurvilinear coordinate system by transforming the governing equation into computational plane. The transformed equations are approximated using central differences and solved simultaneously by successive over relaxation iteration. The time dependent of the vorticity equation solved by using explicit marching procedure. We will apply the technique on several irregular-shapes.

A Numerical Study on the Heat Transfer Characteristics in an Internally Finned Circular Tube Flow (내부핀이 부착된 원형관유동에서의 열전달특성에 관한 수치적연구)

  • Pak, H.Y.;Park, K.W.;Choi, M.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.8 no.2
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    • pp.267-278
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    • 1996
  • Steady, laminar, forced convection flow and heat transfer in the entrance region of an internally finned circular duct with a finite thermal conductivity has been analyzed numerically. The problem under investigation is a three-dimensional boundary layer problem, and is solved by employing a marching-type procedure which involves solution of a series of 2-dimensional elliptic problems in the cross-stream plane. Two types of inlet hydrodynamic conditions are considered : (a) uniform velocity flow and (b) fully developed flow. From the above inlet conditions, the effects of the fin height(h), fin number(N) and conductivity ratio($k_r$) on the flow and thermal characteristics are investigated. The numerical results show that the height and number of fins, and ratio of the solid to fluid thermal conductivity have pronounced effect on the solution. Considering pressure drop, optimized dimensionless fin height is 0.4.

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Non-Cavitation Noise from Large Scale Marine Propeller (대형 선박용 프로펠러의 비공동소음 예측)

  • Ryu, Ki-Wahn;Kim, Bong-Ki;Yoo, Yong-Joo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.10a
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    • pp.562-567
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    • 2012
  • Noises from the large scale marine propeller are calculated numerically on non-cavitation condition. The hydrodynamic analysis are carried out by potential based panel method with time marching free wake approach. The distribution of hyrodynamic loads on the propeller surface and noise signals are obtained using the unsteady Bernoulli's equation and the Farasssat formula respectively. It turns out that the noise signal shows strong peak at the blade passage frequency. Noise signals and directivity patterns for both the thickness and the loading noise are compared with each other. The directivity pattern for the loading noise shows minor lobe at the backward side of the rotating disc plane.

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Numerical study of a turbulent plane jet under the pressure gradient in the transverse direction (진행축에 수직방향 압력구배를 받는 난류 평면제트의 수치적 연구)

  • 최문창;최도형
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.5
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    • pp.1150-1157
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    • 1988
  • Two-dimensional turbulent plane jet which is under the pressure gradient in the transverse direction is studied numerically. Full Navier-Stokes equations are used to correctly account for the pressure variation in the transverse direction. Using the standard k-.epsilon. turbulence model as a closure relationship, a time marching procedure gives the velocity field. The temperature fields are obtained for two different cases : (1) Hot jet is issued into the cold still air, and (2) Hot jet is issued into the surrounding across which exists a temperature difference. The velocity and temperature fields along with other flow and heat-transfer characteristics for two different pressure gradients are presented. A simple formula that relates the jet trajectory to the pressure gradient is also proposed. The mass flux in the longitudinal direction and the jet halfwidth seem insensitive to the pressure gradient. However, the pressure gradient increases the heat flux in the longitudinal direction as well as in the transverse direction.

Prediction of Non-cavitation Noise from Large Scale Marine Propeller (수치해석을 통한 대형 선박용 프로펠러의 비공동소음 예측)

  • Ryu, Ki-Wahn;Lee, Jong-Yeol;Kim, Bong-Ki;Byun, Jeong-Woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.25 no.2
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    • pp.75-82
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    • 2015
  • Noises from the large scale marine propeller are calculated numerically on non-cavitation condition. The hydrodynamic analysis is carried out by potential based panel method with time marching free wake approach. The distribution of hydrodynamic loads on the propeller surface and noise signals are obtained using the unsteady Bernoulli's equation and the Farasssat's formula respectively. It turns out that the noise signal at the narrow band shows strong peak at the blade passage frequency, and the peak value at the 1/3 octave band also shows the same trend. Noise signals and directivity patterns for both the thickness and the loading noise are compared with each other. The directivity pattern for the loading noise shows minor lobe at the backward side of the rotating disc plane.

A Linear Wave Equation Over Mild-Sloped Bed from Double Integration (이중적분을 이용한 완경사면에서의 선형파 방정식)

  • Kim, Hyo-Seob;Jung, Byung-Soon;Lee, Ye-Won
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.12 no.3
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    • pp.165-172
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    • 2009
  • A set of equations for description of transformation of harmonic waves is proposed here. Velocity potential function and separation of variables are introduced for the derivation. The continuity equation is in a vertical plane is integrated through the water so that a horizontal one-dimensional wave equation is produced. The new equation composed of the complex velocity potential function, further be modified into. A set up of equations composed of the wave amplitude and wave phase gradient. The horizontally one-dimensional equations on the wave amplitude and wave phase gradient are the first and second-order ordinary differential equations. They are solved in a one-way marching manner starting from a side where boundary values are supplied, i.e. the wave amplitude, the wave amplitude gradient, and the wave phase gradient. Simple spatially-centered finite difference schemes are adopted for the present set of equations. The equations set is applied to three test cases, Booij's inclined plane slope profile, Massel's smooth bed profile, and Bragg's wavy bed profile. The present equations set is satisfactorily verified against existing theories including Massel's modified mild-slope equation, Berkhoff's mild-slope equation, and the full linear equation.

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Inhomogeneous Helmholtz equation for Water Waves on Variable Depth (비균질 Helmholtz 방정식을 이용한 변동 수심에서의 파랑변형)

  • Kim, Hyo-Seob;Jang, Chang-Hwan
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.13 no.3
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    • pp.174-180
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    • 2010
  • The inhomogeneous Helmholtz equation is introduced for variable water depth and potential function and separation of variables are introduced for the derivation. Only harmonic wave motions are considered. The governing equation composed of the potential function for irrotational flow is directly applied to the still water level, and the inhomogeneous Helmholtz equation for variable water depth is obtained. By introducing the wave amplitude and wave phase gradient the governing equation with complex potential function is transformed into two equations of real variables. The transformed equations are the first and second-order ordinary differential equations, respectively, and can be solved in a forward marching manner when proper boundary values are supplied, i.e. the wave amplitude, the wave amplitude gradient, and the wave phase gradient at a side boundary. Simple spatially-centered finite difference numerical schemes are adopted to solve the present set of equations. The equation set is applied to two test cases, Booij’ inclined plane slope profile, and Bragg’ wavy bed profile. The present equations set is satisfactorily verified against other theories including the full linear equation, Massel's modified mild-slope equation, and Berkhoff's mild-slope equation etc.