• Title/Summary/Keyword: similarity solution

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A Study on the model of Thermal Plume Flow in the Forest Fire (산불에 의한 열적상승유동 해석에 관한 연구)

  • Ji, Young-Moo;Park, Jung-Sang
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.358-361
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    • 2008
  • A study is made of thermal plume flow model for the development of helicopter simulator over the forest fire. For numerical analysis, the Boussinesq fluid approximation and line fire model, which is assumed by the shape of forest fire spreading, are adopted. Comparing 3-D full numerical solutions with 2-D similarity solution, it has been built a new model that is capable of temperature prediction along the symmetric vertical axis in both cases of laminar and turbulent flows.

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Analytic Analysis of Liquid-Filled Membrane Container Resting on Horizontal Foundation with Given Cross-Sectional Volume (수평 지반에 놓인 액체 저장용 막구조물 형상의 단면 체적에 따른 해석적 해)

  • Choi, Yoon-Rak
    • Journal of Ocean Engineering and Technology
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    • v.25 no.2
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    • pp.62-66
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    • 2011
  • In this paper, a liquid-filled long membrane container resting on a horizontal foundation is considered. All of the quantities are normalized to obtain similarity solutions. A system of nonlinear ordinary differential equations with undetermined boundary conditions is solved analytically. The integration of the curvature gives the solutions, which are expressed in terms of the elliptic integrals. A method for finding the shape and characteristic values is proposed for a given cross-sectional volume. The validity of these solutions is confirmed, and some results are shown for characteristic values and shapes.

A Study on the Model of Thermal Plume Flow in the Forest Fire (산불에 의한 열적상승유동 해석에 관한 연구)

  • Park, Jun-Sang;Ji, Young-Moo;Jun, Hyang-Sig;Jeon, Dae-Keun
    • The KSFM Journal of Fluid Machinery
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    • v.12 no.1
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    • pp.7-15
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    • 2009
  • A study is made of thermal plume flow model for the development of helicopter simulator over the forest fire. For the numerical analysis, a line fire model with Boussinesq fluid approximation, which is idealized by the spreading shape of forest fire on the ground, is adopted. Comparing full 2-D and 3-D numerical solutions with 2-D similarity solution, it has been built a new model that is useful for temperature prediction along the symmetric vertical axis of fire model for both cases of laminar and turbulent flow.

MODEL FOR THE CONTAMINATION OF CONFINED AQUIFERS BY POLLUTANTS

  • Bestman, A.R.;Odigi, M.I.
    • The Pure and Applied Mathematics
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    • v.6 no.2
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    • pp.113-120
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    • 1999
  • This paper studies the problem of an infinite confined aquifer which at time t < 0 is assumed motionless. At time t = 0 crude oil seeps into the aquifer, thereby contaminating the valuable drinking water. Since the crude oil and water are im-miscible, the problem is posed as a one-dimensional two-phase unsteady moving boundary problem. A similarity solution is developed in which the moving front parameter is obtained by Newton-Ralphson iteration. A numerical scheme, involving the front tracking method, is devised employing the fourth order Runge-Kutta method. Comparison of the exact and numerical schemes shows an error of only 3%. Thus the developed numerical scheme is quite accurate in tackling more realistic problems where exact solutions are not possible.

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A Numerical Study on the Flow Field in an Optical Disc Drive (광디스크 드라이브 내부 유동장 해석)

  • 최명렬;성평용;이경호
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.991-997
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    • 2003
  • A flow field around a disc in an optical disc drive is invested using numerical methods. The high-speed rotating disc induces a strong flow field around the disc, which causes the pressure distribution on the surfaces of the disc. The pressure difference between the upper and the lower surfaces causes the deformation of the disc. In the first part of this study, flow fields around a rotating disc and a stationary wall are investigated using a similarity solution method, in order to identify the effect of the distance between the disc and the wall on the pressure distribution on the surfaces of the disc. In the second part, flow field in a slim-type optical disc drive is studied using a commercial code in order to consider the effect of the vortices generated by the local geometry of the drive.

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The Effect of Pressure on Laminar Film Condensation along a Horizontal Plate (수평평판의 층류 막응축에서 압력의 영향)

  • Lee, Euk-Soo;Lee, Sung-Hong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.12
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    • pp.945-953
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    • 2008
  • Laminar film condensation of saturated vapor in forced flow over a flat plate is analysed. The problem is formulated as exact boundary-layer solution and integral approximate solution. From numerical solutions of the governing equations, it is found that the energy transfer by convection and the effect of inertia term in the momentum equation in negligibly small for low pressure but quite important for high pressure. The condensate rate, liquid-vapor interfacial shear stress and local heat transfer are strongly dependent on the reduced pressure $P_r$ and the modified Jacob number Ja/Pr.

AXISYMMETRIC STAGNATION FLOW NEAR A PLANE WALL COATED WITH A MAGNETIC FLUID OF UNIFORM THICKNESS (균일 두께로 자성유체가 피막된 평면 벽 주의의 축대칭 정체 유동)

  • Ko, Hyung-Jong;Kim, Kyoung-Hoon;Kim, Se-Woong
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.39-44
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    • 2007
  • A similarity solution of the Navier-Stokes equation for the axisymmetric stagnation flow near a plane wall coated with a magnetic fluid of uniform thickness is constructed. The shape functions representing the flow in two (magnetic and normal) fluid layer are determined from a third order boundary value problem, which is solved by the Runge-Kutta method with two shooting parameters. Features of the flow including streamline pattern and interface velocity are investigated for the varying values of density ratio, viscosity ratio, and Reynolds number. The results for the interface and wall shear stress, boundary layer and displacement thickness are also presented.

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An Experimental Study on the Similarity of Confined Coaxial Jets (동축 이중제한분류의 상사성에 대한 실험적 연구)

  • 사용철;이태환;이준식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.5
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    • pp.1291-1299
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    • 1995
  • In confined coaxial jets, the flow-mixing characteristics depend on the initial conditions at the nozzle outlet such as velocity ratio and nozzle radius ratio. In this study, nozzle ratio(inner/outer) was 0.3. Longitudinal axial velocity, turbulent intensity and Reynolds shear stress were measured by CTA. Measurements were made from the duct inlet to the region where similarity solution could exist. This study investigated flow charicteristics according to the variation of similitude parameter which was derived from the theory of Craya-Cutet. The range of similarity region depends on the variation of the similitude patameter. The form factor obtained from the axial velocity profile in the similarity region was constant. The higher the similitude parameter, the wider the spread rate of the jets. Due to this fact, the similarity conditions developed more quickly and the region where the similarity holds became narrow. Present experimental data confirmed the validity of Craya-Curtet theory.

Numerical Simulation of Mixing Control in Parallel Supersonic- Subsonic Jet Using Acoustic Waves (음향파를 이용한 두 평행류의 혼합 증대)

  • Shin, Seong-Ryong;Chang, Se-Myong;Lee, Soogab
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.751-756
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    • 2001
  • An experimental model of the advanced mixing control in the parallel supersonic-subsonic mixing jet (M$_1$=1.78 and M$_2$=0.30) is numerically simulated. An oscillating wall boundary condition is used as the modeling of a wall cavity for mixing enhancement. The obtained pitot pressure distributions along cross sections at the developing region of the turbulent jets are validated from the good agreement with equivalent experimental data. The similarity solution of dimensional analysis also coincides with this numerical result at the self-similar region sufficiently far from the jet exit.

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The Effect of Heat Conduction resistance on Laminar Film Condensation along a Horizontal Plate (수평평판의 막응축에서 전도 열저항의 영향)

  • Lee, Euk-Soo
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2005.06a
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    • pp.183-188
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    • 2005
  • The effect of heat conduction resistance on laminar film condensation of the pure saturated vapor in forced flow over a flat plate has been investigated as boundary layer solutions. A efficient numerical methods for water are proposed for its solution. The momentum and energy balance equations are reduced to a nonlinear system of ordinary differential equations with four parameters: the Prandtl number, Pr, Modified Jacob number, $Ja^{\ast}/Pr$, defined by an overall temperature difference, a property ratio $\sqrt{P_l{\mu}_l/P_v{\mu}_v}$ and the conjugate parameter ${\zeta}$. The similarity and simplified solutions obtained reveal the effects of the conjugate parameter.

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