• Title/Summary/Keyword: Free Surface Flows

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A STUDY ON AN INTERFACE CAPTURING METHOD APPLICABLE TO UNSTRUCTURED MESHES FOR THE ANALYSIS OF FREE SURFACE FLOW (자유표면유동 해석을 위한 비정렬격자계에 적합한 경계면포착법 연구)

  • Myong, H.K.;Kim, J.E.
    • Journal of computational fluids engineering
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    • v.11 no.4 s.35
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    • pp.14-19
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    • 2006
  • A conservative finite-volume method for computing 3-D flow with an unstructured cell-centered method has been extended to free surface flows or two-fluid systems with topologically complex interfaces. It is accomplished by implementing the high resolution method(CICSAM) by Ubbink(1997) for the accurate capturing of fluid interfaces on unstructured meshes, which is based on the finite-volume technique and is fully conservative. The calculated results with the present method are compared to show the ease and accuracy with available numerical and experimental results reported in the literature.

Interaction of turbulences with non-breaking divergent waves in an open channel

  • Hwang, Ayoung;Seok, Woochan;Lee, Sang Bong
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.13 no.1
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    • pp.35-49
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    • 2021
  • This paper presents a direct numerical simulation of turbulent flows over a bump in an open channel to examine the turbulence characteristics near divergent waves emanating from the bump and to investigate the interaction of the turbulences with the divergent waves. To verify the reliability of the simulations, the mean velocity profile and root-mean-square of velocity fluctuations are compared with previous data. The anisotropic invariant maps show that the ratio of the streamwise to spanwise velocity fluctuations plays an important role in characterizing the anisotropic nature of the separated shear layer behind the bump in the vicinity of the free surface. The vortex identification discloses a large-scale streamwise vortical structure from the mean velocity field and a cluster of small coherent structures from the instantaneous velocity field, which are responsible for the anisotropic characteristics of the turbulence beneath the free surface.

Numeric Analysis of 2-Dimensional Nonlinear Viscous Free-Surface Wave Problems (점성을 고려한 2차원 비선형 자유표면파 문제의 수치해석)

  • Y.H. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.30 no.2
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    • pp.98-111
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    • 1993
  • Two-dimensional nonlinear free-surface wave problems are analyzed with consideration of viscosity. Navier-Stokes equation and continuity equation are solved by the application of Finite Analytic Method, and MAC scheme is used far the treatment of free surface. Surface tension effect is also considered and laminar flow is assumed. The free-surface waves in shallow water, the flows around a vortex-pair with free surface and the wave ahead of a rectangular body are simulated to test the present numerical scheme. In the shallow water problem, viscous effect due to the friction on the bottom is observed. In the second problem, the approach of a vortex-pair to the free surface is simulated to examine the interaction of vortex-pair with the free surface. In the third problem, the wave ahead of a semi-infinite floating body is simulated.

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Study on the Periodic Flows in a Rectangular Container Under a Background Rotation

  • Suh, Yong-Kweon;Park, Jae-Hyun;Kim, Sung-Kyun;Son, Young-Rak
    • Journal of Mechanical Science and Technology
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    • v.18 no.4
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    • pp.671-680
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    • 2004
  • We present numerical and experimental results of the periodic flows inside a rectangular container under a background rotation. In numerical computation, a parallel-computation technique with MPI is implemented. Flow visualization and PIV measurement are also performed to obtain velocity fields at the free surface. Through a series of numerical and experimental works, we aim to clarify the fundamental reasons of discrepancy between the two-dimensional computation and the experimental measurement, which was detected in the previous study for the same flow model. Specifically, we check if the various assumptions prerequisite for the validity of the classical Ekman pumping law are satisfied for periodic flows under a background rotation.

A method for incompressible free surface flow including surface tension using CSF model (CSF 모델을 이용한 자유표면 유동 해석)

  • Hong I. C.;Baek J. H.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.10a
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    • pp.15-18
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    • 2004
  • A numerical method for simulating two-phase flows including surface force is presented. The method is based on fractional step method of finite volume formulation and the interface is tracked with PLIC VOF method. In the CSF model, as color function, f, representing the location of interface varies steeply in the interface region, we need to use smoothed function f to get accurate unit normal and the curvature. Peskin kernel is used to get smoothed function f. A spherical drop in static equilibrium and three-dimensional merging of gas bubble are tested, resulting in the validation of this method

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Comparison of Volume of Fluid (VOF) type Interface Capturing Schemes using Eulerian Grid System (오일러 격자체계에서 유체율 함수에 기초한 경계면 추적기법의 비교)

  • Kim, Do-Sam;Kim, Tag-Gyeom;Shin, Bum-Shick;Lee, Kwang-Ho
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.32 no.1
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    • pp.1-10
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    • 2020
  • The application of multiphase flows is increasingly being applied to analyze phenomena such as single phase flows where the fluid boundary changes continuously over time or the problem of mixing a liquid phase and a gas phase. In particular, multiphase flow models that take into account incompressible Newtonian fluids for liquid and gas are often applied to solve the problems of the free water surface such as wave fields. In general, multi-phase flow models require time-based the surface tracking of each fluid's phase boundary, which determines the accuracy of the final calculation of the model. This study evaluates the advection performance of representative VOF-type boundary tracking techniques applied to various CFD numerical codes. The effectiveness of the FCT method to control the numerical flux to minimize the numerical diffusion in the conventional VOF-type boundary tracking method and advection calculation was mainly evaluated. In addition, the possibility of tracking performance of free surface using CIP method (Yabe and Aoki, 1991) was also investigated. Numerical results show that the FCT-VOF method introducing an anti-diffusive flux to precent excessive diffusion is superior to other methods under the confined conditions in this study. The results from this study are expected to be used as an important basic data in selecting free surface tracking techniques applied to various numerical codes.

Numerical Simulation of Free-Surface Flows around a Series 60($C_B=0.6$) model ship (자유표면을 동반하는 시리즈 60($C_B=0.6$) 선형 주위 유동장의 수치계산)

  • Myung-Soo Shin;Kuk-Jin Kang
    • Journal of the Society of Naval Architects of Korea
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    • v.33 no.2
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    • pp.13-29
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    • 1996
  • This paper presents calculated results of the free-surface flow around a Series 60($C_B=0.6$) model. Three-dimensional Navier-Sotkes equations are solved and Baldwin-Lomax algebraic turbulence model is adopted to simulate the high Reynolds-number flow. To reduce computational efforts, velocity components near the wall are extrapolated with a the solved by using the Implicit Approximate Factorization method[2]. The successive-over-relaxation method is used for solving pressure-Poisson equation when obtaining the pressure field projecting the divergence-free velocity field. To simulate the free-surface flows more precisely, the numerical scheme solving the equation for the kinematic boundary condition is very important. In this paper, there numerical schemes are employed and the results are compared with the available experimental data.

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Turbulence effects on surface pressures of rectangular cylinders

  • Li, Q.S.;Melbourne, W.H.
    • Wind and Structures
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    • v.2 no.4
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    • pp.253-266
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    • 1999
  • This paper presents the effects of free-stream turbulence on streamwise surface pressure fluctuations on two-dimensional rectangular cylinders. Particular attention is given to possible effects of turbulence integral scale on fluctuation and peak pressures. The mean, standard deviation, peak pressure coefficients, spectra and cross-correlation of fluctuating pressures were measured to investigate the nature of the separation and reattachment phenomenon in turbulent flows over a wide range of turbulence intensity and integral scale.