• Title/Summary/Keyword: energy transport

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Interscale transport of the Reynolds stress in a turbulent boundary layer subjected to adverse pressure gradient (역압력 구배 난류 경계층에서 레이놀즈 응력의 스케일 간 수송)

  • Yoon, Min
    • Journal of the Korean Society of Visualization
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    • v.20 no.1
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    • pp.38-44
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    • 2022

  • An interscale transport of the turbulent kinetic energy (TKE) and Reynolds shear stress (RSS) is examined in an adverse pressure gradient (APG) turbulent boundary layer (TBL). The direct numerical simulation data of an APG TBL at Reτ = 834 and β = 1.45 is employed. The TKE and RSS transport equations are divided into large and small scales, leading to the introduction of interscale transport. The TKE mainly transfers from large scales to small ones in the outer region, and vice versa for the RSS. An interscale transport of TKE and inverse interscale transport of RSS are amplified by APG, and the latter results in the increase in large scales of TKE production. Some of outer large scales of enhanced TKE transfer to small scales and then dissipate by viscosity, and the remains dissipate turbulent-non-turbulent interfaces by turbulent transport.

  • https://doi.org/10.5407/jksv.2022.20.1.038 인용 PDF KSCI

Applications of the Sediment-Transport Path Model to the Tidal Flats of Garolim Bay, West Coast of Korea

  • Shin, Dong-Hyeok;Yi, Hi-Il;Han, Sang-Joon;Oh, Jae-Kyung;Won, Joong-Sun
    • International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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    • v.23 no.1
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    • pp.39-51
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    • 1995

  • Bidirectional transport trend using the sediment-transport path model was identified in the two areas, sand ridge area and tidal mudflat in Garolim Bay, which is located in the mid-western coast of Korean Peninsular. This model exhibits the two-dimensional view of clear sediment transport trend based on data of changes in sediment statistics such as mean, sorting, and skewness, Garolim Bay was selected to test for the sediment-transport path model developed by McLaren and Bowles [1985]. Line-S, a typical tidal mudflat and representative of the Garolim Bay tidal flats, is well tested by this model, showing a clear seasonal change and coarsening-trend seaward (case C). This indicates that strong ebb currents carried relatively coarser sediments seaward with respect to high energy regime. Seasonally, this energy regime slowly decreases toward the summer in contrast with an increase of energy regime of flood tides, carrying coarser sediments landward (case C) in the summer. However, the Line-D area does not show consistent transport trend with respect to time-series. Separated and scattered events show fining trend landward (case B) in the sand ridge itself. The finining-trend (case B) either seaward and landward is not chiefly important in both the entire Line-D area and sand ridge itself. Also, the coarsening-Trend (case C) landward is not significant in the sand ridge itself. Consequently, in reality, the selection of suitable and representative locations are very important to fit with this model.

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Convergence study of traditional 2D/1D coupling method for k-eigenvalue neutron transport problems with Fourier analysis

  • Boran Kong ;Kaijie Zhu ;Han Zhang ;Chen Hao ;Jiong Guo ;Fu Li
    • Nuclear Engineering and Technology
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    • v.55 no.4
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    • pp.1350-1364
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    • 2023

  • 2D/1D coupling method is an important neutron transport calculation method due to its high accuracy and relatively low computation cost. However, 2D/1D coupling method may diverge especially in small axial mesh size. To analyze the convergence behavior of 2D/1D coupling method, a Fourier analysis for k-eigenvalue neutron transport problems is implemented. The analysis results present the divergence problem of 2D/1D coupling method in small axial mesh size. Several common attempts are made to solve the divergence problem, which are to increase the number of inner iterations of the 2D or 1D calculation, and two times 1D calculations per outer iteration. However, these attempts only could improve the convergence rate but cannot deal with the divergence problem of 2D/1D coupling method thoroughly. Moreover, the choice of axial solvers, such as DGFEM SN and traditional SN, and its effect on the convergence behavior are also discussed. The results show that the choice of axial solver is a key point for the convergence of 2D/1D method. The DGFEM SN based 2D/1D method could converge within a wide range of optical thickness region, which is superior to that of traditional SN method.

  • https://doi.org/10.1016/j.net.2022.12.034 인용 PDF