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2021-06-18T13:45:03+09:00
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Ritsumeikan Univ.KO-569
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14.25 0 0 14.25 95.9827 788.25 Tm
(Numerical Modeling of Bedform Development in Turbulent Flows)Tj
/TT1 1 Tf
12 0 0 12 462.6719 759.75 Tm
(NGUYEN QUOC Y)Tj
-34.848 -2.313 Td
(Sedimentary bedform development is one of the fundamental problems in hy\
draulic engineering and has)Tj
-1 -1.5 Td
(been the study subject of numerous researchers. However, although statis\
tical quantities of bedforms in)Tj
0 -1.5 TD
(various flow and sediment conditions have been reported extensively, phy\
sical mechanisms of their initiation)Tj
T*
(and development remain poorly understood. Aiming to achieve detailed und\
erstanding of such mechanisms,)Tj
T*
(development of bedforms in turbulent flows is studied numerically in thi\
s study. The interested flows are in)Tj
T*
(hydrodynamically smooth regions where effects of individual sediment par\
ticles on the flow fields are)Tj
T*
(negligible. Initiation and evolution of bedforms from flat beds are repr\
oduced by a model consisting of three)Tj
T*
(modules which are coupled to each other: a module for hydrodynamic equat\
ions based on the Large-Eddy-)Tj
T*
(Simulation \(LES\) and Immersed-Boundary-Method \(IBM\) which are implem\
ented on fixed Cartesian grids, a)Tj
T*
(module for sediment transport based on van Rijn's \(1984\) bedload formu\
la, and a module for 2D bed surface)Tj
T*
(evolution based on the Exner-Polya equation. The model is first validate\
d with test cases of bed shear stress)Tj
T*
(distributions and mean flow fields over fixed sinusoidal bed surface in \
open channel flows, by comparing)Tj
T*
(with reported results computed by the traditional body-fitted Direct-Num\
erical-Simulation \(DNS\) method.)Tj
T*
(The model is also shown to be able to produce realistic flow fields wher\
e the bed surface is evolving.)Tj
1 -2.5 Td
(Test cases of sand wave evolution from flat beds in various flow and sed\
iment conditions are then)Tj
-1 -1.5 Td
(conducted. Computed results are analyzed in four categories: threshold f\
or bedform initiation, the first sand)Tj
T*
(waves appearing on a flat bed, initiation and evolution of successive wa\
ves which fill up the bed surface, and)Tj
T*
(fully developed dimensions of the sand waves. Qualitative and quantitati\
ve comparisons with the)Tj
T*
(experimental observations are made and agreements on major characteristi\
cs of the above categories are)Tj
T*
(observed. To the author's knowledge, this is the first numerical work on\
this problem which can reproduce)Tj
T*
(real-time interaction between evolving bedforms and a three-dimensional,\
fully solved flow field.)Tj
ET
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