行政院國家科學委員會專題研究計畫期中進度報告:三維度自由液面沉澱池水理與懸浮微粒傳輸之數值研究(1/2)
Date Issued
2005
Date
2005
Author(s)
DOI
932211E002023
Abstract
The main objective of this two-year project is to
numerically study water flow field and
suspended particulate transport in 3-D
free-surface sedimentation basins by
interruptedly considering the effects of mean
velocity and turbulence intensity distributions,
particle detention time distributions, suspended
load concentrations, sedimentation efficiencies,
shear distributions on basin bed, and free
surface. In the first year, a 3-D free-surface
water flow model is established to investigate
water flow field of sedimentation basins. The
water flow field within a sedimentation basin is
considered to be incompressible turbulent flow.
The transport of the incompressible turbulent
flow is herein simulated by the finite volume
method (FVM) together with three kinds of
commonly used turbulence models, i.e., the
traditional k- εmodel and the large eddy
simulation (LES). The difference of velocity
distribution pattern among the three turbulence
models is compared. A concentration
convection diffusion model is developed as well.
Numerical scenario simulations are carried out
for various geometry configurations, inflow
velocities, inflow turbulence intensities, inflow
suspended particle concentration, erosion
conditions on basin bed, and baffles. The water
flow field model is verified with available water
flume measurement. Finally, the particle
detention time analysis is performed based on
the building ventilation theory.
In the second year, a 3-D Lagrangian
particle tracking technique is developed to
investigate particle transport trajectories,
particle detention time, deposition patterns, and
concentration distributions in sedimentation
basins by releasing a large number of particles
(at least 1000 particles per simulation) into the
computational domain. The diameter of the
particle released ranges from 0.1 to1000 μm.
The particles released are tracked and recorded
until they hit the basin boundaries or flow out of
the basin. The particle tracking model, solved
by the 4th order Runge-Kutta method, is next
verified with available water flume
measurement. Numerical scenario simulations
are also carried out for various geometry
configurations, hydraulic conditions, and
concentration conditions. In addition, under the
same boundary and initial conditions, the
simulated results of particle detention time,
deposition patterns, sedimentation efficiency,
and concentration distributions by using the
concentration convection-diffusion model and
the particle tracking model are compared and
discussed. Results obtained from this research
are expected to offer engineers a design concept
for sedimentation basins.
Subjects
Free surface sedimentation basin
Suspended particle transport
Computational fluid dynamics
Particle trajectory tracking
Particle detention time
Publisher
臺北市：國立臺灣大學生物環境系統工程學系暨研究所
Type
report
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