| Author | Le Van Duc |
| Call Number | AIT Thesis no.WA-94-3 |
| Subject(s) | Hydraulic models--Mathematical models
|
| Note | A thesis submitted in partial fulfilment of the requirements
for the degree of Master of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | A two-dimensional depth averaged flow model is developed in this study to simulate
the subcritical, supercritical and circulating flow in an open channel transition including
complicated vertical sidewalls.
The circulating flow can be described by using the Boussinesq equation of unsteady
flow and the Velocity Averaging Procedure. In this study, the Boussinesq terms in the
momemtum equations were neglected. Under constant boundary conditions, the steady flow
problem can be solved by using the unsteady flow equations with time increment as an
iterative parameter. A coordinate transformation combined with the perfect slip wall
assumption has been developed to transform the coordinates of the irregular vertical sidewall
into computational, regular domain. The governing equations in the transformed system are
then solved numerically by using the developed Explicit Finite Difference scheme which
consists of four steps; Predictor, corrector, Maccormack solution and velocity averaging. A
computer program written in FORTRAN77 language has been developed for the present
model. In addition to this program, another two supplementary programs written in TURBO
PASCAL 6.0 language have also been developed for the convenience of graphical analysis
of the computed results.
The present numerical model has been verified by comparing its computational results
with either/both the experimental data or/and other numerical results for five cases, namely i)
supercritical flow in a contraction; ii) supercritical flow in a gradual expansion; iii) flow in
an abrupt expansion channel; iv) flow in a channel and pool system; and v) jet discharging
into a pool. A good agreement has been obtained for most of these cases. A sensitivity analysis
of the model parameters, including dissipation coefficient a., grid size ~x, Manning coefficient
n, longitudinal bed slope S0 x, upstream Froude number Frup has also been done for case i) and
case iii). The results show that the dissipation coefficient plays an important role not only for
numerical stability but also for the correct description of occurrence of flow circulation and
the flow energy loss in an open channel transition. The Manning coefficient has less effect on
subcritical flow while it becomes more significant in supercritical flow. The bed slope (mild
bed slope) is of less effect in the supercritical flow. On contrary, it becomes more important
in subcritical flow. The Froude number at upstream end has strong effect on supercritical flow.
The grid size affects significantly on the occurrence of flow circulation, the model accuracy
and the computer time consumption. |
| Year | 1994 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Water Resources Research Engineering (WA) |
| Chairperson(s) | Tawatchai Tingsanchali |
| Examination Committee(s) | Imamura, Fumihiko ;Sutat Weesakul
|
| Scholarship Donor(s) | Japan-Asian Development Bank |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1994 |