| Author | Tran Thuc |
| Call Number | AIT Diss. no. WA-91-02 |
| Subject(s) | Hydraulic structures--Mathematical models
|
| Note | A Dissertation Submitted in Partial Fulfilment of the Requirement for the Degree of Doctor
of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. WA-91-02 |
| Abstract | Two morphological models for computation of local scour and deposition of sand
bed near hydraulic structures were developed in this study. Only the case of sediment
bedload was considered. The first model dealt with the morphological computation based
on the two-dimensional width-averaged flow condition. The second model dealt with the
two-dimensional depth-averaged flow condition.
In order to verify these models, two experimental studies, one relating to the widthaveraged computations and the other to the depth-averaged computations, were carried out
to investigate the flow characteristics and bed deformations. The first experiment was a
channel flow with and without a sluice gate and a movable bed from a certain downstream
location. The second experiment was a flow in a rectangular pool with a slot jet entering
horizontally and also with a movable bed.
Two-dimensional hydrodynamic models for the width-averaged and depth-averaged
computations were used to compute the turbulent velocity field and local bed shear stresses
for input to the morphological models. The hydrodynamic models were based on the full
two-dimensional Reynolds equations of mean flow and the k-E model closure. For the
morphological models, the sediment balance equation, the equation of non-equilibrium
sediment transport and the sediment transport formulae were solved by using an explicit
finite difference technique of the modified Lax-scheme. The spatial lag effect of bedload
transport due to the entry of clear water at the upstream boundary, the influence of local
turbulent velocity fluctuation on sediment transport and the effect of local bed slope were
taken into account in the computations. The hydrodynamic model and the morphological
model were linked by a quasi-steady computational procedure.
The computed results of the hydrodynamic models and the morphological models
were compared with the experimental data. The agreement was found to be very
satisfactory. Two major conclusions are drawn from this study. Firstly, the non-equilibrium
sediment transport model was found to be necessary in local scour and deposition
computation, the results of the morphological models would be very poor if the equation
of non-equilibrium bedload transport was not used. Secondly, the effect of turbulent velocity
fluctuation could be successfully incorporated in the computation of the bed shear stress and
local sediment transport. This effect was calculated based on the turbulent kinetic energy
computed from the k-E model. Sensitivity analysis was made to study the influence of
relevant model parameters on the computed turbulence characteristics and velocity field, the
sediment transport rates and the bed elevations. |
| Year | 1991 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. WA-91-02 |
| Type | Dissertation |
| School | School of Engineering and Technology |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Water Resources Research Engineering (WA) |
| Chairperson(s) | Tawatchai Tingsanchali ; |
| Examination Committee(s) | Suphat Vongvisessomjai ;Gupta, Ashim Das ;Huynh Ngoc Phien ;Rodi, Wolfgang ; |
| Scholarship Donor(s) | The Government of Japan ; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1991 |