Numerical Simulation of Two-dimensional Unsteady Flows in River channels-the Yuanshantze Diversion Case
Date Issued
2010
Date
2010
Author(s)
Lin, Chen-fu
Abstract
The objective of this study is to apply 2D numerical method of characteristics to investigate relation of flow and stage elevation at the Yuansantze Diversion Section of Keelung River. It is intended to develop such a relation for practical engineering purposes to predict inflow and discharges through all of the outlets so that a better flood control and facility maintenance can be achieved.
Numerically, a two dimension model of Characteristics is introduced and repeated to observe it performance properly. After applying a rainfall-runoff model for the upstream basin which has a outlet at the inflow cross-section and check the flow conditions, it is found that a hydraulic jump is impossible to occur at the downstream of the inlet under sub-critical flow condition. However, it was found that water elevations of field stages in this area indicate water elevations of downstream stages are higher than those of upstream in most cases. Rather, there are only two cases in which water elevations of the upstream gage stations are higher than those of downstream stations. One case is use for model calibration and the other for model verification. The computed results are compared with field measurements. Reasonable comparisons are observed. The difference may due to the effects of sudden closure of the sand gates. Mass conservation is checked as required.
It is well known that there is no unique rating cure between discharge and elevation for unsteady flows. It is risky to extend rating cure based on steady assumption. An accurate numerical 2D model to simulate flows through a complicate river sections is strongly in need. A capability of the model to simulate the controlling behavior of sand gates is recommended to be incorporated into the numerical model for better simulations in the future.
Subjects
MOC numerical method
calibration
unsteady flow
flow-stage relation curvel
mass conservation
Type
thesis
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