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Advanced Taiwan Ocean Prediction System

Tseng, Tsu-Lun - ALL News | 2020-09-04 | Count:21

 

Title: Using Numerical Simulations and Field/Lab. Experiments to Study the Riverbed Scouring

Abstract:

Taiwan is located at the subtropics zone of the West Pacific Ocean. It is frequently struck by typhoons with raging storms and heavy rains during the raining seasons. That results the rivers not only are fast-flowing with high discharge, but badly erode their beds during the typhoon seasons. To study this issue, a nested modeling system is proposed which is a simulation ranged from the watershed of the catchment to the river, and to section scales. And the float-out device and acoustic Doppler current measure of field experiments were also conducted to verify model simulations. Besides, it is known that the hydraulic structures are usually installed along with rivers in Taiwan to prevent erosion. Setting spur and groundsill is the most common way to protect the underlying riverbed. The study also conducted a small-scaled experiment in the laboratory which was similar to field site with adopting the discharges of different return periods and measured the flow field by laser doppler velocimetry (LDV). Then the protective effects with different spur types were discussed. The groundsill is another common structures to protect the underlying riverbed. And our reach is mainly covered by Alluvial fans and much of its sediment is obstructed by the groundsill from upstream. This leads to the bedrock exposures and local scour downstream. This study tried to discuss the mechanism for the occurrence of equilibrium and non-equilibrium scour holes by using a particle image velocimetry (PIV) measurement system to study groundsill issue.

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