The use of dam break model to simulate tsunami run-up and scouring around a vertical cylinder

Abstract

This research paper deals with the use of a dam break system to generate a surge model to study tsunami run-up, run-down and scouring around a vertical cylinder. The dam break system was provided with one or two gates to store water at a predefined depth; the water could then be quickly released by opening the gates to create a tsunami surge that runs up on land. In addition, numerical simulations of dam break surges resulting from various lengths of reservoirs were conducted to obtain more findings for further analysis regarding the characteristics of the dam break surges. A vertical cylinder model was installed on the beach at 6 meter downstream of the main gate to study the scour caused by the tsunami surge. The bed material was fine sand with a 0.19 mm diameter. The results were compared with existing experimental results. The comparison indicated that the dam break surge can be used to simulate tsunami surges by adjusting the reservoir length, the reservoir depth and the water depth downstream of the gate. The ratio of the difference between the upstream and downstream water depth on one side to the length of the reservoir on the other affect the run-up height and duration. Thus, this ratio should be considered when simulating tsunami based on dam break systems. Although different in magnitude, the shape of both the surge mareogram and the velocity time history of the tsunami surge generated using dam break system was comparable with the tsunami surge induced by a solitary wave generated using a long flume. For the relatively large cylinder located at the bore location, the separation flow was strongly directed to the wall which produced significantly unsymmetrical scour result.