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Improved Numerical Simulation Against Overflow from Embankment Under Steady and Unsteady Flow Conditions by Considering Non-Hydrostatic Pressure

Author(s): Yoshiya Igarashi; Norio Tanaka

Linked Author(s): Norio Tanaka

Keywords: Piezometric head; Overtopping flow; Tsunami inundation; Flow rate; Embankment modelling

Abstract: High accuracy simulation of overtopping flow from an embankment is required. It helps in better understanding the inundation volume and house-breaking situation. When tsunami inundation is simulated on a real scale, wide area, two-dimensional non-linear long-wave equation model (hydrostatic pressure theory) is often used, as CPU time is not large. In this study, an improved method is proposed. This method can simulate tsunami -like flow with non-hydrostatic pressure theory and has almost the same computational load with the non-linear long-wave equation model. Although the method itself can be applied to two-dimensional flow, the method was tested on a one-dimensional depth-averaged non-hydrostatic equation. Comparing the results from unsteady flow flume experiments, the stability of the improved method, the accuracy of overtopp ing volume from the embankment and the flow depth around the embankment was confirmed. In addition, in order to verify the influence of non- hydrostatic pressure term, a non-linear long-wave equation with the hydrostatic pressure approximation was compared with the improved method, with the non-hydrostatic pressure. It was found that the hydrostatic pressure theory underestimated the overtopping volume from an embankment by about 15% when the width of the top of embankment is narrow. Simulation results of fluid force index, (squared velocity times flow depth) that indicates the probability destruction of houses, are compared with flume experiment results and shown to be highly accurate.


Year: 2020

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