NUMERICAL SIMULATION ON PRESSURE FLUCTUATIONS OF AIR-WATER TWO-PHASE FLOW IN UNDERGROUND PIPELINE CAUSED BY TSUNAMI

Abstract

 Numerical simulation of hydraulic model tests for tsunami that is air-water two-phase flow in the underground pipeline was performed by OpenFOAM, and the applicability of OpenFOAM and the influence of gas phase were verified by comparing the calculation results with the hydraulic model test results. As a result, it was confirmed that the advantage of OpenFOAM in the case of pipeline or gas phase calculation target, and that the initial state inside the pipeline influences flow and pressure distribution. Also, not only the water surface elevation at the exit of the pipeline and flooding depth, but also the air mass in the pipeline and the gas phase velocity was reproduced well. However, large pressure fluctuations associated with the air hammer phenomenon were not reproduced. In order to reproduce the overflow phenomenon at the time of the arrival of the tsunami, it is necessary to consider the air-water two-phase flow in the underground pipeline. In order to further improve the reproduction accuracy, a method such as calculating a compressive fluid can be considered.