STUDY ON TSUNAMI-INDUCED BOUNDARY LAYER USING MEASURED WAVEFORM OBTAINED BY GPS BUOYS

Abstract

 The tsunami-induced bottom boundary layer is investigated based on the actual waveform obtained by the GPS buoys along the coast of the Tohoku region during the 2011 Great East Japan Earthquake tsunami. The k-ω model is utilized for the numerical analysis in this study. As a result, the boundary layer thickness was found extremely thin compared to the water depth. The velocity distribution was similar to that of the bottom boundary layer under wind-generated waves. The flow regime is located in the transition region from smooth turbulence to rough turbulence. Because of this, the bottom friction is underestimated by the steady-state friction coefficient, such as the Manning formula. Therefore, a simple method for calculating the bottom shear stress due to an irregular tsunami which has been proposed in the previous study is employed to make a comprehensive investigation.