Instabilities in the bottom boundary layer under a transient surface wave

Project4_1(collaboration with Prof. Phil Liu)
Tsunami waves are long highly nonlinear transient surface waves whose destructive effect is well-known. U-tube laboratory experiments serve as a model to investigate the boundary layer dynamics under such a long wave over a region limited in the along-wave direction. We are using direct numerical simulations of the U-tube configuration and hydrodynamic instability analysis tools to study the transition to turbulence under a surface solitary wave. The transient nature of such a wave, as sensed by a stationary observer, gives rise to a near-bed base flow whose stability properties might not always be described by classical stability analysis. In close collaboration with Prof. Luis Parras at the University of Malaga in Spain, we are applying alternative stability analysis tools to more effectively characterize and interpret the above transition, and its associated coherent structures, in both two and three dimensions. The PhD student conducting this research is Mr. Mahmoud Sadek, whose primary advisor is Prof. Liu.