Abstract
Motivated by the recently developed bottom-tilting wavemaker specially designed for tsunami research, we propose to investigate numerically the wave generation mechanism of this new wave generator. A series of numerical experiments is carried out using a RANS-based computer model to evaluate the effects of wavemaker length, bottom displacement, motion duration, and water depth on the wavelength, wave amplitude, phase speed, and waveform of the leading waves produced by the bottom-motion wave generator. Numerical results fit well with the existing laboratory data. Explicit equations for the wavelength and wave amplitude are developed and can serve as the guideline for wave generation. Encouraging results suggest that bottom-tilting wavemaker is a good alternative to the traditional piston-type wavemaker for tsunami research.
Highlights
In the past two decades, we have suffered nearly 20 tsunamis that caused an unprecedented economic impact of US$280 billion and some 250,000 casualties in total, where the recorded losses over the previous twenty years were close to US$2.7 billion and 1000 deaths [1,2,3]
It has been widely criticized that the massive loss of life in the 2004 Indian Ocean tsunami can partially be imputed to the lack of general awareness and knowledge of tsunamis and the absence of an operational tsunami early warning system, which issues a technological warning of tsunami when a substantial seismic activity detected by a network of seafloor-mounted sensors is predicted by the use of numerical wave models to generate significant tsunami waves [1,5]
Inspired by the bottom-tilting wavemaker proposed by Lu and colleagues for tsunami research, we perform numerical wave tank experiments to facilitate a better understanding of the generation and control mechanisms of the new wavemaker, where waves are generated by the tilting of the movable tank bottom
Summary
In the past two decades, we have suffered nearly 20 tsunamis that caused an unprecedented economic impact of US$280 billion and some 250,000 casualties in total, where the recorded losses over the previous twenty years were close to US$2.7 billion and 1000 deaths [1,2,3]. A group led by Allsop and Rossetto [29,30,31] developed and improved a pneumatic tsunami simulator capable of generating stable long waves with effective wavelengths up to 28 m [32] In their design, waves are driven by disturbances directly imposed on the free-surface. We remark that the above-mentioned three novel flume generators, based on very different design concepts, share a common ground that they all relax the inherent wavelength-stroke limitation of a piston-type wavemaker This makes them more suitable for laboratory tsunami research. Ma, Shi, and Kirby [41] developed a Navier–Stokes solver in the σ-coordinate system that can predict instantaneous free-surface elevation and three-dimensional (3D) flow field In their non-hydrostatic wave model, nicknamed NHWAVE, a shock-capturing Godunov-type finite volume scheme was employed for spatial discretization and the time marching was performed by a second-order Runge–Kutta scheme. We will present the results of our tests on the control of wave generation (Section 3) followed by conclusions and discussion (Section 4)
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