EAGER: Developing and Testing Algorithms for Generating Leading Tsunami Waves

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During the last forty years, solitary waves have been used as surrogate leading tsunami waves in laboratory studies. The data taken from the 2004 Indian Ocean tsunamis, however, show that the length and time scales for the solitary wave are too small in comparison with those of real tsunamis. This discovery poses a fundamental challenge for the tsunami research community, who currently interpret the existing results based on solitary wave theory. More importantly, this points to the need to investigate the feasibility of generating adequate long waves in a laboratory facility for laboratory research. Intellectual Merit: This research will use the newly installed wave makers with long strokes at Cornell University and the NEES tsunami facility at Oregon State University to test the hypothesis that the leading tsunami wave does not have sufficient time and distance to evolve into a solitary form, therefore challenging the currently used modeling approach for wave runup and other physical quantities based on the solitary wave. Since both wave makers are new, investments need to be made to develop algorithms for generating properly scaled leading tsunami waves. The critical question is to demonstrate if the wave length and wave period estimated by current solitary wave theory agree with recent field observations. Therefore, this research is timely and potentially transformative. The objectives of the research are as follows: (1) investigate and formulate the shape of characteristic leading tsunami waves, and (2) create and implement algorithms for generating desirable leading tsunami wave forms in both the Cornell and Oregon State wave flumes. This research has high risk but potentially high impact. If the research is successful, it has far-reaching implications on future tsunami laboratory research directions and community modeling approaches, including those of the NEES tsunami facility. Most of the laboratory results obtained in the past and their applications would need to be reevaluated. One reason that the solitary wave has been used in the past as the surrogate for the leading tsunami wave in laboratory studies for runup and wave force is that most existing wave flume facilities cannot generate the very long waves that represent leading tsunami waves. However, the new wave makers at both Cornell and the Oregon State tsunami wave facility now have the long stroke capacity to generate very long waves and test this hypothesis, and these two facilities complement each other in terms of range of applicable parameters. Broader Impacts: Successful achievement of the objectives of this research could lead to the following broader impacts. First, if the hypothesis is proven, then the 2004 Indian Ocean tsunamis clearly demonstrate that leading tsunami waves cannot be accurately represented by solitary waves in the laboratory, and new research directions and laboratory capabilities will be required for the field. Second, this project will utilize Oregon State University's Tsunami Experiment Databank and Notebook to capture and make all experimental data publicly available, as well as archiving all data in the NEES data repository, for reuse by future researchers. Third, a new piston wave maker was installed in Oregon State University's NEES Large Wave Flume, acquired through a recent NSF Major Research Instrumentation (MRI) award, and became operational in spring 2009. This award will expand the capabilities of that wave flume facility through the algorithm developed to generate very long waves through modification of the software that drives the hydraulic actuator assembly.