Author(s): Shilong Liu; Ioan Nistor; Abodolmajid Mohammadian; Amir Azimi
Keywords: Tsunami-like bores; Dam break flow; Bed slopes; Experimental investigation; Kinematic behaviors
Abstract: Over the past decades, dam break flows generated by the sudden release of a prescribed volume of water have been adopted as a practical way to simulate and investigate tsunami-like, overland flowing bores. Extensive experimental and numerical modeling research related to dam break waves have been conducted for the case of propagation over horizontal beds. However, natural and artificial beaches exhibit slopes which significantly influence the kinematic behavior of propagating tsunami inundation. The objective of this study was to experimentally investigate the effects of the beach slope on dam break waves in terms of kinematic behavior during their propagation, interactions with and runup onto the structural wall. The physical tests were conducted in the Water Resource Engineering Laboratory at the University of Ottawa, Canada, using a rectangular tank with an impoundment depth of 250 mm. To simulate the inclined beds, 4 different slopes of 0, 5, 10 and 15 degrees were designed and installed at the bottom of the tank, against the downstream vertical wall. Ultra-sonic sensor placed in the vicinity of the impacted wall was used to record the time history of the bore runup on the wall. The free surface profiles at different instants were processed from video recorded using a high-speed camera. The wave front spatial advancement was obtained from the raw images extracted from the recorded bore propagation video. An analysis of the free bore surface showed that its shape only changed as it propagated over the slope. Lower runup heights of the bores on the wall were observed for the sloped cases, with maximum heights being 15 mm, 48 mm and 71 mm lower than those propagating over the horizontal bed, corresponding to the 5-, 10- and 15-degree slope cases. The wave front spatial advancement and velocity magnitude showed a decelerating effect of the slope on propagation of the bores. The arrival time and impact of the wave front on the downstream right wall was delayed by 0.15 s between adjacent cases from 0 to 15 degrees. The results of this study will be of assistance in the design of coastal infrastructure for inundation protection in tsunami prone areas.