دانلود رایگان مقاله تحلیل حرکت آوار به علت انسداد از موانع ثابت در جریان سونامی مانند

Abstract

Experimental research was conducted focusing on debris motion over a horizontal apron featuring vertical obstacles in the path of the debris propagation. The apron was designed as a typical representation of a harbor threatened by an inundating tsunami. The experimental setup idealized often complex harbor settings. The debris was a scaled-down 20-foot shipping container modelled at a 1 in 40 Froude length scale. Offand onshore regions were separated by a vertical quay wall which allowed the incoming elongated solitary wave used to represent the first part of a tsunami to steepen, break and propagate over the initially dry surface as a tsunami-like bore. In the path of propagation, a varying number of debris were entrained within the inundating bore over the horizontal apron. The entrained debris interacted with regularly spaced vertical obstacles representing infrastructure and houses within the propagation path. Varying debris and obstacle arrangements were tested to evaluate the effects the obstacles would have on the debris' maximum longitudinal displacement and the spreading angle. The main conclusion is that the spreading angle of the debris is not as significantly altered by the presence of obstacles on the harbor apron whereas the maximum longitudinal displacement of the debris was significantly affected.

5. Summary and conclusions

The presented experimental research was directed towards elucidation of mechanisms of debris motion over a horizontal apron area representing a typical harbor layout flooded by an incoming tsunami and focussed towards debris interaction with solid obstacles in nonstaggered (aligned) environments. As an idealization to the very complex prototype situation conceivable, debris were modelled by using 20-foot shipping container models at a 1:40 length scale in geometric scale which propagated over an ideally horizontal surface. The wave propagation section and the harbor apron area were separated by a vertical quay wall which allowed the incoming elongated solitary wave to steepen, break and propagate over the initially dry surface as a tsunami bore. In its path of propagation, a varying number of container models were entrained in the resulting flow, propelled and they eventually interacted with regularly spaced vertical obstacles. Some debris and obstacle arrangements were basically tested to elucidate the effects the aligned obstacles would have on the debris' maximum longitudinal displacement and the spreading angles. The presented data set of debrisobstacle interaction and the adjacent analysis may serve to calibrate and test numerical models that unlike experimental tests allow for investigating more diverse obstacle combinations in the future. Based on the given set-up, the following conclusions are drawn with regard to the bore front response to the debris and the debris motion itself: - The hydrodynamics of the incoming elongated solitary wave chosen herein resemble well those short riding waves which often occur in combination with rather long tsunami wave propagating and shoaling over the continental shelf towards the shore; the riding waves are a product of wave fission at the tsunami front leading to short waves with periods of 10–30 s in nature (undulating bores) which will most likely govern the impact to and of dislodged material on the nearby surrounding. The research is thus limited to this region starting at the shoreline and stretching some hundred meters inland where immediate impacts with other infrastructure might occur. - The bore front over the apron area was significantly deformed for cases with container models placed; the transfer of momentum from the bore front leading to entrainment and acceleration of the container models resulted in the bore front lagging behind the undisturbed sections of the bore front. At the same time, additional obstacles interacting with the incoming bore front resulted in focussing and channeling of energy through the gaps between the obstacles; those processes concurrently affected the transport of the debris within the extreme flow. - Compared to existing findings about the maximum longitudinal displacement of debris, it was found that a first row of obstacles significantly reduced this parameter. However, it is remarkable that the addition of a second row of obstacles had only limited effect on the maximum longitudinal displacement of container models. This is explained by the fact that a first row of obstacles led to channelized flow directing and guiding the entrained debris through the spacing between the second row obstacles rather than directly impacting them, as the second row of obstacles was not staggered.