RUNUP OF A SURFACE SOLITARY WAVE ON A THIN VERTICAL SEMI-SUBMERSED SCREEN
Authors:   Institute of Hydromechanics of the NAS of Ukraine, Gorban I.M. , Korolova A.S. ,   Institute of Hydromechanics of the NAS of Ukraine, Sokolovsky G.P. ,   Institute of Hydromechanics of the NAS of Ukraine
Published: July 2023

Global climate changes lead to an increase in the number and intensity of extreme events in the seas and oceans (tsunamis, floods, storm surges, etc.). This can have catastrophic consequences involving the destruction of civil infrastructure, the flooding of large areas of recreational land, the loss of life, and can also adversely affect water quality, sediment transport, and habitats for living organisms. The creation of artificial berms on the seabed and breakwater piers changes significantly the parameters of wave processes, reducing destructive effect of waves in the coastal zone. But the use of traditional coastal protection structures (dams, piers, breakwaters) is not always efficient and economically reasonable. Thin permeable barriers are increasingly being considered as an alternative option in providing economic and ecological protection of coastal areas. The purpose of this research is to substantiate the effectiveness of vertical semi-submerged walls for protection the shores of natural reservoirs from the destructive energy of surface waves. Such a structure is non-permeable near the free surfacer, and is supported by piles at some distance from the bottom, which allows the flow of water and sediments. The physical simulation of the interaction of a nonlinear solitary wave, which is considered as a tsunami model, with a semi-submerged thin vertical barrier is performed in the experimental channel to evaluate the effectiveness of vertical wave barriers against the destructive energy of long waves. It was found that interaction of a solitary wave with an overhanging vertical wall leads to generation both of the reflected wave, due to roll of the incident wave on the structure, and the transmitted wave, which is formed after the liquid mass passes through the gap between the bottom and the wall. Quantitative characteristics of the interaction of the wave with the obstacle were obtained with the help of capacitive sensors, which were installed along the main axis of the laboratory channel to record the free surface disturbances caused by the propagation of the wave in the channel, its reflection from the wave screen and its transmission downstream. The processing of the received data made it possible to estimate the parameters of a solitary wave, which was formed in the channel by the impact of a heavy body on the water surface, those are the amplitude, length, and velocity of wave propagation. The energy attenuation of a solitary wave is estimated, which is an important characteristic of the channel and makes it possible to obtain more accurate values of reflection and transmission coefficients. Evaluations of wave reflection and transmission coefficients show that thin partially submerged vertical barriers are sufficiently effective in reducing the energy of nonlinear solitary waves although they do not suppress the waves completely. The depth of the screen-type permeable obstacle immersion relative to the free surface has a significant influence on the reflection/transmission coefficients and its effectiveness, accordingly. It has been established that semi-submerged obstacles can dissipate up to 60% of the incident wave energy.