Wave run-up and stress imposed on a permeable coastal bed sample of the Caspian Sea


deputy of research and technology


This research aims to reconsider the wave run-up and eulerian schematic of flow contours and the fluid movement path in the sediment sample gathered from southern Caspian Seashore bed, using experimental method in wave flume.The general characteristics of flow depend on the kind of bed structure, the bed shear tension, vertical velocity profile and the permeation velocity, could be changeable. While, because the increasing of water surface height, the fluid penetrates bed, and consequently the suction phase happens within the bed. Through this condition the flow contours approach the bed and the mean velocity accelerates near the bed, and then the tension rises about 3 times.
Because the decreasing of water surface height, the fluid permeates out from the bed and the injection phase happens, so that the flow contours get away from the bed and the mean velocity falls down near the bed , so the tension slakes about 80%. This studyuses 3 waves with a sharpness ranges from 0.01 to 0.06.The wave run-up has been measured using the wave height recorders which have been installed on a ramped shore with a constant slop of 1:5.
By using a camera under water and also color injection into the bed, the flow contours and movement path of fluid in the sample of Caspian Sea, the permeability ranges have been drawn.Meantime, the flow velocity is estimated in two positions including near the bed surface and the bed deep. Through the relative non-dimensional permeation velocity (Ũ=Vz/Vx), it is shown that in a given wave frequency, by increasing velocityin the suction phase, the tension imposed on the bed is risen up, whiles by increasing the relative velocity in injection phase the tension imposed on the bed is fallen down.


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