WAVE PERIOD EFFECTS ON A FLOW AND SHEAR VELOCITY AROUND SUBMERSED POROUS MEDIA

Abstract

 The flow around and inside a submerged porous media (porous submersed breakwater) was measured by the particle image velocimetry with the refractive index matching method. Experiments were carried out under different wave period conditions for long period waves. The developmental process of strong shear flow at the top and shoulders of the submerged breakwater was clarified from the microscopic flow field.

 Compared to the upper current, the inner current of the submerged breakwater is about one order of magnitude smaller. However, periodic flows corresponding to the wave period were observed in the horizontal and vertical components of the inner flow of the submerged breakwater. For the horizontal component, in addition to the presence of a constant phase difference from the upper flow, periodic fluctuations shorter than the wave period were observed. The vertical structure of a strong shear flow field at the top of a submerged breakwater, which cannot be observed by non-clairvoyant measurements, was quantitatively clarified.