Investigation of Turbulent Structure around Bottom Mounted Structures with Porosity Variations

摘要

This paper presents the experimental findings on the turbulent structure in the vicinity of bottom mounted structures of an open channel. Three model structures used in this study have geometric porosities of 0%, 34.9% and 47.5%. Detailed measurements of the velocity fields, turbulent intensity components, and dissipative eddy size were taken by the acoustic Doppler velocimeter (ADV) at different locations around the structures. Near the interface, it is found that the dissipative eddy size is equal to 0.048, 0.082, and 0.129 mm for the solid structure, 34.9% porous structure, and 47.5% porous structure, respectively. These data sheds some light on the numerical modeling of flow over porous structures. The dissipative eddy sizes suggest the eddy motion may across the interface into the gaps of the porous structures. This interaction of the free turbulent flow with the flow inside the porous structure may result in the penetration of turbulence into the upper area of the porous structure and to increased turbulence levels.