Author(s): M. A. F. Sadeque; N. Rajaratnam; M. R. Loewen
Linked Author(s): N. Rajaratnam, Mark R. Loewen
Keywords: Habitat structure; Submerged flow; Bed shear stress; Three dimensional wall wakes
Abstract: This paper presents the results of an experimental study of flow around a cylindrical habitat structure on a smooth bed. Cylindrical objects of equal diameter and four heights were tested under similar flow conditions producing four different levels of submergence. Bed shear stress was measured around the objects using a thin yaw-type Preston probe at a fine spatial resolution. The experimental results clearly depict the location, extent and relative difference in bed shear stress amplification and reduction for the different flow regimes. Large bed shear stresses occur in the vicinity of the transverse face of the object in all the flow regimes. The non-submerged object creates the most significant amplification of bed shear stress over a larger area, where the maximum bed shear stress is about two times of that observed for flow around a deeply submerged object. The other two regimes create almost equal amplification of bed shear stress. However, the lateral extent of increased shear stress is larger for the moderately submerged object than that of slightly submerged object. Shear stress fields on the downstream side of the objects indicate the relative performance of the objects in developing a shadow from the surrounding high velocity flow for the in-stream species. Moderate or deeply submerged objects would develop a relatively wide and closed wake region immediately downstream of the object, but non-submerged or slightly submerged objects would provide narrow and relatively longer near field wakes.
Year: 2005