Date

2018

Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Mechanical Engineering

First Adviser

Oztekin, Alparslan

Abstract

Flows past bluff bodies are encountered in many engineering applications. The bluff body situated in the flow experience a significant amount of pressure drag force. Therefore, it is important to predict flow conditions around bluff bodies when designing bridges, platforms, pipelines near seabed, offshore structures, and hydropower systems. In several engineering applications, structures could often be placed near surfaces. Transient flows past rectangular plates in the vicinity of surfaces are investigated in this study. Flow patterns and hydrodynamic forces acting on the plates become increasingly complicated due to the interactions between the plates and the surfaces. The study of free surface and wall proximity effects reveals that the drag exerted on the plates is sensitive to the submergence depth and the wall gap. Asymmetric flow patterns and an increase in drag coefficient of the plate are observed when the plate is placed near the surface. The array configuration of yawed plates provides distinct properties than tandem arrangements of plates, which are placed perpendicular to the flow. The yawed plates can be placed in a tighter arrangement without a significant penalty on drag reduction. Furthermore, with suitable spacing, the surface proximity effects increase the drag force exerted on plates when compared to those placed away from the wall. This study can help in optimizing the power generation of marine current energy harvesting systems, which consist of translating blades that operate in rivers or beneath offshore platforms.

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