Flow Induced Excitation on basic shape structures

The study of flow-induced vibrations, on structures and obstacles, is one of the main topics of fluid dynamics related to the practical interests in a large number of field application such as aerodynamic, mechanical, civil, naval engineering, etc. New design and project techniques have offered hazardous solutions, consisting in structures, which are more and more slender and flexible. This has led to a number of self-excited vibration situations due to the interaction between the flow field and the structure. Forces coming from this mechanism depend upon both the incoming flow and the structure motion, giving rise to a strong non conservative force field, which may eventually lead to a growing structure motion. There are several structures related to such problems requiring therefore special fluid-elastic studies as well as physical and numerical model. In spite of this trend of design evolution, the fluid-structure interaction mechanism on basic shape is studied extensively. As a matter of fact it still presents several open questions and the understanding of the fluid-structure interaction mechanism on basic shape is not only helpful but also necessary to improve the knowledge on the flow-induced vibrations. The aim of this chapter is to offer an overture about the phenomenon of the fluid-structure interaction. After the introduction to the theoretical and practical interests on this topic and the evolution in the last decades, the fluid-structure interaction will be discussed considering the flow as source of excitation and then analysed in terms of dynamic response of the structure. These two features of the same phenomenon are important to understand the inmost relation between flow distortion due to the obstacle and induced excitation on the obstacle generated by the flow distortion itself. It mainly referred the discussion on basic shape obstacle like cylinders, circular or rectangular and sphere because of the importance that such shape have in the practical applications and of the generalization that this shape allowed.