Fluid-Structure Interaction of Cylinders by Combining the Cosserat Beams Theory and Immered Boundary Methodology

Abstract

A fully coupled simulation of three dimensional problems involving fluid structure interactions is the most accurate wa y t o predict the behavior of high aspect ratio cylinders in cross flows. The main interest in this kind of flows are due the great number of applications in the oil and gas industry (especially the ones related to the modeling of risers used for oil exploitation in deep seas), howeve r there are inherent difficulties in the simulation of the fluid structure interaction of long and thin cylinders, as example the high computational cost due the fact that a cylinder is moving across the computational domain associated with the necessity of the structural model be able to deal with high displacements. In this work we circumvent these difficulties by the joint of two methodologies: the combination of the Cosserat theory applied to slender beams, and the Immersed Boundary Methodology, which is used to represent the interactions between the structural and fluid domains. The main features of the proposed methodology are evaluated by means of a number of numerical simulations, both in static and dynamic regimes, regarding the structural model, in a first step and the complete fluid-structure model, in a second step. The results obtained permits to evaluate the accuracy and the main advantages and shortcomings of the methodology, especially regarding the numerical aspects. The results also, allow t o put in evidence some relevant phenomenological aspects related to the dynamic behavior of cylindrical structures with various levels of bending flexibility, subjected to transverse flows characterized by different values of the Reynolds number.