# Fluid-structure interaction with NURBS-based coupling

## TL;DR

This paper presents a novel fluid-structure interaction method using a shared NURBS-based spline interface, enabling precise geometry communication and flexible refinement in coupled analysis.

## Contribution

It introduces a coupled approach employing NURBS for both structural and fluid domains, facilitating direct transfer and independent refinement of interface quantities.

## Key findings

- Enables exact geometry representation at the interface
- Allows independent refinement of fluid and structural models
- Facilitates direct transfer of interface quantities

## Abstract

Engineering design via CAD software relies on Non-Uniform Rational B-Splines (NURBS) as a means for representing and communicating geometry. Therefore, in general, a NURBS description of a given design can be considered the exact description. The development of isogeometric methods has made the geometry available to analysis methods Hughes et al. (2005). Isogeometric analysis has been particularly successful in structural analysis; one reason being the wide-spread use of two-dimensional finite elements in this field. For fluid dynamics, where three-dimensional analysis is usually indispensable, isogeometric methods are more complicated, yet of course not impossible, to apply in a general fashion. This paper describes a method that enables the solution of fluid-structure interaction with a matching spline description of the interface. On the structural side, the spline is used in an isogeometric setting. On the fluid side, the same spline is used in the framework of a NURBS-enhanced finite element method (extension of Sevilla et al. (2011)). The coupling of the structural and the fluid solution is greatly facilitated by the common spline interface. The use of the identical spline representation for both sides permits a direct transfer of the necessary quantities, all the while still allowing an adjusted, individual refinement level for both sides.