The design of coupling algorithms for partitioned fluid-structure interaction (FSI) simulations are typically
validated on FSI problems involving large deformations of thin elastic structures with large added
mass ratios. A large number of FSI problems may however feature additional internal non-linearities,
examples of which include problems with free surface ow or FSI problems involving contact between
two or more solid bodies. In this paper we aim to demonstrate the applicability of quasi-Newton methods
when applied to these classes of problems. The analyses will focus on a comparison between two
promising families of quasi-Newton methods, namely the 'quasi-Newton least squares' (QN-LS) family
of methods and the 'multi-vector iteratively updated quasi-Newton' (MVQN) method. Both of these
families of quasi-Newton methods construct approximations of the FSI system Jacobians using only
iteratively obtained interface information, and can therefore be applied to black-box subdomain solvers.
We will further attempt to quantify the ability of these QN methods to adequately approximate
these additional non-linearities based on the form of the chosen interface equations.