  In this article, we present a one-field monolithic fictitious domain (FD)
method for simulation of general fluid-structure interactions (FSI). One-field
means only one velocity field is solved in the whole domain, based upon the use
of an appropriate L2 projection. Monolithic means the fluid and solid equations
are solved synchronously (rather than sequentially). We argue that the proposed
method has the same generality and robustness as FD methods with distributed
Lagrange multiplier (DLM) but is significantly more computationally efficient
(because of one-field) whilst being very straightforward to implement. The
method is described in detail, followed by the presentation of multiple
computational examples in order to validate it across a wide range of fluid and
solid parameters and interactions.
