  Direct numerical simulations (DNS) of microscale fluid-structure interactions
(mFSI) in multicomponent multiphase flows pose many challenges such as the
thermodynamic consistency of multiphysics couplings, the tracking of moving
interfaces, and the dynamics of moving triple-phase contact lines. We propose
and validate a generic DNS approach: Diffuse-Resistance-Domain (DRD). It
overcomes the above challenges by employing Onsager's principle to formulate
dynamic models and combining traditional diffuse-interface models for
fluid-fluid interfacial dynamics with a novel implementation of complex
fluid-solid interfacial conditions via smooth interpolations of
dynamic-resistance coefficients across interfaces. After careful validation by
benchmark simulations, we simulated three challenging mFSI problems taken from
different fields.
