  In this paper, a simple field function is presented for facilitating the
solution of complex and dynamic fluid-solid systems on Cartesian grids with
interface-resolved fluid-fluid, fluid-solid, and solid-solid interactions. For
a Cartesian-grid-discretized computational domain segmented by a set of solid
bodies, this field function explicitly tracks each subdomain with multiple
resolved interfacial node layers. As a result, the presented field function
enables low-memory-cost multidomain node mapping, efficient node remapping,
fast collision detection, and expedient surface force integration.
Implementation algorithms for the field function and its described
functionalities are also presented. Equipped with a deterministic multibody
collision model, numerical experiments involving fluid-solid systems with flow
conditions ranging from subsonic to supersonic states are conducted to validate
and illustrate the applicability of the proposed field function.
