Ansys Fluent to Mechanical via System Coupling: Choosing Data Mapping for Non-Matching Interface Meshes

A two-way FSI model is being planned in which Ansys Fluent sends pressure and thermal loads to Ansys Mechanical and receives displacement back, with System Coupling managing the exchange at the shared interface. The fluid and structural side meshes do not match node-for-node, so every transferred field is interpolated by System Coupling's mapping.

The documented mapping options trade local smoothness against conservation of total force or heat flux, and Ansys Help describes the choices without giving a universal selection rule. On a poorly matched interface, mapping can leave pressure patches or over-smoothed deformation that still passes the coupling tolerance. Options and supported participants also vary by release; the assumption here is a recent version (2023 R1 or newer) offering both Workbench wiring and a standalone System Coupling setup, to be confirmed against that release's System Coupling Guide.

Open decisions:

1. For pressure transfer onto a finer structural mesh, is conservative mapping the defensible default, and which artifacts — load patching or flattened displacement — signal the choice should be revisited?
2. Besides the data-change tolerance, should convergence also be judged on stabilized integrated quantities such as total interface force?
3. When deflections are expected to stay small, is one-way transfer acceptable, or should under-relaxed two-way coupling be the starting point whenever added-mass effects are plausible?