### 13.1.1. Supported Capabilities and Limitations

ANSYS CFX supports the following capabilities when used in a System Coupling analysis:

- Force and displacement data transfers on wall boundaries:

  - Input of incremental displacements data from System Coupling allow moving and deforming mesh specification on boundary wall regions. Note that on the boundaries that move/deform, the option for the wall boundaries’ Mesh Motion needs to be System Coupling.

  - Output of force data on boundary wall regions. CFX is able to serve the total force variable (viscous and normal) on all wall boundaries (with or without moving/deforming boundaries). See Variables Available for System Coupling for details about the forces transferred from the wall boundaries.

- Thermal data transfers on wall boundaries:

  - Input of temperature data from System Coupling on all wall boundaries.

  - Output of EITHER

    - heat flow, OR

    - (for cases not involving radiation) heat transfer coefficient reference temperature plus heat transfer coefficient

    to System Coupling on all wall boundaries.

- Full support for local and distributed parallel solver execution.

- The convergence data for the continuity and momentum equations in CFX is shared with the System Coupling service at run time. The CFX equation residuals of a System Coupling simulation can be viewed using the Solution cell of the System Coupling component system. The CFX equation residuals in particular can also be viewed from the Solution cell of the CFX system.

  This data from CFX can be charted in conjunction with other data in the system coupling chart at all available intervals.

Note the following limitations when using CFX in a System Coupling analysis:

- For data transfers, only SI solution units and the global Cartesian coordinate frame are supported. CFX does not convert values if the data received uses a different unit system or any local coordinate frames.

- Monitor point data is not shared with System Coupling but can be seen from CFX-Solver Manager.

- Data transfer regions can only be on wall boundaries that are not on solid or porous domains solved by CFX.

- Multi-configuration cases are not supported, including cases that involve remeshing during an analysis.

- A CFX system that models radiation can only send heat flow data; it cannot send heat transfer coefficient reference temperature and heat transfer coefficient data.

- An immersed boundary cannot be used as a System Coupling interface boundary.

- The rigid body solver is not supported.

- When using thin surfaces/baffles in CFX as System Coupling interfaces, you need to create a separate wall boundary condition for each side of the thin surface. These are paired with two sets of shell elements in ANSYS Mechanical. For more information, see Coupling with Wall/Wall-Shadow Pairs or Thin Surfaces in the ANSYS Mechanical User's Guide.

- Particle forces do not contribute to the force passed to System Coupling on a wall boundary.

- The CFX-Solver log is not viewable from the System Coupling system.

- CFX-Pre-specific errors do not cause a message box to appear in Workbench or in CFX-Pre. However, such errors are reported in the CFX system’s Setup cell properties when the cell is marked “Needs input”.

- If the maximum elapsed time (wall clock time) is specified (from CFX), it will be ignored.

- You cannot interrupt a run from the CFX system. However, you can from the System Coupling system.

- You cannot start a new System Coupling simulation if the CFX portion of the simulation is initialized with results from a transient, non-System Coupling, CFX case involving a Theta shift (for example, a transient rotor stator case). It is a requirement that new cases are initialized without the Continue History From option; however, for CFX cases involving a Theta shift, the interpolation process does not reset the simulation time, which would be required to begin a new case.

- For one-way System Coupling where CFX sends heat flow or heat transfer coefficient reference temperature plus heat transfer coefficient, the temperature on the FSI interface might not be set properly.

- The bulk heat transfer coefficient reference temperature and heat transfer coefficient data generated for a System Coupling interface in a multiphase case are not available for callbacks or User Fortran; this data is only used by the System Coupling system.

Release 18.2 - © ANSYS, Inc. All rights reserved.