### 4.4.2. ANSYS Interface Loads Plots

These plots show the convergence for each quantity that is part of the data exchanged between the CFX and ANSYS Solvers. There will always be two plots: ANSYS Interface Loads (Structural) and ANSYS Interface Loads (Thermal). The structural plot contains convergence information on forces and displacements, and the thermal plot contains information on temperature and heat flows/fluxes.

For each variable (each x-, y-, and z-component of the load is a separate variable), the convergence norm for the data transferred across the interface is given by:

| (4–1)

where represents the L2 norm of the transferred load, is the load component transferred at the last stagger iteration, is the load component transferred at this stagger iteration, and the sum is over all the individual load component values transferred (at different points in space). Each quantity is considered to be converged when , where is the convergence target for that quantity set in CFX-Pre (see Solver Controls, External Coupling Tab in the CFX-Solver Modeling Guide) or directly by the multi-field commands in the ANSYS input file (`MFCO` command).

Note: The definition of the convergence norm in Equation 4–1 was changed in Release 12.0. To achieve convergence in Release 12.0 (and later) that is similar to that achieved prior to Release 12.0, set the new convergence target to be the square root of the convergence target used prior to Release 12.0. Furthermore, the default value for the convergence target in Release 12.0 was changed to 0.01.

Convergence of each quantity transferred across the interface is reported as , where:

| (4–2)

and this is the quantity plotted on the ANSYS Interface plots. This implies that each quantity has converged when the reported convergence reaches a negative value. In general, the ANSYS Interface Loads (Structural) plot will contain six lines, corresponding to three force components (FX, FY, and FZ) and three displacements (UX, UY, and UZ), and the ANSYS Interface Loads (Thermal) plot will contain two lines (temperature and heat flow/flux). However, if the simulation is effectively 2D (only one element across), then forces and displacements in the third dimension are not exchanged and the corresponding lines will not be present.

The X axis of the plot corresponds to the cumulative number of stagger iterations (coupling iterations) and there are several of these for every timestep. A “spiky” plot is expected as the quantities will not be converged at the start of a timestep.

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