### 36.6.1. Type

The frame change interfaces model the interface between a rotating assembly and a stationary assembly. For details, see Frame Change/Mixing Model in the CFX-Solver Modeling Guide. When the analysis type is steady state, four options are available to model frame change:

- `None`

- `Stage`: For details, see Stage (Mixing Plane) in the CFX-Solver Modeling Guide.

- `Periodic`

- `Frozen Rotor`: For details, see Frozen Rotor in the CFX-Solver Modeling Guide.

For transient or Transient Blade Row simulations, the following four options are available to model frame change:

- `None`

- `Stage`: For details, see Stage (Mixing Plane) in the CFX-Solver Modeling Guide.

- `Periodic`

- `Transient Rotor-Stator`: For details, see Transient Rotor-Stator in the CFX-Solver Modeling Guide.

In addition, a frame change interface of type `None` is created for tip clearance regions and disconnected regions of mesh within a component (for example between an inlet section and a blade section). Periodic interfaces are used in regions where a portion of the flow field is repeated in many identical regions. The flow around a single turbine blade in a rotating machine, or around a single louvre in a whole array in a heat exchanger fin are such examples.

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