### 1.7.1. Alternate Rotation Model

By default, the advection term in the momentum equation models the relative frame velocity:

| (1–180)

The alternate rotation model modifies the advection and transient terms so they involve the absolute frame velocity, , rather than the relative frame velocity, .

The change of variable in the advection term requires a modification of the original Coriolis source term. The final form of the momentum equation becomes:

| (1–181)

Modeling details and recommendations on when this should be used are available in Alternate Rotation Model in the CFX-Solver Modeling Guide.

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