By default, the advection term in the momentum equation models the relative frame velocity. Assuming constant angular velocity for simplicity here, the advection term is as follows:

(1–184)

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:

(1–185)

Note that Equation 1–185 does not carry the assumption of constant angular velocity.

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