 ## Fluids

#### Calculate forces and moments in absolute system for a transient turbomachinery run in ANSYS CFX

• admin
Ansys Employee

A: In ANSYS CFX, during transient rotor-stator runs, the meshes of rotating frames remain stationary, but the relative position of the flow profiles at the 2 sides of a transient rotor-stator interface is updated each time step. The forces and moments which are calculated with expressions like forcex() or torquex() are therefore calculated in the relative frame of the rotating parts. To get the forces and moments in absolute frame, a coordinate transformation is needed. If for instance the Z axis is the axis of rotation, the forces in X and Y direction ca be expressed as: myForceXabs = forcex()@Impeller * cos(Angular Velocity * Time) + forcey()@Impeller * sin(Angular Velocity * Time) myForceXabs = -1 * forcex()@Impeller * sin(Angular Velocity * Time) + forcey()@Impeller * cos(Angular Velocity * Time) Similarly, moments in absolute frame can be transformed in the same way.

• admin
Ansys Employee

Q: How to calculate forces and moments in absolute system for a transient turbomachinery run ANSYS CFX, during the solver run? 