Learning Forum

[Luna Chen]

Hi everyone

I am currentlly simulate a compressor with a rotor inside and I use MRF method to let rotor rotate.

But I am comfusing about when drawing streamlines in cfd post in ansys, you can choose velocity or velocity in stn frame in the variable.

What is the difference between the two? Thank you so much!

[CFD_Friend]

Hi Luna,

• Velocity: This option shows the velocity of the fluid relative to the rotating frame of reference. In domains that are in the rotating frame (such as the region around the rotor), this velocity will account for the motion of the rotor. It essentially shows how the fluid is moving as seen from a viewpoint that is rotating with the rotor.

• Velocity in Stationary Frame: This option shows the velocity of the fluid relative to a stationary frame of reference. This is the absolute velocity of the fluid, which includes both the motion of the rotor and the fluid's movement due to other factors. It gives a view as if you were standing still outside the rotating system, observing the overall flow.

[Luna Chen]

Thank you!

So if I set the variable to "velocity," the color setting should correspond to "velocity."

Conversely, if I set the variable to "velocity of stationary frame," I should also set the color to "velocity of stationary frame" to obtain the correct and appropriate velocity distribution.

Is my understanding correct? Thank you again for your response!