Hello Fuyu-m
The Help Document for Discovery Live suggests that the input for Swirl inlet is given as 'Velocity Components', a normal and a radial component. (Refer Image below).
So the 'Speed' here is actually Velocity and the negative sign should imply the direction.
Although thank you for pointing out the wrong terminology. I will inform the developers to make the correction in the upcoming versions.
You are navigating away from the AIS Discovery experience