[Jeoa]

Hello,

I am currently running a CFD project in which I have to model a small fan. I was thinking of using the 3D fan zone cell condition. Not much information is available about it... I was wondering why the tangential source term was defined as follows:

S_t = ( 2*W_fan*r ) / ( c_1*Omega )

where W_fan is the fan power,
r the local radial distance from the fan axis
Omega the fan operating angular velocity
And c_1 an L^5 dimension term.

This information is available in more details in the user guide in section 7.2.4. 3D fan zones, that I have attached.

The user guide states that this equation is derived from a turbomachinery relation. I would like to know which one it is.

It sounds completely counter intuitive that the angular velocity is inversely proportional to the source term.

Why is it that a very low RPM case outputs higher tangential velocities in the fan compared than a high RPM case?

Thanks for your attention,
Jean