Thrust of Jet Fan

[Réda]

Hello everyone,

 

I want to thank all of you for the effort for developing FDS 6.

 

My question is concerning about jet fans, few months ago i used to caracterize jet fans by the velocity/volume flow on FDS, I did many test triyng to verify the induced pressure by the thrust of the jet fan, the results we got are higher than we expected, the questions we had:

 - If the square geometry of the jet fan in fds change the behaviours of the air ? 

 - How the constructor of jet fans verify velocity/volume Flow ?

 

 but during a meeting with a constructor of Jet Fans, it appears that the only parameter which is verified experimentaly is the "THRUST" of the fan in free field. The velocity and the volume flow are "just" theoric.

 

I was curious to know if there is any research about characterizing the jet fan by its thrust ?

 

Thank you for your help

 

Reda

[dr_jfloyd]

As long as you know where the thrust is characterized (so you know the flow area), then there is only one velocity that will give that thrust.  Thrust is mass flow rate times velocity and mass flow rate is volume flow times density. Volume flow is velocity times area.  In this case density is the same (assuming the fan is tested at ambient conditions) and area is given by where the thrust is determined leaving only velocity as a variable.

[Réda]

Dr Floyd,

 

Thank for your answer, and I understand what you said.

I would like to know if you have an idea why there is an overestimation of induced pressure by the thrust of jet fans in FDS?

does it come from the pressure loss inside the jet fan which are not taking in count in FDS ?