Expression for drag coefficient in CFX-Pre
 

Hi,

I am trying to write expression for particle drag coefficient in CFX-Pre but it's giving me error. I used the variable ptre from Ansys reference guide but it is not recognising. I am pasting here the expression

=24/ptre*((1+8.1716*exp(0.9350))*ptre^0.2243)+((73.69* ptre*exp(1.1672))/(ptre+5.378*exp(1.4288)))

Can anyone suggest how can I make the upper expression up and running in CFX-Pre?

Thanks in Advance.