Turbulence%+Dh
 

hello, I found in many tutorials of fluent6.0(like elbow tutorial), in specifying turbulence boundary conditions that turbulence is modeled with INTENSITY % and hydraulic diameter the values of I% (often 10%)do not correspond with the definition of I%=(Rdh)^(-1/8) (etablished in user guide, modelling turbulence). and what exactly the hydraulic diameter. thanks

Re: Turbulence%+Dh
 

Ok, good question.

Turbulence intensity calculation procedure as outlined in the Fluent manual works well for internal duct flows. Usually for such flows, using 1 or 10 percent makes little difference as eventually, the value changes as the solution proceeds due to the viscous effects that result due to the presence of the wall.

This page provides a good explanation about the Hydraulic Diameter:

http://www.piping-toolbox.com/hydrau...er-18_458.html

Re: Turbulence%+Dh
 

ok PU1! how about the Reynolds number presented in the first part of the tutorial ( Re=50000)!! and the formula I%=f(Re)??

thanks for all

Re: Turbulence%+Dh
 

I'm not sure what exactly you are referring to, but even for a pipe elbow case, using 1 OR 5 or even 10% Turbulence Intensity should not influence the results for the same reason as I have given earlier in this thread.