What is the effect of turbulence intensity
 

Hey I am beginner with modeling turbulence by fluent I need to ask : can anybody tell me exactly the effect of turbulence intensity at inlet or outlet boundary conditions on the flow variables like velocity , pressure , volume fraction…etc?

Thank you for your answer

Re: What is the effect of turbulence intensity
 

high ti at inlet will define instability of medium at entry changing heat transfer at surfaces for example or lift drag. TI value at exits is only for situations where backflow occurrs

Re: What is the effect of turbulence intensity
 

thanks for the reply. did you mean by stability it effects the occurring of fully developed flow region for pipe flow? should I keep its value at inlet same as outlet? is it have the same effect for the case of iso-thermal flow?

Thanks again

Re: What is the effect of turbulence intensity
 

TI at inlet can be thought of giving some idea about fluctuation in the flow at inlet. lower the fluctuation in velocity lower the inlet TI. We dont have any measure to know the Turbulence intensity, it comes just from guess and experience. Coming to the querry whether to keep the backflow calculations Intensity at Outlet as same as inlet. well if you have a pipe without any ribs/dimples/ etc which can cause intensity to increase during the flow-path then you may apply same, but if your domain is not that smooth then apply based upon your judgement. I can give one example, I had a rib-roughened rectangular channel at the inlet of which the flow was quite normal (Re 30000, TI 5%) but when the flow encountered ribs, intensity shooted up like anything (which was well expected) it went upto 125%. I had the ribs till very near to exit. Now based upon seeing this I can not apply TI at outlet as 5%, It should be somewhere near to 100 or 125% not 5%. Hope this shades some light! Jha