How to compute turbulent length scale in ANSYS Fluent

vanKey · June 24, 2023, 10:29

Hello all,

does anyone know how to compute the turbulent length scale in ANSYS Fluent?

Kind regards
vanKey

LuckyTran · June 25, 2023, 02:48

In what context? What are you trying to do? And to what scope?

As an input boundary condition for RANS? If so, what model?

Or how to calculate it from detailed flow data such as DNS?

vanKey · June 25, 2023, 09:28

I want to estimate the turbulent properties on the inlets of a CFD simulation.
I've made a RANS-Simulation for an aeroacoustic problem and I want to calculate the turbulence length scale for this simulation. It is a fan in a duct.

LuckyTran · June 25, 2023, 12:02

Since you actually have a duct... Fluent has an intensity and hydraulic diameter option. You should use it. If you want to understand the theory of what it does you can read the wiki article on tke. Basically, it's 0.068Dh

But in actuality, what you are providing at inlets is k and epsilon (or k and omega).

June 24, 2023, 10:29	How to compute turbulent length scale in ANSYS Fluent	#1
vanKey New Member Join Date: May 2023 Posts: 4 Rep Power: 3	Hello all, does anyone know how to compute the turbulent length scale in ANSYS Fluent? Kind regards vanKey

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June 25, 2023, 02:48		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	In what context? What are you trying to do? And to what scope? As an input boundary condition for RANS? If so, what model? Or how to calculate it from detailed flow data such as DNS?

June 25, 2023, 09:28		#3
vanKey New Member Join Date: May 2023 Posts: 4 Rep Power: 3	I want to estimate the turbulent properties on the inlets of a CFD simulation. I've made a RANS-Simulation for an aeroacoustic problem and I want to calculate the turbulence length scale for this simulation. It is a fan in a duct.

June 25, 2023, 12:02		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	Since you actually have a duct... Fluent has an intensity and hydraulic diameter option. You should use it. If you want to understand the theory of what it does you can read the wiki article on tke. Basically, it's 0.068Dh But in actuality, what you are providing at inlets is k and epsilon (or k and omega).