Learning Forum

[fz.erraghroughi]

Hello!

I want to modify the DRW model by changing the normal velocity fluctuations. I run the simulations by using the v²-f turbulence model, the next step is to import the obtained fluctuations by the v²-f model and implement it at the DRW based on the equation below: kmodified= 3v²/2 for y+ < 30

I need to create a UDF for that. I don't have any idea what macro should I use and also where exactly I can change the fluctuating velocities.

Any help!

Thank you!

Regards.

[Rob]

Having read through the theory I'm not sure it's even as easy as that! You might be better looking at not using the built in DRW but instead providing a body force to a particle based on the same maths taking data from v2f etc.

[fz.erraghroughi]

Thank you sir for the reply!
I really don't know where to begin, where to access the normal fluctuation velocities? is it in the time scale used in the DRW model? if yes which command I need to use?
sorry for my questions but I really feel stuck and I need help!
Regards.

[Rob]

Check the maths, do you need to infer them from the k and other terms? We're heading out of what we (staff) can cover on here so will need to rely on the wider community.

[sreekesh]

yes. Basically Random Walk Model calculate the instantaneous fluctuating velocity from RMS turbulent velocity fluctuations and Turbulent kinetic energy with use of a Gaussian random number with zero mean and unit variance.

[Shuvo Chowdhury]

Hello ! Did you get any solution? I am stuck at the same problem.