[me3840]

Hello all,

I'm working on some LES and as most know I'd like to get the ratio of TKE from the resolved velocity field to the total TKE.

Right now there exists a functionObject for generating the TKE for the SGS at any instant in time (I believe) through the turbulenceFields functionObject.

However to get the ratio, I would need the average SGS TKE. Since this field is only written to disk every so often and not stored by the solver during iteration, it's not so easy to get an average without massive storage requirements.

It appears others have modified the solver to compute it at runtime, seen here:
Smagorinsky LES: output and average k value

However this post is a bit old and I was just wondering if this is still a viable method. Is there a newer functionObject which will allow the storage of any field in memory at runtime, or must the solver be modified to allow this?

[agustinvo]

Hello

taking a look onto your problem, I suggest you three things:

1. Modify the solver, where you call kSgs and you define your TKE
2. Use swak4Foam, and add the functionObject expressionField
3. Modify the turbulenceFields functionObject, so you call kSgs from your turbulence model, and TKE, and you write the expression you're looking for

About the massive storage, you can select to have an output of these turbulence fields each outputTime, and not each timeStep.

[me3840]

Just to follow up, I figured this out. No modifications to the solver or use of swak4Foam is needed.


You just have to add the functionObject you want to your control dictionary before the fieldAverage. Then fieldAverage will pick it up without issue.