2nd moment closure model
 

Hi

I have a doubt in a terminology of 2nd moment closure model which is basically RSM model.

I am not quite sure why we call it 2nd moment closure. I have two guess here on the table :

1. the second equation of dissipation is needed for closing the exact transport equation ( like stress-w model of wilocox or whatever else....)

2. RSM is derived from second moment of the RANS equation, or on the word the RSM is being derived by writing the second equation of RANS and multiplying by a term and ... ( you know how to derive RSM from RANS right?)

Please clarify...