What is turbulence flux relating to EBC's?

Hi,

I am trying to prescribe an inlet turbulence intensity for flow past a square cylinder. I believe that This can be accomplished using an essential boundary condition; however, I need to know more details. 

How is turbulence diffusion flux defined in AcuSolve? It would be great to get a detailed understanding of this option.

Here it's used in hwcfd,

Here is what I was able to find in the documentation for hwcfd

Thanks,

Peter Parrish