Hi all,

Where can I get some information on how to set up an isotropic and homogenous turbulence field? I want to know the theory and the coding/method of implentation. A well commented code would suffice. Preferably I want a good CFD based explaination of the theory. Does anyone have any online references?

Thanks.

Hi, cool joe:

I think you have to run a code for 3D N-S equations. You can give a random field as an initial condition for the simulation. During the simulation, monitor the energy spectrum or the total energy as a function of time. When you observe a k^{-5/3} spectrum, then you have an isotropic homogenenous field. Hope it helps -Jenn

Hi,

The mostly used method for the simulation of isotropic turbulence is the pseudo-spectral method. I don't think you will find much detailed online information, but there are some books available about spectral methods, see this site. Some people have also used finite difference methods for isotropic turbulence. This technique is a bit more simple than pseudo-spectral but not as accurate. I think Orlandi wrote a book about it (can't remember the title). Perhaps it even contains a complete code for isotropic turbulence on a CD.

/Tom

Hi,

Thank you both for your help., What I am looking for is a code to create an isotropic and homogenous field which I can then use in a standard finite difference N-S code. All I want to know is how to create such a field. What are the mathematics of it. Thanks again!

"Numerical Experiments in homogeneous turbulence" by Robert S. Rogallo, NASA Tchnical Memorandom 81315.

He explains how to create an initial condition: "The fourier transform of the velocity field is initialized to an isotropic state, satisfying continuity, and having a given energy spectrum."