The eddy-diffusivity for a single particle in turbulent flow if defined as half the time derivative of the mean squared displacement measured from the origin. For the separating pairs, it is defined as half the time derivative of the mean squared separation between the two particles which are advected by the turbulent flow. I would like to characterize the rotational diffusivity of fibers or even for pairs of particles. What could be this definition? Any suggestions?
Hi Abdallah, nice question. But what is a rotational diffusivity? Are the fibers you mention finite, non-closed, or are these pieces? Possibly it helps if you give a more specific formulation. Sometimes also a picture may help.
Thanks Helmut for your answer! Here I mean fibers with finite size e.g. rods of a given length in the inertial range of turbulence. We may consider for example non-inertial fibers with densities similar to that of the surrounding fluid. I think that M. Shin and D. L. Koch, J. Fluid Mech. 540, 143 (2005) did a range of things re that topic. The same approach was used by S. Parsa and G, Voth in a recent PRL (2014). I would like to know about the physical meaning behind the rotational diffusivity of fibers in turbulent flow. Viele danke!!
- Badges
- Science topic