The purpose with this experiment is to study relative diffusion in a two-dimensional turbulent fluid. It is set up as a gravity driven channel with a grid. I look at the flow up to twenty times the grid size downstream from the grid.

Studying two-dimensional phenomena in a three-dimensional world is not really possible. But if we limit the impact of the effects that arise from the fact that our world is three-dimensional, we will get a good approximation of a two-dimensional system.

If we look at the "real world" (the one *outside* the lab :-), both the
atmosphere and the oceans shows a two-dimensional behaviour due to the large
ratio of the horizontal to the vertical extent.

Descriptions of other experiments where soap films are used as an approximation to two-dimensional fluids can be found in [9, , ].

sparre@cats.nbi.dk