Intermittency in 2D Turbulence

The existence of intermittency in three-dimensional turbulence is generally accepted, although with a variety of interpretations. However, the issue of intermittency in two- dimensional turbulence is unresolved. By measuring the velocity in a flowing soap film, we show that there is significant intermittency in both the enstrophy and energy cascades. The intermittency is characterized by the scaling exponents of velocity structure functions $S_n(r)$ as well as the flatness $F$ of velocity derivatives. Both show a strong Reynolds number dependence. However, unlike turbulence in three dimensions, the intermittency decreases with increasing Reynolds number. This work is supported by NSF grant No. 1044105, a Mellon fellowship, and the Okinawa Institute of Science and Technology.