Velocity Intermittency in a Buoyancy Subrange in a Two-Dimensional Soap Film Convection Experiment

In a two-dimensional soap film convection experiment, the velocity fields are found to be strongly intermittent in the buoyancy subrange, which was reported to be nonintermittent in a recent numerical simulation. The structure functions Sq(l)(=⟨|δvₗ|q⟩) exhibit self-similar structures and can be described by power laws l^ζq for integers 8≥q≥1. By extending Kolmogorov's refined similarity hypothesis to our system, an analytical form is derived for the scaling exponent ζq=q/2+(μ/18)(3q-q²). Our measurements yield μ=0.42, which is significantly greater than 0.2 found in high Reynolds number turbulence in wind tunnels.