Decay of vorticity in homogeneous turbulence

Abstract

We report on observations of turbulent behavior made without requiring the use of Taylor's ``frozen turbulence'' hypothesis. Initially, a towed grid generates homogeneous turbulence of grid Reynolds number of order ${10}^{5}$ within a stationary channel filled with helium II. The subsequent decay in time t of the line density of quantum vortices is measured by second sound attenuation, and the associated rms vorticity \ensuremath{\omega} follows the behavior expected of a classical fluid with \ensuremath{\omega}\ensuremath{\sim}${\mathit{t}}^{\mathrm{\ensuremath{-}}3/2}$, consistent with the notion of a coupled turbulent state of helium II. This technique also yields the time dependence of the Kolmogorov microscale.