Decay of vorticity in homogeneous turbulence

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 ω follows the behavior expected of a classical fluid with ω∼${\mathit{t}}^{\mathrm{-}3/2}$, consistent with the notion of a coupled turbulent state of helium II. This technique also yields the time dependence of the Kolmogorov microscale.