Intermittency effects in a numerical simulation of stationary three-dimensional turbulence

Abstract

A Navier-Stokes direct spectral simulation code was modified to produce stationary and nearly isotropic turbulence in three dimensions. An approximate $-\frac{5}{3}$ energy spectrum was maintained over the entire range of wavenumbers by simultaneously driving the fluid and supplementing the ordinary viscosity with a subgrid-like energy sink in the last 15% of the spectrum. Half-tone and contour plots of the fluctuations in the vorticity, rate-of-strain tensor and helicity show increasing ‘spottiness’ as the system evolves in time. Probability distributions and cross-correlations among these three quantities were also obtained. The flatness factor of the longitudinal velocity derivative, the longitudinal structure functions and the fluctuations in the locally averaged dissipation rate are consistent with some degree of intermittency, but do not unambiguously demonstrate its presence in the simulated flows.