ENERGY AND FLATNESS SPECTRA IN A FORCED TURBULENCE

Statistical properties of a forced Navier-Stokes turbulence are studied numerically using a high-symmetric flow. A spectral simulation with resolution of 340(3) realizes the k-5/3 power law with Kolmogorov constant of 1.8 in the one-dimensional longitudinal and lateral spectra over one decade of wavenumber. The time-averaged micro-scale Reynolds number is 180. The normalized form of energy spectrum is the same as that for a previously reported freely-decaying turbulence (Kida and Murakami, Phys. Fluids 30 (1987) 2030) in both the inertial and dissipation ranges. The flatness factor of an individual Fourier component of velocity increases monotonically with wavenumber in the inertial range and saturates at about 3.7 in the dissipation range. The flatness factor of vorticity, on the other hand, is about 9. Such a big difference in the magnitude of flatness factor for a physical field quantity and its Fourier component is discussed with regard to the non-local interaction of Fourier components.