INTERMITTENCY AND SCALING PROPERTY OF BAND-PASS-FILTERED SIGNALS IN MODERATE-REYNOLDS-NUMBER TURBULENT FLOWS

The intermittency (multifractality) of turbulent velocity has been experimentally investigated through the frequency-band-pass-filtered velocity signals. In inertial range frequencies of the band-pass filter, the even number order moments of the signals show the scaling property on a nearly Gaussian distribution. The scaling exponents of the 2nth order moments are a nonlinear function of the order 2n. The nonlinearity means the frequency (scale) -dependent deviation of the statistics law of the signals are from Gaussian statistics. In dissipation range frequencies, the signals have no scaling property, and the deviation of the statistics law becomes much greater at higher frequencies. Such deviations of the statistics law are due to viscous effects, and reflect the breakdown of the self-similarity of turbulent velocity structure, that is to say its intermittent property.