ON THE INTERMITTENCY FEATURE OF SHEAR-STRESS FLUCTUATION IN TURBULENCE

Instantaneous shear stress fluctuation is considered for different kin ds of flow fields and Reynolds numbers. These fluctuations consist of intermittent sharp spikes and small scale oscillations around the zero -crossing. We introduce the maximum norm to characterize them. This no rm is defined as a largest change within a box of finite size. The exp erimental results indicate that the maximum norm has a power law distr ibution in the inertial range. This distribution is independent of the flow field and the Reynolds number. Analogous to the locally averaged energy dissipation rate, the intermittency exponent mu is obtained fo r the maximum norm. Within experimental scatter, we find 0.1 less than or equal to mu less than or equal to 0.15. This value is a little sma ller than that for the energy dissipation field.