Comprehensive measurements of the intermittency exponent in high Reynolds number turbulent flows

The intermittency exponent μ is determined from comprehensive measurements in the mixing layer ( R λ ≈ 2.0 × 10 3 ) and in the return channel ( R λ ≈ 3.2 × 10 3 ) of a large wind tunnel as well as in an atmospheric surface layer at R λ ≈ (3.3–12.7) × 10 3 . To estimate the value of μ and its dependence on R λ and the flow conditions, different methods of data processing are applied to the same data base, i.e., μ is defined by its scaling behaviour in the inertial range of centered and non-centered correlation functions and spectra of energy dissipation, second order moments of r and ln r , etc. (Here R λ is the Taylor microscale based Reynolds number, and r is the energy dissipation averaged over a segment of length r. ) It is found that these methods do not define a unique value of μ but a set of different scaling exponents, and these exponents stay systematically different over the range of flow conditions which was studied. No tendency for these exponents to collapse is observed up to R λ = 12.7 × 10 3 .