COMPREHENSIVE MEASUREMENTS OF THE INTERMITTENCY EXPONENT IN HIGH REYNOLDS-NUMBER TURBULENT FLOWS

The intermittency exponent mu is determined from comprehensive measure ments in the mixing layer (R(lambda)approximate to 2.0 x 10(3)) and in the return channel (R(lambda)approximate to 3.2 x 10(3)) of a large w ind tunnel as well as in an atmospheric surface layer at R(lambda)appr oximate to(3.3-12.7) x 10(3). To estimate the value of mu and its depe ndence on R-lambda and the flow conditions, different methods of data processing are applied to the same data base, i.e., mu is defined by i ts scaling behaviour in the inertial range of centered and non-centere d correlation functions and spectra of energy dissipation, second orde r moments of epsilon(r) and In epsilon(r), etc. (Here R-lambda is the Taylor microscale based Reynolds number, and epsilon(r) is the energy dissipation averaged over a segment of length r.) It is found that the se methods do not define a unique value of mu but a set of different s caling exponents, and these exponents stay systematically different ov er the range of flow conditions which was studied. No tendency for the se exponents to collapse observed up to R-lambda = 12.7 x 10(3).