Measuring nonextensitivity parameters in a turbulent Couette-Taylor flow.

We investigate probability density functions of velocity differences at different distances r measured in a Couette-Taylor flow for a range of Reynolds numbers Re. There is good agreement with the predictions of a theoretical model based on nonextensive statistical mechanics (where the entropies are nonadditive for independent subsystems). We extract the scale-dependent nonextensitivity parameter q(r,Re) from the laboratory data.