Experimental observations of spontaneous breaking of reflectional symmetryin turbulent flow

A unique experimental facility along with unique methods of measurement of vorticity, helicity and related quantities were used in order to obtain the following main results. Strong experimental evidence in favour of the existence of the phenomenon o f spontaneous reflectional symmetry breaking (SRSB) in turbulent flows with initial and boundary conditions, which are nominally reflectionally symmet rical. In contrast to widespread expectation, this SRSB is exhibited not on ly in production of nonzero mean helicity, but in a number of more subtle e ffects related to spectrally and spatially localized SRSB. We observed qual itatively different cases of SRSB exhibited in large and small scales separ ately and concomitantly with helicity of different signs at different scale s and, in particular, cases with SRSB and vanishing mean helicity. Finally, in some cases the flow was almost perfectly reflectionally symmetrical, po ssessing an almost vanishing cospectrum. A surprisingly strong variability of this phenomenon was observed in contrast with 'conventional' characteris tics, which exhibited regular behaviour. On the basis of a large number of different results our conclusion is that the variability of parameters char acterizing SRSB is an intrinsic property at least of some turbulent flows.