HELICITY TRANSFER IN TURBULENT MODELS

Helicity transfer in a shell model of turbulence is investigated. We s how that a Reynolds-independent helicity flux is present in the model when the large scale forcing breaks inversion symmetry. The equivalent in shell models of the ''2/15 law,'' obtained from helicity conservat ion in Navier-Stokes equations, is derived and tested. The odd part of the helicity flux statistics is found to be dominated by a few very i ntense events. In a particular model, we calculate analytically leadin g and subleading contributions to the scaling of triple velocity corre lation.