Four-fifths laws in incompressible and magnetized fluids: Helicity, Energy and Cross-helicity

In this paper, we are concerned with the Kolmogorov’s scaling laws of conserved quantities. By means of Eyink’s longitudinal structure functions and the analysis of interaction of different physical quantities, we extend celebrated four-fifths laws from energy to helicity in incompressible fluid and, energy and cross-helicity in magnetohydrodynamic flow. In contrast to pervious 4/5 laws of energy and cross-helicity in magnetized fluids obtained by Politano and Pouquet, they are in terms of the mixed three-order structure functions rather than the structure coupling correlation functions.