VORTICITY DETERMINATION, DISTRIBUTION, PARTITIONING AND THE HETEROGENEITY AND NONSTEADINESS OF NATURAL DEFORMATIONS

An investigation on vorticity in general heterogeneous and non-steady flows is presented. The bulk vorticity of a flow is solely determined by the imposed boundary conditions and it exerts no constraints on loc al flow. The distribution of bulk vorticity in different rheological d omains and the partitioning of the distributed vorticity into shear-in duced vorticity and spin are both time dependent. This indicates that heterogeneous flows are inevitably non-steady. In a quantitative examp le, it is demonstrated that even though the imposed boundary movement is a constant simple shear, local flow can be non-steady, spinning and non-coaxial. Super-simple shear flow with internal kinematic vorticit y number greater than 1 occurs, but the finite strain does not necessa rily pulsate. The geological implications of this investigation are di scussed. The significance of heterogeneity and non-steadiness in natur al deformations are emphasized. It is concluded that vorticity distrib ution and partitioning is the link between different scale structures. The internal kinematic vorticity number is not a criterion of finite strain oscillation.