The topology of surface skin friction and vorticity fields in wall-bounded flows

Abstract

In previous studies, the three invariants of the velocity gradient tensor have been used to study turbulent flow structures. For incompressible flow the first invariant P is zero and the topology of the flow structures can be investigated in terms of the second and third invariants, Q and R respectively. However, these invariants are zero at a no slip wall and can no longer be used to identify and study structures at the surface in a wall-bounded flow. At the wall, the flow field can be described by a no slip Taylor-series expansion. Like the velocity gradient tensor, it is possible to define the invariants P, Q and R of the no slip tensor. In this paper it will be shown how the topology of ..