  This paper addresses the interaction of initially anti-parallel vortex tubes
containing an axial flow that induces a twisting of the vortex lines around the
tube axes, using numerical simulations. Vortex tube configurations with both
the same and opposite senses of twist -- corresponding to same and opposite
signs of kinetic helicity density -- are considered. It is found that the
topology of the reconnection process is very different between the two cases.
For tubes with the same sense of twist, the reconnection is fully
three-dimensional (3D): vortex lines reconnect at a finite angle, and 3D vortex
null points may be created. Following reconnection the vortex line topology in
both bridge and thread structures exhibits a high degree of complexity. For
oppositely-twisted tubes the reconnection is locally two-dimensional, occurring
along vorticity null lines, that in contrast to the untwisted case are not
perpendicular to the tube axes. This leads to a break in the symmetry between
the two vortex bridges generated during reconnection. For all cases studied,
increasing the twist in the vortex tubes leads to a later, faster, and more
complete reconnection process.
