  We investigate the effect of an anisotropic substrate on the turbulent
dynamics of a simulated two dimensional active nematic. This is introduced as
an anisotropic friction and an effective anisotropic viscosity, with the
orientation of the anisotropy being defined by the substrate. In this system we
observe the emergence of global nematic order of topological defects that is
controlled by the degree of anisotropy in the viscosity and the magnitude of
the active stress. No global defect alignment is seen in passive liquid
crystals with anisotropic viscosity or friction confirming that ordering is
driven by the active stress. We then closely examine the active flow generated
by a single defect to show that the kinetic energy of the flow is orientation
dependent, resulting in a torque on the defect to align them with the
anisotropy in the substrate.
