  We investigate phase ordering dynamics of the incompressible Toner-Tu
equation in three dimensions. We show that the phase ordering proceeds via
defect merger events and the dynamics is controlled by the Reynolds number Re.
At low Re, the dynamics is similar to that of the Ginzburg-Landau equation. At
high Re, turbulence controls phase ordering. In particular, we observe a
forward energy cascade from the coarsening length scale to the dissipation
scale.
