  In this letter we point out some interpretational difficulties associated
with concepts from General Relativity in a recent article which appeared in J.
Fluid Mech. 731 (2013) R4 where a Lorentzian metric was defined for turbulent
fluid flow and interpreted as being analogous to a black hole metric. We show
that the similarity with black hole geometry is superficial at best while
clarifying the nature of the black hole geometry and the work above with some
examples.
