  In a recent paper published in Physics of Fluids, Sanal Kumar et al. present
a model of transonic compressible flows based on ideal gas theory that is
irrelevant to biofluid flow and there are flaws in the general reasoning. In
addition, the experimental attempts do not show any evidence of supersonic flow
and do not provide any support for the flawed theory. In this Comment, I
discuss why this paper and other very similar ones by the same group of authors
and published in a short time frame (in Physics of Fluids and other journals)
should have been retracted.

Fluid Dynamics;Biological Physics