Comment on "Linear stability of a rotating channel flow subjected to a static magnetic field" [Phys. Fluids 34, 054116 (2022)]

TL;DR

This paper critiques a recent linear stability analysis of rotating magnetohydrodynamic channel flow, identifying a fundamental error in the magnetic field formulation that renders the original results unphysical.

Contribution

It highlights a critical mistake in the previous study's magnetic field formulation, emphasizing the importance of electric potential in charge conservation.

Findings

Original results are unphysical due to the error.

Electric potential contribution is essential for correct MHD stability analysis.

Correct formulation alters the stability characteristics of the flow.

Abstract

Recently, Sengupta and Ghosh [Phys. Fluids 34, 054116, (2022)] published a linear stability analysis of a pressure-driven channel flow which is subject to rotation around a spanwise axis and a uniform magnetic field applied in the same direction. Unfortunately, the formulation of the magnetohydrodynamic part of the problem contains an elementary error which makes the obtained results unphysical. The error is due to unfounded omission of the electric potential contribution in the induced electric current which, thus, does not satisfy the charge conservation.