Two- and three-dimensional instabilities of the cylinder wake in an aligned magnetic field

Two- and three-dimensional (2-D and 3-D) instabilities in the wake of a circular cylinder placed in an electrically conducting fluid and subjected to a constant magnetic field aligned with the freestream are investigated numerically. Increasing magnetic fields suppress 2-D instability (vortex shedding), whereas 3-D instabilities are influenced in a more complex way. In the presence of a magnetic field, 3-D instability has been detected below the 2-D stability threshold. This can lead to a reversal of the order of instabilities, i.e., 3-D instability appears at lower Re than 2-D instability.