Controlling flow separation around tandem circular cylinders using transverse magnetic field

An externally imposed transverse magnetic field, due to its damping nature, can control the flow separation around an object. Consequently, an inherently unsteady (or steady separated) flow around a bluff body may be transformed into a steady separated (or attached) flow pattern when an externally imposed magnetic field acts throughout the fluid domain transversely. When a pair of cylinders is arranged in tandem in an unconfined medium, the interference effect may contribute further instability to the resulting flow in comparison to a single cylinder case. This work reports how a transverse magnetic field influences the flow around a pair of tandem circular cylinders placed with varying gap spacing within an unconfined and electrically conducting fluid medium. A finite volume based numerical computation technique is adopted to study the magneto-fluidic phenomena. The flow Reynolds number lies in the range 10 ≤ Re ≤ 40. Additionally, computations are also performed at a relatively higher Reynolds number, Re = 100. The non-dimensional gap between the cylinders is varied as 0.7–5.0 and the magnetic field strength (Hartmann number) is kept in the range 0–5. The flow patterns are steady separated at 10 ≤ Re ≤ 40 and unsteady with vortex shedding at Re = 100. The critical magnetic field strength at which the steady separated (and the unsteady) flow around the cylinders transformed into an attached (and steady separated) flow is obtained for the range of Reynolds number and gap spacing. With increasing Reynolds number, the critical magnetic field strength increases, while it decreases with increasing gap spacing. The observations are substantiated through visual inspection of the streamline profiles around the cylinders for varying Reynolds number and gap spacing.