Flow separation can lead to increased resistance and vibration generation, which is a difficult problem that cannot be ignored in engineering. In this paper, we propose a method of controlling flow separation by adsorbing ferrofluid onto the surface of a magnetized cylinder, taking the common flow around a cylinder as an example. Parametric effects of the ferrofluid film, including its viscosity and thickness, on the flow behavior were investigated in terms of the vortex shedding process, velocity distribution, dominant frequency, pressure distribution, and the flow motion inside the ferrofluid film. The results indicate that the ferrofluid film can suppress the generation of flow separation and achieve effective control, which is mainly caused by wall slip and the internal movement of the ferrofluid film. Furthermore, the flow separation control effect of ferrofluid thin films with different parameters varies, with low-viscosity ferrofluid exhibiting a superior control effect.
