Wave patterns of stationary gravity–capillary waves from a moving obstacle in a magnetic fluid

Abstract

The influence of a magnetic field on the pattern of stationary waves formed on the surface of a magnetic fluid (ferrofluid) when an obstacle moves has been studied both theoretically and experimentally. It is found that a vertical magnetic field narrows the cone of stationary waves and increases their amplitude. In the wake region, the peaks of the Rosensweig instability appear in a magnetic field that is smaller than the critical field that determines this instability occurrence. A horizontal magnetic field parallel to the obstacle velocity expands the cone of waves but reduces their amplitude up to the suppression of stationary waves. A horizontal field perpendicular to the obstacle velocity also expands the cone of waves and stabilizes their amplitude.

Does Magnetic Field Influence the Surface Tension of Ferrofluid?

“…The capillary wave pattern becomes more complicated in H ∥ , where λ increases with the capillary wave elongation along the force lines. This observation coincides with a theoretical prediction. , …”

“…This observation coincides with a theoretical prediction. 28,29 Figure 4a demonstrates that as the MF strength increases, the noise level of the capillary wave signal also increases. This illustrates the growing parasitic static deformation of the FF surface in a weakly nonuniform MF.…”

“…The free surface of the FF layer in the vertically oriented MF experiences Rosensweig instability when MF reaches the critical intensity value H cr . The onset of this instability takes place when the dimensionless parameter, Rosensweig number Ro , is defined as R o = 1 ρ g σ μ 0 M 2 1 + 1 / μ r μ s equals 2. The vacuum magnetic permeability (μ 0 ) is equal to 4π × 10 –7 H/m.…”