Rotating Motion of an Oil Droplet in a Circular Channel Subjected to a Transverse Alternating Electric Field

The transient behavior of a silicone oil droplet passing through a circular channel in which castor oil passes as a surrounding fluid is investigated in both a periodically intermittent alternating electric field and a sinusoidal alternating electric field. When a periodically intermittent electric field with a low frequency and medium strength is applied, the droplet first undergoes ellipsoidal deformation where the major axis is oriented in the direction between the electric field direction and the direction normal to the electric field and electrorotation occurs. The inclined major axis tilts away from the electric field direction and then approaches it. For the case where a sinusoidal alternating electric field with medium strength is applied, electrorotation occurs when the frequency of the alternating sinusoidal electric field is low, whereas the droplet periodically deforms between a prolate and an oblate ellipsoid at certain frequencies. When the frequency of the electric field applied is high, the droplet remains spherical or undergoes deformation to a quasi-steady prolate ellipsoid with an aspect ratio of almost unity.