Electrorotation of a viscous droplet in a uniform direct current electric field

We present a small-deformation theory which explains the experimentally observed nonaxisymmetric droplet deformation and orientation in a uniform DC electric field. The model shows that above a threshold electric field a rotational flow is induced about the droplet. As a result, drop shape becomes a general ellipsoid with major axis obliquely oriented to the applied field direction. The theory is in excellent agreement with the experimental data for high viscosity drops.