Session MB - Drops I. Emulsions & Drops.
MIXED session, Tuesday afternoon, November 23
Grand II, Westin Seattle
The deformation and settling velocity of a translating dielectric liquid drop in a uniform electric field are investigated theoretically at low Reynolds number. Perturbation methods are employed for shape distortion and charge convection respectively, and the settling velocity is calculated by combining the corrections from the two contributions linearly at the lowest order. The result for the settling velocity reads U_S=U_H(1+C_1*aE^2+C_2*E^2), where U_H is the Hadamard-Rybczynski velocity. C_1 and C_2 are dimensional coefficients describing the effects of shape distortion and charge convection respectively. Here a is the drop radius and E the electric field gradient. For most fluid pairs in the experimental papers by Torza et al.(1971) and Vizika amp; Saville(1992), the coefficients C_1 and C_2 have opposite sign, which indicates the existence of critical drop radius determining whether the settling velocity is greater or less than U_H. The radius is typically small, in the range of 10^-9 to 10^-3 m. Experimental attempts to verify its existence are described.