The interpretation of electrohydrodynamic mobility under unipolar injection in dielectric liquids

The EHD (Electrohydrodynamic) mobility with unipolar injection in the transient regime has been investigated theoretically in terms of the EHD interfacial instability. A new expression of the transient EHD mobility is given by considering the dynamics of the interface between the space charge layer in front of the injecting electrode and the bulk of the dielectric liquid. It is shown that the EHD mobility depends on not only the (∈/ρ)^1/2, but also on the characteristics of the interface and electrode separation. The dynamics of the space charge/liquid interface plays a very important role in the conduction process, especially in the dielectric liquids in which the ion `injection´ is the predominant mechanism of providing charge carriers. The type of instability proposed leads directly to the observed EHD delay time, mobility, and fine filamentary structure of the transient electroconvection which has been observed experimentally