EHD Induction Pumping in Annuli

EHD pumps will normally be enclosed in circular pipes, but previous analysis of such pumps was most often undertaken in two-dimensional geometries which cannot represent the curvature and finite size associated with a pipe. One practical version of an EHD induction pump includes an active travelling wave electrode running along the center of a grounded cylindrical pipe. Laminar flow which takes place in the annulus between pipe and electrode is modeled theoretially in terms of an induced charge layer situated at an arbitrary distance from the center electrode. If a hetero-charge layer is present, attraction pumping, in which the fluid follows the electric field wave, results. For a homo-charge layer, repulsion pumping occurs. Calculation of flow rates for various choices of electrical excitation and geometry are given as functions of voltage, frequency, and location of the charge layer. The attraction pump and the heavily loaded repulsion pump both give maximum flow rates at a single non-zero frequency, but the lightly loaded repulsion pump operates best at dc. The implications of these results are discussed in the context of several applications.