Modifications to the wake of a wire across Poiseuille flow due to a unipolar space charge

Abstract

A wake behind a wire in a developed Poiseuille flow is examined with and without ionic injection into the liquid by the wire. Mean electric fields of up to 50 kV/cm between the wire and two plate electrodes on either side were used to bring about this injection. The resulting Coulomb force can modify the wake flow in two ways. When this force is weak, the injected ions are transported downstream in a thin charged wake, the only effect being that the deficit velocity is compensated over shorter distances. Once the Coulomb force is strong, there are two charged and turbulent plume-like structures going from the wire to the plates. These are perpendicular to the plates for zero forced flow and are pushed downstream to smaller angles as the forced flow is increased. The wake in this case is not present. Different experimental laws are given to characterize the different regimes and the transition between them.