Surface waves on an oil film driven by corona-induction

The first demonstration of the creation of expanding circular waves an a precharged oil film spread over a flat dielectric surface used a triggering scheme of sudden grounding of the corona point. Wave initiation by the more general potential-switching method has been explored since. We introduce here a second independent experimental scheme of triggering which can be effective if pre-charging has been by a corona source and if charging level is sufficiently moderate: By switch-reducing the point potential far enough to cause corona-cessation first and then mechanically but impulsively lower the point tip near to the surface of the oil film, sudden wave initiation is invariably encountered in the process when the separation setting is below a threshold. As to the resulting surface characteristics, all essential observations resemble those associated with waves produced with the first scheme except that in a typical event expansion would ultimately cease after initial front propagation. Thus, temporal disturbance affects a maximum but finite size domain only. In this report, details from representative triggering results are presented