Geometric properties of the patterns observed in low conducting liquids under corona discharge

We describe an experimental investigation of the different patterns that appear in thin liquid layers subjected to strong electric fields and a corona discharge. The study is motivated by recent observations [F. Vega Reyes, F.J. García, Pattern imaging of primary and secondary instabilities, J. Fluid Mech. 549 (2006) 61–69] of important disparities that appear in the behaviour of these patterns in liquids with different properties. Two main groups of long-wave hydrodynamic instabilities were detected in this system: primary and secondary instabilities. We present the first statistics of the geometric forms of the patterns cells, as a function of the properties of liquids. We also show that the primary instability may be divided into two subgroups, having different pattern characteristic geometries.