Coupling between thermodynamics and self-organized pattern on the liquid anode of an atmospheric pressure DC glow discharge

In a discharge involving plasma-liquid interactions, many complex dynamics including thermal transfer, fluid mechanics, chemical reactions, and plasma physics are all coupled at the plasma-liquid interface. One of the more remarkable phenomena that occurs at the interface is the formation of the observed self-organized pattern that forms on a liquid anode of the air pressure DC glow discharge. The pattern apparently is coupled to prevailing interfacial processes and responds to discharge conditions by changing its shape and size. In an open system such as this nonequilibrium thermodynamics plays an important role in governing the heat and mass transport at the interface. The ohmic heating of discharge cause substantial water evaporation at interface and drive species transport and interactions through the pattern region. In the liquid phase, temperature gradients induce density variations and lead to the substantial convective flow and movement of the pattern. A highly localized hot spot may also give rise to the Marangoni effect which in turn may also effect the pattern shape.

In this work, the role of nonequilibrium thermodynamics and related heat, mass transport processes in self-organized pattern mechanism is examined. The interface temperature is manipulated by infrared laser and external cooling. The role of the introduction of water into the gas phase on pattern formation is explored in particular in the limit of zero water emission. Liquid motion is also monitored by particle image velocimetry.