Interaction of a biased cylinder with a flowing dusty plasma

Abstract

Experimental observations of supersonically flowing dusty plasmas and their interaction with an electrically biased circular cylinder are presented. Two methods for producing flowing dusty plasmas are described. The dusty plasma is produced in a DC anode glow discharge plasma. In Configuration I, a secondary dust cloud, initially formed near a biased grid, flowed away from the grid at supersonic speeds when the grid voltage was suddenly changed. In Configuration II, a pencillike dust beam was produced using a nozzle-like (converging-diverging) electrostatic potential structure. Using Configuration I, the streaming dust encountered a biased cylinder (wire) whose axis was oriented transverse to the dust flow. The flowing dust particles were repelled by the electrostatic field of the negatively charged cylinder, and a dust void was formed around the cylinder. A detached electrohydrodynamic bow shock, akin to the Earth's magnetohydrodynamic bow shock, was formed on the upstream side of the cylinder, while an extended teardrop-shaped wake region was formed on the downstream side. Video imaging of the dust stream allowed for observations of the structure and evolution of the bow shock. Configuration II was used to produce a narrow beam of dust particles and observe how the beam was deflected around the biased cylinder. Three multimedia files (movies) of the observed phenomena are provided in the online Supplementary material.

Vortex Dynamics in Dusty Plasma Flow Past a Dust Void

“…What they observed was a bow shock in front of it [30]. In the very next year itself (2013), Meyer et al also did a similar experiment with a different configuration and dust flow mechanism (velocity $ 10-25 cms À1 ) than Saitou's [21]. They produced a dust void by placing a 0.5-mm-diameter cylindrical wire transverse to the flow.…”

“…Self-generated vortices have been observed in many dusty plasma experiments, which have been dealt with significant attention. The main cause of such vortex formation is the nonzero curl of the various forces acting on the electrically charged dust particles that are commonly found in radiofrequency (RF) discharges, microgravity conditions and subsonic dusty plasma flow with low Reynolds numbers [20,21]. The nonzero component of the curl induces a rotational motion to the charged dust particles, which leads to the formation of the vortices.…”

Experiment and model for a Stokes layer in a strongly coupled dusty plasma

“…Flows of particles in a dusty plasma can be created by applying several kinds of forces. These include the Coulomb force [40][41][42][43], drag from a flowing gas [44][45][46][47][48], gravity [49], and the radiation pressure force applied by a laser beam [50,51]. The latter force is used in our experiment, as it was in previous experiments involving a shear flow.…”

Experimental investigation of dynamical structures formed due to a complex plasma flowing past an obstacle

“…Such a diagnostic convenience has facilitated many experimental investigations of flow phenomena in dusty plasmas including flow past obstacles 13,16,[19][20][21][22][23][24][25] . Thompson et al 19 experimentally investigated the interactions between an electrically floating metallic rod and charged microparticles either by keeping the rod at rest or by moving it through a dusty plasma with velocities of the order of or much faster than the dust acoustic velocity.…”

“…They performed their experiment in a specially designed dusty plasma chamber where the flow was generated by tilting the device with the help of a mechanical jack. Meyer et al 23 performed an experiment on transient bow shock formation along with a teardrop-shaped wake region on the downstream side by a supersonic dust fluid incident on a biased cylinder. Very recently, precursor solitons and shock waves have been observed for supersonic dust fluid flow over a wire horizontally placed over the cathode plate in a dusty plasma experimental device dedicated to flowing plasma experiments 24,25 .…”