Electrohydrodynamic ionic wind, force field, and ionic mobility in a positive dc wire-to-cylinders corona discharge in air

Abstract

Ionic wind refers to the acceleration of partially ionized air between two high-voltage electrodes. We study the momentum transfer from ions to air, resulting from ionic wind created by two asymmetric electrodes and producing a net thrust. This electrohydrodynamic (EHD) thrust, has already been measured in previous studies with digital scales. In this study, we provide more insights into the electrohydrodynamic momentum transfer for a wire-to-cylinder(s) positive dc corona discharge. We provide a simple and general theoretical derivation for EHD thrust, which is proportional to the current/mobility ratio and also to an effective distance integrated on the surface of the electrodes. By considering various electrode configurations, our investigation brings out the physical origin of previously obtained optimal configurations, associated with a better tradeoff between Coulomb forcing, friction occurring at the collector, and wake interactions. By measuring two-dimensional velocity fields using particle image velocimetry (PIV), we are able to evaluate the resulting local net force, including the pressure gradient. It is shown that the contribution of velocity fluctuations in the wake of the collecting electrode(s) must be taken into account to recover the net thrust. We confirm the proportionality between the EHD force and the current/mobility ratio experimentally, and evaluate the ion mobility from PIV measurements. A spectral analysis of the velocity fluctuations indicates a dominant frequency corresponding to a Strouhal number of 0.3 based on the ionic wind velocity and the collector size. Finally, the effective mobility of charge carriers is estimated by a PIV based method inside the drift region.

Numerical study of ElectroAeroDynamic force and current resulting from ionic wind in emitter/collector systems

“…Note that such charge leaks exist in experiments, and some numerical studies have sometimes introduced them in their boundary conditions so as to better match with their measurements [9]. Secondly, from the action/reaction principle, the total Electro-AeroDynamic (EAD) force exerted on the gas equals the propulsive force exerted onto the device [28]. This EAD force F EAD (per unit length in the span-wise direction) can thus be obtained from integrating local Coulomb force f C = ρE over the 2D domain:…”

“…where∇ and∆ are the gradient and Laplacian operators expressed in terms of the non-dimensional variables, and where the electro-convective Péclet number is defined as P e = µV R col /D ρ . In this problem P e 1 [29,30,28], so that ( 18) is strongly hyperbolic dominated. Dimensionless boundary conditions ( 3) and ( 4) then read…”

Strong, Durable, and Aging-Resistant Bamboo Composites Fabricated by Silver In Situ Impregnation

“…The major peaks at 285.8, 368.8/373.8, and 532.8 eV were attributed to C 1s, Ag 3d 5/2 /Ag 3d 3/2 , and O 1s, respectively. From Figure d, it can be observed that the peak of Ag was produced by silver in situ impregnation treatment because silver ions and electrons collide with bamboo . The O/C ratio of the treated bamboo reduced markedly (Table ).…”

“…From Figure 4d, it can be observed that the peak of Ag was produced by silver in situ impregnation treatment because silver ions and electrons collide with bamboo. 50 The O/C ratio of the treated bamboo reduced markedly (Table 2). The possible reasons are as follows: (1) silver ions have a certain effect, resulting in a decrease in the content of oxygencontaining functional groups and decarboxylation reactions −OH, CO, and −COOH 51 and (2) silver particles penetrate bamboo vessels under treatment and cover bamboo functional groups.…”

Flying with ionic wind

“…These technological developments should provide a better understanding of the coupled physics of charged-molecule production and the resulting ionic wind that is central to such propulsion systems. The force generated by ionic wind is directly proportional to the electric current that flows in the system 2,10 . Because this current is strongly dependent on the configuration of emitters and collectors, research into the conception and optimization of ionicwind propulsion can now begin, thanks to the breakthrough by Xu…”