We present an analytical model for electro-hydrodynamic flow that describes the relationship between the corona voltage, electric field, and ion charge density. The interaction between the accelerated ions and the neutral gas molecules is modeled as an external body force in the Navier-Stokes equation. The gas flow characteristics are solved from conservation principles with spectral methods. This multiphysics model is shown to match experimental data for a point-to-ring corona configuration, shedding new insights into mass, charge, and momentum transport phenomena, and can be readily implemented in any numerical simulation.

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Ultrafine particle behavior in electro-hydrodynamic (EHD) flow induced by corona discharge is studied experimentally and numerically. The EHD flow serves as a primary particle aspiration/ sampling mechanism, the collector does not require any additional flow generation. Multiphysics numerical model couples the ion transport equation and the Navier-Stokes equations (NSE) to solve for the spatiotemporal distribution of electric field, charge density, and flow field, the results are compared with experimental velocity profiles at the exit. The computed velocity and flow rate data are in good agreement with the experimental data; the maximum velocity is located at the axis and ranges from 1 m/s to 4 m/s as a function of corona voltage. Experimentally evaluated particle transmission trends for ambient and NaCl nanoparticles particles in the 20 nm -150 nm range are in good agreement with the theoretical models. However, for particles in the 10 nm -20 nm size range, the transmission is lower due to the increased particle charging resulted from their exposure to the high-intensity electric field and high charge density in the EHD driven flow. These conditions yield a high probability of particles below 20 nm to acquire and hold a unit charge. The transmission is lower for smaller particle (10 nm) due to their high charge to mass ratio, and it increases as the single-charged particles grow in mass up to 20 nm, resulting in their lower electrical mobility. For particles larger than 20 nm, the electrical mobility increases again as they can acquire multiple charges. The results shed insight into interaction of nanoparticle and ions in high electrical field environment, that occur in primary EHD driven flows and in the secondary flows generated by corona discharge.

To date, insect scale robots capable of controlled flight have used flapping-wings for generating lift, but this requires a complex and failure-prone mechanism. A simpler alternative is electrohydrodynamic (EHD) thrust, which requires no moving mechanical parts. In EHD, corona discharge generates a flow of ions in an electric field between two electrodes; the high-velocity ions transfer their kinetic energy to neutral air molecules through collisions, accelerating the gas and creating thrust. We introduce a fabrication process for EHD thruster based on 355 nm laser micromachining, which potentially allows for greater materials selection, such as fiber-based composites, than is possible with semiconductor-based lithographic processing. Our four-thruster device measures 1.8 × 2.5 cm and is composed of steel emitters and a lightweight carbon fiber mesh. We measured the electrical current and thrust of each thruster of our four-thruster design, showing agreement with the Townsend relation. The peak thrust of our device, at 5.2 kV, was measured to be 3.03 times its 37 mg (363.0 μN) mass using a precision balance. In free flight, we demonstrated liftoff at 4.6 kV.

Electrohydrodynamic (EHD) thrust is produced when ionized fluid is accelerated in an electric field due to the momentum transfer between the charged species and neutral molecules. We extend the previously reported analytical model that couples space charge, electric field and momentum transfer to derive thrust force in one-dimensional planar coordinates. The electric current density in the model can be expressed in the form of Mott–Gurney law. After the correction for the drag force, the EHD thrust model yields good agreement with the experimental data from several independent studies. The EHD thrust expression derived from the first principles can be used in the design of propulsion systems and can be readily implemented in the numerical simulations.