LSTM-PINN: An hybrid method for prediction of steady-state electrohydrodynamic flow

Alternating current (AC) electric fields have the potential to induce complex morphological transitions in liquid–liquid systems. In this paper, the instability evolution of the charged methanol droplets in oleic acid under non-uniform AC electric field is investigated by using high-speed imaging. It is found that charged droplets experienced various morphological transitions induced by the AC electric field. For low electric Bond number (BoE), a finger-shaped instability is initiated from the droplet, followed with finger growth and subsequent branching. With the increase in electric field strength, novel morphologies of stretched bottom membrane and radially ejected annulus-shaped film emerge while an explosive Coulomb breakup is found at extremely high field strengths. Throughout the range of instabilities, a transition from disordered to highly ordered polygonal droplet contours is found to be driven by the bifurcation effect in the internal electrohydrodynamics (EHD) flow. Moreover, the growth rate and characteristic wavelength of the instabilities exhibit saturation at high BoE. This nonlinear effect is attributed to the dominance of charge convection, which limits the local surface charge density at the finger tips. Overall, the non-uniform AC electric field provides a method for regulating multi-scale fluid interface morphology in high-viscosity-ratio fluids.

Investigating electrohydrodynamic flow and particle behavior: The role of angle between electric wind and primary airflow in electrostatic precipitators

Three-dimensional electrohydrodynamic flows by a central-moments-based lattice Boltzmann method

Investigating electrohydrodynamic vortical flow and particle transport mechanism in electrostatic precipitators with discharge needles via vortex identification techniques

Fejér-quadrature collocation neural network method for solving ψ-tempered fractional electrohydrodynamics flow model

Recent advancements in active colloidal systems aim to mimic key characteristics of biological microswimmers, particularly their adaptive motility in response to environmental changes. While many approaches rely on externally imposing a variable propulsive force, achieving true autonomous and self-regulating adaptation to the environment remains limited. In this study, we take a step in this direction and develop Janus microswimmers driven by electrohydrodynamic flows that autonomously adjust their propulsion dynamics in response to varying illumination and exposure to chemical agents. Our Janus particles are silica colloids partially coated with titania, which self-propel via induced-charge electrophoresis under uniform AC electric fields. Since titania is photoconductive, it increases its conductivity under UV illumination, which thereby regulates the propulsion velocity independent of and orthogonally to the applied electric field. Crucially, the velocity adaptation happens spontaneously but requires a finite amount of time. This sensory delay leads to enhanced microswimmer localization in response to spatiotemporal light modulations compared with the typical case of instantaneous response considered for synthetic microswimmers. Additionally, the particles spontaneously adapt their response time in the presence of chemicals, here methanol, which affect the lifetime of charge carriers and lead to a concentration-dependent response. By harnessing these dynamics, akin to those of biological microswimmers, we control both local and global particle behavior, presenting exciting opportunities for adaptive active matter systems.

Validity of Particle Image Velocimetry Measurements in Electrohydrodynamic Flows

Active semiflexible filaments are crucial for biophysical processes, yet insights into their single-filament behavior have predominantly relied on theory and simulations, owing to the scarcity of controllable synthetic systems. Here, we present an experimental platform of active semiflexible filaments composed of dielectric colloidal particles activated by an alternating electric field that induces contractile or extensile electrohydrodynamic (EHD) flows. Our experiments reveal that contractile flow-generating filaments (CFs) undergo softening, significantly expanding the range of accessible conformations, whereas extensile filaments (EFs) exhibit active stiffening. By independently tuning filament elasticity and activity, we show that the competition between elastic restoring forces and emergent hydrodynamic interactions along the filament governs conformational dynamics. Specifically, we find that the time scale of conformational dynamics governs the transport of active filaments: enhanced fluctuations lead to diffusive motion despite activity, whereas activity-induced stiffening enables directed propulsion in nonlinear filaments. Our findings highlight that conformational changes, not just geometric or chemical asymmetry, enable propulsion of flexible microswimmers. These insights are essential for designing flexible microswimmers, whose transport can be tailored through controlled activity and shape changes. Additionally, our system provides a powerful platform for gaining fundamental insights into active filament dynamics.

The leaky dielectric model is widely used in simulating two-phase electrohydrodynamic (EHD) flows. One critical issue with this classical model is the assumption of Ohmic conduction, which makes it inadequate for describing the newly discovered EHD flows caused by the Onsager-Wien effect [Ryu et al., “New electrohydrodynamic flow caused by the Onsager effect,” Phys. Rev. Lett. 104(10), 104502 (2010)]. In this paper, we proposed a phase-field lattice Boltzmann (LB) method for two-phase EHD flows induced by the Onsager-Wien effect. In this scheme, two LB equations are employed to resolve the incompressible Navier–Stokes equations and the conservative Allen-Cahn equation, while another three LB equations are used for solving the ionic concentration equations and the electric potential equation. After we validate the developed LB method, we perform a series of numerical simulations of droplet deformation under EHD conduction phenomena. Our numerical results indicate that the presence of the Onsager-Wien effect has a significant impact on droplet deformation and charge distribution. Also, it is interesting to note that, apart from the heterocharge layers near the electrodes, a charge cloud may form between the droplet interface and the electrode in some cases. To thoroughly understand the droplet dynamics, the effects of the reference length d, the applied voltage Δψ, the permittivity ratio εr, and the ionic mobility ratio μr on droplet deformation and charge distribution are all investigated in detail.

Corrigendum to “Mathematical modeling of electro hydrodynamic non-Newtonian fluid flow through tapered arterial stenosis with periodic body acceleration and applied magnetic field” [Applied Mathematics and Computation, 362(2019) 124453

This research presents an experimental analysis of the influence of atmospheric pressure plasma on the performance of a micro horizontal-axis wind turbine blade. The investigation was conducted using an NACA 4412 airfoil equipped with a dielectric barrier discharge (DBD) plasma actuator. The electrodes were configured asymmetrically, with a 2 mm gap and copper electrodes that are 0.20 mm in thickness. A high voltage of 6 kV was applied, resulting in a current of 0.071 mA and a power output of 0.426 W. Optical emission spectroscopy identified the excited components through the interaction of the high-voltage AC electric field with air molecules: N2, N2+, O2+, and O. The electrohydrodynamic force mainly results from the observed charged ions that, when accelerated by the electric field, transfer momentum to neutral molecules via collisions, leading to the formation of the observed jet plasma. The findings indicated a notable enhancement in aerodynamic performance attributable to the electrohydrodynamic (EHD) flow generated by the plasma. The estimated electrohydrodynamic force (8.712×10−4 N) is capable of maintaining the flow attached to the airfoil surface, thereby augmenting flow circulation and, consequently, enhancing the lift force. According to blade element theory, the lift and drag coefficients directly influence the torque and mechanical power generated by the wind turbine rotor. Schlieren imaging was utilized to observe alterations in air density and flow patterns. Lissajous curve analysis was used to examine the electrical discharge behavior, showing that only 7.04% of the input power was converted into heat. This indicates that nearly all input electric energy was transformed into EHD force by the atmospheric pressure plasma. Compared to traditional aerodynamic control methods, DBD actuators are a feasible alternative for small wind turbines due to their lightweight design, absence of moving parts, ability to be surface-embedded without altering blade geometry, and capacity to generate active, dynamic flow control with reduced energy consumption.

Particles in a sufficiently strong electric field spontaneously rotate, provided that charge relaxation is slower in the particle than in the suspending fluid. It has long been known that drops also exhibit such “Quincke rotation,” with the electrohydrodynamic flow induced by electrical shear stresses at the interface leading to an increased critical field. However, the hysteretic onset of this instability, observed for sufficiently low-viscosity drops, has so far eluded theoretical understanding—including simulations that have struggled in this regime owing to charge-density steepening driven by surface convection. Here, we conduct a numerical study of the leaky-dielectric model in a simplified two-dimensional setting involving a circular drop, considering arbitrary viscosity ratios and field strengths. As the viscosity of the drop is decreased relative to the suspending fluid, the pitchfork bifurcation marking the onset of drop rotation is found to transition from supercritical to subcritical, giving rise to a field-strength interval of bistability. In this subcritical regime, the critical field is always large enough that, at the bifurcation, the symmetric base-state solution exhibits equatorial charge-density blowup singularities of the type recently described by Peng []. As the rotation speed increases along the initially unstable solution branch from the bifurcation, the singularities gradually shift from the equator and ultimately disperse once the rotational component of the flow is strong enough to eliminate the surface stagnation points.

The convective and absolute instabilities in electrohydrodynamic-Poiseuille mixed convection for viscoelastic fluids with the Oldroyd-B model are examined. In the absence of Poiseuille flow, based on the stationary and oscillatory characteristics at the onset of convection, we distinguish weakly and strongly elastic fluid, dominated by viscosity effects and elasticity effects, respectively. Their borderline of the two effects in terms of the critical electric Weissenberg W_{ec} satisfies the relation W_{ec}=a/(1-β)+b where β is viscosity ratio, and the parameters a and b depend on dimensionless ion mobility. In the presence of Poiseuille flow, with an increase in shear strength, the convective and absolute instability thresholds increase in both weakly and strongly elastic fluids, and the jump of phase speed and saddle point shift are observed at low polymer concentration with sufficient elasticity, causing the faster transverse rolls (TRs) to propagate downstream. However, at the high polymer concentration of large W_{e}, instead of downstream moving TRs, the upstream moving TRs can be the most unstable at the onset of absolute instability. Kinetic energy budget analysis reveals that with an increase in shear strength and elasticity, the suppressive effect of polymeric stresses on instability is enhanced in viscosity effects-dominated flow, while it is reduced in elasticity effects-dominated flow. Besides, the energy transfer from the wall-normal gradient of the perturbed electric field to the wall-normal gradient of the perturbed wall-normal velocity under the effect of the wall-normal gradient of the base electric field becomes the most destabilizing factor in the very strongly elastic fluids.

Electrohydrodynamic (EHD) flow results from the interaction of electric fields with ionized charges, becoming more complex in gas–liquid systems due to interfacial deformation. This study analyzed the interfacial deformation induced by corona discharge in an air–water system using two-phase numerical simulations. A fully coupled model was developed to account for the interactions among charge transport, fluid motion, and temporal interfacial deformation under corona discharge. The model was validated experimentally through particle image velocimetry and discharge current measurements. The effects of applied voltage ranging from 5 to 15) kV and height of water ranging from 4 to 12) mm were analyzed. The results showed that higher voltage increased the EHD flow velocity and interfacial deformation depth. The reduced distance between the discharge electrode and the interface further intensified these effects. The relationship among current, flow velocity, and interfacial deformation could be defined. A distinctive observation of self-sustained and periodic interface deformation under EHD flow conditions was presented with a period of 3 s at 12 mm height and 15 kV applied voltage. A phase lag of 0.4 s was observed between fluctuations in current and flow velocity, while maintaining the periodic oscillation. Current oscillations remained within 3% of the mean value, while flow velocity deviations reached 8.9%, indicating significant temporal fluctuations that should not be neglected. This study offers deeper understanding of the relationship among charge transport, flow structure, and interface deformation in gas–liquid EHD systems with potential applications in areas that require precise control of flow and interfacial behavior.

Abstract Dielectric barrier discharge (DBD) plasma actuators generate an electrohydrodynamic (EHD) force through the ionization and acceleration of charged species. Most active flow control DBD applications are only practical at lower Reynolds numbers, and increasing the momentum injection can extend the practical uses of the technology. Here, we experimentally demonstrate improvement in the performance of a planar DBD actuator by utilizing an AC-augmented (ACA) electrical field in a three-electrode geometry. Time-resolved electrical and optical measurements, velocity profiles, and direct thrust measurements were used to characterize the EHD augmentation. Varying phase shift and E-field strength between the two air-exposed DBD electrodes can accelerate EHD flow and increase EHD forcing by up to ∼40%. At the most favorable conditions, the maximum thrust was 54 mN m−1 when the air-exposed electrodes were out of phase. In-phase operation of the exposed electrodes at high E-field conditions can induce adverse effects and sliding discharge. Mechanistically, the performance improvements in the ACA DBD actuator primarily come from the additional charge pull action by the ACA electrode. The insight into the ACA DBD mechanism allows for the development of multi-stage arrays capable of further increasing EHD forces.

Electrohydrodynamics (EHD) are widely utilized to manipulate fluid behaviors in practical applications, such as EHD high-resolution printing and EHD nebulization for producing monodispersed small droplets. In these applications, multicomponent multiphase (MCMP) phenomena with large density contrasts are usually involved. However, previous studies either focused on modeling single-phase multicomponent EHD problems where the densities of different components are the same or multiphase single-component EHD flows with large density contrasts where only one fluid component is considered. Therefore, in this work, a hybrid numerical framework combining MCMP pseudopotential LBM and FDM is implemented and applied to simulate EHD flows, which is capable of simulating MCMP EHD flows with large density ratios and offers tunable surface tension that is independent of viscosity and density ratios. The numerical model is comprehensively validated through benchmarks, including the thermodynamic consistency test, Young-Laplace droplet test, contact angle test, and droplet deformation under an electric field. The results demonstrate the capability of the present model for accurately simulating EHD MCMP flows with high-density ratios, good thermodynamic consistency, low spurious velocity, adjustable surface tension, and wettability. Lastly, the developed model is applied to investigate the effects of fluid electrical properties and electric field strength on the deformation and wettability of a sessile droplet under an external electric field. Published by the American Physical Society 2025

ObjectiveThis study employs numerical simulations to investigate how the structural configurations of collecting plates (flat vs. corrugated plates) affect the efficiency of wire-plate electrostatic precipitators (ESPs).MethodsA coupled model was developed, integrating fluid dynamics, electric fields, and particle motion, with User-Defined Functions explicitly programmed to establish strong connections between these physical fields. The complex fluid dynamics within the ESP channel was captured using the k-ε turbulence model, considering the electric body forces computed from the finite volume solvers of electric field and ion charge. Furthermore, the trajectories of particles were simulated using the Lagrangian approach, considering particle size distribution and particle charging process.ResultsThe corrugated plate optimize the ion charge distribution and intensify the electric field strength in ESPs, favoring particle charging and accelerating particle deposition, particularly for coarse particles. However, this also produces stronger electric wind, leading to the formation of distinct vortex structures in the corrugated channel, which hinder the deposition of fine particles near the walls. At low inlet velocities, the electric wind effect exacerbated the vortices, weakening the separation of fine particles. In comparison, the flat plate exhibited better performance in this regard.ConclusionThese findings provide important theoretical foundations and practical guidance for the design and optimization of ESPs, especially improving the removal efficiency for particles of different sizes.Graphical

Investigating the effects of Lorentz forces on electrohydrodynamic flow generated by corona discharge in a multi needle-to-cylinder configuration

Chiral structures assembled from colloids are of great interest for applications in metamaterials and micromachines. However, similar to their molecular counterparts, these assemblies often result in racemic mixtures. Achieving homochirality by breaking the symmetry remains a significant challenge. Here, we report an approach to obtain single-handed clusters from colloidal dimers using orthogonal electric and magnetic fields. Applying an alternating-current electric field perpendicular to the substrate generates a mixture of chiral clusters with both handedness. However, symmetry is broken by superimposing a planar rotating magnetic field, favoring one chirality over the other. The cluster's chirality can be precisely controlled in situ by adjusting the magnetic field's direction and strength, as well as the electric field frequency. Remarkably, this method also induces uniform chirality in initially achiral clusters when exposed solely to the electric field. Both experimental and numerical analyses reveal that the stability of specific handedness depends on the competition between forces and torques generated by the magnetic field, electric field, and electrohydrodynamic flow. Furthermore, we propose a strategy for producing colloidal clusters with uniform sizes and single-handedness through dynamic tuning of the electric and magnetic fields. This work not only demonstrates the potential of integrating external fields but also provides a viable way to create reconfigurable chiral colloidal structures.