Effect Of Electrical Forces Research Articles

Performance Assessment of an Electrostatic Filter-Diverter Stent Cerebrovascular Protection Device: Evaluation of a Range of Potential Electrostatic Fields Focusing on Small Particles.

Silent Brain Infarction (SBI) is increasingly recognized in patients with cardiac conditions, particularly Atrial Fibrillation (AF) in elderly patients and those undergoing Transcatheter Aortic Valve Implantation (TAVI). While these infarcts often go unnoticed due to a lack of acute symptoms, they are associated with a threefold increase in stroke risk and are considered a precursor to ischemic stroke. Moreover, accumulating evidence suggests that SBI may contribute to the development of dementia, depression, and cognitive decline, particularly in the elderly population. The burden of SBI is substantial, with studies showing that up to 11 million Americans may experience a silent stroke annually. In AF patients, silent brain infarcts are common and can lead to progressive brain damage, even in those receiving anticoagulation therapy. The use of cerebral embolic protection devices (CEPDs) during TAVI has been explored to mitigate the risk of stroke; however, their efficacy remains under debate. Despite advancements in TAVI technology, cerebrovascular events, including silent brain lesions, continue to pose significant challenges, underscoring the need for improved preventive strategies and therapeutic approaches. We propose a device consisting of a strut structure placed at the base of the treated artery to model the potential risk of cerebral embolisms caused by atrial fibrillation, thromboembolism, or dislodged debris of varying potential TAVI patients. The study has been carried out in two stages. Both are based on computational fluid dynamics (CFD) coupled with the Lagrangian particle tracking method. The first stage of the work evaluates a variety of strut thicknesses and inter-strut spacings, contrasting with the device-free baseline geometry. The analysis is carried out by imposing flow rate waveforms characteristic of healthy and AF patients. Boundary conditions are calibrated to reproduce physiological flow rates and pressures in a patient's aortic arch. In the second stage, the optimal geometric design from the first stage was employed, with the addition of lateral struts to prevent the filtration of particles and electronegatively charged strut surfaces, studying the effect of electrical forces on the clots if they are considered charged. Flowrate boundary conditions were used to emulate both healthy and AF conditions. Results from numerical simulations coming from the first stage indicate that the device blocks particles of sizes larger than the inter-strut spacing. It was found that lateral strut space had the highest impact on efficacy. Based on the results of the second stage, deploying the electronegatively charged device in all three aortic arch arteries, the number of particles entering these arteries was reduced on average by 62.6% and 51.2%, for the healthy and diseased models respectively, matching or surpassing current oral anticoagulant efficacy. In conclusion, the device demonstrated a two-fold mechanism for filtering emboli: (1) while the smallest particles are deflected by electrostatic repulsion, avoiding micro embolisms, which could lead to cognitive impairment, the largest ones are mechanically filtered since they cannot fit in between the struts, effectively blocking the full range of particle sizes analyzed in this study. The device presented in this manuscript offers an anticoagulant-free method to prevent stroke and SBIs, imperative given the growing population of AF and elderly patients.

Performance assessment of an electrostatic filter-diverter stent cerebrovascular protection device. Is it possible not to use anticoagulants in atrial fibrilation elderly patients?

Stroke is the second leading cause of death worldwide. Nearly two-thirds of strokes are produced by cardioembolisms, and half of cardioembolic strokes are triggered by Atrial Fibrillation (AF), the most common type of arrhythmia. A more recent cause of cardioembolisms is Transcatheter Aortic Valve Replacements (TAVRs), which may onset post-procedural adverse events such as stroke and Silent Brain Infarcts (SBIs), for which no definitive treatment exists, and which will only get worse as TAVRs are implanted in younger and lower risk patients. It is well known that some specific characteristics of elderly patients may lower the safety and efficacy of anticoagulation therapy, making it a real urgency to find alternative therapies. We propose a device consisting of a strut structure placed at the base of the treated artery to model the potential risk of cerebral embolisms caused by dislodged debris of varying sizes. This work analyzes a design based on a patented medical device, intended to block cardioembolisms from entering the cerebrovascular system, with a particular focus on AF, and potentially TAVR patients. The study has been carried out in two stages. Both of them based on computational fluid dynamics (CFD) coupled with Lagrangian particle tracking method. The first stage of the work evaluates a variety of strut thicknesses and inter-strut spacings, contrasting with the device-free baseline geometry. The analysis is carried out by imposing flowrate waveforms characteristic of both healthy and AF patients. Boundary conditions are calibrated to reproduce physiological flowrates and pressures in a patient's aortic arch. In the second stage, the optimal geometric design from the first stage was employed, with the addition of lateral struts to prevent the filtration of particles and electronegatively charged strut surfaces, studying the effect of electrical forces on the clots if they are considered charged. Flowrate boundary conditions were used to emulate both healthy and AF conditions. Results from numerical simulations coming form the first stage indicate that the device blocks particles of sizes larger than the inter-strut spacing. It was found that lateral strut space had the highest impact on efficacy. Based on the results of the second stage, deploying the electronegatively charged device in all three aortic arch arteries, the number of particles entering these arteries was reduced on average by 62.6% and 51.2%, for the healthy and diseased models respectively, matching or surpassing current oral anticoagulant efficacy. In conclusion, the device demonstrated a two-fold mechanism for filtering emboli: while the smallest particles are deflected by electrostatic repulsion, avoiding microembolisms, which could lead to cognitive impairment, the largest ones are mechanically filtered since they cannot fit in between the struts, effectively blocking the full range of particle sizes analyzed in this study. The device presented in this manuscript offers an anticoagulant-free method to prevent stroke and SBIs, imperative given the growing population of AF and elderly patients.

Linear, second-order, unconditionally energy stable scheme for an electrohydrodynamic model with variable density and conductivity

The motion of ions in the complex fluids widely appears in biofluids, hydrodynamics, geodynamics and geophysics. Performing efficient and accurate computation for electrohydrodynamic flows is challenging due to the multiphysics and complex nature of the problem. In this paper, we describe a new second-order linear energy stable time-stepping scheme for a variable density electrohydrodynamic power-law model, which satisfies an energy dissipation law. Firstly, a square root transformation for the fluid density and a logarithmic transformation for the electrical conductivity are used to enforce the positivity-preserving property for these two physical parameters. Secondly, by using the zero energy contribution property of the nonlinear coupling terms in the model and introducing a nonlocal auxiliary variable, an equivalent continuous formulation of the model is obtained. Finally, a two-step backward differentiation scheme is proposed for the resulting equivalent model to construct the time-stepping scheme, and the finite element method is used for spatial discretization. The scheme is proved to be unconditionally energy stable and a nonlocal splitting technique can be utilized to yield several linear subsystems, which can be solved more easily. Numerical simulations are carried out to demonstrate the accuracy and stability of the scheme. The dispersion of electrical conductivity and the effect of electrical force on the Rayleigh–Taylor instability are studied for both shear-thinning and shear-thicking fluids.

Numerical investigation on the effect of electrical force and periodic force on neutrally buoyant spherical particles in a Newtonian fluid at low Reynolds numbers

This topic examines a periodically forced neutrally buoyant spherical particle in an electrically driven dilute solution with the velocity at very long distances (infinity) at low Reynolds numbers. This is a novel problem since it considers the periodic force as well as the electric force operating on the spherical particle/s. When particle-laden suspensions are exposed to electric stress, electrophoresis and electrostriction occur. Consequently, these studies might be used to blood flow to perform electrophoresis on red blood cells and study their activity. We have used the formalism of Lovalenti and Brady [14] to obtain the necessary equations for our considered problem. All the results with U∞ = 0 and U∞ equals specific values are plotted in the form of phase plots between displacements of the particle versus the velocity of the particle. It is observed that the resistance to the change in motion of the particle is manifested in the phase plots and the periodic force is dominant over the considered DC electric field for the Reynolds numbers considered. The DC force translates the particles with different amplitudes of the periodic force. We also computed the only rheological parameter the normal stress difference using Batchelor's technique with respect to volume fraction and amplitude of periodic force with respect to time. The presence of normal stress indicates the non – Newtonian behaviour in this type of phenomena.

Impact of the electromagnetic flow of an MHD Casson fluid over an oscillating porous plate

AbstractThis study deals with the effect of electric force and magnetohydrodynamics (MHD) of the transient state on natural convection flow past an oscillating vertical plate. In addition to this, thermal radiation and porous media are also examined in the Casson fluid flow. The Poisson‐Boltzmann equation is employed to show the electric potential character within the fluid region, which is put into a linear form by the implementation of Debye–Hückel linearization. It is possible to compute the precise solution to the governing equations using the Laplace transform approach. The expression of fluid velocity, fluid concentration, and temperature are exposed graphically, and numerical results for Nusselt and Sherwood numbers are also derived for vital pertinent flow constraints. Increasing electroosmosis parameters strongly boosts fluid velocity. The nonnegative values of the Helmholtz–Smoluchowski velocity highly induce the axial velocity and the negative value decelerates. With increasing radiation strength and Prandtl number, the fluid's temperature distribution diminishes. These more intricate electrokinetic rheological flows associated with electroosmotic separators, such as biomedical absorbers, are illuminated by these models.

Numerical Simulation of Aging by Water-Trees of XPLE Insulator Used in a Single Hi-Voltage Phase of Smart Composite Power Cables for Offshore Farms

Submarine power cables are expected to last 20 years without maintenance to be considered technologically reliable enough and economically beneficial. One of the main issues facing this target is the development of what is called commonly water-trees (nanometer-sized flaws filled with residual humidity), that form within XLPE (cross-linked Polyethylene) insulators and then migrate towards copper, thus leading to its corrosion and further to possible shut-down. Water trees are resulting from the coalescence of nanovoids filled with residual humidity that migrate towards copper under the combined effects of electrical forces and plastic deformation. The nanovoids are originated during manufacturing, shipping, handling and embedding in deep seas. The formation of these nanovoids leads to the degradation of the service lifetime of submarine power cables. Current research is intended to come up with a way to go a little further towards the generalization of coalescence of n nanovoids. In the perspective of multi-physics modeling, a preliminary 3D finite element model was built. Although water voids are distributed randomly inside XLPE, in this study, two extreme cases where the voids are present parallel and perpendicular to the copper surface, were considered for simplification. This will enable checking the electric field effect on neighbouring voids, in both cases as well as the influence of the proximity of the conductor on the plasticity of voids, that further leads to their coalescence. It is worthwhile to note that assessing water-trees formation and propagation through an experimental campaign of ageing tests may extend over decades. It would therefore be an exceptional opportunity to be able to get insight into this mechanism through numerical modeling that needs a much shorter time. The premilinary model suggested is expected to be extended in the future so that to include more variables (distribution and shapes of nano-voids, water pressure, molecular modeling, electric discharge.

Experimental Study of Water Collection from Plume of an Induced-Draft Counter-Flow Cooling Tower Using Space Charge Injection

Plume collection from cooling towers can be a reliable solution to the water scarcity problem faced in many regions around the world. Meshes are one of the most proposed collectors in this regard that rely upon inertial collision for droplet capture and are inherently limited by aerodynamics. This study quantifies the effect of electrical forces on water collection from the plume of an Induced Draft Counter Flow (IDCF) Cooling Tower by introducing sets of copper tubes at the exit of the tower. The imparting of net charge to the exhaust plume by instigating space charge directs the vapor towards the inside wall of copper tube forming water droplets. This arrangement instead of a mesh or net system, creates a lesser obstruction to flow. Fabrication of fill/packing with a corrugated wave pattern using PVC plastic demonstrates satisfactory cooling performance of the tower. An optimized L/G ratio is found to exist for maximum collection efficiency of water from plume at definite entering fluid temperatures by investigating with the entering warm water temperatures at 40°C, 45°C and 50°C while the dry bulb temperature of air ranges from 23.5°C to 30.1°C. The electricity consumption for this arrangement fluctuates from 2.78 kWh/m3 to 5.13 kWh/m3 for two L/G ratios (23.5 and 28.3). Where maximum collection percentage occurs at two different entering fluid temperatures, the power expended is below the minimum used for typical desalination plants.

Numerical Simulation of Flow Field and Ion Transport for Different Ion Source Sampling Interfaces of a Mass Spectrometer.

Understanding ion transport mechanisms in the flow expansion section of the first vacuum region of a mass spectrometer (MS) with an atmospheric pressure ionization source is essential for optimizing the MS sampling interface design. In this study, numerical simulations of three types of ions in two different MS interface designs have been carried out. In contrast to previously reported numerical studies, nonequilibrium gas dynamics due to rarefied gas effects has been considered in modeling the flow expansion and a realistic space charge effect has been considered in a continuous ion injection mode. Numerical simulations reveal that a flat plate interface has a higher peak buffer gas velocity but a narrower zone of silence compared to the conical interface. Shock wave structures are clearly captured, and the Knudsen number distribution is displayed. Simulation results show that in the axial direction the buffer gas effect is much stronger than the electric force effect in the current configuration. The conical interface leads to both a strong ion acceleration in the zone of silence and a strong ion deceleration downstream. In the radial direction, both the electric force and buffer gas drag force play an important role. The conical interface introduces a relatively stronger ion focusing effect from the radial buffer gas effect and a stronger ion dispersion from the radial electric force than the flat plate interface. The net effect for the current configuration is an increase in ion losses for the conical interface. Nanoelectrospray ionization experiments were carried out to validate the ion transmission efficiency.

Effect of electrohydrodynamic stresses in dielectric liquid: simulation study with the aid of single artificial air bubble using level set‐volume of fluid method

Pre-breakdown analysis of dielectric liquids is important in many power system applications. The electric field effect is important as well in pool boiling as it improves the boiling process. This physical phenomenon combined with the pre-breakdown condition in a dielectric liquid has been investigated using a single artificial air bubble immersed in the dielectric liquid and attached to a high voltage electrode. The Level Set coupled with Volume of Fluid numerical method is used to simulate the behaviour of the air bubble in the dielectric liquid. This approach combined with considering the electrical stresses accounts for both the electrical and mechanical (Electrohydrodynamic) stresses on the bubble-liquid interface. Laplace's equation is used to solve the electric field distribution, while the fluid is solved by using Navier–Stokes equations. The electric force effect on the fluid is considered as a source term in the momentum equation. The simulation results show good agreement with the experimental data. It is observed that high-velocity eddies in the order of 22.88 mm/ss are generated inside the air bubble. These eddies are caused by high-pressure gradients near the bubble boundaries caused by the electric field. This high velocity improves the heat and mass transfer between the two fluids.

Estimation of the electric force effect on dispersed additives in the heterogenous combustion flame plasma in the electrostatic field presence

In the work, the influence of the electric force from the external electric field on the charged dispersed particles in the flame was evaluated. It is assumed that changes in the effect of the field on the combustion rate in the presence of dispersed additives in the gas phase take place due to the heat flux into the burning polymer condensed phase changes. However, as it turned out, the flame front moving towards the fuel under the action of field forces does not allow to fully explain the combustion rate increase.

A numerical study of electric force effects on detachment and deposition of particles due to a falling disk

One of the main sources of particulate matter (PM) in indoor environments is particle resuspension due to human activities such as walking. In many situations, surfaces are charged, and electric forces become important. As the human gait cycle induced airflow and electric fields and their interaction with particle resuspension, dispersion and deposition are rather complicated, using a simplified model can help to gain a better understanding of process. In this study, the effect of presence of electric field on particle detachment and deposition due to a falling disk was investigated using a computational modeling approach. For this purpose, a charged disk was considered to be falling freely on a rough surface from a specific height. The disk electric potential developed an electric field throughout the domain that intensified as the disk gets closer to the floor. The electric field charged the particles that were resting on the floor by the field charging mechanism. It was found that the presence of electric force decreased the critical shear velocity needed to detach the particles; however, the reduction was negligible for particles smaller than 5 µm. In addition, the simulation results showed that the number of particles deposited on the disk increased with the size of particles in the presence of electric field. The results of this study provide a better understanding of the effect of the electric potential induced due to human activities on detachment and dispersion of particles in indoor environments.

The combined effect of electric forces and confinement ratio on the bubble rising

In this work, the combined effect of electrohydrodynamic forces and domain confinement on the formation of a toroidal bubble is numerically studied. The numerical scheme is the Volume of Fluid (VOF) method and the surface tension and electric forces are implemented using the Continuum Surface Force (CSF) and leaky dielectric models, respectively. It is found that both domain confinement and electric forces are influential on the formation of a toroidal bubble. For smaller confinement ratios, larger electric forces are required to pierce the bubble. Moreover, the influence of both electric forces and confinement ratio are presented and discussed for bubble vertical velocity, terminal Reynolds number, velocity streamlines and side-wall shear stress.

Electroosmotic flow in optimally operated micro heat pipes

Micro heat pipe, a capillary-driven two-phase heat transfer microsystem, serves as an effective cooling device for electronic components. Based on a mathematical model employing the conservation laws to yield the heat and fluid flow characteristics of a micro heat pipe, we demonstrate how the basic principles of electroosmotic flow can be applied to enhance the performance of micro heat pipes. To provide a thorough and comprehensive analysis, both favorable and adverse effects of electroosmotic flow on the thermal performance of a micro heat pipe are studied. The thermal performance of a micro heat pipe is strongly dependent on the circulation effectiveness of working fluid. A well-defined parameter is employed to characterize the effects of the electric force on the circulation effectiveness of the working fluid with different ion concentrations. The aiding effect of electric force increases the circulation rate of working fluid, resulting in a significant enhancement in the heat transport capacity of micro heat pipe. By investigating the solid wall temperature profiles, the use of electroosmosis in enhancing the thermal performance of a micro heat pipe is deemed to be practically feasible due to the fact that significant enhancement can be achieved with a compensation of small temperature drop at a reasonably low applied voltage.

A theoretical interpretation of the “giant” dust particle conundrum

The effects of electric force were used to interpret a well known conundrum about the long-term (or long-distance) dust transport in the atmosphere.

Shape and oscillations of the water drops freely suspended in a horizontal electric field: A wind tunnel study

The time-averaged axis ratios, frequency and amplitude of oscillations of water drops of 2.67–6.6mm diameter were determined by suspending them in a vertical wind tunnel in the absence and presence of horizontal electric fields using a high speed camera at 1000 frames per second. A systematic decrease in the drop's axis-ratio is observed with increase in its diameter and/or horizontal electric field. The results revealed with high speed photography are in good agreement with earlier results. The drop distortion due to horizontal electric field is more pronounced for the drops in the size-range of 3.36–6mm diameter showing that the electrical forces progressively enhance the horizontal elongation of the drop resulting in its instability at 6.6mm. The drop oscillation frequency computed from temporal variation of axis ratio, decreases with increase in drop size but shows no significant change in oscillation frequency in the horizontal electric field of ≤500kVm−1. However, the oscillation amplitude increases with increase in drop size up to a threshold value and then flatten-off in the electric field of ≤300kVm−1 demonstrating the nonlinear effect of net forces acting on such large drops. In higher electric field of 500kVm–1, gradual increase in the amplitude of oscillation with an increase in drop diameter has been observed. Moreover, for a particular drop size, the amplitude of oscillation decreases with increase in the electric field upto 500kVm−1. The oscillation frequency of the waterdrops experiences multimode oscillations. The dominant fundamental mode of oscillations (2,0) always exists for all drops in our experiments along with the coexistence of higher modes of oscillations i.e. (2,1) and (2,2) mode. Possible effects of electrical forces on shape parameters and their implications on cloud microphysics and in radar meteorology are discussed.

Electro-osmotic slip flow of Eyring fluid in a slit microchannel

The electro-osmotic flow of a non-Newtonian fluid in a slit micro-channel under the Navier's slip boundary condition is investigated. The Eyring constitutive relationship model is adopted to describe the non-Newtonian characteristics of the flow driven by the applied electric field force and pressure. In consideration of the micro-scale effects, electric field, non-Newtonian behavior and slip boundary condition, a mechanical model is built and the effects of these factors on the flow are studied. Analytical expressions are derived for the electric potential and velocity profile by solving the linearized Poisson-Boltzmann equation and the modified Cauchy equation. Approximate expressions of the velocity distribution are also given and discussed. Furthermore, by comparing the effects of electric force with that of pressure on the velocity distribution, some meaningful conclusions are drawn from the obtained graphics.

Mechanism of Collection of Dust Particles by Charged Droplet

The paper presents a numerical algorithm for simulating the trajectories of charged dust particles moving horizontally in the vicinity of an oppositely charged droplet. With taking the air drag, electrical and gravitational into account, the trajectories of charged dust particles are traced by solving the Newton equation. Calculation results show that the dust particles deposit in the whole surface of charged droplet by the effect of electrical force. Electrical force becomes the main factor for dust deposition at low Stokes.

Study of a Newtonian Fluid through Circular Channels with Slip Boundary Taking into Account Electrokinetic Effect

We study the slip flow of fluids driven by the combined effect of electrical force and pressure gradient. The underlying boundary value problem is solved through the use of Fourier series expansion in time and Bessel function in space. The exact solutions and numerical investigations show that the slip length and electrical field parameters have significant effects on the velocity profile. By varying these system parameters, one can achieve smooth velocity profiles or wave form profiles with different wave amplitude and frequency. This opens the way for optimizing the flow by choosing the slip length, the electrical field, and electrolyte solutions.

Particle deposition with thermal and electrical effects in turbulent flows

Development of relationships for the particle concentration and convection velocity profile has been obtained by the adaptation of the surface renewal model to the particle continuity and momentum equations of the turbulence boundary-layer flow in the presence of thermal field [1]. The predictions obtained on the basis of this model for nonisothermal deposition velocity of particles have been found to be in good agreement with the experimental measurements for fully-developed turbulence tube flow conditions. The aim of this work is to extend the previous model for an applied electric field, with the inclusion of the effect of Coulombic force in addition to the Brownian and turbulent diffusion, the eddy impaction, the turbophoresis, and the thermophoresis. The calculations show an interaction between thermophoresis and turbophoresis in the presence of an applied electric field. The effect of electric force in nonisothermal flows can have a dramatic effect on thermophoretic deposition for τ p + < 0.02 , where turbophoretic effect has ceased. The effect of axial pressure gradient is also included.

The effects of electric forces on dust lifting: Preliminary studies with a numerical model

Atmospheric dust aerosols affect the Earth's climate by scattering and absorbing radiation and by modifying cloud properties. Recent experiments have indicated that electric fields produced in dusty phenomena such as dust storms and dust devils could enhance the emission of dust aerosols. However, the generation of electric fields in dusty phenomena is poorly understood. To address this problem, we present results from the first physically-based numerical model of electric fields in dust lifting. Our model calculates the motion and collisions of air-borne particles, as well as the charge transfer during these collisions. This allows us to simulate the formation of electric fields as a function of physical parameters, such as wind stress and soil properties. Preliminary model results show that electric fields can indeed enhance the lifting of soil particles. Moreover, they suggest that strong electric fields could trigger a positive feedback because increases in the concentration of charged particles strengthen the original electric field, which in turn lifts additional surface particles. We plan to further test and calibrate our model with experimental data.