Search Results (187)

This work examines a new methodology for the nonlinear electrohydrodynamic interfacial stability of dielectric viscoelastic liquids to enhance the predictive accuracy of microfluidic and biological applications. It tackles the intricacies of nonlinear coupled dynamics, encompassing interfacial deformation and viscoelastic stress influences. This study examines nonlinear stability, as linear stability has previously been thoroughly scrutinized. The interacting fluids are distinguished by differences in density, dielectric permittivity, permeability, viscoelastic parameters, surface tension, and their dynamic response at the perturbed interface. To simplify the mathematical organization, viscous potential flow theory is adopted. Further reduction is achieved by coupling linearized governing partial differential equations with the applicable nonlinear interfacial boundary conditions. This formulation leads to a nonlinear Mathieu oscillator, which governs the evolution of interface displacement. By adopting a non-perturbative approach, the achieved nonlinear ordinary differential equation is transformed into an equivalent linear one. Numerical solutions to the derived stability conditions reveal that the fundamental stability behavior remains qualitatively identical to both the real and complex coefficients associated with nonlinear characteristic equations describing the movement of interfacial displacement. The findings demonstrate that the Darcy number negatively influences the stability region, whereas kinematic viscosities, the Weber number, and Ohnesorge number facilitate the system’s stabilizing impact. Full article

This study proposes a model-based method for real-time monitoring of the lubrication regimes in dynamically loaded radial sliding bearings using Physics-Informed Neural Networks (PINN). The proposed method replaces computationally intensive elastohydrodynamic lubrication (EHD) simulations with a PINN-based surrogate model. The model predicts hydrodynamic pressure and lubricant film-thickness distributions with comparable accuracy under dynamically varying operating conditions, enabling reliable assessment of lubrication regimes. The proposed model advances the state of the art in physics-informed modelling of mixed lubrication by extending existing approaches to simultaneously account for mixed-friction regimes through the Greenwood–Tripp contact model, transient operating conditions, and bearing surface deformation. Using only the bearing load and shaft rotational speed as inputs, the resulting hydrodynamic pressure field and corresponding lubricant film thickness can be monitored, enabling the direct assessment of the lubrication regime and potential wear risk. The proposed method is applied to a validated EHD model of a 30 mm sliding bearing test rig, where EHD simulation results are used to train, validate, and evaluate the model. The proposed framework achieved an average lubricant film-thickness prediction error of 2.34% and lubrication-regime classification errors of 7.8% and 8.2% for the static and dynamic validation cases, respectively. Furthermore, the computation time for the complete 18-time-step load case was reduced from approximately 35 h to 61.2 ms. Full article

Electrohydrodynamic (EHD) actuators offer a promising approach for active particulate matter (PM) control in heavy-duty and marine exhaust systems. However, continuous DC corona discharge often leads to excessive energy consumption and is susceptible to aerodynamic re-entrainment in high-velocity flows. This study introduces an idealized transient advection mechanism combining a macroscopic corrugated duct geometry with high-frequency pulsed EHD actuation. A fully coupled, time-dependent multiphysics model—integrating RANS turbulent flow, Poisson-Nernst-Planck space charge transport, and Lagrangian discrete particle tracing—was developed to analyze the physical kinetics of 0.2 µm soot particles. The results demonstrate that the corrugation troughs act as effective aerodynamic dead zones with partial electrostatic shielding, creating aerodynamic and electrostatic dead zones. During active microsecond voltage pulses (25 kV peak), intense Coulombic forces rapidly overcome turbulent drag, driving kinetic injection of particles into the corrugation troughs. During the resting phase, particles remain securely trapped by aerodynamic shielding, significantly mitigating the risk of aerodynamic re-entrainment under the simulated conditions. A comprehensive parametric analysis revealed that an optimized 500 Hz pulse with a 5% duty cycle maintains a robust 82.7% trapping efficiency. Compared to standard continuous DC precipitators, this pulsed actuation strategy requires an idealized active corona power of 15.3 mW. This study provides fundamental physical insights into transient EHD flows and establishes optimized design criteria for fundamental EHD transport models. Full article

Efficient thermal management of high-power electronic components has become a critical engineering challenge as power densities grow and device geometries shrink. Conventional solutions based on passive heatsinks and mechanical fans are increasingly inadequate in applications where noise, reliability, and compactness are paramount. This paper presents a comprehensive Computational Fluid Dynamics (CFD) investigation of ionic wind—an Electro Hydro Dynamic (EHD) phenomenon in which a corona discharge between asymmetric electrodes generates a directed airflow without any moving part—as an energy-efficient alternative for cooling high-power electronics. A fully coupled 2D Multiphysics model is developed in COMSOL Multiphysics, integrating electrostatics, ion transport (Nernst–Planck), Navier–Stokes fluid dynamics, and convective heat transfer. The 2D formulation, while computationally efficient and consistent with prior EHD modeling studies, neglects lateral jet spreading inherent to a real three-dimensional needle configuration and is therefore expected to overestimate peak impingement velocities; quantitative comparisons with experimental temperatures are interpreted with this limitation in mind. The study focuses on a needle–collector configuration applied to a heated aluminum plate representative of a high-power electronic component such as a Light Emitting Diode (LED), a power transistor, or a microprocessor die. Simulation results are indirectly validated against experimental data obtained by Schlieren optics on a high-power (Chip-On-Board) COB LED system. The ionic wind reduces the maximum surface temperature by 8.1 K and substantially attenuates the central hotspot, redistributing heat laterally. A systematic parametric study reveals that applied voltage and needle height above the heat source are the dominant design parameters, while an energy balance shows that the EHD jet directly evacuates approximately 1.8% of the generated heat—acting primarily as a surface convection enhancer rather than a bulk heat extractor. These findings provide quantitative design guidelines applicable to any power electronic component cooled by an EHD system. Full article

Journal bearings are prone to failure due to lubrication state degradation under extreme operating conditions. To address the unclear transition mechanism and undefined state boundaries under insufficient lubrication, a coupled tribological model of engine journal bearings was established. Through parameter analysis and dynamic failure mechanism study, the effects of radial clearance, temperature, rotational speed, load, and surface roughness on the lubrication state transition were revealed. The results indicate that radial clearance, oil temperature, rotational speed, applied load and surface roughness are all decisive factors for lubrication transition, and every parameter has its unique critical threshold; once exceeding the limit, the oil film integrity is damaged and the lubrication rapidly shifts from mixed lubrication toward boundary lubrication. After crossing critical thresholds, aggravated asperity contact further triggers continuous temperature rise and viscosity reduction, which may induce closed-loop thermal deterioration and eventually accelerate bearing failure. The research findings provide a theoretical basis for robust design and operational safety monitoring of journal bearings. Full article

Marine diesel engines generate high concentrations of sub-micron particulate matter (PM) that requires effective exhaust aftertreatment. While conventional wire-in-tube electrostatic precipitators (ESP) offer a low-drag solution, their practical efficiency is limited by particle re-entrainment at elevated flow velocities. This study investigates a novel application of corrugated cylindrical ducts—standard vibration-compensating couplings—as electrostatic collectors. A fully coupled two-dimensional axisymmetric COMSOL Multiphysics 6.4 model was developed, integrating turbulent flow (k–ε), electrostatics, ion charge transport, and particle tracing. Numerical results demonstrate that while smooth and corrugated geometries yield identical theoretical Deutsch–Anderson efficiency (61.1% at Uin = 0.5 m/s, the corrugated profile significantly suppresses re-entrainment. The corrugations reduce wall shear stress by a factor of 7.7 to 13.5 at flow velocities of 0.3–0.8 m/s, maintaining aerodynamic conditions below critical particle detachment thresholds. With a pressure drop penalty representing less than 6% of the localized corona power, these findings show that existing marine exhaust infrastructure can be repurposed as high-efficiency, low-re-entrainment particle collectors through the integration of cold plasma electrodes. Full article

The present work proposes a phase change material-based defrosting system (PCM-DS) for vapor compression refrigeration systems (VCRSs). The primary objective is to determine the optimal PCM mass and refrigerant mass flow rate required to melt 1 kg of accumulated evaporator ice. A steady-state macroscopic thermodynamic model, governed by global energy balances and driven by experimental boundary conditions, evaluates the VCRS in both cooling and defrosting operating modes. The PCM-DS is not installed on the experimental setup. The latter is used to obtain experimental data to be used as inputs in the steady-state model. Among the three candidates investigated (OM42, OM46, OM48), OM42 was selected for minimizing system mass and volume constraints. Results demonstrate that integrating the PCM-DS induces only a 3% reduction in the theoretical coefficient of performance (COP) compared with a 5.6% reduction in the case of using the electric heater defrosting (EHD). The core innovation of this work involves proposing and evaluating three distinct energy storage management strategies: unique superheating, unique bypass, and intermittent bypass. The results show that the highest COP is obtained for unique superheating (2.93), followed by unique bypass (2.82) and intermittent bypass (2.81). The work conducted proves the theoretical feasibility of such PCM-DS. Full article

Polyvinylidene fluoride (PVDF), one of the most promising flexible piezoelectric polymers bridging mechanical compliance and infrastructure-scale sensing, suffers from low intrinsic β-phase content that limits energy conversion efficiency. Two-dimensional MXene nanosheets offer a compelling solution, inducing β-phase crystallization through interfacial hydrogen bonding while preserving essential flexibility, yet conventional fabrication methods lack precise control over dipole alignment and suffer from percolation leakage at functional loadings. Herein, we report a process-structure synergistic strategy that combines EHD printing with an optimized serpentine structure to reconcile piezoelectric sensitivity with mechanical durability. By precisely tuning the MXene loading to 0.75 wt% (near but below the percolation threshold), the composite achieves a β-phase content of 71.91% and a piezoelectric sensitivity of 18.09 mV/kPa, while the serpentine design delivers a tensile strength of 21.97 MPa and 17.46% elongation at break. As a proof-of-concept, the sensor is deployed in a vehicle-responsive tunnel lighting system, withstanding cyclic heavy loads and achieving a 95.04% energy-saving rate compared to continuous operation. This work advances high-performance flexible piezoelectric composites for intelligent infrastructure applications. Full article

This study presents a numerical investigation of the influence of channel geometry on electrohydrodynamic (EHD) processes governing particle transport in electrostatic precipitators (ESPs). A conventional rectangular channel is compared with concave configurations using a coupled multi-physics model that accounts for gas flow, electric field distribution, ion transport, and particle migration across a wide particle-size range. The results show that geometric modification significantly alters ion transport and charge distribution within the ESP channel. Compared with the rectangular configuration, the concave profile enhances ion penetration and particle charging, leading to improved collection efficiency across the entire particle-size range. The improvement is particularly pronounced near the minimum-efficiency region for submicron particles. Specifically, near 0.1 μm, the collection efficiency increases from approximately 30% in the rectangular channel to approximately 50% for the higher-contraction concave configuration, representing an improvement of nearly 20 percentage points. A comparison with a Venturi-like contraction further shows that abrupt geometric contraction produces localized space-charge accumulation and reduces the effective charging region. In contrast, smooth concave shaping promotes a more distributed electrostatic interaction region, resulting in improved particle collection performance. Full article

This study presents an optimized numerical and empirical modeling framework for ionic wind-driven electrostatic precipitators designed for atmospheric particulate matter (PM) removal. While traditional particle tracing models in long ducts often suffer from transient evaluation errors (the “flight time paradox”), this work introduces a Fate-based Steady-state Evaluation (FSE) method. By coupling Electrostatics, Laminar Flow, and Particle Tracing in a high-fidelity 2D axisymmetric model, we achieved a baseline validation with a Mean Absolute Error (MAE) of 5.3% compared to experimental data (20 kV, 0.5 m/s). Furthermore, a non-linear regression engine based on a physical-exponential decay function was developed to provide real-time performance predictions. The resulting hybrid model demonstrates a high scientific reliability (R² = 0.98), establishing it as a robust tool for the design and optimization of air purification systems targeting fine atmospheric aerosols (0.1–3.0 μm). In addition, the proposed Fate-based Steady-state Evaluation (FSE) method eliminates transient bias commonly observed in long-duct Lagrangian particle simulations. This methodological improvement enables statistically consistent efficiency estimation for electrohydrodynamic filtration systems and can be applied to a broad class of Computational Fluid Dynamics (CFD)-based particulate capture studies. The developed framework enables rapid design optimization of compact electrohydrodynamic filtration systems and provides a practical alternative to computationally expensive full-scale Computational Fluid Dynamics (CFD) simulations. Full article

This study examines the electrohydrodynamic (EHD) behavior of air bubbles rising in deionized water under a non-uniform electric field, with particular emphasis on the influence of applied voltage (0.5–3.0 kV) and gas flow rates of 30 and 40 mL ${\min }^{-1}$ (corresponding to Reynolds numbers of $R{e}_g=107$–142) on bubble dynamics. High-speed imaging reveals bubbles with equivalent diameters in the range of $d_{eq}\approx 0.8$–3.5 mm, enabling a detailed characterization of their deformation, trajectory, and interfacial response under coupled hydrodynamic and electric stresses. At $R{e}_g=107$, bubbles exhibited stable vertical trajectories with negligible lateral displacement, whereas at $R{e}_g=142$, inertial and wake effects induced deviations. Increasing $B{o}_E$ reduced lateral displacement, restoring alignment with the electric field. Bubble rise velocities increased by ∼20–30% with applied voltage due to polarization-driven EHD forces. A transition from hydrodynamically dominated to EHD-dominated regimes was identified. While polarization forces govern the initial bubble motion under a strong electric field, bubbles progressively transition downstream to a hydrodynamic regime as the electric field weakens, reducing the influence of polarization effects. These findings provide quantitative insight into coupled hydrodynamic–electrohydrodynamic interactions and support the development of predictive models for controlling bubble trajectories, with implications for electrically tunable multiphase and microfluidic systems. Full article

Precise manipulation of two-phase flow in micro-confined electrowetting pixels is limited by contact angle hysteresis (CAH). To elucidate this non-equilibrium process, we establish a high-fidelity electrohydrodynamic (EHD) phase-field simulation framework. The model rigorously couples Navier–Stokes equations with molecular kinetic theory (MKT) to characterize energy dissipation at the three-phase contact line (TCL) and further integrates charge transport kinetics. Numerical results reveal CAH is driven by physical pinning and interfacial charge trapping, with the latter dominating interfacial retreat and causing significant residual displacement. Furthermore, analysis shows alternating current (AC) waveforms mitigate charge accumulation and promote depinning via micro-oscillations, minimizing the hysteresis loop compared to direct current (DC) waveforms. Additionally, an overdrive strategy utilizing a suprathreshold Maxwell stress pulse rapidly overcomes static friction. This strategy significantly improves transient dynamics, substantially reducing the time to reach 90% of the steady-state target from 19.6 ms (under standard DC waveform driving) to 7.4 ms. This work provides a comprehensive theoretical basis and design criteria for optimizing active driving strategies in optofluidic and digital microfluidic systems. Full article

Background: Machine learning (ML) holds great promise for genomic breeding value prediction in livestock and poultry, yet its application in layer breeding remains limited. Methods: In this study, we used whole-genome resequencing data from 834 Wenshui Luhua Green-Shelled (WLGS) laying hens to predict genomic breeding values for eight egg production and egg quality traits using multilayer perceptron (MLP), random forest (RF), and genomic best linear unbiased prediction (GBLUP). Model performance was evaluated via 10-fold cross-validation, and the effects of data type and single nucleotide polymorphism (SNP) density were examined. Results: Heritability analysis indicated moderate heritability for egg number (EN) at 0.327. Egg weight-related traits (EW-30W, EW-40W, and EHD-40W) exhibited high heritability (0.570–0.631), while eggshell strength (ESS-40W) and thickness (EST-40W) showed moderate heritability at 0.228 and 0.220, respectively. Model comparisons revealed that RF performed best for egg shape index (ESI-30W, 0.395) and most egg quality traits, whereas GBLUP yielded optimal results for egg weight traits, achieving prediction accuracies of 0.392 for EW-30W and 0.432 for EW-40W. Whole-genome resequencing data consistently outperformed 50K chip data across all models, with GBLUP improving EW-40W prediction accuracy by 24.9%. SNP density analysis further showed that GBLUP remained stable under low-density conditions, while MLP and RF progressively improved with increasing density, with RF demonstrating the most pronounced advantage at high densities. Conclusions: In summary, the GBLUP model is suitable for traits with high heritability and low-density marker scenarios, while the RF model demonstrates significant predictive advantages for egg production and specific egg quality traits under high-density conditions. This study provides scientific basis for model selection in the genomic selection program for laying hens. Full article

Introduction: The COVID-19 pandemic exposed structural weaknesses in European public health systems while simultaneously accelerating institutional and digital reforms at the European Union (EU) level. This study examines how the EU has evolved from reactive crisis management toward a governance paradigm conceptualized as transformative resilience, understood as the institutional capacity to anticipate, adapt, and structurally reconfigure health governance in response to systemic shocks. Methods: This study employs a structured qualitative policy analysis based on a purposive corpus of key EU legislative and strategic documents (2020–2025), complemented by a contextual review of selected EU-level indicators. The analysis focuses on reforms associated with the European Health Union, including the establishment of the Health Emergency Preparedness and Response Authority (HERA), the development of the European Health Data Space (EHDS), and the adoption of the Artificial Intelligence Act. Results: The findings indicate progressive consolidation of supranational coordination mechanisms, deeper integration of digital infrastructure into health governance, and strategic incorporation of health security into the EU’s broader security architecture. Rather than assessing policy effectiveness, the analysis documents a structural and regulatory shift toward anticipatory and embedded preparedness. Persistent challenges remain, including uneven implementation capacity across member states, disparities in digital maturity, and tensions between innovation and data protection. Conclusions: The EU’s post-pandemic trajectory reflects a distinctive governance model in which health security, digital sovereignty, and democratic safeguards are framed as mutually reinforcing dimensions of resilience within an increasingly complex risk environment. Full article

Background/Objectives: Ankylosing spondylitis (AS) has been associated with various comorbidities, including cardiovascular morbidity. Recent studies suggest that certain arrhythmias may be more frequent in AS patients than in the general population. The aim of this study was to analyze the prevalence of electric heart disorders (EHD) in patients with AS in real-world conditions and compare them with those reported in the general population. Methods: Descriptive cross-sectional study aiming to determine the prevalence of EHD in AS in pre-COVID-19 period. EHD were analyzed in a resting ECG and 24 h Holter monitoring. Additionally, the association between clinical and demographic variables was analyzed. Results: Among 121 patients with AS (62% men; mean ± SD age 54.6 ± 15.6 years; median [IQR] disease duration 14 (8–20) years), 18.2% presented any EHD, including 9.1% with supraventricular tachyarrhythmias (SVT) (5% atrial fibrillation [AF]) and 7.4% with atrioventricular block (AVB). Clinically relevant disorders (≥2nd-degree AVB or SVT) were observed in 9.9% of patients. In adjusted analyses, SVT was independently associated with older age and higher BMI, while any conduction delay and clinically relevant EHD were associated with age, hypertension, and disease-modifying antirheumatic-drug treatment duration. Comparisons with previous population-based studies showed similar data, with a non-significant trend toward higher AF prevalence in AS patients. Conclusions: There appears to be a trend toward a higher prevalence of arrhythmias in patients with AS in real-world conditions, which could have clinical and therapeutic implications. An association between EHD and pro-inflammatory conditions such as age and BMI was observed, supporting the hypothesis that underlying inflammation might contribute to increased arrhythmogenicity. Full article