Kang Luo

As the demand for thermal management under extreme heat fluxes increases, achieving simultaneous enhancement of the boiling heat transfer coefficient (HTC) and critical heat flux (CHF) has become a pressing challenge. As an active thermal management technique, electric-field-enhanced boiling features rapid response, low parasitic power consumption, and precise controllability, and has thus attracted extensive research interest. This review outlines the fundamental physical picture of boiling under an electric field, with emphasis on the origin of electrohydrodynamic (EHD) body forces and their role in bubble dynamics. It then systematically summarizes enhancement characteristics in dielectric liquids across three regimes: uniform electric fields, nonuniform electric fields, and strong-field conditions where free-charge effects become significant. The discussion then extends to conductive liquids and composite systems, covering major mechanisms including Maxwell stress, electrowetting, electrolysis, and electric-field-mediated regulation of nanoparticle migration, deposition, and resuspension. From a flow-physics perspective, electric-field-enhanced boiling is governed by the restructuring of bubble dynamics and the near-wall vapor-liquid distribution, while the net enhancement depends sensitively on fluid electrical properties, field configuration, surface morphology, and operating conditions. The paper concludes by highlighting future directions in mechanistic modeling, multiphysics diagnostics, and synergistic structural co-optimization. These directions may provide a useful reference for both fundamental studies and practical design.

Three-dimensional conjugate simulations of saturated HFE-7100 flow boiling in a rectangular mini-channel were performed within a C++-based open-source numerical framework incorporating the leaky dielectric model and wall nucleation. The effects of inlet velocity and the strength of the applied uniform vertical electric field were systematically investigated, revealing a pronounced dependence of the electric-field response on the flow condition. Under localized-dryout-dominated conditions, field-enhanced upstream vapor fragmentation accelerated liquid depletion and aggravated downstream starvation. Under convection-dominated conditions, sufficient liquid replenishment enabled the field to disrupt elongated wall-attached vapor structures and restore intermittent liquid contact with the heated surface. Proper orthogonal decomposition showed that strong fields concentrated vapor fluctuations into fewer dominant coherent structures under localized-dryout-dominated conditions, but weakened low-order coherence and distributed the fluctuations among more modes under convection-dominated conditions. Quantitatively, increasing the electric capillary number to 50 decreased the critical heat flux from 12.11 to 11.64 kW⁄m^2 at Re=1000, whereas the critical heat flux increased by 26.5% and 92.9% at Re=2000 and 4000, respectively. These findings identify the competition between electric-field-induced vapor reorganization and convective liquid replenishment as the governing mechanism of electric-field-regulated mini-channel flow boiling.

We perform a comprehensive linear non-modal stability analysis of plane Poiseuille flow in Oldroyd-B fluids, employing the recently proposed geometric decomposition of the polymer conformation tensor (Hameduddin et al. , J. Fluid Mech ., 2018, vol. 842, 395–427; J. Fluid Mech ., 2019, vol. 858, 377–406), where perturbation elastic energy has an appropriate definition. In the presence of weak shear flow, e.g. Reynolds number Re = 1, the spanwise-uniform disturbance with a large wavenumber exhibits the largest transient growth, and perturbation elastic energy is the most amplified, proportional to W ² (where W denotes the Weissenberg number), which is mainly attributed to the combination of different modes in the continuous spectrum (CS). Elastic energy analysis suggests that this growth is physically due to the energy transfer from the perturbation wall-normal velocity to the normal components of the perturbation polymer conformation tensor. As Re increases to Re = 1000, transient growth has a significant increase, and its maximum appears in the oblique disturbance with perturbation kinetic energy dominating amplification instead of elastic energy, which is still induced by the spanwise-uniform components of the input perturbation conformation tensor, just as in the Re = 1 case. Mathematically, this energy growth is caused by the combination of CS and the remaining discrete modes, and it is remarkably larger than that merely caused by CS. Kinetic energy analysis suggests that this significant kinetic energy growth is physically due to the fact that elastic effects enhance energy transfer from the base flow field and the perturbed conformation tensor field to the perturbed hydrodynamic field.

Neutronics–thermal coupling affects not only global reactivity but also the spatial relationship between heat generation and thermal response in heterogeneous reactor systems. This work presents a mechanism-oriented analysis of temperature feedback using a unified finite-volume SP3–heat-transfer framework on a common computational mesh. The neutronic solution provides the volumetric fission heat source, while the temperature field feeds back to macroscopic cross sections. Representative steady-state and transient reactor problems are constructed from standard benchmark configurations, and reference eigenvalue and flux comparisons are used only as a concise verification step. The main focus is placed on feedback-induced spatial mechanisms. Diagnostic quantities are introduced to characterize fuel-region power peaking, power–temperature hot-spot separation, dominant hot-region mismatch, relative power-density redistribution, and normalized power–temperature mismatch. The results show that temperature feedback can reshape local power and temperature fields, causing power redistribution, hot-spot migration, and non-monotonic power peaking. Apparent jumps in pointwise hot-spot distance are shown to originate from local peak switching between competing hot spots rather than discontinuities of the coupled fields. Transient results further reveal response lag associated with delayed neutron kinetics and thermal diffusion.

The operational stability of advanced solid-fuel reactors is governed by nonlinear bidirectional coupling between neutron transport and thermal-hydraulics. Conventional approaches often decouple these physics or rely on time-averaged turbulence models, thereby obscuring transient flow–neutron interactions. In this study, a high-fidelity finite-volume framework is developed to tightly couple neutron transport with direct numerical simulation (DNS). A composite state vector integrating velocity, temperature, and neutron flux is constructed, and synchronous Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) are applied for full-field reduced-order diagnosis. The results show that solid-fuel Doppler feedback is the primary stabilizing mechanism: through conjugate heat transfer at the solid–liquid interface, it suppresses power surges and drives divergent eigenvalues toward quasi-equilibrium or limit-cycle states. The neutron cross-section acts as a critical bifurcation parameter, inducing symmetry breaking and transforming ordered periodic structures into multi-scale fragmented vortices. Intensified convection broadens the dynamic energy spectrum and accelerates the transition to spatiotemporal chaos. These modal indicators and stability boundaries provide guidance for heat-removal design, operating-parameter selection, and early warning of thermo-neutronic instabilities in advanced reactor cooling systems.

Double-emulsion droplets subjected to electric fields are widely used in chemical, petroleum, and food-processing applications, yet the mechanisms governing their deformation and breakup are not well understood. In this work, a multi-component lattice Boltzmann method coupled with the leaky dielectric model is employed to investigate the electrohydrodynamic behavior of stationary component-a-in-component-b-in-component-a (a/b/a) compound droplets over a representative range of dielectric constant and electrical conductivity ratios. Four distinct breakup modes are identified, governed by the relative prolate–oblate responses of the inner and outer droplets. Droplets exhibiting asymmetric deformation are more susceptible to rupture than those undergoing symmetric deformation. In particular, breakup dominated by outer-droplet elongation requires a stronger electric field than that driven by inner-droplet elongation. At sufficiently high electric field strengths, concave deformation of the inner droplet promotes multi-fragment breakup of the outer droplet. These results provide physical insight into electric field-induced breakup in double emulsions and offer guidance for the design and control of droplet-based electrohydrodynamic processes.

Flow control and heat transfer enhancement represent critical research in the aerospace field, facing challenges such as complex environments, long-term thermal management requirements, low energy consumption, and high integration. As an emerging fluid-driven and thermal management technology, the electrohydrodynamic (EHD) pump is independent of gravity, and it demonstrates significant application potential. This study presents a modular EHD pump and systematically tests its flow control, heat transfer enhancement, and dynamic response characteristics. Experimental results indicate that as the applied voltage increases, the flow rate of the EHD pump increases significantly. At a heat flux of 10 000 W/m2, the enhancement efficiency of the pump reaches 107.59%. By constructing an energy consumption characteristic curve, the energy consumption of the EHD pump is evaluated, showing a maximum of 0.046 W at 10 kV. Dynamic response tests reveal that the startup and shutdown processes of the pump can be divided into four stages: initiation, progression, stabilization, and decay. Owing to its compact, gravity-independent, and modular design, the pump shows potential for use in spacecraft thermal management and compact electronic cooling systems.

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.