Study on the airflow velocity induced by stack effects and its influence on flame morphology of wall fires within a vertical channel

Asymmetric unstable natural convection in an open-ended vertical channel with hot-cold walls

In oil production and refining, high-capacity continuous settling tanks are used in wastewater treatment systems. Thin-layer settling tanks have a large settling area and ensure high performance. The small channel size ensures laminar fluid flow at higher fluid velocities, preventing the occurrence of vertical convective currents. Thin-layer settling tanks operating in co-current or counter-current modes are widely used. They have a simple design, are easy to manufacture, and are commercially available. However, they have disadvantages that limit their use. This article examines the development of thin-layer settling units with transverse sludge drainage. The modular design allows for factory fabrication, installation through manholes, and ease of installation, maintenance, and repair. Several internal design options for thin-layer settling tanks and the design of a thin-layer settling unit are discussed. All variants utilize inclined plates with upward and downward-facing edges. The plates form a system of troughs and vertical channels for sludge drainage. The plates are connected to each other using connectors or housed within a spatial frame. A thin-layer settling tank design has been developed and its effectiveness evaluated.

Room-temperature mid-infrared (MIR) photodetectors are crucial for a wide range of applications, including free-space communication, infrared countermeasures, and gas sensing. Recently, two-dimensional (2D) materials have emerged as promising candidates for next-generation MIR detection. However, simultaneously achieving high responsivity and fast response speed in 2D material-based MIR detectors remains challenging. Here, we demonstrate a high-performance vertical black phosphorus (BP) photodiode that integrates Schottky-contacted, plasmonic-resonated bottom electrodes with an ultrashort vertical channel. This design synergistically enhances the MIR light absorption area and carrier transport by spatially aligning the plasmonic hot spots with the Schottky junction, enabling efficient carrier generation and rapid extraction. Our proposed photodetector achieves a responsivity of 5 A/W, representing a two-order enhancement compared with the devices without plasmonic integration and corresponding to a specific detectivity of 5.0 × 109 cm Hz1/2 W-1. More importantly, it also achieves an ultrafast rise/decay time of 22/26 ns at 3.7 μm, setting a benchmark for room-temperature MIR photodetection in 2D material systems. This vertical device architecture, leveraging a high Schottky barrier height and strong localized electric fields induced by the plasmonic resonance, offers a scalable and promising strategy for high-performance room-temperature MIR photodetectors that simultaneously achieve a high photoresponse and ultrafast speed.

Complex stimuli such as two-tone stimuli (f1 and f2) elicit frequency-following responses that reflect phase-locking to the stimulus envelope (f2 - f1) and temporal fine structure at multiple stages of the auditory pathway, from the cochlea to the cortex. The relative contribution of these structures to the scalp-recorded envelope-following response (EFR) remains a matter of debate. Although subcortical sources have been proposed as the main contributors, near-field recordings close to the cochlea contain pre-neural components and have recently been reported in auditory steady-state responses (ASSRs), a version of the EFR used to measure thresholds at the four frequencies (0.5, 1, 2, 4 kHz) most relevant for objective audiogram estimations. The present study evaluated the EFR in 26 auditory neuropathy spectrum disorder (ANSD) cases and 79 children with normal electrophysiological thresholds and distortion product otoacoustic emissions (controls). In addition, this study presents data from a battery of auditory neurophysiological objective tests applied to the 26 ANSD cases. EFRs were recorded using horizontal (EFR-H) and vertical (EFR-V) channels and the generalized primary tone phase variation method, allowing isolation of the EFR waveforms in the time domain to obtain direct latency and phase-locking value (PLV) measurements. EFRs detected in ANSD cases were compared with those of the controls. The standard audiological objective tests included tympanograms, distortion product otoacoustic emissions, click-evoked auditory brainstem responses (ABRs), and ASSRs. EFR-H was detected in five ANSD cases, showing shorter onset latencies, shorter response durations, and lower PLVs than controls. Lower PLVs were also observed in the EFR-H from the contralateral ears of unilateral ANSD cases. The EFR-V was undetected in all ANSD patients except for two, who showed milder neural desynchronization in their click-evoked ABRs and exhibited the lowest ABR thresholds within the ANSD cases. In 15 ANSD cases, with totally absent neural click-evoked ABRs, ASSRs were detected for at least one tested frequency, indicating a discrepancy between ABR and ASSR-estimated thresholds. The EFR-H observations suggested a pre-neural origin, with the asymmetrical mechanoelectrical transduction process at the sensory hair cells as the main contributor. These findings provide further evidence of a pre-neural potential explaining the discrepancy between ABR and ASSR threshold estimations in ANSD. In addition, the results from the contralateral ears of unilateral ANSD cases may reveal subtle deficits typically undetected by standard audiological techniques. Overall, the study of noninvasive EFR recordings in ANSD may contribute to refining their diagnosis, ultimately improving their treatment.

Abstract This study investigates the impact of temperature-dependent viscosity on the unsteady magnetohydrodynamic flow of incompressible, electrically conducting Casson nanofluids containing single and multi-walled carbon nanotubes (SWCNTs and MWCNTs) dispersed in engine oil through a vertical Forchheimer porous channel. The model also accounts for the effects of the Péclet number, radiation, heat generation/absorption, and buoyancy. The governing coupled partial differential equations (PDEs) for momentum and thermal transport are numerically solved using the overlapping multidomain bivariate local linearization method. The influence of key parameters, including the Casson fluid index, variable viscosity, magnetic field, Forchheimer resistance, radiation, heat generation/absorption, Grashof number and Brinkman number are analyzed numerically. Velocity and temperature fields are enhanced by higher Casson parameter, viscosity variation, Grashof and Brinkman numbers, while they are reduced by magnetic, Forchheimer, radiation, and heat absorption effects. Overall, MWCNT nanofluids consistently demonstrate higher velocity, temperature, and Nusselt number, as well as greater entropy generation and lower Bejan number than SWCNT nanofluids.

The Lower North River (LNR) exhibits a distinctive anabranching pattern in the Pearl River Basin, China. However, research has predominantly focused on vertical channel adjustments relying on in situ measurements, while the large-scale spatiotemporal dynamics of the anabranching planform have received limited attention. To address this gap, this study quantified the evolution of the anabranching planform from 1990 to 2022 using remote sensing images, focusing on anabranching intensity and island morphology, and analyzed driving factors using hydrological observations. Results revealed three evolutionary phases driven by shifting dominance of human interventions. During the first phase (1990–2004), the LNR experienced a moderate decline in anabranching intensity and widespread shrinkage of river islands, primarily attributed to sediment starvation induced by upstream dams. In the second phase (2004–2013), the decline in anabranching intensity accelerated and the proportion of expanding islands increased, driven by unregulated sand mining and channel regulation. In the third phase (2013–2022), the rapid decline in anabranching intensity decelerated and the islands shifted from a shrinkage-dominated to a stable-dominated state following the implementation of strict mining management and the physical confinement imposed by engineering structures. These findings reveal distinct morphological responses of the LNR to flow–sediment regimes and anthropogenic physical interventions, offering insights into the sustainable management of large anabranching rivers worldwide in the Anthropocene.

Surface tension mediated fluid–structure interactions, or elasto-capillarity, play a pivotal role in a wide range of micro-fluidic applications, as well as in physiological flows. In this study, we analyze the capillary-driven transport of a Newtonian fluid in a thin, cylindrical, deformable microchannel. Through a reduced order model, we rigorously study the dynamics of capillary rise in the channel, highlighting the importance of wall elasticity. Both horizontal and vertical channels, as well as closed and open-ended capillaries are considered. The long-time oscillations in the capillary penetration length are studied through a linearized model. Elasto-capillary instabilities are demonstrated by means of a full-order computational model, whose results compare favorably with that of the analytical model. We showcase that the capillary walls deflect inwards on account of the Laplace pressure drop across the liquid–gas interface. Through a scaling estimate, we report that this deflection does not alter the scaling in both the initial inviscid as well as in the viscous Washburn regime, although it does decrease the Washburn coefficient. Additionally, we report a giant augmentation of the equilibrium (or Jurin) height with elasticity of the channel wall. Finally, we delineate parametric regimes that dictate the occurrence of near-Jurin height oscillations, highlighting a distinct suppression of the oscillations for softer channel walls. Our findings offer an alternative method of controlling both the dynamics of capillary-driven transport at the micro- and nano-scales, by fine-tuning the interplay between the surface tension induced deformability of the channel walls, fluid viscosity, and gas pressure.

The main objective of this study is to determine the energy efficiency of a sensible heat storage system employing a dense crushed stone bed in a vertical heat exchange channel, as well as a latent heat storage system using a phase change material based on paraffin T3, intended for greenhouse applications. To achieve this objective, several tasks were performed, including analytical and experimental investigation of heat transfer processes in thermal energy storage system elements using a greenhouse model, analysis of the temporal variation of temperature profiles and solar radiation intensity, and a comparative evaluation of the energy efficiency of phase change heat storage materials, represented by modified paraffin, and capacitive heat storage systems, represented by crushed stone. The most significant results demonstrate that the derived analytical relationships for calculating working medium temperatures adequately describe the physical process of heat accumulation when experimental heat transfer coefficients are considered. Heat exchange between the dense crushed stone bed and the water flow occurs with high intensity, with an average heat transfer coefficient of α = 80 W/(m²·K). The emissivity of the surface of paraffin-filled heat storage tubes was determined to be εp = 0.65. The significance of the results lies in defining conditions for efficient application of thermal energy storage systems in greenhouse practice. For thermal stabilization of the internal greenhouse volume, the use of modified paraffin T3 is recommended, as its heat storage efficiency is 7.5-9.3 times higher than that of a dense crushed stone bed.

Numerical study of local heat transfer characteristics of flow boiling in a vertical upward narrow rectangular channel

ABSTRACT Designing functional thin films with precisely controlled surface chemistry and smoothness is essential for achieving targeted interfacial properties. Here, we introduce a polymer‐chain insertion strategy to fabricate pore‐threaded films by grafting uniformly long polymer chains into the vertical channels of surface‐mounted metal–organic frameworks (SURMOFs). Using the highly oriented pillared‐layer Cu 2 (bdc) 2 (dabco) SURMOF grown by layer‐by‐layer deposition as a crystalline host, infiltration of polymer chains into its nanochannels allows systematic tuning of interfacial chemistry and water wettability. Insertion of hydrophobic n‐alkane chains effectively masks the polar framework surface, enhances water stability, and imparts strong hydrophobicity. Polymer incorporation leads to characteristic modifications in the X‐ray diffraction pattern, and infrared spectroscopy reveals chain alignment through shifts in CH‐stretching modes. Notably, films infiltrated with long tetracontane (C 40 H 82 ) chains exhibit lubricant‐free slippery behavior, enabling water droplets to slide off readily due to the combination of smooth surface morphology and the low surface energy of exposed hydrocarbon segments. This scalable approach provides an internally integrated method for tailoring SURMOF thin‐film properties, expanding their applicability in liquid‐repellent coatings, anti‐fouling surfaces, and separation technologies.

Hydrogen is widely regarded as an ideal clean-energy carrier, and its safe, efficient utilization is critical to the transition of modern energy systems. However, hydrogen's high diffusivity and flammability make leak monitoring an urgent safety imperative. Here, we propose and fabricate an optical hydrogen sensor consisting of gold core-palladium shell nanorod arrays embedded in porous anodic aluminum oxide (Au@Pd NRAs/AAO). The sensor harnesses near-field coupling between the nanorods' transverse localized surface plasmon resonance (LSPR) and a vertical Fabry-Pérot (F-P) cavity formed by the array, yielding a hybrid LSPR-F-P resonance that amplifies the response to refractive-index perturbations induced by palladium hydride formation in the shell. By combining simulations and experiments, we systematically investigate how geometric parameters govern performance and elucidate the enhancement mechanism. Experimentally, within 0-2 vol% H2, the sensor exhibits a sensitivity of 11.33 nm/% with excellent linearity. At 2 vol% H2, the response and recovery times are <20 s and <50 s, respectively, and the device shows outstanding repeatability and stability with no appreciable hysteresis or baseline drift. Numerical simulations further indicate that integrating silver nanodiscs (AgNDs) on the array surface opens a vertical plasmonic-coupling channel, improving the sensor response by ≈ 20.6% under the same hydrogenation conditions. Leveraging the mechanically robust, process-compatible anodic aluminum oxide (AAO) template, the device is compact and inherently immune to electromagnetic interference, making it promising for industrial safety monitoring and new-energy applications.

ABSTRACT Metal‐induced lateral crystallization (MILC) behaves differently in vertical and confined geometries compared with conventional planar layouts. In this work, we use MILC whisker‐based Monte Carlo simulations supported by experimental validation to analyze the distinct growth behavior of MILC in vertical and narrow structures. First, vertical structures exhibit reduced Ni contact area, fewer NiSi 2 whisker seeds, and a limited Ni supply, which collectively slow growth and shorten the maximum propagation length. Second, in narrow structures, constrained whisker trajectories increase the probability of entrapment, amplifying variability and restricting propagation. Finally, when these constraints coexist in vertical 3D NAND flash memory channels, experiments reveal a strong tendency toward premature termination and pronounced propagation scatter. To overcome these limitations, we propose and validate a plug‐type MILC structure that expands the Ni contact area in vertical 3D NAND flash memory, thereby increasing the number of seeds, preventing premature termination, and significantly enhancing both growth length and reliability. This study provides direct insight into how structural constraints in 3D NAND architectures influence MILC growth and offers practical guidelines for achieving optimized crystallization in vertical channel memory devices.

The relevance of this study is driven by the increasing requirements for the energy efficiency and indoor comfort of residential and public buildings, particularly in regions with extreme climatic conditions characterized by substantial daily and seasonal temperature fluctuations. Effective management of heat transfer through building envelopes has become a key factor in reducing energy consumption and improving indoor comfort. This paper presents the results of an experimental–numerical investigation of the thermal behavior of an adaptive exterior wall system with a controllable air cavity. Steady-state and transient simulations were performed for three envelope configurations: a baseline design, a design with vertical air channels, and an adaptive configuration equipped with adjustable openings. Quantitative analysis showed that during the winter period, the adaptive configuration increases the interior surface temperature by 1.5–2.3 °C compared to the baseline design, resulting in a 12–18% reduction in the specific heat flux through the wall. In the summer period, the temperature of the exterior cladding decreases by 3–5 °C relative to the baseline, which reduces heat gains by 8–14% and lowers the cooling load. Additional analysis of temperature fields demonstrated that the presence of vertical air channels has a limited effect during winter: temperature differences at the surfaces do not exceed 1 °C. A similar pattern is observed in warm periods; however, due to controlled air circulation, the adaptive configuration provides an improved thermal regime. The results confirm the effectiveness of the adaptive wall system under the climatic conditions of southern Kazakhstan, characterized by high solar radiation and large diurnal temperature variations. The practical significance of the study lies in the potential application of adaptive façades to enhance the energy efficiency of buildings during both winter and summer seasons.

Abstract This study investigates the linear stability of mixed convection&amp;#xD;flow of an Oldroyd-B viscoelastic fluid in a vertical porous channel&amp;#xD;subjected to differential heating. To understand how thermal properties&amp;#xD;influence stability, two representative Prandtl numbers, Pr = 0.7&amp;#xD;and Pr = 7 are considered. The governing equations for basic flow and&amp;#xD;generalised eigenvalue problem, based on the viscoelastic form of the&amp;#xD;volume averaged Navier-Stokes equations, are solved using a spectral&amp;#xD;collocation approach. The analysis shows that variations in Reynolds&amp;#xD;number strongly impact the critical Grashof number (Gr′), the propagation&amp;#xD;speed of disturbances, and the overall instability mechanisms.&amp;#xD;The results further highlight that flow stability is governed by a delicate&amp;#xD;balance between fluid elasticity, buoyancy-driven forces, and the&amp;#xD;permeability of the porous medium. The fluids with lower Prandtl&amp;#xD;number display a stronger sensitivity to elasticity effects and further,&amp;#xD;the fluid elasticity has significant impact on the disturbance convection&amp;#xD;patterns inside the channel. The nature of instability is commonly&amp;#xD;found to be thermal-bouyant for the range of parameters considered&amp;#xD;in this study.

Oscillating piezofan effects on natural and forced convection flow in a vertical channel with protruding heat sources

This study presents a low-cost, scalable needle-templated method to fabricate a D1.4N8-GSA evaporator with vertical channels, achieving high evaporation efficiency and rate, superior to evaporators fabricated by unidirectional freezing.

Salt-resistant composite aerogel with vertical channels and low enthalpy for continuous solar desalination

Explainable critical heat flux prediction in vertical circular channels by self-attention-enhanced one-dimensional convolutional neural networks

A highly defective porous carbonized wood membrane (hd-CWM) is developed as a free-standing supercapacitor electrode with high areal capacitance, excellent rate capability, and exceptional durability.