Effect Of Aspect Ratio Research Articles

Probing the optical properties and toxicological profile of zinc tungstate nanorods.

Zinc tungstate is a semiconductor known for its favorable photocatalytic, photoluminescence, and scintillation properties, coupled with its relatively low cost, reduced toxicity, and high stability in biological and catalytic environments. In particular, zinc tungstate evinces scintillation properties, namely the ability to emit visible light upon absorption of energetic radiation such as x rays, which has led to applications not only as radiation detectors but also for biomedical applications involving the delivery of optical light to deep tissue, such as photodynamic therapy and optogenetics. Here, we report on the synthesis of zinc tungstate nanorods generated via an optimized but facile method, which allows for synthetic control over the aspect ratio of the as-synthesized anisotropic motifs via rational variation of the solution pH. We investigate the effect of aspect ratio on their resulting photoluminescent and radioluminescent properties. We further demonstrate the potential of these zinc tungstate nanorods for biomedical applications, such as photodynamic therapy for cancer treatment, by analyzing their toxicological profile within cell lines and neurons.

A size‐dependent energy‐based strain burst criterion

AbstractThis paper presents a size‐dependent energy‐based strain burst criterion linking strength, elasticity, fracture energies and specimen size effect with stress state due to changes in boundary conditions. It proposes the concept of a ‘Burst Envelope’, a surface in three‐dimensional principal stress space derived based on energy storing and dissipation characteristics of a rock sample, taking into account the size of the specimen and potential localised failure pattern. A scalar burst index is also proposed to quantify the bursting scale. To illustrate and verify its functioning, a numerical modelling framework based on the distinct element method and employing a new cohesive‐frictional contact model is used to perform virtual strain burst experiments under different polyaxial loading‐unloading scenarios, mimicking various underground excavation scenarios. The obtained results are in good agreement with the theoretical prediction of burst occurrence. On that basis, the variation of burst possibility and magnitude are investigated with key factors, including confinement level and the material's elastic, strength and fracture properties. The effect of the specimen's aspect ratio and size on the rock burst potential is elaborated and verified using virtual strain burst experiments, facilitating the linking of the proposed theoretical framework with the evaluation of in‐situ strain bursts in rock masses around underground openings.

Unfolding of shocked hydrodynamic instability at SF[formula omitted] elliptical interface: Physical insights from numerical simulations

The Richtmyer–Meshkov (RM) instability widely exists in variety of industrial and scientific applications, such as in inertial confinement fusion, astrophysics explosions, supersonic combustion, bubble dynamics and cavitation. This study investigates the unfolding physical phenomena of RM instability at SF6 elliptical bubbles using numerical simulations. In contrast to cylindrical bubble, both shocked horizontal/vertical-aligned elliptical bubbles with different aspect ratios are considered, emphasizing the aspect ratio effects on flow morphology, complex wave patterns, interface deformation, vorticity generation, and interface features. For this purpose, a two-dimensional system of compressible Navier–Stokes-Fourier equations for multicomponent flows are solved using by a mixed modal discontinuous Galerkin method. Numerical simulations illustrate that the aspect ratio of elliptical bubbles have a significant influence on the vortex dynamics and the associated RM instability flows in contrast to the cylindrical bubble. In horizontal-aligned elliptical bubbles, some additional complex waves pattern, including inward jet and secondary vortex rings are observed. While, in vertical-aligned elliptical bubbles, the interface between two primary vortex rings is always vertical and has a “hippocampus” appearance due to the enhancement of downstream velocity. The baroclinic vorticity due to misalignment of density and pressure gradients at interface affects the bubble deformation and induces the Kelvin–Helmholtz instability, which leads to turbulent mixing. It is observed that the complexity of the vorticity fields is enhanced with increasing aspect ratios. Further, these aspect ratio effects result in integral diagnostic of important spatially integrated fields, and various interface features.

Microfluidic flow tuning via asymmetric flow of nematic liquid crystal under temperature gradient

In this work, efficient microfluidic flow rate tuning based on the asymmetric flow of nematic liquid crystal 5CB under a horizontal temperature gradient is studied. Rectangular microchannels with the width of 100 μm are fabricated through soft lithography and treated with homeotropic surface anchoring conditions. Polarized optical microscopy is applied to explore the unique optical anisotropic characteristics of the nematic liquid crystal. The asymmetric velocity profiles in the microchannel are obtained by particle tracking velocimetry. The effects of temperature, flow rate, and aspect ratio on the velocity profile and split ratio of the asymmetric flow are quantitatively studied for the first time, while the mechanism of the flow asymmetry of the nematic liquid crystal is discussed. The results show that the asymmetric flow of the nematic liquid crystal occurs after the horizontal temperature gradient is applied, with the velocity in the heated region markedly higher than its counterpart. The split ratio of the asymmetric flow increases with the increase in the temperature gradient and the decrease in the flow rate. The aspect ratio influences the asymmetric flow through approaches of average velocity and surface anchoring strength, while the former is more distinct. The impacts of temperature gradient, flow rate, and aspect ratio on the flow asymmetry of nematic liquid crystals are caused by the coupling between physical properties, velocity field, and director field. Microchannels based on the asymmetric flow characteristics of nematic liquid crystals can act as a novel kind of temperature-controlled microvalve to achieve efficient microfluidic flow tuning.

Experimental investigation of the effect of slenderness ratio and retention time on the separation performance of a two-phase horizontal separator

This study investigates the effect of the slenderness ratio (L/D) on the performance of a three-phase separator for constant retention times in the oil phase. The research combines experimental measurements with statistical analysis. To determine the controlling parameters of separation efficiency. The experiments varied 4 independent variables: slenderness ratios (2:1, 4:1, and 5:1); total mass flow rates (2, 3, 4, 5, and 6 GPM); oil layer thickness (9 18 27 and 36 mm) and composition. In addition, the oil flow rate, as part of the total flow, was varied to allow the oil retention time to be held constant. Taguchi and full factorial statistical analysis methods were used to analyse the results. The performance was seen to increase with increasing slenderness ratio for constant retention time. This implies that the slenderness ratio has a positive effect on separation. However, this is not a simple relationship. The main independent variables that affect separation were identified as total flow and aspect ratio, but the interaction of flow rate and slenderness ratio can cancel each other out. The interaction of the oil layer and slenderness ratio is normally insignificant but becomes controlling when the aspect ratio and flow effect cancel each other out. The performance decreases as the oil layer thickness increases and the aspect ratio decreases. This indicates that separators with shorter and wider configurations are less efficient than those with longer and slimmer designs.

Effect of Frequency-Amplitude Parameter and Aspect Ratio on Propulsion Performance of Underwater Flapping-Foil.

The propulsion system is the core component of unmanned underwater vehicles. The flapping propulsion method of marine animals' flippers, which allows for flexibility, low noise, and high energy utilization at low speeds, can provide a new perspective for the development of new propulsion technology. In this study, a new experimental flapping propulsion apparatus that can be installed in both directions has been constructed. The guide rail slider mechanism can achieve the retention of force in the direction of movement, thereby decoupling thrust, lift, and torque. Subsequently, the motion parameters of frequency-amplitude related to the thrust and lift of a bionic flapping-foil are scrutinized. A response surface connecting propulsion efficiency and these motion parameters is formulated. The highest efficiency of the flapping-foil propulsion is achieved at a frequency of 2 Hz and an amplitude of 40°. Furthermore, the impact of the installation mode and the aspect ratio of the flapping-foil is examined. The reverse installation of the swing yields a higher thrust than the forward swing. As the chord length remains constant and the span length increases, the propulsive efficiency gradually improves. When the chord length is extended to a certain degree, the propulsion efficiency exhibits a parabolic pattern, increasing initially and then diminishing. This investigation offers a novel perspective for the bionic design within the domain of underwater propulsion. This research provides valuable theoretical guidance for bionic design in the underwater propulsion field.

Effect of aspect ratio on the metal flow behaviour during forming process: A numerical simulation approach

This paper presents results on the effect of aspect ratio on the flow stress of 42CrMo4 steel using Deform™ 3D Version 11 simulation software. The FEM simulation process conditions were upsetting temperature of 1000 °C and 10 s⁻¹ strain rate. The sample aspect ratios (height/diameter) varied within commonly used ranges during conventional Gleeble experimentations. The aspect ratio did not affect the flow stress behaviour during forming. Generally, the forming conditions influence the flow stress-strain field and distribution behaviour, causing inhomogeneous deformation. A negligible effect of aspect ratio on typical industrial forging process is only attainable between 1.0 and 2.0. The implications of the results for industrial forging are elucidated.

Comparative analysis of mechanical characteristics in masonry walls: impact of aspect ratios and opening percentages

In this research, we undertake an extensive investigation focusing on masonry walls with aspect ratios of one and two, both confined and unconfined, while also accounting for a range of opening percentages. Employing a combination of finite element analysis and a simplified micro-modeling approach, we meticulously scrutinized and validated several masonry wall with an objective to investigate effects of aspect ratios and varying percentages of openings on key seismic characteristics such as lateral capacity, stiffness, and failure modes. Results reveal that with openings, wall lateral stiffness reduced by up to 54%. For a 4% opening, aspect ratio 1.0 walls saw reductions of 53.9% (unconfined) and 26.0% (confined). Aspect ratio 2.0 walls experienced 50.8% (unconfined) and 52.3% (confined) reductions. Notably, confined aspect ratio 2.0 walls showed significant stiffness reduction compared to aspect ratio 1.0 walls. Results highlight aspect ratio one walls’ superior performance over aspect ratio two walls in both confined and unconfined conditions. A four-parameter logistic regression quantifies opening percentages’ impact on lateral stiffness. This equation aids design professionals, enabling cost-effective and sustainable decision-making before construction.

A simple refined plate theory for buckling problems of in-plane bi-directional functionally graded plates with porosity under various boundary conditions

In this article, a simple refined shear deformation theory that eliminates the use of a shear correction factor was presented for buckling analysis of in-plane bi-directional functionally graded (IBFG) porous plates under various boundary conditions. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. Material properties of IBFG are assumed to vary continuously along with two different directions simultaneously, that is, the longitudinal and transversal ones, respectively. Governing equations and boundary conditions are derived. Analytical solutions were obtained for buckling analysis of (IBFG) porous plates. Several numerical examples are presented to demonstrate the performance and effectiveness of the proposed theory. The effects of material gradations, aspect ratios, and porosity on IBFG plate responses are examined in detail as well.

Effect of aspect ratio on the unlimited flow-induced vibration of an elliptical cylinder-plate assembly

Effect of aspect ratio on the unlimited flow-induced vibration of an elliptical cylinder-plate assembly

Effects of Impact Energy and Aspect Ratio on the Motion of Particle Clouds in Stagnant Water

Abstract A series of laboratory experiments was conducted to investigate the effects of impact energy and other initial controlling parameters on the motion of particle clouds in stagnant water. Experiments were performed for two median sand diameters of D50 = 0.52 mm and 0.74 mm and nozzle diameters of do = 6 mm and 8 mm. Sand masses were converted to an equivalent pipe length with the same diameter as the nozzle, Lo, and a wide range of aspect ratios, Lo/do, between 2 and 93 was tested. The impact energy of sand particles was controlled by the release height of sand particles, and it was quantified by the non-dimensional release height, η, ranging from 1 to 21.5. It was found that particle clouds with higher impact energy had smaller concentration and velocity decay rates. This indicated that by increasing the release height, the momentum transfer between sand particles and the ambient water decreases. The time-series of instantaneous sand velocity were used to determine velocity fluctuations and turbulence intensity of sand particles and a direct correlation was found between sand velocity fluctuations and aspect ratio in particle clouds. The effects of impact energy on the anatomy of the resulted particle clouds were examined in this study. It was found that the cloud width increased dramatically when the impact energy of sand particles with high aspect ratios (i.e., Lo/do > 39) increased. Furthermore, the dispersion of sand particle began earlier as the kinetic energy of sand particles increased at the water surface.

Effect of particle aspect ratio in targeted drug delivery in abdominal aortic aneurysm

Aneurysm is a permanent irreversible bulge in the artery that can occur with higher prevalence among elderly individuals. Although invasive surgical procedures can prevent their development, they come with considerable side effects. Recently, treatments based on targeted drug delivery have gained a lot of attention to suppress aneurysm growth. Numerical simulations have been shown to be of great role in the prediction of blood hemodynamics and vascular wall behaviour in the case of an aneurysm. Moreover, the utilization of high-fidelity approaches such as the Lagrangian frame of reference can address the motion characteristics of microbubble (MB) contrast agents in particulate flows. This study aims to investigate the effect of particle aspect ratio on the adhesion of oblate spheroid particles to the vascular wall. Accordingly, a two-way fluid–structure interaction (FSI) method consisting of a hyperelastic material model for the vessel along with a non-Newtonian, compressible model for blood was employed to simulate an abdominal aortic aneurysm (AAA). Moreover, the ligand–receptor binding concept has been utilized to address the quantification of MBs adhesion. Five sets of aspect ratios ranging from 1 to 9 have been investigated and results indicated that with the increase of the aspect ratio the rate of adhesion decreases. Two drastic changes in the particle number occurred due to the diastolic peak and negative velocity profile, respectively. However, it was concluded that the hydrodynamic of the MBs in terms of velocity and wall distance is rather insensible to the particle shape.

Wetting of nanoscale water films on hierarchically structured surfaces

Surfaces with hierarchical structures significantly enhance the hydrophobic properties of solids, proving crucial for diverse applications including self-cleaning, anti-icing, and contamination prevention. In this study, we directly observe the dynamic wetting transitions of nanoscale water films on desirable textured surfaces decorated with dual-scale roughness between various wetting states encompassing Cassie–Cassie, Wenzel–Cassie, Cassie–Wenzel, and Wenzel–Wenzel states. Additionally, detailed information on the wetting of the water film on desirable textured surfaces decorated with dual-scale roughness is obtained using atomistic simulations in conjunction with sampling techniques. Through observation of the dynamic wetting transition, two common types of wetting pathways are directly captured, dubbed the preferential primary intrusion and secondary intrusions. The wetting follows which pathway is dependent on Hs/Ss of the small-scale roughness. The mechanisms behind the wetting transitions are revealed based on corresponding free-energy pathways. Moreover, the effect of aspect ratio and intrinsic contact angle on the wetting behavior has been studied. Subsequently, we construct a wetting phase diagram to exhibit all the possible outcomes and identify different wetting regimes. This work paves the way to understanding the wetting mechanisms on nanoscale textured surfaces with two-tier roughness, which can help to design a hydrophobic surface with superior robustness.

A case study on effect of twisting technique on heat transfer characteristics in a twisted oval helical tube

Efficient transfer of energy is an important issue addressed by numerous scholars in the literature and various methods have been proposed for enhancing the heat transfer efficiency in heat exchangers. Among many different heat exchangers, helical tubes are one of the most prevalent types of heat exchangers which have many applications in industry. In a case study, effect of twisting technique on the heat transfer in a helical tube with oval cross section has been investigated numerically and the results have been compared with simple circular cross section helical tube. Effect of cross section aspect ratio and twisting ratio in different flow Reynolds numbers has been considered. Results have been presented in terms of Nusselt number, friction factor, PEC, entropy generation and contours of velocity, streamlines and temperature. Results indicate that twisting technique can significantly enhance the heat transfer and all cases have PEC values of above unit which indicates superiority of this method. Also the velocity contours and streamlines indicate that using twisting technique result in higher mixing in the flow which is the reason for higher heat transfer characteristics in twisted oval helical tubes.

Parametric Decay of a Kinked Alfvén Wave Packet: 3D Magnetohydrodynamic Simulations

Large amplitude Alfvénic fluctuations, sometimes leading to localized inversions of the magnetic field, called switchbacks, are a common but poorly understood phenomenon in the solar wind. In particular, their origin(s), evolution, and stability within solar wind conditions are yet to be fully understood. Simulations modeling switchbacks have previously studied their stability in 2D. Here, we investigate the decay process of Alfvén wave packets via MHD simulations in 3D by characterizing the effects of system size, aspect ratio, and propagation angle on the decay rate. We show that the initial wave packet is unstable to parametric instabilities that develop compressible and Alfvénic secondary modes in the plane of, and transverse to, the initial wave packet propagation direction. The growth of transverse modes, absent in 2D simulations, increases the decay rate of the wave packet. We finally discuss the implications of our results for lifetime estimates of switchbacks and wave energy conversion in the solar wind.

Effect of Aspect Ratio, Rotation, and Eccentricity of Square Section Nested Thin-Walled Tubes on Their Energy Absorption Characteristics Under Quasi-Static Load

In this research, energy absorption characteristics of nested thin-walled aluminum structures with square cross-section have been investigated, and the effect of the three parameters: eccentricity, rotation, and tube aspect ratio on the energy absorption characteristics of the structure has been studied. The properties investigated were the specific energy absorption and crush force efficiency. An aluminum 1050 sheet was used to build the tubes. After making the samples and determining how the tubes were placed with each other, the structures were subjected to quasi-static axial loading. Also, for parametric investigations, the behavior of the structures was simulated using LS-Dyna software. The results showed that the simultaneous effect of the three desired parameters has increased the specific absorbed energy and the crushing force efficiency. When the tubes were at maximum eccentricity, the specific energy absorption and crushing force efficiency increased by reducing the aspect ratio and rotation angle. On average, the best sample’s specific energy absorption and crush force efficiency increased by 41.9% and 22.2%, respectively, compared to the single tube.

Investigation of the effects of volume fraction, aspect ratio and type of fibres on the mechanical properties of short fibre reinforced 3D printed composite materials

AbstractMechanical behaviour of 3D-printed composite parts is affected by the volume fraction, aspect ratio and type of fibre reinforcement. Although in the literature experimental approaches have been used to characterise the effects of the above factors on the mechanical properties of 3D printed parts, time and cost of the manufacturing process as well as the uncertainty associated with a large number of experimental techniques are the key issues. This study aims to address these challenges by developing a methodology based on a multi-scale Finite Element (FE) analysis of representative volume element (RVE) of 3D printed composite parts to predict the effective orthotropic properties. To account for the effects of fibre features, RVEs were modelled considering variables of volume fraction, aspect ratios and type of short fibres. To study the main and interaction effects of the above variables on the mechanical properties of 3D printed composite parts, a structured approach based on the Design of Experiments is used. The FE stress analysis of the RVE provides an understanding about the potential failure modes such as interfacial debonding between fibres and matrix, interlayer and intralayer delamination that may occur in load-bearing 3D printed composite parts. The FE computed mechanical properties are validated against experimental data through a series of mechanical testing of flexure, Iosipescu, and short beam shear which were conducted in conjunction with the Digital Image Correlation technique. As a result, certainty is obtained in using the proposed approach for a fast iterative design of 3D printed composite parts prior to industrial applications.

Numerical study of the effect of aspect ratio on the entropy generation due to Rayleigh–Benard convection in 2D trapezoidal cavity

The investigation of entropic variations in the thermal transport mechanism produced by buoyantly driven temperature gradients has attracted significant attention because of excellent physical significance. Therefore, the prime consent to manipulate the current investigation is to explore the impact of change in the aspect ratio of the trapezoidal cavity in the optimization of the entropy phenomenon. After attaining motivation from its practical essence different entropies including thermal, viscous, and local are estimated. Additionally, global quantities such as average Bejan and Nusselt numbers calculated along with total entropy are measured against flow concerning parameters (aspect ratio (AR), Rayleigh number (Ra) and irreversibility ratio (ϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi $$\\end{document})). Numerical experiments are performed by implementing a finite element approach using open-source software renowned as COMSOL Multiphysics. Before the accomplishment of the outcomes, confirmation of the numerical technique is assured by establishing grid sensitivity testing. Comparison of results between present and previous studies is also demonstrated. A wide range of involved sundry parameters varying from 10-4≤ϕ≤10-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{-4}\\le \\phi \\le {10}^{-2}$$\\end{document}, 102≤Ra≤105and0.25≤AR≤0.75\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{2}\\le {\ ext{Ra}}\\le {10}^{5} \\; {\ ext{and}} \\; 0.25\\le {\ ext{AR}}\\le 0.75$$\\end{document} are accounted. It is concluded that by escalating the aspect ratio from 0.50 to 0.75, the magnitude of the local entropy enhances from 3370 to 3424. It is revealed that the highest value of viscous entropy that is, 45, is achieved at Ra = 105 and by keeping the aspect ratio of enclosure equal to 0.75, whereas, the thermal entropy approaches 2 for the same situation of parameters. The magnitude of the average Bejan number reaches unity at AR = 0.5 and Ra = 105, whereas for low and high aspect ratios it depicts a magnitude less than 1 for the same Rayleigh number.

Computational study of aspect ratio and undulation effect on natural convection in an inverted T-shaped porous enclosure

This numerical study aims to enhance the convective thermal and fluid flow characteristics in an inverted T-shaped porous enclosure saturated with a water-based special fluid. Moreover, a Darcy-extended Brinkman-Forchheimer-based mathematical model is numerically simulated with a penalty finite element approach to analyze the influence of aspect ratio and undulation effect on the developed mathematical model. Firstly, the various aspect ratios ( Ar = 0.25 , 0.50 , and 0.75 ) of the mathematical model are numerically simulated at the varying range of Rayleigh number (Ra), which reveals that the increasing aspect ratios reinforce the convective heat and fluid flow phenomena. Moreover, it confirms the most pertinent aspect ratios (Ar = 0.50) that get superior results in reinforcing the convective flow among other aspect ratios. Furthermore, the optimal aspect ratio (Ar = 0.50) is further fixed to explore the parametric influences, including Rayleigh number ( Ra = 10 3 − 10 6 ), porosity value ( ϵ = 0.1 − 0.9 ), Darcy number ( Da = 10 − 5 − 10 − 2 ), and various undulation parameters such wave number ( n a = 5 , 9 , 15 ) and amplitude of wavy surface ( a = 0 , 0.050 , 0.125 , 0.250 ). The results reveal that augmenting Ra, Da, and ϵ reinforces the convective thermal and fluid transport characteristics. Moreover, a combined effect of undulation factors ( n a , a ) is also reported, indicating that decreasing na and increasing a magnitude strengthen the natural convection process. It is analyzed that the optimal combination of undulation parameters ( n a = 5 , a = 0.25 ) results in a 16.15% in heat transfer enhancement. Additionally, maximum enhancements of 32.55%, 6.63%, and 41.47% in Num are reported while comparing between na = 5 and na = 15 for Ra, Da, and ϵ. Similarly, maximum enhancements of 17.87%, 16.10%, and 37.77% in Num are reported when comparing between a = 0.05 with a = 0.25 for Ra, Da, and ϵ. The research contributes valuable insights into improving thermal transport processes in real-world applications, especially in industrial solar power collectors, thermal exchangers, and heat storage industries that utilize the T-shaped configuration.

Effect of urban street canyon aspect ratio on fire-induced air pollutants dispersion under cross wind

The incidence of vehicle fires in urban street canyons has continuously increased with the process of urban modernization. The dispersion and accumulation of fire-induced air pollutants seriously affect residents’ safety. The effects of the street canyon aspect ratio and fire source location on fire-induced air pollutants dispersion under cross wind were numerically investigated in the paper. The results show that the street canyon aspect ratio can affect flow patterns and vortex structure and then lead to different accumulation states of air pollutants. Smoke development can be divided into four different regimes according to cross wind velocity. The re-entrainment phenomenon occurs when the fire source is close to the windward building or in the center of the street, but it does not occur when the fire source is close to the leeward building. Smoke tends to accumulate in street canyons when the aspect ratio is smaller and the fire source is closer to the leeward building. The variation of critical velocity with the aspect ratio can be divided into three regions, i.e., initial linear growth region (0.5 ≤ W/H < 1), constant region (1 ≤ W/H ≤ 1.5), and second linear growth region (1.5 < W/H ≤ 2). The dimensionless critical velocity and critical Froude number are used to quantify the re-entrainment phenomenon in different fire scenarios, and prediction models are finally proposed. The main findings can provide a more detailed reference for urban layout and air pollution control to reduce fire-induced air pollutants.