Velocity Spread Research Articles

Varying Heat Release Rates per Unit Area – The Impact in Underground Mines

Abstract The fire behaviour and smoke behaviour of a fire in an underground mine will be largely dictated by the heat release rate of the fire. The heat release rate per unit area is generally the output from small-scale fire experiments and can be applied for larger objects with varying surface area. This paper studies the impact of varying heat release rate per unit area for fires in materials and substances typically found underground. Data from earlier fire experiments were analysed and discussed, and several different heat release rate curves and flame spread velocities for various fuel components were developed and discussed. It was found that the hydraulic hose presented the highest peak heat release rate per unit area of the solid fuel items, followed by the low-voltage cable, cab interior, and tyre in descending order. The increase in the peak heat release rate was highest for the highest incident heat flux levels, representative for scenarios underneath a mining vehicle. The heat release rate per unit area of pool fires underneath a vehicle is significantly higher than a corresponding free burning case - attributed to the higher incident heat flux – but a gravel surface underneath a pool fire will reduce the heat release rate considerably. Line fires in larger bundles of electrical cables were modelled and found to attain the peak flame spread velocity more rapidly compared with a fire in hydraulic hoses. This was caused by the higher heat release rate of the initial fire and ignited segments in the electrical cable case.

Impact behaviors of a single aqueous solution droplet on curved surface filler

Chemical absorption is one of the main methods for capturing and absorbing CO2 in post-combustion flue gases. The impact behaviors of the absorbent droplets on the filler have significant effects on CO2 absorption as the absorbent is sprayed down. However, the driving mechanisms behind these behaviors are not fully understood due to the increased difficulty in the absorption tower. In the present study, we numerically investigate the impact behavior of the CO2 absorbent droplet on the curved surface filler. The developed three-dimensional model is validated by our experimental results and previous studies. The driving mechanisms are revealed by focusing on the velocity and pressure field in different stages. The influence of the surface curvature and Weber number is analyzed, with particular attention to the evolution velocity. The liquid film oscillation is characterized by its amplitude and time for different surface hydrophobicity. The results show that the spreading of the liquid film is primarily influenced by the initial inertia, while its retraction and oscillation are mainly controlled by the surface tension and viscosity, leading to a longer retraction and oscillation time. Both pressure and velocity, as well as their peaks, exhibit different distributions depending on the behaviors in different stages. This is similar to the formation of the surrounding air vortex with its center above the gas–liquid interface in different stages. Both the Weber number and the curvature have little effect on the average spreading velocity, whereas the dimensionless maximum spreading diameter vs the Weber number follows a power law dependence. The results are helpful for understanding the physical mechanisms behind the impact behaviors of the CO2 absorbent droplets on the curved surface filler.

Host galaxies of ultra-strong Mg ii absorbers at z ∼ 0.7

ABSTRACT We report spectroscopic identification of the host galaxies of 18 ultra-strong Mg ii systems (USMg ii) at 0.6 ≤ z ≤ 0.8. We created the largest sample by merging these with 20 host galaxies from our previous survey within 0.4 ≤ z ≤ 0.6. Using this sample, we confirm that the measured impact parameters ($\rm 6.3\leqslant D[kpc] \leqslant 120$ with a median of 19 kpc) are much larger than expected, and the USMg ii host galaxies do not follow the canonical $\rm {\it W}_{2796}-{\it D}$ anticorrelation. We show that the presence and significance of this anticorrelation may depend on the sample selection. The $\rm {\it W}_{2796}-{\it D}$ anticorrelation seen for the general Mg ii absorbers show a mild evolution at low $\rm W_{2796}$ end over the redshift range 0.4 ≤ z ≤ 1.5 with an increase of the impact parameters. Compared to the host galaxies of normal Mg ii absorbers, USMg ii host galaxies are brighter and more massive for a given impact parameter. While the USMg ii systems preferentially pick star-forming galaxies, they exhibit slightly lower ongoing star-forming rates compared to main sequence galaxies with the same stellar mass, suggesting a transition from star-forming to quiescent states. For a limiting magnitude of mr < 23.6, at least 29 per cent of the USMg ii host galaxies are isolated, and the width of the Mg ii absorption in these cases may originate from gas flows (infall/outflow) in isolated haloes of massive star forming but not starbursting galaxies. We associate more than one galaxy with the absorber in $\ge 21~{{\ \rm per\ cent}}$ cases, where interactions may cause wide velocity spread.

Low glycemic index diet restrains epileptogenesis in a gender-specific fashion

Dietary restriction, such as low glycemic index diet (LGID), have been successfully used to treat drug-resistant epilepsy. However, if such diet could also counteract antiepileptogenesis is still unclear. Here, we investigated whether the administration of LGID during the latent pre-epileptic period, prevents or delays the appearance of the overt epileptic phenotype. To this aim, we used the Synapsin II knockout (SynIIKO) mouse, a model of temporal lobe epilepsy in which seizures manifest 2–3 months after birth, offering a temporal window in which LGID may affect epileptogenesis. Pregnant SynIIKO mice were fed with either LGID or standard diet during gestation and lactation. Both diets were maintained in weaned mice up to 5 months of age. LGID delayed the seizure onset and induced a reduction of seizures severity only in female SynIIKO mice. In parallel with the epileptic phenotype, high-density multielectrode array recordings revealed a reduction of frequency, amplitude, duration, velocity of propagation and spread of interictal events by LGID in the hippocampus of SynIIKO females, but not mutant males, confirming the gender-specific effect. ELISA-based analysis revealed that LGID increased cortico-hippocampal allopregnanolone (ALLO) levels only in females, while it was unable to affect ALLO plasma concentrations in either sex. The results indicate that the gender-specific interference of LGID with the epileptogenic process can be ascribed to a gender-specific increase in cortical ALLO, a neurosteroid known to strengthen GABAergic transmission. The study highlights the possibility of developing a personalized gender-based therapy for temporal lobe epilepsy.

Experimental study and numerical simulation of the combustion characteristics of dust clouds in vertical pipelines underneath unilateral obstacles

To reveal the impact of unilateral obstacles on the combustion characteristics of dust clouds inside vertical pipelines. This paper uses high-speed photography to conduct research on the combustion of vertical dust clouds using a self-designed experimental platform. A numerical model is established using Fluent to numerically simulate the combustion process. The results show that obstacles can increase flame spread velocity inside the pipeline, leading to an increase in peak temperature. As the blockage ratio of the obstacles increases, the flame profile becomes increasingly distorted. The maximum flame spread velocity and temperature initially increase and then decrease, with the maximum flame spread velocity reaching further away from the pipeline outlet. At the same time, high blockage ratios can lead to the accumulation of dust concentration underneath obstacles, resulting in a continuous turbulent reaction. As the number of obstacles increases, the maximum flame spread velocity and temperature gradually increase, and the maximum flame propagation ratio is closer to the pipeline outlet. The experiment and the flame propagation procedure (as calculated by numerical simulation) are consistent. The discrepancy between the simulated results and the experimental results is < 15 %.

Observational Evidence of the Merging of Filaments and Hub Formation in G083.097+03.270

We uncover a hub–filament system correlated with massive young stellar associations in G083.097+03.270. Diagnosed with simultaneous 12CO, 13CO, and C18O line observations, the region is found to host two distinct and elongated filaments having separate velocity components, interacting spatially and kinematically, that appear to have seeded the formation of a dense hub at the intersection. A large velocity spread at the hub, in addition to a clear bridging feature connecting the filaments in velocity, indicate the merging of filaments. Along the filament axis, the velocity gradient reveals a global gas motion with an increasing velocity dispersion inward to the hub signifying turbulence. Altogether, the clustering of Class I sources, a high excitation temperature, a high column density, and the presence of a massive outflow at the central hub suggest enhanced star formation. We propose that the merging of large-scale filaments and velocity gradients along filaments are the driving factors in the mass accumulation process at the hub that have sequentially led to the massive star formation. With two giant filaments merging to coincide with a hub therein with ongoing star formation, this site serves as a benchmark for the “filaments to clusters” star-forming paradigm.

Effect of Beam Velocity Spread With Spatial Variation on Mode Excitation in Gyrotrons

Effect of Beam Velocity Spread With Spatial Variation on Mode Excitation in Gyrotrons

Investigation of droplet impact dynamics on textured cylindrical hydrophobic surfaces

In this experimental investigation, a study of water droplet dynamics has been performed on a semi-hierarchical textured cylindrical target. Three different textures, viz. cycloid, sawtooth, and triangular, with amplitude of 300 µm and time-period of 600 and 800 µm, were fabricated on a Nickel-Titanium alloy through the Wire Electrical Discharge Turning process. The contact angle of the textured samples improved drastically compared to the as-received samples and was related to the roughness factor (r). The spreading in the axial direction has been studied for the various textures, and it was observed that the textures significantly reduce the maximum spreading diameter compared to the smooth cylinders. Furthermore, the experimental investigation revealed splashing in the case of textured samples and deposition in the case of as-received samples at α ≥ 38.8, indicating r, along with diameter ratio, D* , plays a critical role in determining the splashing zone. Accordingly, a regime map has been plotted between r and α, and a critical curve in the form of hyperbolic function was observed. The average velocity of spreading and receding was calculated, and the spreading velocity was 3–5 times higher than the receding velocity. Finally, a model has been developed based on data-driven machine learning, which was in good agreement with the previous experimental investigations.

Enhancement of heat transfer by flowing turbulent jet on a linearly decaying (LD) wavy wall

The influence of a partial linearly decaying (LD) wavy wall on different fluid flow and thermal parameters has been investigated for the turbulent jet. For the present study, a segment of wall from the leading edge is made with a constant amplitude 0.8a (a = nozzle height), followed by a segment of LD wavy wall. In the region of LD wavy wall, the amp (amplitude) of wavy wall is linearly reduced from 0.8a amplitude to 0a in the downstream direction. The LD wavy wall segment varies from 100% to 0%. For 100% LD wavy wall, the whole wall is made of linearly decaying amplitude, whereas for, 0% LD wavy wall, the whole wall is made wavy with a constant amplitude. The Reynolds number at the inlet is same for all the cases, i.e. 15,000 to maintain the fully turbulent condition at the exit of nozzle. The problem is solved numerically using k−ε RNG model. The results obtained from this study show that for 100% LD wavy wall the velocity decay is minimum and as the % of LD wavy wall decreases, the velocity decay increases. Whereas the thermal decay of jet is maximum in the case of 100% LD wavy wall. Similarly, Ymax, YTmax, and the velocity and thermal jet spread are found to be minimum for the 100% LD wavy wall and all these parameters increase as the % of LD wavy wall decreases. The maximum increment in the heat transfer rate is 27.9% for 100% LD wavy wall in regards to the baseline case (plane wall). However, the maximum increment in thermal hydraulic performance (THP) is noticed for the wavy wall with 50% LD wavy wall, which is equal to 6.7%. In a previous study (ArchanaKumari, 2021 [1]), the increment of 19.0% and 5.3% is observed for the heat transfer and THP respectively. In the present study by introducing LD wavy wall, the increment in the heat transfer and THP are quite significant.

Enhancement of flame spread and droplet dynamics behavior of biodiesel constituents with ethanol and MWCNT-OH additions

The interactive droplet combustion between three adjacent droplets of biodiesel constituents was investigated to obtain flame spread and droplet dynamics behavior enhancement with ethanol and hydroxyl-functionalized multi-walled carbon nanotubes (MWCNT-OH) additives. The experiment was conducted at atmospheric pressure and under normal gravity using spatial and temporal tracking. This study found that ethanol effectively increases flame spread velocity and shortens droplet heating time at a close droplet distance. Meanwhile, MWCNT-OH shortens flame spread induction time at a large droplet distance when thermal conduction time mainly controls the flame spread. Both additives improve the volatility and thermal conductivity of fuel blends, extending the flame spread limit distance with strong reciprocal interaction between droplets and accelerating combustion with a higher burning rate. Different flame spread mechanisms were observed and determined by the fuel additives. Child droplet ejection and microburst flame encourage rapid ignition and flame spread to the next unburned droplet. The puffing and microexplosion mechanisms of the fuel blends were determined by the nucleation type preceding the child droplet ejection. Combining ethanol and MWCNT-OH as fuel additives is the most effective way to improve combustion and flame spread performance because ethanol induces nanoparticle burns at the earlier combustion stage.

A linear parameters study of ion cyclotron emission using drift ring beam distribution

Ion Cyclotron Emission (ICE) holds great potential as a diagnostic tool for fast ions in fusion devices. The theory of Magnetoacoustic Cyclotron Instability (MCI), as an emission mechanism for ICE, states that MCI is driven by a velocity distribution of fast ions that approximates to a drift ring beam. In this study, the influence of key parameters (velocity spread of the fast ions, number density ratio, and instability propagation angle) on the linear MCI is systematically investigated using the linear kinetic dispersion relation solver BO (Xie 2019 Comput. Phys. Commun. 244 343). The computational spectra region considered extends up to 40 times the ion cyclotron frequency. By examining the influence of these key parameters on MCI, several novel results have been obtained. In the case of MCI excited by super-Alfvénic fast ions (where the unique perpendicular speed of fast ion is greater than the perpendicular phase velocity of the fast Alfvén waves), the parallel velocity spread significantly affects the bandwidth of harmonics and the continuous spectrum, while the perpendicular velocity spread has a decisive effect on the MCI growth rate. As the velocity spread increases, the linear relationship between the MCI growth rate and the square root of the number density ratio transitions to a linear relationship between the MCI growth rate and the number density ratio. This finding provides a linear perspective explanation for the observed linear relation between fast ion number density and ICE intensity in JET. Furthermore, high harmonics are more sensitive to changes in propagation angle than low harmonics because a decrease in the propagation angle alters the dispersion relation of the fast Alfvén wave. In the case of MCI excited by sub-Alfvénic fast ions (where the unique perpendicular speed of fast ion is less than the perpendicular phase velocity of the fast Alfvén waves), a significant growth rate increase occurs at high harmonics due to the transition of sub-Alfvénic fast ions to super-Alfvénic fast ions. Similarly, for MCI excited by greatly sub-Alfvénic fast ions (where the unique perpendicular speed of fast ion is far less than the perpendicular phase velocity of the fast Alfvén waves), the growth rate at high harmonics also experiences a drastic increase compared to the low harmonic, thereby expanding the parameter range of the velocity spread.

Real-time three-dimensional micro-imaging of liquid front in spreading sessile droplet under transient spreading states.

Dynamic wetting behaviors of sessile droplets on substrates play crucial roles for various industrial chemical processes. In the case of complete wetting, it has been proposed that a precursor film which is nanometer-order thickness and micrometer-order length further expands outside the macroscopic contact line of the sessile droplet. While the time evolution of the precursor film is believed to strikingly affect the macroscopic wetting behavior (e.g., spreading velocity), it had been hard to visualize the three-dimensional shape of the precursor film at the early stage of wetting. Further, although the spreading velocity rapidly decreases upon time at the early stage of the wetting (transient state) and then converged to be a constant at later time (steady state), conventional fluid mechanics theories generally describe only the wetting behavior at the steady state. Therefore, experimental observation of time evolution of the precursor film shape in the transient state is essential to proceed the theories to the next step. Here, a monochromatic laser interference microscope was developed to visualize three-dimensional shape of the wetting front of sessile droplets in real time. By detecting an interference of the laser reflected at the liquid and substrate surfaces, the precursor film was successfully visualized with a time resolution of 20ms and a thickness resolution of about 3.5nm at worst. For 10 cSt silicone oil on Si substrate, a 60-nm-thick and 70-μm-long precursor film was observed for 2-10min after dropping and its spreading velocity which decreased with time was quantitatively analyzed.

An exploratory investigation into moisture content and wind impact on the fire behaviour of modular living walls

Vertical greenery systems (VGS) consist of vegetation biomass and organic materials as well as plastics or metal elements in supporting systems. In this work, we investigate fire properties of live and dead plants as part of complete VGS systems (living walls, LW). Small-scale tests using a cone calorimeter and medium-scale tests using the SBI method were used to determine reaction to fire properties. Full-scale experiments were carried out to approximate the flame spread with and without wind along a living wall. Highly moist plants lead to slower spread of the fire, but have not prevented spreading the fire on the plastic potting, which in all cases was eventually involved in the fire and burned down to a collapse. On dry vegetation and without wind, the vertical flame spread velocity was up to 90 cm/s, and horizontal up to 2.7 cm/s. Wind conditions have changed the living wall fire performance, accelerating the fire spread on the vegetation and the fire of plastic potting as well. For moist samples in PN-B 02867 test the test duration (until full destruction of the facade) was 2100 s without and 1150 s with wind. For dry samples, this was 1350 s and 590 s, respectively.

Genetic and sporadic forms of tauopathies-TAU as a disease driver for the majority of patients but the minority of tauopathies.

Ageing-associated tauopathies like frontotemporal dementia (FTD), variants thereof (like progressive supranuclear palsy (PSP), pick diseases (PiD), corticobasal degeneration (CBD)), and of course the most prevalent form of dementia, Alzheimer Disease (AD), are widely recognized forms of tauopathies. The list of tauopathies is expanding. We now include: (i) tauopathies where the disease cause or trigger is clearly either physical, such as in Traumatic Brain Injury (TBI) or Chronic Traumatic Encephalopathy (CTE), and (ii) genetic diseases that result in tauopathy but have pathogenic genetic variants in genes not related to TAU. Examples of the latter are myotonic dystrophy Type 1 and Type 2 (DM1, DM2, due to pathogenic genetic variants in the genes DMPK and CNBP, respectively), Niemann-Pick Disease Type C (NPD, due to mutations in NPC1 or NPC2), Kufs Disease (CLN6), Christianson Syndrome (SLC9A6), familial forms of Parkinson Disease (PD), and many others. In terms of affected brain regions and cell types, intracellular distribution of TAU pathology/aggregates, age of disease onset, velocity of disease progression and spreading of TAU pathology, there is, however, little in common in most of these disease entities. Here, I reason that TAU/MAPT is causative for the minority of tauopathies (e.g., MAPT-related FTD/PSP and Vacuolar Tauopathy (VCP)) and a critical mediator for others, like shown by overwhelming evidence for AD. However, TAU may also be a mere bystander or even protective in other settings. Improved understanding of rare tauopathies is necessary to develop specific treatments, but also to improve our understanding of the pathomechanistic role of TAU and to identify diseases that may profit from TAU-based therapies.

Design and verification of a backward wave oscillation suppression circuit for the Ka-band gyrotron travelling-wave tube.

Backward wave oscillation seriously degrades the stability of gyrotron travelling-wave tubes (gyro-TWTs), especially during high average/continuous wave operation. To solve this problem, a selective mode suppression structure (SMSS) based on the mode coupling principle is proposed and applied in the nonlinear beam-wave interaction region to suppress the parasitic TE11 mode. It is capable of obtaining a high power and improving the tube stability. Simulation results demonstrate that the SMSS can raise the starting current from 10 to 18A and the starting pitch factor from 1.2 to 1.6. Based on this proposed circuit, a Ka-band TE01 mode gyro-TWT was designed, and the particle-in-cell simulation shows that it can achieve a saturated output power of over 150 kW from 29.7 to 31.7GHz with a velocity spread of 2.2%. For verification, a SMSS is manufactured and cold tested. The measurement of S-parameters reveals that it can effectively suppress the parasitic TE11 mode.

Developing a novel ultrasonic atomization-based cutting fluid spray system and evaluating its performance during milling processes

Cutting fluid has been widespread in the metal cutting industry due to its cooling and lubrication properties. However, the excessive application of cutting fluids can lead to significant environmental issues and raise machining costs. Recently, the ultrasonic atomization-based cutting fluid (UACF) spray using minimum quantity has shown superior cooling and lubrication performance during machining processes, while the precise management of UACF spray and its influence on machining performance requires further comprehension. In this case, this paper developed a novel ultrasonic atomization-based cutting fluid (UACF) spray system, featuring a specialized nozzle unit that included an internal droplet nozzle and an external gas nozzle. Subsequently, the dynamics of droplet impingement on a rotated surface were analyzed, and the spray characteristic parameters were investigated. Then, comparative milling experiments were conducted under different cooling conditions, including dry cutting, flood cooling, high-pressure air cooling, and UACF. The influence of these cooling conditions on machining performance was investigated, in terms of cutting force, temperature, surface roughness, and chip morphology. The results obtained indicate that the critical velocity of droplet spreading was dependent on the cutting fluid properties, ultrasonic frequency, and velocity of the rotated surface. The droplets generated by ultrasonic atomization follow a Gaussian distribution. Flood cooling and UACF exhibit similar effects in reducing cutting force, temperature, and surface roughness due to the efficient penetration of liquid film into tool-workpiece interfaces. Additionally, UACF can significantly reduce the consumption of cutting fluid by up to 98.5 % compared to flood cooling. The effective cooling and lubrication in UACF can improve the surface quality and suppress machining vibration. Moreover, the appropriate droplet velocity can ensure the formation of a thin film on the tool surface, thereby enhancing cooling and lubrication performance in the UACF process.

The diffusion metrics of African swine fever in wild boar

To control African swine fever (ASF) efficiently, easily interpretable metrics of the outbreak dynamics are needed to plan and adapt the required measures. We found that the spread pattern of African Swine Fever cases in wild boar follows the mechanics of a diffusion process, at least in the early phase, for the cases that occurred in Germany. Following incursion into a previously unaffected area, infection disseminates locally within a naive and abundant wild boar population. Using real case data for Germany, we derive statistics about the time differences and distances between consecutive case reports. With the use of these statistics, we generate an ensemble of random walkers (continuous time random walks, CTRW) that resemble the properties of the observed outbreak pattern as one possible realization of all possible disease dissemination patterns. The trained random walker ensemble yields the diffusion constant, the affected area, and the outbreak velocity of early ASF spread in wild boar. These methods are easy to interpret, robust, and may be adapted for different regions. Therefore, diffusion metrics can be useful descriptors of early disease dynamics and help facilitate efficient control of African Swine Fever.

Theoretical analysis of convective transport over a slender body of revolution

The study of thermal transport in the laminar boundary layer had been a great area of research since long ago because of its practical necessity in different fields of engineering such as aerodynamics, electronics cooling, designing of turbine blades, etc. The primary goal of the research has always been to look into geometries or shapes that have higher heat transfer rates but a less viscous drag. This is also a topic of fundamental interest to the aerospace industry. For this purpose, a cone-shaped body of revolution has been considered. Such geometries are chosen due to their wider acceptance in modern aerodynamics, with their enhanced heat transfer rates and lower aerodynamic drag. In this connection, axisymmetric bodies of revolution having different body contours and involving surface transverse curvature are usually considered. The selection of such a curved body and the imposed particular type of momentum and thermal boundary conditions make the problem of non-similar nature. Such kinds of problems are normally dealt with by an implicit finite difference scheme due to the accuracy of the solution. The current problem has also been solved with the same numerical scheme. It is concluded that a more streamlined body of revolution has a less spread of velocity and temperature within the boundary layer with a large heat transfer rate and wall skin-friction. On the other hand, the parabolic body of revolution has a large distribution of velocity and temperature but less heat transfer rate and wall skin-friction. Moreover, the assisting role of surface transverse curvature on temperature distribution and wall skin-friction has also been observed in this study.

Investigation of factors enhancing droplets spreading on leaves with burrs.

Spread effect is one of the aspects on deposition quality evaluation of pesticide droplets. It could be affected by many factors such as the microstructure of the target plant leaf surface, physical features of the droplets, and the concentration of spray additives. In this study, using a high-speed photography system, 2.3% glyphosate ammonium salt solution with different concentration of the additive was applied to investigate the impact process of single droplet deposition on the plant leaf surface with burrs. Effect of droplet sizes and velocities on spreading area and dynamic deposition procedure was analyzed using image processing programs. The diffusion factor in the process of droplet spreading was changed over time. The occurrence of bubbles in the droplets was observed in the results. With the bubble generation, the droplet diameter expands and a better diffusion effect is obtained. As a result, better spreading effect was obtained as the droplet diameter was expanded with the generation of bubbles. The significant effects of each physical property of droplets on droplet spreading and the interaction effects between the influencing factors were analyzed. A significant correlation was found between additive concentration, droplet impact velocity, droplet diameters and droplet spreading area. All interactions of concentration:velocity, concentration:diameter, velocity:diameter, and concentration:velocity:diameter had a significant effect on the spreading area of droplets. The study of the factors influencing the process of pesticide droplet impact on the leaf surface contributes to the efficient use of pesticides. Thus, the consumption of pesticides and the resulting impact on the environment can be reduced.

Dynamic Behavior of Droplet Impact on Laminar Superheated Particles.

The impact of droplets on particles involves a wide range of complex phenomena and mechanisms, including bubble nucleation, crater formation, fluidization, and more intricate changes in the boiling regime when impacting superheated particles. In this study, we focus on droplet impact behavior on superheated laminar particles at various temperatures and define six typical characteristic patterns of a single droplet impact on superheated laminar particles, including film evaporation, bubbly boiling, immersion boiling, sputter boiling, transition boiling, and film boiling. It is worth noting that the variations of inertial force FI caused by gravity, the capillary force FC generated by the pores of the droplets, and the dewetting force by the vapor phase FV are the main contributors to different evaporation regimes. Interestingly, we find that the Leidenfrost point (LFP) of droplets on the laminar superheated particles decreases with particle size, which is related to the effect of the pore space generated between the laminar particles. Finally, the effect of temperature, particle size, and Weber number (We) on the dynamic behavior of droplet impact is revealed. Experimental results show that the instantaneous diameter of droplets is inversely proportional to the change of height, with different patterns of maximum spreading diameter and maximum bounce height at different particle sizes, while the maximum spreading velocity and maximum bounce velocity are independent of particle size. We believe the present work would provide a broader knowledge and comprehension of the droplet impact on heated particles and promote the development of the safety and productivity of industrial processes such as fluid catalytic cracking, spray drying, and spray cooling.