Maximum Spreading Distance Research Articles

Effect of sneeze flow velocity profiles on the respiratory droplets dispersion in a confined space: An experimental and computational fluid dynamics study

In this study, the effects of sneeze velocity profiles, including peak velocity (PV), peak velocity time (PVT), and sneeze duration time (SDT), on the dispersion of respiratory droplets were studied experimentally and numerically. Spatial–temporal datasets of droplet velocity exhaled from several subjects' mouths with different physiological characteristics were obtained by particle image velocimetry. A direct relationship was found between the forced vital capacity and PV, while the subject's body mass index significantly affected the SDT. A transient computational fluid dynamics (CFD) approach using the renormalization group k–ε turbulence model in conjunction with the Lagrangian particle tracking was developed and used to simulate sneeze droplet motion characteristics. Both one-way and two-way (humidity) coupling models were used in these simulations. The CFD results showed that the two-way (humidity) coupling model provided better agreement with the data in the turbulent and expanded puff zones than the one-way coupling model. The one-way model led to reasonably accurate results in the fully dispersed and dilute-dispersed droplet phases. The effect of injection duration time and injection angle on PVT was larger than that on PV values, while the effect of initial injection velocity on PV was higher than that on PVT values. In addition, the initial injection velocity and angle significantly affected the maximum spreading distance of droplets dmax,sp. The numerical results obtained from the dilute-dispersed droplet phase were in good agreement with the trajectories of isolated droplets in the experimental data. The findings of this study provide novel insights into the effect of sneeze velocity profiles on dmax,sp, and the sneezer subject physiological effect on the threshold distance for the transmission of respiratory pathogens in a confined space.

Development of Automatic Fish Feeding Machine for Integrated Floating Cage Aquageoponic System

Aims: The objective of this work was to develop and evaluate the performance of an automatic fish feeder- to enhance aquacultural practices and farmponds
 Place and Duration of Study: The research study was conducted at Madakasira, (Latitude: 13°56ʹ55.96″ N and Longitude: 77°18ʹ45.38″ E) which is located in Anantapur district of Andhra Pradesh, India. The mean annual temperature and annual rainfall of the study area are 27.6°C and 532 mm, respectively. Most of the rainfall (~80%) is received during South-West monsoon. The experiment study was conducted from March‒June, 2018.
 Methodology: Automatic fish feeder includes both electrical and mechanical mechanism. The materials includes for the development of the feeder was cone shape hopper, top covering lid, base, 12V DC motor, 12V 7Ah Rechargeable Lead Acid Battery, Arduino Uno, Bluetooth HC-05 module, 5v Relay, DC-DC step-down converter. The developed feeder was operated with the help of mobile app by using Bluetooth HC-05 module. The spreading distance and amount of feed spread, opening angles of the feeder were evaluated during the research period.
 Results: Our results showed that the amount of feed spread was maximum (140 g m-1) with 1.0 m height and was minimum (101 g m-1) at 0.2 m height. This results clearly shows that the fish feeder has to be kept at maximum height so that it covers maximum spreading distance with minimum loss of fish feed by drift. With increase in height of the machine from ground surface, the spreading distance of the fish feed from the feeding machine was also increased.
 Conclusion: Farmers were satisfied with this new technology which helps to avoid manual feeding and provides the clean environment.

Influence of indoor environmental conditions on airborne transmission and lifetime of sneeze droplets in a confined space: a way to reduce COVID-19 spread.

Effects of indoor temperature (T∞) and relative humidity (RH∞) on the airborne transmission of sneeze droplets in a confined space were studied over the T∞ range of 15-30°C and RH∞ of 22-62%. In addition, a theoretical evaporation model was used to estimate the droplet lifetime based on experimental data. The results showed that the body mass index (BMI) of the participants played an important role in the sneezing jet velocity, while the impact of the BMI and gender of participants was insignificant on the size distribution of droplets. At a critical relative humidity RH∞,crit of 46%, the sneezing jet velocity and droplet lifetime were roughly independent of T∞. At RH∞ < RH∞,crit, the sneezing jet velocity decreased by increasing T∞ from 15 to 30°C, while its trend was reversed at RH∞ > RH∞,crit. The maximum spreading distance of aerosols increased by decreasing the RH∞ and increasing T∞, while the droplet lifetime increased by decreasing T∞ at RH∞ > RH∞,crit. The mean diameter of aerosolized droplets was less affected by T∞ than the large droplets at RH∞ < RH∞,crit, while the mean diameter and number fraction of aerosols were more influenced by RH∞ than the T∞ in the range of 46% ≤ RH∞ ≤ 62%. In summary, this study suggests suitable indoor environmental conditions by considering the transmission rate and lifetime of respiratory droplets to reduce the spread of COVID-19.

Numerical simulation of two droplets impacting on the wall continuously

The application of spray system has been widely used in the industry. The impact of droplets between the wall impact has become one of the important studies of spray system. The investigation is to develop a numerical code for the simulation of two water droplets impinging continuously upon the wall. In the code, the structured single-block and staggered grid system are adopted for discretization of the space domain, while the finite volume method is applied to solve iteratively the governing equations of mass and momentum. The interconnection between the velocities and pressure is dealt by SIMPLER methods. In order to capture the boundary of the deformation of droplets, a level set function method is considered due to the advantage of handling the incorporation and breakup of the boundary easily. In the paper, the numerical verification of a water droplet impinged upon the wall are very accurate with the experimental values. Subsequently, a forward droplet with different Reynolds number of 100, 200, 400 and a backward droplet with the fixed Reynolds number of 200 vertically impact the wall continuously. According to the calculation results a forward droplet with smaller the Reynolds number shows the larger the maximum spread distance after merging. In impact process of different angles, the merged droplet moves along the wall, and produces also oscillates back and forth asymmetrically. As for the maximum horizontal spread distance of the merged droplet, the impact angle of 30 degrees is the smallest, and the impact angle of 60 degrees is the largest.

Reduced order models for uncertainty quantification of gas plumes from leakages during LNG bunkering

The impacts of uncertainty in wind conditions on the spread of hazardous plume resulting from a jet leak during a Liquefied Natural Gas (LNG) bunkering operation were investigated. Computational Fluid Dynamics (CFD) using the Reynolds-Averaged Navier Stokes (RANS) solver with multi-species transport and a transient leak model for keyhole leak was used for the simulation of a simplified bunkering station. Following detailed validation & verification, the sensitivity of the safety zone extents to the wind conditions was demonstrated. CFD results reinforced the strong dependence of the maximum spread distance on wind conditions and enclosure geometry. To quantify the impact of input uncertainty from wind conditions on the plume spread, a reduced-order model (ROM) was developed using the proper orthogonal decomposition (POD) of CFD results on sampled conditions. ROM-POD enables a fast evaluation of the plume under changing wind conditions and acts as an efficient forward model for uncertainty quantification using Polynomial Chaos Expansion (PCE) technique. The spatial distribution of plume residence time under the same input uncertainty was also obtained from the proposed approach showing its potential in risk assessment and design of bunkering facilities.

Air bubble entrapment during drop impact on solid and liquid surfaces

The phase-field modeling (PFM) of water drop impact onto a dielectric hydrophobic parafilm surface is performed to explore air entrapment and its influence on deposition and rebound phenomena. Local and global characteristics of the drop impact are taken into account by using the combined Cahn-Hilliard and Navier-Stokes equations. The modeling results of water drop impact are directly compared with our experimental measurements in terms of maximum spreading distance, and air bubble size. The simulation results reveal that air can be trapped under the liquid drop during the initial impact as well as during the retraction phase at the center of the drop due to the closure of the liquid layer above a cavity. It is found that the drop diameter and the impact velocity play significant roles in the air entrapment phenomena. The probability of air bubble formation is higher at lower impact velocity and for larger drop size. The model is also capable of simulating the case of drop impact onto a water surface, and the results are validated using prior literature data. In addition, the influence of the phase-field variables and the mesh adaptation scheme on the PFM is studied and discussed. Thus, our findings provide new qualitative and quantitative insights into the influence of air entrapment on drop deposition onto hydrophobic and liquid surfaces.

Measurement and analysis on large-scale offline mobile app dissemination over device-to-device sharing in mobile social networks

Recently, the issue of offloading cellular data while reducing the duplicated cellular transmission has gained more and more attention. Several studies have shown that sharing contents through Device-to-Device (D2D) to offload traffic to local connections nearby can offer better performance for mobile users. Nevertheless, most existing proposals are somewhat confined to small-scale data sets or limited feature dimensions, relied on unconsolidated hypotheses and measurements of data sets. This paper presents a prior work of large-scale measurements on 3.56 TBytes of real-world data sets, which contain D2D content sharing activities from a popular D2D sharing application (APP). We conduct a comprehensive analysis of multi-dimensional features, including time series, structural properties, meeting dynamics, location relationship, and propagation tree. Our analysis reveals that (i) D2D sharing makes the hops between users shorter (in 3 or 4 degrees), (ii) the maximum spreading distance of content dissemination is 27 hops, (iii) we provide a new evidence of log-normal distribution of all user encounters (named meeting dynamics in this paper) based the fit of inter-TX time, Inter-Content Time (ICT) and Contact Time, (iv) online factor (O) and social factor (S) demonstrate the largest positive correlation and indicate that the two factors have high linear correlation. Finally, we analyze the correlations among all the impact factors by Pearson coefficient, principal component analysis, and latent semantic analysis, respectively. Results reveal that online factor (O) and social factor (S) have a high correlation, especially both of them have a great effect on D2D sharing activities.

Drop impacting on a single layer of particles: Evolution of ring without particles

In this study, we examined the impacts of a millimeter sized water drop hitting a layer of uniformly distributed particles on a hydrophilic/hydrophobic glass slide. A ring/disc structure without particles was formed and modified by two mechanisms: pushout and pullback. The pushout factor dominated the process when the drop hit on the hydrophilic glass slide, while the pullback factor played a decisive role during impact on the hydrophobic surface. The rebound of a drop on the hydrophobic surface formed a disc-shaped ring. We showed that the ratio of the effects of these two factors on the ring/disc width were independent from the impact speed, in both experimental and scaling analyses. Our results also suggested that higher hydrophobicity of a water drop on the hydrophobic glass slide, instead of a polymethyl methacrylate (PMMA) particle surface, resulted in a lower maximum spreading distance when the drop hit the PMMA particle layer on a hydrophobic surface.

Human Cough as a Two-Stage Jet and Its Role in Particle Transport.

The human cough is a significant vector in the transmission of respiratory diseases in indoor environments. The cough flow is characterized as a two-stage jet; specifically, the starting jet (when the cough starts and flow is released) and interrupted jet (after the source supply is terminated). During the starting-jet stage, the flow rate is a function of time; three temporal profiles of the exit velocity (pulsation, sinusoidal and real-cough) were investigated in this study, and our results showed that the cough flow’s maximum penetration distance was in the range of a 50.6–85.5 opening diameter (D) under our experimental conditions. The real-cough and sinusoidal cases exhibited greater penetration ability than the pulsation cases under the same characteristic Reynolds number (Rec) and normalized cough expired volume (Q/AD, with Q as the cough expired volume and A as the opening area). However, the effects of Rec and Q/AD on the maximum penetration distances proved to be more significant; larger values of Rec and Q/AD reflected cough flows with greater penetration distances. A protocol was developed to scale the particle experiments between the prototype in air, and the model in water. The water tank experiments revealed that although medium and large particles deposit readily, their maximum spread distance is similar to that of small particles. Moreover, the leading vortex plays an important role in enhancing particle transport.

Surfactant Driven Post-Deposition Spreading of Aerosols on Complex Aqueous Subphases. 1: High Deposition Flux Representative of Aerosol Delivery to Large Airways.

Aerosol drug delivery is a viable option for treating diseased airways, but airway obstructions associated with diseases such as cystic fibrosis cause non-uniform drug distribution and limit efficacy. Marangoni stresses produced by surfactant addition to aerosol formulations may enhance delivery uniformity by post-deposition spreading of medications over the airway surface, improving access to poorly ventilated regions. We examine the roles of different variables affecting the maximum post-deposition spreading of a dye (drug mimic). Entangled aqueous solutions of either poly(acrylamide) (PA) or porcine gastric mucin (PGM) serve as airway surface liquid (ASL) mimicking subphases for in vitro models of aerosol deposition. Measured aerosol deposition fluxes indicate that the experimental delivery conditions are representative of aerosol delivery to the conducting airways. Post-deposition spreading beyond the locale of direct aerosol deposition is tracked by fluorescence microscopy. Aqueous aerosols formulated with either nonionic surfactant (tyloxapol) or fluorosurfactant (FS-3100) are compared with surfactant-free control aerosols. Significant enhancement of post-deposition spreading is observed with surfactant solutions relative to surfactant-free control solutions, provided the surfactant solution surface tension is less than that of the subphase. Amongst the variables considered--surfactant concentration, aerosol flow-rate, total deposited volume, time of delivery, and total deposited surfactant mass--surfactant mass is the primary predictor of maximum spread distance. This dependence is also observed for solutions deposited as a single, microliter-scale drop with a volume comparable to the total volume of deposited aerosol. Marangoni stress-assisted spreading after surfactant-laden aerosol deposition at high fluxes on a complex fluid subphase is capable of driving aerosol contents over significantly greater distances compared to surfactant-free controls. Total delivered surfactant mass is the primary determinant of the extent of spreading, suggesting a great potential to extend the reach of aerosolized medication in partially obstructed airways via a purely physical mechanism.

Application of a 3-D laser scanner for characterising centrifugal fertiliser spreaders

The suitability of using 3-D laser technology to assess the performance of a twin disc centrifugal fertiliser spreader was analysed. A static test with an Amazone ZA-M twin disc fertiliser spreader distributing di-ammonium sulphate was developed. The spreader was adjusted to spread the fertiliser at a distance of 12 m at three different rates. The test was conducted inside a building; 64 sample boxes were installed on the floor within a 2 m × 2 m frame. Considering the static test, for each spreading rate, five consecutive measurements were made using a Leica HDS6000 3D laser scanner. The information supplied by the laser scanner was correlated with the weight of the fertiliser collected in the boxes using linear regression equations. Each regression model was obtained for one particular and specific spreading configuration. This reduces the applicability of the method because for each spreader setting requires a new surface distribution to be measured to establish a new regression model. A field test was conducted to obtain a fertiliser distribution curve, with the machine set at 41.1 kg min −1 , while the tractor was progressing at 8 km h −1 . This information was used to validate the laser technology by comparing the real distribution curve with the simulated curve. The correlation coefficient (adjusted R 2 ) was 0.86. The information provided by the scanner also enabled the surface distribution of the product, the maximum spreading distance, the spreading symmetry on both sides of the machine and the trajectory of the grains of fertiliser to be analysed.

Genotypic diversity enhances invasive ability of Spartina alterniflora

Although genetic diversity is very important for alien species, which have to cope with new environments, little is known about the role that genetic diversity plays in their invasive success. In this study, we set up a manipulation experiment including three levels of genotypic diversity to test whether genotypic diversity can enhance the invasive ability of alien species, in our case the invasive Spartina alterniflora in China, and to infer the underlying mechanisms. There was no significant relationship between genotypic diversity and parameters of performance in the first year; however, from the summer of the second year onwards, genotypic diversity enhanced four of the six parameters of performance. After two growing seasons, there were significant positive relationships between genotypic diversity and maximum spread distance, patch size, shoot number per patch, and aboveground biomass. Moreover, abundance of the native dominant species Scirpus mariqueter was marginally significantly decreased with genotypic diversity of S.alterniflora, suggesting that enhanced invasive ability of S.alterniflora may have depressed the growth of the native species. There was no significant difference in most measures of performance among six genotypes, but we observed a transgressive over performance in four measures in multiple-genotype patches. At the end of the experiment, there were significant nonadditive effects of genotypic diversity according to Monte Carlo permutations, in six-genotype, but not three-genotype plots. Our results indicated that both additive and nonadditive effects played roles in the positive relationship between genetic diversity and invasion success, and nonadditive effects were stronger as duration increased.

Spreading Dynamics of Surfactant Solutions

The spreading behavior of microdrops of surfactant solutions at solid surfaces has been studied. The influence on the spreading of different factors, such as the drop lifetime prior to surface contact, surface tension dynamics, surface energy, and surfactant properties, was systematically investigated. The results obtained suggest the existence of two spreading regimes exhibiting different spreading characteristics: In the first, nondiffusive regime, the spreading is very rapid and controlled to different extents by inertia, gravity, and capillarity, depending on the drop size, impact energy, and interfacial tension balance. It is shown in this study that the initial drop surface tension, which is set by the surface tension decay rate and the drop lifetime prior to the surface impact, strongly influences the maximum spreading distance in the nondiffusive spreading regime. The second, diffusion-controlled regime, is characterized by slower concentration-dependent spreading rates. The spreading rate is, here, mainly controlled by the diffusive transport of surfactant to the expanding liquid−vapor interface. In this regime, the drop base radius exhibits an approximate rb2 ∝ t dependence on time. The spreading kinetics at hydrophobic surfaces has been discussed in the framework of a simplified theory. Depending on the assumptions regarding the drop shape, rb5/2 ∝ t to rb2 ∝ t spreading laws are obtained. This agrees reasonably with the experimentally observed relationship.

The spreading of radiolabelled fatty suppository bases in the human rectum

The purpose of this study was to develop a radiolabelling method for assessing the spreading of fatty suppository bases (Witepsol H-5, W-35 and S-55), and to apply this technique to the evaluation of suppository disposition in the human rectum. 99mTc was bound chemically to the bases Witepsol H-5 and W-35, and mixed physically with Witepsol S-55. The spreading of each suppository base was monitored by gamma-scintigraphy following rectal administration. The mean radioactivity remaining at the inserted region 4 h after administration was 44.2% of total activity. The mean perpendicular maximum spreading distance from this region was 7.7 cm on the scintigram near to the sigmoid colon. Defecation was suggested to be a factor influencing the spread of suppository bases. However, there was no clear relationship between the type of suppository base used and the extent of its spread within the rectum.

Boiling and spreading of liquid nitrogen and liquid methane on water

An experimental and theoretical investigation was carried out to study the boiling and spreading of liquid nitrogen and liquid methane on water, in a one-dimensional configuration. With the equations of continuity and momentum transfer, a mathematical model was developed to describe the boiling-spreading phenomena of cryogens spilled on water. The model accounts for a decrease in the density of the cryogenic liquid due to bubble formation. Experimental spreading fronts were successfully simulated by assuming constant evaporation rates (40 kW/m 2 and 92 kW/m 2 for nitrogen and methane respectively) in the theoretical model. The model predicts the maximum spreading distance and the time for complete vaporization.