Drop Spreading Research Articles

Water drops on nanofiber-coated substrates: Influence of wall temperature and coating thickness on hydrodynamics and wall heat flux distribution

Heat and mass transport during drop impact or a gentle deposition onto a heated substrate depends on the surface chemistry, morphology, thermal and mechanical properties of the substrate, as well as the substrate temperature. In particular, if a substrate is coated with a porous layer of a wettable material, the drop spreading is accompanied by the imbibition of a liquid into the layer. The wetted area is significantly enhanced in comparison with the area which can be covered by a drop spreading over a bare substrate. As a result, the liquid evaporation rate increases and the evaporation time decreases. Understanding the interaction between the liquid spreading, imbibition and evaporation is important, both for enhancement of heat transfer in cooling applications and for functionalizing of porous media. In our experimental studies, a disk of infrared-transparent calcium fluoride is used as the base substrate. The disk is coated with a submicrometer layer of black chromium nitride and an electrically conductive chromium layer, used for heating of the substrate by electrical current. Nanofiber coating layers are applied on top of the chromium layer using electrospinning. The dynamics of drop spreading is captured by a high-speed camera in a side view, the imbibition is observed with a top view camera, and the temperature distribution at the substrate-coating interface is captured by an infrared camera. Based on the transient temperature field, corresponding heat flux distributions are determined. For the detailed analysis of the interplay between hydrodynamics and heat transfer, the nanofiber coating thickness and substrate temperature have been varied. It has been found that the drop drying time and maximal imbibed area depend non-monotonously on the coating thickness. Changing the initial wall temperature leads to qualitatively different distribution of the heat flux at the substrate surface.

Comparison of pneumatic sowing machines by the number of seeds in the slots of the discs and the distance between the slots

This article compares the pneumatic seeders currently in use. The comparison results provide the following indicators specifying the number of seedlings in the clusters, the distance between the clusters, the width of the clusters and the length of the clusters. Based on the results obtained from 3 sowing machines selected for clustering sowing of seeds, it was determined that it is advisable to improve the sowing disc in order to improve it so that the indicators of the sowing machine in 3 variants exceed the indicators of other devices.

The Main Directions of Improvement of Sowing Disks of Units for Joint Sowing of Two Crops

This article describes the design of an experimental sowing disk for joint sowing of corn and sorghum seeds. The results of laboratory studies are presented and the need to improve the sowing disk and its individual elements is justified. A patent search for sowing machines and sowing disks was carried out in order to analyze and further synthesize the best solutions for the development of new designs of a sowing machine and a sowing disk for joint crops. The necessity of conducting research on further improvement of the disk elements in order to increase its reliability is substantiated.

Exploration and characterization of a newly isolated bacterium, Enterobacter quasihormaechei strain BDIFST24001, capable of producing rhamnolipid biosurfactant for oil remediation.

Biosurfactants are naturally occurring compounds synthesized by micro-organisms that increasingly attract attention due to both their living area and application in various industries. In this study, we explore and characterize a novel bacterium, Enterobacter quasihormaechei strain BDIFST24001, isolated for its ability to produce rhamnolipid biosurfactants, with the aim of facilitating oil remediation processes. The isolation of this bacterium was carried out using Luria-Bertani (LB) broth media from environmental samples collected from oil-contaminated sites in Dhaka City. Screening tests, including the oil spreading method and drop collapse assay, were conducted to identify potential biosurfactant-producing strains, leading to the selection of E. quasihormaechei strain BDIFST24001 based on its favourable performance. Subsequent molecular identification revealed a high similarity of the strain's 16S rRNA gene to E. quasihormaechei, which was corroborated through phylogenetic analysis. Further analysis of the biosurfactant produced by this strain indicated its rhamnolipid nature, as confirmed by FT-IR spectroscopy. The rhamnolipids exhibited promising surface-active properties, including a significant reduction in surface tension and emulsification activity, as evidenced by surface tension measurements and emulsification index assays. Optimization studies revealed that the optimal conditions for rhamnolipid production by E. quasihormaechei strain BDIFST24001 were a temperature of 37 °C, pH 10.0 and salinity of 4 %. The rhamnolipids produced by this strain demonstrated effective oil remediation capabilities, as observed through controlled experiments using petrol oil. The rhamnolipids effectively reduced the surface tension of the oil-water interface, facilitating the dispersion and emulsification of the oil phase in water. Overall, our findings highlight the potential of E. quasihormaechei strain BDIFST24001 as a promising candidate for biosurfactant-mediated oil spill cleanup and environmental remediation efforts.

Dynamics of spreading of an asymmetrically placed droplet near a fluid-fluid interface.

Two-dimensional numerical simulations are carried out to study the spreading dynamics of a droplet placed in the vicinity of a fluid-fluid interface. Simulations are performed using the hybrid lattice-Boltzmann technique and the diffuse-interface model by considering three immiscible fluids of the same density and viscosity. In contrast to the well-studied spreading of drops placed symmetrically across fluid-fluid interfaces, this work considers the simultaneous migration, spreading and eventual adsorption of an asymmetrically placed drop. These processes, which are solely driven by interfacial forces, are characterised by monitoring the temporal evolution of geometric parameters, such as the centre of mass, radius and height of the drop, the surface energy of the three interfaces and the associated flow fields inside and outside the droplet. The rate of spreading and rate of adsorption are also calculated to determine the dominant processes that drive the dynamics of the system.

NUMERICAL SIMULATION OF DROP SPREADING OVER A PILLARED SURFACE

Understanding drop-level interactions with micron-size pillars over flat textured surfaces is required in applications such as condensation of water vapor from a humid environment. Accordingly, the spreading of water drops with diameters of ~ 45 μm over micro-pillars has been studied. The studied cylindrical pillars had a diameter of 3.2 μm, whereas the height and pitch were varied from 15 to 20 μm and 6 to 9 μm, respectively. The impact velocity was varied from 0.02 to 1.89 m/s. The stability of the equilibrium and the transitions in the Cassie-Wenzel wetting states were examined. Three-dimensional simulations showed that drops rebound in closely spaced pillars. In contrast, for a relatively large pitch, drops may rebound and partially or entirely wet the pillars. These details depended on the impact velocity and pillar height. The structure and mechanism of moving contact lines over a pillared surface during impact was also examined. In the simulations, the spreading details were correctly reproduced when a time-dependent contact angle model was adopted, which took into account the nonlinear contribution of friction as well as hysteresis owing to finite pinning. The presence of pinning sites at the edges of the pillars was found to be a major factor affecting the possibility of rebounding and the resulting spreading rate. The simulations of drop shapes using this approach matched the experimental results reported in the literature.

Phase separation dynamics in wetting ridges of polymer surfaces swollen with oils of different viscosities.

When drops are placed on a sufficiently soft surface, the drop surface tension drives an out of plane deformation around the contact line (i.e., a wetting ridge). For soft elastomeric surfaces that are swollen with a liquid, capillarity from a drop can induce a phase separation in the wetting ridge. Using confocal microscopy, we study the dynamics of phase separation at the wetting ridge of glycerol drops on silicone elastomers, which are swollen with silicone oils of varying viscosity (i.e., molecular weight). We show that the viscosity of the swelling oil plays a large role in the oil separation size and separation rate. For networks swollen to near their maximum swelling (i.e., saturated), lower viscosity oil separates more and separates faster at early times compared to larger viscosity oil. During late-stage wetting, the growth rate of the separation is a function of viscosity and swelling ratio, which can be described by a simple diffusive model and a defined wetting ridge geometry. In this late-stage wetting, the higher viscosity oil evidently grows faster, likely because it is further from reaching equilibrium. Interestingly, the separated oil phase region grows with a nearly constant, geometrically similar shape. Understanding how phase separation occurs on swollen substrates should provide information on how to control drop spreading, sliding, adhesion, or friction on such surfaces.

Designing a Precision Seed Sowing Machine for Enhanced Crop Productivity

A seed sowing machine is a valuable agricultural device that facilitates the precise and efficient sowing of seeds in fields. When designing and optimizing such a machine, several crucial factors need consideration including seed size, seed rate, soil type, and field conditions. The primary objective is to achieve uniform seed distribution and optimal seed-to-soil contact, which can be accomplished by incorporating a seed metering mechanism to control the seed rate accurately. Versatility is another important aspect of the machine's design, as it should be able to handle different seed sizes, types, soil conditions, and field variations. To achieve this, utilizing advanced technologies such as sensors, automation, and precision farming techniques can significantly enhance the machine's performance and efficiency while also reducing costs and minimizing environmental impact. The optimization of a seed sowing machine plays a crucial role in ensuring successful crop production. By implementing cutting-edge technologies and precision farming techniques, farmers can increase their yields and decrease the amount of seed and fertilizer needed for a specific area. Ultimately, this leads to improved productivity, increased profitability, and a more sustainable approach to agriculture.

Battery powered self-propelled sowing machines: A review

Battery powered self-propelled sowing machines: A review

Investigation of the influence of technological factors on the throughput capacity of the dispenser of a pneumatic sowing machine

One of the significant directions of scientific research in terms of improving the design of sowing machines and increasing their adaptability to modern requirements of automation is the creation of dispensers that provide adjustment of the seeding rate during the operation of the sowing machine. Specialists of the Siberian Research Institute of Mechanization and Electrification of Agriculture have developed a sample of a pneumatic sowing machine dispenser, which was used as a prototype in the study. The dispenser used allows for a smooth adjustment of the seed rate in accordance with the map task, as well as automatic shut-off of the seed supply to the seed line when the machine turns at the headland to prevent overconsumption of seeds and reseeding. The purpose of the research is to determine the design and technological parameters of the experimental dispenser of the pneumatic sowing machine. To achieve the set goal the following tasks were formulated: 1) to conduct a laboratory study of the process of seed metering in the experimental dispenser of the pneumatic seeding machine; 2) to determine the regularities of mutual influence of significant factors on the throughput capacity of the dispenser and describe them by regression equations. In accordance with the listed tasks the process of seed dosing on the laboratory unit was studied. In the course of experimental data processing, regression dependencies were obtained. According to the characteristics of the obtained equations, it is found that the most significant influence on the throughput capacity of the dispenser is the volume of the dispenser coil. Maximum performance of the dispenser is noted at rotor speeds in the range of 80–100 rpm. The highest feed rate and avoidance of spontaneous seed leakage from the dispenser into the seed pipe are achieved at a gate height of the dispenser discharge window within 2 cm. The results of the research can be used to finalize the design of the dispenser in order to use it as an actuator of the system of complex automation of the sowing unit.

Initial contact and spreading of a non-Newtonian drop on a solid surface

In this work, the very initial contact and spreading of drops of two non-Newtonian fluids on a hydrophilic stainless-steel surface were comparatively investigated. The fluids employed were respectively a polymer solution of polyacrylamide (PAAm) and an aqua dispersion of fine graphene oxide (GO) particles. Experimental studies involved visualizing and characterizing the spreading width over time on the substrate surface. A more precise investigation into the initial contact and spreading of non-Newtonian pendant drops on a solid surface was performed through a home-made ultra-high-speed direct current (DC) electrical device with an acquisition frequency up to 1.25 MHz (time interval of 0.8 μs), a high-speed camera and a home-developed high-speed micro-particle image velocimetry (micro-PIV). The competing mechanisms of related forces: inertial, viscous, and capillary forces were probed to lead to different scaling laws.

Insights into carbon dioxide sequestration into coal seams through coupled gas flow-adsorption-deformation modelling

Injecting carbon dioxide (CO2) into coal seams may unlock substantial carbon sequestration potential. Since the coal acts like a carbon filter, it can preferentially absorb significant amounts of CO2. To explore this further, desorption of the adsorbed gas due to pressure drop is investigated in this paper, to achieve an improved understanding of the long-term fate of injected CO2 during post-injection period. This paper presents a dual porosity model coupling gas flow, adsorption and geomechanics for studying coupled processes and effectiveness of CO2 sequestration in coals. A new adsorption−desorption model derived based on thermodynamics is incorporated, particularly, the desorption hysteresis is considered. The reliability of the proposed adsorption-desorption isotherm is examined via validation tests. It is indicated that occurrence of desorption hysteresis is attributed to the adsorption-induced pore deformation. After injection ceases, the injected gas continues to propagate further from the injection well, while the pressure in the vicinity of the injection well experiences a significant drop. Although the adsorbed gas near the well also decreases, this decrease is less compared to that in pressure because of desorption hysteresis. The unceasing spread of CO2 and drops of pressure and adsorbed gas depend on the degree of desorption hysteresis and heterogeneity of coals, which should be considered when designing CO2 sequestration into coal seams.

Spiking ink drop spread clustering algorithm and its memristor crossbar conceptual hardware design

<span lang="EN-US">In this study, a novel neuro-fuzzy clustering algorithm is proposed based on spiking neural network and ink drop spread (IDS) concepts. The proposed structure is a one-layer artificial neural network with leaky integrate and fire (LIF) neurons. The structure implements the IDS algorithm as a fuzzy concept. Each training data will result in firing the corresponding input neuron and its neighboring neurons. A synchronous time coding algorithm is used to manage input and output neurons firing time. For an input data, one or several output neurons of the network will fire; confidence degree of the network to outputs is defined as the relative delay of the firing times with respect to the synchronous pulse. A memristor crossbar-based hardware is utilized for hardware implementation of the proposed algorithm. The simulation result corroborates that the proposed algorithm can be used as a neuro-fuzzy clustering and vector quantization algorithm.</span>

A simple and low-cost paper-based device for simultaneous determination of hematocrit and hemoglobin levels in point-of-care settings

Hematocrit and hemoglobin levels are common blood tests used to assess the overall health status of patients as well as the oxygen-carrying capacity of the blood. The gold-standard technologies to determine the hematocrit and hemoglobin levels are precise and fast, but they are not pragmatic in extreme point-of-care settings due to the prohibitive cost, process complexity, and sophisticated facilities. Therefore, here, we report the development of a microfluidic paper-based analytical device to determine hematocrit and hemoglobin levels simultaneously. This device exploits the area of the stain formed by a spreading drop of 20 μl of whole blood on Whatman filter paper immobilized with sodium chloride and ethylenediaminetetraacetic acid for hematocrit level, whereas for hemoglobin concentration, it utilizes the gray color intensity of a 20 μl droplet of a mixture of blood and de-ionized water. The performance of the device is verified by comparing with gold-standard results of the automated hematology analyzer, showing a high degree of correlation (R2) of 0.9651 and 0.9701 for hematocrit and hemoglobin levels, respectively. The bias and standard deviation of the differences between the two measurements for hematocrit determination are 0.002 and 1.005, respectively, while the bias and standard deviation of differences between the two methods for hemoglobin determination are 0.065 and 0.398, respectively. This device is likely to provide a simple, fast, disposable, and inexpensive tool to determine the hematocrit and hemoglobin levels in resource-constraint settings.

A Unified Transformation Framework for Studying Various Situations of Vertical/Oblique Drop Impact on Horizontal/Inclined Stationary/Moving Flat Surfaces

There are various situations of drop impact on solid surfaces widely occurred in natural phenomenon or used in different industrial applications. However, comparing and classifying these drop impact situations is not easy due to different states of the parameters affecting drop impact dynamics. In this article, a unified transformation framework is proposed to study various situations of vertical/oblique drop impact on horizontal/inclined stationary/moving flat surfaces with/without a crossflow. This simple framework consists of a coordinate with normal and tangential axes on a horizontal stationary surface. For each drop impact situation, the drop velocity, gravitational acceleration, possible induced flow due to the moving surface, and possible crossflow are transformed into the framework. Comparing the transformed versions of considered drop impact situations facilitates identification of their physical similarities/differences and determines which situations (and under what conditions) lead to identical results and can be used interchangeably. Although common situations of drop impact on moving surfaces (having tangential component of surface velocity) lead to asymmetric drop spreading, the possibility of symmetric drop spreading on moving surfaces is demonstrated and analyzed using the proposed transformation framework. This interesting possibility means that for related production lines or experimental setups, where symmetrical drop spreading is required, the surface does not need to be stationary. In such applications/setups, the use of moving surfaces (rather than stationary surfaces) can considerably accelerate the symmetric drop impact process. Our simulation results of several of the considered drop impact situations well confirm the facilities/predictions of the proposed transformation framework.

On-Farm Evaluation of Tractor Drawn Wheat Seed Drill

This experiment was conducted to evaluate the performance of a tractor-drawn wheat seed drill machine which can sow wheat and fertilizer at predetermined depths and row spacing. The machine performances were evaluated in terms of Seed and fertilizer rate, depth of seed placement, row spacing, plant population, field capacity, and field efficiency. Randomized complete block design with three forward speeds, three hopper loading, and three replications were used as experimental design. There were no visible or internal seeds damaged by the machine and it shows that there was no reduction in germination percentage when compared with the seed supplier recommendation. The seed and fertilizer rate was calibrated and recorded as 125 kg/ha and 150 kg/ha respectively for 20 cm row spacing. The seed drill was evaluated at speeds of 3, 4, 5 km/hr and hopper loading levels of H50, H75, and H100. Both the operating speed and hopper loading capacity of the machine had a significant effect on seed and fertilizer rate at p < 0.05. The average field capacity, field efficiency, and fuel consumption at 4km/hr speed of operation were 0.43 ha/hr, 85.93%, and 3.8 l/hr respectively. 378 to 380 plant populations per 1.2 m2 area were counted during seedling count. Depending on the results of the performance evaluation, it is concluded that the developed seed drill machine can be efficiently and economically used by the majority of farmers.

Relative Comparison in Performance Evaluation of Happy Seeder and Conventional Seed Drill under Rice-Wheat Cropping System

The study evaluates the Happy Seeder's performance in sowing wheat crops in combined harvested paddy fields in the Moradabad region, aiming to mitigate crop residue burning and promote sustainable agriculture. The rice-wheat cropping system in the Indo-Gangetic region generates significant crop residues after combine harvesting, leading to environmental and health hazards. The Happy Seeder, designed to cut and lift rice straw while sowing wheat, offers a promising solution to manage residues and prevent burning. Various parameters, including forward speed, crop residue condition, and soil bulk density, were investigated as independent variables to assess the Happy Seeder's performance. Results show an actual field capacity of 0.23 to 0.29 ha/, with fuel consumption ranging from 4.12 to 4.40 l/h at different speeds. Field efficiency varied from 43.4% to 65%, with the best performance at 3.5 km/h forward speed. Economically, the Happy Seeder proves to be a cost-effective alternative, saving 613.83 ₹/compared to conventional seed drills. Farmers responded positively to its labor-saving features, timely sowing, and eco-friendly benefits, leading to improved crop growth and higher yields. In conclusion, the Happy Seeder demonstrated efficiency, economic viability, and positive farmer feedback, making it a valuable tool for sustainable agriculture in the Moradabad region and beyond. Its adoption can contribute to residue management, improved soil health, and increased crop productivity, fostering an environmentally conscious rice-wheat cropping system in the Indo-Gangetic region.

Understanding under-liquid drop spreading using dynamic contact angle modeling

We present numerical modeling and experimental data to investigate droplet spreading dynamics on a substrate submerged in another liquid. Dynamic contact angle equations are formulated and used to simulate the spreading of different oil drops in the presence of water. Drop spreading in the presence of water starts with a viscosity-dominated regime where a scaling law of r∼t is observed. For low viscosity drops, an intermediate inertial regime with scaling r∼t12 is observed after the viscous regime. For high viscosity drops, such an intermediate regime diminishes. At later stages near equilibrium, the spreading dynamics follow Tanner's law for all drops.

Small-sized unit for the restoration of herbage in mountain meadows and pastures

BACKGROUND: The results of RD for the laboratory prototype of the unit for grass seeds oversowing on mountain slopes, which can increase labor efficiency and mountain forage lands yield by 20-25%, are presented.
 AIMS: The developed laboratory prototype of a block module based on the Feng Shou 180 mini-tractor for surface oversowing of grass seeds, providing with an accelerated increase in the yield of perennial grasses and soil resistance to water and wind erosion.
 METHODS: Technical expertise and testing of the unit and technology were carried out in the mountainous zone of the Republic of North Ossetia Alania (Dargava basin, the base station of the Institute) at an altitude of 1540 meters above sea level. The indicators of the test conditions and functional performance of the unit were determined according to the OST 10.5.1-2000 industry standard. Technical examination of the unit was carried out according to the OST 10.2.1-97. Surface sowing of grass seeds was carried out according to GOST 31345-2017. The subject of research included the technology of grass seeds oversowing, the design of the unit and working bodies: pendular sowing machines, seeding rates and method of sowing.
 METHODS: The laboratory prototype of the small-sized unit based on the Feng Shou 180 mini-tractor for surface oversowing of grass seeds has been developed and manufactured. The block module is a hinged structure with a two-row arrangement of containers for grass seeds and with pendular sowing machines. In the design of the small-sized mountain unit, motion across the slope from top to bottom is performed with a shuttle method with rolling of the sown seeds by press wheels. The grass was oversown on a rarefied section of the northern slope with a slope angle of 1316 on the Sugsadtanrag terrain.
 CONCLUSIONS: The practical application of the small-sized unit based on the Feng Shou 180 mini-tractor for surface oversowing of grass seeds with their subsequent pressing in areas in highland and piedmont areas ensures detaining of degradation processes of slope areas, accelerated increase in yield, quality and quantity of perennial grasses, improves soil resistance to water and wind erosion.

Evaluation of different paddy straw management technologies for their economic viability in rice-wheat system

The study examines the economics of different paddy straw management methods in rice-wheat systems in Gurdaspur, Punjab during the Rabi seasons (2019-20 and 2020-21). The experiment was carried out with 2 wheat varieties, HD 3086 (V1) and PBW 550 (V2), using varied treatment combinations of crop residue management approaches, tillage and seed drilling methods. Based on the pooled data, the PAU (Punjab Agricultural University) cutter cum spreader + incorporation with Mould Board plough + Use of Seed drill (M4) treatment produced the highest plant height (95.87 cm). Treatment PAU cutter cum spreader + PAU happy seeder with press wheel (M2) (437.71) had the highest density of tillers per square meter, significantly outperforming other treatments. A significant interaction was observed between paddy residue management methods and varieties in terms of the number of tillers. Maximum spike length (12.81 cm) was obtained with Stubble Shaver + Burning + Zero Tillage Drill (M1), whereas maximum number of spikelets per spike (18.33) was noted in method (M2). The treatment method (M2) turned out to be the most efficient in terms of yield (44.02 q/ha) and benefit cost ratio (1.72).