Jet Length Research Articles

Molecular dynamics simulation of the cone-jet electrospray: Role of surfactants

Electrospray in the cone-jet regime could produce highly charged and fine monodisperse drops, and further disintegrates into nanoscale drops, even ions due to synergism of Rayleigh instability and evaporation. The jet and its breakup instability into drops are significantly affected by liquid properties including surface tension, conductivity, density and others. Surfactants may play important roles on gas-liquid interface and are usually added in solution to vary liquid property and may further affect electrospray behaviors. In present work, the ethanol containing surfactants is atomized in the cone-jet to discuss the synergistic effect of surfactant types, concentrations and surfactant-salt on the jet evolution behaviors under direct current electric fields using molecular dynamics (MD) method. It is found that the jet length of ethanol solution with Span-80 is the longest (Span-80, SDS, CTAB and TX-100), while it has excellent dispersion. The addition of CTAB could make ethanol solution transform from continuous jet into dripping. SDS interacts most violently with ethanol due to the presence of sodium ions. As surfactant concentration increasing, the number of solution molecules sprayed remarkably increases, while the interaction generated from ethanol decreases. The number of molecular clusters (composed of three or more ethanol molecules) in the cone-jet electrospray increases with increasing Span-80 concentration. It is also found that the addition of Span-80 slightly changes the average bond angle of ethanol and bond angle distribution. The ethanol atomization morphology transforms to spindle becasue of the synergistic effect of surfactant and salt ions. The interaction generated between ethanol molecules plays a dominating role and decreases due to the generation of spindle-shaped drops. The hydrogen bond generated from ethanol decreases with increasing conductivity and surface tension. The conclusions of this paper will be latent value for the optimization of physical parameters in electrospray.

Application of a hybrid ANFIS with metaheuristic algorithms to estimate the aeration design parameters

Abstract Cavitation is a common and complex hydraulic phenomenon on the chute spillways and may cause damage to the structure. Aeration in the water flow is one of the best ways to prevent cavitation. To design an aerator, estimation of aeration coefficient (β), jet length (L/h0), and jet impact angle on chute (tanγ) are important in this study. The potential of a hybrid adaptive neuro-fuzzy interface system (ANFIS) with metaheuristic algorithms was investigated to estimate the required parameters to design an aerator. The ANFIS was combined with four metaheuristic algorithms, including differential evolution (DE), ant colony optimization (ACO), genetic algorithm (GA), and particle swarm optimization (PSO). Experimental data and dimensionless parameters were used to develop the proposed hybrid ANFIS models. Three statistical indicators, including root mean square error (RMSE), mean average error (MAE), and coefficient of determination (R2), were employed to compare the proposed methods with empirical relations. According to the statistical indicators, among the data-driven methods, the ANFIS–DE method had the best prediction in estimating β (RMSE = 0.018, R2 = 0.984, MAE = 0.013), L/h0 (RMSE = 1.293, R2 = 0.963, MAE = 1.082), and tanγ (RMSE = 0.009, R2 = 0.939, MAE = 0.007).

Numerical investigation of impinging jet ventilation in ICUs: Is thermal stratification a problem?

Intensive care units (ICUs) are the high incidence sites of hospital-acquired infections, where impinging jet ventilation (IJV) shows great potential. Thermal stratification of IJV and its effect on contaminants distribution were systematically investigated in this study. By changing the setting of heat source or the air change rates, the main driving force of supply airflow can be transformed between thermal buoyancy and inertial force, which can be quantitatively described by the dimensionless buoyant jet length scale (). For the investigated air change rates, namely 2 ACH to 12 ACH, varies between 0.20 and 2.80. The thermal buoyancy plays a dominant role in the movement of the horizontally exhaled airflow by the infector under low air change rate, where the temperature gradient is up to 2.45 °C/m. The flow center remains close to the breathing zone of the susceptible ahead, resulting into the highest exposure risk (6.6‰ for 10-µm particles). With higher heat flux of four PC monitors (from 0 W to 125.85 W for each monitor), the temperature gradient in ICU rises from 0.22 °C/m to 1.02 °C/m; however, the average normalized concentration of gaseous contaminants in the occupied zone is reduced from 0.81 to 0.37, because their thermal plumes are also able to carry containments around them to the ceiling-level readily. As the air change rate was increased to 8 ACH (), high momentum weakened the thermal stratification by reducing the temperature gradient to 0.37 °C/m and exhaled flow readily rose above the breathing zone; the intake fraction of susceptible patient located in front of the infector for 10-µm particles reduces to 0.8‰. This study proved the potential application of IJV in ICUs and provides theoretical guidance for its appropriate design.}.

Prediction of gamma-ray emission from Cygnus X-1, SS 433, and GRS 1915+105 after absorption

Context. Stellar black hole X-ray binary stars (BHXRBs) are among the most luminous and powerful systems located in our Milky Way and in other galaxies of the Universe. Their jets are prominent sources of particles (e.g., neutrinos) and radiation emissions in energy ranges detectable by terrestrial and space telescopes, even from galaxies deep in the space. A significant factor, however, would be the photon absorption effect that occur due to scattering on the lower end of the energy radiation of the system’s surroundings. Aims. We aim to study in detail and extract predictions for the emitted gamma-ray intensities and integral fluxes of the jets emanating from BHXRB systems Cygnus X-1, GRS 1915+105, and SS 433. Toward this end, we also investigate the severe effects of gamma-ray absorption that eradicate part of the produced intensity spectra. Furthermore, we explore the jet regions that are most likely to emit unabsorbed gamma-rays capable of reaching detectors on Earth. Our goal is to calculate the integral fluxes before and after absorption for the abovementioned systems and compare the results with the very-high-energy gamma-ray observations of sensitive telescopes such as the MAGIC, H.E.S.S., Fermi-LAT, and so on. Methods. The implemented gamma-ray emission mechanisms initiate from the p − p scattering process inside the hadron-dominated jets following the well-known shock-wave particle acceleration. In addition, we estimate the optical depths of three absorption processes between gamma-ray photons and (i) accretion disk X-ray emission, (ii) black hole corona photons, and (iii) donor star thermal emission. We also examine the dependence of the absorption optical depths on various parameters, such as the disk’s temperature, coronal radius and, donor star luminosity. Results. We find that disk absorption is dominant for distances of z < 1010 cm from the black hole, while the donor star absorption dominates for 1010 < z < 1012 cm. Beyond that jet point, the absorption effects become significantly weaker. Cygnus X-1 presents the highest gamma-ray integral flux across the jet length, while GRS 1915+105 emits the least due to its weakly collimated jets. The jets of SS 433 emit gamma-rays only for z > 1010 cm due to severe disk absorption fueled by the system’s super-Eddington accretion limit.

Simulation and Experimental Study on Jetting Projectile Charge Penetrating Multi-Layer Spaced Targets with Large Spacing

To study the ability of shaped charges to penetrate typical ship targets, two shaped charges with the same diameter of 200 mm but different configurations are designed to generate two forms of jetting projectile charge (JPC). Based on the protective structure of typical ship targets, static penetration tests are performed using the two types of a shaped charge with copper liner and 10-layer spaced targets with a total span of 16 m which is made in 921A steel. Numerical simulations under the same working conditions are also carried out. It is found that the simulation results of the penetration depth and the number of layers of target perforated by the JPC are much greater than the experimental results. In fact, the JPC breaks up when moving to a certain distance, and the JPC segments after breakup have a transverse drift velocity, causing the segment to deviate from the original penetrating channel. The influence of drift velocity after JPC fracture cannot be considered in numerical simulation, resulting in significant differences between numerical simulation and experimental results. Thus, this paper proposed a segment-based numerical simulation method and analyzed the penetration process of JPC fragments after JPC fracture. Combined with experimental results, the radial motion after JPC fracture and the final distribution of penetration holes can be well revealed. It is found that the penetration depth and the number of layers of target perforated by the JPC depend on the tip velocity of each segment and the jet length.

Influences of semi-circular, square, and triangular grooves on mixing behavior of an axisymmetric supersonic jet

The length of the supersonic jet ejected from the military aircraft must be reduced in order to decrease its heat signature and aeroacoustic noise and thereby to enhance its stealth capability. The reduction or manipulation of the supersonic core can be achieved through various passive control techniques. Considering this, the present study explores the mixing characteristics of supersonic jets with and without passive controls. Passive controls in the form of grooves configured at the exit of a Mach 1.73 convergent–divergent nozzle are investigated computationally. Particularly, the supersonic jet decay characteristics and flow development for a plain nozzle and a nozzle with semi-circular, square, and triangular grooves are presented. In addition, the study explores different turbulence models, namely, Spalart–Allmaras, realizable k-ε, std k-ω, shear stress transport (SST) k-ω, and SST transition. The realizable k-ε turbulence model is found to be the most effective one in capturing the supersonic jet structure. It is observed that the grooves produce large distortions in the jet structure, accompanied by significant mass entrainment and lateral spread. Interestingly, semi-circular grooves are proven to be most effective in all cases of expansion level than square and triangular grooves. For the semi-circular grooves, a maximum of 48.5% reduction in the supersonic core length of the correctly expanded jet at nozzle pressure ratio (NPR) of 5 is achieved. The reduction in the supersonic core length for semi-circular grooves is 31% for the overexpanded jet at NPR 4 and 29% for the underexpanded jet at NPR 7.

Study on Characteristics of Special ICP-Heated Wind Tunnel by Improved HCN Laser Interferometer

The results of the experimental investigation of a plasma jet created by a large-volume, high-enthalpy plasma wind tunnel are presented. The plasma wind tunnel generates an electric field by applying a time-varying power with a frequency of 440 kHz, which excites the plasma and ejects it from the nozzle due to the pressure difference. This article uses high-voltage probes, cameras, and laser interferometers to understand the properties of plasma wind tunnels. In order to diagnose the electron density at different positions of the plasma jet, a laser interferometer is improved in this article. The waveform of the power supply, the length of the plasma jet, and the brightness and electron density of the plasma jet were obtained during the experiment. The results show that the electron density increases by about an order of magnitude when the supply voltage rises from 8 to 12 kV. As the distance increases by 150 mm, the plasma electron density decreases by a factor of 1.5 or 2, but the electron density increases with the increase of pressure. Finally, the electron density distribution characteristics can be explained by the simulation results.

Analisis Karakteristik Aliran Irigasi Perforasi Pada Lahan Datar

Perforation irrigation is a unidirectional beam irrigation system that can be used for crop irrigation on dry land, due to the efficient use of water and the ability to wet land with a limited area. Therefore, the perforation irrigation system needs to be studied further in relation to the area of land that can be irrigated and the distribution of discharge to each perforated pipe. By testing several variations of the water level, the perforation irrigation emission capability will be obtained in the form of irrigation distribution, uniformity, emission capability and discharge amount used in irrigation on flat land. This study aims to determine the perforation irrigation capacity on flat land, the distribution of irrigation and the amount of discharge required. The test was carried out on three perforated pipes made of ½” PVC as lateral pipes, three transmission pipe length variations, such as 0.8m, 1m, and 1.2m with a distance between the perforations of 60 cm. The source of irrigation water comes from a 3 m tall tower with a capacity of ± 200 𝑙𝑖𝑡𝑒𝑟. The test uses three variations of head height, namely h1 350 cm, h2 360 cm, h3 370 cm and h4 380 cm. The results showed that the perforation irrigation jet length was around 100cm -120 cm, the uniformity of CU irrigation was above 97% with a total discharge on h1 QT = 0.689 lt/s, h2 QT = 0.690 lt/s , h3 QT = 0.695 lt/s and on h4 QT = 0.701 lt/s. While the range of flow rates for perforation 1 pipe Q1 (0.42 lt/s – 0.429 lt/s), perforation 2, Q2 (0.13 -0.145 lt/s) and perforation 3, Q3 (0.129 - 0.135 lt/s)

Microwave atmospheric pressure plasma jet generated from substrate integrated waveguide resonator

AbstractA microwave atmospheric pressure plasma jet (MW‐APPJ) generator based on a substrate‐integrated waveguide (SIW) resonator is proposed. A thin, straight plasma needle with a length of 9 cm could be obtained. Higher than 90% of microwave feeding efficiency is obtained under a wide range of gas flow rates without a microwave matching network. As the gas flow increased from 1 to 14 L/min, a transition from laminar to turbulent mode is observed in the plasma jet's morphology. Furthermore, a preliminary surface treatment was tested for the device. The polyimide film became super hydrophilic after a 5‐min treatment with the developed SIW‐based plasma generator. Generally, the SIW‐based MW‐APPJ is low‐cost, electrodeless, and low‐profile along the plasma jet length direction.

Influence of structural parameters of needle-ring electrode on the length of argon plasma jet under atmospheric pressure

In this paper, a multi-structure needle-ring electrode argon plasma jet device was designed to investigate the influence of reactor structure parameters and discharge parameters on the length of atmospheric pressure non-equilibrium plasma jet. Specifically, the effects of the discharge voltage, the electrode gap, the distance between the end of the high-voltage electrode and the ground electrode, and the volume flow of argon on the jet length were explored. The results demonstrate that the maximum length of the plasma jet in the external environment can reach 80 mm when the inner diameter of the tube is 15 mm; the jet length first increases and then tends to be stable with the increase in the discharge voltage; the jet length presents two peaks with the increasing voltage; the end of jet appears the unstable phenomenon of ‘beating’ when the discharge voltage is high. Besides, the longer the distance between the end of the high-voltage electrode and the ground electrode, the longer the jet length. Nevertheless, the relationship between the distance and the jet length is non-linear. The jet length first increases and then decreases with the increase in the electrode gap. The phenomenon of ‘particle countercurrent’ is observed when the electrode gap and discharge voltage are relatively large. With the increase in the argon volume flow, the plasma jet length also exhibits a trend of first increasing and then decreasing. To sum up, the main factors affecting the length of the plasma jet is transport mode during the plasma transport process.

Molecular dynamics simulation of ethanol electrohydrodynamic atomization: Microscopic mechanism of the operating parameter effects

Electrohydrodynamic (EHD) atomization is a physical process, in which a liquid subjected to an external strong electric field and pumped through a capillary tube, disintegrates into monodisperse fine drops. In present work, EHD atomization behaviors under various operating parameters were numerically investigated using molecular dynamics (MD) methods. Good agreement was obtained between the MD simulations and the previous experimental work. The effects of electric potential, liquid flowrate, sodium chloride concentration and temperature on EHD atomization process were systematically examined, analyzed and discussed from the microscopic perspective. The results show that the jet length and the number of ethanol molecules ejected from capillary tube increased with an increase in electric Bond number. As the electric Bond number increases, the interaction between ethanol molecules decreases, and the hydrogen bond number reduces. As the Weber number increases, the jet length also increases, and the jet morphology may change from ‘plump’ to ‘sharp,’ and finally disrupts into liquid fragments. Sodium chloride plays an important role in the formation of atomization mode. With increasing ions concentration, a continuous jet can convert into dripping, which results from that the ions could destroy the stable structure of hydrogen bond among ethanol molecules. Furthermore, the ethanol clusters would gradually increase in size as the sodium chloride ion concentrations increasing. In addition, the movement of cations is inseparable from the breakup of the jet. The trend of individual atom motion in an ethanol molecule increases with an increase in temperature. This work provides a microscopic insight into EHD atomization and will be potentially useful for optimizing operating parameters and improving efficiency.

Decrease in volcano jet noise peak frequency as crater expands

Volcanic jet noise is the sound, often <20 Hz and termed infrasound, generated by momentum-driven fluid flow through a volcanic vent. Assuming the self-similarity of jet flows and audible jet noise extends to infrasonic volcanic jet noise, the Strouhal number, St, connects frequency changes to those in jet length (expanded jet diameter) and/or velocity scale (jet velocity). We examine the infrasound signals from the June 2019 eruptions of Raikoke, Kuril Islands and Ulawun, Papua New Guinea volcanoes with changes in crater geometry. We use data from the International Monitoring System infrasound network and pre- and post-eruption satellite data (PlanetScope imaging). We observe a decrease in infrasound peak frequency during the transition to a more intense phase, which remains through the end of both eruptions. With the PlanetScope data, we measured a crater area increase of ∼50 000 m2 at Raikoke and ∼31 000 m2 at Ulawun. We use crater diameter as a proxy for expanded jet diameter. Our analysis suggests that the increases in crater diameter alone cannot account for the decreases in peak frequency for a constant St. This suggests the jet velocity also increased, which fits satellite data, and or the fluid properties (e.g., particle loading, nozzle characteristics, etc.) changed. This is reasonable as the eruptions intensified, which likely involved an increase in jet velocity and erosion of the crater walls. This is the first study to corroborate the decrease in infrasound peak frequency with documented increase in crater area.

Jet Formation Characteristics of the Reactive Material Composite Liner Shaped Charge

The formation characteristics of reactive material (RM) composite jet were studied by finite element software AUTODYN. The effect of diameter and thickness ratio, and cone angle of the liner on the tip velocity of composite jet and effective jet length were investigated. In numerical simulations, with increasing of the ratio of liner diameter, the ratio of liner thickness and the liner cone angle, the tip velocity of the composite jet decrease. With increasing of the liner cone angle, the effective length of composite jet decreases. But it is almost independent of the liner diameter and thickness ratio. When the liner diameter ratio is 0.6-0.8, the liner thickness ratio is 0.1-0.2, and the cone angle of composite liner is 60°-80°, the comprehensive performance of the RM-composite jet is better.

The influence of electrodes thicknesses on the characteristics of a helium plasma jet

An atmospheric plasma jet reactor (PJR) was designed using two outer disc-like copper plats placed around a quartz tube. The effects of the electrodes’ thicknesses and their placement on the plasma jet length created in helium and its electrical characteristics were investigated. Measurements of the plasma jet length were carried out for different applied voltages and different gas flow rates. The electrical characteristics (such as discharge current and power consumption) of the plasma jet obtained using a high voltage generator delivering a sin-wave signal varying from 13kVp-p to 17kVp-p at a resonance frequency of 5.5kHz, were measured/calculated. The best results (long plasma plume and intense plasma) were obtained with a reactor equipped with a thicker upper electrode and a thinner lower electrode. Using this configuration, a plasma plume 55mm long was reached at 17kVp-p and 7slm of helium.

Numerical study on thermal and hydraulic performance of a stacked-plate jet-impingement/microchannel heat sink

This paper presents a stacked-plate jet impingement microchannel (SP-JIMC) heat sink with highly-dense micro-fins and numerically investigates the thermal and hydraulic performance with single-phase water as coolant. Comparative analysis with the parallel microchannel heat sink and the micro-gap heat sink indicates that the SP-JIMC can achieve a better cooling performance and improve the temperature uniformity. With the inlet water temperature of 300 K and flow rate of 1 L/min, SP-JIMC has a thermal resistance of 0.45 cm2⋅K/W and a pressure drop of 208.2 Pa, and the maximum temperature difference is 2.2 K under 100 W/cm2 over a span of 35 mm. When the flow rate is increased to 10 L/min, the thermal resistance decreases to 0.21 cm2⋅K/W, and the pressure drop increases to 5085.9 Pa. The heat transfer analysis shows the micro-fins dissipate 77.5 % with a flow rate of 1 L/min. As the flow rate increases to 10 L/min, the jet impingement heat transfer is enhanced and the percentage of heat transfer over micro-fins drops to 56.2 %. Parametric study is performed to investigate the influence of structural parameters on the heat transfer characteristics. The results show the thermal performance is improved by increasing jet length and separator thickness, and reducing separator gap. The lowest thermal resistance is achieved at a jet width of 0.35 mm when the combined effects of jet impingement and micro-fins reach the optimum situation. In order to further improve the thermal performance of SP-JIMC, dual-side micro-fins and convex/concave impinged surfaces are simulated. The results show that adding the micro-fins on the out-flow plate can increase the heat transfer percentage over fins by 9.4 % and reduce the thermal resistance to 0.39 cm2⋅K/W under a flow rate of 1 L/min. The maximum heat transfer capacity is achieved when the inlet flow rate 35 L/min under 300 W/cm2 heat flux, the average temperature of the heating surface is 349.5 K, the pressure drop is 55.1 kPa and the thermal resistance is 0.165 cm2⋅K/W.

An experimental study of liquid micro-jets produced with a gas dynamic virtual nozzle under the influence of an electric field.

The results of an experimental study of micro-jets produced with a gas dynamic virtual nozzle (GDVN) under the influence of an electric field are provided and discussed for the first time. The experimental study is performed with a 50% volume mixture of water and ethanol, and nitrogen focusing gas. The liquid sample and gas Reynolds numbers range from 0.09-5.4 and 0-190, respectively. The external electrode was positioned 400-500μm downstream of the nozzle tip and an effect of electric potential between the electrode and the sample liquid from 0-7kV was investigated. The jetting parametric space is examined as a function of operating gas and liquid flow rates, outlet chamber pressure, and an external electric field. The experimentally observed jet diameter, length and velocity ranged from 1-25μm, 50-500μm and 0.5-10m/s, respectively. The jetting shape snapshots were processed automatically using purposely developed computer vision software. The velocity of the jet was calculated from the measured jet diameter and the sample flow rate. It is found that micro-jets accelerate in the direction of the applied electric field in the downstream direction at a constant acceleration as opposed to the standard GDVNs. New jetting modes were observed, where either the focusing gas or the electric forces dominate, encouraging further theoretical and numerical studies towards optimized system design. The study shows the potential to unlock a new generation of low background sample delivery for serial diffraction measurements of weakly scattering objects.

Performance of an engineered combination of plunging jet with stirred tank part I: Single impeller system

The present work proposes a new combination of two conventional reactors with the objective of developing improved gas-liquid/gas-liquid-solid reactor. Thus performance of plunging jet/s coupled with conventional mechanically agitated contactor (MAC) has been investigated experimentally by standard parameters. Plunging jet/s was/were used as a means to introduce gas phase into conventional MAC instead of a sparger. The plunging jet/s was/were located in such a way that the gas plunged-in by the jet can be sucked-in and efficiently dispersed by the impeller. Experiments were performed in 1 m i.d. stirred tank and power consumption was varied in the range of 0.05 to 3 kW/m3. Volumetric mass transfer coefficient (kLa), specific power consumption (PG/V) and the gas hold-up (ЄG) was measured for disk turbine (DT), Pitched blade downflow turbine (PBDT) and hydrofoil impeller for two different jet diameter and length of the jet and two number of jets. The performance of proposed reactor has been compared with gas inducing (GIC) and conventional MAC. The performance of proposed reactor was found to be superior as compared to conventional MAC and GIC.

Effect of varying velocity ratio and separation distance on thin lip coaxial jet

Purpose In comparison to a nozzle with a larger/finite separation distance (Thanigaiarasu et al., 2019), a thin-lip nozzle (Srinivasarao et al., 2017) minimizes drag. Coaxial nozzles with thin lips are an appropriate tool for studying high subsonic jets because it does not create a dominant re-circulation zone. This study aims to analyze the characteristic of separation distances, between primary and secondary nozzles, within the range of 0.7–3.2 mm which can be considered a thin lip. Design/methodology/approach A separation distance of 0.7 (Papamoschou, 2004), 1.7 and 2.65 mm (Lovaraju and Rathakrishnan, 2011) is considered for the present study. The main nozzle exit Mach number is maintained at a subsonic condition of Mach 0.6, and the co-flowing nozzle exit Mach number is varied from 0% (secondary jet stopped/single jet) to 100% (Mach 0.6) in steps of 20% with respect to the main nozzle exit Mach number. A comparison was made between these velocity ratios for all three lip thicknesses in the present study. Design mesh and analysis were done by using Gambit 2.6.4 and Fluent 6.12. Velocity contours and turbulence contours were studied for qualitative analysis. Findings When lip thickness increases from 0.7 to 2.65 mm, the potential core length (PCL) of the primary jet decreases marginally. Additionally, the PCL of the primary jet elongates significantly as the velocity ratio increases. The primary shear layer is dominant at 20% co-flow (20 PCF), less dominant at 60% co-flow (60 PCF) and almost disappeared at 100% co-flow (100 PCF). Concurrently, the secondary shear layer almost disappeared in 20 PCF, dominant in 60 PCF and more dominant in 100 PCF. Different zones such as initial merging, intermediate and fully merged zones are quantitatively and qualitatively analyzed. Practical implications Co-flow nozzle is used in turbofan engine exhaust. The scaled-down model of a turbofan engine has been analyzed. Core length is directly proportional to the jet noise. The PCL signifies the jet noise reduction in a high-speed jet. For a low-velocity ratio, the potential core is reduced and hence can reduce the jet noise. At the same time, as the velocity ratio increases, the mass flow rate of the coaxial increases. The increase in the mass flow increases the thrust of the engine. The aircraft engine designer should analyze the requirement of the aircraft and choose the optimal velocity ratio coaxial nozzle for the engine exhaust (Papamoschou, 2004). Originality/value There have been many research studies carried out previously at various lip thickness such as 0.4 (Georgiadis, 2003), 0.7 (Papamoschou, 2004), 1.5 (Srinivasarao et al., 2014a), 1.7 (Sharma et al., 2008), 2 (Naren, Thanigaiarasu and Rathakrishnan, 2016), 2.65 (Lovaraju and Rathakrishnan, 2011), 3 (Inturiet al., 2022) and 3.2 mm (Perumal et al., 2020). However, there is no proper study to vary the lip thickness in this range from 0.7 to 3.2 mm to understand the flow behavior of a co-flowing jet.

Extremely long nanojet formation from a ballpoint photonic pen

Certain microelements can facilitate light manipulation in the form of an intense electromagnetic beam known as a “photonic nanojet” (PNJ), which is an emerging candidate in the field of spectroscopy, nanolithography, and bio/chemical sensing. However, inherent limitations of the PNJs such as short jet length, focal point, and working length minimize their application areas. Herein, by considering readily available materials and technologies, we report a simple and physically realizable “photonic pen” (PP)-like microstructure to yield extremely long PNJs under plane-wave illumination. Essentially, by semi-immersing a sphere of certain diameter (acting as pen tip) in a barrel material with the width equal to and height 5 times the sphere diameter, a “ballpoint pen”-like microstructure is formed where illuminated light acts as the ink. Finite-difference time-domain analysis shows the use of low refractive index (RI) spherical tips ( n = 1.48 ) with 10 µm diameter, and a high RI SU-8 barrel ( n = 1.62 ) creating a net index difference of Δ n = 0.14 to effectively form PNJs with extremely long jet length, working distance, and full width at half-maximum of over 330 λ (121.6 µm), 319.45 λ (116.6 µm), and 4.22 λ (1.54 µm) respectively, and a figure of merit of ∼ 155 in water environment. S i O 2 / SU- 8 PPs show over ∼ 3 times longer jet length than previous studies. We show that such SU- 8 / SiO 2 PPs with extremely long PNJs can act as epidermal photonic imagers to scan biological tissues such as trilayer human skin to detect melanoma (skin cancer), both in contact and in noncontact mode with efficiency enhancement reaching ∼ 45 % compared to plain microspheres without barrels.

Supersonic Shrouding Methane Mixtures for Supersonic Combustion Coherent Jets

A coherent jet oxygen supply plays a key role in the process of electric arc furnace steelmaking: it provides the necessary oxygen for the smelting of molten steel and promotes the flow of the molten pool. Compared with coherent jets in current use, the supersonic combustion coherent jet shrouded in supersonic methane gas could improve the impact capacity and stirring intensity of the molten pool. In order to reduce the smelting cost, the characteristics of the supersonic combustion coherent jet shrouding the supersonic methane and nitrogen mixtures must be studied. Computational fluid dynamics software is used to simulate the supersonic combustion coherent jet under various methane–nitrogen mixing conditions. The six-component combustion mechanism of methane and the Eddy Dissipation Concept combustion reaction model are selected. In agreement with thermal experiments, the simulation results show that the inclusion of a small amount of nitrogen has little effect on the combustion of supersonic shrouding methane gas. However, as the nitrogen content increases, the combustion region of supersonic shrouding gas becomes shorter in length, resulting in decreases in the lengths of the high-temperature, low-density region, and the high-turbulence-intensity region. These effects weaken the ability of the shrouding gas to envelop the main oxygen jet. The potential core length of the main oxygen jet decreases significantly; this decrease first accelerates and then decelerates. These results demonstrate the feasibility of including a small amount of nitrogen (about 10 wt%) in the supersonic shrouding methane gas without substantial negative impacts on the characteristics of the supersonic combustion coherent jet.