Forced Jet Research Articles

Interfacial structure and properties of anodized 6061 Al alloy joints by ultrasonic-assisted hot dipping and soldering using a Sn–9Zn–2Al filler metal

Al alloy joints soldered with Sn-based filler metal are susceptible to corrosion and early failure when exposed to moisture, resulting in severe accidents and substantial economic losses. This study proposes a method to prevent galvanic corrosion by separating Al alloys and Sn-based filler metals with an insulating barrier layer of anodized aluminum oxide (AAO) composed of Al2O3. The successful joining of anodized aluminum alloy (AAA) with Sn–9Zn–2Al was achieved through ultrasonic-assisted hot dipping and soldering in air at 240 °C. Microstructural examination revealed strong bonding between the solder alloy and AAO, with the solder infiltrating the AAO nanotubes and a transition layer consisting of two sublayers at the interface: amorphous ZnO mixed with nanocrystals (ZnO and Al2O3) and amorphous Al2O3. The shear strength of the joints ranged from 31.8 to 32.8 MPa when subjected to ultrasonic hot dipping for 0.5–2.0 s, with no significant difference observed. Fracture initiation and propagation occur within the transition layer at the interface. The shear strength of joints subjected to dipping for more than 3.0 s decreased slightly to 27.9 MPa due to localized peeling off of AAO from the Al substrate. The formation of the interface involves the segregation of Al and Zn on the liquid filler metal surface, driven by differences in atomic activity. Due to the jet force from cavitation, an Al-rich liquid infiltrates the nanotube, resulting in the formation of Zn–O at the interface and Al–O both at the interface and within the nanotube. Throughout this process, the wetting model shifts from a Cassie state to a near-Wenzel state. Immersion tests of two types of joints, Al/SnZnAl/Al and AAA/SnZnAl/AAA, confirmed that galvanic corrosion of Sn/Al was completely inhibited by the latter. Consequently, AAA joints demonstrate excellent corrosion resistance, validating this approach as a promising solution to the Al/Sn galvanic corrosion issue.

Nozzle Wear in Abrasive Water Jet Based on Numerical Simulation.

Particle diameters and jet pressure in abrasive water jet (AWJ) are significant jet properties which deserve a better understanding for improving AWJ machining performance. Some influence factors have been verified regarding nozzle wear in abrasive water jet polishing application. A three-dimensional model of a nozzle is established to analyze the influence of internal multi-phase flow field distribution, which is based on Euler-Lagrange methodology. With the increase of jet pressure, the erosion rate decreases; with the increase of the diameter and mass flow rate of the erosion particles, the erosion speed increases as well. When the diameter of the outlet is worn to 1.6 mm, the pressure on the work piece caused by the abrasive water jet increases by more than double compared to the non-worn nozzle; when the diameter of the nozzle outlet is worn to 1.6 mm, the shear force is 2.5 times higher than the shear force when the diameter is 1.0, which means that the jet force is divergent when the diameter is 1.6 mm, and the damage of the work piece is very serious. The obtained results could improve polishing efficiency on the work piece, extend nozzle lifetimes, and guide the future design of AWJ nozzles.

CARING: Cannula for Alleviation of Retinal Injury Caused by Needle Fluidic Gashing.

Infusion-related iatrogenic retinal breaks (IRBs) are a significant complication in vitrectomies, particularly when smaller-gauge cannulas are used during fluid infusion. Using two-dimensional finite element analysis (FEA), we analyzed forces exerted on the retina from different cannulas: traditional 25-gauge, 20-gauge, 23-gauge, and 27-gauge, then investigated four alternative new cannula designs: (A) oblique orifices, (B) external obstruction, (C) side ports, and (D) perpendicular orifices. The analysis revealed that the standard 25-gauge cannula had a force of 0.546 milli-Newtons (mN). Optimized cannulas demonstrated decreased forces: 0.072 mN (A), 0.266 mN (B), 0.417 mN (C), and 0.117 mN (D). While all the designs decrease fluid jet force, each has unique challenges: Design A may complicate manufacturing, B requires unique attachment techniques, C could misdirect fluid toward the lens and peripheral retina, and D requires a sealed trocar/cannula design to prevent unwanted fluid ejection. These four innovative cannula designs, identified with detailed engineering simulations, provide promising strategies to reduce the risk of IRBs during vitrectomy, bridging the gap between engineering insights and clinical application.

Comet 81P/Wild 2: Changes in the spin axis orientation during the last five apparitions

Comet 81P/Wild 2 is characterized by the presence of a prominent fan-shaped dust emission originating from an active source at high latitude on the nucleus, whose axis is assumed to coincide with the comet's rotation axis. Therefore, several authors estimated the spin axis orientation of 81P in past apparitions based on the polar jet model.By measuring the PAs of the fan on CCD images taken with different telescopes during the 2009–10 and 2022–23 apparitions, we estimated a position of the comet's spin axis at RA = 295.0° ± 7.5°, Dec = 14.5° ± 4.0° for the 2009–10 apparition and at RA = 296.7 ± 2.0°, Dec = 17.3 ± 2.5° for the 2022–23 apparition. Despite some degree of uncertainty of the estimate for the 2009–10 apparition, we interpolated the estimate for 2009–10 and 2022–23 with the published data of the previous apparition of 1997, to assess the presence and the extent of a drift of the pole since the 1997 passage.The analysis over a long time span of five consecutive apparitions confirms previous observations that the spin axis of comet 81P is subject to a slow drift with variable rate, probably connected to outgassing-induced jet forces and the related non-gravitational perturbations of its orbital period.

A numerical study of rectification driven by a tidal jet

The barotropic tide in fjords is often assumed to play a negligible role in driving the circulation over timescales greater than the tide itself, the residual circulation. However, this is not necessarily true when the tide interacts with the fjords’ topography. Of particular interest are narrow channels, where the tide can excite non-linear flow features such as flow separation eddies and establish a tidal jet. The jet and associated eddies are known to influence transport through the channel and dominate local dispersion. We investigate how the jet can influence the residual circulation in Kvænangen, a Northern Norwegian fjord. We model the flow dynamics using an unstructured grid ocean model, solving the shallow water equations. The model results show that the jet can drive residual currents around the fjords basin if the jet forces a vorticity flux across closed bathymetric contours. We demonstrate that the rectification is sensitive to how the channel is represented in the ocean model. With a wide channel, the fjord-scale residual circulation diminishes. Our work thus highlights the importance of accurately resolving the actual geometry of the coastline, since small-scale flow phenomena generated in narrow channels can force a far-field circulation response and consequently influence the drift of tracers in the fjord.

The Formation Mechanism and Suppression Strategies of Spatter in Pulsed Gas Metal Arc Welding for Titanium Alloy

The GMAW process for titanium alloy is not commonly applied within the industry due to the occurrence of severe spatter. This research endeavors to elucidate the mechanism underlying spatter formation and explore efficacious strategies to suppress spatter. The experimental results demonstrated the existence of two distinct spatter types: large and small spatter particles. The high- speed images and synchronous electrical signals were utilized for determining the spatter formation mechanism, with force analysis serving to mutually validate the inferences. The large spatter particles originated from the whole transitional molten droplet as it descended within the arc space, while the small spatter particles were formed by the partial transitional molten droplet as it contacted the weld pool. The cathode jet force accounted for the formation of large spatter particles, whereas the electromagnetic force was responsible for the small spatter particles. To suppress spatter, increasing detachment current and decreasing pulsing frequency were employed. Consequently, the spatter rate witnessed a remarkable decrease from 14.00% to 3.33% with a progressive increment in detachment current from 100 A to 300 A, and a corresponding decline from 12.67% to 1.33% upon decrementing the pulsing frequency from 90 Hz to 50 Hz. This research suggests that a judicious increase in the detachment current can effectively decrease the spatter rate while concurrently preserving welding efficiency.

Numerical investigation of the instability of dry granular bed induced by water leakage

AbstractUnderground pipe defects or cracks under transport infrastructure can cause water leakage to upper soil layers (e.g. subgrade and capping), inducing local cavities or even failure of overlying road/railway formation. Although numerous studies on the instability of granular beds induced by injected water have been conducted, most of them focused on the behaviour of saturated granular beds, while research on dry granular beds is still limited. This paper aims to address this gap using a numerical model coupling volume of fluid method with discrete element method. We observed that dry granular beds go through three distinct regimes as water jet velocity increases including stationary, stable deformation with heave and fluidisation. However, the flow velocities required to deform and fluidise dry granular beds are significantly higher than those required for saturated beds. Increasing granular bed thickness can alter its failure mechanism from full depth to localised erosion, leading to cavity formation around pipe cracks prior to the bed fluidisation. The gravitational and frictional components of granular mass are identified as two main resisting forces of dry granular beds against water jet force, evidenced by the increase of critical jet velocities as particle density and friction coefficient increase. Nevertheless, the moblised zone of granular mass is practically independent of both the buried depth of dry granular beds.

The role of opened fire doors in enhanced heat exchange of long-distance utility tunnels

Due to their distinctive structural attributes, fire compartments in utility tunnels result in regions of increased temperature concentration and thermal dissipation, notably influencing heat exchange phenomena. Investigating airflow diffusion and thermal exchange principles of fire compartments is important when optimizing heat transfer processes in extensive utility tunnels. In this study, we employed numerical simulations and rigorous experimental validation to compare velocity and temperature field attributes between conventional tunnels and those augmented with fire compartments under diverse boundary conditions. The findings revealed that substantial ventilation exchange, reduced cable-based thermal exchange, diminished wall temperatures, and incorporation of opened fire doors are effective measures in improving the thermal environment in utility tunnels. During the summer season, it was observed that the temperature prerequisites were adequately met in a 400-m-long utility tunnel featuring cross-fire compartments at a ventilation rate of 4 air changes per hour (ACH), while tunnels surpassing a length of 600 m required a ventilation rate of 2 ACH, and single-fire compartment tunnels required a ventilation rate of 6 ACH for similar thermal control. Specifically, at a rate of 2 ACH, the temperature in the tunnel exhibited an average reduction of 3.25 °C with the addition of one additional opened fire door. In comparison, a decrease of 1.91 °C was observed when maintaining a rate of 4 ACH. Finally, the airflow characteristics of tunnels with normally opened fire doors were summarized via a finite forced jet model, and the specific ranges of the potential flow core region, characteristic attenuation region and radial attenuation region were obtained.

Machine learning algorithms to study the relative roles of jet convection and natural convection in the presence of surface roughness elements on enhancement of jet impingement heat transfer

Based on data-driven approaches, eight machine-learning algorithms have been proposed to characterize the heat transfer performance of turbulent jet impingement cooling. These algorithms are designed to cool high-heat-flux surfaces modified with single protrusions, multi-protrusions, or V-grooves. To train these algorithms, an experimental dataset was used, which included 184 experiments with Reynolds numbers ranging from 10,000 to 33,000, nozzle exit-to-plate distances ranging from 2 to 10 jet diameters, and two different heat inputs of 60 W and 90 W. Multiple linear regression algorithms in Python programming were used to model jet impingement cooling, showing that the proposed machine learning models provided more accurate predictions with a 20.4 % to 66.5 % relative residual improvement over the existing conventional regression model based on performance metrics like R2 and relative residual. This improvement was leveraged to quantify natural convection's impact on the effectiveness of heat transfer enhancement due to different types and sizes of roughness elements in high-temperature applications. The research found that as the protrusion surface area increased from 0.02 % to 0.188 % compared to the flat plate, the effectiveness of heat transfer enhancement decreased from 2.69 % to 8.37 % at similar operating conditions. These results revealed that natural convection, which opposes forced jet impingement, was strengthened with increased heat input values, roughness element surface area, and the local turbulence generated. The higher natural convection weakened the enhancement afforded by jet impingement on the modified plates relative to the flat plate. Additionally, the capabilities of machine learning algorithms were explored to unlock the full potential of the jet impingement technique and to overcome the associated complexity in jet impingement applications for next-generation electronics cooling. Finally, the Decision Tree Classifier algorithm was applied to classify the performance of the surface roughness element as either effective or ineffective.

Effect of Diameter on Steam Pressure Sootblower to Eliminate Low Potential Slagging and Fouling

The combustion process in pulverized coal boilers utilizes coal fuel, which produces ash and heat. Ash from combustion process will be deposited and adhere to pipes, known as slagging and fouling. Cleaning of slagging and fouling is done using a sootblower by flowing pressurized fluid to generate a jet nozzle force, which can remove the slagging and fouling adhering to the pipes in the superheater. Based on testing of parameters, ash fusion temperature is 1415.42 oC, and silica ratio is 79.55%, indicating a low potential for slagging. For fouling testing yielded an index of 0.089, indicating a low potential for fouling. The existing retractable sootblower operates using superheated steam with a pressure of 70-75 bar. In the design of low-pressure sootblower, flow is derived from intermediate pressure turbine by modifying feed tube, lance tube, and sootblower nozzle. The design results in a feed tube diameter of 101.65 mm, a lance tube diameter of 114.3 mm, an inlet nozzle diameter of 21.1 mm, a throat nozzle diameter of 13.97 mm, and an outlet nozzle diameter of 41.02 mm, with a Mach number output of 2.09 and a total jet force of 2023.9 N.

Forced Injection of a Spanwise-Inclined Jet in Supersonic Crossflow

Beneficial effects of forced air-jet vortex generators in controlling shock-induced flow separation motivated us to study forced jet injection in detail to understand the advantageous control effects. We performed implicit large-eddy simulations to examine the influence of sinusoidally forced injection of a spanwise-inclined jet in supersonic crossflow. Two forcing frequencies were considered (with and 0.0062) in a crossflow at Mach 2.5 and momentum-thickness Reynolds number of 7000. The underexpansion of the jet has a near-linear dependence on the injection pressure. Consequently, in the near field, the major vortices pulsate with the injection pressure. Statistical analysis using triple decomposition revealed that periodic oscillations of the major counter-rotating vortex pair (CVP) result in momentum transfer by major CVPs, also on their lateral sides, leading to enhanced mixing and lateral spreading, which is beneficial for separation control. Three-dimensional dynamic mode decomposition revealed that forced injection induces a large-scale clockwise rotation of the major vortex. These effects are weak at low forcing frequency. High-frequency jet forcing thus leads to more efficient control of flow separation. On the other hand, periodic oscillations cause these vortical structures to dissipate and breakdown faster in the midfield region than for steady jets. The placement of forced jets is therefore an important parameter when used for separation-control purposes.

Computational Fluid Dynamics Analysis of Jet-Ullage Interactions During Microgravity Mixing

Forced jet mixing with and without cooling has long been proposed for active pressure control of cryogenic tanks in microgravity. In this paper, a three-dimensional two-phase computational fluid dynamics (CFD) model is presented that was developed to capture the intricate dynamic interaction between a forced liquid jet and the ullage interface under weightlessness conditions. The CFD model is validated against the microgravity results of the Tank Pressure Control Experiment. The volume-of-fluid method is used to capture the ullage deformation as well as movement in the jet mixing simulations of the microgravity experiment. Two different initial ullage positions are considered, and computational results for the jet–ullage interaction are compared with a still-image sequence captured from real-time video of the experiment. Parametric simulations over a range of jet Weber numbers indicate four distinct jet–ullage interaction modes from nonpenetrating to fully penetrating, which are corroborated experimentally. Qualitative comparisons also provide good agreement between CFD predictions and experimental results with regard to the main features of the ullage dynamics, such as movement, deformation, and jet penetration during microgravity mixing.

Attenuation of the unsteady loading on a high-rise building using top-surface open-loop control

With the severity and frequency of significant weather events increasing, methods for alleviating unsteady wind loading for high-rise buildings are gaining interest. This study numerically investigates the three-dimensional flow structures around a canonical high-rise building immersed in an atmospheric boundary layer at different oncoming wind angles, using wall-resolved large eddy simulations. A synthetic jet located on the top surface is used as open-loop active actuation with the aim of suppressing the building's side-force fluctuations when exposed to oncoming wind variations. Three different frequencies of jet forcing are considered, all half an order of magnitude larger than the vortex shedding frequency. The behaviour of the synthetic jet and its effect on the building's unsteady side force, time-averaged flow fields and unsteady flow structures are investigated numerically. The synthetic jet actuation is found to reduce the side-force fluctuation of the building, enhance the downwash flow and successfully attenuate the antisymmetric vortex shedding. This was achieved to different extents across the range of oncoming wind angles considered and may motivate future attempts to explore experimental active control strategies for attenuation of unsteady wind loading.

Enhancing the bubble collapse energy using the electrohydrodynamic force

The energy released during the bubble collapse process is used for medical and industrial purposes. The present study investigates the effects of electrohydrodynamic force on the collapse phenomenon near the rigid wall and the enhancement of the collapse energy. A solver in the OpenFoam open-source code is developed based on the volume-of-fluid model, in which the effects of compressibility, energy transfer, and electrohydrodynamic force are included. The developed solver is validated against the available experimental data, and a good agreement is seen. The effects of an electric field on the bubble collapse for the range of the electrocapillary number (CaE) of 0–5.76 and normalized wall distance (γ) of 0.8–2.0 are investigated. The results indicate that the bubble is deformed due to the presence of an electric field, and the values obtained for the maximum velocity and pressure are 33 and 35 times the state without the electric field at γ = 2 and CaE = 5.76, respectively. Also, due to the increase in velocity, the maximum shear stress on the rigid wall is increased up to seven times in the absence of the electric field. Therefore, the jet force obtained from the bubble collapse can be enhanced by applying the electric field in the continuous phase fluid. Also, the correlations are proposed to estimate the jet velocity, pressure, and wall shear stress of bubble collapse in the presence of an electric field.

Пневматические регуляторы на основе эффекта силового действия струи

The paper considers schemes of pneumatic regulators, which operation principle is based on the jet force action effect on the flat plate. The main nodes of such regulators include the plate support and the compensatory circuit of the regenerative feedback forming the basis for building pneumatic control circuits that implement the basic laws of regulation. The proposed devices are able to improve static characteristics due to their linearity. Schemes are provided of aerostatic bearing, regenerative feedback, jet-pneumatic proportional and proportional-integral controllers, precession and differentiation block, proportional integral differential controller and semi-proportional controller.

Study on the downhole measurement method of weight on bit with a near-bit measurement tool

The downhole weight on bit (DWOB) measurement method using a near-bit measurement tool can directly measure the force between the well bottom and drilling bit, which is crucial for safe and efficient drilling. However, its accuracy is highly influenced by the downhole drilling fluid pressure and temperature difference between the inner and outer walls. Previous studies have proposed compensatory methods. However, these methods are either extremely complex or not sufficiently accurate. In this study, we proposed a DWOB measurement method based on the force-strain principle. We theoretically and quantitatively studied the impact of various factors, including fluid pressure and temperature difference, on strain measurements. The results showed that the strain output is linear with respect to axial force, fluid pressure, and temperature difference. Using this linear relationship, we determined the downhole axial force. Subsequently, we combined the linear relationship with that between the DWOB and obtained axial force and derived a final DWOB measurement equation that incorporated the nozzle jet force, flow friction force, and lift force. Finally, we quantified the three forces using drilling-fluid mechanics and applied the proposed method to both a finite-element simulation and a real-field drilling experiment. The calculated DWOB measurement error in the simulation and field experiment was less than ±1000 N and ±5000 N, respectively. In short, the proposed method may be used to achieve improved WOB measurements and can significantly improve the bit life and increase the rate of penetration (ROP).

Mechanisms of air breakdowns for aluminum conductors steel reinforced wire-wire gaps induced by propane jet flames

In recent years, events of transmission line tripping caused by wildfires have occurred frequently in many mountain areas. In order to understand the mechanism of such events, an experimental system for simulating breakdown discharge processes of model wires induced by a simulated fire source is designed. In this experiment, propane jet flame (somewhat like eruptive fires in real wild fires) is used as a simulated flame source. By setting three different gas flow rates and five different wire-wire gaps, discharge breakdown behaviors and characteristics between two ACSR (aluminum conductors steel reinforced) segments in propane flames with three flame zones are explored. The influences of these different factors on the breakdown characteristics and mechanisms of wire-wire air gaps are analyzed. Results show that breakdown voltages increase almost linearly with the increase of wire-wire gaps in continuous zone of the flames for three gas flow rates. For a short wire-wire gap like 5.0 cm, the pilot discharge channels can be formed more easily, stably and completely under a lower voltage and weaker external ionization environment. The propane jet flame conditions are complex and affected by multiple actions like initial jet force (affected by gas flow rate), temperature distribution, soot particle, ion wind. As a result, local electric field will be distorted, a streamer channel is established dependently in different cases. These factors play individual, competitive or synergistic roles at the same time in breakdowns of real ACSR wire-wire gaps.

Струйный преобразователь для автоматизированных систем контроля и управления

The use of the aerodynamic jet force action effect became widespread in designing the automatic sensors for physical and technical parameters of gases and liquids, converters and control devices. This technical solution provides high sensitivity and accuracy of the measured parameters in the rapidly changing processes increasing the speed of work. Introduction of sensors built on the basis of such technical solution is especially important in the automated control systems for fast technological processes, where control over various parameters should be quick and accurate. The paper considers a jet pneumatic optical pressure transducer based on the jet force action effect on a plate, which dimensions are commensurate with those for the jet cross section. Static and dynamic characteristics of the pneumatic optical transducer were determined, where the cumulative parameters were accepted as the quality factor criterion combining the measurements sensitivity with the natural frequency square. Using this criterion, optimal parameters of the sensing element were derived based on the considered aerodynamic effect.

The dynamics of non-premixed flames subjected to a transverse acoustic mode

A non-premixed methane/air flame under a transverse acoustic mode is studied by combining theoretical analysis and numerical simulations to understand the acoustic and flow mechanisms affecting the flame response. The experimental configuration under investigation consists of a combustion chamber, a coaxial injector with coflow, and speakers inducing stationary transverse acoustic waves. Numerical simulations reveal a strong response of the flow in the injector to transverse acoustic excitation, resulting in large fluctuations in the mass flow rates of the fuel and oxidizer streams. An analytical model is developed to describe the acoustic response of the flow in the injector to transverse excitation. This model is employed to describe unsteady inflow conditions in large-eddy simulations for different excitation amplitudes. The simulations show that the injector acoustic coupling must be considered to accurately predict the flame lift-off dynamics. Comparisons of numerical results with experimental measurements reveal similar flame structures arising from the longitudinal forcing and good agreement in the lift-off behavior. Further analyses of the flow field, mixing, and flame structure show that the coflow longitudinal forcing induces vortices that corrugate the stoichiometric surface. In addition, the jet forcing enhances the mixing at greater radial locations. The combination of these two mechanisms results in a periodically increased mixing at the stoichiometric surface, leading to significant heat release rate oscillations near the inflow. This work supports the hypothesis that strong acoustic/flame coupling can be present in non-premixed systems when the injectors are longitudinally excited by transverse acoustic waves.

Retrofitting stoves with forced jets of primary air improves speed, emissions, and efficiency: Evidence from six types of biomass cookstoves

Incorporating jets of forced air into biomass cookstove combustion has been shown to potentially decrease harmful emissions, leading to a variety of designs in recent years. These have shown mixed success in terms of real-world performance, usability, and durability. The Jet-Flame forced draft retrofit accessory was recently developed to implement forced jets of primary air at a low cost into a wide range of types of cookstoves using a small 1.5-W fan housed in a low-cost cast iron body to be inserted beneath the fuel bed of a biomass cooking fire. This research sought to quantify the potential efficiency and emissions performance impacts of the Jet-Flame when installed in six different types of biomass cookstoves (three open or shielded fires and three rocket stoves) versus the natural draft performance of each. The effect of the operating fan voltage was also measured. A series of tests following a modified ISO 19867-1:2018 protocol were performed in the laboratory using the Aprovecho Laboratory Emissions Measurement System (LEMS) equipped with additional oxygen and temperature sensors. Results for each stove carefully tended with a single layer of sticks showed that the global average PM2.5 reduction with the Jet-Flame was 89 % relative to the natural draft cases, with larger relative improvements seen in the most rudimentary stoves. CO was reduced by a global average of 74 %, reaching tier 4 or 5 for all stoves. Thermal efficiency was also improved by 34 % when calculated without taking into account the energy content of the remaining char (or 21 % with char), illustrating the value of burning char to provide cooking energy rather than leaving it unburned in the combustion chamber as is common in many natural draft stoves. Time to boil was also reduced by 8 %. In addition, adjusting the voltage of the jet-flame assisted in modulating firepower, improving the usability of the stove. These results indicate a strong potential for the Jet-Flame to help reduce emissions and fuel consumption in a wide range of cookstove designs at a relatively low cost or need for changes in behavior, fuel, or cooking device. The unit also provides enhanced usability in terms of ease of startup, cooking speed, low PM emissions at high power, and burning char. Additional studies are needed to measure performance in the field and under a variety of operational conditions.