Jet Shape Research Articles

Investigating the Morphology of a Free-Falling Jet with an Accurate Finite Element and Level Set Modeling

This study investigates the morphology of a free-falling liquid jet by using a computational approach with an experimental validation. Numerical simulations are developed by means of the Finite Element Method (FEM) for solving the viscous fluid flow and the level set method in order to track the interface between the fluid and air. Experiments are conducted in order to capture the shape of a free-falling jet of viscous fluid via circular orifice, where the shape is measured optically. The numerical results are found to be in agreement with the experimental data, demonstrating the validity of the proposed approach. Furthermore, we analyze the role of the surface tension by implementing linear as well as nonlinear surface energy models. All computational codes are developed with the aid of open-source packages from FEniCS and made publicly available. The combination of experimental and numerical techniques provides a comprehensive understanding of the morphology of free-falling jets and may be extended to multiphysics problems rather in a straightforward manner.

Electrochemical jet machining in deep-small holes with gas assistance: generating complex features on internal surfaces

Deep-small holes with internal features have important applications in thermal engineering but pose significant difficulties for traditional machining methods. Electrochemical jet machining (EJM) is an effective surface micromachining technique with numerous merits. Applying EJM to create complicated features on the internal surface of deep-small holes is attractive. However, this concept remains challenging due to the narrow and enclosed processing space. In this work, a novel gas assistance tool is developed to achieve the EJM process in deep-small holes for the first time. The hydrodynamic conditions to realize well-shaped and unsubmerged jets in both open space and deep-small holes using the specifically designed tool are investigated. The appropriate electrolyte flow rate and sidewall orifice dimensions enable the desired jet to be ejected laterally from the tubular cathode sidewall orifice. While in the deep-small hole the assist gas creates a local gas cavity around the orifice to prevent the jet from submerging, forming the jet shape required for EJM and consequently achieving localized machining of the internal surface. Excessive assist gas pressure should be avoided as it causes the jet to incline and deform, resulting in reduced machining accuracy. Furthermore, the influence of the main parameters on machining performance is examined. The developed gas-assisted EJM method demonstrates similar machining characteristics to the conventional EJM process when appropriate gas assistance conditions can produce the well-shaped unsubmerged jet. As such, various features with smooth surfaces and good shape accuracy are successfully machined on the internal surface of deep-small holes.

Jet injection through microneedles for large volume subcutaneous delivery

Subcutaneous (SC) drug delivery offers several advantages over intravenous (IV) delivery including: self-administration, improved patient experience, and reduced treatment costs. Unfortunately, each SC delivery is currently limited to ∼ 2.25 mL with IV administration required when the delivery volume exceeds this value. In this work, we explore a new technique for large volume subcutaneous drug delivery that uses microneedles to break through the epidermis then forms the liquid drug into many small jets that penetrate past the ends of the microneedles and into the subcutaneous (or muscle) tissue. By performing multiple simultaneous injections, this delivery approach avoids the volume limitations of SC delivery, and thus may be able to greatly increase the volume we can deliver to this space. Here, we present a novel multi-jet prototype that forms seven simultaneous jets through 30G needles that have been shortened to have an exposed length of just ∼ 1mm. The jet speed, shape, and volume of jets formed through these microneedles are measured to assess the consistency of jet production through the microneedles. We then perform jet injections of volumes up to 3.9 mL into ex vivo porcine tissue. The results demonstrate the successful delivery (>95 %) of 3.9 mL in just 0.3 s using jet injection performed through microneedles. This volume is almost double the maximum volume of current autoinjectors and the perceived limit for subcutaneous injection (2.25 mL). We also find that jet speeds of 70 m/s and below do not achieve complete delivery of 3.9 mL with our prototype system, and that the addition of microneedles leads to more consistent large volume delivery than equivalent needle-free injections. These results demonstrate the promise of multi-jet injection through microneedles to accommodate volumes much greater than current autoinjectors, and thus potentially allow patient self-administration in many more delivery applications.

Multifrequency polarimetry of high-synchrotron peaked blazars probes the shape of their jets

Multifrequency polarimetry is emerging as a powerful probe of blazar jets, especially with the advent of the Imaging X-ray Polarimetry Explorer (IXPE) space observatory. We studied the polarization of high-synchrotron peaked (HSP) blazars, for which both optical and X-ray emission can be attributed to synchrotron radiation from a population of nonthermal electrons. We adopted an axisymmetric stationary force-free jet model in which the electromagnetic fields are determined by the jet shape. When the jet is nearly parabolic, the X-ray polarization degree is ΠX ∼ 15–50%, and the optical polarization degree is ΠO ∼ 5–25%. The polarization degree is strongly chromatic: ΠX/ΠO ∼ 2–9. This chromaticity is due to the softening of the electron distribution at high energies, and is much stronger than for a uniform magnetic field. The electric vector position angle (EVPA) is aligned with the projection of the jet axis on the plane of the sky. These results compare very well with multifrequency polarimetric observations of HSP blazars. When the jet is instead nearly cylindrical, the polarization degree is large and weakly chromatic (we find ΠX ∼ 70% and ΠO ∼ 60%, close to the expected values for a uniform magnetic field). The EVPA is perpendicular to the projection of the jet axis on the plane of the sky. A cylindrical geometry is therefore practically ruled out by current observations. The polarization degree and the EVPA may be less sensitive to the specific particle acceleration process (e.g., magnetic reconnection or shocks) than previously thought.

Performances of the ITER Pressure Suppression System during unstable steam condensation regimes

Abstract The paper deals with the qualification of the main safety system of the nuclear fusion reactor ITER: the Vacuum Vessel Pressure Suppression System (VVPSS). This safety system manages the Loss of Coolant Accident (LOCA), that could occur in the Vacuum Vessel (VV), avoiding a significant increase of the internal pressure that could breach the primary confinement barrier. Steam condensation occurs at sub-atmospheric pressure. This condition is original respect the usual applications of steam direct condensation in nuclear fission reactors. An extensive experimental research program, funded by ITER Organization, on reduced scale experimental rigs (scale 1/22 and 1/10) have been carried out at the University of Pisa. Unstable condensation regimes occurred during some tests at about 500 g/s of steam mass flow rate (10 % of the maximum steam mass flow rate foreseen for the relevant accidental scenarios). In these conditions, high intensity vibrations of the whole experimental rig occurred. These events can be classified as ‘Chugging’ or Condensation Induced Water Hammer (CIWH). 
The performed tests have been analysed elaborating the images of the video-cameras located in the pool and comparing the steam jet shape with the acceleration values recorded by an accelerometer mounted on the sparger structure.
These elaborations permitted to evaluate the dynamic of bubble collapse, the volume of the developed external bubbles, the collapse frequency as function of thermal-hydraulic parameters. 
Moreover, the paper emphasizes the beneficial effects of non-condensable gases on the unstable condensation regimes. In fact, the non-condensable gas inhibits the occurrences of Water Hammer inside the sparger and eliminates the thermal stratification inside the water pool increasing the turbulence.

Effect of vent size on vented H2/N2/air deflagration

In this work, the coupling of explosion venting (vent size) and inerting (N2) on H2/air deflagration was investigated. Experiments were carried out in a vertical rectangular duct with an upper opening at an initial temperature and pressure of 280 K and 101 kPa, and a vent coefficient Kv was employed to replace the vent size to elucidate its effect on pressure buildup and flame propagation during H2/N2/air deflagration. In the present study, the internal pressure profile is monitored by three pressure sensors, PS1-3, which are installed at the bottom, center, and top of the duct, respectively, and the external pressure profile is obtained by PS4. The results show that the maximum internal overpressure (pmax) recorded by PS1-3 all increase with increasing Kv, but pmax obtained from PS2 and PS3 tend to increase linearly. For a given Kv, the maximum and minimum amplitudes of pmax are measured by PS1 and PS3, respectively. Specifically, the greater the distance between the pressure sensor and the upper opening, the greater the amplitude of pmax. The relationship between the maximum reduced explosion pressure (pred) and Kv is investigated, where pred is defined as the highest pmax for a specific Kv. As Kv increases from 2.2 to 11.9, pred increases from 26.25 kPa to 88 kPa. The maximum external flame velocity (Vext) increases from 83 m/s to 454 m/s with increasing Kv from 2.2 to 11.9. The amplitude of the maximum external overpressure (pext) first increases and decreases with an increase in Kv from 2.2 to 11.9. The formation time (Δt) of pext decreases and then increases and finally decreases with increasing Kv from 2.2 to 11.9. When Kv is increased from 2.2 to 4.1, all external fireballs are presented as mushroom shapes, but the external fireballs are gradually transformed into jet shapes for Kv ≥7.8. Two pressure oscillations, including Helmholtz oscillations and acoustic oscillations, are found. Acoustic oscillations are found in all tests, but Helmholtz oscillations are only observed for Kv ≤ 4.1.

Evidence of stretching/moving sheet-triggered nonlinear similarity flows: atomization and electrospinning with/without air resistance

PurposeThe purpose of this study is two-fold. First, it aims to differentiate the response of a stretching jet encountering a quadratic air resistance from the classical jet shape formed in a frictionless medium. Second, it investigates how the resulting jet forms with and without air resistance, seeking evidence that supports the similarity flows frequently studied for stretching/moving thin bodies under the boundary layer approximation.Design/methodology/approachThis study extends the established electrohydrodynamic stretching jet theory, used to model electrospinning or jet printing in the absence of air resistance, to encompass the impact of the retarding force on the jet stretching in both the cone and final regimes before it impinges on a substrate.FindingsA close examination of the nonlinear governing equations reveals that the jet rapidly thins near the nozzle because of the combined action of viscous and electrical forces. In this region, the exponentially decaying jet receives further support from the air resistance, resulting in a closer alignment with the observed experimental jet. This exponential decay, accelerated by the inversely quadratic speed of the liquid particles, serves as clear evidence for the existence of a similarity flow over an exponentially stretching sheet. Furthermore, in the final regime, the jet stretching exhibits an algebraic decay in the absence of air friction, while with air resistance, it decays exponentially to reach a limiting speed. In the former case, a square root dependence of the stretching jet speed leads to the emergence of a similarity flow over a thin stretching jet, while in the latter case, a Sakiadis’ similarity flow appears over a continuously moving flat surface.Practical implicationsThe analysis goes beyond jet hydrodynamics, delving into the interplay of electrostatic forces (including Coulomb’s law) and quadratic air drag, drawing upon experimental data on glycerol liquid presented in earlier publications.Originality/valueFinally, the asymptotic behavior of the stretching jet under the combined influence of electrostatic pull and its electric currents because of bulk conduction and surface convection is validated through a comprehensive numerical simulation of the nonlinear system.

Improving the Representation of Moisture and Convective Instability in Baroclinic-Wave Channel Simulations

Abstract We present an improved approach to generating moist baroclinically unstable background states for f-plane-channel simulations via potential vorticity (PV) inversion. Previous studies specified PV distributions with constant values in the troposphere and the stratosphere, but this produces unrealistic static-stability profiles that decrease sharply with height in the troposphere. Adding moisture to such environments can yield unrealistically large values of convective available potential energy (CAPE) even for reasonable relative humidity (RH) distributions. In our modified approach, we specify a PV distribution that increases with height in the troposphere and the stratosphere, yielding background states with more realistic values of static stability and CAPE. This modification produces environments that are better suited for representing moist processes, namely, deep convection, in idealized extratropical-cyclone simulations. Also, we present a method for introducing moisture that preserves a specified RH distribution while maintaining hydrostatic balance. Our approach allows for a large degree of control over the initial conditions, as background states with different jet strengths and shapes, average temperatures, moisture contents, or horizontal shears can easily be obtained without changing the underlying PV formula and inadvertently producing unreasonable values of static stability or CAPE. We demonstrate the characteristics of idealized extratropical cyclones developing in our background states by adding localized perturbations that represent an upper-level trough passing over a low-level frontal zone. In particular, we illustrate the impacts of horizontal shear, moisture, and grid spacing on baroclinic-wave development.

Understanding cavitation bubble collapse and rebound near a solid wall

The collapse of cavitation bubbles is known for its intense and aggressive behavior, producing concentrated bursts of energy that can cause erosion, noise, and damage to metallic surfaces and mechanical equipment. However, this concentrated energy also offers significant potential for various applications in biomedical science, industrial engineering, and related technologies. This study presents a comprehensive numerical investigation of the collapse and rebound of cavitation bubbles near a wall using a conservative, compressible multiphase flow model. Laser-generated cavitation bubbles growing, collapsing, and rebounding in distilled water near a wall at three standoff distances were experimentally studied to validate the numerical method. The results show good agreement between the bubble shapes and radii from the numerical simulations and experiments. Additionally, velocity of microjets and thermodynamics of the bubble collapse were validated against the reference data in the literature. Subsequently, the pressure and temperature distributions and jet shapes were examined in detail, exploring the impact of standoff distances ranging from 0.2 to 1.8. A quantitative analysis of the pressure and temperature produced on the wall, as well as the jet velocity and bubble movement during the collapse, was systematically conducted. Jet velocities observed ranged from 30 m/s to 130 m/s, and numerical simulations were compared with experimental data from the literature, showing good agreement. Maximum temperature and pressure induced at the wall center can reach up to 616.2 K and 139.5 MPa, respectively. The detailed analyses in this study provide significant insights into the behavior of cavitation bubbles and the effect of standoff distance on their collapse and rebound near a wall.

Experimental study on effect of submergence depth on steam jet shape characteristics in direct contact condensation

The phenomenon of direct contact condensation is frequently utilized in the industrial sector due to low driving potential requirements and proficient heat and mass transfer characteristics. This experimental study investigates the influence of nozzle submergence depth by condensing steam through a straight pipe (SP) and converging-diverging (CD) nozzle. The effect of operating conditions i.e. steam pressure and water temperature in addition to nozzle geometry were also studied on steam cavity shape characteristics. Six different shapes were manifested including unstable, conical, ellipsoidal, cylindrical, divergent, and double expansion-contraction. The dimensionless penetration length of plumes was observed in a range of 1.46–3.91 and 2.14–4.41 for the CD and SP nozzle, respectively while the maximum expansion ratio was determined to be 1–1.25 for the CD nozzle and 1.16–1.58 for the SP nozzle. It has been observed that jet length increases with an increase in submergence depth, steam pressure, and water temperature. The maximum expansion ratio was observed to decrease with the increase in submergence depth and increase with an increase in steam pressure and water temperature. The empirical correlations for dimensionless penetration length were developed and predicted results were found to be lying between ±10 % and ±7 % for CD and SP nozzle respectively.

On the Water Jet Quality at Part-Load Operation of Pelton turbines

Abstract Pelton turbines with multiple nozzles are characterised by their excellent performance over a wide operating range of mass flow rates. Thus, Pelton turbine manifolds must also be designed to deliver good flow quality to the nozzles at part-load operating conditions to accomplish the expectations. A reduced number of nozzles are opened at low mass flow rate operating conditions, where the choice of the open nozzles depends on the water jet quality generated at the individual nozzles. We investigate the flow phenomena occurring in the manifold with the operation of a reduced nozzle number employing numerical simulations to analyse beneficial nozzle opening selections. The turbulent two-phase flow is predicted by the Volume-Of-Fluid (VOF) approach and the k–ω SST turbulence closure model. Different nozzle operating scenarios are simulated, and the implications on the water jet quality, i.e. deviation and shape deformation, are reported. The results show that the free water jet quality criteria can change drastically at individual nozzle operating conditions because of the velocity changes at the branch line junctions.

Effects of the nozzle structure and fluidized gas composition on the gas-particle two-phase jet characteristic in a powder fuel scramjet

The interaction between nozzle design and fluidization gas composition significantly influences the dynamics within a powder fuel scramjet's combustion chamber. To investigate this relationship, an experimental study utilized high-speed shadow imaging technology to explore the macroscopic aspects of powder fuel injection. The investigation examined various convergence angles, nozzle throat lengths, and fluidized gas compositions. Key findings include: During jet development, powder fuel initially concentrates near the axis, with non-convergence angle nozzles exhibiting longer concentrated distribution periods than convergence angle conditions. Decreasing nozzle convergence angles lead to increased penetration distance, frontal velocity, and radial diffusion distance during the initial stages of jet development. Additionally, stable jet shapes show larger divergence angles as nozzle convergence angle decreases, with the largest divergence angle observed at α=60°. In the initial 0–7 ms of jet development, the powder fuel jet demonstrates greater penetration distance and frontal velocity under certain conditions. Moreover, penetration distance and frontal velocity increase with throat length from 7 to 20 ms, accompanied by changes in divergence angles. Specifically, at a throat length (l) of 2 mm, the near-field divergence angle measures 46.50°, and the far-field divergence angle is 22.25°. Conversely, at l=8mm, the near-field divergence angle is 33.49°, and the far-field divergence angle is 23.21°. The fluidization gas composition minimally affects jet penetration distance and frontal velocity during the initial 0–3 ms. However, due to hydrogen's low density, hydrogen/powder fuel jets exhibit shorter distances and velocities compared to nitrogen/powder fuel jets. Hydrogen fluidization also results in larger divergence angles, particularly in the near field. These findings underscore the importance of nozzle design and fluidization gas composition in optimizing scramjet performance and efficiency.

Mitigation of reentry blackout via gas injection in arc-heating facility

Communication blackouts during atmospheric reentry pose significant challenges to the safety and adaptability of spacecraft missions. This phenomenon, caused by the attenuation of electromagnetic waves by the plasma surrounding the spacecraft, disrupts communication with ground stations or orbiting satellites. Therefore, it is crucial to decrease the plasma density in the vicinity of the spacecraft to ensure an unobstructed electromagnetic wave communication path. This study proposes a methodology that involves the injection of gas from the vehicle’s wall to create an insulating layer near the surface. This thin layer maintains lower temperatures and reduced plasma density, enabling electromagnetic wave propagation without attenuation. Practical experiments were conducted in an arc-heating facility to simulate atmospheric reentry conditions. The results of the experiments provided empirical evidence of the effectiveness of the technique in mitigating communication blackout phenomena. Numerical fluid analysis within the wind tunnel chamber validated the formation of an air film layer near the experimental model owing to the injected gas. Schlieren imaging revealed distinctive jet shapes, which corroborated the findings of the numerical analysis. The wind tunnel tests that simulated atmospheric reentry environments confirmed the formation of an air film layer through gas injection, which substantiates the reduction in communication blackout. These results have the potential to improve communication reliability in space transport.

Asymmetric jet shapes with two-dimensional jet tomography

Two-dimensional (2D) jet tomography is a promising tool to study jet medium modification in high-energy heavy-ion collisions. It combines gradient (transverse) and longitudinal jet tomography for selection of events with localized initial jet production positions. It exploits the transverse asymmetry and energy loss that depend, respectively, on the transverse gradient and jet path length inside the quark-gluon plasma (QGP). In this study, we employ 2D jet tomography to study medium modification of the jet shape of γ-triggered jets within the linear Boltzmann transport (LBT) model for jet propagation in heavy-ion collisions. Our results show that jets with small transverse asymmetry (ANn⃗) or small γ-jet asymmetry (xJγ=pTjet/pTγ) exhibit a broader jet shape than those with larger ANn⃗ or xJγ, since the former are produced at the center and go through longer path lengths while the later are off center and close to the surface of the QGP fireball. In events with finite values of ANn⃗, jet shapes are asymmetric with respect to the event plane. Hard partons at the core of the jet are deflected away from the denser region while soft partons from the medium response at large angles flow toward the denser part of QGP. Future experimental measurements of these asymmetric features of the jet shape can be used to study the transport properties of jets and medium responses. Published by the American Physical Society 2024

On the role of aortic valve architecture for physiological hemodynamics and valve replacement, Part I: Flow configuration and vortex dynamics

Aortic valve replacement has become an increasing concern due to the rising prevalence of aortic stenosis in an ageing population. Existing replacement options have limitations, necessitating the development of improved prosthetic aortic valves. In this study, flow characteristics during systole in a stenotic aortic valve case are compared with those downstream of two newly designed surgical bioprosthetic aortic valves (BioAVs). To do so, advanced three-dimensional fluid–structure interaction simulations are conducted and dedicated analysis methods to investigate jet flow configuration and vortex dynamics are developed. Our findings reveal that the stenotic case maintains a high jet flow eccentricity due to a fixed orifice geometry, resulting in flow separation and increased vortex stretching and tilting in the commissural low-flow regions. One BioAV design introduces non-axisymmetric leaflet motion, which reduces the maximum jet velocity and forms more vortical structures. The other BioAV design produces a fixed symmetric triangular jet shape due to non-moving leaflets and exhibits favourable vorticity attenuation, revealed by negative temporally and spatially averaged projected vortex stretching values, and significantly reduced drag. Therefore, this study highlights the benefits of custom-designed aortic valves in the context of their replacement through comprehensive and novel flow analyses. The results emphasise the importance of analysing jet flow, vortical structures, momentum balance and vorticity transport for thoroughly evaluating aortic valve performance.

JUSTIFICATION OF NOZZLE PARAMETERS OF JET-TYPE WASHING MACHINES FOR CLEANING AGRICULTURAL MACHINES AND UNITS

Agricultural machinery and equipment are exposed to significant contamination by various types of pollutants, some of which can be easily removed, while others require the use of special cleaning agents and machines. To remove these contaminants, a pressurized water jet is used, the biggest disadvantage of such devices is the significant water consumption, so the issue of intensifying the cleaning process of agricultural machinery using a limited amount of water is an important scientific task. Cleaning of agricultural machinery and units from contaminants is a complex technological operation, therefore, there is a need to develop and justify the parameters and operating modes of a high-tech washing device that would ensure high-quality removal of all types of contaminants with high efficiency, minimal water consumption and minimal labor costs. The analysis of cleaning technologies showed that water jet cleaning is the most promising for removing dirt from the surface of agricultural machines and units, the technology allows to increase the level of mechanical impact by using additional energy, which can be the energy of a rotating jet. The study examines the efficiency of cleaning washing plants from various contaminants. The main focus is on studying the impact of nozzle design on the quality and productivity of the washing process. Nozzles determine the shape of water jets and their velocity, determining the cleaning efficiency. The dagger and fan nozzles, their advantages and disadvantages are considered. Nozzle parameters such as orifice diameter, spray angle, and number of fan jets are investigated. It is shown that properly selected nozzle parameters play an important role in achieving the optimal cleaning effect and water saving. Factors such as flow coefficient, drag coefficient, and velocity coefficient that affect the performance and energy of the jet are outlined.

Design and Analysis Method of Piezoelectric Liquid Driving Device with Elastic External Displacement.

In piezoelectric drive, resonant drive is an important driving mode in which the external elastic force and electric drive signal are the key factors. In this paper, the effects of the coupling of external elastic force and liquid parameters with the structure on the vibrator resonance frequency and liquid drive are analyzed by numerical simulation. The fluid-structure coupling model for numerical analysis of the elastic force was established, the principle of microdroplet generation and the coupling method of the elastic force were studied, and the changes in the resonant frequency and mode induced by the changes in the liquid parameters in different cavities were analyzed. Through the coupled simulation and calculation of the pressure and deformation of the cavity, the laser vibration measurement test was carried out to test the effect of the vibration mode analysis. The driving model of the fluid jet driven by the elastic force on the piezoelectric drive was further established. The changing shape of the fluid jet under different elastic forces was analyzed, and the influence law of the external elastic force on the change in the droplet separation was determined. It provides reference support for further external microcontrol of droplet motion.

Optimal standoff distance for a highly focused microjet penetrating a soft material

A needle-free injector using a highly focused microjet has the potential to minimize the invasiveness of drug delivery. In this study, the jet penetration depth in a soft material—which is a critical parameter for practical needle-free injections—was investigated. We conducted jet penetration experiments by varying the inner diameter of the injection tube and the standoff distance between the meniscus surface and the soft material. Interestingly, the results showed that the penetration depths peaked at certain distances from the meniscus, and the positions shifted further away as the inner diameter was increased. By analyzing the velocity distribution of the microjet, the peak positions of the penetration depth and the maximum velocities were inconsistent due to the effects of the jet shape. To account for this, we introduce the concept of the “jet pressure impulse,” a physical quantity that unifies the velocity and jet shape. However, direct estimation of this parameter from experimental data is challenging due to limitations in spatiotemporal resolution. Therefore, we used numerical simulations to replicate the experimental conditions and calculate the jet pressure impulse. Remarkably, the results show that the jet pressure impulse has peak values, which is consistent with the penetration depth. In addition, there is a correlation between the magnitude of the jet pressure impulse and the penetration depth, highlighting its importance as a key parameter. This study underlines the importance of the jet pressure impulse in controlling the penetration depth of a focused microjet, providing valuable insights for the practical use of needle-free injection techniques.

Https://vestnik.mrsu.ru/index.php/en/articles2-en/123-24-1/1114-10-15507-0236-2910-034-202401-5

Introduction. The article describes the process of considering the geometric parameters of water jet depending on a water jet operation mode and nozzle type. Within the framework of the study of hydraulic soil treatment in the under-tree zones, it became necessary to study the water jet parameters when using different types of nozzles. There was need to determine the geometric parameters of water flow for calculating the cross-sectional area and determining the structural features of the water jet formation. These characteristics are important for a complete description, subsequent study and calculation of water jet action during hydraulic soil treatment; they also allow studying the real shape and structure of the water jet when using different types of nozzles. Aim of the study. The study is aimed at determining the geometric parameters of the water jet for different nozzles including turbo cutters located at different heights. Materials and Methods. To solve this problem, there was developed a test bench, on four pillars, to which the adapter of the supply line of the high-pressure apparatus with replaceable nozzles is fixed. To fix the position and shape of the water jet with a certain frequency, a Basler ace acA1920 camera was used. There was also used a high-pressure apparatus with a maximum pressure of P = 140 MPa, a maximum flow rate of Q = 360 l/h. A standard nozzle with a flat jet, a standard turbo nozzle, and a turbo nozzle of the developed design were used. The geometric parameters of the water jet section were measured from the photographs obtained. Results. From the photos obtained, it can be seen that the rotating water stream entering the turbo nozzle of its own design and the standard turbo nozzle disintegrates from rapid rotation, forming a cone, the cross-sectional area of which is a circle, and affects the soil surface. A flat jet is characterized by a rectangular cross-section. Discussion and Conclusion. According to the results of the study we can draw the following conclusions, the nozzle of the proposed design allows creating water jets of the largest area, which should provide an increase in the working width and, as a consequence, an increase in productivity and quality of soil surface treatment in mainline plantations. This study will also make it possible to analyze the structure of the jet during its operation.

Flow Field Characteristics and Flotation Efficacy in a Pulse Jet Flotation Machine: A Comprehensive Investigation

The design and optimization of flotation machines hold significant importance in enhancing the industrial-grade coal beneficiation process. In this research, the flow field characteristics and flotation performance of a novel pulse jet flotation machine (PJFM) were investigated. The results showed that a PJFM equipped with an innovative pulse cavity can improve the mineralization efficiency of coal due to the coupling of multiple jet shapes. The aeration performance of this PJFM also exceeds the usual desired targets of coal flotation machines, which are characterized by an aeration uniformity coefficient higher than 70% and dominant bubbles of 100~200 μm and 200~300 μm, including a small amount of −100 μm bubbles. The cavitation of the pulse jet achieved the modification of the coal particle surface, and subsequently, the electric potential of the coal largely decreased in absolute value, and the floatability of the coal significantly improved. The concentrate yield of step release flotation increased by 12.42%, while the ash content was only 0.45% higher. Furthermore, in the early stage of flotation, the flotation rate of 0~0.074 mm coal slurry is the fastest and is preferentially floated; in the later stage, the flotation of 0.25–0.5 mm particles dominates. The PJFM demonstrates enhanced particle size selectivity and superior performance in selective flotation.