Intense Jet Research Articles

Numerical investigation of the effect of tracheostomy on flow and particle transport characteristics in human airways

Tracheostomy is a typical surgical procedure that has been widely practiced to address airway-related difficulties, such as airway obstruction or chronic conditions, that require long-term supportive ventilation. However, it may result in symptoms that detrimental to respiratory system. Computational fluid dynamics (CFD) is a noninvasive and efficient approach for observing the effects of tracheostomy. In this study, we introduced a CFD framework that can reveal the effects of tracheostomy tube insertion based on a comparison with the airflow of a normal airways. An automatic transformation method was developed using a patient's anatomical information to combine subject-specific airways with an artificial tracheostomy tube geometry and an idealized upper airway geometry for later comparison of characteristics of airflow and particle transport. The CFD scheme used for flow simulation in lungs was employed to achieve the behaviors of airflow. The tracheostomy tube generates a jet flow, resulting in twice greater wall shear stress (WSS) and 30 times greater viscous dissipation in the trachea compared to normal airway. The tracheostomized airway induces an intense turbulent jet, which enhances chaotic motion of the particles therein and allows particles to deposit more frequently on the surface. Subsequently, an increase in particle deposition is observed on the central airway's surface. The variation of pressure between inspiration and expiration phase was twice greater and the airflow resistance was also significantly higher compared to normal airway, implying the greater work of breathing. The novel framework could evaluate the efficiency and potential complications in performing tracheostomy beforehand by observing airflow behaviors.

Сontinuous walking beam furnace without water cooling for reheating copper alloy blanks

It takes a special technique to heat up round blanks cast of copper alloys in conformance with applicable process specification, which implies maintaining a low oxidizing atmosphere in a gas furnace. This paper describes a continuous furnace with walking beams that are not watercooled designed to heat up round blanks to the maximum temperature of 1,000 ºC. The furnace, which stands before the pipe press for making pipes of different sizes, is fueled by natural gas burned in high-speed burners with the air flow rate of α = 0.98 in hot zones and that of α = 1.05–1.1 in preheating zones. The side walls of the furnace are equipped with high-speed burners which serve to intensify the convective heat transfer inside the furnace. The burners ensure a transverse/countercurrent flow of gases with an intense transverse jet circulation. The furnace is equipped with a panel roof lined with ribbed ceramic fiber blocks (original design by UralTermoKompleks) which serves to intensify the radiation heat transfer without raising the temperature. A larger interior surface of the furnace roof leads to an increased radiation heat flow density and hence higher heating rates. It means that the furnace has better performance at the same temperature. The furnace is equipped with charging and discharging systems. An eccentric is responsible for moving the walking beams. An integrated control system controls heat in each of the five zones of the furnace guided by thermocouples and charging and discharging modes. The furnace has been fully commissioned.

Inter‐Model Spread of the Simulated Winter Surface Air Temperature Over the Eurasian Continent and the Physical Linkage to the Jet Streams From the CMIP6 Models

AbstractThe model uncertainty, one of the major sources of projection uncertainty, is still a challenge in the climate simulation. In this study, we investigated the inter‐model spread of the simulated winter surface air temperature (SAT) over the Eurasian continent and the physical link to the upper‐level jet streams from the Coupled Model Inter‐comparison Project Phase 6 models. Extracted by the inter‐model empirical orthogonal function analysis, the leading inter‐model spread of SAT over the Eurasian continent is characterized by a cold pattern, particularly over high latitudes, which is closely associated with the out‐of‐phase variation in the intensity of the East Asian polar front jet (EAPJ) and East Asian subtropical jet (EASJ). The weakened‐EAPJ‐enhanced‐EASJ pattern is linked to the intensified Siberian high, the strengthened Aleutian low, and the deepened East Asian trough. All the variations would benefit the cold air invasion, resulting in the leading inter‐model spread of the SAT. The possible mechanism for the inter‐model uncertainty in the out‐of‐phase variation in the intensity of the two jets would be traced to the cooling over the Northwest Pacific oceans, which has reduced (enhanced) the meridional temperature gradient over high (low) latitudes and thereby contributed to the out of phase variation in the two jets. Our findings would help provide a potential metric for understanding the winter SAT change over the Eurasian continent.

Cavitation over solid surfaces: microbubble collapse, shock waves, and elastic response

We discuss the interaction of the strongly nonlinear fluid motion induced by the collapse of a vapor microbubble over a planar surface and the elastic dynamics of the underlying solid. The fluid is described using an extension of the Navier-Stokes equations endowed with distributed capillary stresses in the context of a diffuse interface approach. The collapse of the bubble is triggered by overpressure in the liquid and leads to an intense jet that pierces the bubble, changing the bubble topology from spheroidal to toroidal, and impinges the solid wall inducing an intense and strongly localized load. Moreover, at bubble collapse, a compression wave is launched into the liquid surrounding the bubble. By propagating along the solid surface, the compression wave combined with the liquid jet excites the dynamics of the elastic solid, producing a complex system of waves, including, longitudinal, transversal, and Rayleigh waves, propagating in the solid. It is conjectured that the intense deformation of the solid induced by the strongly localized liquid jet may lead to the plastic deformation of the solid producing the surface pitting observed in many applications subject to cavitation-induced material damage.

Steerable photonic jet for super-resolution microscopy

A promising technique in optical super-resolution microscopy is the illumination of the sample by a highly localized beam, a photonic jet (also called photonic nanojet). We propose a method of computation of incident field amplitude and phase profiles that produce photonic jets at desired locations in the near field after interaction with a fixed micro-scale dielectric lens. We also describe a practical way of obtaining the incident field profiles using spatial light modulators. We expect our photonic jet design method to work for a wide range of lens shapes, and we demonstrate its application numerically using two-dimensional micro-lenses of circular and square cross-sections. We furthermore offer a theoretical analysis of the resolution of photonic jet design, predicting among other that a larger lens can produce a narrower photonic jet. Finally, we give both theoretical and numerical evidence that the waist width of the achieved designed jets is increasing linearly and slowly over a large interval of radial distances. With uniform plane wave illumination, the circular two-dimensional micro-lens produces a similar-sized jet at a fixed radial distance, while the square lens does not form a jet at all. We expect our steerable optical photonic jet probe to enable highly localized adaptive real-time measurements and drive advances in super-resolution optical microscopy and scatterometry, as well as fluorescence and Raman microscopy. Our relatively weak peak jet intensity allows application in biology and health sciences, which require high resolution imaging without damaging the sample bio-molecules.

Study on Penetration Mechanism of Shaped-Charge Jet under Dynamic Conditions.

Aiming at the dynamic penetration process of a shaped-charge jet, we proposed a mathematical model for the penetration of a jet under dynamical conditions based on the theory of virtual origin and the Bernoulli equation taking into account the jet and target intensities. The dynamic penetration process of the jet was divided according to the penetration channel of the jet into the static target. The dynamic penetration model of the jet based on the unperturbed section and perturbed section was established. The penetration depth variation in the shaped-charge jet vertically penetrating target plates with different moving speeds (150~400 m/s) was analyzed by finite element software. The dynamic penetration model shows that with the increase in the target moving speed, the disturbed time of the jet continuously advances, and the dynamic penetration depth continuously decreases; as the velocity of the target increases, the penetration length of the unperturbed jet decreases and then becomes stable, while the penetration length of the perturbed jet decreases. The results showed that the mathematical model is consistent with the finite element simulation, and that the mathematical model can effectively characterize the penetration depth of the unperturbed and disturbed jet portions, adequately explain the dynamic response behavior of the jet penetrating a moving target, and effectively predict the dynamic penetration depth of the jet under the influence of the target movement.

Torpedo pile penetration by combined water jet and mechanical vibrations in cohesive sedimentary beds

The penetration efficiency and safety of piles on the seabed affect the cost of offshore structures and the reliability of relevant equipment, which entails to the success or failure of the development and utilization of ocean resources. However, the traditional methods of pile penetration, including pressing method, impact driving method and vibro-driving method, are difficult to adapt to the complex marine environment. In this study, the torpedo pile penetration in cohesive sedimentary bed was investigated by applying downwardly directed vertical water jet and mechanical vibrations. The experimental work was developed in the laboratory through a series of pile penetration tests in different types of cohesive sediments. During the penetration processes of the torpedo pile, the relevant influencing factors such as water content of cohesive sediment, vibration intensity and water jet velocity were considered. The experimental results show that the penetration depth of the torpedo pile increases with the increase of water jet velocity, vibration intensity and water content of cohesive sediment. Based on the dimensionless analysis and data regression, a formula for the critical penetration depth of the torpedo pile in cohesive sediment is proposed, which is correlated with the water jet velocity and vibration intensity, as well as the torpedo pile and soil properties. In addition, the formula is verified by the experimental data of other study, which presents good consistency.

Application of the Local Estimation Methods to Calculate the Radiant Intensity of a High-Temperature Jet

Application of the Local Estimation Methods to Calculate the Radiant Intensity of a High-Temperature Jet

Associated Summer Rainfall Changes over the Three Rivers Source Region in China with the East Asian Westerly Jet from 1979 to 2015

Abstract Under the intensification of global warming, the characteristics of the Three Rivers source region (TRSR; i.e., headwaters of the Yellow River, the Yangtze River, and the Lancang River) in China were diagnosed in the summer season from 1979 to 2015 using observations and reanalysis data. The diagnoses indicate that summer precipitation decreased from 1979 to 2002 [by 9.01 mm day−1 (10 yr)−1; p < 0.05 by Student’s t test] and increased significantly after 2002 [by 5.52 mm day−1 (10 yr)−1]. This abrupt change year (2002) was further confirmed by the cumulative anomaly method, the moving t-test method, and the Yamamoto method. By compositing the thermodynamics before and after the abrupt change year (2002), the results reveal that increased water vapor and more substantial lower-level convergence were present over the TRSR during 2003–15. This marked interdecadal variability in the TRSR summer precipitation responded to the interdecadal position and intensity of the large-scale forcing East Asian westerly jet (EAWJ), which is significantly modulated by the low-frequency variability associated with Southern Oscillation index. The connection between the interannual TRSR precipitation and the location and intensity of EAWJ was also explored. The position index of the EAWJ is negatively (with correlation coefficient R of −0.446; p < 0.05 by Student’s t test) correlated with the precipitation over the TRSR, implying that southward and northward years of EAWJ are respectively associated with intensifying and weakening the TRSR summer precipitation, whereas the intensity of EAWJ is insignificantly correlated with the TRSR summer precipitation.

Numerical simulation of early stages of scour around a submarine pipeline using a two-phase flow model

Current-induced scour around a submarine pipeline during onset and tunnel erosion are investigated in both clear-water and live-bed regimes using an Eulerian–Eulerian two-phase model for sediment transport. The Hybrid Fictitious Domain-Immersed Boundary (HFD-IB) method is adopted to simulate the pipeline structure. The model is validated against two published experimental data: (1) flow past a pipeline near a rigid bed and (2) scour around a pipeline over a sand-bed, showing favorable results for the flow and scour patterns around the pipe. The driving mechanisms of the onset and tunnel erosion are investigated by examining the detailed fluid–sediment interactions around the pipe in both regimes. The driving mechanisms for the onset and tunnel erosion are found similar in both regimes, except their time and magnitude scales. The onset is triggered by the piping mechanism induced by the upstream–downstream pressure gradient beneath the pipe. Meanwhile, the jet flow is the driving mechanism for the tunnel erosion. The simulated live-bed condition shows a higher upstream–downstream pressure gradient beneath the pipe, faster piping mechanism, more intense jet flow velocity and sediment flux compared to the clear-water condition. The model well capture these underlying mechanisms, suggesting its promising capability as a predictive tool for scouring.

Design and performance of a small-scale acoustic wind tunnel at Wenzhou University for aerodynamic noise studies

A small-scale acoustic wind tunnel has been newly built at Wenzhou University to study the aerodynamic noise generation and suppression for various bodies immersed in a fluid flow, especially for the airfoil and low-speed axial fans. The design principle, the overall layout, and key components of the wind tunnel are presented in this paper. This open-circuit and suction-type wind tunnel has an open-jet test section of 0.5 m × 0.4 m and can achieve a maximum wind speed of 60 m/s, corresponding to the Reynolds number of 1.8 × 106 based on the hydraulic diameter of the tunnel. The acoustic characteristics of the wind tunnel have shown a satisfactory result of low background noise levels comparable to other university wind tunnels worldwide. The turbulence intensity of the free jet in the potential core is measured between 0.15 and 0.22 %. Aeroacoustic measurements have been finally performed on a few benchmark models, including a rectangular cavity, a flat plate with blunt/sharp trailing edges, a tandem rod-airfoil, and a circular rod. The noise levels of all test models at the frequencies of interest are far in excess of the free-jet background noise, making the wind tunnel well suitable for aerodynamic noise studies.

Effect of low-pressure environment on thermal runaway behavior of NCM523/graphite pouch cells with different overcharge cycles

In the aviation field, the development and application of electric aircraft powered by lithium-ion batteries (LIBs) have received extensive attention. However, abuse due to overcharge poses a significant obstacle to its safe application. In this work, to investigate the thermal runaway (TR) behavior of overcharged LIBs in low-pressure flight environment, the TR characteristics of NCM523/graphite pouch cells with different overcharge cycles at 30 kPa are studied. The results suggest that the increase of overcharge cycles leads to a decrease of thermal stability, and an increase of TR intensity and heat release of the LIBs. In addition, the TR jet intensity at 30 kPa is significantly stronger than that of 95 kPa due to the larger differential pressure for the release of combustibles. The TR intensity and heat release at 30 kPa are significantly weaker than that of 95 kPa due to the lower oxygen content for burning. The electrochemical analysis and the disassembly photos confirm the destruction of electrode structure and the deposition of lithium. The X-ray computed tomography images and X-ray diffraction patterns suggest that the side reactions in the inner layer of the cell are more obvious than the outer layer, and the internal deformation expands from the inside out.

Aeroacoustics of Twin Rectangular Jets Including Screech: Large-Eddy Simulations with Experimental Validation

High-fidelity large-eddy simulations (LESs) are performed to investigate aeroacoustic characteristics of jets issuing from twin rectangular nozzles with an aspect ratio of 2:1 at two overexpanded conditions and the design condition. For all three jet conditions simulated, LES predicts qualitatively similar near-field flow statistics to those measured at the University of Cincinnati. Using the Ffowcs Williams-Hawkings method, LES captures the fundamental screech tone and its harmonics fairly well at multiple observer locations in the far-field. Intense jet flapping motions in the near field along the minor axis, which are influenced by jet-to-jet interactions, are found to correspond to those frequencies. Moreover, the predicted overall sound pressure levels are within 1–2 dB of the experimental measurements. However, the screech tones appear to be intermittent, as the twin-jet interaction pattern varies irregularly. To extract dominant flow structures at the screech frequencies and identify the twin-jet coupling modes, spectral proper orthogonal decomposition (SPOD) analysis is used. SPOD analysis recovers energetic peaks at the screech frequencies, and the corresponding leading modes indicate strong upstream radiation originating from the fifth/sixth shock cells. For the two overexpanded conditions, the leading modes show antisymmetric coupling in the minor axis at the fundamental screech frequencies. In contrast, the two jets behave symmetrically with respect to each other in the major axis, in line with the absence of jet flapping in this direction. Furthermore, the leading SPOD eigenvalues turn out to be, at least, two orders of magnitude larger than higher-order eigenvalues, suggesting potential of reduced-order models for the twin-jet screech.

Analysis of Upper Airway Flow Dynamics in Robin Sequence Infants Using 4-D Computed Tomography and Computational Fluid Dynamics.

Robin Sequence (RS) is a potentially fatal craniofacial condition characterized by undersized jaw, posteriorly displaced tongue, and resultant upper airway obstruction (UAO). Accurate assessment of UAO severity is crucial for management and diagnosis of RS, yet current evaluation modalities have significant limitations and no quantitative measures of airway resistance exist. In this study, we combine 4-dimensional computed tomography and computational fluid dynamics (CFD) to assess, for the first time, UAO severity using fluid dynamic metrics in RS patients. Dramatic intrapopulation differences are found, with the ratio between most and least severe patients in breathing resistance, energy loss, and peak velocity equal to 40:1, 20:1, and 6:1, respectively. Analysis of local airflow dynamics characterized patients as presenting with primary obstructions either at the location of the tongue base, or at the larynx, with tongue base obstructions resulting in a more energetic stenotic jet and greater breathing resistance. Finally, CFD-derived flow metrics are found to correlate with the level of clinical respiratory support. Our results highlight the large intrapopulation variability, both in quantitative metrics of UAO severity (resistance, energy loss, velocity) and in the location and intensity of stenotic jets for RS patients. These results suggest that computed airflow metrics may significantly improve our understanding of UAO and its management in RS.

Electrical explosion in confined space: From warm dense matter to fragmentation

The physical image of the confined electrical explosion in the source region is depicted. Metallic plasma/vapor dynamics and its fragmentation effect (on a confining structure) under μs-timescale are diagnosed via high-speed photography, electrophysical, and spectral measurements. When adding a 1-mm-thick Teflon tube outside the exploding wire, the growth of spatial heterogeneity via electro-thermal instability is largely compressed, and the deposited energy almost doubled from about 85 to 150 J. During the short period after breakdown, considerable energy depositing into the confined space, e.g., 100 J for 0.1 cm3, drives the fast inflation and burst of the 0.5 g confining tube to ∼500 m/s (kinetic energy of ∼62.5 J). Intense plasma jet eruption with a supersonic speed >1.5 km/s and induced shock waves of 2–3 km/s are observed from cracks of the inflated tube. In addition, the erupted plasma jets gradually evolve Rayleigh–Taylor instability and finally cause turbulent mixing with the ambient medium. This mechanism is very likely to explain the plasma cavity evolution in underwater explosion. Interestingly, although the confining effect of water is stronger than a Teflon tube, the latter has a better response to the high-rate impulse loading and absorbs more deposited energy by deformation, phase transition, and acceleration.

Substantiation of dth air drill hammer parameters for penetration rate adjustment using air flow

One of the critical process flows in open pit mining is blasthole drilling using self-propelling equipment. Roller-bit drilling rigs enjoy wide application in surface mining. It is of the current concern to increase penetration rate of drilling with such drilling rigs, especially in structurally complex rock mass. The most effective tool to this end is a DTH air drill hammer which allows adjustability of penetration rate, reduction in probability of roller-bit jamming and intensification of removal of chippings. The authors review alternative modifications of roller-bit drilling rigs with intensification of rotary drilling by means of applying impact loads to roller bit. The theoretical research determines the ultimate impact force of a DTH air drill hammer such that the penetration rate of rotary drilling increases at the preserved durability of roller bit. The re-designed air drill hammer with adjustable air damper enables optimized treatment of well bottom by roller bit owing to variation in the compressed air jet intensity and in the tool impact energy. It is expected to manufacture and test a pilot DTH air drill hammer for roller-bit drilling rigs in an open pit mine in the northwest of the country. The experimental research of penetration rate versus impact load proves feasibility of a substantial increase in the penetration rate with the increasing energy of impact generated by DTH air drill hammers. It is required to take into account an essential decrease in the roller bit durability as function of the impact energy in this case. It seems to be important to obtain experimental relationships or families of graphs of roller bit durability and impact energy at different characteristics of rocks and using the three-mass piston–pin–tool system. Wide introduction of drilling rigs SBSH-250 equipped with DTH air drill hammers with adjustable air dampers can essentially increase drilling performance and decrease drilling cost.

Engineering application of submerged water jets for sediment removal in a tidal riverbed

Sediment deposition problems have attracted the interest of engineers and researchers. Several experimental studies have been conducted on scour depth using turbulent jets. However, field observation and monitoring have rarely been reported. This study aimed to eliminate sediments on a tidal riverbed using a prototype device, which consisted of a set of submerged vertical water nozzles and submerged horizontal air nozzles. The effectiveness of the water jet in sediment removal during spring and neap tides was evaluated. The quantitative relationships of dimensionless parameters, such as (1) the relative sediment scour volume versus the number of flows from the jet exit, (2) the relative sediment scour volume versus the relative scour depth, and (3) the relative scour size versus the relative jet intensity, were analyzed. The results showed that the freshwater flowing to the sea affected the sediment scour volume during the falling cycle of spring tides. In contrast, the rising cycle of spring tides retarded the freshwater flow, resulting in a decrease in the sediment scour volume. A steep water surface slope accelerated the river flow and further influenced the cross-flow current around the study area. As a result, a highly diffusive turbulent flow was produced, causing suspended sediments to be rapidly removed from the scour hole center. An increase in the number of flows from the jets led to intensified diffusion of turbulent energy into the flow. The rapidly varying water depth caused jet energy to be dissipated before approaching the riverbed, and it significantly affected the scour process during the spring-tide period. The proposed equations can be used to estimate the scour volume, scour size, and re-suspended sediments in tidal rivers within defined ranges of parameters.

Impact of interannual variation of the spring Somali Jet intensity on the northwest–southeast movement of the South Asian High in the following summer

Impact of interannual variation of the spring Somali Jet intensity on the northwest–southeast movement of the South Asian High in the following summer

Effect of external E × E and E × B configurations on an atmospheric-pressure plasma jet and plasma-activated water: Experiments and simulations

The potential of atmospheric-pressure plasma-treated water in biomedical-related applications has gradually increased recently. This contribution aims to explore the effects of externally applied E × E and E × B configurations on plasma jets and plasma-activated water. Although plasma plume deflection occurs in both external electric and magnetic configurations, the crossed electric field causes the radial separation of electrons and positive ions to weaken the plasma jet–liquid interaction, while E × B drift enhances the ionization collisions and discharge intensity of plasma jets. The concentration of aqueous reactive species (O2−, OH, and H2O2) and the inactivation effectiveness of living tissues (tumor cells and Escherichia coli) are weakened in the case of applying an external E × E configuration but strengthened with increasing transverse magnetic field. These findings prove that an external E × B configuration is a promising method for improving the performance of plasma jets in biomedical applications.

Polymer materials used to reduce waterjet wear of pump parts

The article presents the results of studies of the degree of influence of the operating mode of the centrifugal pump on the intensity of the water jet at constant values of the sediment concentration P = 20 kg/ m3, particle diameter d = 0.25…0.5 mm, test duration T = 2 hours and shaft speed n0 = 2900 rpm. Experiments were carried out on pump feeds from 0.5 Qopt to 1.25 Qopt with various materials and polymer coatings that were applied to the surfaces of the blades made of St.3. The best adhesion of the polymer coating is obtained at a metal temperature of 21°C. Polymer materials based on epoxy resin with silicon carbide have the highest wear resistance, while silumin shows low wear resistance. When testing ground pumps, it was found that parts made of electro corundum on an epoxy-phenol-formaldehyde bond, in comparison with parts made of wear-resistant cast iron, increases the service life of pumps 3 - 8 times.