Interaction Of Jet Research Articles

Helium plasma jet interaction with different target materials and the plasma characteristics on the irradiation area

The experimental study on the dynamic behavior of helium atmospheric pressure plasma jet exposed on the surface of different conductivity is reported in this article. Electrical, optical, and gas dynamics characteristics are monitored using a high voltage probe, current probe, and imaging technique. The turbulence-free plasma jet length is estimated from the image of the plasma jet and correlated with the length estimated through the Electrohydrodynamic number (Ehd number). It has been shown that plasma species strongly modify the gas dynamics on the contact surface. The irradiation area on agar gel, metal, and Teflon is observed and the different flow regimes (free jet, stagnant region, and accelerating region) are identified. The irradiation area is significantly broadened for the polymer-like substrate and intensity is higher close to the stagnant region. The excited nitrogen and OH intensity is higher than the other observed chemical species on the target surface. The turbulence is higher near the outer radius of the irradiated surface, and it increases with operating voltage. The chemistry of the water changes with the presence of the metal probe inside the water.

Effect of the relative arrangement of atomizers on composite liquid fuel spraying characteristics

The paper presents the experimental research findings for the characteristics of promising composite liquid fuel spraying with two atomizers, when varying the scheme of their relative arrangement. The nozzle arrangement was shown to have a significant effect on the spraying characteristics (droplet sizes and velocities), the volume and rate of the combustion chamber filling with aerosol. Following the experimental research, the relative efficiency indicators of spraying water and composite fuels were calculated. The research findings for the spraying of water and composite liquid fuels based on coal and coal processing waste were compared. It was established that in the interaction of sprayed liquid jets, it is possible to control the average size and, thus, number of secondary fragments by intensifying their transformation during coalescence and disruption. A mathematical processing of the experimental results was performed using a set of dimensionless criteria introduced. Schemes were shown that make it possible to provide minimum sizes of slurry droplets and maximum relative efficiency factor of spraying. • One- and two-atomizer spraying characteristics of fuels were compared. • Droplet number, sizes, velocities and trajectories were determined. • Fuel droplet sizes can be changed by the liquid jet interaction with air. • Maximum efficiency factor of fuel spraying was determined. • Spraying schemes for more complete filling of the chamber with fuel aerosol were proposed.

Radio jet–ISM interaction and positive radio-mechanical feedback in Abell 1795

ABSTRACT We present XSHOOTER observations with previous ALMA, MUSE, and HST observations to study the nature of radio jet triggered star formation and the interaction of radio jets with the interstellar medium in the brightest cluster galaxy (BCG) in the Abell 1795 cluster. Using HST UV data, we determined an ongoing star formation rate of 9.3 M⊙ yr−1. The star formation follows the global Kennicutt–Schmidt law; however, it has a low efficiency compared to circumnuclear starbursts in nearby galaxies with an average depletion time of ∼1 Gyr. The star formation and molecular gas are offset by ∼1 kpc indicating that stars have decoupled from the gas. We detected an arc of high linewidth in ionized gas where electron densities are elevated by a factor of ∼4 suggesting a shock front driven by radio jets or peculiar motion of the BCG. An analysis of nebular emission line flux ratios suggests that the gas is predominantly ionized by star formation with a small contribution from shocks. We also calculated the velocity structure function (VSF) of the ionized and molecular gases using velocity maps to characterize turbulent motion in the gas. The ionized gas VSF suggests that the radio jets are driving supersonic turbulence in the gas. Thus radio jets cannot only heat the atmosphere on large scales and may quench star formation on longer time-scales while triggering star formation in positive feedback on short time-scales of a few million years.

Atmospheric Effects of Magnetosheath Jets

We report effects in the upper high-latitude atmosphere related to the interaction of fast magnetosheath plasma streams, so-called jets, with the dayside magnetopause. The jets were observed by THEMIS mission in the dayside magnetosphere during a quiet day on 12 July 2009. It was found that the jet interaction was accompanied by strong localized compression and penetration of suprathermal magnetosheath plasma inside the dayside magnetosphere. The compression caused prominent magnetic variations with amplitudes up to 100 nT observed by ground-based magnetic networks SuperMAG and CARISMA. The magnetic variations were also visible in the geomagnetic Dst and AE indices. The jets also resulted in intense precipitation of the suprathermal ions with energies < 10 keV and energetic electrons with energies > 30 keV observed by low-altitude NOAA/POES satellites in a wide longitudinal range. The precipitations produced enhancements of ionization with an amplitude of ~1 TECU (~30% in relative units) and intensification of the ionospheric E and F1 layers as observed in the FORMOSAT-3/COSMIC misson. The enhanced ionization in the upper atmosphere might affect radio communication and navigation in the high-latitude regions. These results also provide new insight into the contribution of magnetospheric forcing to day-to-day ionospheric variability.

Mesh Adaptation for Simulating Lateral Jet Interaction Flow

Under the condition of supersonic incoming flow, a missile lateral jet flow field has complex flow structures, such as a strong shock wave, an unsteady vortex and flow separation. In order to improve ability to capture complex flow structures in numerical simulation of lateral jets, this paper proposes a combined-grid adaptive method. When combined with finite volume approximation of second-order and h-type adaptive technology, our method was verified by numerical experiments, which shows that wave structure and vortex structure in the jet flow field can be effectively captured at the same time. In comparison of uniformly refined mesh results, it was found that accuracy of computed results and resolution of characteristic flow structures were significantly improved after mesh adaptation. In comparison of the pressure coefficient, it was found that the error between the adaptive mesh and the uniformly refined mesh was smaller, and the maximum errors of the base grid, adaptive grid and uniformly refined grid were 92.1% and 12.3%.

Research on RCS Jet Interaction Characteristics of the Capsule Entry Vehicle at Subsonic and Transonic Speed

In this paper, the RCS jet interaction characteristics of the capsule entry vehicle were studied by numerical simulation. The jet interference characteristics under different re-entry ballistic parameters were compared. The influence of the angle of attack on the jet flow field structure and aerodynamic characteristics was analyzed.

Numerical Simulation of Jet Interaction Flow Field with Different Flow Rates

In this paper, the complex disturbance flow caused by the interaction of jets with different flow rates and hypersonic incoming flow on a cone-cylinder-skirt of revolution is numerically studied, the typical shock wave structure and the influence range caused by the jet interaction are given, and the effect of the jet flow rate on the interaction flow field is discussed. The results show that the interaction between the jet flow and the incoming flow increases with the rise of the jet flow rate, and the influence range of the wrapping effect enlarges. If the jet flow rate is equivalent to the incoming flow rate, the leading edge separation line forms a closed loop.

Effect of voltage pulse duration on electrophysical and thermal characteristics of cold atmospheric plasma jet

The desirable properties of a cold atmospheric plasma jet (CAPJ) for medical applications are high efficiency of the treatment and low thermal effects. To meet these requirements, we propose to use the CAPJ generated with the positive pulsed (PP) voltage. In our experiments and fluid model simulations, it is shown that a change of the pulse duration allows us to control precisely the intensity of interaction of the plasma jet with the target and the heating of the contact zone. The helium CAPJ is formed with 13–30 kHz PP voltage frequencies with the pulse duration of 7–20 µs. The enhancement of plasma-target interaction is analyzed with the measured discharge current and calculated ionization rate near the target surface. The temperature measurements in the plasma-target active zone show that the heating by CAPJ excited with the PP voltage is generally less than in the case of AC voltage. The efficacy of treatment is tested on A549 cancer cells exposed to CAPJ ignited with the positively pulsed voltage with different pulse duration and with AC voltage.

Physicochemical Description and Mathematical Model of the Oxygen Flame Formation during the Interaction of an Oxygen Jet with the Converter Atmosphere

Physicochemical Description and Mathematical Model of the Oxygen Flame Formation during the Interaction of an Oxygen Jet with the Converter Atmosphere

Experimental study on the transmission characteristics of near-field detonation noise into water

To study the transmission characteristics of near-field detonation noise into water, the detonation noise transmission system is built on a laboratory-scale water tank using a detonation tube with a diameter of 30 mm. The interaction of the detonation gas jet with the air–water interface, the development of the cavity, and the growth of the liquid column are experimentally observed by a high-speed camera. The spectral distribution characteristics of detonation noise above and below the interface are recorded by a microphone, a hydrophone, and an underwater blast sensor. Analysis of the experimental images shows that the size of the cavity increases with increasing filling pressure and decreases with increasing nozzle height. By normalizing the evolution time of the cavity with the cavity lifetime, it is concluded that the time for the cavity to develop to the deepest is about 0.27, independent of the filling pressure. The pressure field data analysis results show that the main frequencies of the detonation sound waves are 100 and 400 Hz, and the frequency distribution has nothing to do with the filling pressure. Through the defined acoustic wave energy transmission coefficient, it is demonstrated that the detonation acoustic wave transmission coefficient decreases with the increase in the frequency, and the shock wave transmission coefficient decreases with the increase in the angle.

Experimental and Numerical Investigations on the Mixing Process of Supercritical Jet Injected into a Supersonic Crossflow

The mixing process and distribution characteristics of a supercritical endothermic hydrocarbon fuel (EHF) jet injected into a supersonic crossflow were investigated by experimental and numerical methods, respectively. The schlieren system and acetone planar laser-induced fluorescence (PLIF) optical system were used to capture the flow-field structural characteristics and instantaneous plume. The mixture and real gas models were employed to calculate the interaction of a transverse jet and supersonic crossflow and reveal a good accuracy with the experimental results. The mixing efficiency and total pressure loss were analyzed based on the numerical results. The results indicate that the supercritical-state EHF directly changes to a gaseous state as it enters the supersonic crossflow from the injector. The EHF jet plume boundary increases with the increasing momentum flux ratio (q). As the streamwise and spanwise distance increases, the traverse heights and expand width increase, and the EHF jet plume presents a semicircle shape in the cross-sectional plane. With the increase in the traverse direction, the concentration distribution shows a fast and then slow power exponential decreasing law; the highest concentration point starts from the near-wall region and rises in the transverse direction with the flow distance increasing. For the same injection condition, the higher the inflow Mach number, the higher the mixing efficiency. For the same Ma, the mixing efficiency is better for the case with low injection pressure and high injection temperature. The total pressure loss is greater in the higher Ma, and high injection pressure conditions cause greater total pressure loss.

A compact symmetric ejection from the low mass AGN in the LINER galaxy NGC 4293

ABSTRACT We conducted a Very Long Baseline Array (VLBA) observation of the low mass active galactic nucleus (AGN) in galaxy NGC 4293 (z = 0.003). The object is associated with a low-ionization nuclear emission-line region (LINER). Its black hole mass is estimated as ∼105 or ${\sim}10^7 \, \mathrm{M}_\odot$. The VLBA 1.5 GHz image shows an inverse symmetric structure with two discrete radio blobs separated by an angular distance of ∼120 mas, corresponding to ∼7 parsec. Furthermore, its integrated radio spectrum has a turnover at the frequency of ∼0.44 GHz. Based on the compactness and spectrum, the nuclear radio source in NGC 4293 belongs to a sample of (megahertz) peaked spectrum (PS/MPS) radio sources with compact symmetric morphologies. NGC 4293 has 1.4 GHz radio power of only ${\sim}10^{20}\, \mathrm{W\, Hz^{-1}}$ with the VLBA observation, which is consistent with local AGNs but lower than the current PS samples. One of the two blobs has a steep radio spectrum α = −0.62 ± 0.08 (Sν ∝ ν+α), while the other one has an inverted spectrum α = 0.32 ± 0.10. The VLBA 1.5 GHz luminosity ratio of the two blobs is 3.23 and both blobs show lateral-flowing structures where the hotspots reside at the edge of each radio lobe. This can be explained as jet interactions with dense circumnuclear medium. We estimate the black hole mass of NGC 4293 through the Fundamental Plane of black hole activity, which constrains the black hole mass to be ${\lesssim}10^6\, \mathrm{M}_\odot$. It supports that the object is a low-mass AGN and a potential candidate for accreting and ejecting IMBHs.

RAD@home citizen science discovery of an active galactic nucleus spewing a large unipolar radio bubble on to its merging companion galaxy

ABSTRACT Active galactic nucleus (AGN) feedback during galaxy merger has been the most favoured model to explain black hole–galaxy co-evolution. However, how the AGN-driven jet/wind/radiation is coupled with the gas of the merging galaxies, which leads to positive feedback, momentarily enhanced star formation, and subsequently negative feedback, a decline in star formation, is poorly understood. Only a few cases are known where the jet and companion galaxy interaction leads to minor off-axis distortions in the jets and enhanced star formation in the gas-rich minor companions. Here, we briefly report one extraordinary case, RAD12, discovered by RAD@home citizen science collaboratory, where for the first time a radio jet–driven bubble (∼ 137 kpc) is showing a symmetric reflection after hitting the incoming galaxy which is not a gas-rich minor but a gas-poor early-type galaxy in a major merger. Surprisingly, neither positive feedback nor any radio lobe on the counter jet side, if any, is detected. It is puzzling if RAD12 is a genuine one-sided jet or a case of radio lobe trapped, compressed and re-accelerated by shocks during the merger. This is the first imaging study of RAD12 presenting follow-up with the Giant Metrewave Radio Telescope, archival MeerKAT radio data and Canada-France-Hawaii Telescope optical data.

Shelfbreak processes affecting acoustic propagation in a changing ocean

Fundamental physical oceanographic processes affecting sound speed fields and acoustic propagation have been studied in shelfbreak regions for some time. Integrated observations extending back to the 1990s have related acoustic propagation variability to basic thermohaline structure as well as physical oceanographic processes causing significant variability in sound speed fields. Key shelfbreak processes such as frontal wave propagation, eddy-Shelfbreak Jet interactions, and wind-driven motions will be described. The influence of ocean warming and climate change impacts on these processes will be outlined with emphasis on the Middle Atlantic Bight in the northeastern United States. The impacts of changes in both the atmospheric Jet Stream as well as the Gulf Stream on the Shelfbreak Front and Jet and implications for acoustic propagation will be presented.

Atmosphere homogenization induced by vertical jets in large enclosures

To theoretically investigate atmosphere mixing in an enclosure, three experiments of interaction of a vertical air jet with a helium-rich layer performed in SPARC, PANDA and MiniPanda experimental facilities, were simulated using the URANS approach. For the purposes of this work, firstly, a local Froude number is introduced, which can be directly used in computational fluid dynamics calculations to specify the regions with possible occurrence of Kelvin-Helmholtz instability. Namely, it is shown that in these regions, turbulent diffusion is underpredicted and turbulence model fails to replicate some phenomena. Secondly, a model for dynamically prescribe turbulent Schmidt and Prandtl numbers is proposed. The proposed model improves the results in isothermal case with possible occurrence of Kelvin-Helmholtz instability, while its effects are negligible in cases with higher temperature jets with lower local Froude number values, where the conditions for the Kelvin-Helmholtz instability are not established.

Precision Ventilation for an Open-Plan Office: A Study of Variable Jet Interaction between Two Active Chilled Beams

Precision ventilation is developed to achieve thermal comfort for occupants in an office by creating micro-climate zones. The present study aims to achieve individual thermal comfort for occupants with different metabolic rates by using higher airspeeds for enhancing heat transfer. The variable jet interaction between two ACBs with JetCone adjustments cause higher velocity jets to reach different regions of the occupied zone. The colliding jets from the center of a thermal isolated room were moved towards different zones in an office configuration with a constant room temperature of 23 °C. This study was conducted for five different cases in a room divided into four zones according to occupants’ metabolic rates. The experimental and CFD results show that occupants facing symmetrical airflow distribution and with a constant 1.2 metabolic rate (Case 1) had a similar predicted mean vote (PMV) index. The zones with higher-metabolic-rate occupants, i.e., 1.4 met and 1.6 met in cases 2 and 3 were exposed to air velocities up to 0.4 and 0.5 m/s, respectively. In case 4, the air velocity in the single zone with 1.6 met occupants was raised to 0.6 m/s by targeted airflow distribution achieved by adjusting JetCones. These occupants with higher metabolic rates were kept thermally neutral, in the −0.5 to +0.5 PMV range, by pushing the high velocity colliding jets from the center towards them. In case 5, the results showed that precision ventilation can maintain the individual thermal comfort of up to three different zones (in the same office space) by exposing the occupants with metabolic rates of 1.2, 1.4, and 1.6 met to airspeeds of 0.15, 0.45, and 0.55 m/s, respectively.

Multiphase CFD Modeling and Experimental Validation of Polymer and Attenuating Air Jet Interactions in Nonwoven Annular Melt Blowing.

In annular melt blowing, fiber formation is achieved by accelerating a molten polymer via drag forces imparted by high velocity air that attenuates the polymer jet diameter. The interactions at the polymer-air interface, which govern the motion of the jets and impact the resulting fiber characteristics, are important but not well understood yet. This work details the development and validation of a multiphase computational fluid dynamics (CFD) model to investigate these interactions and the effects of three key melt blowing process parameters (polymer viscosity and throughput, and air velocity) on two critical fiber attributes - whipping instability and fiber diameter. Simulation results highlighted that whipping instability was driven by the polymer-air velocity differential, and the fiber diameter was primarily modulated by polymer throughput and air velocity. The CFD model was validated by modulating the polymer and air throughputs and analyzing the fiber diameter experimentally. Empirical results showed good agreement between fabricated and model-estimated fiber diameters, especially at lower air velocities. An additional CFD simulation performed using a melt blowing nozzle geometry and process parameters described in literature also confirmed good correlation between model estimates and literature empirical data.

Unsteady Turbulent Swirling Flows in a Thick Torus

Experimental study of unsteady swirling flows generated by special diverters in closed toroidal channels with different curvatures was carried out. The formation of a swirling flow in a toroidal channel is crucially different from the case of a straight cylindrical channel. It essentially depends on the curvature and is hindered by its increasing. The complex dynamics of swirling flow tightly connects with the interaction of jets after the diverter. Measurements of flow velocity using tracer’s tracks showed that the evolution of the toroidal component in torus with one diverter can be divided into two-time intervals with different power laws. The evolution of the poloidal component is rather characterized by one slope “-2/3”.

Turbulence characteristics of the flow resulting from the hydrodynamic interaction of multiple counter flow jets in expanding channels

Turbulence characteristics of the flow resulting from the hydrodynamic interaction of multiple counter flow jets in expanding channels

Numerical study on mean flow characteristics for a combined turbulent wall and offset jets with a parallel co-flow

Combined turbulent wall and offset jets with and without the presence of a parallel co-flow stream are investigated using the k-ω turbulence model. We focus on the effects of co-flow velocity on the locations of various characteristic points formed owing to the interaction of wall and offset jets in the dual jet flow. The inlet Reynolds number is taken as 15,000 and the offset ratio is varied from 5 to 11. At low offset ratios, the co-flow velocity effect remains almost negligible. With the progressive increase in co-flow velocity, the characteristic points are gradually relocated towards the further downstream direction with a transverse movement away from the bottom wall whose effect is weakened with the increase in co-flow velocity. Furthermore, regression analysis shows power law and linear correlations of the longitudinal and transverse coordinates of characteristic points with the co-flow velocity and the offset ratio.