Morphology Of Jets 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.

A Simulation Study of Low-power Relativistic Jets: Flow Dynamics and Radio Morphology of FR-I Jets

Radio galaxies are classified into two primary categories based on their morphology: center-brightened FR-I and edge-brightened FR-II. It is believed that the jet power and interactions with the ambient medium govern the deceleration and decollimation of the jet-spine flows, which, in turn, influence this dichotomy. Using high-resolution, three-dimensional relativistic hydrodynamic simulations, we follow the development of flow structures on sub-kiloparsec to kiloparsec scales in kinetically dominant low-power relativistic jets. We find that the bulk Lorentz factor of the jet spine and the advance speed of the jet head, which depend on the energy injection flux and the jet-to-background density contrast, primarily determine the dynamics and structures of the jet-induced flows. The entrainment of ambient gas and the background density and pressure gradient may also play significant roles. To emulate radio morphology, we produce the synthetic maps of the synchrotron surface brightness for the simulated jets, by employing simple models for magnetic field distribution and nonthermal electron population and considering relativistic beaming effects at different inclination angles. Both the flow structures and radio maps capture the longitudinal and transverse structures of the jet-spine and shear layer, consistent with observations. We also compare different background effects and argue that the loss of pressure confinement beyond the galactic core may be a key factor in the flaring and disruption of FR-I jets. Our results confirm that mildly relativistic jets could explain the one-sidedness or asymmetries with the boosted main jet and deboosted counterjet pairs.

Multiple chemical tracers finally unveil the intricate NGC 1333 IRAS 4A outflow system. FAUST XVI

ABSTRACT The exploration of outflows in protobinary systems presents a challenging yet crucial endeavour, offering valuable insights into the dynamic interplay between protostars and their evolution. In this study, we examine the morphology and dynamics of jets and outflows within the IRAS 4A protobinary system. This analysis is based on ALMA observations of SiO(5–4), H2CO(30, 3–20, 3), and HDCO(41, 4–31, 3) with a spatial resolution of ∼150 au. Leveraging an astrochemical approach involving the use of diverse tracers beyond traditional ones has enabled the identification of novel features and a comprehensive understanding of the broader outflow dynamics. Our analysis reveals the presence of two jets in the redshifted emission, emanating from IRAS 4A1 and IRAS 4A2, respectively. Furthermore, we identify four distinct outflows in the region for the first time, with each protostar, 4A1 and 4A2, contributing to two of them. We characterize the morphology and orientation of each outflow, challenging previous suggestions of bends in their trajectories. The outflow cavities of IRAS 4A1 exhibit extensions of 10 and 13 arcsec with position angles (PA) of 0° and -12°, respectively, while those of IRAS 4A2 are more extended, spanning 18 and 25 arcsec with PAs of 29° and 26°. We propose that the misalignment of the cavities is due to a jet precession in each protostar, a notion supported by the observation that the more extended cavities of the same source exhibit lower velocities, indicating they may stem from older ejection events.

Trumpet-shaped diffuse plasma jet in a semi-confined environment

Abstract This paper reports a unique trumpet-shaped diffuse plasma jet (TDPJ) with a caliber exceeding 30 mm in a semi-confined environment, which is larger than the diameter of existing atmospheric pressure plasma jets (APPJs) in an open environment. The morphology of the TDPJ is attributed to the influence of the electric field on the development characteristics of ionization waves in the ambient environment. High-speed ICCD camera images show that the plasma bullets in the TDPJ have a completely different propagation trajectory compared to the APPJ. Different shapes of diffuse plasma jets can also be formed by adjusting the doping gas, which is due to the Penning ionization and consistent with the impact of the electric field. This research reveals the long-neglected effect of the electric field on ionization waves and provides a way to manipulate the morphology of plasma jets efficiently. The generation mechanism of the TDPJ can provide preliminary guidance for the effective medical treatment of plasma jets in semi-confined environments, such as human internal organs.

Prognostic value of three-dimensional regurgitant orifice determination in functional mitral regurgitation

Abstract Background Functional mitral regurgitation (FMR) evaluation using effective regurgitant orifice (ERO) by echocardiography remains controversial. Given the morphology of regurgitant jets in FMR, determination of ERO using three-dimensional transesophageal echocardiography (3D-TEE) may be more accurate. However, a clear threshold for this parameter has not been defined. Purpose Our aim is to evaluate the prognostic value of 3D-ERO in FMR. Methods All patients with at least moderate FMR who underwent 3D-TEE in a tertiary center between 2016 and 2020 were retrospectively selected. Echocardiographic variables by transthoracic and transesophageal, as well as demographic and clinical history variables, were collected. A combined event of urgent hospital admission or death was considered. Variables statistically associated with the event were included in multivariate analysis. Results 112 patients (74 men (66.1%), mean age 72.3±10.9 years) were finally included. The most frequent etiology of FMR was ventricular dysfunction (61.6%), followed by annular dilation (23.2%) and posterior leaflet restriction (15.2%). The mean 3D-ERO was 0.53±0.25 cm2 and mean ejection fraction was 40.7±14.2%. At diagnosis, 49 patients (43.8%) were not receiving diuretics, 63 (56.2%) had atrial fibrillation/flutter, 60.3% permanent. FMR was treated in 54 patients (48.2%), 61,1% percutaneously. During a follow-up of 36 [14-54] months, 50 (44,6%) patients were urgently hospitalized (mean 1.9±2.8 admissions) and 49 (43,8%) died, received a heart transplant or LVAD. 3D-ERO was significantly associated with the occurrence of the event (0.55 vs 0.41; p=0.02). Additionally, 3D-ERO was associated with mitral intervention (0.58 vs 0.47 cm2; p=0.01) and had a trend towards death from any cause (0.56 vs 0.5 cm2; p=0.098). The prognostic capacity of 3D-ERO for the combined event was determined using an ROC curve (Figure). An AUC of 0.67 (95% CI 0.55-0.8; p=0.01) and an optimal cutoff value of 0.45 cm2 (sensitivity 0.62, specificity 0.73) were obtained. In univariate analysis, the combined event was also associated with age (73.9 vs. 65.6 years; p=0.01), diabetes (40 vs. 13.6%; p=0.02), chronic kidney disease (42.7 vs. 13.6%; p=0.01), ischemic heart disease (59.6 vs 31,8%, p=0.02) and daily furosemide dose (39.7 vs. 13.6 mg; p<0.01). In multivariate analysis of the event, age, daily furosemide dose, ischemic heart disease and 3D-ERO were included in the final predictive model (Table). Conclusions In patients with FMR, 3D-ERO was significantly associated with the occurrence of events during follow-up, with an optimal prognostic performance cutoff point of 0.45 cm2. Furthermore, it was an independent predictor of mitral intervention and included among the predictors of urgent hospital admission or death. Therefore, 3D-ERO may be useful in risk stratification of FMR.

The Morphology and Dynamics of Relativistic Jets with Relativistic Equation of State

We study the effect of plasma composition on the dynamics and morphology of relativistic astrophysical jets. Our work is based on a relativistic total variation diminishing simulation code. We use a relativistic equation of state in the simulation code that accounts for the thermodynamics of a multispecies plasma, which is a mixture of electrons, positrons, and protons. To study the effect of plasma composition, we consider various jet models. These models are characterized by the same injection parameters, same jet kinetic luminosity, and the same Mach numbers. The evolution of these models shows that the plasma composition affects the propagation speed of the jet head, the structure of the jet head, and the morphology, despite fixing the initial parameters. We conclude that electron-positron jets are the slowest and show more pronounced turbulent structures in comparison to other plasma compositions. The area and locations of the hot-spots also depend on the composition of the jet plasma. Our results also show that boosting mechanisms are an important aspect of multi-dimensional simulations, which are also influenced by the change in composition.

Analysis of the whole main structure morphological evolution and velocity distribution characteristics of a high-pressure water jet by an imaging experiment

Water jets play a crucial role in physically-fluidized coal mining. Analyzing the whole morphology and velocity characteristics of water jets is essential for the improvement of coal-breaking efficiency. An imaging experiment was performed to capture the intricate geometrical features of the water clusters and droplets at diverse distances from the exit of the nozzle. Based on the obtained results, a new classification of the jet structures has been proposed. Additionally, the axial of the jet velocity was predominantly characterized by a piecewise linear decreasing. For the coal-breaking efficiency of long-distance jets, the velocity could not be a major concern because the velocity attenuation is minimal. In contrast, the form of the jet is crucial for improvement. An empirical model of the high-efficiency jet impact radius was established, leading to the introduction of the concepts of critical, optimal, and farthest jet target distance, which will inform future research on high-efficiency coal-breaking.

Experimental study on pressure oscillation phenomenon of vertical upward bubble submerged jet under heave conditions

With the vigorous progress of nuclear industry under marine environment, the ocean motion will exacerbate the pressure oscillation phenomenon caused by the change of the steam-liquid interface during the jet, causing great harm and challenges to the security and steady operation of device related to steam submerged jets. Therefore, the effects of heave motion on the steam bubble morphology and pressure oscillation phenomenon of jets with vertically upward low mass fluxes were experimentally investigated. The experimental results show that when the heave motion is upward, the steam bubble will be stretched obviously in the necking and detachment stages; while when the heave motion is downward, the steam bubble will accumulate at the nozzle outlet during the growth initial stage. Compared with the land environment, the heave motion increases the dominant frequency and pressure pulses average amplitude, and the dominant frequency and pressure pulses average amplitude have a positive correlation with the heave amplitude and a negative correlation with the heave period. In addition, there is a positive correlation between the Strouhal number and the heave maximum acceleration amplitude. An experimental correlation is proposed to predict the dominant frequency in heave motion, and the error is basically within ±30%.

Effect of Inverse Compton Cooling on Relativistic Particles Accelerated at Shear Boundary Layers in Relativistic Jets

AbstractRecent theoretical considerations and observational evidence evince the spine-sheath morphology of relativistic jets emitted from active galactic nuclei (AGNs) or gamma-ray bursts (GRBs). The resulting shear boundary layers (SBLs) are likely to be an avenue for particle acceleration in relativistic jets. The effect of radiation drag on radiating particles has yet to be addressed in most studies of particle acceleration at shear boundary layers, even though radiative cooling may considerably affect particle dynamics. By using particle-in-cell simulations, we study the effects of inverse Compton cooling on particle dynamics and emerging particle spectra.

3D Space‐Time Adaptive Hybrid Simulations of Magnetosheath High‐Speed Jets

AbstractWe study the generation and evolution of spatially localized dynamic plasma pressure enhancements in the magnetosheath (high‐speed jets) by carrying out three‐dimensional hybrid simulations of the Earth's dayside magnetosphere with a novel, space‐time adaptive code, HYPERS. High‐speed jets are shown to occur downstream of quasi‐parallel bow shocks under southward and northward quasi‐radial interplanetary magnetic field conditions. The physical properties and three‐dimensional morphology of simulation jets are found to be consistent with general statistical knowledge acquired from the satellite observations. We discuss a “magnetokinetic” mechanism for jet origin whereby the compression of solar wind plasma and its penetration into the magnetosheath is tied to the turbulence‐driven magnetic field perturbations. We compare three‐dimensional jets to dynamic pressure structures observed in two‐dimensional hybrid simulations and demonstrate the impact of large jets on the magnetopause and the cusp.

Optimization of ultrasonographic ureteral jet detection and normal ureteral jet morphology in dogs.

Ureteral jets are visualized with ultrasound as echogenic streams extending from the ureterovesicular junction into the urinary bladder. In clinical practice, diuretics are sometimes administered to increase visibility of ureteral jets, however this has not been well described in the veterinary literature. The purpose of this prospective, crossover study was to describe the normal morphology of canine ureteral jets, determine an optimal protocol for diuretic administration to increase visibility of ureteral jets, and confirm in vitro the effect that differences in specific gravity and velocity have on visibility. Ultrasound of 10 normal dogs was performed at baseline and following 1mg/kg furosemide administered intravenously or subcutaneously. Increased numbers of ureteral jets were seen post-furosemide administration compared to baseline, with an overall increased number of ureteral jets identified following intravenous administration when compared to subcutaneous administration. Time to first ureteral jet was significantly shorter with intravenous compared to subcutaneous administration. Urine specific gravity significantly decreased following furosemide administration. For the in vitro study, saline solutions of varying specific gravities were infused into a bath of hypertonic saline with specific gravity of 1.037. There was good visibility in vitro with infusion of solutions of specific gravities of 1.010-1.025. Infusion of saline solution with a specific gravity of 1.030 had reduced visibility, while infusion of saline with equivalent specific gravity (1.037) was not visible with B-mode ultrasonography. Both intravenous and subcutaneous furosemide administration significantly increase ureteral jet detection with ultrasound secondary to differences in specific gravity, confirming results of prior studies.

Continuous Jets and Backflow Models for the Formation of W50/SS 433 in Magnetohydrodynamics Simulations

Abstract The formation mechanism of the W50/SS 433 complex has long been a mystery. We propose a new scenario in which the SS 433 jets themselves form the W50/SS 433 system. We carry out magnetohydrodynamics simulations of the propagation of two side jets using the public code CANS+. As found in previous jet studies, when the propagating jet is lighter than the surrounding medium, the shocked plasma flows back from the jet tip to the core. We find that the morphology of light jets is spheroidal at early times; afterward, the shell and wings are developed by the broadening spherical cocoon. The morphology depends strongly on the density ratio of the injected jet to the surrounding medium. Meanwhile, the ratio of the lengths of the two side jets depends only on the density profile of the surrounding medium. We also find that most of the jet kinetic energy is dissipated at the oblique shock formed by the interaction between the backflow and beam flow, rather than at the jet terminal shock. The position of the oblique shock is spatially consistent with the X-ray and TeV gamma-ray hotspots of W50.

A novel method to characterize morphological dynamics and determine flashing jet regimes

Spray cone angle (θ) and width (H) have been widely used to characterize morphology of jets. However, to a flashing jet, their capabilities are restrained by two flaws: (a) they are variable as a function of axial distance (θ (H)=f(x)), leading to nonunified θ or H at different axial locations, and (b) fail to precisely capture key characteristics of nonlinear boundary of expansion zone, resulting in their disability to determine the flashing jet regimes. In this work, a power function |y|=kx0.5, in which x and y are axial and radical directions respectively, characterizing the nonlinear boundary of expansion zone of flashing jet is proposed. A variety of experiments are conducted to validate the proposed method. Experimental results demonstrate that the graphical parameter k unifies a cluster of spray angles (θ=f(x))), and furthermore, owns a good capability to characterize morphological dynamics of flashing jet. These merits allow k to determine the flashing jet regimes. In this work, k<1, 1<k<5, and k>5 are the determining criteria for the external, internal transition, and full flashing jet regimes, respectively.

Determining mass-accretion and jet mass-loss rates in post-asymptotic giant branch binary systems

Aims. In this study we determine the morphology and mass-loss rate of jets emanating from the companion in post-asymptotic giant branch (post-AGB) binary stars with a circumbinary disc. In doing so we also determine the mass-accretion rates onto the companion, and investigate the source feeding the circum-companion accretion disc. Methods. We perform a spatio-kinematic modelling of the jet of two well-sampled post-AGB binaries, BD+46°442 and IRAS 19135+3937, by fitting the orbital phased time series of Hα spectra. Once the jet geometry, velocity, and scaled density structure are computed, we carry out radiative transfer modelling of the jet for the first four Balmer lines to determine the jet densities, thus allowing us to compute the jet mass-loss rates and mass-accretion rates. We distinguish the origin of the accretion by comparing the computed mass-accretion rates with theoretically estimated mass-loss rates, both from the post-AGB star and from the circumbinary disc. Results. The spatio-kinematic model of the jet reproduces the observed absorption feature in the Hα lines. The jets have an inner region with extremely low density in both objects. The jet model for BD+46°442 is tilted by 15° with respect to the orbital axis of the binary system. IRAS 19135+3937 has a smaller tilt of 6°. Using our radiative transfer model, we find the full 3D density structure of both jets. By combining these results, we can compute the mass-loss rates of the jets, which are of the order of 10−7 − 10−5 M⊙ yr−1. From this we estimate mass-accretion rates onto the companion of 10−6 − 10−4 M⊙ yr−1. Conclusions. Based on the mass-accretion rates found for these two objects, we conclude that the circumbinary disc is most likely the source feeding the circum-companion accretion disc. This is in agreement with the observed depletion patterns in post-AGB binaries, which is caused by re-accretion of gas from the circumbinary disc that is under-abundant in refractory elements. The high accretion rates from the circumbinary disc imply that the lifetime of the disc will be short. Mass transfer from the post-AGB star cannot be excluded in these systems, but it is unlikely to provide a sufficient mass-transfer rate to sustain the observed jet mass-loss rates.

Using synchrotron emission modelling of relativistic hydrodynamic jet simulations to study the FR I/FR II dichotomy of active galactic nuclei radio jets

In this paper three dimensional relativistic hydrodynamic simulations of AGN jets are presented to investigate the FR I/FR II dichotomy. Three simulations are presented which illustrates the difference in morphology for high/low Lorentz factor injection as well as a stratified background medium. Lorentz factors of 10 and 1.0014 were used for the high and low Lorentz factor cases respectively. The hydrodynamic simulations show a division in the morphology of jets based on their initial injection luminosity. An additional simulation was set up to investigate the evolution of the low Lorentz factor jet if the mass injection was lowered after a certain time. A synchrotron emission model was applied to these simulations to reproduce intensity maps at radio frequencies (1.5GHz) which were compared to the observed emission structures of FR I/FR II radio galaxies. The effect of Doppler boosting on the intensity maps was also investigated for different polar angles. The intensity maps of both the high and low Lorentz factor cases reproduced emission structures that resemble those of FR II type radio galaxies with a dominant cocoon region containing time dependent hot spots and filaments. An FR I like structure was, however, produced for the low Lorentz factor case if the mass injection rate was lowered after a set time period.

Implications of River Discharge Angle and Basin Slope on Mouth Bar Morphology and Discharge Dynamics of Stable Jets

AbstractRiver mouth bars are strategic morphological units primarily responsible for the development of entire deltaic systems and coastline configuration. Although many works during the last decad...

A new method for extending solutions to the self-similar relativistic magnetohydrodynamic equations for black hole outflows

The paradigm in which magnetic fields play a crucial role in launching/collimating outflows in many astrophysical objects continues to gain support. However, semi-analytical models including the effect of magnetic fields on the dynamics and morphology of jets are still missing due to the intrinsic difficulties in integrating the equations describing a collimated, relativistic flow in the presence of gravity. Only few solutions have been found so far, due to the highly nonlinear character of the equations together with the need to blindly search for singularities. These numerical problems prevented a full exploration of the parameter space. We present a new integration scheme to solve r-self-similar, stationary, axisymmetric magnetohydrodynamics equations describing collimated, relativistic outflows crossing smoothly all the singular points (Alfven point and modified slow/fast points). For the first time, we are able to integrate from the disk mid-plane to downstream of the modified fast point. We discuss an ensemble of jet solutions, emphasising trends and features that can be compared to observables. We present, for the first time with a semi-analytical MHD model, solutions showing counter-rotation of the jet for a substantial fraction of its extent. We find diverse jet configurations with bulk Lorentz factors up to 10 and potential sites for recollimation between $10^3-10^7$ gravitational radii. Such extended coverage of the intervals of quantities, such as magnetic-to-thermal energy ratios at the base or the heights/widths of the recollimation region, makes our solutions suitable for application to many different systems where jets are launched.

Evolving morphology of the large-scale relativistic jets from XTE J1550−564

We present an in-depth study of the large-scale, western jet of the microquasar XTE J1550-564, based on X-ray and radio observations performed in 2002-2003. The jet is spatially resolved in both observing windows. The X-ray jet is expanding in time along the axis of the jet's propagation: we observe the formation of a tail (~2.25"), which appears to extend backwards with an apparent velocity ~-0.10c. The origin of this feature is discussed in the framework of scenarios of energy dissipation. A single power-law adequately describes the broadband spectra, supporting a synchrotron origin of the X-ray emission. However, a spectral break at ~10^{15} Hz is necessary in coincidence with a re-flare at 8.64 GHz in September 2002. This finding may be indicative of emission from newly accelerated low-energy particles. The first detection of the jet is in February 2001 (F_{8.64GHz}=0.25+/-0.09 mJy) in the flux rising phase. A phase of stable emission is followed by a rapid decay (t_{decay}=167+/-5 days). The decay at radio frequencies is significantly shorter than in X-rays (t_{decay}=338+/-14 days). We detected a high fraction (up to ~9%) of linearly polarized radiation at 4.8 GHz and 8.6 GHz. The orientation of the electric vector is consistent with the picture of a shock-compressed magnetic field, and there are hints of variations on month-timescales, possibly connected with the evolution of the jet structure.

Sublimation of icy aggregates in the coma of comet 67P/Churyumov–Gerasimenko detected with the OSIRIS cameras on boardRosetta

Beginning in March 2014, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analyzed the dust monitoring observations shortly after the southern vernal equinox on May 30 and 31, 2015 with the WAC at the heliocentric distance Rh = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this article was that through the sublimation of the aggregates of dirty grains (radius a between 5 microm and 50 microm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data we needed to inject a number of aggregates between 8.5 x $10^{13}$ and 8.5 x $10^{10}$ for a = 5 microm and 50 microm respectively, or an initial mass of $H_2O$ ice around 22kg.

Scientific assessment of the quality of OSIRIS images

OSIRIS, the scientific imaging system on board the ESA Rosetta spacecraft, has been imaging the nucleus of comet 67P/Churyumov-Gerasimenko and its dust and gas environment since March 2014. The images serve different scientific goals, from morphology and composition studies of the nucleus surface, to the motion and trajectories of dust grains, the general structure of the dust coma, the morphology and intensity of jets, gas distribution, mass loss, and dust and gas production rates. Aims. We present the calibration of the raw images taken by OSIRIS and address the accuracy that we can expect in our scientific results based on the accuracy of the calibration steps that we have performed. Methods. We describe the pipeline that has been developed to automatically calibrate the OSIRIS images. Through a series of steps, radiometrically calibrated and distortion corrected images are produced and can be used for scientific studies. Calibration campaigns were run on the ground before launch and throughout the years in flight to determine the parameters that are used to calibrate the images and to verify their evolution with time. We describe how these parameters were determined and we address their accuracy. Results. We provide a guideline to the level of trust that can be put into the various studies performed with OSIRIS images, based on the accuracy of the image calibration.