jet trajectory
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2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Wen Han Chiu ◽  
Zhen Liu ◽  
Matthew Low ◽  
Lian-Tao Wang

Abstract The measurement of the arrival time of a particle, such as a lepton, a photon, or a pion, reaching the detector provides valuable information. A similar measurement for a hadronic final state, however, is much more challenging as one has to extract the relevant information from a collection of particles. In this paper, we explore various possibilities in defining the time of a jet through the measurable arrival times of the jet constituents. We find that a definition of jet time based on a transverse momentum weighted sum of the times of the constituents has the best performance. For prompt jets, the performance depends on the jet trajectory. For delayed jets, the performance depends on the trajectory of the jet, the trajectory of the mother particle, and the location of the displaced vertex. Compared to the next-best-performing jet time definition, the transverse momentum weighted sum has roughly a factor of ten times better jet time resolution. We give a detailed discussion of the relevant effects and characterize the full geometrical dependence of the performance. These results highlight the critical importance of using a proper definition of jet time with its corresponding detector-dependent calibration and the exciting possibility of deepening our understanding of jets in the time domain.


Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 110
Author(s):  
Dmitry Bisikalo ◽  
Andrey Sobolev ◽  
Andrey Zhilkin

In this paper, the characteristics of hot spots on an accretor surface are investigated for two types of polars: the eclipsing synchronous polar V808 Aur and the non-eclipsing asynchronous polar CD Ind in configuration of an offset and non-offset magnetic dipole. The drift of hot spots is analyzed based on the results of numerical calculations and maps of the temperature distribution over the accretor surface. It is shown that a noticeable displacement of the spots is determined by the ratio of ballistic and magnetic parts of the jet trajectory. In the synchronous polar, the dominant influence on the drift of hot spots is exerted by variations in the mass transfer rate, which entail a change in the ballistic part of the trajectory. It was found that when the mass transfer rate changes within the range of 10−10M⊙/year to 10−7M⊙/year, the displacement of the hot spot in latitude and longitude can reach 30∘. In the asynchronous polar, a change in the position of hot spots is mainly defined by the properties of the white dwarf magnetosphere, and the displacement of hot spots in latitude and longitude can reach 20∘.


Author(s):  
Yong Zhang ◽  
Yuyang Liu ◽  
Xigang Yang ◽  
Guoqing Chen ◽  
Baosheng Jin

Abstract For an air staged combustion boiler, the rational organization of jets to form closing-to-wall film using as little air as possible plays a key role in resolving the high temperature corrosion problems. In this work, a comprehensive computational fluid dynamics (CFD) model including hydrodynamics and coal combustion is established for a 660 MW opposed wall fired boiler. Based on the grid independence and model validation, the flow field, temperature profile, and species concentration are predicted, and the influences of the structure of nozzles and the operation parameter of jets are further evaluated. The results show that the corrosion area of the side wall is dependent on the jet projection velocity and nozzle structures. The increase of the jet velocity does not always have an active influence on the reduction of corrosive area. Only increasing the nozzle diameter does not always have a positive impact on the improvement of the corrosion. The increase of the jet inclination angle can extend the jet trajectory, contributing to increase the oxygen coverage area. Reasonably adjusting the jet inclination angle of each layer can obtain the lower corrosion area. The increase of jet row number leads to a decrease in the spacing between rows, which enables the downstream jet to penetrate deeper into the cross stream. By increasing the number of jet layers and reducing the jet velocity of each layer, the lowest corrosion area can be obtained.


2021 ◽  
Vol 62 (10) ◽  
Author(s):  
Francesca De Serio ◽  
Roni H. Goldshmid ◽  
Dan Liberzon ◽  
Michele Mossa ◽  
M. Eletta Negretti ◽  
...  

AbstractThe present study has the main purpose to experimentally investigate a turbulent momentum jet issued in a basin affected by rotation and in presence of porous obstructions. The experiments were carried out at the Coriolis Platform at LEGI Grenoble (FR). A large and unique set of velocity data was obtained by means of a Particle Image Velocimetry measurement technique while varying the rotation rate of the tank and the density of the canopy. The main differences in jet behavior in various flow configurations were assessed in terms of mean flow, turbulent kinetic energy and jet spreading. The jet trajectory was also detected. The results prove that obstructions with increasing density and increased rotation rates induce a more rapid abatement of both jet velocity and turbulent kinetic energy. The jet trajectories can be scaled by a characteristic length, which is found to be a function of the jet initial momentum, the rotation rate, and the drag exerted by the obstacles. An empirical expression for the latter is also proposed and validated. Graphic abstract


2021 ◽  
Vol 125 (1291) ◽  
pp. 1519-1541
Author(s):  
Y. Zhu ◽  
X. Sun ◽  
V. Sethi ◽  
P. Gauthier ◽  
S. Guo ◽  
...  

ABSTRACTThe commercial Computational Fluid Dynamics (CFD) software STAR-CCM+ was used to simulate the flow and breakup characteristics of a Liquid Jet Injected into the gaseous Crossflow (LJIC) under real engine operating conditions. The reasonable calculation domain geometry and flow boundary conditions were obtained based on a civil aviation engine performance model similar to the Leap-1B engine which was developed using the GasTurb software and the preliminary design results of its low-emission combustor. The Volume of Fluid (VOF) model was applied to simulate the breakup feature of the near field of LJIC. The numerical method was validated and calibrated through comparison with the public test data at atmospheric conditions. The results showed that the numerical method can capture most of the jet breakup structure and predict the jet trajectory with an error not exceeding ±5%. The verified numerical method was applied to simulate the breakup of LJIC at the real engine operating condition. The breakup mode of LJIC was shown to be surface shear breakup at elevated condition. The trajectory of the liquid jet showed good agreement with Ragucci’s empirical correlation.


2021 ◽  
pp. 1-30
Author(s):  
Michelle Otero ◽  
Tommy Genova ◽  
Bernhard Stiehl ◽  
Anthony Morales ◽  
Scott Martin ◽  
...  

Abstract This work experimentally investigates the effects of elevated combustor pressures on the characteristics of a lean premixed reacting methane/air jet injected into a lean vitiated crossflow using a 12.7mm axial jet. Experiments were conducted in an axially staged combustor, which implements a reacting jet in crossflow (RJIC) configuration and operates over a pressure range of 1 to 5 atmospheres. Simultaneous CH* chemiluminescence and Particle Image Velocimetry (PIV) are used to study the flow field and flame behavior. The results show that the reacting jet trajectory exhibits greater penetration with elevated pressure, which is a novel finding compared to available data in the literature. However, the flame lift-off point and ignition delay time both decreased with elevated pressure, which was attributed to decreased vorticity along the flame boundary which corresponds to increased Damköhler numbers (Da). Emissions measurements confirm the NOx increase with pressure as reported in the literature for single stage gas turbine combustors. Concurrently, emission measurements for the staged configuration show the strong NOx benefit of the RJIC system: the data proves a reduction of global outlet emission levels at elevated pressure with the axially staged configuration. The axial emission reduction was attributed to the decreasing lift-off at elevated pressure levels. Hence, the research emphasizes that the flame and emission characteristics are coupled; they are not only dependent on the geometric parameters and momentum flux ratios but are also a function of pressure.


Author(s):  
Dumitru I. Caruntu ◽  
Simon Padron ◽  
Karen Lozano

Abstract Forcespinning is a novel method that makes use of centrifugal forces to produce nanofibers rapidly and at high yields. To improve and enhance the forcespinning production method, a 2D computational forcespinning inviscid fluid dynamics model is developed. Two models, namely time-independent and time-dependent, are obtained in order to investigate the influence of various parameters on fiber forcespinning formation (trajectory, jet diameter, tangential velocity). The fluid dynamics equations are solved using the method of multiple scales along with the finite difference method, and including slender-jet theory assumptions. It is important to produce jets with small diameters in the micro- and nano-range. The Weber (We) and Rossby (Rb) numbers were found to both expand the jet trajectory as they increased. Increasing We and/or decreasing Rb was found to decrease the jet diameter. Also, by varying forcespinning parameters, it has been found that the jet radius can be decreased by increasing the jet exit angle in the direction of rotation, reducing the spinneret fluid level, increasing the angular velocity of the spinneret, reducing spinneret length, and/or reducing the orifice diameter. Knowing the jet trajectories is important for designing and positioning of fiber collector. It has been found that the trajectories expand out with the increase of the jet exit angle in the direction of rotation, increase of fluid level, increase of angular velocity, and/or increase of the spinneret length. Production rates and jet radii for any predetermined radial collector distance were also determined.


2021 ◽  
Vol 915 ◽  
Author(s):  
Girish K. Jankee ◽  
Bharathram Ganapathisubramani

Abstract


2021 ◽  
Vol 143 (12) ◽  
Author(s):  
Bernhard Stiehl ◽  
Tommy Genova ◽  
Michelle Otero ◽  
Scott Martin ◽  
Kareem Ahmed

Abstract Three reacting jet-in-crossflow (JiC) methane/air flames were numerically investigated in a lean axially staged combustor at a pressure of five atmospheres. A detailed chemistry Star-CCM+ computational fluid dynamics (CFD) model was used with 53 species considered and the result of turbulence-governed finite-rate modeling was validated with in-house experimental data. An optically accessible test section features three side windows, allowing local flow and flame analysis with particle image velocimetry (PIV) and CH* chemiluminescence as well as pressure, temperature, and species exit measurements. The research objective was to predict and verify NOx formation of the premixed 12.7 mm axial jet. Three headend temperature levels were investigated along with three premixed jets at lean (φJet = 0.75), near-stoichiometric (φJet = 1.07), and rich (φJet = 1.78) axial fuel line equivalence ratio. Based on the matching exit emission concentration, global emission benefits were investigated by adjustment of the fuel stratification. The perfectly premixed methane/air flames of this study were shown to ignite at the lee-side of the jet. For the elevated headend temperature level T = 1800 K, the flame extended beyond the windward jet trajectory and caused high axial NO production. For industry application, a firing temperature of 1920 K was achieved with a NOx optimized fuel split of 25%, combining a lean headend (φHeadend = 0.61) with a rich (φJet = 1.78) jet equivalence ratio. This operating point allowed minimization of the combustor residence time at temperatures above 1700 K as well as combustion in a compact flame at the jet lee-side along the counter rotating vortex pair.


2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Yang Qu ◽  
◽  
Xintian Liu ◽  
Minghui Zhang ◽  
Yansong Wang ◽  
...  

To study the precision of the fire water monitor with important influence on fire extinguishing effect, the drop point of fire water monitor is studied. The quadratic drag model is selected on the basis of the analysis of the mechanical model of the fluidic microbody, considering the change of the cross-sectional area caused by velocity and breakup of the water jet. The boundary between breakup and atomization is clarified, and the change of diameter and area of the droplet is also discussed based on the theory of liquid jet breakup, to build a dynamic breakup model of air resistance and broken jet. The jet trajectory of the fire water monitor is mainly influenced by the initial velocity, pitching angle, air resistance, and other factors. In this paper, the influence of different parameters on the jet drop point is considered. The analysis and comparison of all the points are performed, and the range of uncertainty is obtained. Finally, the accurate prediction of the jet trajectory is analyzed.


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