Orifice Configuration Research Articles

Scorpion-inspired multi-scale contact enabled multifunctional piezoresistive pressure sensor based on hybrid nanofiber decoration

Inspired by the slit organs of scorpions, an array narrow orifice configuration (ANOC) piezoresistive foam sensors are developed by decorating hybrid polypyrrole (PPy)/ carbon nanotubes (CNT) nanofibers on the foam strut. The developed ANOC composite foam exhibits a unique multi-scale contact sensing mechanism enabled by the macro-scale internal dome structures, the micro-scale struts of the porous foam, the nano-scale PPy/CNT hybrid conductive networks, and the nano-scale friction of the rough CNT/PPy hybrid nanofibers (NFs), which rendered the ANOC composite foam an ultra-high sensitivity of 1.8 kPa−1 at low pressure within 1.5 kPa. When used as a piezoresistive pressure sensor, the ANOC composite foam exhibits a wide detection range (0 %-70 %), fast response/recover time (120/90 ms), and long-term stability and fatigue resistance (over 80000 s), and demonstrated capability to monitor various human activities. A smart cushion integrated with an array of foam sensors can accurately identify the human sitting positions and posture rectifying. Moreover, owing to the highly porous conductive network and the doped ions, the ANOC composite foam can generate energy from saline water and serve as a water-induced energy generation (WIEG) device for direct energy supply. This research paves the way for the development of multifunctional high-performance.

Experimental investigation of metal foam embedded surface thermal characteristics using air-jet impingement with different orifice geometry

Experimental investigation of metal foam embedded surface thermal characteristics using air-jet impingement with different orifice geometry

Physics-Informed Acoustic Liner Optimization: Balancing Drag and Noise

Pore-resolved direct numerical simulations (DNS) of turbulent flows grazing over acoustic liners with aerodynamically and/or acoustically optimized orifice configurations are presented. The DNS explore a large parameter space, studying various families of orifice geometries, including the influence of orifice shape, orientation, and the number of orifices. All flow cases show an increase in drag compared to the smooth wall. However, the added drag can be reduced by as much as approximately 55% as compared to conventional acoustic liners by simply altering the shape of the orifice or its orientation, in the case of a noncircular orifice. Complementary acoustic simulations demonstrate that this reduced drag may be achieved while maintaining the same noise reduction properties over a wide range of frequencies.

Effect of Outlet Shape on Flame Height of Transformer Oil Jet Fire Under External Fire Source

Abstract In this inquiry, we delve into the manner by which disparate orifice configurations exert influence upon the elevation of the jet flame when subjected to an external conflagration, employing empirical simulations. Elaborating upon the empirical dataset, we introduce the derivative of hydraulic diameter alterations and the velocity of material degradation, thereby revising the traditional non-dimensionalized model of flame altitude. The revelations disclose that, across an array of orifice profiles, the conflagration jet within oil-laden apparatus undergoes four discernible phases of evolution, each replete with variable flambeau altitudes. In disparate operational circumstances, the quantified velocity of material degradation during the evolution phase manifests an exponential interrelation with the approximated value of the model. Conversely, the phases of stability and decline adhere to a potency function connection. A quantitative delineation of the pivotal states for each phase of combustion is achieved through the evaluation of the rate of alteration in the velocity of material degradation. Significantly, the pivotal juncture for the proliferation and equilibrium stage is ascertained to be 2 g/s. This scientific inquiry confers invaluable theoretical reinforcement for fire safeguarding and catastrophe evaluation within substations accommodating oil-infused apparatus.

Noise and Jet Momentum of Synthetic Jet Actuators with Different Orifice Configurations

Sound pressure levels and flow characteristics of a synthetic jet actuator (SJA) are investigated experimentally using the following orifice configurations: a) a slender rectangular slot orifice and b) an array of circular orifices with two different orifice diameters. All configurations have similar total orifice neck area, orifice height, and cavity volume, resulting in a similar Helmholtz frequency. Experiments are conducted for orifices mounted on a flat plate under a quiescent condition. The mean jet velocity exhibits resonant peaks at several excitation frequencies, which also gave rise to the sound pressure levels. The resonant frequencies and peak jet velocities were found to depend on the excitation amplitude and orifice configuration. Investigation of the jet momentum penetration into the quiescent air above the different orifice configurations shows that the momentum issuing from the rectangular slot decays much quicker than that of the circular orifices, irrespective of whether the SJA is excited at resonance or not. The most favorable performance (i.e., the highest momentum in the jet core) was obtained with the array of circular orifices having a smaller orifice diameter, even at off-resonance excitations. The work herein shows the possibility of reducing the SJA noise by 8–10 dB by operating the SJA at a frequency away from the Helmholtz frequency while still achieving comparable levels of jet momentum penetration into the crossflow.

The circulation growth of non-impulsive starting jet

An analytical model that can be used to predict the circulation growth process for non-impulsive starting jets has been developed by extending the over-pressure correction model for impulsive starting jets. Only the jet velocity function U0(t) is needed to obtain the circulation growth process of non-impulsive starting jet. The non-impulsive starting jets generated by nozzle and orifice configurations are performed numerically with two acceleration schemes (represented by two kinds of velocity functions) and different acceleration stage stroke ratios LaD (modifying the acceleration time ta in each velocity function to obtain LaD=0.05:0.2:1.25) to verify the accuracy of the proposed analytical model. The influence of radial velocity distribution in the jet inflow boundary is ignored in the process of constructing this model, but this has been proven to be reasonable. The time-averaged relative error with the growth process of the total circulation predicted by this model is about 11% to 26%, which is smaller than the 44% to 88% obtained by the classical slug model. For the range of LaD from 0.05 to 1.25, the relative error with the prediction of the total circulation at the end of the acceleration stage is from 4% to 28%, as compared to the 39% to 96% for the slug model.

Unsteady flow behaviors and noise generation mechanisms of tandem orifices in a circular duct

Turbulent flow through tandem orifices in a circular duct is numerically modeled through dynamic delayed detached-eddy simulations to clarify the unsteady flow behaviors and noise generation mechanism. The characteristics of four configurations with different separation distances L/D = 0 (single orifice), 1, 2, and 4 are compared at a Reynolds number of 10 000. The acoustic sources and their noise-propagation behaviors are analyzed using Lighthill's acoustic analogy. The coherent flow structures (wavepackets) are determined through spectral proper orthogonal decomposition to clarify the resulting flow noise mechanism. The dominant noise sources are acoustic dipoles that are alternately energetic on the orifice's leading and trailing faces subjected to intermittent interaction with the unsteady flow. The total sound pressure level (SPL) for a single orifice is alternately dominated by the shedding and flapping behaviors of the large-scale vortical structures in the low-frequency range and Kelvin–Helmholtz (K–H) type wavepackets at high frequencies. For the tandem orifice configuration with L/D = 1, the total SPL is dominated by the contribution of the trailing face, attributable to the interactions between the K–H-type double-wavepacket structures. Both the upstream and downstream wavepackets start to split and generate four-wavepacket structures in the high-frequency range. In the cases of L/D = 2 and 4, the total SPL is dominated by the dipole sources at the downstream leading face that subjected to the intermittent interaction with the upstream separated shear layers. The dominant flow structures are independent wavepackets through each orifice at low frequencies, while at high frequencies the four-wavepacket structures break into two independent double-wavepacket structures close to each orifice.

Effects of catheter orifice configuration (triple-hole versus end-hole) in continuous infraclavicular brachial plexus block on analgesia after upper limb surgery.

The configuration of a nerve block catheter may affect the local anesthetic spread in epidural analgesia and continuous peripheral nerve blocks. This prospective and randomized study aims to compare the multi-orifice nerve block catheter with an end-hole catheter in ultrasound-guided continuous infraclavicular brachial plexus block (BPB) in terms of providing postoperative analgesia for the orthopedic upper limb surgery below the shoulder. The primary outcome measure was mean pain scores. Secondary outcome measures were the consumption of rescue analgesic and the amount of local anesthetics delivered by a Patient-Controlled Analgesia (PCA) device. A total of 58 adult patients who underwent orthopedic upper limb surgery below the shoulder were randomly assigned into two groups: group end-hole catheter (EHC) (n=31) and group multi-orifice catheter (MOC) (n=27). All patients received a single-shot infraclavicular BPB using 100 mg lidocaine 2% and 75 mg bupivacaine 0.5% administrated through a Tuohy needle. Then, a multi-orifice (triple-hole) nerve catheter was placed in the group MOC and an end-hole (one-hole) catheter in the group EHC at the same location. Bupivacaine 0.125% was infused through the catheters via PCA (infusion rate: 2 mlh-1, automated regular bolus: 5 mlh-1, patient-controlled bolus: 3 ml, lock-out time: 1 hour, 4 hours limit: 40 ml). Pain intensity was evaluated using a visual analogue scale (VAS). Mean VAS scores were higher in group EHC than group MOC in the first postoperative day (p=0.001). Mean rescue analgesic consumption, the number of bolus demand on PCA, PCA bolus demand dose, and total PCA dose were higher in group EHC than group MOC during the first postoperative day (p<0.05). It is concluded that the use of MHC is more effective than EHC for continuous infraclavicular brachial plexus blocks in providing postoperative pain relief during the first 24 hours.

Flow and heat transfer characteristics of single and multiple synthetic jets impingement cooling

In this paper, the comparison between synthetic jet actuator with single axisymmetric orifice and multiple axisymmetric orifices is presented. The aim of this paper is to compare the flow and heat transfer characteristics of single and multiple synthetic jet impingements cooling. The multiple orifice configurations had a central orifice and a satellite orifices placed in the pitch circle. The synthetic jet actuator had central orifice with 0, 3, 4, 5 and 6 orifices placed in the diameters of the relative pitch circle p/d = 2.5, 3 and 4. A total of 13 various geometric configurations were tested experimentally. In the multiple orifice configurations, the total cross-section area was approximately equal to the cross-section area of the single orifice configuration. The input power delivered to the synthetic jet actuator was maintained constant and equal to 3.00 W. The synthetic jet actuator energetic efficiency, Reynolds number, equivalent Reynolds number, radial and axial distributions of pressure coefficient, and heat transfer characteristic were presented. The synthetic jet issuing from multiple orifice plate merged at some axial distance, creating a single axisymmetric jet. The merging jet axial distances were determined for all investigated configurations. In the present paper, the integral quantities averaged over all orifices cross section area, or over impingement plate much larger than total orifices area, were analyzed for the purpose of objective comparison. From all various investigated parameters obtained from five different and independent experimental methods, the following conclusion may be made: if the total orifice cross section area in the case of single and multiple orifice synthetic jet is similar and real power deliver to the SJA is maintained at the same level the resulting equivalent Reynolds number and equivalent dimensionless stroke length achieved similar values and the impinging jet equivalent Nusselt number also achieved comparable values and distributions.

Influences of the pre-chamber orifices on the combustion behavior in a constant volume chamber simulating pre-chamber type medium-speed gas engines

The study aims to clarify the influence of pre-chamber (PC) configurations on the combustion process in the main chamber (MC) of medium-speed spark-ignition gas engines equipped with an active PC. A constant volume combustion chamber was prepared to simulate the chamber configurations of the gas engines. A high-speed shadowgraph was applied to visualize the torch flame development and the combustion process in the MC. Experiments were done by changing the charged gas in the MC, the number, and the diameter of the PC orifices. Combustion was most accelerated when the PC orifice configuration was set appropriately so that the adjacent torch flames would combine with each other. It was also found that the unburned mixture in the PC, which ejected prior to the torch flame, supported the penetration of the torch flame.

Experimental investigation on flow characteristics and unsteady heat transfer of noncircular impinging synthetic jets

This study investigates the flow characteristics and unsteady heat transfer of noncircular synthetic jets impinging on a heated plate. Thermographic phosphor thermometry and time-resolved particle image velocimetry are used to acquire quantitative wall temperature and flow field information, respectively. At a constant orifice-to-wall distance (H/De = 7.5), five orifice configurations (circular, square, elliptic with aspect ratio (AR) of 3, and rectangular with ARs of 3 and 5) are examined at a wall temperature of 80 °C. The orifice configuration has a significant effect on the heat transfer and vortex behavior of the impinging synthetic jets. The square orifice displays better stagnation cooling performance with 42% increase in the maximum stagnation cooling coefficient relative to the circular case due to the larger impinging velocity and deeper penetration into the wall shear layer. Axis-switching of the vortex rings is detected for both the elliptic and rectangular orifices before they impinge onto the wall. The axis-switching enhances the near-wall mixing and turbulent kinetic energy in the elliptic and rectangular orifices, and thus heat transfer compared with the circular case. Additionally, stronger vortices and deeper penetration into the wall shear layer are observed in the major-axis plane than in the minor-axis plane, leading to enhanced heat transfer in the major-axis direction. In particular, the rectangular orifice with an AR of 5 induces strong secondary structures in the trailing jet following the primary vortex ring, and these are responsible for the double-peak distribution of wall temperature in the major-axis direction. This is the first time a double-peak temperature distribution has been reported for noncircular impinging synthetic jets. The rectangular orifice with an AR of 5 also yields a larger cross-stream velocity in the minor-axis direction, indicating a stronger wall jet. Thus, among the cases considered in this study, the rectangular orifice with AR = 5 achieves the optimal cooling performance and the maximum time-averaged cooling area reaches more than 14 times the jet orifice area.

Effective ureteral access sheath insertion during flexible ureteroscopy: Influence of the ureteral orifice configuration.

We sought to determine the possible predictors for effective insertion of the ureteral access sheath (UAS) during flexible ureteroscopy (fURS) in virgin ureters and their impact on postoperative ureteral wall injury and the procedural outcome. A retrospective review of prospectively collected data was performed for all consecutive patients scheduled for fURS of virgin ureters at two tertiary care centers between 2018 and 2020. Demographics, stone characteristics, and perioperative data, including the configuration of the ureteral orifice (UO) over introductory guidewire insertion, were collected. Multivariate logistic regression was used to detect possible predictors of successful UAS insertion. In total, 128 patients who underwent primary fURS were included, with a mean age of 43.3±12.3 years and a stone burden of 12.3±6.9 mm. One hundred and ten patients (85.9%) achieved successful ureteral access insertion, including 81 (63.3%) without ureteral dilatation and 35 with dilation, of which 29 (22.7%) had a successful UAS afterward, while six failed. Total patients who underwent ureteral orifice dilatation were 35. 29 had a successful UAS afterward, while 6 failed. Patients who underwent successful UAS placement into virgin ureters were significantly older and had a lower body mass index (BMI). A tent-shaped UO over the guidewire led to successful UAS insertion. In multivariate regression analysis, cases with BMI <30 kg/m2 (odds ratio [OR] 1.89, 95% confidence interval [CI] 1.28-7.03) and those with a tent-shaped UO over the introductory guidewire (OR 6.60, 95% CI 3.8-7.2) maintained their significance to predict successful UAS insertion into virgin ureters. Nine patients (8.2%) had ureteral mucosal injuries, and the overall stone-free rate was 78.2%. Patients with normal BMIs and tent-shaped UOs over the introductory guidewires are more likely to achieve primary UAS insertion without the need for ureteral dilation.

Effects of Orifice Configuration on the Flame Propagation and Mechanism of Jet Ignition under Elevated Temperature and Pressure

Effects of Orifice Configuration on the Flame Propagation and Mechanism of Jet Ignition under Elevated Temperature and Pressure

Experimental & numerical study of different orifice configurations for helical coil Once Through Steam Generator

The main aim of the present study is to aid the selection of suitable orifice configuration for helical coil once-through steam generators being designed for SMRs. The selection of orifice is based on the pressure drop occurring in the orifice over the desired flow range, the minimum length required for the orifice, repeatability of the results, and ease of fabrication.In the present study, three different tube inlet orifice configurations are evaluated for a helical coiled Once Through Steam Generator. Orifice length is derived for all three configurations based on the orifice pressure drop required for avoiding flow instabilities. Orifice pressure drop required to avoid flow instabilities is estimated as factor k times the sum of two phase pressure drop and super-heating zone pressure drop of the tube side flow, where minimum value of k is taken as 2 (Han et al., 2019; Kang et al., 2007). Various power levels (10%–100%) are considered to obtain the governing length of the orifice. Pressure drop across the orifice over the flow range 10%–100% is estimated theoretically using various correlations available in the literature (Idelchik). Numerical simulations are carried out for all three configurations of the orifice. Flow through the orifice falls in the turbulent regime and hence, three different turbulent models viz. k-ε model, RNG k-ε model and Realizable k-ε model are compared for their capability to predict pressure drop across the orifice. Theoretical and Numerical results are verified with experimental pressure drop measurements over the flow range corresponding to a power range of 10%–100%. The effect of manufacturing tolerances on pressure drop is studied experimentally for all three configurations. Five nos. of each orifice configuration were manufactured and tested experimentally for pressure drop over 10%–100% flow range to see the effect of manufacturing tolerances.It is concluded from the study that irrespective of the orifice configuration, the minimum length required for the orifice is governed by the lowest power operation i.e, the lowest flow operation. Also, a comparison of various turbulence models viz. k-ε model, RNG k-ε model and Realizable k-ε model, reveals that, RNG model is best suited for orifice configurations that utilize sudden expansion and contraction for creating pressure drop. Whereas, all three turbulence models compared in the present study gives similar results for orifice configurations in which pressure drop occurs mainly due to wall friction and gradual but smooth change in flow direction. Orifice configuration-3 which utilizes a helical flow path is finally selected based on the selection criteria stated above.

Experimental observation of lean flammability limits using turbulent jet ignition with auxiliary hydrogen and methane in pre-chamber

The combustion characteristics of CH4-air mixture under the lean-fuel conditions ignited by different methods including SI, unfueled pre-chamber ignition and fueled pre-chamber ignition were investigated experimentally in a constant volume combustion chamber (CVCC) through high-speed schlieren photography. And a self-designed fueled pre-chamber turbulent jet ignition (TJI) combustion system with a single orifice configuration and small volume was employed. Results show that TJI could enhance combustion including the rapid increases of flame tip velocity and flame area growth rate, which also was manifested by increasing peak pressure and shortening time to peak. The pre-chamber ignition fueled with hydrogen can greatly extend the lean flammability limit in the main chamber and reduce the sensitivity of flame development with the excess air coefficient. However, the oscillations in flame propagation and pressure evolution due to the flame-shock interaction were obvious under the pre-chamber fueled with hydrogen. Overall, in the present work, the turbulent flame development in the main chamber depends on the flame consumption velocity in pre-chamber, orifice size of pre-chamber, and the mixture concentration in main chamber. These results are of great help to achieve the highly-efficient combustion and to shorten the combustion duration in practical SI engines.

Mesiobuccal and Palatal Interorifice Distance May Predict the Presence of the Second Mesiobuccal Canal in Maxillary Second Molars with Fused Roots

IntroductionThe aim of this study was to evaluate if the configuration of canal orifices can predict the presence of a second mesiobuccal canal (MB2) in maxillary second molars with fused roots. MethodsMaxillary second molars with fused roots (N = 150) were scanned in a micro–computed tomographic device (pixel size = 9 μm) and evaluated regarding the root fusion type and the incidence of the MB2 canal. The centers of the canal orifices were connected, and the angles formed by the intersection of these lines as well as their distances were measured and statistically compared (1-way analysis of variance). Specimens were then assigned to 2 groups according to the presence (n = 65) or absence (n = 50) of the MB2 canal and compared regarding the angles and interorifice distances using the Welch t test. A binary logistic regression model estimated the association between the interorifice distance, the fusion type, and the presence of the MB2 canal, whereas receiver operating characteristic curve analysis was performed to evaluate the diagnostic abilities of significant variables. The significance level was set at 5%. ResultsThe most common fusion types were 1 and 6, and MB2 canal incidence was 47.3%. No statistical difference was observed in the angles or interorifice distances among teeth with different fusion types (P > .05). Distances from the mesiobuccal (MB) to the distobuccal and palatal (P) canal orifices as well as the MB and P angles were significantly higher in the presence of an MB2 canal (P < .05). A binary logistic regression model revealed that MB-distobuccal and MB-P distances were significant in the presence of an MB2 canal (P < .05). Receiver operating characteristic analysis indicated that MB-P distance had acceptable diagnostic accuracy for the prediction of MB2 canal presence. Sensitivity (specificity) calculated from the MB-P distances of 4.0, 4.5, and 5.0 mm were 89.2% (36.5%), 76.9% (58.4%), and 44.4% (71.4%), respectively. ConclusionsMB-P interorifice distance is a strong predictor of the presence of the MB2 canal in maxillary second molars with fused roots.

Impingement heat transfer on flat and concave surfaces by piston-driven synthetic jet from planar lobed orifice

The heat transfer characteristics of a single synthetic jet (SJ) issuing from planar lobed orifice are investigated experimentally in current study. Two specific planar-lobed orifices (petal-shaped orifice and arch-shaped orifice) and two typical targets (flat target and semi-cylindrical concave target) are taken into consideration. For each lobed orifice, three configurations are included. In the petal-shaped orifices, the lobe numbers are chosen as N=4, 6 and 8 in turns. While in the arch-shaped orifices, the lobe number is fixed as N=6 but the lobe aspect ratios are altered as AR=1, 2 and 3 respectively. All lobed orifices have the same exit area with the baseline round orifice. The experimental tests are performed under a series of operational frequencies (ranging from 10Hz to 25Hz) and dimensionless jet-to-target distances (ranging from 2 to 14 for flat target, and from 6 to 14 for concave target). Under the present conditions, SJ impingement heat transfer enhancement is mostly achieved by the planar lobed orifices when compared to the baseline round orifice, which depends tightly on the lobe shape and target shape. Among current petal-shaped orifices, the N=6 petal-shaped orifice is demonstrated to be a most promising orifice configuration. With regard to current arch-shaped orifices, a moderate lobe aspect ratio is demonstrated to be the superior. When compared to the flat target, SJ impingement heat transfer on the concave target is seriously reduced, regardless of orifice shapes. Interestingly, the relationship of SJ impingement heat transfer on the concave target, between the N=6 petal-shaped orifice and AR=2 arch-shaped orifice, is found contrary to that on the flat target. On the concave target, the N=6 petal-shaped orifice does not show its advantages on SJ heat transfer enhancement as appeared on the flat target. However, the AR=2 arch-shaped orifice still shows its positive role on SJ heat transfer enhancement obviously in comparison to the baseline round orifice.

Synthetic jet actuator with two opposite diaphragms

Abstract The synthetic jet actuators are one of the most investigated types of actuators used in heat transfer and active flow control. The energetic efficiency of actuators is a key parameter determining the possibility of device use. The actuators with two or more diaphragms have higher efficiency than the actuators with only one. The paper presents the investigations of the acoustic synthetic jet actuator with two opposite diaphragms. In the paper, synthetic jet velocity, Reynolds number and the energetic efficiency as a function of oscillating actuator frequency, for a different cavity, orifice configuration and one real input power P 0 = 2 W were studied. The possibility of theoretical calculation of first and second resonance frequency were checked. The coupling ratio for actuators was calculated. The maximum energetic efficiency was η = 8.67% and Reynolds number Re = 8503. The possibility of using the same dependencies and rules during the design of actuators with two opposite diaphragms as in the case of actuators with one diaphragm was demonstrated. The results may be useful in the design of the actuators of the two membranes.

An in vitro investigation into the hemodynamic effects of orifice geometry and position on left ventricular vortex formation and turbulence intensity.

In a healthy human cardiac system, a large asymmetric clockwise vortex present in the left ventricle (LV) efficiently diverts the filling jet from the mitral annulus to the left ventricular outflow track. However, prior clinical studies have shown that artificial mitral valve replacement can affect the formation of physiological vortex, resulting in overall flow instability in the LV. Lately, the findings from several recent hemodynamic studies seem to suggest that the native D-shaped mitral annulus might be a crucial factor in the development of this physiological flow pattern, with its inherent flow stability and formation of coherent structures within the LV. This study aims to investigate the effect of orifice shape and its position with respect to the posterior wall of the ventricle on vortical formation and turbulence intensity in the LV, by utilizing four separate orifice configurations within an in vitro left heart simulator. Stereo particle image velocimetry experiments were then carried out to characterize the downstream flow field of each configuration. Our findings demonstrate that the generation of the physiological left ventricular vortical flow was not solely dependent upon the orifice shape but rather the subsequent jet-wall interaction. The distance of the orifice geometric center from the left ventricular posterior wall plays a significant role in this jet-wall interaction, and thus, vortical flow dynamics.

Three-dimensional vortical structures generated by plasma synthetic jets in crossflow

In the present study, phase-locked tomographic particle image velocimetry measurements are performed to obtain the complex three-dimensional vortex system created by the interaction of plasma synthetic jets with external crossflow. Three orifice configurations (round, transverse slot, and longitudinal slot) are investigated. For the round orifice case, the vortex system consists of a starting vortex ring surrounding the jet head, a hanging vortex pair residing in the two lateral sides of the jet body, several shear layer vortices bridging the two legs of the hanging vortex pair, and a hairpin vortex induced by the low-speed secondary jet. For the slot orifice cases, the above vortex system is also present; nevertheless, the interconnections of the vortices are further intersected by the rib vortices that are branched out of the elongated vortex ring during axis switching. The counter-rotating vortex pair observed in the far field is essentially evolving from the hanging vortex pair in the near field.