Primary Jet Research Articles

Причины свечения аномального вторичного потока в сверхзвуковых кластированных струях, возбужденных высоковольтным электронным пучком

The role of clustered particles in the formation of a secondary flow (“wake”) occuring at the gas expiring into a rarefied medium in condensation modes is established. The “wake” boundaries were found by comparing the spectral and photometric measurements. Possible mechanisms for initiating luminescence in "wake" are considered. The role of energy exchange of clusters with background gas in the afterglow of the "wake" has been found out. The wavelengths and corresponding transitions in the neutral (Ar-I) and once ionized (Ar-II) argon atoms, which determine the anomalous glow, were discovered. The lifetimes in the excited state of particles in the central part and on the periphery of the clustered flow are detected. The effect of condensation on the background gas penetration into the primary traditional supersonic jet and into the “wake” zone is found.

Non-Reacting studies on Transverse Injection Upstream of Aft Wall Angled Cavities

Cavity performance in coaxial supersonic jets is investigated experimentally in a supersonic flow facility. The coaxial jets issued from the supersonic nozzle enter into a supersonic combustor in which the cavities are incorporated. The primary jet is maintained at a Mach of 1.32, while secondary jet is designed for Mach of 1.00, 1.11 and 1.45. The open type cavities are axisymmetric. The primary flow is maintained at a temperature of 1050K and the secondary flow is at atmospheric temperature. Static and stagnation pressures are measured by using a conventional pitot probe to analyze the quantitative mixing performance and total pressure loss. Uniform momentum flux distribution is observed in cavity configurations compared with nocavity. A more uniform mixing, as well as minimum stagnation pressure loss, is observed for cavity configuration - 4, L/D = 1.53, than other cavity configurations

New model for the prediction of the machining depth during milling of 3D woven composite using abrasive waterjet process

The goal is to study the influence of abrasive water jet (AWJ) machining parameters (jet pressure, traverse speed and scan step) on the cutting depth of 3D woven Carbon Fibres Reinforced Polymer (CFRP) composite. The original material linked to this non-conventional milling process has not been treated yet. The depths of cut were measured and characterized as a function of the machining parameters. Finally, two prediction models for the cutting depth are proposed and validated experimentally.An increase in cutting depth with the pressure and a decrease as the traverse speed and/or the scan step increase were observed. The first prediction model, based on the pocket depth measurements, has a mean error of 5%. However, the error increases (up to 23%) when the pocket becomes shallow (lesser than 1 mm). The second prediction model, based on the algebraic sum of elementary passes modelled with Gaussian bells, shows at first a mean error of 12%. A correction was performed depending on the erosion regime piloted by the depth of the elementary trench constitutive of the pocket. This enhancement, performed thanks to the primary jet diameters measurements with high speed camera, has improved the second model with a mean error of 5% (error <16%).

Large scale instabilities in coaxial air-water jets with annular air swirl

The aim of this paper is to characterize large-scale instabilities during the primary breakup process in liquid centered coaxial air-water jets. The interest here is to investigate the role of annular air swirl on such instabilities. A coaxial airblast atomizer that incorporates an axial swirler is considered for this purpose. The atomizer was operated in a wide range of the Weber number, Weg(80–958), momentum flux ratio, M(1–26), and air swirl strength, S(0–1.6). High-speed shadowgraphic images of the primary jet breakup process were recorded. Proper orthogonal decomposition (POD) analysis of the time-resolved images was performed for each operating condition. The 2nd and 3rd POD modes depicted some universal spatial features which refer to large scale instabilities. Three different dominant large scale instabilities were identified, viz., jet flapping, wavy breakup, and explosive breakup, for the entire range of the injector operating condition either in the presence or absence of air swirl. It was found that jet flapping (referred to as the lateral oscillation of the tail end of the jet) is the dominant mode of jet instability for a lower range of M, while explosive jet breakup (referred to as the radial expansion of the jet) governs jet breakup unsteadiness for a higher range of M. The wavy or sinuous mode of breakup is a secondary mechanism relevant under low M conditions. The mechanisms of large scale instabilities and the role of air swirl in that context are explained based on the Fourier analysis of the temporal coefficients of the corresponding POD modes.

Numerical study on Vectoring the primary flows with dilator using microjet actuators

The synthetic flow field of Vectoring control of a primary flows with dilator using microjet actuators was Numerical studied by the overall flow field calculation model-X-L model. The result shows that the primary flows with dilator deflected larger than no one. And the angle of dilator has an optimal value. The reason of primary flows deflected was analyzed. There are three stage sections that the “low pressure closed reticular flow region” results in non-equilibrium of pressure along the primary jet’s orifice; the microjet roll sucked and the primary flow coupled in each other in the near catchment area; the microjet and the primary flow coupled in each other in the far catchment area.

P4725Prognostic relevance of the COAPT inclusion criteria in real-world patients with secondary mitral regurgitation undergoing mitraclip implantation

Abstract Background The recently published Cardiovascular Outcomes Assessment of the mitraclip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation (COAPT) randomized trial has shown a huge benefit in the survival of patients with systolic heart failure and functional mitral regurgitation treated with MitraClip. However, patients in COAPT were highly selected and the clinical course in real-world patients with and without fulfilment of the trial inclusion criteria is unclear. Methods Our study examined the clinical outcome in consecutive patients from our Heart Centre with reduced left-ventricular ejection fraction (EF&lt;50%) undergoing mitraclip for mitral regurgitation of dominant functional etiology by the presence of the inclusion criteria of the COAPT trial (left ventricular ejection fraction &gt;20%, left ventricular end-systolic dimension &lt;70 mm, non-commissural primary jet, estimated pulmonary artery systolic pressure &lt;70 mmHg, mitral valve orifice area &gt;4 cm2, no prior mitral valve leaflet surgery or any currently implanted prosthetic mitral valve or any prior transcatheter mitral valve procedure). The composite endpoint of all-cause mortality or heart failure hospitalization and the endpoint of heart failure hospitalization were analysed. Results Among 123 patients who underwent mitraclip implantation 60.2% fulfilled the inclusion criteria of COAPT. Overall, 54 patients (46.6%) died or were hospitalized for heart failure during a median follow-up time of 19 months. The composite endpoint was significantly less frequent (p=0.01) in patients fulfilling the COAPT selection criteria than in those not fulfilling the criteria, with an estimated 1-year event rate of 24.6% vs 49.1%. Patients with COAPT inclusion criteria had a 49% lower hazard of the composite endpoint (95% CI 12–70%, p=0.015). Heart failure hospitalization was significantly less frequent (p=0.039) in patients fulfilling COAPT selection criteria than in those who did not, with an estimated 1-year event rate of 19% vs. 36.8%. Patients with COAPT inclusion criteria had a 50% lower hazard for heart failure hospitalization (95% CI 1–75%, p=0.046). Of note, the 1-year all-cause mortality in our patients fulfilling COAPT inclusion criteria was lower compared to the renowned COAPT trial (10% vs. 19%). Conclusion In this single center study the outcome of patients with functional mitral regurgitation undergoing mitraclip therapy was significantly worse in patients not fulfilling COAPT inclusion criteria, indicating that these criteria might help identify futility. The remarkable difference in outcome between real-world patients and COAPT trial patients warrants further study to elucidate underlying causes, which might affect the transferability of the COAPT results.

Experiment on of Nozzle Flow with Sudden Expansion at Mach 1.1

This present study discusses the outcome of the experimental investigations, and the efficacy of the tiny jets used to regulate the base pressure as well as the wall pressure in suddenly expanded flow. The control mechanism as tiny jets having a cross-section of 1 mm diameter was employed as the base pressure regulator at the exit periphery of the nozzle. The experiments were carried out to investigate and record the flow field at the rear end of the separated flow region for area ratio 4.84. Four tiny jets were placed at a distance of 6.5 mm away from the primary jet coming from the nozzle exit at ninety degrees apart, and the tiny control jets were flowing at sonic Mach number. The actual Mach number of the main jet was 1.1. The experimentation was accomplished at a different level of expansion (i. e., NPR = 3, 5, 7, 9, and 11) and the L/D ratio considered was from 10 to 1. This study mainly focuses on the development of the flow in the suddenly expanded duct, nature of the flow in the duct, and the impact of the Control on the wall pressure and the magnitude of the pressure along the duct. The wall pressure in the smooth duct is not unfavorably influenced by the control jets.

Spatio-kinematical model of the collimated molecular outflow in the water-fountain nebula IRAS 16342–3814

Context. Water-fountain nebulae are asymptotic giant branch (AGB) and post-AGB objects that exhibit high-velocity outflows traced by water-maser emission. Their study is important for understanding the interaction between collimated jets and the circumstellar material that leads to the formation of bipolar and/or multi-polar morphologies in evolved stars. Aims. The aim of this paper is to describe the three-dimensional morphology and kinematics of the molecular gas of the water-fountain nebula IRAS 16342−3814. Methods. Data was retrieved from the ALMA archive for analysis using a simple spatio-kinematical model. The software SHAPE was employed to construct a three-dimensional, spatio-kinematical model of the molecular gas in IRAS 16342−3814, and to then reproduce the intensity distribution and position-velocity diagram of the CO emission from the ALMA observations to derive the morphology and velocity field of the gas. Data from CO(J = 1 → 0) supported the physical interpretation of the model. Results. A spatio-kinematical model that includes a high-velocity collimated outflow embedded within material expanding at relatively lower velocity reproduces the images and position-velocity diagrams from the observations. The derived morphology is in good agreement with previous results from IR and water-maser emission observations. The high-velocity collimated outflow exhibits deceleration across its length, while the velocity of the surrounding component increases with distance. The morphology of the emitting region, the velocity field, and the mass of the gas as function of velocity are in excellent agreement with the properties predicted for a molecular outflow driven by a jet. The timescale of the molecular outflow is estimated to be ~70–100 yr. The scalar momentum carried by the outflow is much larger than it can be provided by the radiation of the central star. An oscillating pattern was found associated with the high-velocity collimated outflow. The oscillation period of the pattern is T ≈ 60–90 yr and its opening angle is θop ≈ 2°. Conclusions. The CO (J = 3 → 2) emission in IRAS 16342−3814 is interpreted in terms of a jet-driven molecular outflow expanding along an elongated region. The position-velocity diagram and the mass spectrum reveal a feature due to entrained material that is associated with the driving jet. This feature is not seen in other more evolved objects that exhibit more developed bipolar morphologies. It is likely that the jet in those objects has already disappeared since it is expected to last only for a couple hundred years. This strengthens the idea that water fountain nebulae are undergoing a very short transition during which they develop the collimated outflows that shape the circumstellar envelopes. The oscillating pattern seen in the CO high-velocity outflow is interpreted as due to precession with a relatively small opening angle. The precession period is compatible with the period of the corkscrew pattern seen at IR wavelengths. We propose that the high-velocity molecular outflow traces the underlying primary jet that produces such a pattern.

Two-loop massive quark jet functions in SCET

We calculate the O( {alpha}_s^2 ) corrections to the primary massive quark jet functions in Soft-Collinear Effective Theory (SCET). They are an important ingredient in factorized predictions for inclusive jet mass cross sections initiated by massive quarks emerging from a hard interaction with smooth quark mass dependence. Due to the effects coming from the secondary production of massive quark-antiquark pairs there are two options to define the SCET jet function, which we call universal and mass mode jet functions. They are related to whether or not a soft mass mode (zero) bin subtraction is applied for the secondary massive quark contributions and differ in particular concerning the infrared behavior for vanishing quark mass. We advocate that a useful alternative to the common zero-bin subtraction concept is to define the SCET jet functions through subtractions related to collinear-soft matrix elements. This avoids the need to impose additional power counting arguments as required for zero-bin subtractions. We demonstrate how the two SCET jet function definitions may be used in the context of two recently developed factorization approaches to treat secondary massive quark effects. We clarify the relation between these approaches and in which way they are equivalent. Our two-loop calculation involves interesting technical subtleties related to spurious rapidity divergences and infrared regularization in the presence of massive quarks.

Experimental investigation of flow dynamics of sweeping jets impinging upon confined concave surfaces

The flow fields of a sweeping jet impinging on a confined concave wall are experimentally investigated at different Reynolds numbers and surface curvatures by time-resolved particle image velocimetry (TR-PIV). Three Reynolds numbers (Re = 1650, 3300 and 6601) are considered. With the increase of Reynolds number, the profile of jet oscillation changes from a sawtooth wave, to a sinusoidal wave and finally a square wave, due to the intensified intrinsic bi-stability. Then, concave surfaces with three different diameters (R=∞, 20Dh and 10Dh) are placed at a fixed distance of 5.5 Dh (jet hydrodynamic diameter) from the jet throat. The curved shape of the impingement wall has a notable impact on the flow behaviors. In contrast to the case of a flat impingement wall (R=∞), a pair of large trapped vortices is identified on the lateral recirculation regions of the sweeping jet impinging upon the most curved wall (R=10Dh). The strong outer vortices induce a marked enhancement of fluctuating velocity in regions far from the primary jet impact. The flow dynamics associated with the wall of intermediate curvature (R=20Dh) generally show transitional behaviors.

Feasibility Study for Using Jet Fuel in Diesel Engines

We have determined the primary jet fuel performance properties that have the greatest impact on how effectively they can be used in diesel engines, requiring improvement with the help of functional additives. We have studied the effect of a cetane improver additive based on 2-ethylhexyl nitrate and an antiwear additive based on higher carboxylic acids on the performance properties of jet fuels when they are used in diesel engines, and we have optimized their composition. We present the results of a study of the proposed fuel compositions based on jet fuel and functional additives, using laboratory and qualification methods and indicator properties for the D-245.125 engine cycle.

Switching mechanism investigation for the supersonic jet element: Deflection, attachment and adjustment stages

Based on the unsteady viscous flow simulation, the flow characteristics inside the supersonic jet Element have been investigated numerically. The results have revealed that once the specific structures of the supersonic jet element are finalized, even if the boundary conditions remain unchanged, the corresponding internal flow will also shows strong unsteady in a certain range of primary gas source pressure. The instability of the main vortex center is a main reason to make the output thrust of the supersonic jet components fluctuate all the time in the attached wall condition. At the deflection of the jet stage, once the static pressure for the right side of the wedge exceeds the left side, the transverse expansion for the stripping zone near the right output channel entrance can play a significant role in making the primary jet deflect successfully. When the jet starts to attach the wall layer, due to the “Coanda” effect, the jet also can attach the layer successfully even though the corresponding control flow is totally closed. When the jet enters the adjustment stage, the thrust changes process for the left and right outputs will experience two typical stages: adjusting and adjusted stages. The corresponding vortex structures at different switching time together with the force variations etc. inside the jet Element have been obtained computationally and analyzed in details.

An experimental and numerical study of the suppression of jets, counterflow, and backflow in vortex units

AbstractVortex units are commonly considered for various single and multiphase applications due to their process intensification capabilities. The transition from gas‐only flow to gas–solid flow remains largely unexplored nonetheless. During this transition, primary flow phenomenon, jets, and secondary flow phenomena, counterflow and backflow, are substantially reduced, before a rotating solids bed is established. This transitional flow regime is referred to as the vortex suppression regime. In the present work, this flow transition is identified and validated through experimental and computational studies in two vortex units with a scale differing by a factor of 2, using spherical aluminum and alumina particles. This experimental data supports the proposed theoretical particle monolayer solids loading that allows estimation of vortex suppression regime solids capacity for any vortex unit. It is shown that the vortex suppression regime is established at a solids loading theoretically corresponding to a monolayer being formed in the unit for 1g‐Geldart D‐ and 1g‐Geldart B‐type particles. The model closely agrees with experimental vortex suppression range for both aluminum and alumina particles. The model, as well as the experimental data, shows that the flow suppression regime depends on unit dimensions, particle diameter, and particle density but is independent of gas flow rate. This combined study, based on experimental and computational data and on a theoretical model, reveals the vortex suppression to be one of the basic operational parameters to study flow in a vortex unit and that a simple monolayer model allows to estimate the needed solids loading for any vortex device to induce this flow transition.

Large eddy simulation of transverse single/double jet in supersonic crossflow

In this paper, large eddy simulation of transverse sonic single/double hydrogen jets into supersonic Mach 2 crossflow have been carried out to investigate the complex flow structures and the mixing performance. Detailed turbulence characteristics, in terms of the instantaneous and mean flow fields, the vortex structures and their evolutions, the turbulence kinetic energy and the Reynolds shear stress distributions, the maximum hydrogen mass fraction and jet penetration, have been provided. Results of the two-dimensional and three-dimensional streamlines illustrate that the trailing counter-rotating vortex pairs (TCVP), the secondary TCVP of primary jet and the horseshoe vortex can merge and form a new horseshoe vortex. Three counter-rotating vortex pairs (CVP) are formed in the downstream of secondary jet: the CVP-B due to interactions between the supersonic crossflow and secondary jet; the CVP-C due to interactions between the supersonic crossflow, primary and secondary jets; and the CVP-D due to interactions of the supersonic crossflow and primary jet. The presence of primary jet flow alters the Reynolds shear stress distributions after the secondary injection with the influence of these large-scale structures. In addition, the two-stage jet injection system is proved to yield a better mixing performance than the single jet system.

Numerical study on the shock vector control in a rectangular supersonic nozzle

In recent decades, the fluidic thrust vector control technique is one of the core strategies to redirect various aerospace vehicles, such as modern launch rockets, supersonic aircraft, and guided missiles. The fundamental theory of the shock vector control is that the gas is injected into the supersonic part of a conventional convergent–divergent nozzle from the transverse to cause interactions between the shock waves and boundary layers. Then, the deflection of the primary jet can be easily realized by the induced oblique shock waves. It was evident that the shock vector control is a very simple, low weight, low cost, and quick vectoring response technique to gain high thrust vectoring performance. In the present work, computational fluid dynamics studies were performed at different control parameters in a three-dimensional rectangular supersonic nozzle with the slot injector. For the validation of the numerical methodology, computational results were compared with experimental data referred to the NASA Langley Research Center. The static pressure distributions along the upper and lower nozzle surfaces in the symmetry plane were matched with the test data excellently. Numerical simulations were based on the well-assessed shear stress transport k–ω turbulence model. Second-order accuracy was selected to reveal more details of the flow-field as much as possible. Lots of factors were investigated, such as the momentum flux ratio, length-to-width ratio, injection location, and injection angle. The performance variations for different affecting factors were illustrated and some constructive conclusions were obtained to provide the reference for further investigations in fluidic thrust vector control field.

NVST observations of collision-induced apparent fan-shaped jets

ABSTRACT Using high-quality H α observations from the New Vacuum Solar Telescope, we first report apparent fan-shaped jets (AFJs) generated during the interaction between primary fan-shaped jets (FJs) and nearby facula magnetic structure. The primary FJs were intermittently launched from a sunspot penumbra with negative-polarity magnetic fields in active region 12740 on 2019 May 6, accompanied by impulsive brightenings at the base. While the propagating FJ encountered and collided with the negative-polarity magnetic structure of the west facula, the density of jet material was enhanced to the east of the facula. Meanwhile, the jet structures exhibited a deflection towards the north-west at the jet–facula collision location. Then the primary FJ evolved into two parts, with one part being reflected away from the facula and the other part forming an AFJ. Easily distinguished from the primary FJ, the ejecting AFJ was more ordered and had an apparent end at the facula. The AFJ was impulsively accelerated to speeds of 100 km s−1, and reached lengths of up to 40 Mm. The observed AFJ had a similar morphology to the fan-shaped quasi-separatrix layer (QSL) between the penumbra and facula magnetic systems, implying that the material of the AFJ was mainly guided by the fan plane of the QSL. We suggest that the collision does not cause a change in the field-line connectivity and only leads to the redistribution of jet material.

Experimental investigation of different nozzle designs inside active chilled beams

The aim of this study is to improve the performance of active chilled beams (ACB) by varying the nozzles cross section geometry. Most of the common ACB today have circular nozzles for the primary air plenum, as they are easy to produce and ensure a good performance. The amount of induced secondary air and thereby the performance of the system can be increased by improving the properties of the primary air jet. In other research fields like engine jets or air diffusers, different nozzle designs have been developed to enhance the jets mixing. In this study, a generic test bench is built to investigate different nozzle designs for ACB. The flow field is investigated with particle image velocimetry (PIV) which gives detailed information about the jet’s shape. The designed test bench ensures optical access to the flow field while the induced room air is measured via differential pressure methods. The cross-shaped nozzle achieved the best results among the investigated ones and could significantly increase the induced air amount. An elliptic opening also shows promising results but cannot reach the performance of the circular nozzle in this study. A rectangular nozzle opening turns out to be unsuitable in ACB.

The Effect of Dilution Air Jets on Aero-Engine Combustor Performance

Abstract In aero-engine combustor, the primary and secondary dilution air jets play a vital role to achieve efficient combustion and provide a satisfactory temperature profile at the combustor exit. In the current research, seven kinds of three-dome combustor sector associated with different dilution holes arrangements are simulated using Flamelet model. The influences of location, number and diameter of dilution air holes on flow field and performance of combustor are analysed in detail. The results demonstrate that the variation of airflow distribution, while keeping the total admission area constant, impact the combustion efficiency and pattern profile considerably, yet has insignificant effect on the total pressure coefficient. The maximum combustion efficiency and minimum pattern factor can be achieved simultaneously with deliberate dilution jet holes arrangement.

オフィス空間の空調制御に利用可能な室内温度分布の予測モデル式の検討 （第４報）一次噴流モデルによる室内気流場の予測検証及び風量補正モデルの検討

オフィス空間の空調制御に利用可能な室内温度分布の予測モデル式の検討 （第４報）一次噴流モデルによる室内気流場の予測検証及び風量補正モデルの検討

Fluidic injectors for supersonic jet control

An experimental investigation on the mixing capability of a Mach 2.0 jet manipulated based on a convergent injector (CI) and convergent-divergent injector (CDI) is reported in this paper. The injector parameters that influence the core length of the manipulated jet (Lc*), such as the mass flow rate ratio Cm of the minijets to the main jet and the expansion ratio pe/pa (where pe and pa are the nozzle exit and atmospheric pressures, respectively), are examined in detail. The experimental diagnostics include the detailed Pitot pressure measurement along the jet centerline and the shadowgraph visualizations captured in the orthogonal planes of the manipulated jet. Various flow structures have been identified based on the shadowgraph visualization, such as categories I and II corresponding to the off-design and design conditions of the primary jet, respectively. The core length of the manipulated jet exhibits a strong dependence on Cm, pe/pa, and the type of injection (CI or CDI). The jet mixing quantified based on ΔLc* (where ΔLc* is the percentage reduction in core length of the manipulated jet with respect to the natural jet) is maximum at the design condition than the off-design condition implying that the jet manipulation is highly efficient at the design condition.