Lateral Jet Research Articles

Investigation of Significant Parameters during Abrasive Waterjet Turning.

This paper presents an investigation of abrasive waterjet turning (AWJT). The purpose of the article was to investigate significant parameters of the turning process and to evaluate their impact on the turning product. The influence of the traverse speed, the rotational speed, and the relative position of the jet to the specimen (lateral jet shift) were investigated. Based on the previous research done in this field, the multi-pass tangential turning method was selected. Rotational speed does not seem to have a significant impact on the AWJ turning process. However, the relative position of the jet is a key parameter for improving the efficiency of the process. Increasing the lateral jet shift causes the volume of the material removed to increase until the optimal impact angle is reached. These findings need to be extended in order to adjust AWJT. Without these improvements, a comparison of jet to traditional technologies is inappropriate.

GRB jet structure and the jet break

ABSTRACT We investigate the shape of the jet break in within-beam gamma-ray burst (GRB) optical afterglows for various lateral jet structure profiles. We consider cases with and without lateral spreading and a range of inclinations within the jet core half-opening angle, θc. We fit model and observed afterglow light curves with a smoothly-broken power-law function with a free-parameter κ that describes the sharpness of the break. We find that the jet break is sharper (κ is greater) when lateral spreading is included than in the absence of lateral spreading. For profiles with a sharp-edged core, the sharpness parameter has a broad range of 0.1 ≲ κ ≲ 4.6, whereas profiles with a smooth-edged core have a narrower range of 0.1 ≲ κ ≲ 2.2 when models both with and without lateral spreading are included. For sharp-edged jets, the jet break sharpness depends strongly on the inclination of the system within θc, whereas for smooth-edged jets, κ is more strongly dependent on the size of θc. Using a sample of 20 GRBs, we find 9 candidate smooth-edged jet structures and 8 candidate sharp-edged jet structures, while the remaining 3 are consistent with either. The shape of the jet break, as measured by the sharpness parameter κ, can be used as an initial check for the presence of lateral structure in within-beam GRBs where the afterglow is well-sampled at and around the jet-break time.

Fluid-thermal coupled investigation on the combinational spike and opposing/lateral jet in hypersonic flows

The drag reduction and thermal protection mechanism induced by the spike and its combinations with jet strategy is investigated in the current study. A fluid-thermal coupled analysis is carried out to explore the impacts of the jet pressure ratio (PR), the length-to-diameter ratio (L/D) of the spike and the lateral jet location (DL) on the peak pressure and peak heat flux of the blunt head. The obtained results suggest that the combined spike and multi-jet strategy is the most promising technology for the drag and heat reduction. The increases in jet pressure ratios including opposing jet ratio and lateral jet ratio are advantageous and provide the maximum reduction in the drag and heat flux. Specifically, for the cases of PRo = 0.2 and PRo = 0.6, the peak heat fluxes are decreased by about 2.25 kW/m2 and 0.37 kW/m2 respectively after 0.6 s’, and the decrease rate becomes more slowly during the coupling process. Further, the negative thrust produced by the opposing jet plays a key role in the total drag component. For the L/D effect, the peak pressure and drag coefficient decreases when L/D increases. However, it is noteworthy that when L/D = 0.5, the peak heat flux is close to that when L/D = 2, which, is at a relatively low level of 104.83 kW/m2. In addition, the lateral jet location has a decisive influence on the flow structure, drag coefficient and heat flux distribution, and DL = 8 mm gives the minimum drag and heat flux while the peak pressure is the maximum.

Instabilities and transition in cooled wall hypersonic boundary layers

Abstract

Effectiveness of multiple jets for a finned large slenderness ratio missile in supersonic crossflows

The reaction control system with multiple lateral jets shows great advantages in agility and maneuverability for supersonic air vehicles. Interactions among sonic jet plumes, X-shape fins, and supersonic crossflow at Mach 4.5 and Reynolds number 3.8 × 107 are numerically studied considering different number of jets for a large slenderness ratio missile with 7 jet exits. Three-dimensional Reynolds-averaged Navier–Stokes equations closed by Spalart–Allmaras turbulence model for the structured grid are validated and solved. The overall force and moment amplification factors of configurations with and without fins are analyzed and compared. Moreover, the force and moment amplification factors on fins and ratio of force and moment on fins are proposed and discussed to measure the jet effectiveness contributed from fins. The number of jet plumes is under consideration for all cases. Results show that the increment of effectiveness decreases as the number of jets increases for the finned configuration. Fins can significantly improve the jet effectiveness with more than 70% force and 50% moment increment, which shows great advantages to the jet effectiveness as well as the overall aerodynamic performance.

Research on Drag Reduction Mechanism and Optimization Design of Bionic Jet Flow

In the process of sailing, the frictional resistance of underwater objects must be reduced, which is of great significance for improving speed, range and saving energy. Based on the inspiration of the shark breathing process, this paper simplified the water spray process from the external bronchial slit of the shark breathing to the cross-flow lateral jet process. By establishing a numerical model, the influence mechanism of the jet on the flow resistance was studied, and by analyzing different jet velocities, the change of viscous resistance reveals the influence of jet velocity on viscous resistance. The results show that the side jet can reduce the boundary layer on the surface of the object, thereby having a drag reduction effect, and the drag reduction rate can be about 10%. In addition, as the jet velocity increases, the drag reduction effect is enhanced, and at the back of the jet port the vortex is formed, the outlet pressure is reduced, and the drag reduction effect is strengthened. At the same time, the study found that the arc-shaped jet port is more conducive to the reduction of resistance.

Study of counteracting the secondary flow in open channel bends

In terms of the importance of reducing the influences of curvature induced circulation secondary flow, several counteracting techniques/measures have been studied. Although the previous techniques have obtained good results yet, they involve fixed and permanent construction works in the channel. Most of the techniques have a negative impact on navigation, and may be damaged under extreme flow conditions. Therefore, the use of new technique has become very significant and must be studied. The aim of this paper to study a new technique as an indirect tool to counteract the impact of the secondary flow on the banks and bed at channel bends by re-distribution of the main flow velocity in the curved section through water jets. In a previous experiment, air bubbles are induced as a bubble screen (air media) with an appropriate velocity, through a porous tube placed near the outer bank in the sharply open channel bend 193°. In this paper, one of the previous experiments is modeled with the same shape and conditions, however, the induced air bubbles from the porous tube in the experiment are replaced by a water screen to act as a source of momentum. A numerical model FLUENT was implemented and a realizable K-ε turbulent model was used to scrutinize and predict the velocity pattern in the channel bend. The impact of the change in lateral water jets flow from the porous tube was also investigated and results presented and compared. The results revealed that the water screen technique contributes in reducing the downward movement of the secondary circulation, dragging the flow upward, leading to the distribution of the secondary circulation, and shifting the core of maximum downstream velocities away from the outer bank towards the inner bank at the junction of generated circulation. The results also showed that the water screen is able to counteract the effect of the main flow circulation cells provided that this secondary flow is not less than 20% of the main flow and the corresponding velocity is also not less than 40% of the main flow velocity.

Curved surface effect on high-speed droplet impingement

Abstract

Flow and mixing characteristics of dual parallel plane jets subject to acoustic excitation

The effects of jet pulsation intensity and excitation Strouhal number on the flow and dispersion characteristics of dual parallel plane jets at a low Reynolds number of 200 were experimentally studied so that the transition from laminar to turbulence was focused. A hot-wire anemometer was used to record the jet velocities. The flow patterns were obtained using the laser-light sheet assisted smoke flow visualization technique. Jet spread widths were derived from the long-exposure images using the binary edge detection method. The jet fluid dispersion characteristics were examined using the tracer-gas concentration detection technique. Four characteristic flow modes (discrete coherent vortices, contiguous coherent vortices, early vortex breakup, and lateral dispersion) were identified in the domain of the jet pulsation intensity and excitation Strouhal number. At small jet pulsation intensities, discrete and contiguous coherent vortices appeared at low and high excitation Strouhal numbers, respectively. The vortices appearing in the jet shear layers broke up slowly and caused small jet expansions and turbulent intensities, thus inducing a low efficiency of jet fluid dispersion. The early vortex breakup mode was induced by the low-frequency back-and-forth flow motions in the near region at large jet pulsation intensities and low excitation Strouhal numbers. Large turbulence fluctuations caused by the early vortex breakup increased the jet dispersion significantly. At large jet pulsation intensities and excitation Strouhal numbers, high-frequency back-and-forth flow motions in the region near the jet exits significantly reduced the time-averaged axial momentum and induced large lateral jet expansion and jet fluid dispersions.

Numerical investigation of vented plume into a supersonic flow in the early stage of rocket hot separation

In the early stage of rocket hot separation, the vented plume from separation gap interacts with the supersonic incoming flow, causing lateral interference which affects separation safety and flight stability. In this work, steady interstage interference flow fields of a two-stage rocket in different incoming flow conditions (Mach number from 2.5 to 5.5, angle of attack from 0° to 6°, flight altitude from 16 Km to 24 Km) are numerically studied by the compressible Reynolds Averaged Navier-Stokes equations with SST turbulence model. An annular lateral jet is used to simulate the vented plume near the separation gap. Firstly, the interference flow fields with and without angle of attack are analyzed in detail to illustrate the interference mechanism of lateral jet. Then, the effects of flight altitude, jet total pressure, separation distance and free-stream Mach number on lateral jet interaction are investigated. With the increase of flight altitude, jet total pressure and separation distance, the upstream separation length and the pressure peak increase, and the peak position moves upstream. Nevertheless, with the increase of free-stream Mach number, the upstream separation length is shortened, the pressure peak raises and the peak position shifts to the downstream. Besides, a combined parameter named momentum ratio is introduced to involve various factors, and the upstream separation length increases linearly with the momentum ratio when the momentum ratio is between 0.03 and 0.173. Finally, the influences of angle of attack on the disturbing force and moment of the upper stage are discussed. Numerical results indicate that the direction of the disturbing force is downward and the magnitude first rises and then falls with the angle of attack. The disturbing moment makes the upper stage have a tendency of subduction and increases with the angle of attack.

Assessment on jet direction effect on drag and heat reduction efficiency for hypersonic vehicles

Introducing jet for drag reduction and thermal protection in hypersonic flows has attained worldwide attentions due to its giant potential, and this paper focused on the drag and heat reduction efficiency of unit mass flow rate for different jet directions in hypersonic flows. The developed code employed conjugate heat transfer approach to solve unsteady Reynolds-averaged Navier-Stokes equations and Fourier's heat conduction equation simultaneously, and then it was thoroughly validated by two classical experiments. Based on that, the flow field characteristics induced by different jet directions under the constant mass flow rate of jet were numerically investigated. Besides, two parameters were introduced to quantitatively evaluate the drag and heat reduction efficiency of different jet directions. The obtained results show that though the total mass flow rate of jet is constant, jet direction still has a decisive influence in manipulating the flow structures, and the rear jet would result in more complicated shock waves due to the interaction between the rear jet flow and spike. The force produced by the jet is the key role in determining the total drag, and the variation of pressure distribution along the blunt body is not the direct presentation of drag reduction performance. The opposing jet has the highest drag reduction efficiency, and lateral jet has the highest heat flux reduction. However, compared with the lateral and rear jets, the opposing jet has better thermal protection performance from the overall perspective as it can also protect the aerodome head from severe aerodynamic heating.

Numerical Investigation of Supersonic Lateral Jet Interaction for Subsonic Projectiles with Different Fins at Large Angle of Attack

Detached Eddy Simulation is used to study the interaction flowfields of a supersonic lateral jet penetrating into the crossflow of projectiles with cruciform or X-type fin configurations at $${\text{Ma}} = 0.3$$ and $$\alpha = 0^\circ ,30^\circ \sim 60^\circ$$ . For $$\alpha = 0^\circ$$ , typical flow structures such as barrel shock, Mach disk and counter-rotating vortex pair(CVP) induced from the jet orifice are observed. Asymmetrical flowfields downstream of the jet for $$\alpha = 30^\circ$$ are analyzed, as well as the pressure distribution on the surfaces of all the projectiles. The reason why the CVP mentioned above disappears in this condition is also proposed. The variations of the normal forces acting on these projectiles are pointed out. The investigations into the amplification factor and the control efficiency of the jet force show that X-type fin configuration is more beneficial to maintain attitude for projectiles at large angle of attack.

Impact of column geometry and internals on gas and particle flows in a fluidized bed with downward solids circulation: Effect of lateral injection profile and baffles

This paper investigates how solids flow in a circulating fluidized bed can be modified by adding baffles and modifying gas injection locations, and how these changes suggest strategies for a reduction of liquid carryunder in the stripper in Fluid Cokers™. A Computer-Aided Radioactive Particle Tracking (CARPT) method was used with a pilot unit operated at room temperature with the same flux of recirculating coke particles as in the commercial unit. The lateral bitumen injections, and their impact on superficial gas velocity were simulated with 5 banks of 8 lateral gas injectors. In cokers, wet agglomerates that trapped injected bitumen carry unreacted liquid to the stripper. Radioactive simulated agglomerates were tracked to obtain formation-to-stripper time distribution profiles, for each lateral injection jet. Two methods were investigated to reduce liquid carryunder: the addition of a ring baffle and redistribution of liquid between banks. Experiments showed that carryunder can be reduced by either redirecting the bitumen feed from the lowest injection bank to higher banks, or adding a ring baffle with flux tubes in between the lowest and second-lowest injection banks. Combining both methods does not provide additional improvement.

Active Flow Control on a Square-Back Road Vehicle

An experimental investigation focused on the manipulation of the wake generated by a square back car model is presented. Four continuously-blowing rectangular slot jets were mounted on the rear face of a 1:10 commercial van model. Load cell measurements evidence drag reduction for different forcing configurations, reaching a maximum of 12% for lateral and bottom jets blowing. The spectral analysis of the pressure fluctuations evidence, for all forced cases, an energy attenuation with respect to the natural case, especially close to the shedding frequency. An energy budget highlighted the most efficient forcing configurations accounting for both the drag reduction and the power required to feed the blowing system. Two main configurations are considered: the maximum drag reduction and the best compromise, yielding 5% drag reduction and a convenient energy balance. Particle Image Velocimetry (pPIV) and stereoscopic PIV (sPIV) experiments were performed allowing the three-dimensional reconstruction of the wake in the three considered configurations. Consistently with static and fluctuating pressure measurements, sPIV results reveal a dramatic change in the wake structure when the jets blow in the maximum drag reduction configuration. Conversely, the best compromise configuration reveals a wake structure similar to the natural one.

Visualization of asymmetric separation induced by lateral jet interaction on a slender body in supersonic flow

The lateral jet interaction on a slender body in supersonic flow was investigated by numerical simulation. The spatial and surface flow characteristics induced by jet interaction were shown. As a result, when the lateral jet is not in the longitudinal symmetry plane, the jet interaction causes asymmetric separation flow of surface and space, and destroys the pressure distributions of the slender body. With different angle of attack and circumferential positions of jet, the flow characteristic of the after body for jet in asymmetry plane changes greatly. The results with and without jet interaction also show that the far-field interaction played a major role in the lateral jet interaction.

Influences of lateral jet location and its number on the drag reduction of a blunted body in supersonic flows

ABSTRACTThe analysis of the aerodynamic environment of the re-entry vehicle attaches great importance to the design of the novel drag reduction strategies, and the combinational spike and jet concept has shown promising application for the drag reduction in supersonic flows. In this paper, the drag force reduction mechanism induced by the combinational spike and lateral jet concept with the freestream Mach number being 5.9332 has been investigated numerically by means of the two-dimensional axisymmetric Navier-Stokes equations coupled with the shear stress transport (SST) k-ω turbulence model, and the effects of the lateral jet location and its number on the drag reduction of the blunt body have been evaluated. The obtained results show that the drag force of the blunt body can be reduced more profoundly when employing the dual lateral jets, and its maximum percentage is 38.81%, with the locations of the first and second lateral jets arranged suitably. The interaction between the leading shock wave and the first lateral jet has a great impact on the drag force reduction. The drag force reduction is more evident when the interaction is stronger. Due to the inclusion of the lateral jet, the pressure intensity at the reattachment point of the blunt body decreases sharply, as well as the temperature near the walls of the spike and the blunt body, and this implies that the multi-lateral jet is beneficial for the drag reduction.

Active flow control by a novel combinational active thermal protection for hypersonic vehicles

This paper studies the mechanism of combinational active thermal protection system (CA-TPS) of the hypersonic vehicles by numerical method. Unlike the traditional configuration, the nozzle is fixed on the spike, and the directions of lateral jet and hypersonic free stream are perpendicular to each other. The CA-TPS has significantly weaker reattachment shock wave than traditional spiked blunt body. Furthermore, the low temperature gas ejected from the nozzle flows downstream to reduce the aeroheating directly. For the blunt body, the peak and total heat fluxes of CA-TPS are 37.34% and 23.97% lower than that of traditional spiked blunt body, respectively. In addition, this paper conducts the analysis of influencing factors of the CA-TPS. As the total-pressure-ratio of nozzle and the length of spike increase, the reattachment shock wave intensity gradually weakens, and more low temperature gas can be ejected to increase the thermal protection efficiency of the CA-TPS. As the nozzle moves downstream, the reattachment shock wave intensity gradually increases, thus reducing the thermal protection efficiency. The effects of the above influencing factors on the flow field and change rate of thermal protection efficiency of CA-TPS are also studied in this paper.

Investigation of flight dynamics of an axisymmetric vehicle with ejection of a lateral transverse jet

Results on flight dynamics of an axisymmetric vehicle with a control action in the form of gas jet ejection are reported. The differences in the flight trajectories with and without allowance for the pressure redistribution over the vehicle surface due to transverse gas jet ejection are considered and analyzed. Targeted software is developed on the basis of the equations of motion of a material point in space and rotation of the flying vehicle around its center of mass. The influence of the pressure redistribution over the axisymmetric vehicle surface owing to ejection of a lateral transverse gas jet on the flight trajectory and on the rate of vehicle deviation in terms of the yaw angle is demonstrated.

P224 Valvuloplasty treatment and three-dimensional analysis for isolated cleft of the anterior mitral valve leaflet: a case report

Abstract Introduction: Isolated cleft of the anterior mitral valve leaflet is a very rare congenital disease and a cause of mitral regurgitation not associated with atrioventricular septal defect. In this case, we report our experience in valvuloplasty treatment for mitral regurgitation with this rare aetiology. Case description 23-year-old Russian women. Although cardiac murmur was pointed out in her childhood and she was diagnosed as mitral regurgitation, she refused treatment. After getting married with a Japanese man and moving to Japan, her symptoms had worsened and she visited our hospital for treatment. Preoperative transthoracic echocardiography (TTE) had indicated the regurgitation from the central part of the mitral valve. Preoperative transoesophageal echocardiography (TOE) had pointed out the isolated cleft of the anterior mitral valve. Surgical mitral valvuloplasty was scheduled, and the TOE after anaesthetic induction showed the isolated cleft of the anterior mitral valve the same as in the preoperative period and pointed out the posterior leaflet billowing. The operative finding was also similar to TOE: the largely bisected central anterior mitral valve and billowing, P2 billowing, shortening of P1 and P3, P2-3 cleft. There were no chords at the anterior cleft. The valvuloplasty was performed including five-time pump runs in total: 1) Continuous suture for the anterior cleft and ring annuloplasty were performed, and the regurgitation was seemed to be almost controlled at the water-leak test and the ink test; 2) Artificial chordae and leaflet plications were added to residual regurgitation from the posterior region; 3)The residual regurgitation was controlled to Mild but it became a lateral jet toward the ring; 4)Mild remnant flow was pointed out: the regurgitation seemed to be from the posterior cleft, where immediately below the ring suture; 5) Pericardium patch was added and the remnant flow was almost eliminated. The pump was weaned and the operation was finished without any problems. Discussion The cause of difficulty in this valvuloplasty was thought to be caused by the difficulty in evaluating the mitral valve morphology. It was evident that the anterior leaflet of the mitral valve was largely bisected. However, it was difficult to evaluate the coaptation line and area due to the absence of chordal cords in the anterior cleft and the billowing or shortening of the posterior leaflet. Although preoperative three-dimensional analysis helped evaluating the isolated cleft and the regurgitation was almost controlled in the evaluation in the operation field, nevertheless, a residual regurgitation occurred and indicated in the TOE after re-beating. Conclusion It is important and necessary to use fine evaluation of coaptation is needed in valvuloplasty for isolated cleft of the anterior mitral valve leaflet; not only apply three-dimensional analysis but also apply two-dimensional echocardiogram. Abstract P224 Figure.

Eksperimentalno i numeričko istraživanje uticaja rada sistema upravljanja vektorom potiska na aerodinamičke karakteristike raketa simulacijom hladnim i toplim mlazom

The flow field phenomena that occur as a result of thrust vector control (TVC) system activity on a missile with lateral jets are very complex and influence all other components of the missile. Influence is more significant when TVC is generating commands, when jets are asymmetrically directed. The main goal of these study was to determine the influence of of the hot rocket motor's combustion products on the basis of the CFD model proven with the cold-jet simulation. Based on obtained experimental aerodynamic coefficients for the cold-jet simulation the preliminary aerodynamic CFD model was designed. Three-dimensional Reynolds averaged Navier-Stokes numerical aerodynamic and hot-jet simulations were carried out to predict the aerodynamic loads of the missile based on the finite volume method. The study resulted in the definition of a methodology for the investigation of the jet reaction effects in a wind tunnel. A method for determining of the TVC system interference on the aerodynamic characteristics, as a basic prerequisite for structural, stability and performance analysis, was proposed. Mutual verification and validation process was carried out through experiment and proper application of the commercial CFD software code for calculation aerodynamic effects of the hot gases lateral jets on the performance of a guided missile. Experimental and computational results of the pitching moment coefficients are presented and agreed well with.