Deflection Angle Of Jet Research Articles

Experimental investigation on plasma jet deflection with magnetic fluid control based on PIV measurement

This paper is devoted to experimentally investigating the influence of magnetic field intensity and gas temperature on the plasma jet deflection controlled by magneto hydrodynamics. The catalytic ionization seed CS2CO3 is injected into combustion gas by artificial forced ionization to obtain plasma fluid on a high-temperature magnetic fluid experimental platform. The plasma jet was deflected under the effect of an external magnetic field, forming a thrust-vector effect. Magnesium oxide was selected as a tracer particle, and a two-dimensional image of the jet flow field was collected using the particle image velocimetry (PIV) measurement method. Through image processing and velocity vector analysis of the flow field, the value of the jet deflection angle was obtained quantitatively to evaluate the thrust-vector effect. The variation of the jet deflection angle with the magnetic field intensity and gas temperature was studied under different experimental conditions. Experimental results show that the jet deflection angle increased gradually with a rise in gas temperature and then increased substantially when the gas temperature exceeded 2300 K. The jet deflection angle also increased with an increase in magnetic induction intensity. Experiments demonstrate it is feasible to use PIV test technology to study the thrust vector under magnetic control conditions.

Numerical simulation of gas jet in liquid crossflow with high mean jet to crossflow velocity ratio

A jet in crossflow (JiCF) is a type of flow found in several important industrial applications. A gas jet in liquid crossflow represents one of the possible configurations for which there are fewer published studies than for other types of JiCF. The aim of this paper was to determine the equations for the gas jet trajectory and deflection angle via numerical experiments.A three-dimensional numerical simulation of a turbulent two-phase time-dependent flow was conducted with OpenFOAM to obtain the necessary data. Following computational fluid dynamics, the numerical model was validated against experimental data. The agreement between the calculated and measured results was good.The numerical simulation results demonstrated that the jet centerline trajectory could be described by a power regression curve whose coefficient and exponent depended on the liquid Reynolds number. A similar correlation, but with a constant coefficient and exponent, was obtained for the jet deflection angle. Both proposed correlations were valid for a wide range of liquid Reynold numbers, constant high mean jet-to-crossflow velocity ratios, and low jet-to-crossflow density ratios.

Control of self-sustained jet oscillations in 3D thin rectangular cavity

The aim of this work is the control of an oscillatory jet submerged in a 3D thin rectangular cavity, with two opposite injections added on its thinnest sidewalls at the same height, perpendicular and above the jet exit. This type of control is required when the characteristics of the main jet (Reynolds number, nozzle size) are not modifiable. Due to Coanda effect, the oscillations of the main jet occur in the widest plane of the cavity, and depend on the mass flow of two injections. Unsteady, 3D problem is solved by finite volume method using URANS modeling. The validation confirms that second order models predict more accurately this flow configuration than first order models. Two behaviors of time average of flow fields corresponding for two ranges of β are detected. When 0≤β<25.51%, the main jet effect decreases to reach the case without lateral injections (β=0). Similarly for 25.51≤β≤50.67%, the main jet effect diminishes for higher value of β. Thus, β=25.51% is a threshold value for this type of flow configuration. Moreover, for β=25.51% the minimum values for the kinetic energy, main jet deflection angle and oscillations frequency are reached. Furthermore, the deflection angle reaches its maximum value for β=12.90% and the best deflections are recommended for β<25.51%.

Numerical modeling of coanda effect in a novel propulsive system

Coanda effect (adhesion of jet flow over curved surface) is fundamental characteristics of jet flow. In the present paper, we carried out numerical simulations to investigate Coanda flow over a curved surface and its application in a newly proposed Propulsive system “A.C.H.E.O.N” (Aerial Coanda High Efficiency Orienting jet Nozzle) which supports thrust vectoring. The ACHEON system is presently being proposed for propelling a new V/STOL airplane in European Union. This system is based on cumulative effects of three physical effects such as (1) High speed jet mixing speeds (2) Coanda effect control by electrostatic fields (3) Coanda effect adhesion of an high speed jet to a convex surface. The performance of this nozzle can be enhanced by increasing the jet deflection angle of synthetic jet over the Coanda surface. This newly proposed nozzle has wide range of applications. It can be used in industrial sector such as plasma spray gun and for direct injection in combustion chamber to enhance the efficiency of the combustion chamber. Also, we studied the effect of Dielectric barrier discharge (DBD) plasma actuators on A.C.H.E.O.N system. Dielectric barrier discharge (DBD) plasma actuators are active control devices for controlling boundary layer and to delay the flow separation over any convex surfaces. Computations were performed under subsonic condition. Two dimensional CFD calculations were carried out using Reynolds averaged Navier stokes equations (RANS). A numerical method based on finite volume formulation (FVM) was used. SST k-ω model was considered to model turbulent flow inside nozzle. DBD model was used to model the plasma. Moreover, a body force treatment was devised to model the effect of plasma and its coupling with the fluid. This preliminary result shows that, the presence of plasma near Coanda surface accelerates the flow and delays the separation and enhances the efficiency of the nozzle.

Experimental investigation on a vectorized aerodynamic dielectric barrier discharge plasma actuator array

The Electro-Hydro-Dynamics (EHD) interaction, induced in atmospheric pressure still air by a surface dielectric barrier discharge (DBD) actuator, had been experimentally studied. A plasma aerodynamic actuator array, able to produce a vectorized jet, with the induced airflow oriented toward the desired direction, had been developed. The array was constituted by a sequence of single surface DBD actuators with kapton as dielectric material. An ac voltage in the range of 0–6 kV peak at 15 kHz had been used. The vectorization had been obtained by feeding the upper electrodes with different voltages and by varying the electrical connections. The lower electrodes had been connected either to ground or to the high voltage source, to produce the desired jet orientation and to avoid plasma formation acting in an undesired direction. Voltage and current measurements had been carried out to evaluate waveforms and to estimate the active power delivered to the discharge. Schlieren imaging allowed to visualize the induced jet and to estimate its orientation. Pitot measurements had been performed to obtain velocity profiles for all jet configurations. A proportional relation between the jet deflection angle and the applied voltage had been found. Moreover, a linear relation had been obtained between the maximum speed in the jet direction and the applied voltage. The active power of the discharge is approximated by both a power law function and an exponential function of the applied voltage.

Fluidic Thrust Vector Control of Supersonic Jet Using Coflow Injection

The purpose of this research is to investigate the operation condition of fluidic thrust vector using injection of the control flow tangential to the main jet direction; co-flow injection. The physical model of concern includes a chamber and a supersonic nozzle for supersonic main jet injection, and two chambers with slots for control flow injection. Steadystate numerical and experimental studies were conducted to investigate operating parameters; detailed flow structures, jet deflection angles, and shock effects were observed near the nozzle exit. An unsteady numerical calculation was conducted to analyze the dynamic characteristics of fluidic control of jet vectoring up- and downward from the nozzle axis, so that the response time of jet deflection to control flow injection and the pressure dispersion on the nozzle wall were investigated. Internal nozzle performance was predicted for total pressure range of the jet from 300 kPa to 1000 kPa to the control flow pressure from 120 to 200 kPa. To take into account the important features of high-speed flows, including shock-boundary layer interactions, a low Reynolds number k-e turbulence model with compressible-dissipation and pressure-dilatation effects was applied.

Computational analysis of the aerodynamic performance of a jet-flap airfoil in transonic flow

The needed shift in next generation aircraft design is expected to bring novel concepts for civil aviation as the jet-flap wing. The aircraft efficiency improvements with the jet-flap wing directs its use for future aircraft designs reinforced by the tendency for more synergistic systems as active flow control, boundary layer ingestion and distributed propulsion, making the jet-flap wing a very suitable option for the latter concept. The analysis carried out in this paper is aimed at the application of the jet-flap wing concept for manoeuvrability and cruise efficiency improvement of an airliner. A 2D computational model of a jet-flapped transonic airfoil is developed in order to assess the jet-flap wing technology for a commercial aircraft at cruise conditions. This paper provides an insight into the parameters that affect the performance of a jet-flap under various flight conditions. To do this, a general parametrical analysis is performed, studying numerically the influences of main flow parameters like Mach number, Reynolds number, angle of attack, jet deflection angle and jet thickness. Changes in pressure distribution and flow circulation around the airfoil yield strong modifications in lift and drag due to jet angle variation. Improvements are encountered in the performance of an airfoil with a jet-flap system compared with a standard airfoil with no jet. Enhancements in lift and reduction in drag, as well as an increase of the lift-to-drag ratio is possible with a proper combination of the jet deflection and the angle of attack of the airfoil. In summary, this paper shows the conditions under which the benefits of the jet-flapped wing, for lift enhancement and manoeuvrability as an active flow control are promising.

Parallel CFD simulation of flow in a 3D model of vibrating human vocal folds

Accurate computation of highly unsteady and massively separated airflow in human vocal folds during phonation, which is fundamental for the understanding and modeling of the aeroacoustic processes involved in human voice production, requires CFD simulations on large 3D dynamic meshes. This work presents a 3D model of flow past vibrating vocal folds solved by cell-centered finite volume method, verification of the solver on a benchmark cylinder cross-flow problem, grid dependence study and parallel scalability results obtained on a heterogeneous Linux computational cluster with 12 Intel Xeon dual-processor dual-core and 17 AMD Opteron dual-processor single-core nodes. Transient computations on dynamic meshes with up to 3.2M elements were performed on two geometries modeling convergent and divergent glottis with an angle of 20 degrees. In the results, the jet deflection angle, flow rate, glottal velocity and pressure, drag and lift force and jet contours (including phase-averaged data) are compared for these two configurations.

Simulation investigation on fluid characteristics of jet pipe water hydraulic servo valve based on CFD

Simulation investigation on fluid characteristics of the water hydraulic jet pipe servo valve (WHJPSV) is con- ducted through a commercial computational fluid dynamics (CFD) software package FLUENT. In particular, the factors to fluid characteristics of WHJPSV are addressed, which include diameter combination of jet pipe and receiver pipe, jet pipe nozzle clearance, angle between two jet receiver pipes and deflection angle of the jet pipe. It is concluded from the results that: (i) Structural parameters have great influences on fluid characteristics of WHJPSV, when d1 = d2 = 0.3 mm, α =4 5 ◦ , b = 0.5 mm, and the simulation exhibits better fluid characteristics; (ii) The magnitude of the recovery pressure and flow velocity increase almost linearly with the deflection angle of jet pipe. The research work in this paper is important for deter- mining and optimizing the structural parameters of the jet pipe and jet receiver. The relevant conclusions could be extended to the study of other water hydraulic servo control components.

동축류 이차유동 분사를 이용한 초음속 과팽창 제트유동의 유체역학적 추력방향제어 작동특성 연구

본 연구는 주유동의 흐름과 동일한 방향으로 2차 유동을 분사하여 주유동의 방향을 제어하는, 동축류 유체역학적 추력방향제어기법에 관한 연구이다. 이는 유체역학 특징인 코안다 효과를 이용하는 기술이다. 주유동의 전압력은 설계노즐의 과팽창 조건인 300~790 kPa 이며 이차유동의 제어유동압력( 120~200 kPa )에 따른 제트편향각, 세부유동특성, 제어노즐 후방에서의 충격파에 따른 추력편향특성에 대하여 수치적, 실험적 연구를 수행하였다. 이를 바탕으로 초음속 제트유동의 방향을 변화시킬 수 있는 제어유동의 작동한계(0.15 < PR < 0.4)를 도출하였다. The purpose of this research is to investigate the operation characteristics of fluidic thrust vector control using injection of the control flow parallel to the main jet direction; Co-flow injection. The technique bases on the Coanda effect of flow. Both numerical and experimental studies were conducted to investigate operation parameters; flow structure, the jet deflection angle, and shock effects near the nozzle exit. While the total pressure of main jet is the range of 300 to 790 kPa, the total pressure of control flow varies from 120 to 200 kPa. The jet deflection angle and thrust coefficient have linear relation with the pressure ratio(PR) of main jet to control flow in 0.15 < PR < 0.4 but show their limit above PR = 0.4.

Propulsion and aerodynamic performance evaluation of jet-wing distributed propulsion

Distributed propulsion is the idea of redistributing the thrust across the drag producing elements of a vehicle. Our configuration has a modest number of engines with part of the exhaust flow vented from thick trailing edges of the wings to cancel the local profile drag and the rest of the exhaust flow providing thrust to cancel the induced drag and drag of the fuselage and tails. CFD studies were performed on two-dimensional wing sections in transonic, viscous flow to (1) investigate the effect of jet-wing on propulsion efficiency and the flow field (2) determine design changes for achieving efficient distributed propulsion, and (3) investigate the effect of jet-flaps with small jet deflection angles on aerodynamic parameters. The jet-wing distributed propulsion can give propulsive efficiencies on the order of turbofan engine aircraft and if the trailing edge of a conventional Outboard airfoil is expanded, efficiency can be increased by 7.5%. An increase in propulsion efficiency was achieved without expanding the trailing edge for a thicker Inboard airfoil. The results of the Outboard airfoil jet-flap cases support the idea of using deflected exhaust jets from trailing edges as control surfaces.

Hemodynamics of the Mitral Valve Under Edge-to-Edge Repair: An In Vitro Steady Flow Study

Edge-to-edge repair (ETER) is a mitral valve repair technique that restores valvular competence by suturing together the free edges of two leaflets. This repair technique alters mitral valve inflow and thus left ventricle hemodynamics during diastole. Our objective was to investigate fluid mechanics immediately downstream of the mitral valve under ETER during diastole. Fresh porcine mitral valves of the annulus size M32 with chordae removed were installed into a steady flow loop simulating a peak diastolic inflow through the mitral valve. Digital particle image velocimetry was used to measure the velocity field immediately downstream of the mitral valve under normal and ETER conditions. First, to study the suture length effect, suture was applied in the central position of the leaflet edge with suture lengths of 3 mm, 6 mm, and 9 mm, respectively. Then, 3 mm suture was set in the central, lateral, and commissural positions of the leaflet edge to study the suture position effect. Flow rate was 15 l/min. Velocity, Reynolds shear stress (RSS), and effective orifice area were assessed. A total of five mitral valves were tested. The normal mitral valve without the ETER had one jet downstream of the valve, but the mitral valve with the central or lateral sutures under the ETER had two jets downstream of the valve with a recirculation region downstream of the suture. The maximum velocity, the maximum RSS in the jets, the pressure drop across the mitral valve, and the jet deflection angle increased with the increase in suture length in the central position. When the suture position effect was investigated with the 3 mm suture, the maximum velocity, the maximum RSS, and the pressure drop across the valve in the central suture position were greater than those of the lateral and the commissural suture positions. The lateral suture demonstrated major and minor jets with the greater maximum velocity and maximum RSS in the major jet. When the suture was in the commissural position, the flow field downstream of the mitral valve was similar to that of the normal mitral valve without the ETER. The effective orifice area was smallest when the suture was applied in the central position as compared with other suture positions. Both suture length and position have an important impact on fluid mechanics downstream of the mitral valve under the ETER in terms of flow pattern, maximum velocity, and RSS distribution. The altered hemodynamics of the mitral valve and thus of the left ventricle by the ETER may change mitral valve and left ventricle function.

Control of an Oscillatory Rectangular Cavity Jet Flow by Secondary Injection

A method for controlling the position of an oscillatory cavity jet flow is demonstrated. The method involves secondary injection of a lower mass flow control jet into the cross-flow region of the primary jet. The primary jet in this case is a turbulent jet (Re = 55 000) which when injected into the rectangular cavity with no secondary control, attains a stable oscillation with a characteristic Strouhal number of S t,w = 0.013. The injection control method is investigated using a combined experimental and numerical approach with a water model test rig and a 2D and 3D computational fluid dynamics (CFD) model. Based on previous work, a baseline cavity, with a depth to width ratio of H/W = 0.16 and entry nozzle submergence of S/W = 0.38, is used to study the effect of secondary jet injection parameters on primary jet deflection angle (δ) as a function of momentum ratio (β) and injection position (Y i ). Results have shown primary jet deflection angles (6) of up to 15° for a momentum ratio (β) of 20% can be achieved for a secondary jet injection position of Y 1 /W = 0.12.

Closed-Loop Vectoring Control of a Turbulent Jet Using Periodic Excitation

Closed-loop control strategies were studied experimentally at low Reynolds and incompressible Mach numbers using periodic excitation to vector a turbulent jet. Vectoring was achieved by attaching a short, wide-angle diffuser at the jet exit and introducing periodic excitation from a slot covering one quadrant of the circumference of the round turbulent jet. Closed-loop control methods were applied to transition quickly and smoothly between different jet deflection angles. The frequency response of the zero-mass-flux piezoelectric actuator was flat to about 0.5 kHz, but the jet responds up to 30-50 Hz only. This is still an order of magnitude faster than conventional thrust vectoring mechanism. System identification procedures were applied to approximate the system's transfer function. A linear controller was designed that enabled fast and smooth transitions between stationary deflection angles and maintained desired jet vectoring angles under varying system conditions. The linear controller was tested over the entire range of available deflection angles, and its performance is evaluated and discussed.

Parsec-Scale Radio Structure and Broad Optical Emission Lines in a Complete Sample of 3CR Lobe-dominated Quasars

We present results from VLBI observations of 24 of the 25 lobe-dominated quasars (LDQs) in the 3CR complete sample and from optical spectrophotometry of 14 of these objects. The VLBI observations were made with a variety of arrays—most recently the Very Long Baseline Array—at frequencies ranging from 5 to 22 GHz during the period 1981–1997. The optical spectra were obtained with the Hale 200 inch (5 m) telescope at Palomar Observatory, using the blue and red CCDs of the Double Spectrograph, between 1984 and 1992. The radio nuclei range in strength over nearly 3 orders of magnitude, from ∼0.9 Jy down to ∼3 mJy, and were imaged at typical resolutions of ∼0.5–1.0 mas and sensitivities of ∼0.1–0.2 mJy beam-1. All 24 LDQs show detectable radio structure in their nuclei. All 19 objects for which VLBI images could be made show one-sided nuclear jets, often several milliarcseconds in length and significantly curved, on the same side of the compact core as the one-sided large-scale jets seen on Very Large Array images. No counterjets were observed; jet-to-counterjet ratios that virtually all exceed ∼10 suggest that these objects are all oriented within ∼70° to the line of sight. For the 10 sources in which parsec-scale jet speeds could be estimated, the well-defined motions range from ≲h-1c to ∼4h-1c; some ambiguous cases might allow for motions as fast as ∼8h-1c, even then they are not indicative of bulk Lorentz factors, γ, in excess of ∼10h-1 (H0 = 100h km s-1 Mpc-1, q0 = 0.5). While the present distribution of jet speeds is consistent with random orientations, it is more easily accomodated by a restricted range of orientations. Evidence for slower jet speeds and larger apparent bends close to the core support the concept of a "transition" zone in the inner few parsecs of these jets. There are significant correlations among the prominences of the cores and jets, relative jet length, maximum jet deflection angles, and variability amplitude, as well as possible trends involving jet speed and strength of compact jet knots; furthermore, these objects tend to exhibit flat-spectrum cores and steep-spectrum jets. These results are all consistent with orientation-dependent relativistic beaming effects and unification of core- and lobe-dominated quasars. We have also defined a new postulated measure of orientation, based on both prominence of the radio nucleus and projected linear size, that correlates very well with properties predicted to have strong orientation dependence on beaming models. Finally, we confirm earlier studies demonstrating an anticorrelation between the prominence of the radio nucleus and the width of broad Mg II λ2798 optical emission lines; we also extend this result to C III] λ1909 and, more generally, to all broad lines by simple scaling and normalization methods. This relationship suggests a restricted range of orientations for LDQs, and that the broad-line clouds may have a flattened distribution associated with the accretion zone surrounding a central supermassive black hole.

亜・遷音速流中におけるジェットの干渉による鈍頭物体底面部での圧力分布特性

The objective of the present study is to experimentally make clear the mechanism of aerodynamic interaction, in particular pressure interaction, due to a jet located off-center at the base of a blunt body with angle of attack in subsonic to transonic flow. The correlation between change in pressure drag and local pressure distribution by issuing the jet toward the downstream is obtained in terms of four parameters: the jet deflection angle, the jet mass flow rate, the freestream Mach number, and the angle of attack of model. Results indicate that the interacted flow field is characterized by three components: jet entrainment, vortex, and turn of main flow round the corner of the model base. At lower angle of attack than 15 degrees, the interacted flow shows different mechanisms between the inner and the outer regions at the base. In the inner region, pressure increases due to a vortex produced by jet entrainment, in which the circulated flow yields a stagnation point at the base. This is a favorable effect in terms of thrust. However, larger deflection of jet decreases the pressure in this region due to breakdown of the vortex. On the other hand, in the outer region, pressure decreases due to disappearance of a vortex produced in the case of no jet. At higher angle of attack than 15 degrees, more main flow comes to turn to the base round its corner. Consequently, the base pressure tends to have a uniform distribution with increasing the angle of attack. Moreover, increase in the jet mass flow rate makes this trend prominent, where the pressure in the outer region decreases to a certain level. Meanwhile, this pressure interaction increases with the freestream Mach number, which is caused by two effects:turn of more main flow to the base due to compressibility and jet expansion due to decrease in the ambient pressure.

Jet Deflection Angles in Military, Civil and RPV Thrust Vectoring Aircraft

Jet Deflection Angles in Military, Civil and RPV Thrust Vectoring Aircraft

The Influence of Fuel Jet Precession on the Global Properties and Emissions of Unconfined Turbulent Flames

Abstract An investigation was conducted to characterize the shape and size, the global radiation, and the CO and NOx, emissions of precessing jet flames and to compare these results with conventional, free, turbulent jet diffusion flames. Jet precession was accomplished using a mechanically-rotated nozzle. Parameters varied include nozzle diameter, jet deflection angle, initial jet velocity (Reynolds number), dimensionless precession frequency (Strouhal number), and fuel type. Measured quantities included visible flame dimensions; NOx, NO2, and CO emissions; and radiant heat flux. Results of these experiments showed that two broad regimes of flame type exist for precessing jet flames. For precession Strouhal numbers (St p ) less than about 0.01, flames are non-luminous and, in comparison with conventional flames, are short and broad. For St p > 0.03, flames are highly luminous, and of a shape which is between that of a conventional jet flame and the low-St p flame. In general, radiant fractions increase w...

Flight measurements of downwash on the Ball-Bartoe Jetwing powered lift aircraft

Flight tests were conducted with the Ball-Bartoe Jetwing powered lift technology demonstration aircraft to visualize flow angles on the fuselage surface and at selected points in the flowfield near the horizontal tail. Simple data acquisition techniques were used. The results were used to calculate the downwash near the horizontal tail and its variation with airspeed, jet deflection angle, and blowing coefficient over a range of level flight conditions. Further research is needed to broaden the database and substantiate these findings.

Aerodynamics of a finite aspect ratio jet flap at low flight speeds

A theoretical treatment of inviscid incompressible flow over a thin wing equipped with a part-span jet flap is given; the treatment is capable of describing low-speed flight regimes where nonlinear problems may be significant. The induced flow fields of the jet and the wing are characterized separately, and a fully coupled solution is reached through iteration. A lifting surface theory is employed for the wing aerodynamics, and the vorticity associated with the jet is also taken into account. Calculations are presented for the case of a rectangular wing. Comparisons with existing linear or nonlinear theories and experimental data suggest that the treatment is capable of accurate analyses in situations involving small angles of attack, jet deflection angles and jet momentum coefficients. In addition, the theory may be a better means of evaluating subsidiary aerodynamic variables, such as downwash aft of the wing, than existing treatments.