Synthetic Jet Actuator Research Articles

Проектирование блоков генераторов синтетических струй и экспериментальные исследования нестационарного истечения струй с помощью PIV- метода

Проектирование блоков генераторов синтетических струй и экспериментальные исследования нестационарного истечения струй с помощью PIV- метода

Microfabricated Electrodynamic Synthetic Jet Actuators

This paper presents the design, fabrication, and characterization of a chip-scale electrodynamic synthetic jet actuator with batch-fabricated die components. The actuator is an assembly of two dies with a plastic spacer sandwiched in between. The top die consists of a copper micro-coil and an orifice through which the jet is synthesized. The bottom die consists of a poly-dimethyl-siloxane diaphragm with a wax-bonded NdFeB magnet. When assembled, an ac current applied to the micro-coil forces an oscillatory actuation of the magnet, and correspondingly ingestion and expulsion of fluid through the orifice. The dimensions of the assembled actuator are 7.5 mm $\times7.5$ mm $\times1.1$ mm. The peak jet velocity is measured to be 4.3 m/s at 160 Hz for an input of 200-mA $_{pp}$ current corresponding to 20 mW of input electrical power. [2017-0166]

Continuous control of asymmetric forebody vortices in a bi-stable state

Aiming at the problem of continuous control of asymmetric forebody vortices at a high angle of attack in a bi-stable regime, a dual synthetic jet actuator embedded in an ogive forebody was designed. Alternating unsteady disturbance with varying degree asymmetrical flow fields near the nozzles is generated by adjusting the duty cycle of the drive signal of the actuator, specifically embodying the asymmetric time-averaged pattern of jet velocity, vorticity, and turbulent kinetic energy. Experimental results show that within the range of relatively high angles of attack, including the angle-of-attack region in a bi-stable state, the lateral force of the ogive forebody is continuously controlled by adjusting the duty cycle of the drive signal; the position of the forebody vortices in space, the vorticity magnitude, the total pressure coefficient near the vortex core, and the vortex breakdown location are continuously changed with the duty cycle increased observed from the time-averaged flow field. Instantaneous flow field results indicate that although the forebody vortices are in an unsteady oscillation state, a continuous change in the forebody vortices’ oscillation balance position as the duty cycle increases leads to a continuous change in the model’s surface pressure distribution and time-averaged lateral force. Different from the traditional control principle, in this study, other different degree asymmetrical states of the forebody vortices except the bi-stable state are obtained using the dual synthetic jet control technology.

Active Flow Vector Flight Control Using Only SJAs for a Fixed-Wing UAV

A novel flight control method for a fixed-wing unmanned aerial vehicle (UAV) is provided, which uses only synthetic jet actuators (SJAs) to achieve thrust vector control of the fixed-wing UAV. Firstly, the fluid model of the engine jet (or primary jet) and the SJAs are built, and the relation between the deflection angle of the primary jet and the amplitude of vibrating membrane of the SJAs is obtained. Secondly, based on the relation, a SJAs-based thrust vector control pitching motion model of the UAV is built. Thirdly, considering parameter uncertainties, unmodeled dynamics and unknown external disturbance of the system, an adaptive back-stepping sliding mode control (ABSMC) law is proposed, and pitching motion of the UAV is achieved by using only the SJAs-based thrust vector control. Finally, some simulations are conducted to analyze and verify the effectiveness of the flight control method. The results show that the thrust vector produced by the SJAs can enable the pitch control of the UAV and the ABSMC performs well in the presence of parameter uncertainties, unmodeled dynamics and unknown external disturbance of the system.

Attitude Control of Aircraft Using Only Synthetic Jet Actuators When Stall Occurs

This paper proposes a novel active flow control method for a special aircraft, that using only synthetic jet actuators (SJAs) to achieve pitch-roll-yaw attitude control at a high angle of attack when the stall occurs. The special aircraft goes without traditional aileron, elevator, or vertical stabilizer. As the first step, the model of the aircraft is built and the relation between the velocity amplitude of SJAs and the moments provided by SJAs are derived. The next step, to solve the problem that parameter uncertainties, unmodeled dynamics, and unknown external disturbances exist in the aircraft system, a sliding mode controller base on extended state observer (ESO) is designed. The parameter uncertainties, unmodeled dynamics, and unknown external disturbances are regarded as the compound interference of the system, which is estimated by the ESO and compensated in real time. Finally, the effectiveness of the proposed controller is verified through the numerical simulations. Simulation results show that the proposed control method is feasible and effective to solve the difficult problem of attitude control when the stall occurs.

Unsteady Simulation of a Synthetic Jet Actuator with Cylindrical Cavity Using a 3-D Lattice Boltzmann Method

A synthetic jet actuator is a zero-net mass-flux device that imparts momentum to its surroundings and has proved to be a useful active flow control device. Using the lattice Boltzmann method (LBM) with the Bhatnagar-Gross-Krook (BGK) collision models, a 3-D simulation of a synthetic jet with cylindrical cavity employing a sinusoidal velocity inlet boundary condition was conducted. The velocity distributions are illustrated and discussed, and the numerical results are validated against previous experimental data. The computed results show the ingestion and expulsion flow over one working cycle as well as the evolution of vortices important to the control of the separated shear layer. Zero-net mass-flux behavior is confirmed.

Indirect Inactivation of Candida guilliermondii by Using a Plasma Synthetic Jet Actuator: Effect of Advected Charged Particles

Indirect Inactivation of Candida guilliermondii by Using a Plasma Synthetic Jet Actuator: Effect of Advected Charged Particles

Characteristics of a Synthetic Jet Actuator and Its Application on Control of Flow over a Backward Facing Step

Characteristics of a Synthetic Jet Actuator and Its Application on Control of Flow over a Backward Facing Step

The Frequency Excitation and Cavity Shape Changes Effect to the Vortex Ring Formation of the Synthetic Jet Actuator

The Frequency Excitation and Cavity Shape Changes Effect to the Vortex Ring Formation of the Synthetic Jet Actuator

Formation, evolution and scaling of plasma synthetic jets

Plasma synthetic jet actuators (PSJAs), capable of producing high-velocity pulsed jets at high frequency, are well suited for high-Reynolds-number subsonic and supersonic flow control. The effects of energy deposition and actuation frequency on the formation and evolution characteristics of plasma synthetic jets (PSJs) are investigated in detail by high-speed phase-locked particle imaging velocimetry (PIV). Increasing jet intensity with energy deposition is mainly contributed by the increasing peak jet velocity ($U_{p}$), while decreasing jet intensity with actuation frequency is attributed to both the reduced cavity density (primary factor) and the shortened jet duration (secondary factor). The total energy efficiency of the considered PSJA ($O(0.01\,\%)$) reduces monotonically with increasing frequency, while the time-averaged thrust produced by the PSJA is positively proportional to both the deposition energy and the frequency. A simplified theoretical model is derived and reveals a scaling power law between the peak jet velocity and the non-dimensional deposition energy (exponent$1/3$). The propagation velocity of the vortex ring attached at the jet front shows a non-monotonic behaviour of initial sharp increase and subsequent mild decay. The peak values for both the propagation velocity and the circulation of the front vortex ring are reached approximately two exit diameters away from the exit. Finally, analysis of the time-averaged flow fields of the issuing PSJ indicates that the axial decay rate of the centreline velocity is proportional to the actuation frequency whereas it is invariant with the energy deposition. The jet spreading rate of the PSJ is found to be higher than steady jets but lower than piezoelectric synthetic jets. Similarly, the entrainment coefficients of the PSJ are found to be twice as high as the values for comparable steady jets.

Hydrodynamic characteristic of synthetic jet steered underwater vehicle

In this paper, the hydrodynamic characteristic of a synthetic jet steered underwater vehicle is studied. The steering motion studied is the lateral motion and the yaw motion. The lateral motion is induced through the in-phase work of this two actuators and the yaw motion is realized through the out-of-phase work. The vehicle studied is REMUS AUV with synthetic jet actuator mounted inside. The hydrodynamic characteristic of the vehicle under different cruising speed is studied. The driving parameters of the SJ actuator keep invariant in different cases. When the two actuators work in phase, the average steering force is smaller than the thrust of the isolated actuator and keeps nearly invariant under different cruising speed. When the two actuators work out of phase, the average steering moment also keeps invariant with cruising speed. The mathematical model of the additional drag of the vehicle, the thrust of the actuator, the steering force as well as the steering moment is given. The velocity distribution is also given to assistant the analysis in this paper. From the analysis given it can be known the steering method based on SJ is realized through position control other than velocity control.

Numerical Characterisation of Active Drag and Lift Control for a Circular Cylinder in Cross-Flow

Synthetic jet actuators have shown promise to control drag and lift for a bluff body in cross-flow. Using unsteady RANS CFD modelling, a significant modification of the drag coefficient for a circular cylinder in cross-flow at R e = 3900 is achieved by varying the actuation frequency. The variation in actuation frequency corresponds to a range in Stokes number of 2.4 < S t o < 6.4. The trends in drag coefficient modification largely agree with the findings of past publications, achieving a maximum drag reduction at S t o = 4.9 for a fixed jet Reynolds number of the synthetic jet of R e U ¯ o = 12. A decrease in the adverse pressure gradient near the jet orifice correlated with a momentum increase in the viscous sublayer and stronger vortical structures at the rear of the cylinder. In these same conditions, a decrease in turbulence intensity was observed in the far field wake, which is a relevant finding in the context of wind and tidal turbine arrays.

Numerical investigation of the influence of nozzle geometrical parameters on thrust of synthetic jet underwater

The thrust characteristic and efficiency of synthetic jet underwater is easily affected by the geometrical parameters. In this paper, the influence of nozzle geometrical parameters on the thrust of synthetic jet underwater is investigated through numerical method. The geometrical parameters studied include nozzle diameter and nozzle height. The numerical method is validated using the experiment data. A mathematical model of the thrust is established. This model decomposes the thrust into three parts. By adjusting the weights of these parts, the dynamic characteristic of the thrust can be rebuilt. Using this method, the mechanism behind the thrust variation with nozzle geometrical parameters is analyzed. The variation of the thrust with the nozzle diameter is induced by the increase of the acceleration force and the decrease of the pressure force. When the nozzle diameter is small, the thrust is velocity dominated. While when diameter is large, the thrust is acceleration dominated. The thrust variation with nozzle height has two different patterns. The pressure force dominates the first pattern of thrust variation. And the acceleration force contributes more to the second pattern of thrust variation. The results in this paper can be used for the efficiency oriented optimal design of synthetic jet actuator underwater.

Experimental investigation on frequency characteristics of plasma synthetic jets

The performance of a two-electrode plasma synthetic jet actuator (PSJA) is investigated for a wide range of dimensionless actuation frequencies ( f*) using high-speed phase-locked particle imaging velocimetry measurements. The jet-induced velocity fields in the axisymmetric plane are measured during both transient and steady working stages of the PSJA. When f* increases, the jet duration time (Tjet) is reduced, while the peak suction velocity (Us) increases consistently. Three integral parameters including the total expelled gas mass, impulse, and issued mechanical energy also decline considerably with increasing frequency, which is shown to relate to both the reduced cavity density and the decreasing jet duration. Theoretical analysis reveals that the mean cavity density decreases monotonically with the square root of the discharge frequency. The decreasing rate is inversely proportional to a thermal cut-off frequency ( fc, 210 Hz for the current study), which scales with the convective heat transfer coefficient between the actuator cavity walls and the cavity gas, as well as the area of the cavity internal surface. In the time-averaged velocity fields, the jet centreline velocity (U¯c) exhibits a local maximum in the axial coordinate. The nondimensional maximum centreline velocity reduces with increasing frequency of operation. The jet spreading rate of the plasma synthetic jets (PSJs) decreases from 0.14 to 0.09 with increasing frequency. During the transient working stage of a PSJ, the exit velocity trace elapses 20 successive actuation cycles to stabilize. In contrast to the exit velocity, approximately 130 cycles are needed for the mean cavity density/temperature to reach steady values.

High-frequency counter-flow plasma synthetic jet actuator and its application in suppression of supersonic flow separation

We come up with a control strategy for suppression of supersonic flow separation based on high-frequency Counter-flow Plasma Synthetic Jet Actuator (CPSJA). The main purpose of this investigation is to verify if its control authority can be enhanced by the jet/shock interaction. We use a blunt nose to generate a bow shock, a step on a flat plate to introduce a massive separation in a Mach 2 wind tunnel, and the CPSJA to generate Plasma Synthetic Jet (PSJ). In this study, pulsed capacitive discharge is provided for an array of CPSJAs, which makes the actuation (discharge) frequency f1 = 1 kHz, f2 = 2 kHz and f3 = 3 kHz. We use the high-speed schlieren imaging and fast response pressure transducers as well as a numerical simulation to investigate the quiescent PSJ properties, the interaction between the jet and bow shock, and its disturbance effect on the downstream separated region. The schlieren images show that PSJ is characterized by a succession of vortex rings; the jet strength weakens with the increase of frequency. A 4.5 mN jet thrust is found for all the frequencies. The simulation results show that jet/shock interaction produces vorticity in the vortex ring of the jet, enhancing turbulent mixing in PSJ so that a great deal of momentum is produced into the flow. We found the downstream flow is significantly disturbed by the enhanced actuation. Actuation with frequency of f2, f3 which is close to the natural frequency fn of the separation bubble suppresses the separation with the upstream laminar boundary layer being periodically attenuated, which has a better control effect than f1. The control effect is sensitive to the position where PSJ interacts with the shear layer, but the amount of energy deposited in one pulse is not crucial in a separation reduction in the experiment.

A Computational Fluid Dynamic Study of the Effects of a Synthetic Jet Actuator on an Airfoil

A Computational Fluid Dynamic Study of the Effects of a Synthetic Jet Actuator on an Airfoil

The failure of delayed detached eddy simulation for flow control over a hump using synthetic jet actuator

The performance of three different numerical methods for predicting the large separated flow over a hump model and its control using steady suction and techniques is investigated. Unsteady Reynolds Averaged Navier-Stokes (URANS), Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) approaches are developed and applied to determine the proficiency of these approaches in predicting such degree of separation and assess their applicability to capture the turbulent flow structures in the separated flowfield. Active flow control techniques are applied by means of two-dimensional slot located at x/c -0.65 along the model spanwise with an opening of 0.00187c, directly upstream on the concave surface. The novelty of the present work is that the dynamic grid technique is formulated to model the repeated motion of the synthetic jet membrane instead of using the oscillating boundary conditions at the jet exit. Dynamic grid is found to be useful in providing more insight into the physical mechanism that drive the interface between the plenum flow and separated boundary layer flow. The numerical results obtained from the baseline and controlled cases are validated against the measurements and compared with published numerical results in terms of mean flow quantities. Despite the fact that URANS and DES methods provide good agreement with the measurements for the uncontrolled and steady suction controlled cases, only DES showed the flow unsteadiness, however the DDES method failed to predict the mean flow quantities or the turbulent flow features. The dynamic grid technique successfully simulated the cavity flow, showed up the existence of two counter rotating vortices inside the plenum move up and down during the control cycle and finally energized the boundary layer in the separated flow region.

Towards the noise reduction of piezoelectrical-driven synthetic jet actuators

This work details an experimental investigation aimed at reducing the noise output of piezoelectrical-driven synthetic jet actuators while minimising peak jet velocity reduction. The study considers double-chamber actuator for anti-phase noise suppression and lobed orifice as a method to enhance jet turbulent mixing to suppress jet noise. The study involved the design, manufacture and bench test of interchangeable actuator hardware. Hot-wire anemometry and microphone recordings were employed to acquire velocity and sound pressure level measurements respectively across a range of excitation frequencies for a fixed diaphragm clamping and input voltage. The data analysis indicated a 26% noise reduction (16dB) from operating a single-chamber, round orifice actuator to a double-chamber, lobed orifice one at the synthetic jet resonant frequency. Results also showed there was a small reduction in peak jet velocity of 7% (∼3m/s) between these two cases based on orifices of the same discharge area. The electrical-to-fluidic power conversion efficiency of the double-chamber actuator was found to be 15% for both orifice types at the resonant frequency; approximately double the efficiency of a single-chamber actuator.

Accurate Discrete Adjoint Approach for Optimal Active Separation Control

This paper presents the development of an accurate and robust discrete adjoint approach for the optimization of active flow control mechanism. The adjoint solver is developed by applying algorithmic differentiation techniques to an incompressible unsteady Reynolds-averaged Navier–Stokes solver. Coupled with a quasi-Newton gradient-search optimization algorithm, its applicability is demonstrated by finding the optimal synthetic jet actuation on the suction side of the NACA 4412 airfoil at a Reynolds number and angle of incidence of 20 deg. Numerical results have shown that the actuation sensitivities based on the unsteady discrete adjoint solver are in excellent agreement with the values obtained from the tangent-linear solver and finite differences. Compared to the stalled baseline flow, optimal actuated flow significantly increased the time-averaged lift by 54%, and the stall is delayed from 16 to 22 deg. A detailed analysis of sensitivities and the effect of optimal actuation on the separation is presented.

Particle Image Velocimetry Experiment Analysis Using Large-Eddy Simulation: Application to Plasma Actuators

This article presents an analysis of a planar particle image velocimetry experiment aiming at measuring the phase-averaged velocity fields of a synthetic jet generated by a plasma synthetic jet actuator. Three major sources of uncertainty related to this type of experiment are examined: the phase-averaging process, the estimation of the vertical position of the wall into which the actuator is inserted, and the position of the laser sheet plane. Furthermore, the present work investigates the errors related to the dynamics of the particles used for seeding this type of high-speed transient flow. As expected, uncertainties associated with the phase-averaging process and the estimation of the wall position may be directly estimated from the measurements. However, estimation of the uncertainties originating from the position of the laser sheet plane and the errors related to the particle dynamics require additional information. In the present work, an original methodology relying on a numerical model of the actuator is thus proposed. This model, based on a large-eddy simulation, is able to reproduce the main features of the jet observed in the experiments and is used to generate realistic synthetic particle images. The influence of the laser sheet position on the velocity uncertainties and the errors associated with the particle dynamics are then explored. Experimental and numerical findings are considered to conclude in a quantitative manner on the dominant sources of uncertainty for such experiments and on the errors induced by particle dynamics that should be expected.