Jet vectoring using synthetic jets

2002 ◽  
Vol 458 ◽  
pp. 1-34 ◽  
Author(s):  
B. L. SMITH ◽  
A. GLEZER
Keyword(s):  
Flow Rate ◽  
Volume Flow Rate ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Control Surface ◽  
Piv Measurements ◽  
Synthetic Jet Actuator ◽  
Recirculating Flow ◽  
Air Jet ◽  
Image Velocimetry

The interaction between a conventional rectangular (primary) air jet and a co-flowing synthetic jet is investigated experimentally. The nozzles of both jets have the same long dimension but the aspect ratio of the synthetic jet orifice is 25 times larger. Detailed particle image velocimetry (PIV) measurements of the flow in the midspan plane show that primary jet fluid is directed into the synthetic jet orifice and the interaction between the jets leads to the formation of a closed recirculating flow domain. The concomitant formation of a low-pressure region between the jets results in deflection of the primary jet toward the actuator jet despite the absence of an extended control surface (e.g. a diffuser or collar) and is balanced by a force on the primary jet conduit. For a given synthetic jet strength and primary jet speed, the vectoring force depends mainly on the volume flow rate of primary jet fluid that is diverted into the synthetic jet actuator. This flow rate is regulated by restricting the flow of entrained ambient fluid using a small streamwise extension of the synthetic jet orifice that scales with the orifice width. The response of the primary jet to the imposed vectoring is investigated using stepped modulation of the driving signal. The characteristic vectoring time and vectoring angle decrease monotonically with primary jet speed.

PIV MEASUREMENTS OF DUAL SYNTHETIC JETS ACTUATOR DRIVEN BY ELECTRICAL FACTORS

2009 ◽  
Vol 23 (03) ◽  
pp. 417-420 ◽  
Author(s):  
ZHEN-BING LUO ◽  
ZHI-XUN XIA ◽  
BING LIU ◽  
DE-QUAN WANG ◽  
JIAN-XIN HU ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Driving Voltage ◽  
Transfer Phase ◽  
Piv Measurements ◽  
Synthetic Jet Actuator ◽  
Arbitrary Phase ◽  
Image Velocimetry

A dual synthetic jets actuator driven by different electrical factors was investigated using particle image velocimetry (PIV). A transfer-phase and sub-frequency technique was provided to capture the arbitrary phase of the dual synthetic jets, and a transfer-phase to equal technique was provided to determine the phase of the dual synthetic jets. The results show that both the amplitude and frequency of the electrical forcing voltages vastly affect the flow-field of the dual synthetic jets actuator. Both the forcing frequency and the driving voltage amplitudes contribute to the pressure difference and the area of the lower pressure, which determines the interactions of dual synthetic jets. The dual synthetic jet actuator exits a circumscription of electrical factors in which the actuator works efficiently.

Wing tip vortex control using synthetic jets

2006 ◽  
Vol 110 (1112) ◽  
pp. 673-681 ◽  
Author(s):  
P. Margaris ◽  
I. Gursul
Keyword(s):  
Synthetic Jet ◽  
Synthetic Jets ◽  
Tip Vortex ◽  
Particle Image Velocimetry System ◽  
Driving Frequency ◽  
Velocity Measurements ◽  
Vortex Control ◽  
Image Velocimetry ◽  
Wing Tip ◽  
Jet Blowing

AbstractAn experimental investigation was conducted to study the effect of synthetic jet (oscillatory, zero net mass flow jet) blowing near the wing tip, as a means of diffusing the trailing vortex. Velocity measurements were taken, using a Particle Image Velocimetry system, around the tip and in the near wake of a rectangular wing, which was equipped with several blowing slots. The effect of the synthetic jet was compared to that of a continuous jet blowing from the same configurations. The results show that the use of synthetic jet blowing is generally beneficial in diffusing the trailing vortex and comparable to the use of continuous jet. The effect was more pronounced for the highest blowing coefficient used. The driving frequency of the jet did not generally prove to be a significant parameter. Finally, the instantaneous and the phase-locked velocity measurements helped explain the different mechanisms employed by the continuous and synthetic jets in diffusing the trailing vortex.

Design and Thermal Characteristics of a Synthetic Jet Ejector Heat Sink

2004 ◽  
Vol 127 (2) ◽  
pp. 172-177 ◽  
Author(s):  
Raghav Mahalingam ◽  
Ari Glezer
Keyword(s):  
Thermal Resistance ◽  
Steady Flow ◽  
Heat Sink ◽  
Power Dissipation ◽  
Ambient Air ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Transfer Coefficients ◽  
Electromagnetic Actuators ◽  
Air Jet

The design and thermal performance of a synthetic-air-jet-based heat sink for high-power dissipation electronics is discussed. Each fin of a plate-fin heat sink is straddled by a pair of two-dimensional synthetic jets, thereby creating a jet ejector system that entrains cool ambient air upstream of the heat sink and discharges it into the channels between the fins. The jets are created by periodic pressure variations induced in a plenum by electromagnetic actuators. The performance of the heat sink is assessed using a thermal test die encased in a heat spreader that is instrumented with a thermocouple. The case-to-ambient thermal resistance under natural convection with the heat sink is 3.15°C∕W. Forced convection with the synthetic jets enables a power dissipation of 59.2W at a case temperature of 70°C, resulting in a case-to-ambient thermal resistance of 0.76°C∕W. The synthetic-jet heat sink dissipates ∼40% more heat compared to steady flow from a ducted fan blowing air through the heat sink. The synthetic jets generate a flow rate of 4.48 CFM through the heat sink, resulting in 27.8 W/CFM and thermal effectiveness of 0.62. The effect of fin length on the thermal resistance of the heat sink is discussed. Detailed measurements on an instrumented heat sink estimate that the average heat transfer coefficients in the channel flow between the fins is 2.5 times that of a steady flow in the ducts at the same Reynolds Number.

Analytical and Experimental Investigation of Different Synthetic Jet Actuator Configurations

Aerospace ◽  
2004 ◽  
Author(s):  
Sandra Ugrina ◽  
Alison Flatau
Keyword(s):  
Resonant Frequency ◽  
Smart Materials ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Laser Vibrometer ◽  
Synthetic Jet Actuator ◽  
Exit Nozzle ◽  
Geometry Configuration ◽  
Jet Velocity ◽  
Constant Temperature Anemometer

The ultimate goal of this project is to actively control the flow over a micro air vehicle using smart materials. MAVs are a new type of aircraft operating at Reynolds numbers of about 50,000 that are one to two orders of magnitude lower than encountered in larger aircraft. The intention is to implement smart structures and couple them with fluids to improve the deteriorated aerodynamics of MAVs and help improve efficiency, stability and maneuverability of such vehicles. The actuators used in this work for artificially controlling the boundary layer are piezoelectrically driven synthetic jets. We theoretically investigated and predicted the behavior of the synthetic jet as we changed the geometry and material property parameters of the actuator. Analytical results were then compared to the results obtained from the experiments. It is crucial to be able to accurately design a strong unimorph to be implemented as an active component of a synthetic jet actuator and design the geometry configuration of the cavity that will best couple with the chosen membrane. A condenser microphone, a constant temperature anemometer (CTA) and a laser vibrometer were used to quantify actuator performance. It was observed that the size of the cavity and the size and shape of the exit nozzle were related and the performance of the actuator increased when the structure was tuned such that the resonant frequency of the diaphragm and that of the cavity were close to matching. A square unimorph made of PZT-5H and bonded to a 0.20- mm brass shim maximized jet velocity for the actuators studied. Optimum direction of change in the volume and the dimensions of the nozzle will strongly depend on the resonant frequency of the membrane in use. In this situation, increasing either the volume of the cavity or the thickness of the nozzle made the two frequencies move away from each other producing reduction in jet velocity. Increasing the area of the nozzle, made the structure behave more as needed and was taken as a key parameter for tuning the base geometry of the device.

THE MECHANISM OF JET VECTORING USING SYNTHETIC JET ACTUATORS

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1619-1622 ◽  
Author(s):  
ZHEN-BING LUO ◽  
ZHI-XUN XIA
Keyword(s):  
Static Pressure ◽  
Deflection Angle ◽  
Control Mechanism ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Control Mechanisms ◽  
Synthetic Jet Actuator ◽  
Synthetic Jet Actuators ◽  
Jet Actuators ◽  
Main Factors

The control mechanism of jet vectoring using synthetic jet actuators is investigated. The final deflection angle of the primary jet is a result of the primary jet controlled by synthetic jets at three different regions. The lower static pressure near the primary jet exit induced by the synthetic jet, the entrainment and absorption of the primary jet fluid by the synthetic jet during the blowing and the suction stroke, the coupling and interaction between the vortices of synthetic jet and the shear layer of the primary jet are the main control mechanisms for the synthetic jet actuator vectoring a primary jet. The main factors influencing jet vectoring are analyzed and summarized, and a preparatory model for jet vectoring using synthetic jet actuator is presented.

2D numerical study of circular synthetic jets in quiescent flows

2005 ◽  
Vol 109 (1092) ◽  
pp. 89-97 ◽  
Author(s):  
H. Tang ◽  
S. Zhong
Keyword(s):  
Experimental Data ◽  
Numerical Study ◽  
Initial Study ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Neutral Position ◽  
Computational Results ◽  
Synthetic Jet Actuator ◽  
Field Velocity ◽  
Turbulent Models

Abstract2D numerical simulations of flows generated by a synthetic jet actuator with a circular orifice were conducted at two different diaphragm displacement settings, one representing a typical laminar case and the other a fully turbulent case. The flow in the cavity was included in the computation in order to provide more accurate predictions. A velocity boundary condition was applied at the neutral position of the diaphragm to account for its temporal deformation. Comparisons were made between the computational results and existing PIV and hot-wire data in terms of the time sequence of the velocity vector field, velocity variations in space and with time. It is found that computational results for the laminar case agree well with the experimental data. Four turbulent models were tested for the fully turbulent case. It was found that the predictions using the RNG κ-ε and Standard k-ε models were reasonably close to the experimental data. This initial study has produced some encouraging evidence for the capacity of FLUENT in simulating the key features of synthetic jets.

Examination of a Variable-Diameter Synthetic Jet

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Spencer O. Albright ◽  
Stephen A. Solovitz
Keyword(s):  
Particle Image Velocimetry ◽  
Vortex Ring ◽  
Mass Flux ◽  
Particle Image ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Variable Diameter ◽  
Constant Diameter ◽  
Image Velocimetry ◽  
Jet Actuators

Synthetic jet actuators are used to produce net axial momentum flow without net mass flux. Through strategic application, such devices can be used for flow control, propulsive thrust, and cooling. A novel application uses a variable-diameter orifice to constrict the exiting flow, and the motion can be synchronized with the pulse of the jet. This device is examined using phase-locked particle image velocimetry (PIV), permitting investigation of the flow fields and momentum flow. When compared to fixed-diameter synthetic jets, the variable-diameter actuator produces a larger vortex ring that lingers nearer the aperture. In addition, the experiments show increased momentum when the aperture is contracted in phase with the pulsing jet, with peak levels more than twice that of a constant-diameter jet.

Experimental Characterization of a Micro-Blower for Flow Control

2019 ◽  
Author(s):  
Maria Wu ◽  
Pierre Sullivan
Keyword(s):  
Flow Control ◽  
Turbulent Jets ◽  
Synthetic Jet ◽  
Experimental Characterization ◽  
Continuous Mode ◽  
Mean Velocity ◽  
Burst Mode ◽  
Synthetic Jet Actuator ◽  
Image Velocimetry

Abstract A compact, lightweight, low-power piezoelectric micro-blower was characterized using particle image velocimetry to determine its flow control potential. The micro-blower has been operated in continuous mode as well as in burst mode using two different actuation frequencies. The maximum mean velocity measured with the micro-blower operating in continuous mode was approximately Ūmax = 13 m/s which occurred at the centerline at an approximate stream-wise location of x/d = 4. The velocity profiles in the developed region resemble those of turbulent jets. The momentum-flux from the micro-blower in continuous mode was significantly greater than a typical synthetic jet actuator which was successfully used for flow control, indicating that the micro-blower can impart the necessary momentum to be effective for flow control. With burst mode, the results show that the micro-blower could impart an even greater momentum.

Performance Characterization of a Piezoelectric Micro SJA

2009 ◽  
Vol 74 ◽  
pp. 223-226
Author(s):  
An Shik Yang ◽  
Jeng Jong Ro ◽  
Wei Han Chang
Keyword(s):  
Near Field ◽  
Vortex Pair ◽  
Computer Code ◽  
Synthetic Jet ◽  
Driving Voltage ◽  
Synthetic Jet Actuator ◽  
Air Jet ◽  
Jet Actuators ◽  
Jet Behavior

This paper aims to explore the synthetic jet behavior for a dual-diaphragm piezoelectrically driven micro synthetic jet actuator. For a sinusoidal actuation cycle at an operating frequency of 648 Hz, the synthetic jet flow pattern was simulated and compared with the visualized image and measured centerline velocity distribution to validate the computer code. The far-field flow structure was similar to a common continuous turbulent air jet; whereas, the unsteady formation of a vortex pair was predicted in the near-field. Numerical experiments were extended to appraise performance of micro synthetic jet actuators by varying the driving voltage, width of the slot and depth of the actuator cavity.

Heat Transfer Measurements of Impinging Synthetic Air Jet

2007 ◽  
Author(s):  
Alan McGuinn ◽  
Tadhg S. O’Donovan ◽  
Darina B. Murray
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Impinging Jets ◽  
Copper Plate ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Driving Frequency ◽  
Promising Alternative ◽  
Air Jet ◽  
Cooling Effects

The implementation of synthetic jets for use in the cooling of electronics is a relatively new technology. It is well established that effective rates of cooling can be achieved using conventional steady flow impinging jets. However it has been shown that synthetic jets can deliver similar cooling effects without the need for an air supply system and therefore represent an extremely promising alternative for thermal management applications. A study has been undertaken of the heat transfer distribution to an impinging synthetic jet flow. The jet is directed at a heated copper plate, which approximates a uniform wall temperature. Nusselt number profiles generated by the synthetic jet for various Reynolds numbers and heights above the plate were obtained. Time varying velocity measurements were also carried out to provide information about the flow characteristics of the synthetic jet and to aid with evaluation of the heat transfer data. For continuous jets mean heat transfer distributions have been shown to have a direct relation to jet velocity profiles, however, for synthetic jets fluctuations in local heat flux illustrate a significant dependence on the driving frequency.

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