Jet Velocity Enhancement of Synthetic Jets: Unimorph vs. Bimorph Piezoelectric Actuator

Analytical and Experimental Investigation of Different Synthetic Jet Actuator Configurations

Aerospace ◽

10.1115/imece2004-62485 ◽

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.

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Flow and heat transfer characteristics under synthetic jets impingement driven by piezoelectric actuator

Experimental Thermal and Fluid Science ◽

10.1016/j.expthermflusci.2013.02.016 ◽

2013 ◽

Vol 48 ◽

pp. 134-146 ◽

Cited By ~ 43

Author(s):

Xiao-Ming Tan ◽

Jing-Zhou Zhang

Keyword(s):

Heat Transfer ◽

Piezoelectric Actuator ◽

Synthetic Jets ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Flow And Heat Transfer

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Pressure Loading of Piezo Composite Unimorphs

MRS Proceedings ◽

10.1557/proc-0888-v01-06 ◽

2005 ◽

Vol 888 ◽

Cited By ~ 1

Author(s):

Poorna Mane ◽

Karla Mossi ◽

Robert Bryant

Keyword(s):

Active Flow Control ◽

Synthetic Jet ◽

Synthetic Jets ◽

Synthetic Jet Actuator ◽

Active Pressure ◽

Average Maximum ◽

Non Local ◽

Jet Velocity ◽

Active Flow ◽

Jet Velocities

ABSTRACTOver the past decade synthetic jets have emerged as a promising means of active flow control. They have the ability to introduce small amounts of energy locally to achieve non-local changes in the flow field. These devices have the potential of saving millions of dollars by increasing the efficiency and simplifying fluid related systems. A synthetic jet actuator consists of a cavity with an oscillating diaphragm. As the diaphragm oscillates, jets are formed through an orifice in the cavity. This paper focuses on piezoelectric synthetic jets formed using two types of active diaphragms, Thunder® and Lipca. Thunder® is composed of three layers; two metal layers, with a PZT-5A layer in between, bonded with a polyimide adhesive. Lipca is a Light WeIght Piezo Composite Actuator, formed of a number of carbon fiber prepreg layers and an active PZT-5A layer. As these diaphragms oscillate, pressure differences within the cavity as well as average maximum jet velocities are measured. These parameters are measured under load and no-load conditions by controlling pressure at the back of the actuator or the passive cavity. Results show that the average maximum jet velocities measured at the exit of the active cavity, follow a similar trend to the active pressures for both devices. Active pressure and jet velocity increase with passive pressure to a maximum, and then decrease. Active pressure and the jet velocity peaked at the same passive cavity pressure of 18kPa for both diaphragms indicating that the same level of pre-stresses is present in both actuators even though Lipca produces approximately 10% higher velocities than Thunder®.

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Formation, evolution and scaling of plasma synthetic jets

Journal of Fluid Mechanics ◽

10.1017/jfm.2017.855 ◽

2017 ◽

Vol 837 ◽

pp. 147-181 ◽

Cited By ~ 27

Author(s):

Haohua Zong ◽

Marios Kotsonis

Keyword(s):

Vortex Ring ◽

Propagation Velocity ◽

High Speed ◽

Energy Deposition ◽

Synthetic Jet ◽

Synthetic Jets ◽

Actuation Frequency ◽

Jet Velocity ◽

Deposition Energy ◽

Steady 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.

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Characterization and Thrust Optimization of Synthetic Jets

Volume 2: Fora ◽

10.1115/fedsm2006-98312 ◽

2006 ◽

Author(s):

Yury Loayza ◽

Kamran Mohseni

Keyword(s):

Velocity Field ◽

Synthetic Jet ◽

Synthetic Jets ◽

Voltage Response ◽

Zero Mass ◽

Formation Number ◽

Temporal And Spatial ◽

Jet Velocity ◽

Velocity Changes ◽

Hotwire Anemometry

A synthetic jet is a zero-mass pulsatile jet. A common approach in creating a synthetic jet is to use a cavity with an orifice on one side and an oscillating membrane on another side. In this study the dynamics of a piezoelectrically driven synthetic jet is investigated using a laser nano sensor to capture the temporal and spatial deflection of the membrane. The frequency and voltage response of the piezoelectric membrane for different cavity dimensions are presented, while the velocity field of the resulted jet is characterized by hotwire anemometry. Subsequently, the volume of the expelled jet for any given exit diameter is correlated to the resulting jet velocity. It is found that at a formation number around 3 the nature of the average jet velocity changes and the resulting jet velocity shows less sensitivity to the formation number.

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Frequency Response of Synthetic Jets Emanating From an Array of Circular Orifices

10.1115/fedsm2021-65225 ◽

2021 ◽

Author(s):

Nadim Arafa ◽

Pierre Sullivan ◽

Alis Ekmekci

Keyword(s):

Frequency Response ◽

Excitation Frequency ◽

Acoustic Mode ◽

Synthetic Jet ◽

Synthetic Jets ◽

Mode Shapes ◽

Long Span ◽

Jet Actuators ◽

The Mean ◽

Jet Velocity

Abstract The effect of the excitation frequency of synthetic jet actuators on the mean jet velocity of synthetic jets issuing from an array of circular orifices is investigated experimentally. Herein, the focus is placed on an array of circular orifices, rather than a single orifice, as it brings the advantage of covering long-span airfoils. The array consists of 16 circular orifices, each having a diameter of 3.42 mm, distributed over a span of 300 mm. The jets are generated by the excitation of a single cavity via 16 piezoelectric elements. Localized velocity measurements at the exit of the orifices show that the mean jet velocity varies with the excitation frequency. Several distinct resonant peaks were observed in the frequency response. Acoustic simulations of the cavity showed that these peaks correspond to acoustic mode shapes of the cavity. Due to the high-aspect ratio of the cavity, several acoustic mode shapes exist in the excitation frequency range aside from the Helmholtz resonance frequency. Moreover, the mean jet velocity emanating from the array shows a variation from orifice to orifice, depending on the excited acoustic mode.

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