Numerical Investigation of Controlling Mixing in Coaxial Jets Using Synthetic Jet Actuator Arrays

2008 ◽  
Author(s):  
Yanming Liu ◽  
Baoguo Wang ◽  
Shuyan Liu
Keyword(s):  
Near Field ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Mixing Enhancement ◽  
Mixing Processes ◽  
Turbulent Dissipation ◽  
Synthetic Jet Actuator ◽  
Control Effectiveness ◽  
Coaxial Jets ◽  
Actuator Arrays

A Numerical Simulation has been conducted to investigate the mixing of coaxial jets with zero-mass-flux synthetic jet actuators, two arrays of which are placed side by side around coaxial jets and in the exit plane of the outer primary jet. Both the temperature field of the primary jet and mixing processes are studied at given temperature ratio. High-frequency forcing leads to increases in the radial extent of the jet and turbulent intensity in the near-field and increased turbulent dissipation. During the analysis, the influence of adjacent synthetic jets is also considered. The comparison is made between the control effectiveness of two arrays of actuators and that of an array of actuators. The results show both of the actuator’s configurations can result in the significant mixing enhancement, but the former exhibits more desirable.

Investigation of Phasing on Synthetic Jet Actuator Arrays

2013 ◽  
Vol 465-466 ◽  
pp. 541-545
Author(s):  
Jhao Jinq Goh ◽  
Ann Lee
Keyword(s):  
Continuous Flow ◽  
Main Channel ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Maximum Temperature ◽  
Cooling Performance ◽  
Synthetic Jet Actuator ◽  
Actuator Arrays ◽  
Flow Mixing ◽  
Jet Actuators

Unsteady computations of laminar flow have been performed for two-dimensional configurations of micro-channel equipped with two synthetic jets. The effect of phasing has been investigated at in-phase and 180̊ out-of-phase of the synthetic jet actuators at a fixed operating frequency and oscillating amplitudes. It was shown that the 180̊ out-of-phase configuration of the synthetic jets promotes better and more continuous flow mixing within the channel during the oscillation. This was due to the discrete pattern of vortex forming which disrupts the main channel flow. The 180̊ out-of-phase jet configuration exhibits higher cooling performance compared to the in-phase jet configuration in terms of the reduction in the maximum temperature in the silicon wafer.

The performance of round synthetic jets in quiescent flow

2006 ◽  
Vol 110 (1108) ◽  
pp. 385-393 ◽  
Author(s):  
M. Jabbal ◽  
J. Wu ◽  
S. Zhong
Keyword(s):  
Near Field ◽  
Jet Flow ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Operating Conditions ◽  
Stroke Length ◽  
Synthetic Jet Actuators ◽  
Macro Scale ◽  
Jet Actuators ◽  
The Impact

AbstractPIV measurements in the near-field region of a jet flow emanating from a round synthetic jet actuator into quiescent air were conducted over a range of operating conditions. The primary purpose of this work was to investigate the nature of synthetic jets at different operating conditions and to examine the jet flow parameters that dictate the behaviour of synthetic jet actuators. The effects of varying diaphragm displacement and oscillatory frequency for fixed actuator geometry were studied. It was observed that the characteristics of synthetic jets are largely determined by the Reynolds number and stroke length. An increase in the former is observed to increase the strength of consecutive vortex rings that compose a synthetic jet, whereas an increase in the latter results in an increase in relative vortex ring spacing and for further increases in stroke length, shedding of secondary vortices. Correlations were also made between the operating parameters and the performance parameters most effective for flow control and which therefore determine the impact of a synthetic jet on an external flow. Relations of time-averaged dimensionless mass flux, momentum flux and circulation with the jet flow conditions were established and found to widely support an analytical performance prediction model described in this paper. It is anticipated that the experimental data obtained in this study will also contribute towards providing a PIV database for macro-scale synthetic jet actuators.

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.

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.

Effects of inlet and outlet boundary conditions on the flow field of synthetic jets

2016 ◽  
Vol 231 (2) ◽  
pp. 107-118 ◽  
Author(s):  
Farzad Bazdidi-Tehrani ◽  
Mohammad Hatami ◽  
Ahmad Abouata
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Vortex Rings ◽  
Mean Velocity ◽  
Synthetic Jet Actuator ◽  
Velocity Magnitude ◽  
Wall Boundary Conditions ◽  
Significant Difference

The present work provides the computations of unsteady 3D synthetic jet ejected into a quiescent ambient. The [Formula: see text] turbulence model is employed for numerical simulations of flow field and the problem is considered under incompressible and axisymmetric assumptions. The pressure-implicit with splitting of operators algorithm is used for coupling of continuity and momentum equations. In order to accurately simulate the synthetic jet actuator, the dynamic mesh method is employed to model the flow field. In different simulations, pressure inlet, pressure outlet and wall boundary conditions at the orifice outlet of the synthetic jet are investigated. Changes in the boundary conditions at the orifice outlet affect the flow field such that mean velocity magnitude is higher for unconfined synthetic jets than confined ones. Moreover, form of vortex rings is dissimilar for confined and unconfined jets. Also, the actuator is modelled with two types of inlet boundary conditions, namely, moving piston and moving diaphragm boundaries. Results show that they have no significant difference and can be used interchangeably.

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