A Synthetic Jet Issuing From a Bio-Inspired Actuator With an Oscillating Nozzle Lip

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Zdeněk Trávníček ◽  
Zuzana Broučková
Keyword(s):  
Momentum Flux ◽  
Flux Measurement ◽  
Experimental Methods ◽  
Synthetic Jet ◽  
Operating Frequency ◽  
Working Fluid ◽  
Hot Wire ◽  
Synthetic Jet Actuator ◽  
Novel Variant ◽  
Flexible Diaphragm

A novel variant of a synthetic jet actuator (SJA) has been designed, manufactured, and tested. The novelty consists in a bio-inspired nozzle whose oscillating lip is formed by a flexible diaphragm rim. The working fluid is air, and the operating frequency is 65 Hz. The proposed SJA was tested by three experimental methods: phase-locked visualization of the nozzle lips, hot-wire anemometry, and momentum flux measurement using a precision scale. The results demonstrate advantages of the proposed SJA, namely, an increase in the momentum flux by 18% compared with that of a conventional SJA.

Novel Fluidic Diode for Hybrid Synthetic Jet Actuator

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Jozef Kordík ◽  
Zdeněk Trávníček
Keyword(s):  
Pressure Drop ◽  
Resonant Frequency ◽  
Synthetic Jet ◽  
Volumetric Efficiency ◽  
Operating Frequency ◽  
Working Fluid ◽  
Hot Wire ◽  
Synthetic Jet Actuator ◽  
Fluidic Diode ◽  
Resonance Curves

This paper deals with a new design of a hybrid synthetic jet actuator (HSJA), which is based on a novel fluidic diode. Two fluidic diodes were tested using pressure-drop measurements with air as the working fluid, and their diodicities were evaluated. A greater diodicity was achieved with the new diode design. Two outlet nozzles of the HSJA were tested (shorter and longer), and the velocity resonance curves were evaluated using hot-wire measurements at the outlets of the nozzles. Volumetric efficiency of the HSJA was evaluated as function of the operating frequency. The greatest efficiency was achieved at the second resonant frequency of the actuator with the longer nozzle.

Characterization of Impingement Heat/Mass Transfer to the Synthetic Jet Generated by a Biomimetic Actuator

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Zdeněk Trávníček ◽  
Zuzana Broučková
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Mass Transfer Rate ◽  
Jet Impingement ◽  
Flux Measurement ◽  
Impinging Jets ◽  
Synthetic Jet ◽  
Working Fluid ◽  
Naphthalene Sublimation Technique ◽  
Flexible Diaphragm

Two biomimetic synthetic jet (SJ) actuators were designed, manufactured, and tested under conditions of a jet impingement onto a wall. Nozzles of the actuators were formed by a flexible diaphragm rim, the working fluid was air, and the operating frequencies were chosen near the resonance at 65 Hz and 69 Hz. Four experimental methods were used: phase-locked visualization of the oscillating nozzle lips, jet momentum flux measurement using a precision scale, hot-wire anemometry, and mass transfer measurement using the naphthalene sublimation technique. The results demonstrated possibilities of the proposed actuators to cause a desired heat/mass transfer distribution on the exposed wall. It was concluded that the heat/mass transfer rate was commensurable with a conventional continuous impinging jets (IJs) at the same Reynolds numbers.

scholarly journals Novel Nozzle Shapes for Synthetic Jet Actuators Intended to Enhance Jet Momentum Flux

Actuators ◽  
2018 ◽  
Vol 7 (3) ◽  
pp. 53 ◽  
Author(s):  
Jozef Kordík ◽  
Zdeněk Trávníček
Keyword(s):  
Momentum Flux ◽  
Element Model ◽  
Velocity Profiles ◽  
Input Power ◽  
Synthetic Jet ◽  
Stroke Length ◽  
Synthetic Jet Actuator ◽  
Pressure Loss Coefficient ◽  
Nozzle Plate ◽  
Lumped Element Model

An axisymmetric synthetic jet actuator based on a loudspeaker and five types of flanged nozzles were experimentally tested and compared. The first (reference) type of nozzle was a common sharp-edged circular hole. The second type had a rounded lip on the inside. The third nozzle type was assembled from these two types of nozzles—it had a rounded lip on the inside and straight section on the outside. The fourth nozzle was assembled using orifice plates such that the rounded lips were at both inner and outer nozzle ends. The last nozzle was equipped with an auxiliary nozzle plate placed at a small distance downstream of the main nozzle. The actuators with particular nozzles were tested by direct measurement of the synthetic jet (SJ) time-mean thrust using precision scales. Velocity profiles at the actuator nozzle exit were measured by a hot-wire anemometer. Experiments were performed at eight power levels and at the actuator resonance frequency. The highest momentum flux was achieved by the nozzle equipped with an auxiliary nozzle plate. Namely, an enhancement was approximately 31% in comparison with an effect of the reference nozzle at the same input power. Furthermore, based on the cavity pressure and the experimental velocity profiles, parameters for a lumped element model (mass of moving fluid and pressure loss coefficient) were evaluated. These values were studied as functions of the dimensionless stroke length.

Effects of Operating Frequency of a Synthetic Jet and Cross Flow Velocity on the Heat Transfer Enhancement in a Micro-Channel

2013 ◽  
Author(s):  
Mark E. Zschirnt ◽  
Ann Lee ◽  
Guan H. Yeoh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Cross Flow ◽  
Synthetic Jet ◽  
Operating Frequency ◽  
Micro Channel ◽  
Transfer Enhancement ◽  
Synthetic Jet Actuator ◽  
Micro Channels

Current devices have been reported to approach 1 MW/m2 so that current heat dissipation devices will not be able to cope with increasing heat flux. It has therefore been proposed that in order to manage the ever-increasing heat rejection demands, it will be necessary to have cooling fluid flowing through micro-channels in the microchip itself. Since laminar flow is likely to result for reasonable pressure drops in these micro-channels, the heat transfer rate will need to be enhanced if this approach is to be successfully used. Synthetic jets, which are the main focus of this research, generate vortex structures which disrupt the flow. They have, therefore, been proposed as a means of providing mixing, thereby augmenting the heat transfer potential of the fluid in the micro-channel. A two-dimensional computational model has been developed to investigate the cooling effect of a synthetic jet interacting with a turbulent cross-flow in a micro-channel. Validation of the hydrodynamics feature of the flow was done by comparing numerical results against existing experimental results. A parametric study was performed on a fixed geometry by using a constant wall temperature to investigate the effect of operating frequency of the synthetic jet actuator coupling with different flow rates in the micro-channel. The operating frequencies of the jet were simulated at 1000 Hz, 1500 Hz and 2000 Hz while the cross flows vary from 0 to 10 m/s. In general, the flow structures in the micro-channel were shown to be greatly disrupted when the synthetic jet actuator was turned on. However, the heat transfer enhancement due to the operation of the synthetic jet reduces as the cross flow increases. The frequency of the diaphragm oscillation has a large influence on the distance between the adjacent vortices and therefore on the average flow rate in the micro-channel. The near wall Nusselt Number was calculated in order to compare the effects of operating frequency of the jet and flow rate in the micro-channel. The jet Reynolds number was increased by 50% when the actuator frequency was increased from 1000 Hz to 1500 Hz while the heat transfer enhancement was increased by 21%. Further increment of actuator frequency from 1000 Hz to 2000 Hz resulted in a doubled jet Reynolds number while the heat transfer enhancement was improved by 66%. The heat transfer enhancement showed greater improvement when the actuator operating at 2000 Hz.

scholarly journals Cephalopod‐Inspired Swimming Robot Using Dielectric Elastomer Synthetic Jet Actuator

2020 ◽  
Vol 22 (4) ◽  
pp. 2070014
Author(s):  
Chao Tang ◽  
Wentao Ma ◽  
Bo Li ◽  
Mingliang Jin ◽  
Hualing Chen
Keyword(s):  
Dielectric Elastomer ◽  
Synthetic Jet ◽  
Synthetic Jet Actuator
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