Visualization of synthetic jet formation in air

Trávníček, Z.; Broučková, Zuzana; Kordík, Jozef; Vít, Tomáš

doi:10.1007/s12650-015-0273-2

Cited by 19 publications

(9 citation statements)

References 48 publications

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“…The problem of the SJ existence threshold is known as the SJ formation criterion (Timchenko et al 2004;Holman et al 2005;Shuster and Smith 2007;Zhou et al 2009;Trávníček et al 2012a). The closely related topic of SJ flow field regimes was investigated in recent experimental studies (Trávníček et al 2014;McGuinn et al 2013;Xia and Zhong 2012a).…”

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confidence: 99%

Visualization study of hybrid synthetic jets

Broučková

Trávníček

2014

J Vis

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A synthetic jet (SJ) is a fluid flow that is created from an oscillatory process of suction and blowing. A hybrid synthetic jet (HSJ) combines this principle with fluidic pumping through a valveless pump. The present study addresses round HSJs issuing into quiescent surroundings from an actuator orifice 8 mm in diameter. For comparison purposes, a common (zero-net-mass-flux) SJ is used. The working fluid is air, and the maximum Reynolds numbers are 11,000 and 9,000 for HSJs and SJs, respectively. The following five experimental methods are employed: flow visualization using a smoke wire technique, velocity measurements using a hot-wire anemometer, velocity measurements using a Pitot tube, impedance measurements of the actuators, and measurements of the jet momentum using precision scales. Flow visualization demonstrates phase-locked flow fields. The first resonance frequencies are theoretically derived to be 79 and 98 Hz for an SJ and HSJ, respectively. These values are confirmed by all of the experimental methods used. The results demonstrate the advantages of HSJs. The tested HSJ achieves a 24 % higher pumped volume flow rate in comparison to the SJ at a maximum volumetric efficiency of 33 %. Moreover, the overall energy efficiency of the HSJ actuator is 1.8 times higher than that of the SJ actuator. These promising HSJ features, including significantly higher efficiencies, can be useful for various heat transfer applications such as the cooling of highly loaded electronic devices.

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confidence: 99%

Visualization study of hybrid synthetic jets

Broučková

Trávníček

2014

J Vis

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“…The dimension of the computational domain was set according to the experimental measurement [3], where the jet is created in the cylindrical domain of 100 mm length and 60 mm in diameter, orifice diameter is 3.18 mm. Figure 1 shows instantaneous centerline streamwise velocity for four typical phases of synthetic jet work at L = 1.174 compared with hot-wire anemometry measurement [3]. The good agreement of computational data with measurement is observed.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…Instantaneous streamwise velocity at jet centerline for the case with L = 1.174; solid line corresponds to numerical computation and dots are from hot-wire anemometry measurement[3].…”

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Dynamic Mode Decomposition of Axisymmetric Synthetic Jet on the Limit of Its Formation

Hyhlik¹

2016

World Congress on Mechanical, Chemical, and Material Engineering

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The modal decomposition of two flow fields related to axisymmetric synthetic jet creation has been done by using Dynamic Mode Decomposition (DMD). Both the case without synthetic jet formation defined by nondimensional stroke length L = 0.615 a the case with synthetic jet creation which is defined by L = 1.174 are studied. The analyses are based on the data by using ANSYS Fluent solver. Numerical results are validated by hot-wire anemometry data measured along the jet centerline. The vortex identification is based on residual vorticity, which allows identifying of the regions where continuum particle rotates. It is shown that in the case of L = 1.174 exist travelling vortex which diminishes two diameters behind orifice and this case is very close to the case of a synthetic jet without vortex roll-up. It is possible to expect that the vortex path would be shorter with decreasing stroke length until the vortex completely vanishes and the jet is not synthetized. The travelling vortex speed is measured by using vortex tracking and by using wavelength measured from DMD modes. It is shown that the vortex is travelling not only in the axial direction, but there is also a radial component which leads to the change of vortex ring size. The evaluation of travelling vortex speed leads to not typical behaviour because of a non-monotonous character of the vortex speed. It is shown that the vortex speed has an increasing-decreasing behaviour in the case of nondimensional stroke length L = 1.174.

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“…This technique has been used for other estimations, such as the mean velocity field [19][20][21][22][23] and its fluctuations [15,19,24], the mean vorticity [18,21,23,25], the turbulence intensity [19,22], the Reynolds stress [20,26] and velocity profiles. Aside from the visualization techniques, hot-wire anemometry (HWA) has been also used to estimate the velocity of the flow [11,12,19,21,23,[27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Momentum transfer in the outflow cycle of a Synthetic jet: Comparison between a developed flow and an LE model

Hernández-Sánchez¹,

Orduña‐Bustamante²,

Velasco-Segura³

2021

Preprint

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In the literature, flows produced by synthetic jets (SJ) have been studied extensively through experiments and numeric simulations. The essential physics of such a complex system has been simplified successfully to Lumped-element models in a wide range of conditions. LE models effectively predict the pressure in the cavity and the velocity in the neck of SJ. But, this does not comprise the complete dynamics of SJ. As soon as the flow starts separating from the neck of the SJ device, vortices and jets form at some distance downstream. These structures are the result of loosening the flow boundaries. Despite such a dramatic change, predictions of LE models remain unverified by measurements of the fully developed jet. We compared predictions of momentum transfer using an LE model with measurements of size and velocity of a fully developed jet/vortex detached from an SJ. Our SJ device operated with air as an active fluid. Comparing measurements and predictions, we found a constant difference for the higher sound pressures. However, the predictions and the measurements follow similar trends. Additionally, we found that the decay rate of the flow regime given by the relationship between the Reynolds and the Strouhal numbers differs significantly when the flow is studied within the neck and downstream the cavity.

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Visualization of synthetic jet formation in air

Cited by 19 publications

References 48 publications

Visualization study of hybrid synthetic jets

Visualization study of hybrid synthetic jets

Dynamic Mode Decomposition of Axisymmetric Synthetic Jet on the Limit of Its Formation

Momentum transfer in the outflow cycle of a Synthetic jet: Comparison between a developed flow and an LE model

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