Effect of Orifice Geometry on Synthetic Jet Evolution

Lindstrom, Annika; Amitay, Michael

doi:10.2514/1.j058135

Cited by 11 publications

(7 citation statements)

References 22 publications

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“…Further developments led to dedicated lumped-element models (LEM) of complex devices, with more cavities and/or orifices [30,31]. The flow field generated by unconventional SJ actuators, with noncircular orifices or multi-slot and multi-cavity characteristics are still object of current research [32][33][34], and these studies could be the basis for new LEMs. On the contrary, there are no LEMs for the synthetic jets in crossflow, which led the researchers to rely to empirical models or trial-and-error techniques for the design of the actuators.…”

Section: Introductionmentioning

confidence: 99%

Receptivity to synthetic jet actuation in boundary layer flows

Palumbo

Semeraro

Robinet

et al. 2020

AIAA Scitech 2020 Forum

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The flow field generated by the interaction between a zero-net-mass-flux (synthetic) jet and a boundary layer crossflow is studied in the present work. The investigation consists in Direct Numerical Simulations (DNS) of the resulting unsteady field, for various boundary layer Reynolds numbers Re δ * 0 and jet reduced frequencies F + . In particular, the actuation frequency is chosen in order to match the unstable (or less stable) frequency of the incoming crossflow. The analysis is focused on the near-field behaviour of the flow, i.e. next to the jet exit orifice, and in the downstream region. It has been found that the presence of the jet deeply modifies the boundary layer transition. Indeed, the instantaneous flow field is characterized by the presence of unsteady, hairpin-like vortical structures, similar to the ones generated by localized roughness elements. Moreover, streaky structures can be detected in the time-averaged flow field. The overall behaviour of the flow field (investigated via time-averaged boundary layer integral parameters) allows to state that early transition can be achieved by using SJ devices. This work is part of a wider project which aims at realizing a reduced-order modeling of a piezo-driven synthetic jet in crossflow, based on simulations and lumped element modeling of the actuator.

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Section: Introductionmentioning

confidence: 99%

Receptivity to synthetic jet actuation in boundary layer flows

Palumbo

Semeraro

Robinet

et al. 2020

AIAA Scitech 2020 Forum

View full text Add to dashboard Cite

show abstract

“…From Equation (21) it can be seen that the product u rms, LE d n in Equation ( 28) is related to U v D v in Equation ( 29) by a factor √ 2. However, even if the definitions are similar, the Reynolds numbers refer to different phenomena.…”

Section: Reynolds and Strouhal Numbersmentioning

confidence: 99%

“…In synthetic jets, PIV has been widely used to estimate the instantaneous velocity fields [15,18]. 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%

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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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“…Both experimental and numerical studies have been conducted to explore the effect of various geometrical parameters along with the geometrical modifications such as shape, and size of the cavity, and orifice of the synthetic jet [10][11][12][13][14][15][16]. In the numerical modelling of a synthetic jet, three different actuation mechanisms can be used: a. oscillating velocity inlet boundary condition at the orifice exit [17][18][19][20][21], b. cylinder-piston type motion of the diaphragm [23], or c. membrane type motion of the diaphragm [13,14,22].…”

Section: Introductionmentioning

confidence: 99%

Effect of Strouhal Number and Stokes Number on the Flow Behaviour of an Axisymmetric Synthetic Jet: A Numerical Study

Panda

Gohil

Arumuru

2023

Preprint

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The study focusses on the response of a round synthetic jet (SJ) towards the Strouhal number and Stokes number An SJ is formed by issuing a stream of fluid into a low momentum region with the help of an oscillating boundary. The nature of the jet can be controlled by controlling the actuation frequency and amplitude of oscillation, and these two operating parameters are associated with the Strouhal number (St) and Stokes number (S) of the jet respectively. These non-dimensional numbers play a significant role in the effective utilization of SJs in controlling the flow, and heat transfer. The purpose of this article is to numerically investigate the flow behaviour of an SJ issued into a quiescent medium based on these two non-dimensional parameters. For analysis, a two-dimensional axisymmetric SJ is modelled using a finite volume solver integrated with openFOAM. The oscillating boundary resembles the motion of a diaphragm, and deforming mesh is enforced in the flow domain. Range of parameters within which the jet is operated: St – 0.13 to 0.16, and S – 23 to 36. The study highlights the strength, and spreading of the SJ based on St and S. Effect of St and S on the mean jet parameters such as centreline velocity decay, jet half-width, jet momentum flux, and entrainment rate are studied in detail, which can enhance the idea of operating an SJ effectively for better heat transfer and flow control. Time evolution of saddle point, and mean jet centreline decay profiles suggest the spacing between the orifice and a heated plate to be maintained for effective heat transfer. The jet should be operated at a low Strouhal number and high Stokes number for better impingement on a heated plate to be cooled. Low Strouhal number should be maintained to get high-velocity output, which is desirable for better flow control. These results are useful for the effective utilization of SJs for heat transfer, flow control, and other similar applications.

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Effect of Orifice Geometry on Synthetic Jet Evolution

Cited by 11 publications

References 22 publications

Receptivity to synthetic jet actuation in boundary layer flows

Receptivity to synthetic jet actuation in boundary layer flows

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

Effect of Strouhal Number and Stokes Number on the Flow Behaviour of an Axisymmetric Synthetic Jet: A Numerical Study

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