Towards the Design of Synthetic-jet Actuators for Full-scale Flight Conditions

Tang, Hui; Zhong, Shan; Jabbal, Mark; Garcillan, Luis; Guo, Fushui; Wood, N. J.; Warsop, Clyde

doi:10.1007/s10494-006-9061-3

Cited by 50 publications

(16 citation statements)

References 21 publications

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“…We also relax the assumption that the flow is fully developed throughout. This results in a criterion for the onset of Helmholtz resonance and an estimate of the Helmholtz frequency that are different from those published in [16,22].…”

Section: Introductioncontrasting

confidence: 57%

“…Perversely, it turns out that the very cavity and orifice dimensions that are optimum for actuator performance in terms of maximizing mass flux are close to optimum for Helmholtz resonance [16]. This is true also for synthetic-jet actuators [13,16,21,22].…”

Section: Introductionmentioning

confidence: 93%

“…However, it was assumed that the orifice flow was fully developed quasi-steady Poiseuille flow (see also [22]). This is a poor assumption because in the present paper we show that the Helmholtz frequency is well above the limit of validity for quasi-steady Poiseuille theory.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Is Helmholtz Resonance a Problem for Micro-jet Actuators?

Lockerby

Carpenter

Davies

2007

Flow Turbulence Combust

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A theoretical analysis is described that determines the conditions for Helmholtz resonance for a popular class of self-contained microjet actuator used in both synthetic-and pressure-jump (pulse-jet) mode. It was previously shown that the conditions for Helmholtz resonance are identical to those for optimizing actuator performance for maximum mass flux. The methodology is described for numerical-simulation studies on how Helmholtz resonance affects the interaction of active and nominally inactive micro-jet actuators with a laminar boundary layer. Two sets of numerical simulations were carried out. The first set models the interaction of an active actuator with the boundary layer. These simulations confirm that our criterion for Helmholtz resonance is broadly correct. When it is satisfied we find that the actuator cannot be treated as a predetermined wall boundary condition because the interaction with the boundary layer changes the pressure difference across the exit orifice thereby affecting the outflow from the actuator. We further show that strong inflow cannot be avoided even when the actuator is used in pressurejump mode. In the second set of simulations two-dimensional Tollmien-Schlichting waves, with frequency comparable with, but not particularly close to, the Helmholtz resonant frequency, are incident on a nominally inactive micro-jet actuator. The simulations show that under these circumstances the actuators act as strong sources of 3D Tollmien-Schlichting waves. It is surmised that in the real-life aeronautical applications with turbulent boundary layers broadband disturbances of the pressure field, including acoustic waves, would cause nominally inactive actuators, possibly including pulsed jets, to act as strong disturbance sources. Should this be true it Flow Turbulence Combust (2007) 78:205-222 would probably be disastrous for engineering applications of such massless microjet actuators for flow control.

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Section: Introductioncontrasting

confidence: 57%

Section: Introductionmentioning

confidence: 93%

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Is Helmholtz Resonance a Problem for Micro-jet Actuators?

Lockerby

Carpenter

Davies

2007

Flow Turbulence Combust

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“…In recent years, more research attention has been given to synthetic jets due to their potential for flow separation control in aerospace applications [6][7][8][9]. A typical synthetic jet actuator consists of a small cavity with an oscillating diaphragm at its bottom side and an orifice plate at the opposite side, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Vortex Roll-Up Criterion for Synthetic Jets

2009

Self Cite

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In this paper, both theoretical analysis and numerical simulations are undertaken to study the parameters that affect the strength of vortex roll-up of synthetic jets. A dimensional analysis reveals that the dimensionless vorticity of vortex roll-up produced by an orifice flow depends on the dimensionless stroke length, Stokes number, and the ratio between the orifice diameter and the thickness of the Stokes layer. Based on the results from a fully developed oscillating laminar pipe flow, the Stokes number is found to play an important role in determining the thickness of the Stokes layer inside the orifice and hence the shape of the velocity profile. Results from the numerical simulations confirm that the Stokes number also determines the strength of vortex roll-up of a synthetic jet issued from an orifice of a finite depth, for the same reason. Finally, a parameter map, which marks the three different regimes of synthetic jets (classified as no jet, jet formation without vortex roll-up, and jet formation with vortex roll-up) is produced based on the numerical simulation results. It is shown that for the synthetic jet actuator used in the present study, a minimum Stokes number of about 8.5 is required to ensure the occurrence of an appreciable vortex roll-up at a dimensionless stroke length greater than 4. In addition, a very low Stokes number can also suppress the formation of synthetic jets. This study provides a further understanding of the behavior of synthetic jets in quiescent conditions, which will be useful for designing more effective synthetic jet actuators in which vortex roll-up is desired. Nomenclature D c = cavity diameter, m D o = orifice diameter, m f = diaphragm oscillation frequency, Hz H = cavity depth, m h = orifice depth, m L = dimensionless stroke length, L o =D o L o = stroke length, U o T, m Re L = Reynolds number based on the stroke length, U o L o = r = radial coordinate measured from the center of the diaphragm or orifice, m S = Stokes number, 2fD 2 o = p T = period of diaphragm oscillation cycle, s t = time, s U o = time-averaged jet blowing velocity over the entire cycle, m=s u= instantaneous jet exit velocity, m=s x = axial coordinate measured from the orifice exit, m = peak-to-peak displacement at the center of diaphragm, m = molecular kinematic viscosity, m 2 =s

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“…Therefore, many authors concentrated their efforts on location and prediction of the SJ actuator resonances (see e.g. [32][33][34][35][36][37][38][39][40][41][42][43][44]). Having a SJ actuator operating at a resonance frequency, there still exist other ways how to enhance its exploitable outlet quantities such as volumetric flux, momentum or kinetic energy fluxes.…”

Section: Introductionmentioning

confidence: 99%

Comparison of synthetic jet actuators based on sharp-edged and round-edged nozzles

Kordík

Trávníček

2017

EPJ Web Conf.

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Abstract. Axisymmetric synthetic jet actuators based on a loudspeaker and on two types of flanged nozzles were tested and compared experimentally. The first type of the nozzle was a sharp-edged circular hole. The second one had a special design with fillets at inner and outer nozzle exit and with a small step in the middle of the nozzle. The function of the step was to prevent the flow reattachment during the extrusion stroke. The actuators with the two types of nozzles were operated at resonance and were compared first qualitatively using a simple phase locked flow visualization. Then the hot-wire anemometer was used to measure velocity distributions along nozzle axis and velocity profiles at the nozzle exit. Comparison of the nozzles was based on evaluation of the characteristic velocity and integral quantities (volumetric, momentum, and kinetic energy fluxes). It was found out that these quantities, which were evaluated at the nozzle exit, differ substantially for both nozzles. On the other hand the velocity flow field in farther distances from the nozzle exit area did not exhibit such prominent differences.

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Towards the Design of Synthetic-jet Actuators for Full-scale Flight Conditions

Cited by 50 publications

References 21 publications

Is Helmholtz Resonance a Problem for Micro-jet Actuators?

Is Helmholtz Resonance a Problem for Micro-jet Actuators?

Vortex Roll-Up Criterion for Synthetic Jets

Comparison of synthetic jet actuators based on sharp-edged and round-edged nozzles

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