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Vectoring of parallel synthetic jets: a parametric study

Vectoring of parallel synthetic jets: a parametric study
Vectoring of parallel synthetic jets: a parametric study
The vectoring of a pair of parallel synthetic jets can be described using five dimensionless parameters: the aspect ratio of the slots, the Strouhal number, the Reynolds number, the phase difference between the jets and the spacing between the slots. In the present study, the influence of the latter four on the vectoring behaviour of the jets is examined experimentally, using particle image velocimetry. Time-averaged velocity maps are used to give a qualitative description of the variations in vectoring for a parametric sweep of each of the four parameters independently. A diverse set of vectoring behaviour is observed in which the resulting jet can be merged or bifurcated and either vectored towards the actuator leading in phase or the actuator lagging in phase. Three performance metrics are defined to give a quantitative description of the vectoring behaviour: the included angle between bifurcated branches, the vectoring angle of the total flow and the normalized momentum flux of the flow. Using these metrics, the influence of changes in the Strouhal number, Reynolds number, phase difference and spacing are quantified. Phase-locked maps of the swirling strength are used to track vortex pairs. Vortex trajectories are used to define three Strouhal number regimes for the vectoring behaviour. In the first regime, vectoring behaviour is dominated by the pinch-off time, which is written as function of Strouhal number only. In the second regime, the pinch-off time is invariant and the vectoring behaviour slightly changes with Strouhal number. In the third regime, given by the formation criterion, no synthetic jet is formed. Vortex positions at a single phase, shortly after creation of the lagging vortex pair, are used to propose a vectoring mechanism. This vectoring mechanism explains the observed qualitative and quantitative variations for all four parameters.
0022-1120
467-489
Berk, Tim
6d080fa4-abf6-4a81-9e35-178e8454e755
Ganapathisubramani, Bharath
5e69099f-2f39-4fdd-8a85-3ac906827052
Gomit, Guillaume
81e53723-d65a-46f5-bfc5-4ada63f6c5a9
Berk, Tim
6d080fa4-abf6-4a81-9e35-178e8454e755
Ganapathisubramani, Bharath
5e69099f-2f39-4fdd-8a85-3ac906827052
Gomit, Guillaume
81e53723-d65a-46f5-bfc5-4ada63f6c5a9

Berk, Tim, Ganapathisubramani, Bharath and Gomit, Guillaume (2016) Vectoring of parallel synthetic jets: a parametric study. Journal of Fluid Mechanics, 804, 467-489. (doi:10.1017/jfm.2016.559).

Record type: Article

Abstract

The vectoring of a pair of parallel synthetic jets can be described using five dimensionless parameters: the aspect ratio of the slots, the Strouhal number, the Reynolds number, the phase difference between the jets and the spacing between the slots. In the present study, the influence of the latter four on the vectoring behaviour of the jets is examined experimentally, using particle image velocimetry. Time-averaged velocity maps are used to give a qualitative description of the variations in vectoring for a parametric sweep of each of the four parameters independently. A diverse set of vectoring behaviour is observed in which the resulting jet can be merged or bifurcated and either vectored towards the actuator leading in phase or the actuator lagging in phase. Three performance metrics are defined to give a quantitative description of the vectoring behaviour: the included angle between bifurcated branches, the vectoring angle of the total flow and the normalized momentum flux of the flow. Using these metrics, the influence of changes in the Strouhal number, Reynolds number, phase difference and spacing are quantified. Phase-locked maps of the swirling strength are used to track vortex pairs. Vortex trajectories are used to define three Strouhal number regimes for the vectoring behaviour. In the first regime, vectoring behaviour is dominated by the pinch-off time, which is written as function of Strouhal number only. In the second regime, the pinch-off time is invariant and the vectoring behaviour slightly changes with Strouhal number. In the third regime, given by the formation criterion, no synthetic jet is formed. Vortex positions at a single phase, shortly after creation of the lagging vortex pair, are used to propose a vectoring mechanism. This vectoring mechanism explains the observed qualitative and quantitative variations for all four parameters.

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Vectoring of parallel synthetic jets A Parametric Study.pdf - Accepted Manuscript
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Accepted/In Press date: 22 August 2016
e-pub ahead of print date: September 2016
Published date: October 2016
Organisations: Aerodynamics & Flight Mechanics Group

Identifiers

Local EPrints ID: 399957
URI: http://eprints.soton.ac.uk/id/eprint/399957
ISSN: 0022-1120
PURE UUID: 396d2323-c249-4b93-89e3-298fa586ddd6
ORCID for Bharath Ganapathisubramani: ORCID iD orcid.org/0000-0001-9817-0486

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Date deposited: 06 Sep 2016 11:05
Last modified: 03 Dec 2019 06:34

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