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Scalings for rectangular synthetic jet trajectory in a turbulent boundary layer

Scalings for rectangular synthetic jet trajectory in a turbulent boundary layer
Scalings for rectangular synthetic jet trajectory in a turbulent boundary layer
Synthetic jet actuators remain coveted components in flow control applications as the convection of vortex rings induces a redistribution of the momentum in a boundary layer although the net mass flux remains zero. The ability to predict the trajectory of these vortical structures, and subsequently the jet, is critical for efficient and targeted usage of such actuators. In this investigation, a synthetic jet is issued into a zero pressure gradient turbulent boundary layer from rectangular orifices with aspect ratios 3, 6 and 12 over a range of actuation frequencies and velocity ratios, with the flow field captured through particle image velocimetry measurements. An assessment of the trajectories culminates in scaling characteristics which encapsulate the aspect ratio, the momentum ratio between the jet and the cross-flow and the Strouhal number. However, the scaling mechanism is found to be sensitive to constraints which include the interaction between successive vortex pairs and the various regions of the flow field where the degree of interaction of the jet with the cross-flow changes. By redefining the threshold between the near-field, transitioning and far-field regions and accounting for vortex interaction, we observe the relevant non-dimensional parameters describing the scaling to vary. Additionally, together with cross-flow properties, variation in the orifice dimensions and actuation parameters enable the exact form of the Strouhal number for each combination of constraints to be determined. Under conditions of no vortex interaction, synthetic jets are found to follow identical trajectories provided the ratio of total momentum between the jet and the cross-flow remains the same, irrespective of the actuation frequency or Reynolds number of the incoming flow.
jets, turbulent boundary layers
0022-1120
Jankee, Girish K.
ae50bc76-d591-4ec8-9a60-421b2336f5a7
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
Jankee, Girish K.
ae50bc76-d591-4ec8-9a60-421b2336f5a7
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052

Jankee, Girish K. and Ganapathisubramani, Bharathram (2021) Scalings for rectangular synthetic jet trajectory in a turbulent boundary layer. Journal of Fluid Mechanics, 915, [A57]. (doi:10.1017/jfm.2020.1142).

Record type: Article

Abstract

Synthetic jet actuators remain coveted components in flow control applications as the convection of vortex rings induces a redistribution of the momentum in a boundary layer although the net mass flux remains zero. The ability to predict the trajectory of these vortical structures, and subsequently the jet, is critical for efficient and targeted usage of such actuators. In this investigation, a synthetic jet is issued into a zero pressure gradient turbulent boundary layer from rectangular orifices with aspect ratios 3, 6 and 12 over a range of actuation frequencies and velocity ratios, with the flow field captured through particle image velocimetry measurements. An assessment of the trajectories culminates in scaling characteristics which encapsulate the aspect ratio, the momentum ratio between the jet and the cross-flow and the Strouhal number. However, the scaling mechanism is found to be sensitive to constraints which include the interaction between successive vortex pairs and the various regions of the flow field where the degree of interaction of the jet with the cross-flow changes. By redefining the threshold between the near-field, transitioning and far-field regions and accounting for vortex interaction, we observe the relevant non-dimensional parameters describing the scaling to vary. Additionally, together with cross-flow properties, variation in the orifice dimensions and actuation parameters enable the exact form of the Strouhal number for each combination of constraints to be determined. Under conditions of no vortex interaction, synthetic jets are found to follow identical trajectories provided the ratio of total momentum between the jet and the cross-flow remains the same, irrespective of the actuation frequency or Reynolds number of the incoming flow.

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Scalings for synthetic jet trajectory in crossflow_accepted - Accepted Manuscript
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Accepted/In Press date: 10 December 2020
e-pub ahead of print date: 16 March 2021
Published date: 25 May 2021
Keywords: jets, turbulent boundary layers

Identifiers

Local EPrints ID: 445604
URI: http://eprints.soton.ac.uk/id/eprint/445604
ISSN: 0022-1120
PURE UUID: d35c0f98-6b5d-4361-9dc4-a12905e126cc
ORCID for Girish K. Jankee: ORCID iD orcid.org/0000-0002-9178-1070
ORCID for Bharathram Ganapathisubramani: ORCID iD orcid.org/0000-0001-9817-0486

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Date deposited: 18 Dec 2020 17:30
Last modified: 26 Nov 2021 05:20

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Contributors

Author: Girish K. Jankee ORCID iD

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