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Effects of multijet coupling on propulsive performance in underwater pulsed jets

Effects of multijet coupling on propulsive performance in underwater pulsed jets Despite the importance of pulsed jets for underwater propulsion, the effect of multiple-jet interactions remains poorly understood. We experimentally investigate how interactions between parallel jets in a pulsed-jet thruster affect the thruster's propulsive performance. Using high-speed fluorescence imaging, we investigate the mutual influence of two pulsed jets under conditions relevant to low-speed maneuvering in a vehicle ( Re ≈ 350 , L / D ≤ 2 ). Thrust production and propulsive efficiency are evaluated for different nozzle spacings using a new force estimation technique based on the fluorescence data. This analysis reveals that compared to noninteracting jets, the efficiency and thrust generated by the pair of interacting jets can fall by as much as 10% when the jets are brought into close proximity. Empirically, the thrust T falls off with the nondimensional jet spacing Δ ̃ as T = T ∞ ( 1 − C o Δ ̃ − 6 ) for a thrust coupling coefficient C o = 2.04 ± 0.11 . Finally, we predict this dependence of thrust on spacing using a model that relates the thrust and efficiency drop to streamline curvature and vortex induction at the nozzles. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review Fluids American Physical Society (APS)

Effects of multijet coupling on propulsive performance in underwater pulsed jets

Effects of multijet coupling on propulsive performance in underwater pulsed jets

Physical Review Fluids , Volume 1 (3): 12 – Jul 19, 2016

Abstract

Despite the importance of pulsed jets for underwater propulsion, the effect of multiple-jet interactions remains poorly understood. We experimentally investigate how interactions between parallel jets in a pulsed-jet thruster affect the thruster's propulsive performance. Using high-speed fluorescence imaging, we investigate the mutual influence of two pulsed jets under conditions relevant to low-speed maneuvering in a vehicle ( Re ≈ 350 , L / D ≤ 2 ). Thrust production and propulsive efficiency are evaluated for different nozzle spacings using a new force estimation technique based on the fluorescence data. This analysis reveals that compared to noninteracting jets, the efficiency and thrust generated by the pair of interacting jets can fall by as much as 10% when the jets are brought into close proximity. Empirically, the thrust T falls off with the nondimensional jet spacing Δ ̃ as T = T ∞ ( 1 − C o Δ ̃ − 6 ) for a thrust coupling coefficient C o = 2.04 ± 0.11 . Finally, we predict this dependence of thrust on spacing using a model that relates the thrust and efficiency drop to streamline curvature and vortex induction at the nozzles.

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Publisher
American Physical Society (APS)
Copyright
©2016 American Physical Society
Subject
ARTICLES; Vortex dynamics
ISSN
2469-990X
eISSN
2469-990X
DOI
10.1103/PhysRevFluids.1.034501
Publisher site
See Article on Publisher Site

Abstract

Despite the importance of pulsed jets for underwater propulsion, the effect of multiple-jet interactions remains poorly understood. We experimentally investigate how interactions between parallel jets in a pulsed-jet thruster affect the thruster's propulsive performance. Using high-speed fluorescence imaging, we investigate the mutual influence of two pulsed jets under conditions relevant to low-speed maneuvering in a vehicle ( Re ≈ 350 , L / D ≤ 2 ). Thrust production and propulsive efficiency are evaluated for different nozzle spacings using a new force estimation technique based on the fluorescence data. This analysis reveals that compared to noninteracting jets, the efficiency and thrust generated by the pair of interacting jets can fall by as much as 10% when the jets are brought into close proximity. Empirically, the thrust T falls off with the nondimensional jet spacing Δ ̃ as T = T ∞ ( 1 − C o Δ ̃ − 6 ) for a thrust coupling coefficient C o = 2.04 ± 0.11 . Finally, we predict this dependence of thrust on spacing using a model that relates the thrust and efficiency drop to streamline curvature and vortex induction at the nozzles.

Journal

Physical Review FluidsAmerican Physical Society (APS)

Published: Jul 19, 2016

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