Mechanism of wake-induced flow dynamics in tandem flapping foils: Effect of the chord and gap ratios on propulsion

Joshi, Vaibhav; Mysa, Ravi Chaithanya

doi:10.1063/5.0057827

Cited by 25 publications

(8 citation statements)

References 67 publications

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“…Major interactions have been shown in Fig. 9, the details of which can be found in Joshi et al 27 . To summarize, a constructive interaction (same-signed) on the upper surface (Interaction-1 or I-1) and a destructive one (opposite-signed) on the lower surface (Interaction-4 or I-4) of the foil favors the generation of thrust during the downstroke.…”

Section: Propulsive Performance In Frequency-pitch Amplitude Parametr...mentioning

confidence: 86%

“…• The behavior of the propulsive performance of the tandem system of foils can be explained by examining the vortex interaction patterns and linking it with favorable and unfavorable conditions for thrust generation provided in the literature 27 .…”

Section: Discussionmentioning

confidence: 99%

“…The nonlinear Navier-Stokes equations are solved by the Newton-Raphson iterative technique. The coupling between the flow equations and the moving mesh framework is carried out in a partitioned iterative manner, the details of which can be found in the works 27,50 . The above formulation has been verified and validated, consisting of mesh convergence and time convergence studies in the earlier work 27 for the single and tandem flapping foils and will not be discussed in the present work for brevity.…”

Section: Numerical Frameworkmentioning

confidence: 99%

“…In the tandem configuration of flapping foils, the downstream foil interacts with the wake of the upstream foil. The effect of the gap between the flapping foils on the propulsive performance of the downstream foil was investigated in detail in Joshi et al 27 for gap ratios of g/c d ∈ [1,14] for tandem foils of same chord length, i.e., c u /c d = 1. Various mechanisms of vortex interactions were proposed and categorized into constructive and destructive interactions, which have been noticed in the literature [53][54][55] as well.…”

Section: Propulsive Performance In Frequency-pitch Amplitude Parametr...mentioning

confidence: 99%

“…A numerical study by Pan and Dong 25 at Re = 1000 identified that an increase in the streamwise spacing in a school of flapping foils reduced the influence of the lateral neighbors on the performance of the flapping foils. Recently, Joshi and Mysa 26,27 studied the effect of gap and the chord sizes for the tandem foils on the propulsion at Re = 1100. The mechanism of wake interaction with the downstream foil was identified and studied in detail.…”

Section: Introductionmentioning

confidence: 99%

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Effect of combined heaving and pitching on propulsion of single and tandem flapping foils

Hegde¹,

Gurugubelli²,

Joshi³

2022

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Flow dynamics across flapping foils in tandem arrangement at Reynolds number of Re = 1100 has been numerically investigated in the present study. The kinematic motion of the foils consists of sinusoidal heaving and pitching motion. The two-dimensional computation has been carried out through the arbitrary Lagrangian-Eulerian (ALE) moving mesh based algorithm with the variational modeling of the incompressible flow equations. The effects of the heave amplitude, pitch amplitude and the flapping frequency on the propulsive performance have been comprehensively studied for a single as well as tandem system of foils at two gaps of 4 and 7 times the downstream foil's chord length. It is found that the effective angle of attack, effective projected area, type of vortex interaction and the timing of the interaction during the downstroke of the flapping motion influence the propulsive performance. Increasing the heave amplitude of the upstream foil leads to an increase in the average thrust generated by the downstream foil for the gap of 7, while the opposite effect is observed for gap of 4. The propulsion of the downstream foil increases monotonically with the heave amplitude of the downstream foil. Upstream foil's pitch amplitude is noticed to have a minor effect on the performance of the downstream foil, while an increase in the pitch amplitude of the downstream foil increases the thrust for larger gap between the foils. The study of the propulsive performance in the frequency-pitch amplitude parametric space for the tandem foils has been performed for the first time, where a more complex behavior is observed. The trends in the thrust coefficient and the propulsive efficiency are corroborated by the study of various vortex interaction mechanisms leading to favorable or unfavorable thrust generating conditions. Finally, the three-dimensional flapping dynamics of the tandem configuration is demonstrated, where no spanwise wake structures are noted, indicating the wake interaction to be inherently two-dimensional.

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Section: Propulsive Performance In Frequency-pitch Amplitude Parametr...mentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%