Swimming in density-stratified fluid: study on a flapping foil

Kandel, Prabal; Deng, Jian

doi:10.1088/1748-3190/ac7fd4

Cited by 4 publications

(2 citation statements)

References 40 publications

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“…The present numerical solver has been employed to simulate the stratified flow around both the stationary object (Deng & Kandel 2022) and the moving body (Kandel & Deng 2022; Wang et al. 2023).…”

Section: Methodsmentioning

confidence: 99%

High propulsive performance by an oscillating foil in a stratified fluid

Wang,

Kandel,

Deng

2024

J. Fluid Mech.

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We investigate numerically the propulsion characteristics of an oscillating foil undergoing coupled heave and pitch motion in a linearly density-stratified flow. A parameter space defined by the internal Froude number ( $1 \le Fr \le 10$ ) and the maximum angle of attack ( $5^\circ \le {\alpha _0} \le 30^\circ$ ) is considered in our study. The results demonstrate a significant enhancement in both thrust production and propulsive efficiency due to the stratification influence. Notably, the highest efficiency exceeding $80\,\%$ is achieved under moderate stratification conditions, surpassing the performance observed in a homogeneous fluid. We attribute this optimum performance to the proper match between the stratification effect and foil kinematics, which gives rise to intense vortex interactions and sufficient wave–mean flow interactions in the near wake of the oscillating foil. Consequently, the energy is transferred towards wake structures to form a high-intensity momentum jet in close proximity to the foil's trailing edge, indicating efficient propulsion. Furthermore, we find that the stratifications within the moderate-to-strong transitional regime display a reduced dependence of propulsive efficiency on the maximum angle of attack, primarily due to the delaying and alleviating effects on dynamic-stall events. Such a mechanism enables the oscillating foil to maintain a satisfactory performance by sufficiently high angles of attack without the penalty of stall events. Based on our findings, we propose that animals or artificial vehicles utilising oscillatory propulsion can benefit from the presence of density stratification in the surrounding fluid.

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Section: Methodsmentioning

confidence: 99%

High propulsive performance by an oscillating foil in a stratified fluid

Wang,

Kandel,

Deng

2024

J. Fluid Mech.

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“…The cruising speeds and energy efficiency of the different formations are compared to those of the isolated swimmer. Kandel and Deng [10] study numerically the locomotion of a pitching foil in both homogeneous and stratified fluid flows. They show that the stratification modifies the dynamics of the pitching foil in both its wake structure and the drag/thrust force, as well as its propulsive performance.…”

Section: Interactionsmentioning

confidence: 99%

Special issue: bioinspired fluid-structure interaction

Jung

Godoy-Diana

2023

Bioinspir. Biomim.

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Fluid-structure interaction (FSI) studies the interaction between fluid and solid objects. It helps understand how fluid motion affects solid objects and vice versa. FSI research is important in engineering applications such as aerodynamics, hydrodynamics, and structural analysis. It has been used to design efficient systems such as ships, aircraft, and buildings. FSI in biological systems has gained interest in recent years for understanding how organisms interact with their fluidic environment. Our special issue features papers on various biological and bio-inspired FSI problems. Papers in this special issue cover topics ranging from flow physics to optimization and diagonistics. These papers offer new insights into natural systems and inspire the development of new technologies based on natural principles.

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