Self-propulsion of a flapping flexible plate near the ground

Abstract

The self-propulsion of a three-dimensional flapping flexible plate near the ground is studied using an immersed boundary-lattice Boltzmann method for fluid flow and a finite-element method for plate motion. When the leading edge of the flexible plate is forced into a vertical oscillation near the ground, the entire plate moves freely due to the fluid-structure interaction. The mechanisms underlying the dynamics of the plate near the ground are elucidated. Based on the propulsive behaviors of the flapping plate, three distinct regimes due to the ground effect can be qualitatively identified. These regimes can be described briefly as the expensive, benefited, and uninfluenced propulsion regimes. The analysis of unsteady dynamics and plate deformation indicates that the ground effect becomes weaker for a more flexible plate. We have found that a suitable degree of flexibility can improve propulsion near the ground. The vortical structure around the plate and the pressure distribution on the plate are analyzed to understand propulsive behaviors. The results obtained in this study can provide some physical insights into the propulsive mechanisms of a flapping flexible plate near the ground.

Effect of trailing-edge shape on the self-propulsive performance of heaving flexible plates

“…where v is the velocity, p the pressure, ρ the density of the fluid, µ the dynamic viscosity and f the body force term. The structural equation is employed to describe the plate deformation and motion (Huang & Sung 2010;Hua, Zhu & Lu 2014;Tang et al 2016):…”

Hydrodynamics of a self-propelled flexible fin in perturbed flows

“…Some of the previous studies observed the increased power input when operating near the ground (Quinn et al 2014a;Dai et al 2016;Tang et al 2016;Park et al 2017). The body kinematics was one of the key parameters in determining the thrust and the power input (Park et al 2017).…”

“…In the numerical study performed by Ryu et al (2016), a tethered flexible fin with a transverse heaving motion produced an enhanced thrust near the ground. Several studies adopted a self-propelled system to study the ground effect, where the swimming speed and the body kinematics are dynamically coupled (Dai et al 2016;Tang et al 2016;Park et al 2017). Dai et al (2016) and Park et al (2017) modelled a twodimensional (2D) flexible fin swimming near the ground, and the swimming speed increased with the cost of increasing input power.…”

“…Dai et al (2016) and Park et al (2017) modelled a twodimensional (2D) flexible fin swimming near the ground, and the swimming speed increased with the cost of increasing input power. Tang et al (2016) defined the expensive, benefited, and uninfluenced regimes for a self-propelled flexible plate near the ground. The swimming speed increased, and a larger amount of input work was required for the locomotion in the expensive regime, while the efficiency increased with the reduced input work due to the decreased bending deformation of the plate in the benefited regime.…”

“…Motivated by many animals swimming near the ground, Sung Goon PARK* and Hyung Jin SUNG* *Department of Mechanical Engineering, KAIST 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea E-mail: hjsung@kaist.ac.kr Park and Sung, Mechanical Engineering Reviews, Vol.5, No.1 (2018) [DOI: 10.1299/mer. many researchers have performed experimental (Blevins and Lauder 2013;Quinn et al 2014aQuinn et al , 2014bFernandez-prats et al 2015;Bleishwitz et al 2016) and numerical (Dai et al 2016;Ryu et al 2016;Tang et al 2016;Park et al 2017) studies on the ground effect, and observed the hydrodynamic advantages such as increments of cruising speed, thrust and propulsive efficiency depending on the body motion of a swimmer. Fish can benefit from swimming in the wake of an inanimate structure as well as swimming near the ground.…”