Characteristics of flow over traveling wavy foils in a side-by-side arrangement

Abstract

Flow over traveling wavy foils in a side-by-side arrangement has been numerically investigated using the space-time finite element method to solve the two-dimensional incompressible Navier-Stokes equations. The midline of each foil undergoes lateral motion in the form of a streamwise traveling wave, which is similar to the backbone undulation of swimming fish. Based on the phase difference between the adjacent undulating foils, two typical cases, i.e., in-phase and anti-phase traveling wavy movements, are considered in the present study. The effects of lateral interference among the foils on the forces, power consumption, propeller efficiency, and flow structures are analyzed. It is revealed that the lateral interference is of benefit to saving the swimming power in the in-phase case and enhancing the forces in the anti-phase case. Some typical vortex structures, e.g., vortex-pair row, single vortex row, and in-phase and anti-phase synchronized vortex-street, are observed in the wake of the traveling wavy foils. The results obtained in this study provide physical insight into the understanding of hydrodynamics and flow structures for flow over the traveling wavy foils and swimming mechanisms relevant to fish schooling.

Flow-Mediated Interactions between Two Self-Propelled Flapping Filaments in Tandem Configuration

“…This is very different from the model used in some previous works [11,12,14], where the body was held fixed in an oncoming flow. Although a single actively flapping body in self-propulsion has been studied before [17][18][19][20][21], the multibody interactions under such condition have never been considered.…”

“…Although numerous studies on fish schools [7], bird flocks [8], and systems containing bacteria or active particles [9,10] can be found in the literature, the mechanism by which stable aggregations are formed remains unclear. The hydrodynamic characteristics of two coupled flapping (or traveling wavy) foils have been studied in some previous works [11][12][13]. For fish schools, Weihs predicted that a diamondlike configuration of the positions of individuals is energetically optimal [14].…”

Accelerated Motions of a Fish-Like Foil from Impulsive Starts to Terminal States

“…Although Eqs. (2a) and (2d) have already been used by Dong (13) and Akimoto (10) , respectively, the other two amplitude Eqs.…”

“…For example, in two-dimensions, Akimoto and Miyata (10) , Nakaoka et al (11) , and Sheu and Chen (12) have simulated flow fields induced by a deforming fish-like body placed in a uniform viscous flow using moving grid system such as arbitrary Lagrangian-Eulerian (ALE) approaches. Dong and Lu (13) have studied a side-by-side arrangement of fish and…”

Numeric Simulation on the Performance of an Undulating Fin in the Wake of a Periodic Oscillating Plate

“…Pan et al studied the oscillation behaviour of a flexible plate in the wake of a D-section cylinder and found that the incoming vortices make the plate oscillate with large amplitude at the beginning and then slant laterally [18]. Dong [19], Zhang [20] and Wu [21] et al adopted CFD to illustrate the interactions between fish while cruising in groups and revealed their abilities to control vortices. Wang [22] and Alben [23][24][25] numerically analysed the influence of phase relationships between the flexible plate and the vortex on its force generation.…”