Review of Experimental Work in Biomimetic Foils

Abstract

Abstract-Significant progress has been made in understanding some of the basic mechanisms of force production and flow manipulation in oscillating foils for underwater use. Biomimetic observations, however, show that there is a lot more to be learned, since many of the functions and details of fish fins remain unexplored.This review focuses primarily on experimental studies on some of the, at least partially understood, mechanisms, which include 1) the formation of streets of vortices around and behind two-and three-dimensional propulsive oscillating foils; 2) the formation of vortical structures around and behind two-and three-dimensional foils used for maneuvering, hovering, or fast-starting; 3) the formation of leading-edge vortices in flapping foils, under steady flapping or transient conditions; 4) the interaction of foils with oncoming, externally generated vorticity; multiple foils, or foils operating near a body or wall.Index Terms-Biomimetics, fish swimming, flapping foil propulsion. I. OVERVIEW OF LITERATURE BIOMIMETIC studies and observations from fish and cetaceans have provided a wealth of information on the kinematics, i.e., how these animals employ their flapping tails and several fins to produce propulsive and maneuvering forces (see reviews in [123] The fluid mechanics and force mechanics of foils have been investigated with the goal of understanding the principles of this different paradigm of propulsion and maneuvering, so as to apply it to enhance existing technology. The tails of some of the fastest swimming animals closely resemble high aspect ratio foils. As a result, flapping foils have been studied extensively using theoretical and numerical techniques [72] II. BASIC PARAMETERS AND DEFINITIONSIn a foil with maximum chord length and maximum span , moving at steady speed , and at an angle of attack , the parameters of relevance are (a) the geometric shape (rectangular, delta-shaped, etc.); (b) the aspect ratio (AR), defined to be equal to the ratio of an average span over an average chord; (c) the angle of attack ; and (d) the Reynolds number , where is the kinematic viscosity of the fluid.

Numerical Study on Hydrodynamic Performance of Bionic Caudal Fin

“…Any new breakthrough in the mechanism will bring new inspiration to the developments of biomimetic propulsors. Therefore, to explore the mechanism, scholars are spending considerable efforts to reveal the essence of the problems with different research methods [3][4][5][6][7][8][9][10]. Among the methods, numerical simulation method has gained growing attention because of its advantages of low input, high efficiency and simple post-processing.…”

Numerical Modelling of Flexible Heaving Foils

“…Note that this value is based on the reference velocity U ref , as it enters equation (1). To obtain the Reynolds number based on the wing velocity, this value should be corrected by a factor proportional to the stroke frequency.…”

“…In the twodimensional approximation, shown in Fig. 1(b), this is equivalent to prescribing a heave motion y le (t) and a pitch motion α(t) (see, e.g., [1]). However, if the wing is flexible and clamped at the leading edge, the effective angle of incidence varies passively due to the action of inertial and aerodynamic forces (Fig.…”

Multimodal swimming control of a robotic fish with pectoral fins using a CPG network

“…It is also confirmed that the CPG-based swimming control exhibits better dynamic invariability in preserving rhythm than the conventional body wave method. Robotic fish, inspired by fish in nature, have received increasing attention in recent years because of potential aquatic-related applications such as exploration, surveillance, transportation, and mobile sensing [1][2][3][4][5][6][7]. Many scientists and engineers have carried out studies on robotic fish, focusing not only on the hydrodynamics mechanism and bio-inspired practice of fishlike swimming, but also on motion planning, control, and optimization of the fishlike robots [2].…”