Three-dimensional cfd analysis to study the thrust and efficiency of a biologically-inspired marine propulsor

M Lamas,C Rodríguez,P González,J Rodríguez

doi:10.2478/v10012-011-0002-2

Abstract

Aquatic animals, which are the result of many millions of years of evolutionary optimization, are very quick, efficient, robust, and versatile. Accordingly, biologically-inspired mechanisms which emulate the movement of animals have recently become very popular. For the efficient design of a propulsion system it is very important to analyze the fluid flow in detail. CFD (Computational Fluid Dynamics) has become a powerful technique to understand the phenomena because it gives extensive information about the fluid flow characteristics. In the present work, a propulsion system consisting of an undulating fin which emulates the fish swimming was built. In order to optimize the mechanism, several undulating configurations were studied using a 3D turbulent CFD model. The thrust, drag, efficiency and hydrodynamic characteristics were analyzed. Furthermore, it was shown that the efficiency and thrust depend strongly on the oscillation frequency, amplitude and wavelength. In order to validate this CFD model, the numerically obtained thrust was successfully compared with experimental results from the laboratory mechanism.

Highlights

Biomimetic is an emerging field which employs the principles of living organisms to derive man-made mechanisms which are capable of emulating the efficient movement of animals
A fish consumes much less energy to displace than a rigid body because the motion of the fish contributes to a reduced drag force and increased propulsive efficiency by reducing separation and suppressing turbulence (Shen et al, 2003)
Barret et al (1999) constructed a fish-like mechanism and studied it on a laboratory in order to compare the undulating fish movement with a rigid wall movement. They concluded that the power required to propel an actively swimming fish-like body is significantly smaller than the power needed to tow the body straight and rigid and they obtained drag reductions up to 70% for the undulating fish movement

Summary

Introduction

Biomimetic is an emerging field which employs the principles of living organisms to derive man-made mechanisms which are capable of emulating the efficient movement of animals. Recent works have shown that undulating fish movement is very efficient compared to rigid bodies (Barret et al, 1999, Liu and Kawachi, 1999, Triantafyllou, 1995) and there are several researchers interested in fish-like underwater and surface ships. Barret et al (1999) constructed a fish-like mechanism and studied it on a laboratory in order to compare the undulating fish movement with a rigid wall movement. Young-hua et al (2007) designed an environment-friendly propulsion system mimicking undulating fins and developed a two-dimensional CFD method to study the unsteady flow around the fin. They focused its study on studying the amplitude configuration. Clark and Smith (2007) built a flexible fin which replicates some features of the pectoral fin of a batoid fish

Methods

Results

Conclusion