Strouhal Number Measurement for Novel Biomimetic Folding Fins Using an Image Processing Method

Abstract

The aim of the paper is to present the parameters of new biomimetic folding fins measured using image processing. Tests were carried out for different types of folding biomimetic fins and compared to the most popular fins on the market. A noninvasive image processing method was used to estimate divers’ velocities in the vertical and horizontal directions and the frequency and the amplitude of the fin trailing edge, and as a result, the Strouhal number was calculated. These tests are a continuation of studies conducted in a water tunnel, where fin efficiency was measured as the ratio of generated thrust to electrical energy consumption, taking into account the mechanical efficiency of the leg manipulator as well as the water velocity. The Strouhal number helped us to analyse the parameters of the fin–diver–water system taking into account the properties of the fins, in particular the newly designed biomimetic folding fins.