Hydrodynamic analysis of an undulating body: Integrating the benefits of rectangular fin and NACA profile

In general, for an autonomous underwater vehicle (AUVs), its shape is one of an important parameter influencing its performance. AUVs can be propelled using conventional propellers or by undulating (flapping), its body like aquatic animals. Most of the existing AUVs that propels by undulating its body are multi-segmented and rectangular. However, research studies have often focussed on NACA hydrofoils, despite the prevalence of rectangular designs in AUVs. This paper aims to fill the gap in the current research by conducting a comparative study of the thrust force generation and efficiency of rectangular fin and hydrofoil. Besides, a merged body shape (MBS) has been proposed, combining the advantages of hydrofoil and fin. A comprehensive analysis has been made by comparing the performance of an undulating NACA 0012 foil, a rectangular fin with the proposed MBS at St = 0.2 – 1, for non-dimensional wavelengths (l*= 0.8 and 1.0) at Re = 1000. Increase in thrust forces are observed with increase in St and l*. The efficiency at l*=0.8 is higher than that at l*=1.0, indicating optimal wavelength for high efficiency. The MBS generates a mean thrust coefficient comparable to the hydrofoil, offering a balance of thrust and modular adaptability.