Hydrodynamics and Thrust Efficiency of a Bio-Inspired Ray Model Under Prescribed Manta-like Pectoral-Fin Kinematics

Ray-like swimmers achieve propulsion through undulatory pectoral-fin motions, but the hydrodynamic consequences of these prescribed motions remain incompletely understood. We investigated a bio-inspired ray model that combines geometry reconstructed from a Javan cownose ray (Rhinoptera javanica) with pectoral-fin kinematics parameterized from published manta and mobuliform swimming studies. Pectoral-fin deformation was prescribed using analytical amplitude and phase functions, while fluid forces updated only streamwise rigid-body translation. The model yielded a maximum hydrodynamic Froude efficiency of 47.4% under the prescribed kinematics, and mean speed increased approximately linearly with flapping frequency over the retained 0.2–0.6 Hz range (R2 = 0.9890). The surface-attached vortex became less continuous as frequency increased, while pressure evolution indicated that thrust arose mainly during downstrokes. These results characterize the hydrodynamic response of this hybrid, bio-inspired ray model to the imposed manta-like waveform; they are not species-specific predictions for manta rays or R. javanica.