Fluid–structure interaction study on the performance of flexible articulated caudal fin

The caudal fin is composed of two links which are connected by a hinge. One link is driven by pitching motion while the other one moves passively.

Five cases of link flexibility are investigated, namely, the rigid–rigid case, the medium flexible–medium flexible case, the flexible–flexible case, the rigid–flexible case and the flexible–rigid case. Their fluid field and structure deformations are analysed and hydrodynamic forces are compared. It is found that the rigid–rigid caudal fin produces larger thrust force than other cases with a low-pitching frequency, while the rigid–flexible case performs better with a higher frequency.