Study on thrust increase characteristics of separated undulating fins

The undulating fin, as a novel underwater propulsion method, has attracted increasing attention due to its excellent low-noise and high-maneuverability characteristics. However, this propulsion method still faces the challenge of generating relatively low thrust. This study proposes a separated undulating fin propulsion approach from a biomimetic perspective. Numerical simulations were employed to compare the thrust generated by the separated undulating fin and the traditional undulating fin under different phases and frequencies. The results demonstrate that this method can provide up to 13.5% greater thrust compared to traditional undulating fins. To validate the accuracy of the numerical simulation results, fluid experiments were designed and conducted for comparative verification. Through pressure analysis and vorticity analysis, the intrinsic mechanisms of thrust enhancement by the separated undulating fin were revealed. This work provides a new approach for generating greater thrust with undulating fin propulsion. •A new undulating fin which can increase thrust is proposed.•The thrust of separated undulating fins can be increased by up to 13.5%.•The influence of different factors on the thrust enhancement phenomenon is explored.•The mechanism of thrust enhancement is explored from the perspective of vortex.