Multi-fidelity approach for thrust enhancement in bio-inspired nozzles for underwater vehicles using LES and experiments

Nozzles are commonly used in jet engines, fuel-injection systems, and underwater propulsion to control fluid flow and enhance thrust generation. Flexible nozzles have shown potential to enhance propulsion performance for small-scale underwater vehicles by increasing hydrodynamic impulse and jet entrainment. This study presents a multi-fidelity approach, which combines data from both low and high accuracy sources, integrating experimental data and computational modeling to characterize thrust and flow dynamics of bio-inspired flexible nozzles. Nozzles with varying stiffness and geometry were fabricated via 3D printing and tested on a fixed dynamometer. The dynamometer uses a current sensor and loadcell to measure power consumption and thrust simultaneously, with the propeller jet at fixed RPM. The propeller jet geometry was 3D scanned using PolyCam software and integrated into a high-fidelity CFD solver with a strongly coupled Fluid-Structure Interaction (FSI) model and Large Eddy Simulation (LES) to resolve unsteady vortex dynamics and jet structures. The integrated experimental and high-fidelity simulation approach enables direct comparison between simulations and experimental results, particularly in capturing thrust enhancement, jet flow statistics, and flow-induced nozzle deformation in flexible designs. The combined experimental and computational insights inform the design of efficient, bio-inspired propulsion systems for underwater vehicles.