Structural Analysis and Optimization of a Propeller Under Separate Air and Water Operating Conditions Using One-Way Fluid–Structure Coupling

Abstract

A propeller intended for aerial–aquatic vehicles must maintain adequate propulsive performance and structural reliability in both air and water, where the fluid properties and load levels differ substantially. This study presents an engineering workflow combining blade element momentum theory (BEMT), computational fluid dynamics (CFD), and one-way fluid–structure coupling to evaluate a propeller under separate air and water operating conditions. Candidate geometries were first screened using a two-stage BEMT procedure. The selected baseline configuration was subsequently analyzed by CFD under three steady operating conditions: air start, water start, and water inflow. The resulting non-uniform surface pressures and centrifugal loads were transferred to a finite element model. The blade root transition was identified as the dominant stress concentration region under all conditions, and the water inflow case produced the most critical structural response, with a maximum von Mises stress of 129.8 MPa and a maximum deformation of 5.378 mm. After local blade root optimization, these values decreased to 87.0 MPa and 3.669 mm, respectively. The proposed workflow provides an efficient approach for preliminary structural assessment and local optimization of propellers operating separately in air and water. The transient air–water interface-crossing process and associated multiphase effects are beyond the scope of the present study.