CFD-based hydrodynamics modeling of control fins with low aspect ratio for AUVs

Autonomous underwater vehicles (AUVs) are equipped with short span control fins owing to geometric constraints, resulting in difficulties in design and control of AUVs. The present study proposes a generalized approach for hydrodynamics modeling of AUV control fins based on validated computational fluid dynamics analyses. The lift generation, inflow velocity, and interaction with the vehicle body are systematically investigated and modeled with respect to fin span variation. The lift generation is modeled as the function of the fin aspect ratio and angle of attack, while conventional modeling considers only the fin aspect ratio. Inflow model is developed based on the lift generation model, to be consistent with nominal flow field measurements. The numerical test results confirm that the longer span fins reduce the fin-body interaction, which is found to degrade the vehicle’s turning ability. • Hydrodynamic characteristics of control fins of TL-AUVs with short span are investigated by validated CFD analysis. • The lift gradient of the short span fins is expressed as a function of the aspect ratio and angle of attack, while conventional ship rudder only considers the aspect ratio. • Fin deflection causes lateral force of the propulsor to reduce turning ability of the AUV. • Based on the findings, a generalized approach of hydrodynamics modeling of the control fins is suggested.