Mathematical Modeling and Simulation of a Hybrid Additive–Subtractive ROV with Experimental Validation for Reef Exploration

This work presents a mathematical and numerical framework for the design and analysis of a remotely operated vehicle (ROV) intended for shallow-water reef exploration. The vehicle consists of an open-frame structure with a sealed pressure housing and a four-thruster propulsion system that enables omnidirectional maneuverability and stable low-speed operation. The hydrodynamic behavior of the ROV is modeled using the incompressible Reynolds-averaged Navier–Stokes equations, which are solved numerically to obtain the velocity and pressure fields around the vehicle. Thruster-induced flow is represented through a Multiple Reference Frame (MRF) formulation, allowing thrust generation and momentum exchange to be resolved directly from the governing equations without prescribing artificial source terms. The propulsion model is supported by experimental bollard-pull characterization of T200 thrusters, from which quadratic thrust laws were identified. A quantitative validation against published experimental data shows deviations within 6–9% and a root-mean-square error (RMSE) of approximately 1.6 N, confirming the accuracy of the proposed thrust model. The CFD-predicted axial force (FZ≈−17.60N) was further shown to be consistent with the experimentally derived thrust law when evaluated at the corresponding equivalent operating condition. Structural response is evaluated through a one-way fluid–structure interaction (FSI) strategy, in which the hydrodynamic loads obtained from the CFD solution are transferred to a linear elastic structural model. The validity of the one-way coupling assumption is supported by explicit displacement-to-length ratios in the range δ/L∼ 10−5–10−3, confirming negligible geometric feedback on the flow field. The results show that the combined CFD–FSI formulation provides physically consistent predictions while remaining computationally efficient. The aluminum configuration exhibited a maximum von Mises stress of approximately 21.1 MPa, remaining safely within the elastic regime, whereas the ABS configuration reached a maximum displacement of 2.9 mm, indicating substantially higher structural compliance. Overall, the experimentally validated propulsion model, quantitatively supported CFD predictions, and asymptotically justified one-way FSI coupling constitute the main contributions of this study, providing a reproducible and physically consistent methodology for the analysis and optimization of reef-class ROVs.