Fin hydrodynamics in the design of swimming humanoid robots for hydraulic engineering and sanitary technology

The article analyzes the applicability of hydrodynamic scaling laws in the design of fins for swimming humanoid robots intended to perform demanding and high‑risk underwater tasks in hydraulic engineering and sanitary technology. It is demonstrated that fin length plays a crucial role in the efficiency of rapid locomotion, which may be applied to tasks such as delivering equipment to divers in caissons or transporting materials in underwater environments. The presented mathematical relationships provide a tool supporting the selection of optimal fin parameters in engineering practice. The proposed modeling algorithms can be applied not only in the context of humanoid robots but also to human swimming, thereby extending the range of potential applications. Calculations are presented for the propulsion generated by the fins of a humanoid robot of the Morphobot type. The robot’s design enables transformation from a humanoid to a sirenoid configuration by replacing the lower body segment with a tail module integrated with a monofin. It is shown that the use of a single monofin attached to both legs eliminates functional redundancy, whereas integration of the monofin with a dedicated tail module increases reliability. The highest level of functional redundancy is achieved when two separate fins are mounted on each leg in elongated boots reaching mid‑calf, equipped with fastening straps and buckles. This solution, referred to as hybrid mounting, ensures functional redundancy by allowing task continuation even in the event of the loss of one fin. Keywords: fin hydrodynamics, scaling laws, humanoid robots, underwater construction, hydraulic engineering, sanitary technology, bioinspired design, robot locomotion, underwater safety, aquatic robotics