DYNAMIC SIMULATIONS OF AN AIRPLANE-SHAPED UNDERWATER TOWED VEHICLE

This paper discusses the dynamic simulations of a Towfish equipped with three wings, two of which can be moved for a possible stability depth control. The models describing the 3D geometry of both vehicle and towing cable are implemented, their main parameters and the acting forces are evaluated and then simulated using a multibody dynamic software. Numerical values of the hydrodynamic forces and moments, obtained by numerical fluid dynamics analyses, are also added to the vehicle model in order to obtain a more accurate simulation of the open-loop behavior of the system. As shown in the Fig. 1, the airplane-shaped Towfish has three wings: a main fixed wing, a mobile stern wing and another mobile bow wing, called Canard wing. The vehicle length is 1.8 m, its height is 52.8 cm and its width is 2 m., measured as the wingspan of the main wing. The system is designed as a not buoyant object, while the airfoil shape of the wings is chosen according to the NACA code. The towing cable has a length of 500 meters, a section diameter of 30 mm and its linear weight in the seawater is 1.27 kg/m. Finally, the connection between the cable and the towfish is reproduced by a spherical joint. Numerical simulation results show a depth stability of the vehicle associate with a positive pitch angle. The used method can provide some appreciable results to create a stability control system.