Study on Structural and Hydrodynamics of Autonomous Underwater Gliders

Underwater gliders are autonomous underwater vehicles that use buoyancy to convert horizontal to vertical displacement to propel underwater. The most famous and common AUGs in the market are Slocum, Seaglider, Spray, and LiberdadeXray. All these gliders serve at different operating depth and payload. However, external forces and hydrodynamic forces are important to define the operational capacity of an AUG. Experimentally, it is expensive and difficult to determine the behaviour of structural and hydrodynamic forces. Therefore simulation is used to optimize the structural and hydrodynamics of the AUGs. There are two types of analysis proposed to compare both Slocum and Seaglider which are structural FEA and hydrodynamic CFD analysis. For structural FEA analysis, CATIA Dessault software is used meanwhile ANSYS FLUENT is used to analysis hydrodynamic performance of these AUGs. For the structural analysis, FEA modelling has been used to test the Von Mises stress and buckling of three types of materials on the AUGs hull body. On the other hand, hydrodynamic performance of the AUGs are tested to interpret the coefficient of lift, coefficient of drag and lift to drag ratio generated on Slocum and Seaglider at different angle of attacks (-15° − +15°). For this project, these findings are to be compared between the chosen gliders based on structural and hydrodynamic performance. From structural perspective, it is found that Seaglider has better hull body performance compared to Slocum because Seaglider is designed at thicker hull thickness and higher buckling resistance compare to Slocum. Based on hydrodynamic performance, Seaglider also has higher performance than Slocum because Seaglider produced less drag and higher lifted when simulated at different angles of attacks. This is because an AUG shape greatly influences its hydrodynamic performance. Seaglider has shape more closely to NACA airfoil design which performs to have less drag and higher lift