A general computational framework for fluid-structure interactions with application to underwater propulsion




Pereira Soares Gomes Pedro, Goncalo

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In SCUBA diving, the propulsive efficiency of a diver regulates, in part, his autonomy. An inefficient method of propulsion will increase the power output required and, therefore, the intake of oxygen and increase fatigue. Since the development of the SCUBA apparatus, fins have evolved based on the designer's intuition and knowledge of hydrodynamics. Some experimental work has been performed, but it is usually limited to studying the diver as whole and does not focus on the fin design. In this dissertation, a state-of-the-art fluid-structure interaction framework is developed and then used to study fin propulsion. This framework couples the structural dynamics of the fin with the fluid dynamics surrounding it using a modular framework. This way, mature state-of-the-art solvers can be used in each domain (structural and fluid). The flow field is solved using a computational fluid dynamics solver which resolves the Navier-Stokes equations. Coupled with these equations are a variety of turbulence models which can be used to resolve the turbulence in the flow. The CFD method is validated using a two-dimensional circular cylinder and a pitching and heaving airfoil, both immersed in a turbulent flow field. A commercial structural dynamics solver, is used to resolve the structural dynamics. The coupling of the two solvers is also described in detail. The basic design of a fin (a simple flat plate) is studied and modified in order to test the effect that altering key structural parameters has on the thrust, power and efficiency of the fin. The end result is a set of design recommendations which can be used to enhance the performance of a SCUBA fin. These recommendations are based on both quantitative and qualitative analysis of the performance characteristics of the fin.



Fluid-Structure, CFD, SCUBA, Propulsion