MS, University of Cincinnati, 2006, Engineering : Mechanical Engineering

Hydrofoils are used in maritime applications; such as ships and submarines, for stabilization, maneuvering, etc. In many of these applications, the hydrofoil may experience dynamic motion; an example would be an active-fin ship stabilization system where the hydrofoil oscillates periodically at large angles of attack. Computational Fluid Dynamics (CFD) is used for simulating the flow over an oscillating hydrofoil used in such systems. The CFD simulations for oscillating-hydrofoil flow are used in analysis of performance of the active-fin ship stabilization system. A system model has been created in MATLAB for this purpose. A Proportional Integral Derivative (PID) control system has also been developed to control the fin motion. Simulation of the active-fin ship-stabilization system in MATLAB provides the typical motion experienced by a hydrofoil used in ship stabilization. This motion is fed back to a CFD solver to determine the effect of non-sinusoidal oscillation on Lift, Drag and Moment of the hydrofoil. The aerodynamics of the non-sinusoidally oscillating hydrofoil is analyzed so as to find an optimum pitching motion for the hydrofoil so as to produce higher lift forces and thus provide better performance. Another important aspect which affects the performance of an active-fin ship stabilization system is cavitation occurring in the flow over oscillating hydrofoils. Cavitation occurs because the pressure on the suction side of the hydrofoil falls below the vapor pressure of water. Numerical simulations using Reynolds-averaged Navier-Stokes equations are carried out to analyze the effect of cavitation on the dynamic stall of an oscillating hydrofoil. It was found that the flow physics changes considerably with cavitation. The dynamic stall vortex (DSV) was formed at an angle of attack much smaller than that for the non-cavitating case. The vortical structures were found to be distorted as compared to the non-cavitating case. Cavitation led to large oscillations i (open full item for complete abstract)

Committee: Dr. Urmila Ghia (Advisor) Subjects: