Experiments of Dynamic Forces of Two Oscillating Foils in Series

An underwater glider is propelled by a buoyancy engine to adjust the difference between buoyancy and weight, combining with the lift induced by the wing. In general, an underwater glider can ascend or descend obliquely, but has no capability to move horizontally. In view of the fact that an underwater glider is lack of horizontal mobility, a concept of booster with two oscillating foils in series is proposed in the present study to enhance the horizontal mobility without disturbing gliding. A test apparatus is established and a series of tank tests are carried out for clarifying its hydrodynamic characteristics.
The effects of amplitude, frequency and phase angle between the two oscillating foils to the hydrodynamic forces are investigated. It is found that the phase angle influences the propulsion force significantly, but the propulsion performance of the proposed design is not as good as expected. It needs to be modified for improving the performance. In addition, the CFD software “FLUENT” has been applied for comparison, and its validity as a tool to evaluate the design has also been confirmed. Therefore, the CFD tool “FLUENT” and the test apparatus established in the present study will be applied continuously in the future work to refine the design of a booster for underwater gliders.