(NURP) Performance Optimization of an Underwater Vehicle Propelled by a Fluttering Tail
Abstract
ABSTRACT:An ideal underwater vehicle for naval applications would be energy efficient,maneuverable, and quiet. Vehicles employed by the Navy typically use propellers to provide thrust, which are efficient and can be made to run quietly, but cannotmaneuver a vehicle without additional control surfaces. By comparison, theswimming motions of carangiform fish are highly efficient and even large fish areable to make sharp turns at high speed. This maneuverability is a directconsequence of using the entire length of the tail as the control surface. Thekinematics, efficiency, and maneuverability of living fish are well-discussed in theliterature, but articulated mechanical devices designed with many degrees-of freedomto emulate the motion of swimming fish have generally not been able toreproduce the desired performance. An alternative method of producing fish-likemotion was developed by researchers at Michigan State University. In this method, a tail-like flexible element is designed to undergo flutter instability; the instability is produced by a fluid jet exhausting from the tip of the tail and the thrust is produced by the synergistic combination of the jet and the fluttering tail. This system is the ultimate expression of an underactuated system because it relies completely on the natural dynamics of the flexible tail. This mode of under-actuation greatly reduces the mechanical complexity of the system but requires more modeling effort for optimal performance.The objective of this research is to further develop and optimize the propulsionmechanism proposed by researchers at Michigan State University. Using exactsolutions, simulations, and experimental results, it has been shown that thetraveling waveforms produced by the tail s jet-driven flutter instability producesthrust exceeding the momentum flux from the jet exiting the tail. Modeling alsoindicated that the vehicle could be steered by carefully modulating the velocity ofthe jet. The preliminary work indicated paths of inquiry which will help to producemore capable vehicles using this type of propulsion. Improving the tail geometry so that an effective fluttering waveform is produced with less energy expended on the fluid jet will improve the propulsive efficiency; this optimization will require us to relax some of the assumptions made in the preliminary analysis, which was accurate for small movements of the tail. Improvements to the accuracy of the model at large tail amplitudes will also support further study of the control of a flutter-propelled vehicle, with the intention of eventually producing a full turn within one vehicle length. Apart from using a fluid-jet, active terminal bending moments will be explored as an alternative to generating fluttering oscillations of the tail. Improved test hardware will also be constructed to validate the modeling results.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2019
- Source ID
- N000141912535
Entities
People
- Ranjan Mukherjee
Organizations
- Michigan State University
- Office of Naval Research
- United States Navy