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Mechanical Engineering MS Thesis Defense by Mr. Jeffrey Hanson

When: Monday, June 7, 2021
9:00 AM - 12:00 PM
Where: > See description for location
Description: Mechanical Engineering MS Thesis Defense by Mr. Jeffrey Hanson

June 7, 2021

9:00 a.m. - 12:00 p.m.

Zoom link:

Tethered Recharge of Autonomous Underwater Vehicles

The United States Navy (USN) makes extensive use of Autonomous Undersea Vehicles (AUVs) and has strongly supported continued advancements in their capabilities. However, mission duration and range remain strongly constrained by battery capacity. Options for extending duration include connecting to docking stations and modifying the vehicle to harvest wave and solar energy. These systems allow the AUV to recharge over the course of days allowing for extended operation but mission logistics can be complex, performance is dependent on ocean conditions, and vulnerability due to surface exposure is a concern. In this work an alternative approach for self-recharging of an AUV is examined. The approach borrows from a form of airborne wind-energy known as crosswind kite power whereby a vehicle is tethered to the ground and undergoes controlled glide through periodic trajectories at speeds much greater than the freestream. Power is generated by onboard turbines. In the present work this approach is applied to an AUV temporarily anchored to the seabed in a uniform ocean current. While undergoing controlled motion, flow over the vehicle turns the propeller in reverse and adds energy to the batteries. As the rate of this tethered recharge is strongly tied to the vehicle aerodynamic efficiency (L/D), wings are affixed to the AUV body. An iterative optimization method is developed to determine the planform and airfoil section of the wings that results in the maximum rate of recharge. This method is applied to the design of wings for the General Dynamics Mission Systems Sandshark micro AUV. The resulting optimized micro AUV undergoes tethered recharge in 9.1 hours in an ocean current of 0.2 ms-1. Additional scaling studies are conducted to examine the influence of ocean current speed and vehicle size on the rate of recharge. Reynolds effects are found to increase the functional dependence of recharge rate on flow speed beyond a nominal cubic law. Recharge power increases by 8.8 when the freestream is doubled. The influence of vehicle size on recharge power is also found to be affected by flow scaling and recharge rates were found to be 5.6% greater than those predicted by a nominal area rule. In all cases optimizing wings for specific size and freestream speed was found to be beneficial and increased recharge power by 12.5% and 26.2% respectively beyond that of a baseline vehicle. The results of this study demonstrate that tethered recharge is a viable means of extending mission duration of existing AUVs.

Dr. Geoffrey Cowles, Associate Professor, Department of Fisheries and Oceanography,
School for Marine Science and Technology, UMassD

-Dr. Amit Tandon, Professor of Mechanical Engineering, UMassD
-Dr. Scott Hassan, Naval Sea Systems Command Division, Newport, Rhode Island

Open to the public. All MNE students are encouraged to attend.

For more information, please contact Dr. Geoffrey Cowles (

Thank you,

Sue Cunha, Administrative Assistant
UMass Dartmouth Mechanical Engineering Department
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