Dual Wavemakers for Bi-Directional Irregular Seas and Ship Motions and Loads in Extreme Conditions
Abstract
**Approved for Public ReleaseWater waves are a distinguishing feature of the ocean environment that determine ship motions and loads, enable energy transfer between water, air, ice, and sediment, and are an enormous source for expeditionary energy needs. Water waves cause motions to ships that limit the ability to perform essential tasks and duties, cause safety hazards such a loss of ship incapsize, or damage due to structural loading or green-water on deck. Furthermore, water waves that dominate ship motions and loads are also a vast source of energy. For example the wave-power flux is 10-100 kW per meter of wave front, which is at least ten times higher than energy density of wind or solar sources. The theoretically available ocean wave energy resources along the US coastline alone are 5,100 TWH per year, exceeding the electricity generated from all resources. This high-density source of energy presents numerous opportunities to power expeditionary operations.It is proposed to purchase two hinged-flap-style wavemakers for installation in the towing tank at the Aaron Friedman Marine Hydrodynamics Laboratory at the University of Michigan. The new wavemakers will be able to generate bi-directional irregular waves of large scale. This is a first-of-its kind wavemaking facility in the United States and it will directly enhance a wide range of DOD projects related to surface and subsurface ship motions and loads, and it will be fundamental in driving the development of ocean-wave energy conversion for expeditionary operations and the reduction of carbon dependence of the military.The ocean environment is harsh and demanding, and engineering development for new ships and energy conversion is delayed by the inability to accurately recreate realistic ocean waves in a controlled experimental facility. Small wave basins are easy to use but can only test small models where complex interdependent multidisciplinary systems can not be faithfully recreated due to competing scaling laws. Thus access to large scale facilities will accelerate development and knowledge discovery. The new system will be able to generate shortcrested bi-directional seas with wave height of more than 1.0 m and largest wave period in the range of 3.0-5.0 s.The new wavemaking capability will enable two unique features. The first is the ability togenerate bi-dictional waves. This allows for the study of dynamics in the realistic scenario of one group of waves propagate in one direction, and a second wave type propagates in the opposite direction. This is typical of swell from one storm which is moving in a differentdirection from building seas in the direction of the wind. The second feature is the ability toactively damp waves. In all of the current systems the waves are damped with a passivebeach, and this permits energy accumulation and limits the length of run time for a givenexperiment. This new configuration will allow for long-time experiments that are needed tocollect statistics of extreme motions and loads.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 24, 2023
- Source ID
- N000142312689
Entities
People
- Kevin J. Maki
Organizations
- Board of Regents of the University of Michigan
- Office of Naval Research
- United States Navy