Dissertation
Degradation and Enhancement of Drag-reducing Air Cavities Under Marine Vessels
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000005398
Handle:
https://hdl.handle.net/2376/124794
Abstract
Today’s economy relies heavily on the transportation of goods via waterway, which currently contributes around 3% of man-made greenhouse gas and is projected to grow. Air lubrication of ship hulls is a viable method for reducing friction drag and fuel consumption and has been implemented for a small number of water vessels, though confident design of ships with air assistance is limited by lack of experimental data and theoretical knowledge. Reliable design methodology requires additional experimentation under a variety of conditions, greater understanding of solid/liquid/gas interactions to build accurate physics simulations, and ultimately a way to provide dynamic control over multiphase flow characteristics. To expand the viability of air lubrication systems, this study has been undertaken to determine whether flow-altering devices such as hydrofoils, cavity-initiating wedges, and transom appendages can stabilize air cavities on ship hulls under various adverse operating conditions. Experimental studies included small-scale models tested in a recirculating water channel and larger models tested on open water. Results showed that increased air cavity size and greater potential drag savings are possible using these devices, while providing some insight into mechanisms limiting the air cavity size with unfavorable operating conditions. Computational fluid dynamics studies were conducted using commercial software Star-CCM+ to determine suitable modeling strategies to capture air cavity behavior observed experimentally. Using unsteady Reynolds-averaged turbulence models and the volume-of-fluid method to resolve air cavity characteristics, cavity behavior under the influence of hydrodynamic actuators at low Reynolds-number water speeds was captured with qualitative agreement using 2D simulations of ship models fixed in space. Additional studies using fixed 2D geometry at high Reynolds-number accurately predicted the minimum airflow required to sustain the air cavity, which was a problematic case for earlier computational research. Finally, 3D computational studies were conducted with two degrees-of-freedom and found that both cavity behavior and general hydrodyamics of the hull can be captured with reasonable accuracy using computationally inexpensive model settings.
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Details
- Title
- Degradation and Enhancement of Drag-reducing Air Cavities Under Marine Vessels
- Creators
- Jeffrey Michael Collins
- Contributors
- Konstantin I Matveev (Advisor)John Swensen (Committee Member)Lloyd Smith (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Mechanical and Materials Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 138
- Identifiers
- 99900592361701842
- Language
- English
- Resource Type
- Dissertation