Journal
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART M-JOURNAL OF ENGINEERING FOR THE MARITIME ENVIRONMENT
Volume 225, Issue M2, Pages 161-169Publisher
PROFESSIONAL ENGINEERING PUBLISHING LTD
DOI: 10.1177/1475090211398822
Keywords
air cavity; ventilation; drag reduction; potential flow theory; flow control
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Funding
- WSU
- NSF [1026264]
- Div Of Civil, Mechanical, & Manufact Inn
- Directorate For Engineering [1026264] Funding Source: National Science Foundation
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The application of air-ventilated cavities for marine vessels can result in substantial drag reduction. Experimental and modelling studies of air cavities formed under a model-scale hull are reported. Experiments were conducted with a simplified stepped hull on the water surface in a recirculating water channel. Stable cavities with different lengths and cavitation numbers were generated at fixed water flow velocity and model position. No air leakage from cavities was observed in a range of cavity lengths. The maximum length of a stable cavity with air leakage was identified. Significant enhancement of the maximum cavity length was achieved by placing an inclined plate under the cavity and supplying a large amount of air during a short period of time. This augmentation of the cavity presents an effective practical means for lengthening air-ventilated cavities and controlling cavity properties. Numerical studies simulating an air-cavity flow were conducted using a linearized potential flow method. Calculations show a qualitative agreement with trends of experimentally observed lengths of air cavities and confirm a possibility of increasing the cavity length by placing a vortex underneath the cavity. A quantitative agreement is obtained for maximum lengths of non-augmented cavities when non-linear and viscous effects are minimal.
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