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- Title
- Hydrodynamic Interactions of Pitching Hydrofoils in Close Formation.
- Creator
- Boltri, Michael A., Curet, Oscar M., Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
-
Hydrodynamics interaction is a factor in the performance of fish schooling or underwater vessels in close formation. In this work, we visualized the wake structure of pitching hydrofoils using an inclined soap film. We considered one-, two-, three- and nine-foil configurations with different spacing and actuation parameters: amplitude (A), frequency (f), phase difference (), and flow speed (U). The wake structures were recorded with a high-speed camera and analyzed to measure the vortex...
Show moreHydrodynamics interaction is a factor in the performance of fish schooling or underwater vessels in close formation. In this work, we visualized the wake structure of pitching hydrofoils using an inclined soap film. We considered one-, two-, three- and nine-foil configurations with different spacing and actuation parameters: amplitude (A), frequency (f), phase difference (), and flow speed (U). The wake structures were recorded with a high-speed camera and analyzed to measure the vortex angle created. The wake structure of two- and three-foil configurations were compared with the Strouhal number, St = fA/U, of a single foil. For the nine-foil configuration, the wake velocity and the standard deviation of the velocity were used to interpret the hydrodynamic interaction. It was found that both spacing and phase difference between foils are relevant in the hydrodynamic interaction. Qualitative observations are also made, and vortex street behavior characteristics are identified.
Show less - Date Issued
- 2020
- PURL
- http://purl.flvc.org/fau/fd/FA00013627
- Subject Headings
- Hydrodynamics, Hydrofoils
- Format
- Document (PDF)
- Title
- Flow Control Through Geometric Modifications to Improve Airfoil/Hydrofoil Performance.
- Creator
- Ni, Zao, Dhanak, Manhar, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Geometric modification as the most effective passive flow control method has recently received wide attention due to its enormous potential in enhancing performance characteristics of airfoils or hydrofoils without expensive manufacturing and maintenance cost. Two primary passive flow control modifications, known as leading-edge tubercles and internal slots and their applications in airfoils/hydrofoils have been investigated in this dissertation. For the hydrofoil, since free surface effects...
Show moreGeometric modification as the most effective passive flow control method has recently received wide attention due to its enormous potential in enhancing performance characteristics of airfoils or hydrofoils without expensive manufacturing and maintenance cost. Two primary passive flow control modifications, known as leading-edge tubercles and internal slots and their applications in airfoils/hydrofoils have been investigated in this dissertation. For the hydrofoil, since free surface effects cannot be neglected, the interaction between the hydrofoil-motion induced waves on the free surface and the hydrofoil has been studied as well. In the theoretical approach aspect, an empirically-based model based on an iteration scheme has been proposed for predicting the lift coefficients of twisted airfoils with leading-edge tubercles by using experimental data for untwisted airfoils. With both numerical and experimental investigations, this dissertation has discussed the application of a custom optimized-design internal slot on a NACA 634-021 airfoil blade to allow ventilation of flow through the slot from the pressure side to the suction side of the blade, in support of delaying flow separation, and stall. The combined effect of an internal slot in an airfoil and transverse leading-edge tubercles on its performance has been further studied both numerically and experimentally. Moreover, performance of a NACA 634-021 hydrofoil in motion under and in close proximity of a free surface for a large range of AoAs has been studied. Lift and drag coefficients of the hydrofoil at different submergence depths are investigated both numerically and experimentally. The results of the numerical study are in good agreement with the experimental results. The agreement confirms the new finding that for a submerged hydrofoil operating at high AoAs close to a free surface, the interaction between the hydrofoil-motion induced waves on the free surface and the hydrofoil results in mitigation of the flow separation characteristics on the suction side of the foil and delay in stall, and improvement in hydrofoil performance. A similarly submerged hydrofoil with a custom-designed internal slot has further been studied. The performance characteristics of the slotted hydrofoil in the presence of the free surface are investigated both numerically and experimentally.
Show less - Date Issued
- 2019
- PURL
- http://purl.flvc.org/fau/fd/FA00013248
- Subject Headings
- Hydrofoils, Aerofoils, Performance, Flow control
- Format
- Document (PDF)
- Title
- Experimental investigation of an oscillating hydrofoil propulsion system.
- Creator
- Viswanathan, Hariharan., Florida Atlantic University, Marshall, Jeffrey S., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
An experimental investigation of an oscillating hydrofoil propulsion system working behind a model of a small submersible was conducted. Tests were carried out both for a single foil and for systems of two foils. The tests with two foils considered various possible interactions between the foils. In order to understand the influence of trailing vortices of the foils on efficiency of the propulsion system, the two foils were tested for three different combinations of their relative wing spans....
Show moreAn experimental investigation of an oscillating hydrofoil propulsion system working behind a model of a small submersible was conducted. Tests were carried out both for a single foil and for systems of two foils. The tests with two foils considered various possible interactions between the foils. In order to understand the influence of trailing vortices of the foils on efficiency of the propulsion system, the two foils were tested for three different combinations of their relative wing spans. All of the above tests were carried out for two types of foil motion, one in which the pitch distribution was prescribed and the other in which the pitch depended on the motion characteristics.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14695
- Subject Headings
- Underwater propulsion, Submersibles, Hydrofoil boats
- Format
- Document (PDF)